stratigraphy and of coal at achibo

ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITY

STRATIGRAPHY AND QUALITY ASSESSMENT

OF COAL AT ACHIBO

DEPARTMENT OF GEOLOGY

COLLEGE OF

i



OF COAL AT ACHIBO-SOMBO AREA, SOUTH

WESTERN ETHIOPIA

A MASTER’S THESIS

BY

DIRIBA YADATA AYANSA

TO


COLLEGE OF APPLIED SCIENCES

DECEMBER, 2020



SOMBO AREA, SOUTH

APPLIED SCIENCES



OF COAL AT ACHIBO

A Thesis Submitted as a Partial Fulfillment to the


DECii



OF COAL AT ACHIBO-SOMBO AREA, SOUTH

WESTERN ETHIOPIA

BY

DIRIBA YADATA AYANSA

A Thesis Submitted as a Partial Fulfillment to the Requirements for the Award of the

Degree of Master of Science in Geology

(Sedimentary Geology)

To



DECEMBER, 2020



SOMBO AREA, SOUTH

Requirements for the Award of the


I hereby declare that the thesis entitled “

Coal at Achibo–Sombo A

the guidance of my advisor

except where explicitly stated otherwise in the text, and that this work has not been

submitted, in whole or in part, for any other degree or professional qualification.parts

of this work has been submitted for publication.

i

Declaration

I hereby declare that the thesis entitled “Stratigraphy and Quality Asse

Sombo Area, South Western Ethiopia” was prepared by me, with

the guidance of my advisor Dr.Samuel Getnet. The work contained herein is my own



of this work has been submitted for publication.

Stratigraphy and Quality Assessment of

” was prepared by me, with

contained herein is my own



This is to certify that the thesis prepared by

“Stratigraphy and Quality Assessment of Coal at Achibo

Western Ethiopia” and submitted as a partial fulfillment for the award of the Degree

of Master of Science complies with the regulations of University and meets the

accepted standards with respect to originality, content and quality

1

Approval Page

This is to certify that the thesis prepared by Mr.Diriba Yadata Ayansa

“Stratigraphy and Quality Assessment of Coal at Achibo-Sombo Area, South

and submitted as a partial fulfillment for the award of the Degree


accepted standards with respect to originality, content and quality.

Mr.Diriba Yadata Ayansa entitled

Sombo Area, South

and submitted as a partial fulfillment for the award of the Degree


iii

ABSTRACT

Achibo-Sombo which is known for its extensive coal deposits is situated in Oromia

regional state, South-Western Ethiopian. The present study was focused to analyses

the coal bearing sedimentary rock, lithostratigraphy, and quality of coal seam deposit

in the Achibo-Sombo Area. The stratigraphy of the area was investigated by

integrating borehole data and separating the area section wise based on field survey.

The area is characterized by variable lithostratigraphic units: Basement complex,

Lower Basalt, Coal bearing sedimentary rock (i.e.., interbedded mudstone and

sandstone layers comprising plant fossils with laminated carbonaceous shale, shale,

oil shale, and coaly shale) and Upper Basalt to the latest. The presence of Sandstone,

Mudstone, Coal Beds and Plant fossils bear fluviatile deposits where as the

intercalated various shale layers envisage the lacustrine environment. For this study,

fifteen (15) representative samples were taken separately with respect to their seam

thickness. Accordingly, coal seam thickness from outcrop ranges (0.45 to 4.8m) and

(2.5 to 8.37m) from borehole data and the overall coal seam ranges from (0.45 to

8.37m). The quality of coal at Achibo Sombo was analyzed by Adiabatic Calorie

Metter, Gravimetric and Proximate techniques. The result showed that, coal quality

ranged between (2323.044 - 9378.684 Btu/lb) as were observed from Adiabatic

Calorie Metter, while sulfur content value ranged (<0.02 % to 1.90%) based on the

Gravimetric and Proximate analyses which revealed the moisture, volatile matter,

fixed carbon and ash content where results showed (5.38 to 30.27 %, 21.27 to

37.29%, 6.29 to 33.23%, and 0.25 to 67.05%) respectively. Based on the current

study, the Coal at Achibo Sombo is characterized by low to medium sulfur, low to

high ash, low fixed carbon and medium to high volatile matter contents. Moreover,

majority of the studied samples showed Lignite A ranks while few samples reflected

Lignite B and Sub-bituminous C ranks. On the other hand, the grades of analyzed

samples are categorized as Steel Grade-I and II and Washery Grade-I and II.Based on

the findings of this study, detail exploration and XRD analyses mainly in the North

East and Eastern part of the study area were recommended

Keywords: Proximate Analysis, Sulfur content, Coal grade, Coal rank,

Lithostratigraphy

iv

ACKNOWLEDGMENT

Before and above all of everything I am grateful when I thank the almighty God, who

helped me throughout my life and work.

I would like to give my sincere gratitude to ministry of education and Mizan Tepi

University for openhanded the prospect to study for my master’s degree. Next, my

special thanks go to Addis Ababa Science and Technology University, College of

Applied Sciences Department of Geology for their financial assistance as well as

necessary materials to bring the research to its conclusion.

I also appreciate all of geology academic staff for their guidance and encouragement

from the starting to the end of this research work. I would like to give my great

appreciation to my advisor and instructor Dr.Samuel Getnet for his unreserved and

constructive comment, valuable suggestion, encourage and tireless support. His

willingness to devote his time generously is very much appreciated. Again also, my

heartfelt thanks to my co-advisor Dr.Tesfaye Demissie and Dr.Daniel Meshesha

whose invite me as I work on this project as well as constructive comment and tireless

support. As well my instructor Prof. Nageshwar Dubey for his constructive

comment, encouragement and tireless support.

I want to express my deepest sincere thanks to the Ethiopian Geological Survey

laboratory team for facilitating things in order to reach the proximate, Calorific Value,

and sulfur analysis results on time. I am also greatly thankful to the Achibo-Sombo

village friendly people and administration officers for their permission to do the

fieldwork and support me throughout my stay in Achibo-Sombo.

I wish to thank my parents for giving me encouragement and unforgettable support

when I am in the project work. At the last but not least, Iam thankful to everyone I

didn’t mention but has a special contribution to the work directly and indirectly.

v

Table of Contents

Declaration ................................................................................................................. i

Approval Page ........................................................................................................... 1

ABSTRACT ............................................................................................................. iii

ACKNOWLEDGMENT .......................................................................................... iv

List of Figures .......................................................................................................... ix

List of Tables ............................................................................................................ xi

List of symbols and Abbreviations ........................................................................... xii

CHAPTER ONE........................................................................................................ 1

1. INTRODUCTION ................................................................................................. 1

1.1 Background ......................................................................................................... 1

1.2 Description of the Study Area .............................................................................. 2

1.2.1 Location and Accessibility ............................................................................ 2

1.2.2 Physiography and Drainage pattern of the Study Area ................................... 4

1.2.3 Climatic Condition and Vegetation coverage ................................................. 6

1.2.4 Population and Settlement ............................................................................. 8

1.3 Statement of the Problem ..................................................................................... 8

1.4 Objective of the Study ......................................................................................... 8

1.4.1 General Objective .......................................................................................... 8

1.4.2 Specific Objectives ........................................................................................ 9

1.5. Scope and Limitation of the Study ...................................................................... 9

CHAPTER TWO ..................................................................................................... 10

2. LITERATURE REVIEW .................................................................................... 10

vi

2.1 Introduction ....................................................................................................... 10

2. 2.Coalification ..................................................................................................... 10

2.3. Depositional Environments of Coal ................................................................... 13

2.4 .Classification of Coals ...................................................................................... 13

2.5. Coal Quality ..................................................................................................... 14

2. 6.Regional Geology of the Area ........................................................................... 14

2.6.1 Precambrian ................................................................................................ 17

2.6.2. Paleozoic and Mesozoic Sediments ............................................................ 18

2.6.3. Cenozoic Rocks .......................................................................................... 18

2.7. Regional Geological Structures ......................................................................... 18

2.8. Stratigraphy of Geba Basin ............................................................................... 19

2.8.1. Crystalline Basement .................................................................................. 19

2.8.2. Lower Basalt .............................................................................................. 20

2.8.3. Coal and Oil Shale Bearing Sediments ....................................................... 20

2.8.4. Upper Basalt ............................................................................................... 20

CHAPTER THREE ................................................................................................. 22

3. MATERIALS AND METHODS ......................................................................... 22

3.1. Materials ........................................................................................................... 22

3.2. Methods ............................................................................................................ 24

3.2.1 Data Acquisition .......................................................................................... 24

3.3. Data Analysis ................................................................................................... 25

3.3.1. Proximate Analysis Procedure .................................................................... 26

3.3.2. Calorific Value Analysis Procedure ............................................................ 26

vii

CHAPTER FOUR ................................................................................................... 28

4. RESULT.............................................................................................................. 28

4.1 Lithological succession ...................................................................................... 28

4.1.1. Fluvio-Lacustrine Sediments (Coal Bearing Unit Section) .......................... 28

4.1.1.1. Dawe Section .......................................................................................... 28

4.1.1.2 Debeso Section ......................................................................................... 29

4.1.1.3. Tekeshe Stream Section ........................................................................... 30

4.1.1.4. Sombo-Section ........................................................................................ 31

4.1.1.5. Achibo Quarry site section .......................................................................... 32

4.1.1.6. Hada Bekela Stream Section .................................................................... 34

4.1.1.7. Witate –Section ....................................................................................... 35

4.1.2. Volcanic Clastic Sediments ........................................................................ 35

4.1.3. Upper Basalt ............................................................................................... 35

4.2. The sub-surface Coal-bearing Lithological succession in the Study

Area ........................................................................................................................ 36

4.3. Litho Stratigraphic succession of Coal Bearing Strata ....................................... 38

4.3.1. Lithostratigraphic succession Correlation ................................................... 48

4.4. Coal Quality Analysis ....................................................................................... 51

4.4.1 Moisture Content ......................................................................................... 51

4.4.2. Volatile Matter ........................................................................................... 53

4.4.3. Fixed Carbon .............................................................................................. 54

4.4.4 Ash Content ................................................................................................ 55

4.4.5. Sulfur Distribution ...................................................................................... 58

viii

4.4.6 Calorific Value ............................................................................................ 62

CHAPTER FIVE ................................................................................................. 65

5. DISCUSSION .................................................................................................. 65

5.1 Depositional Environment ................................................................................. 65

5.1.1. Fluvial Deposits ......................................................................................... 65

5.1.2. Lacustrine Deposits .................................................................................... 67

5.2. Quality Interpretation of Coal ........................................................................... 67

5.2.1. Grade ......................................................................................................... 68

5.2.2. Rank ........................................................................................................... 70

5.3. Comparison within Yayu coal deposits ............................................................. 74

5.4. Comparison with the Corresponding Coal deposit in Ethiopia ........................... 77

5.5. Economic significance of the Achibo-Sombo coal ............................................ 82

CHAPTER SIX ....................................................................................................... 85

6. CONCLUSION AND RECOMENDATION ....................................................... 85

6.1 .Conclusion ........................................................................................................ 85

6.2. Recommendation .............................................................................................. 86

REFERENCES ........................................................................................................ 87

Appendix I .............................................................................................................. 94

Appendix II ............................................................................................................. 97

ix

List of Figures

Figure 1 . Location Map of the study Area ............................................................................ 3

Figure 2.Accessibility of study Area ...................................................................................... 4

Figure 3..Physiography of study Area .................................................................................... 5

Figure 4.Drainage pattern of study area ................................................................................. 6

Figure 5.Field photo shows vegetation coverage and coal seam ............................................. 7

Figure 6.Coalification of coal (Falcon, 20013) .................................................................... 10

Figure 7.Type, Grade and Rank of Coal (Falcon, 2013) ....................................................... 12

Figure 8 .Regional Geological map of South Western Ethiopia (After Mengesha , 1996 ) ... 16

Figure 9.Lithostratigraphic column of Geba Basin (After Kibre,2000) ................................. 21

Figure 10.Methodology Flow charts .................................................................................... 24

Figure 11.Figure showing sample points taken from the studied area ................................... 25

Figure 12..Field photo shows very thick Coal bed at Dawe section ...................................... 29

Figure 13..Field photo taken from Debeso section ............................................................... 30

Figure 14. Field photo taken from Tekeshe section show laminated Oil Shale ..................... 31

Figure 15.A) Sombo section Eastern and B) Western Coal deposit field photos ................... 32

Figure 16. Field photo taken from Achibo Quarry site ......................................................... 33

Figure 17.Field photo taken from Hada Bekela section. A) From southern of the stream. B)

From Northern of the stream .................................................................................... 34

Figure 18.A) Geological Map and B) Cross-sectional Map of the study area ....................... 37

Figure 19.. Lithostratigraphic column of Dawe section ........................................................ 39

Figure 20.Lithostratigraphic column of Debeso section ....................................................... 40

Figure 21.Lithostratigraphic column of Tekeshe section ...................................................... 41

Figure 22.Lithostratigraphic column of Sombo section ........................................................ 42

Figure 23.Lithostratigraphic column of Achibo Quarry site Section .................................... 43

x

Figure 24.Lithostratigraphic column of Hada Bekela section ............................................... 44

Figure 25.Lithostratigraphic column of Witate Section ........................................................ 45

Figure 26.Detail Lithostratigraphic column of (BH-3,BH-4,and BH-5) .............................. 46

Figure 27. Detail Lithostratigraphy of (BH-7, BH-10, and BH-18) ...................................... 47

Figure 28.Lithostratigraphic column correlation of each section of study area ..................... 49

Figure 29.Lithostratigraphic column Correlation of Borehole study area ............................. 50

Figure 30. Lithostratigraphic column Correlation of study area within the Basin ................. 51

Figure 31.Graphic representation of moisture content by line charts .................................... 53

Figure 32.Fixed Carbon and Ash content comparison trend of Achibo-Sombo Coal ............ 56

Figure 33.Graphic representation of proximate analysis by line chart .................................. 57

Figure 34.Graphic representation of proximate analysis by column chart ............................ 58

Figure 35.Graphic representation of sulfur increment in Achibo-Sombo by column chart .... 61

Figure 36.Graphic representation of sulfur distribution by line chart.................................... 61

Figure 37.Graphic representation of calorific value increment by column chart ................... 63

Figure 38.Graphic representation comparison of volatile matter versus fixed carbon ........... 64

Figure 39. Graphic representation of ash versus moisture content by line chart .................... 64

Figure 40.Rank and Grade correlation of lithostratigraphic column of each stream section. . 74

Figure 41.Graphic Representation of proximate value comparison trend of Geba Basin Coal

deposits. .................................................................................................................. 76

Figure 42.Calorific value increment comparison trend of Geba Basin coal deposit .............. 77

Figure 43.Graphic representation of sulfur value increment comparison trend of the Geba

Basin coal deposit. ................................................................................................... 77

Figure 44.Ash, Fixed carbon, and Sulfur comparison trend of Ethiopian coals ..................... 80

Figure 45.Calorific value comparison trend of Ethiopia coals increments by column charts. 81

Figure 46.Sulfur value comparison trend of Ethiopian coals increments by line chart .......... 81

xi

List of Tables

Table 1.Location of Coal sample selected for analysis from out crop ................................... 23

Table 2.Location of Core Coal sample selected for analysis from bore hole......................... 23

Table 3.The sample analyzed result of moisture, volatile matter, fixed carbon and ash

contents ................................................................................................................... 57

Table 4.Sulfur (%) and Calorific value (Btu/lb) analysis result ............................................ 60

Table 5.Coal Grade ............................................................................................................. 69

Table 6.Rank classification based on ASTM (D388-1999) .................................................. 73

Table 7.Proximate, Calorific value ,Sulfur analysis results from GSE and Selected from the

present study............................................................................................................ 76

Table 8.Laboratory analysis of Ethiopian Coal deposits comparison. ................................... 79

xii

List of symbols and Abbreviations

ASTM = American Society for Testing and Materials

COFCOP = Coal-Phosphate Fertilizer Complex Project

CV = Calorific Value

DEM = Digital Elevation Model

D.m.m.f.basis = dry mineral matter free basis

FC = Fixed Carbon

GCF = Gross Calorific Value

GIS = Geographic Information System

GPS = Global Positioning System

GSE = Geological Survey of Ethiopia

ICCP = International Commission for Coal Petrology

ISO = International Organization for Standardization

M.m. m.f.b = moist mineral matter free basis

UTM = Universal Transverse Mercator

VM = Volatile Matter

1

CHAPTER ONE

1. INTRODUCTION

1.1 Background

Coal is the end product of the progressive burial of plant remains in oxygen-starved

condition. It is a readily combustible rock containing more than 50 percent organic

matter (carbon) by weight, and 70 percent carbonaceous material by volume including

inherent moisture, which was formed from the compaction and alteration of plant

remains, Schopf (1966); Jackson (1997); Alpern and Desousa (2002). It has been a

support for the economy in the world, but there are still over a billion people in the

world who live inadequate electricity, which is crucial for basic needs.

Coal is at a halt an important energy source and can replace conventional fuel sources

like petroleum and natural gas to meet the current rise in energy demand (Wolela,

2008). It plays an important role in the security of supply in developed countries and

is a key enabler for economic growth and development in developing countries,

(World Energy Resources, 2016). The world’s coal resources are derived mostly from

sedimentary rocks; exploration for such resources demands a detailed understanding

of Stratigraphy relationship with resources, which is the more important for energy

explorations.

According to Omar (1994), Ethiopia is the lowest per capital energy utilization of

organic energy, spends a large share of its total foreign earnings on imported fuels.

Before a coal mine is allowed to initiate operations, thorough studies must be carried

out to identify all the potential risks to the surrounding environment and to minimize

any negative impacts. As a result, predicting coal quality is an important charge and

depends on the knowledge of its physical and chemical constitution (Verma et al.,

2010).

2

The study of lithostiratigraphy and quality of coal assessment help to understand vital

energy exploration. Since there are variable economic uses for the production of coal:

chemical fertilizers, power generation (electric power), domestic fuel (source of

energy for household), fuel in the production of lime and bricks, ceramic plant

processing, cement manufacture, fuel for thermal plants for steel mills, oil and gas

generation, etc; Coal have been consumed in large quantities.

Coal quality is an important aspect of the assessment program in that it provides a

synthesis and analysis of important data that will influence the future utilization of

this valuable resource.

The Achibo-Sombo area is located in the South-Western flank of the South-Eastern

Ethiopian plateau which is known for its considerable coal deposits. The area is

characterized by variable lithostratigraphic units: Basement complex, Lower Basalt,

Coal bearing sedimentary rock, and Upper Basalt from oldest to youngest

respectively. Previous exploration work and research activities were focused mainly

on the quantity of coal in the place. However, this study intended at detail coal

bearing sedimentary rock lithostratigraphy and quality of coal seam deposit in the

Achibo-Sombo area based on integrated from outcrop and borehole data. The Achibo-

Sombo area coal deposit is lacks detail Lithostratigraphical correlation with other coal

deposits in the basin and other equivalent stratigraphic successions which will enables

us to understand the coal quantity and quality. The Lithostratigraphic correlation is

the organization of strata based on physical lithological characteristics based on strata

type, color, grain size, mineral composition, and texture. Therefore, with the use of

Stratigraphy research methods to study coal quality feature is the power full for

analysis of significant data for this worth resource.

1.2 Description of the Study Area

1.2.1 Location and Accessibility

The Achibo-Sombo area is a considerable coal deposit; it is situated in the South-western

Ethiopian located at a distance of 560 km southwest of the capital city, Addis Ababa. It is

bordered to the west by Gambella Regional State, to the east by the East Wollega and Jimma

zones, to the north by West and East Wollega, and to the South by the Southern Nations,

Nationalities, and Peoples' Region.

The study area mainly Achibo

far to the Eastern side) and Yayu (26 Km far to the Western side).It is bounded the

geographic coordinates of 8°21'20''

two routes from Addis Ababa along the Jima

weather asphalt high way and gravel road that joins the capital Addis Ababa with

Gambella. This road passes through the towns of Jima, Agaro, Bedelle, and Metu. The

other route that leads to the study area from Addis Ababa 500

Bedelle- Gambella road asp

Figure 1 . Location Map of the study Area

3

The study area mainly Achibo-Sombo, was found between the local towns of Chora (20 Km

ern side) and Yayu (26 Km far to the Western side).It is bounded the

geographic coordinates of 8°21'20''-8°24' 00'' N and 35°56'0''-36° 1'20''E

two routes from Addis Ababa along the Jima –Bedelle which is accessible by all

alt high way and gravel road that joins the capital Addis Ababa with


other route that leads to the study area from Addis Ababa 500 Km is along Nekemte

Gambella road asphalt road (Figure 2).

Location Map of the study Area

Sombo, was found between the local towns of Chora (20 Km

ern side) and Yayu (26 Km far to the Western side).It is bounded the

36° 1'20''E ( Figure 1 ) . It is

Bedelle which is accessible by all-

alt high way and gravel road that joins the capital Addis Ababa with


Km is along Nekemte -

4

Figure 2.Accessibility of study Area

1.2.2 Physiography and Drainage pattern of the Study Area

The topography of the study area contains undulating mountainous terrain, rising and

falling plateaus, valleys, and it is characterized by gentle slopes. The elevation

difference between the highest and the lowest point is nearly 600 meters, the highest

elevation being 2000m and the lowest 1400m above sea level. The elevation

difference between the maximum and minimum shows the ruggedness of the area

(Figure 3). Deep river valleys, dissected by several small streams and one major river,

called Geba River. It is bounded on both sides by ridges that trend almost East-West.

It is the main river system in the study area and it has many tributaries. These

tributaries flow from North East to South West and from South East to North West

directions. All the perennial and intermittent streams along with the Geba River drain

to the Birbir River. The drainage pattern is mainly dendritic type (Figure 4).

5

Figure 3..Physiography of study Area

Figure 4.Drainage pattern of study area

1.2.3 Climatic Condition and Vegetation coverage

Ethiopia has four seasons: the dry season (December to February), the small

season (March to May), the main rainy season (June to August), and the transition

season (September-December).The rainfall pattern is unimodal with a mean annual

rainfall ranging between 1243 and 3445 mm. November to February is a relatively dry

season with rare occurrences of rain, followed by the hottest period from February

through to the end of April.

The period between May and October is the wettest season of the year. Heavy rain

occurs between July and August with extended cold weather until mi

a diverse mix of climatic conditions is said to be the most important factor for the

availability of a huge wealth of biologically diverse species. The diverse vegetation

cover and tree species present within the biosphere reserve play vita

social, economic, and cultural aspects of the local community

6

Drainage pattern of study area

1.2.3 Climatic Condition and Vegetation coverage

Ethiopia has four seasons: the dry season (December to February), the small


December).The rainfall pattern is unimodal with a mean annual


on with rare occurrences of rain, followed by the hottest period from February

through to the end of April.


occurs between July and August with extended cold weather until mi



cover and tree species present within the biosphere reserve play vita

social, economic, and cultural aspects of the local community ( Figure 5)

Ethiopia has four seasons: the dry season (December to February), the small rainy


December).The rainfall pattern is unimodal with a mean annual


on with rare occurrences of rain, followed by the hottest period from February


occurs between July and August with extended cold weather until mid-October. Such



cover and tree species present within the biosphere reserve play vital roles in the

( Figure 5) .

Some trees are used for food and others that serve as traditional medicines. Similarly,

there are tree species used as main sources of wood and timber for the local people

residing in the district.

and Polyscias fulva (Karasho)

beehives because they have a pleasant odour that attracts bees and are easily workable

and light-weighted. Generally, the area is scarcely vegetated on the slope of the

ridges, and covers by dense high land forests along the Geba river basin. Most parts of

the target area farmlands. Cash crops, such as

for the farmers.

Figure 5.Field photo

7



residing in the district. Cordia Africana (Waddessa), Afrocarpus campus (Birbirsa

Polyscias fulva (Karasho) are essential trees, useful in making traditional


weighted. Generally, the area is scarcely vegetated on the slope of the

and covers by dense high land forests along the Geba river basin. Most parts of

the target area farmlands. Cash crops, such as coffee are the major source of income

shows vegetation coverage and coal seam



Afrocarpus campus (Birbirsa),

are essential trees, useful in making traditional


weighted. Generally, the area is scarcely vegetated on the slope of the

and covers by dense high land forests along the Geba river basin. Most parts of

are the major source of income

8

1.2.4 Population and Settlement

The 2007 population census of Ethiopia conducted by its Central Statistics Agency

shows that more than 1.2 million people live in the Illu Abba Bora zone have a total

population of 132 177,26 with almost equal proportions of men and women (CSA,

2007). It is estimated that the majority of these inhabitants (90.8% or 120 147) are

settled in the rural parts of the districts adjoining the dense coffee forest. According to

the 2005 countrywide census report, the average population density of the Yayu

district is 189.6 people/ km2, a figure much greater than the zonal average of 72,3

people/km2 (CSA and ORC Marco, 2006).

1.3 Statement of the Problem

Achibo-Sombo is one of the Yayu basins which are characterized by varieties of

Stratigraphic units, lithologies, and depositional environment. Stratigraphy is

persuasive for analyzing the depositional environment, vertical and spatial lithological

variation, and coal bed thickness. Coal quality issues related to coal combustion are

focusing on the release of particulate matter like sulfur, ash, volatile matter, and

moisture contents.

From the understanding of relevant published and unpublished reviewed paper

regarding Lithostratigraphic, coal quality, Structural, and tectonic setting of the area

related to depositional environment, there was a variable litho tectonic domain and

widely distributed coal deposited at Achibo –Sombo area. However, there was a

poorly documented stratigraphic study related to coal thickness and sulfur

identification related to coal seam, coal quality, grade and rank of the coal is not

reported in the sectional wise. Therefore, detailed study of stratigraphic logs,

correlation, depositional environment, and quality assessments to know the quality of

the coal deposits in the Achibo-Sombo area was studied in this paper.

1.4 Objective of the Study

1.4.1 General Objective

The main objective of this research is to constructing lithostratigraphic succession of

coal bearing strata and quality assessment of coal deposits at the Achibo-Sombo area

Southwestern Ethiopia.

9

1.4.2 Specific Objectives

To produce Geological Map of the Study area at Scale of 1:10,000.

To log coal-bearing strata.

To identify coal, grade, and rank of Achibo-Sombo coal deposits.

To evaluate sulfur distribution.

To correlate the Lithological units of the study area.

1.5. Scope and Limitation of the Study

In the present study, several coal samples and Lithostratigraphic unit of Coal bearing

strata were encountered following the coal quality. Todetermine the Lithostratigraphic

logs and quality of coal, critical stratigraphic section was s elected and coal samples

were analyzed using proximate, adiabatic calorie metter and gravimetric method.

However due to constrain of time, resources and financial limitations the analyses

were applied only to selected Lithostratigraphic logs , proximate, calorie metter and

gravimetric method which the fundamental for coal exploration and coal quality

determination. Therefore, during the present study only seven (7) out crop

Lithostratigraphic sections unit log, six (6) Lithostratigraphic unit log from bore hole

data, four (4) core coal samples, and eleven (11) outcrop coal samples were selected

and studied. In case of ultimate analysis method, some coal sample were gave unusual

result.

10

CHAPTER TWO

2. LITERATURE REVIEW

2.1 Introduction

Larry Thomas, (2013) reported that, Coals are the result of the accumulation of

vegetable debris in a specialized environment of deposition. Such accumulations have

been affected by synsedimentary and post-sedimentary influences to produce coals of

differing rank and differing degrees of structural complexity, the two being closely

interlinked. Coal is one of the very important energy sources for many countries that

are converted to heat and electrical power by different technologies.

Coal is currently a major energy source worldwide, especially among many

developing countries, and will continue to be so for many years (Miller, 2005). Hatch

and Swanson (1977) state that four general reasons why coal quality data are

necessary for the proper assessment and utilization of coal: the evaluation of

environmental impacts of mining of coal, the evaluation of the best and most effective

technological use of coal (combustion, liquefaction, gasification, etc.), determination

of the economic aspects of extracting elements from the coal, and development of

geologic and geochemical models to help interpret and predict coal quality and relate

these factors to the stratigraphic and sedimentological framework.

2. 2.Coalification

Coalification of coal is the transformation of peat through lignite, sub-bituminous,

bituminous, and semi-anthracite to anthracite and meta-anthracite coal.

Figure 6.Coalification of coal (Falcon, 20013)

11

It is the process of chemical and physical change by biochemical interferences,

temperature, pressure, and time imposed on the organic components that survived the

peat formation until it becomes organic rock (Tissot and Welte, 1984; Miller, 2005).

The change includes decaying of the vegetation, deposition, and burying by

sedimentation, compaction, and transformation from plant material to solid rock. The

degree of transformation or coalification is termed the coal rank, and the early

identification of the rank of the coal deposit being investigated will determine the

future potential and interest in the deposit. A detailed account of coalification and its

physical and chemical processes is given by (Taylor et al, 1998), who describe the

major stages of coalification from peat to meta-anthracite. During coalification, the

three maceral groups become enriched in carbon and each maceral group (i.e. exinite,

inertinite, and huminite (vitrinite)) follows a distinct coalification path van Krevelen

(1961). The optical properties of vitrinite have enabled it to be used as an indicator of

rank. The properties of given coal can be related to three independent geological

parameters, each of which is determined by some aspect of the coal’s origin. As

discussed more fully by authors such as Ward (1984), Diessel (1992), Taylor et al.

(1998) these parameters are briefly defined as follows:

Coal rank reflects the degree of metamorphism (or coalification) to which the original

mass of plant debris (peat) has been subjected during its burial history. Coal type

reflects the nature of the plant debris from which the original peat was derived,

including the mixture of plant components (wood, leaves, algae, etc.) involved and the

degree of degradation to which they were exposed before burial. The grade of coal

reflects the extent to which the accumulation of plant debris has been kept free of

contamination by inorganic material (mineral matter), including the periods before

burial (i.e., during peat accumulation), after burial, and during the rank advance.

The heating value, calorific value, or specific energy: This indicates the amount of

heat liberated per unit of mass of combusted coal and is of fundamental importance in

setting the price of particular coals for combustion applications.

12

Although generally regarded as a rank-related parameter, the calorific mineral

composition.

Although vitrinite reflectance is widely used as a measure of coal rank, it is not

always a truly independent rank indicator. Some vitrinite may have anomalously low

reflectance (such as the original depositional environment), a phenomenon known as

reflectance suppression (Barker, 1991), which may give misleading results if other

indicators are not taken into account. Despite the advantages and simplicity of

vitrinite reflectance, it is very difficult to find an indicator of coal rank that is totally

independent of the organic and inorganic

Composition of other influencing factors such as depositional environments of the

original peat deposit. Coalification affects both the organic matter and the mineral

matter in coal. Coalification proceeds, organic matter, which is relatively rich in

water, oxygen, and hydrogen, gradually loses those constituents and becomes

relatively enriched in fixed carbon.

Figure 7.Type, Grade and Rank of Coal (Falcon, 2013)

13

2.3. Depositional Environments of Coal

The study of coal facies is best accompanied by a facies study of the inter seam

sediments surrounding the coal layers (Mc cabe1984,Diesel 1992). A careful study of

both coal facies and clastic sediments may produce more precise interpretations of the

coal depositional environments. Coal, as well as the inter seam rock, is a sedimentary

rock with the only difference being in the source material which, in the case of coal,

mostly consists of organic material; the process of sedimentation requires that the

organic matter has to be preserved. An understanding of inter seam rocks also

influences coal quality. The coal and inter seam rocks do not necessarily have the

same environment of deposition even if they are stratigraphically adjacent to one

another.

The various deposits of the same facies area and similarly, rocks of different facies

areas, were formed beside each other in space, but in a crustal profile we see them

lying on top of each other it is a basic statement of far-reaching significance that only

those sand facies area can be superimposed, primarily that can be observed beside

each other at present (Selley, 2000). This principle is termed Walter’s law, and may

be succinctly stated as “a conformable vertical sequence of facies was generated by a

lateral sequence of environments” This principle is a vital one in environmental

analysis. One of the ways of identifying the environments of facies is by analyzing the

environments of facies above and below to come up with the most logical sequence of

events (Selley, 2000). Much of the field recording of sedimentary rocks is aimed at

classifying the strata being investigated into recurrent units and attempting to detect

order in the vertical and lateral arrangement of those units. The term applied to those

units is facies that are defined on a combination of lithological, structural, and organic

aspects in the field (Tucker, 1988).

2.4 .Classification of Coals

According to Thomas (2013) Coals have usually been classified based on the coal’s

chemical properties concerning their industrial usage. Several classifications are in

common usage, which classifies both humic and brown coals, and refers to particular

parameters; these range from the percentage of fixed carbon and volatile matter (on a

dry mineral matter free basis), calorific value (on a moist mineral matter free basis).

14

As the ASTM (American Society for Testing and Materials) classification (D 388-

1999) is used on a worldwide basis this is based on two coal properties, the fixed

carbon values and the calorific values (on d.m.m.f.basis). The higher rank coals are

classified according to fixed carbon on a dry basis, the lower rank coals are classified

according to gross calorific value on the moist basis. Such coals classification is

mostly non-banded varieties containing only a small proportion of vitrinite and

consists mainly of atrial materials.

2.5. Coal Quality

The physical and chemical properties in turn determine the overall quality of the coal

and its suitability for specific purposes. The basic chemical parameters of coal are

determined by proximate analysis (moisture, ash, volatile matter, and fixed carbon

percentages) and ultimate analysis (carbon, hydrogen, nitrogen, sulfur, and oxygen

contents). The quality of coal is measured by the made-up of the original maceral and

mineral matter content of the coal, with the degree of coalification (rank). For this to

be understood in analytical terms, set procedures for determining chemical and

physical properties of coals have been required ( Karr, 1978).

The possession of the coal is the most commonly determined properties of coal is

important, in particular those which are harmful to the coal. Such coal analyses are

essential in the evaluation of a coal deposit, which is to be aware of which seams or

parts of seams will be unacceptable when mining commences, or conversely, those

seams or parts of seams (Thomas, 2013).

According to Zhu (2014), Coal quality is determined by analyses of proximate or an

ultimate analysis. Proximate analysis is a broad analysis that determines the amounts

of moisture, volatile matter, fixed carbon, and ash. This is the most fundamental of all

coal analyses and is of great importance in the practical use of coal.

2. 6.Regional Geology of the Area

The geology of Ethiopia is comprised of three major geological terranes, categorized:

the Proterozoic crystalline basement, Late-Paleozoic to Mesozoic marine and

continental sedimentary rocks, and Cenozoic volcanic rocks.

15

Gashaw Beza and Kibre, (1996) reported that, the geological setting of southwestern

Ethiopia is included the Precambrian crystalline basement affected by the Pan African

Orogeny, overlain by Tertiary volcanics. The crystalline basement geology is part of

the Mozambique Orogenic Belt with a dominant north-south trending deformation.

The Basement complex had undergone various stages of deformations and erosion

before the volcanic flows.

According to Mengesha and Seife Michael (1982) the regional geological mapping of

the Gore sheet that includes the study area, has four major domains in the

metamorphic basement. These are the Baro domain, Birbir domain, Geba domain, and

Yubdo domain. Mengesha (1982) illustrates planar features are manifested by

gneissic banding on layering and foliation in rocks of the Baro group. The Baro and

Geba domain rocks are commonly high-grade gneisses; whereas the Birbir rocks are

low grade metasedimentary and metavolcanic schists (Greenschist to lower

Amphibolite facies). The Birbir domain both to the West and East is bounded by the

high grade metamorphic rocks of the other two domains. The Yubdo Domain

represents an Ophiolitic succession consisting of Mafic and Ultramafic rocks in the

North Eastern part of the mapped Gore sheet (Figure 8).

16

Fig

ure 8 .R

egio

nal Geo

logical m

ap o

f South W

estern E

thiopia (A

fter Men

gesha , 1

996 )

17

Volcanism in Southwestern Ethiopia had started as early as Middle Eocene,

(Davidson, 1983) confirmed it by radiometric age dating. The fluvial lacustrine coal

and oil-shale bearing units are sandwiched between the Lower and Upper Tertiary

Basalts and Upper Tertiary Basalt and high-grade gneiss, (Getahun et al., 1993). Like

the other basins in the Southwestern Ethiopian Plateau (i.e. Delbi and Moye Basin)

the Yayu-Hurumu like Basin deposition was also assumed to be restricted to tectonic

blocks, and it is characterized by alluvial deposition which is followed by widespread

paleo-lake development. The paleo-lake deposition consists of thick fluvial lacustrine

sediments that are assumed to be formed during the Tertiary period (Getahun, et al.,

1993). The presence of fluvio-lacustrine coal and oil shale-bearing sediments are well

known to intervene in the Tertiary volcanic of Ethiopia (Wolela, 2007, 2008); there

are strong evidence that the NNW-SSE fault structure provided the tectonic

relationship for the expansion of grabens and half-grabens. The Basin subsidence,

with syn-depositional faulting, was probably an important control on sedimentation.

According to (Wolela,2014), the sedimentary successions filling Yayu Basins are

composed of terrigenous clastic rocks (Sandy conglomerates, Sand stones, Siltstones,

and Mudstones), biogenic sedimentary rocks (Carbonaceous shales, Carbonaceous

Clay stones, Carbonaceous Mudstones, Coal, and Oil shale seams), and volcaniclastic

sedimentary rocks. Generally, Southwestern Ethiopia is composed of Precambrian,

Paleozoic, and Mesozoic sediments and Cenozoic rocks oldest to youngest

respectively.

2.6.1 Precambrian

According to Mengesha et al, (1996) divided the Precambrian rocks of southwestern

Ethiopia into Archean (Baro and Alghe Group) and late Proterozoic (Tulu Dimtu and

Birbir Group). The low-grade Meta volcano-sedimentary and associated intrusive

rocks exposed remarkably persistent and can be traced for the entire length of the

Precambrian of Western Ethiopia. The group vary in width along strike that is wider

in the north and narrower in the South. Further South the assemblage pinches out and

truncates by the NW-trending Surma shear zone.

18

Previously, they are referred to as upper complex (Kazmin, 1972) and have long been

considered as the Southern continuation of the Pan-African Arabian-Nubian Shield

and were correlated to the Juvenile Pan-African assemblage of Northern Ethiopia,

Eritrea, and SE Sudan.

2.6.2. Paleozoic and Mesozoic Sediments

A few outcrops of the Karoo system have been identified at Gilo and Kari in SW

Ethiopia. Regionally Mesozoic sediments, are absent in Western Ethiopia indicating a

synchronous regional uplift in this part (Kibrie, 2000). Similarly, in the study area, no

exposed older rock units were going down beyond Cenozoic volcanic.

2.6.3. Cenozoic Rocks

During Cenozoic Ethiopia has excised extrusion of immense among units of volcanic

together with plateau uplift and rift development, volcanism has started as early as

Eocene (Davidson,1983; Ebinger et al.,1993) with extensive development during

Oligocene (Kazmin,1979; Davidson,1983).

The Cenozoic Ethiopian volcanic province can be divided into two major series.

These are (i) the Plateau (trap) volcanic, and (ii) the Rift volcanic. The study area is

formed by the Southwestern Plateau volcanic. According to (Merla et al., 1979)

subdivided the southwestern Ethiopia flood basalts into three stages: - (1) the Omo

Basalts (40 to 25 Ma), (2) the Jimma Volcanics (30 to 21 Ma), and (3) the Wollega

Basalts (15 to 7 Ma). Davidson and Rex (1980) also recognized three units: - (1) the

Main Sequence (49.4 to 30.5 Ma), (2) the Makonen Basalts (32.8 to 21.2 Ma), and (3)

a Post-rift sequence (13.0 Ma to present day). Berhe et al. (1987) identified four

formations in western and southwestern Ethiopia. These are from oldest to youngest:-

(1) Geba Basalts, (2) the Lower aphyric basalts, (3) the Upper basalts, and (4) the

Tulu Wolela and Sayi central type trachytic and transitional lavas. According to

(Mengesha et al., 1996) identified two volcanic units in the southwestern Ethiopian

flood basalts. These are; the Jimma Volcanics and the Makonen Basalts.

2.7. Regional Geological Structures

The East African Rift system is generally considered to be associated with the

rejuvenation of an ancient tectonic lineament and possibly have had an early origin in

Precambrian Pan- African Orogenic activity (McConnell, 1972: Korme et al., 2004).

19

The extensions of NNW to SSW, N-E to SW, EW, and NNE to SSW fault systems

are related to the East African Rift system. These fault systems were supplemented by

voluminous lava flows. The NNW to SSW Rift system created graben and half-

grabens to be became sites of sedimentation in the Yayu Basins (Wolela, 2014).

According to Wolela ( 2014) the distribution and the rocks association in the Yayu

Basins are explained concerning the Precambrian Orogenic belt and the younger rift

tectonics. The structural evolution of the Yayu Basin is in accordance with the NNW-

SSE, E-W extensional tectonics, and the main Ethiopian rift, which accounted for the

structural complexities of the basins. These rift systems were accompanied by

volcanic activities. Eocene-Early Oligocene, a shallow proto rift was formed in the

SW Ethiopian Plateau, which is closely related to the extensional tectonics (Sefu

Michael et al., 1987).

According to Kibre (2000) the E-W trending faults at the southern margin of the area

Yayu fault may be considered to be the major structure responsible for the formation

of the graben. The sedimentary sequence, on these blocks, varies in thickness and

sediment distribution. Normally, the attitude of the sedimentary unit is horizontal,

deposit onto the blocks that may locally slightly tilt to form minor half grabens.Any

significant lateral or vertical structural change in a coal seam has a direct bearing on

its thickness, quality, and mine ability.

2.8. Stratigraphy of Geba Basin

According to Kibre (2000) sedimentary sequence of Geba Basin is consists of coal

and Oil shale bearing rocks the basin consists of Precambrian rocks, tertiary

sedimentary rocks, and tertiary volcanic.

The Stratigraphy of the Geba Basin is the oldest to the youngest as follows;

Crystalline Basement, Lower Basalt, Coal and Oil shale bearing sediments, and Upper

Basalt respectively (Kibre, 2000).

2.8.1. Crystalline Basement

The Basement complexes are dominated by biotite–quartz–feldspathic gneiss. These

basement rocks in the area are categorized under the Geba domain (Tekle Wold and

Moore, 1989), the upper part of the crystalline basement is highly weathered.

20

It is composed of sand-size aggregates of quartz and kaolinite feldspars and seems

that it is the result of in-situ weathering. Non resistant minerals like micas and

feldspars are altered into kaolin.

2.8.2. Lower Basalt

According to Wolela (2007) the Lower Basalt unconformable overlain the

Precambrian basement rocks, reaches a maximum thickness of 100m. The unit is

highly fractured in three directions, and in-filled by secondary minerals silica, calcite,

and Zeolite. These lower Basalt separated by the number of weathered surfaces and

dated to be 36.32 Ma (Merla, 1979).In the Ethiopian Trap Series classification, the

volcanic rocks underlying the Coal-bearing sediments (strong unconformity within

the Trap Series) is known as Ashengi Basalt in the North and Akobo Basalt in

Southern Ethiopia.

2.8.3. Coal and Oil Shale Bearing Sediments

The coal-bearing sediments unconformable deposited either on the Precambrian rocks

or Lower Basalt (Wolela, 2007). It is deposited in NNW to SSE trending grabens. The

Coal seams are associated with various types of sediments in various places to the

place and stream sections. The grain size of the sediments interbedded between the

roof of the top most coal seams and the floor of the lower most coal seam changes

from Clay size to very coarse sand size from East to the West. The sediments

associated with the Coal seams become coarser towards West from the present study.

2.8.4. Upper Basalt

Upper Basalt is a part of Makonen Basalt whose absolute age ranges between 34 and

23.1 Ma (Davidson, 1983). Upper Basalt is one of the most extensive rock units that

comprehends several flows and presumably covers almost the Southern and SE parts

of the study area. In the Eastern parts, it includes a thick succession of reworked

pyroclasts. It occupies topographic highs and forms peaks continuous SE to SW

running ridges; the upper Basalt unconformable overlies the sedimentary rock

sequence of the area.

21

There are sporadic fresh outcrops, which are characterized by dark gray color and

aphanitic texture. Mengesha and Seife Michael (1982) correlated these Basalts to the

Jimma volcanic, whose age ranges determined by (Merla et al.,1979) to be between

27 and 15 M.Y. They also correlated it to Zanetin and Justin Visentin's Allagi Basalt

(1974) and Mekonen Basalts of (Davidson et al., 1976) that have similar age to Jimma

volcanic.

Figure 9.Lithostratigraphic column of Geba Basin (After Kibre,2000)

22

CHAPTER THREE

3. MATERIALS AND METHODS

3.1. Materials

Different materials have been used and different methods have been applied in the

fieldwork and the office. Detail field studies by follow-up the lithological exposures

on road-cuts, stream cuts, quarry site, and fresh coal sample collection for laboratory

analysis were carried out in the field.

Coal samples were collected through both surface and subsurface approaches. From

all the studied section Twenty-Two (22) fresh coal samples were collected. But, we

discarded seven samples since they were homogeneous in nature and used for further

studies, and fifteen (15) samples were analyzed. From the Achibo quarry site Four ( 4)

samples, Hada Bekele three (3 ) samples Sombo two(2 ) samples, Dawe and Debeso

(1) sample from each, a total of eleven (11) samples were selected for all stream

sections depend on the Coal bed sequence, and four (4) core sample was taken from

COFCOP company. The core sampling was done where the exposure of coal is

unavailable in the study area. These four core samples were taken one Coal sample

from each of Sheno, Witate Jeto, Witate Muchuchato, and Achibo Tebel area. From

these, fifteen (15) coal samples (Table 1) were analyzed for proximate, calorific

value, and sulfur at a laboratory of Geological Survey of Ethiopia.

Different materials were used for field data collection and the lithological unit sketch

to achieve the stated research problem, for the general and specific objectives of this

research study. The different field instruments present at the College of Applied

Science department of Geology Addis Ababa Science and Technology University

were used to carry out field data collection, coal samples and to measure the

lithological unit thickness in the study sections. These are GPS, sample bag, plastic

bag, Brunton compass, a geological hammer, notebook, pen, marker, meter stick,

hand lenses, digital camera, chisel, and two topographic maps with a scale of 1:50,000

( Yayu and kumbabe). Golden Starter, Surfer, Arc GIS⃰, DEM, Global Mapper, and

Google Earth Software’s were utilized to analyze and interpret the data used for the

current study. Generally, the works of the research were conducted by ( Figure10 ).

23

Table 1.Location of Coal sample selected for analysis from out crop

S/N Sample

ID

Geographic

Coordination

Elevations

(m)

Thickness

(m)

Sample

name

Site of

location

Easting Northing

1 AQS1 0830219 0929099 1516 1.7 Coal Achibo

2 AQS2 0830219 0929099 1516 0.64 Coal Achibo

3 AQS3 0830219 0929099 1516 0.45 Coal Achibo

4 AQS4 0830219 0929099 1516 0.6 Coal Achibo

5 AHBS1 0830145 0929022 1532 0.8 Coal Hada Bekela

6 AHBS2 0830145 0929022 1532 1.7 Coal Hada Bekela

7 AHBS3 0830145 0929022 1532 2 Coal Hada Bekela

8 ADS1 0170648 0928097 1539 1.6 Coal Debeso

9 DAS2 0172257 0927147 1502 4.8 Coal Dawe

10 SGS12 0828327 0929246 1518 4 Coal Sombo

11 SGS14 0828327 09292446 1518 4 Coal Sombo

Note: AQS-Achibo Quarry site Coal Seam1, 2, 3, 4 respectively. SGS14-Sombo Genji Coal Seam 1, Sample no 4

DAS-Dawe Abote Coal seam 2 ADS-Achibo Debeso Coal Seam 1

AHBS-Achibo Hada Bekela Coal Seam 1, 2, 3 respectively

SGS12-Sombo Genji Coal Seam 1, Sample no 2

Table 2.Location of Core Coal sample selected for analysis from bore hole

S/N

Sample

ID

Easting

Northin

g

Elevati

on

Depth

(m)

Thickness

(m)

Sample

Name

Sample

location

1 WJBH1 0825605 0927533 1603 170.7 7.4 Coal Witate

2 SHBH2 0824143 0924823 1907 464.7 8.37 Coal Sheno

3 ABH2 0169809 0927914 1686 144.5 2.5 Coal Achibo

4 WMBH1 0821713 0926342 1633 18.3 8.26 Coal Witate

Note: SHBH2-Sheno Bore Hole no 2 ABH2-Achibo Bore Hole no 2 WMBH1-

Witate Muchuchato Bore Hole no 1 WJBH1-Witate Jeto Bore Hole no 1

3.2. Methods

3.2.1 Data Acquisition

Literature review and collection of available information from the previous geological

investigation of the study area were undertaken. Traverses and field observations were

carried out depend on the availability of Coal expo

section along with the stream cuts, and quarry site. From all the section twenty

fresh coal samples were collected and fifteen samples were analyzed. From the

Achibo quarry site, Hada Bekele, Sombo, Dawe, Debeso ,Witate

Jeto from bore hole ),and Sheno from bore hole , the core sample collected from bore

hole was taken from COFCOP company. The core sampling was done where the

exposure of coal is unavailable in the study area. Studies focusing on

sedimentological descriptions (concerning on textural, compositional, physical

properties like color identification) measured the lithological thickness by bed to bed

in all sections of the study area.

Figure 10.Methodology Flow charts

24

3.2.1 Data Acquisition



carried out depend on the availability of Coal exposure divided the area into seven

section along with the stream cuts, and quarry site. From all the section twenty


Achibo quarry site, Hada Bekele, Sombo, Dawe, Debeso ,Witate




ogical descriptions (concerning on textural, compositional, physical


in all sections of the study area.

Methodology Flow charts



sure divided the area into seven

section along with the stream cuts, and quarry site. From all the section twenty-two


Achibo quarry site, Hada Bekele, Sombo, Dawe, Debeso ,Witate(Muchuchato and




ogical descriptions (concerning on textural, compositional, physical


25

Litho logic unit log from the observed exposures of the Coal seams and geological

map of study area was undertaken at the field and representative Coal samples were

collected was tightly wrapped with masking tape in a plastic bag for the sake of

preservation for laboratory analyses such as proximate, sulfur, and calorific value by

following the International and national standards coal analyses guidelines i.e.

American Society for Testing and Materials standards for coal analyses (ASTM) (J.

G. Speight, 2005). The selected samples were analyzed at a Geological Survey of

Ethiopia laboratory in December 2020.

3.3. Data Analysis

Laboratory data analyses were conducted on collected samples. The aim of the sample

analysis carried out were to determine grade, rank, moisture content, volatile matter,

Figure 11.Figure showing sample points taken from the studied area

26

ash, and fixed carbon contents of the coal for essential characteristics for the

indication of coal quality.

3.3.1. Proximate Analysis Procedure

The moisture content analyses on the gross samples were screened for 60 mesh

analysis. This method involved oven-drying on a known mass of Coal sample to a

constant mass at a temperature of 105 to 110°C for 1hrs by using (ASTM) standard.

The moisture content was calculated from the loss in mass of the sample.

The ash content analysis procedure for ash determination is in the way, first,

accurately weighing the sample and reduces to pass a sieve of 212μm aperture. Then

it is heated at a uniform heating rate in a furnace from room temperature to 500°C

over a period of 60 minutes. This was held at this temperature for 30 minutes (60

minutes for brown coals). Again the sample heated to 815°C ± 10°C and maintained

at this temperature for a minimum of 60 minutes until the sample is constant in mass.

The volatile matter content of coal is analyzed as described in ASTM standards based

on the same principle and is similar. Approximately 1 g, for general analysis, of coal

sample with a size of 250μm (ASTM) is heated to 950°C ± 25°C in a Carbolite

furnace for a total of exactly 7 minutes. After that, the result is determined by the

oven and reported.

Fixed carbon is not determined directly, but it is the difference, in an air-dried coal,

between the total percentages of the other components, that is moisture, ash, and

volatile matter and 100%.

3.3.2. Calorific Value Analysis Procedure

According to Qian Zhu (2014) the calorific value analysis procedure is as follow; the

standard methods for determining CV of coal employ calorimeters and burning coal in

oxygen under pressure in a closed system. The bomb calorimeter provides the most

suitable and accurate apparatus for determination of the CVs of solid and liquid fuels,

and is adopted in ASTMD5865-12(Standard test method for gross calorific value of

coal.

In the bomb washing method, sulfur is precipitated as barium sulphate from the

washing from the oxygen bomb calorimeter following the calorimetric determination.

27

Subsequent to opening, the inside of the bomb is wash carefully, and the washings are

collect.

After titration with standard sodium carbonate solution to determine the acid

correction for the heating value, the solution is heated and treated with ammonium

hydroxide to precipitate iron ions as ferric oxide. After filtering and heating, the

sulphate is precipitated with barium chloride and determined gravimetrically (Zhu,

2014).The sulfur content of the study area done followed the above procedure.

The studied sample rank classification based on the American society for Testing and

material (ASTM, D388-1999), and grade is based on the Government of India

Ministry of coal (htt://www.coal.nic.in/point html).

28

CHAPTER FOUR

4. RESULT

4.1 Lithological succession

The geology of Achibo-Sombo area encompasses three rock groups: - Precambrian

basement rocks, Mesozoic sediments and volcanic rocks. The Basement rock in the

study area was rare observed at the outcrop, but it is available from the borehole data

at the bottom of the Lower Basalt which consists of biotite gneiss, quarto-feldsphatic

gneiss with few pegmatite and quartz veins. Which it is observed from the borehole

location at (Figure 11) and lithostratigraphic succession (Figure 26 and 27).It is

distributed at the NE and some at the central of the study area.

The Lower Basalt rock is slightly observed in the SE and NW parts of study area. It

was observed along cut streams underlying the sedimentary rock, slightly weathered

composed of feldspar grains which is observable under hand lens. Near the contact

with the overlying sedimentary sequence, it is frequently appears to be stratified

parallel - sub parallel to the surface .But, further down the stream it develop to the

columnar joints.

4.1.1. Fluvio-Lacustrine Sediments (Coal Bearing Unit Section)

The sedimentary strata of the study area comprise continental clastic of fluvio-

lacustrine origin. Mostly, sedimentary succession is unconformable underlain Lower

Basalt unit. However, fluvio-lacustrine succession mainly consists of Argillo-

arenaceous sedimentary rocks such as unconsolidated Sand stones, Mud stones,

Siltstones, Clay stones, Oilshale and Carbonaceous shales. Generally the coal bearing

strata of Achibo-Sombo area were classified in to seven major Stratigraphic sections

based on coal exposed, color, texture and thickness found in different in stream

section, Quarry site and borehole data.

4.1.1.1. Dawe Section

This section is located in the Dawe village Eastern parts of Achibo quarry site and NE

of Achibo village closer to the Geba river which covered by fluvio- lacustrine

sediments and volcanic clastic sediments.

These lithologies are slightly weathered around the Abote stream margin and highly

weathered surround of the

joints with the some plant f

to the top Lower Basalt, Coal ( 4.8m thick),Silt stone (0.5m th

thick),and Oil shale (1m thick) respectively. I

of (Figure 19).

Figure 12..Field photo shows very thick Coal bed at Dawe section

4.1.1.2 Debeso Section

This section is located

exposed by the stream cut. The strata exposed were consists of upper Basalt 1m thick

slightly weatherd underlain by Oil s

exposed at this area is less fissi

29


weathered surround of the stream. It is consists of the parallel lamination, cleats and

joints with the some plant fossils. The strata exposed in this stream were from bottom

ower Basalt, Coal ( 4.8m thick),Silt stone (0.5m th

hale (1m thick) respectively. It is shown at lithostratigraphic column

.Field photo shows very thick Coal bed at Dawe section

4.1.1.2 Debeso Section

This section is located NE of Achibo quarry site and consists of few lithologies


htly weatherd underlain by Oil shale and overlain by vegetation.The Oil s

exposed at this area is less fissility and visible it is 0.1m thick.


It is consists of the parallel lamination, cleats and

am were from bottom

ower Basalt, Coal ( 4.8m thick),Silt stone (0.5m thick),Coal (1.2m

t is shown at lithostratigraphic column

of Achibo quarry site and consists of few lithologies


overlain by vegetation.The Oil shale

The third layer coal seam which overlain Oil s

is Mud stone 1m thick which massive structure, the fift

thick underlain Oil shale 0.3m thick.

4.1.1.3. Tekeshe Stream Section

The thicker Oil shale is observed about 4m to 10 m thick (Tekeshe stream),

characteristically. It includes the intercalation of Mudstone with Siltstone, and rarely

Coal observable within thin beds which less than 0.1m particularly in Tekeshe stream

in the NE parts of the A

dark brownish gray and is characterized by the alternation of thin and thick

laminations. Plant fossil and concretions are commonly associated with the thic

laminated part of this Oil s

Figure 13..Field photo taken from Debeso section

30

r coal seam which overlain Oil shale is 1.6m thick, and the fourth layer

is Mud stone 1m thick which massive structure, the fifth strata is coal be

hale 0.3m thick.

4.1.1.3. Tekeshe Stream Section

hale is observed about 4m to 10 m thick (Tekeshe stream),



parts of the Achibo-Sombo area. Its color varies between a light gray to


laminations. Plant fossil and concretions are commonly associated with the thic

laminated part of this Oil shale.

.Field photo taken from Debeso section

hale is 1.6m thick, and the fourth layer

h strata is coal bed which 2m

hale is observed about 4m to 10 m thick (Tekeshe stream),



Sombo area. Its color varies between a light gray to


laminations. Plant fossil and concretions are commonly associated with the thickly

31

Figure 14. Field photo taken from Tekeshe section show laminated Oil Shale

4.1.1.4. Sombo-Section

This section is located NW of the Achibo quarry site and it is covered by coffee

vegetation and forest. The Sombo Genji stream is divided lithology into East and

West parts, the west parts form joint sets in the Oil shale strata while the Eastern parts

more exposed coal seam the coal seam found in this stream is black in color and very

hard relative to the other place of my study area. This exposed coal is affected by

water which flows from this stream whereas not weathered as the other place of the

study area. The first layer of this strata is Oil shale (2.5m thick) which is parallel

lamination from East to West direction and composed of fossil root plants, the second

strata are thin layer strata Carbonaceous shale (0.5m thick) intercalated fossil stem or

woody fossil brown to reddish color. The third layer is Oil shale(3m thick) dark gray

in color also fissility, the fourth strata are coal seam (4m thick) highly exposed and

hard coal it is black in color and conchoidal fracture form cubic geometry, the fifth layer is

Mudstone (0.1m) light gray color and Shally characterized at the top, sixth strata is coal

(0.4m) thick black to dark

ninth layer coal (0.5m thick), mudstone (0.

4.1.1.5. Achibo Quarry site section

The Achibo quarry site is absolutely found between NW and SW of Achibo village;

far from this village approximately 2

stream and in the Northern part by Geba River and in the Western

Bekela stream also at the SE by Achibo village. In the present day, this quarry site is

exposed on the surface by human activity of small micro

of “Qeerroo and Qarree

this time, the coal deposit was highly visible and exposed by surface mining and

excavation. Whereas bounded in all directions by coffee vegetation with forest.

In the Southern parts of this site, it is a high cliff relative to the other direction which

is covered by 10m thick Sand soil intercalation with Mud and Clay.

Figure 15.A) Sombo section Eastern and B) Western Coal deposit field photos

32

(0.4m) thick black to dark color, and the seventh layer is Mudstone (0.5m thick), eighth and

oal (0.5m thick), mudstone (0.2m thick) respectively.

Quarry site section


far from this village approximately 2-2.5km. It is bounded in the NE part by Tekeshe

stream and in the Northern part by Geba River and in the Western


exposed on the surface by human activity of small micro

Qarree” group done by surface mining method since 2018. During

me, the coal deposit was highly visible and exposed by surface mining and



ed by 10m thick Sand soil intercalation with Mud and Clay.

A) Sombo section Eastern and B) Western Coal deposit field photos

color, and the seventh layer is Mudstone (0.5m thick), eighth and


2.5km. It is bounded in the NE part by Tekeshe

stream and in the Northern part by Geba River and in the Western parts by Hada


exposed on the surface by human activity of small micro-enterprise

” group done by surface mining method since 2018. During

me, the coal deposit was highly visible and exposed by surface mining and



ed by 10m thick Sand soil intercalation with Mud and Clay.

A) Sombo section Eastern and B) Western Coal deposit field photos

This quarry site contains four coal seams and an Oil s

to excavation activity. The plant fossils and sedimentary structure parallel lamination,

cross lamination, cleat

distribution in this site was included: A

thick), Coal (2m thick), Oil s

Coal (1m thick), Oil s

shales were exposed with various propert

(Figure 23)

A) Field photo taken from northern part of the quarry site show high thick coal visible. B)

Field photo taken from southern of quarry site confirm high thick of Oil Shale and Coal C)

Photo taken from Eastern

alluvial sediments D) Photo taken from Western of quarry site explain alluvial impose by

alluvial sediment and thin Oil s

Figure 16. Field photo taken from Achibo Quarry site

33

ins four coal seams and an Oil shale bed which is exposed due


cross lamination, cleats, and wave ripple lamination are observed. The lithology

ion in this site was included: Alluvial sediments (10m thick), Oil s

thick), Coal (2m thick), Oil shale ( 2m thick), Coal (1m thick), Oil s

Coal (1m thick), Oil shale (1m thick), coal (1m thick ) from top to bottom and

hales were exposed with various properties shown Lithostratigraphic column of

rom northern part of the quarry site show high thick coal visible. B)


Photo taken from Eastern of quarry site illustrate Oil shale and Coal highly over burden by

uvial sediments D) Photo taken from Western of quarry site explain alluvial impose by

alluvial sediment and thin Oil shale and Coal.

Field photo taken from Achibo Quarry site

hale bed which is exposed due


s, and wave ripple lamination are observed. The lithology

ial sediments (10m thick), Oil shale (3m

Coal (1m thick), Oil shale (2m thick),

hale (1m thick), coal (1m thick ) from top to bottom and Oil

ies shown Lithostratigraphic column of

rom northern part of the quarry site show high thick coal visible. B)


hale and Coal highly over burden by

uvial sediments D) Photo taken from Western of quarry site explain alluvial impose by

4.1.1.6. Hada Bekela Stream Section

This section is relatively found on the Western of Achibo

three kilometers far from Achibo

shales with Coally shal

underlain by Oil shale has similar properties with the Eastern parts of Achibo

site and lesser in thickness. The visible coal seam found in this area

mixed with Oil shales

fissility intercalated with wood fossil very thin lamination 0.8m thick, the third layer

is coal which very fragile and thin seam combustible black color and easily broken by

finger print consists of leaf fossil and few amount of mud equ

overlain Oil shale. The fourth layer is harder than the o

Coally shale thin bed 0.4m th

and sixth layer strata is s

the pond which flow from the upper layer 1.7m thick

shale, and last visible layer is coal 2m) thick.

Figure 17.Field photo taken from Hada Bekela section.

stream. B) From Northern of the stream34

4.1.1.6. Hada Bekela Stream Section

This section is relatively found on the Western of Achibo-quarry site which is around

three kilometers far from Achibo-village and contains different coal seams and Oil

hale that varies in thickness exposed by excavation.

hale has similar properties with the Eastern parts of Achibo

site and lesser in thickness. The visible coal seam found in this area

hales from top to bottom (alluvial sediments 4.5 m thick, Oil shale



sts of leaf fossil and few amount of mud equ

hale. The fourth layer is harder than the overlain Coal seam which

hale thin bed 0.4m thick. The fifth layer Oil shale highly laminated 2m thick

and sixth layer strata is stratified East to West visible coal seam relatively affected by

the pond which flow from the upper layer 1.7m thick underlain by 0.28m thick Oil

hale, and last visible layer is coal 2m) thick.

Field photo taken from Hada Bekela section. A) From southern of the

stream. B) From Northern of the stream

quarry site which is around

s different coal seams and Oil

e that varies in thickness exposed by excavation. The sediment

hale has similar properties with the Eastern parts of Achibo-quarry

site and lesser in thickness. The visible coal seam found in this area is three seams

from top to bottom (alluvial sediments 4.5 m thick, Oil shale



sts of leaf fossil and few amount of mud equal thick with the

verlain Coal seam which

hale highly laminated 2m thick

tratified East to West visible coal seam relatively affected by

underlain by 0.28m thick Oil

A) From southern of the

35

4.1.1.7. Witate –Section

This section is located at the Western of Achibo, and SW of Sombo village consists of

three different lithologies which vary in thickness vertically from top to bottom: Oil

shale ( 3m thick), Mudstone ( 2m thick), Oil shale (1m thick), Coal (0.5m thick), Oil

shale (6.5m thick), Coal (1m thick), Oil shale(7m thick), Coal (1m thick), Mudstone

(0.5m thick ), Coal (0.5m thick), Oil shale ( 2.5m thick), Coal (0.5m thick), Mudstone

(0.5m thick) respectively. The sedimentary structure found in this section is identical

to the other section. It contains parallel lamination Oil shale, cross lamination, wave

ripple lamination, and massive Mudstone.

4.1.2. Volcanic Clastic Sediments

Volcanic Clastic Sediments are represented in the studied area by Tuffaceous beds,

whose thickest formation is observed mostly at the N and NE. This sediment is crops

out at the upper parts of the fluvio lacustrine sediments and is closely related to the

upper Basalt. It is mostly consists of the weathered upper Basalts. The lateral

extension of this volcanic clastic is rare observed in the Southern parts.

This sediment is the topmost reworked Tuffaceous (volcanic clastic) dominated

sediment; it is in the field observed vary in color place to the place the group of these

sediment is composed of bluish gray, bluish green, greenish blue, green, light gray,

grayish brown, reddish brown, and brown, Clay size, Silt size, and Sand size mainly

reworked volcaniclastic Mudstones. The sediments in general are massive, soft and

friable. At places weakly developed and sometimes well-developed sedimentary

structures such as lamination, slump or load cast, cross lamination and horizontal

stratification are observed. The Sandstones are poorly sorted, massive, composed

mainly of rock fragments and Coal debris.

4.1.3. Upper Basalt

Upper Basalt is one of the most extensive rock units comprehends a number of flows

and presumably covers almost the Southern and SE parts of the study area. In the

Eastern parts it is includes a thick succession of reworked pyroclasts.

It occupies topographic highs and form peaks continuous South east to SW running

ridges, the Upper Basalt unconformable overlain the alluvial sediments of area.

36

4.2. The sub-surface Coal-bearing Lithological succession in the Study Area

Subsurface exploration has been conducted in the Achibo-Sombo area and data

incorporated in this study contain that of 10 boreholes drilled and confirm by the

geophysical method of natural gamma and density responses during 1998 and 2007 by

Ethiopian Mineral Resource Development Enterprise and COFCOP respectively. The

location of each borehole is given in (Figure 11) and their Lithostratigraphic

succession were in (Figure 26 and 27) the drilled boreholes revealed the different

lithological succession. In the boreholes the Coal and Oil shale bearing sedimentary

sequences are encountered being sandwiched between the basement complex and

Upper Basalt.

According to EMRDE (1998), the cores from boreholes drilled at the Southern parts

of the study area, BH-5, and BH -18 include lenses like vesicular and amygdaloidal

Basalt layers that have dark gray to light gray color. The thickness of the sedimentary

rocks varies between 35.56 m (BH-4) and 162.73m (BH-5). This sedimentary unit

shows thickness and facies variations both laterally and vertically. The thickest

section of the sequence is found in the Southern part of the area (BH-5) where it

attains a thickness of 157.45m. The thickness of the coal-bearing sedimentary unit

progressively thins out to 36.15m further to the NE and NW at borehole BH-4.

The general lithology units of the study area are characterized by the similar structural

appearance and physical properties. Almost all of them are relatively fresh and mostly

possess horizontal laminations and fissility (weak discontinuity planes) observables

from the fieldwork and borehole data are:-Shale, Sand stone, Mud stone

Carbonaceous mudstone, Siltstone, Claystone, Oilshale, Coal, and Alluvial sediments.

37

Figure 18.A) Geological Map and B) Cross-sectional Map of the study area

38

4.3. Litho Stratigraphic succession of Coal Bearing Strata

According to Wolela (1991, 1992) the majority of coal deposits in Ethiopia are

stratigraphically inter-trappean sediment deposit. The lithostratigraphy of coal-bearing

strata in the Achibo Sombo area from both fieldwork and borehole data: the

crystalline basement, Lower Basalt, Sedimentary rocks, and Upper Basalt from the

oldest to youngest respectively. The fluvio-lacustrine coal and Oil shale bearing units

are sandwiched between the Lower and Upper Tertiary Basalts and Upper Tertiary

Basalt and high-grade gneiss, (Getahun et al., 1993). The lithostratigraphy observable

in all section of the study area are briefly discussed in this paper (section; 4.1 to 4.2)

and Litho stratigraphic succession (Figure 19 to 27). At the majority stream section of

the study area, the coal-bearing strata are covered by alluvial sediments and Oil shale

on the upper parts (i.e.Achibo-Quarry site, Dawe, Hada Bekela, Tekeshe, Witate, and

Sombo) sections and no upper Basalt was observed but in the Debeso section, it is

visible. Also from the borehole data, only the BH-18 is covered by Upper Basalt on

the top otherwise it is alluvial sediments on the upper parts.

Generally, the coal-bearing strata in the Achibo Sombo area are sandwiched between

Lower Basalt and alluvial sediments in the majority sections, Lower Basalt and Upper

Basalt at the minimum places bottom to top respectively, according to their position in

Lithostratigraphic sequence units of coal-bearing sedimentary rocks in the study area.

The lithostratigraphy of the Achibo-Sombo area based on the physical features of

litho logy the coal-bearing strata found in different in stream sections (and quarry

sites are showing (Figure 19 to 25) and from borehole data (Figure 26 and 27) the

detail unit logs are shown.

39

Figure 19.. Lithostratigraphic column of Dawe section

This lithostratigraphic succession of Dawe section is contain three different lithologic

unit (two coal seam) were observed in outcrop, the second coal seam is the highest in

thickness (4.8 m) from outcrop of the study area. Note: As shown in the figure 19 the

lithostratigraphic unit was prepared by using Golden software (starter version 5 and

surfer Version 10).

40

Figure 20.Lithostratigraphic column of Debeso section

As observed from above figure this section is consists of four unusual lithologic units

and unlike sedimentary structure with plant fossils. Hint: As shown in the figure 20

the lithostratigraphic succession was prepared by using Golden software (starter

version 5 and surfer Version 10).

41

Figure 21.Lithostratigraphic column of Tekeshe section

As observed from this stratigraphic section this section is highly covered by Oil shale

which only one thin Coal seam is overlain by Oil shale and underlain by

Carbonaceous Shale. Clue: As shown in the figure 21 the lithostratigraphic unit was

prepared by using Golden software (starter version 5 and surfer Version 10).

42

The lithostratigraphic section of Sombo Genji stream four variable lithologic unit and

four coal seams are observed as shown in this figure the first coal seam is high in

thickness and cleat structure is observed. Note: As shown in the figure 22 the

lithostratigraphic unit was produced by using Golden software (starter version 5 and

surfer Version 10).

Figure 22.Lithostratigraphic column of Sombo section

Figure 23.Lithostratigraphic column

From observed figure above the coal seam were

These coal seams were currently under exploration.


surfer Version 10).

43

Lithostratigraphic column of Achibo Quarry site Section

From observed figure above the coal seam were overlain and underlain by Oil s

These coal seams were currently under exploration. Hint:


underlain by Oil shale.

Hint: The figure23


The coal seam found from these lithologic units was currently under exploration,

which it is exposed by stream cut called Hada Bekela stream.

lithostratigraphic unit was prepared by usi

surfer Version 10).


44


which it is exposed by stream cut called Hada Bekela stream. Clue:


.Lithostratigraphic column of Hada Bekela section


Clue: The figure 24

ng Golden software (starter version 5 and


As observed from the figure above this lithostratigraphic section is consists of five

coal seam which overlain and underlain by Oil s

underlain by Oil shale and Mudstone at the bottom of stream respectively.

45

.Lithostratigraphic column of Witate Section


overlain and underlain by Oil shale at top of stream and

hale and Mudstone at the bottom of stream respectively.


hale at top of stream and overlain and

hale and Mudstone at the bottom of stream respectively.

46

Figure 26.Detail Lithostratigraphic column of (BH-3,BH-4,and BH-5)

Clue: The figure 26 lithostratigraphic succession was prepared by using Golden

software (starter version 5 and surfer Version 10).

47

Figure 27. Detail Lithostratigraphy of (BH-7, BH-10, and BH-18)

Note: The figure 4.16 lithostratigraphic unit was prepared by using Golden software

(starter version 5 and surfer Version 10).

48

4.3.1. Lithostratigraphic succession Correlation

The coal bearing strata of the study section are characterized by Oil shale, Mud stone,

coal, Carbonaceous shale and Lower Basalt associated with plant fossil; plant roots,

plant stem, plant leaf and laminated sedimentary structures; wave- ripple lamination,

cross lamination, parallel lamination, concretion and joints in Tekeshe section, and

Hada Bekela section and Achibo quarry site section which have additionally alluvial

sediments, Coaly shale and cleats whereas, the Debeso, and Dawe, section are

characterized by Upper Basalt, Oil shale, Coal, Mudstone intercalated with some

organic fossils of plant root, stem and leaf with the sedimentary structure

cleat,concretion,parallel lamination, cross lamination and massive. Additionally the

Sombo and Witate sections are consists of all lithology and sedimentary structure

which found in Dawe and Debeso sections, even more Carbonaceous shale, and wave

ripple lamination. From the bore hole data and lithostratigraphic unit (Figure 26 and

27) majority of bore hole were consists of maximum lithology which exposed at

quarry site and stream but vary in thickness and physical properties. The lithological

correlation of establishing Coal bearing strata in the study area can be made by

comparing the physical characteristics of the strata with each other and lithological

similarity.

49

Figure 28.Lithostratigraphic column correlation of each section of study area

Hint: The figure 28 lithostratigraphic column correlation was prepared by using

Golden software (starter version 5 and surfer Version 10).

50

Figure 29.Lithostratigraphic column Correlation of Borehole study area

Note: The figure 29 lithostratigraphic correlation was prepared by using Golden

software (starter version 5 and surfer Version 10).

51

Figure 30. Lithostratigraphic column Correlation of study area within the Basin

Note that: as shown in the figure 30 the lithostratigraphic column correlation was

prepared by using Golden software (starter version 5 and surfer Version 10).

4.4. Coal Quality Analysis

Coal quality of the study area has been evaluated through proximate, calorific value,

and sulfur contents, and the obtained data are tabulated (Tables 3 and 4) and described

in the following sections.

4.4.1 Moisture Content

According to (Yang et al., 2005) moisture content is a very important property that

can greatly affect the burning characteristics of coal.

52

The moisture in coal is one of the vital parameters, which can appraise coal quality

value and effects coal demonstration. , the lower moisture content in coal is a good

thing for coal economic value. The coals of the study area are characterized by very

low 5.38% (WJBH-1) to high 30.27 % (AQS-1), and a total average of 19.52%

moisture content (Table 3). The sample collected from the Western parts of the study

area of witate section (Table 3), borehole (WJBH-1), and borehole (WMBH-1) are a

minimum variation of moisture content 5.38% and 7.30 % respectively. The sample

was taken from Southwestern borehole (SHBH-2) and Northeastern (ABH-2) 8.39 %

and 10.24 % correspondingly.

However, the sample taken from Northeastern parts of the study area Achibo quarry

site section, lithostratigraphy of (Figure 23) AQS-1 to AQS-4 the moisture content is

decreasing downward from first coal seam to fourth coal seam (Table 3). But the

Hada Bekela stream section sample collected from lithostratigraphy of (Figure 24) the

second coal seam (AHBS-2) is high moisture content than the first (AHBS-1) and

third coal seam (AHBS-3). The sample taken from Eastern parts of the study area

Dawe section lithostratigraphy of shown (Figure 19), DAS-2 is the lowest by moisture

content except those of borehole samples. The Sombo section (SGS-14) and Debeso

section (ADS-1) are relatively closer in the moisture content 29.72% and 29.09%

respectively. The moisture content is the most characteristics to identify the coal

quality: the lower moisture value of coal suggesting a higher calorific value. When

moisture content decreases, calorific value increases, and vice versa.

Figure 31.Graphic representation of moisture content by line charts

4.4.2. Volatile Matter

According to Chaney (2010) Volatile matter represent the components of

oxygen and carbon, present in the c

matter of the samples collected in the study area ranges from minimum to the

maximum, 21.27% (WJBH

of Achibo- quarry site (Figure 23

minimum variation of 36.26 % and 37.29% respectively. But the Coal bed (AQS

and (AQS-3) are less variation than those the first two beds 28.95% and 29.19%

respectively.

The sample collected from Hada Bekela streams stratigraphic secti

a first coal bed to third c

(AHBS-2), and 31.27% (AHBS

53

Graphic representation of moisture content by line charts

4.4.2. Volatile Matter

According to Chaney (2010) Volatile matter represent the components of

present in the coal that when heated turn to vapor


maximum, 21.27% (WJBH-1) to 37.29% (AQS-4) (Table 3). The stratigraphic section

site (Figure 23) sample from coal bed (AQS-1) and (AQS

minimum variation of 36.26 % and 37.29% respectively. But the Coal bed (AQS

3) are less variation than those the first two beds 28.95% and 29.19%

The sample collected from Hada Bekela streams stratigraphic section in (Figur

rd coal bed the volatile matter is 27.94 % (AHBS

2), and 31.27% (AHBS-3) respectively.

Graphic representation of moisture content by line charts

According to Chaney (2010) Volatile matter represent the components of hydrogen,

n to vapor. The volatile


). The stratigraphic section

1) and (AQS-4) are

minimum variation of 36.26 % and 37.29% respectively. But the Coal bed (AQS-2)

3) are less variation than those the first two beds 28.95% and 29.19%

on in (Figure 24) in

oal bed the volatile matter is 27.94 % (AHBS-1), 32.10%

54

The sample from the stratigraphic section of Dawe and Debeso (Figure 19 and 20 )

minimum different in the volatile matter only differ 0.30 % of Achibo Debeso stream

section is greater than Dawe Abote stream section (Table 3).

The sample collected from the stratigraphic section of Sombo –Genji stream the

Northern parts of the study area Lithostratigraphic section of (Figure 22) lateral

variation on coal bed sample Id (SGS-12) and (SGS-14) 29.09% and 34.94% from

West to East on the first coal bed. However, the sample collected from the borehole of

the SW 29.71% (SHBH-2) and Western 23.57% (WMBH-1) parts of the study area is

lower than the sample collected from the borehole in the Eastern 34.03% (ABH-2)

parts of the study area. Generally, the volatile matter of the Western part is relatively

lower than the Eastern and the Southern part. It is relatively lower than the Northern

parts of study area.

The amount of volatile matter is used to confirm the rank of coals, to suggest the basis

for coal quality for purchasing and selling, or to establish burning characteristics of

the coal. According to (Stach et al., 1982) the increased volatile matter content is

many characteristics of low-rank coals, even though the decreased value is more

characteristic of higher-rank coals.

4.4.3. Fixed Carbon

Fixed carbon is a combustible matter left in coal after moisture, ash, and volatile

materials are driven off from the coal. The averages of the fixed carbon content of the

samples taken from in the study area are 24.45%. The lowest fixed carbon content is

the sample taken from in the Western parts of the study area 6.29% (WJBH-1) and the

highest fixed carbon content is the sample collected from NE parts 33.23% (AQS-1).

The Lithostratigraphic section of (Figure 19) Dawe section Abote stream Eastern

parts of the study area Coal bed no 2 is fixed carbon content 22.89% (DAS-2) lower

than the sample collected from other bed but higher than the borehole sample except

sample Id (ABH-2),(Table 4.1). The lithostratigraphy of Achibo- quarry site section

(Figure 23) the first coal seam is higher fixed carbon content than the second to the

fourth coal seam,33.23%(AQS-1),24.90%(AQS-2),25.11%(AQS-3),31.88%(AQS-

4)respectively.

55

However, the Lithostratigraphic section of (Figure 24) Hada Bekela stream section the

second coal seam 30.77% (AHBS-2) is higher fixed carbon contents than the first

25.92% (AHBS-1) and third 24.02% (AHBS-3) coal seam.

The sample taken from the Lithostratigraphic section of Sombo-Genji stream (Figure

23) Northern parts of the study area has high fixed carbon content is 31.07% (SGS14)

and the low fixed carbon content is 26.69% (SGS12) higher than the sample taken

from all borehole samples found in the Western, SW and Eastern parts of the study

area. The fixed carbon values are extremely based on the amount of carbon and

organic matter in Coal. The fixed carbon of the study area is increased laterally from

West to the NE and Eastern parts.

4.4.4 Ash Content

The ash content of the sample taken in study area averagely 25.59: the very low ash

0.25 % (AQS-1) and the highest ash 67.05% (WJBH-1). From the Lithostratigraphic

Achibo quarry site section of ( Figure 4.12), four sample collected from each Coal

seam, the ash contents were 0.25% (AQS-1),22.11% (AQS-2),22.06% (AQS-

3),18.83% (AQS-4) correspondingly, the ash contents of the Coal bed no 2 and 3 were

relatively similar while, coal bed no 1 is very least of all sample taken from the study

area. In the other hand, the all core sample collected from Western (WMBH-

1),(WJBH-1), Eastern (ABH-2) and SW (SHBH-2) borehole has high ash contents

rather than the all outcrop sample analyzed except (DAS-2) ( Table 3). The highest

contributor of ash in this area Coal is because of the Claystone of volcanic origin. The

Lithostratigraphic section of Hada Bekela stream NE of the study area (Figure 24),

from the three Coal seams the second bed (AHBS-2) is high ash contents than the

first (AHBS-1) and third (AHBS-3) beds.

Due to the high ash yield is marked by the relatively abundant supply of detrital

materials. The sample taken from the Lithostratigraphic section of the Sombo-Genji

stream Northern parts of the study area two sample taken from the first Coal bed in

lateral variation East to West the Western part is low ash content (SGS-14) the second

lowest ash contents in all sample analyzed and the Eastern (SGS-12) part is high. The

Coal ash content provides used as an indicator of the heating value of the Coal.

Low Coal ash content shows a high heating value of the Coal which in general

indicates low emissions, hence is very suitable for industrial

Nevertheless, high Coal ash content shows the direct opposite not for suitable.

As a result, the Achibo

applications, particularly in cement production.

However, to intention that

Achibo quarry site, Hada Bekela,Debeso stream, and Sombo section coal ash has to

be investigated, extremely. According to (Kim et al.,

influence on the heat pass to the sur

ash content observed in this study area are suitable and adequate. Coal with higher ash

or splits indicates development in proximity to active marine or no marine siliciclastic

depositional environments (

Figure 32.Fixed Carbon and Ash content comparison trend of Achibo

56


indicates low emissions, hence is very suitable for industrial


As a result, the Achibo-Sombo Coal ashes were shown to be sufficient for industrial

applications, particularly in cement production.

However, to intention that ash can be used to, the recital of the cement containing


tremely. According to (Kim et al.,2001) ash has a significant

influence on the heat pass to the surface of the fuel. The values of volatile matter and



depositional environments (McCabe, 1984).

Fixed Carbon and Ash content comparison trend of Achibo


indicates low emissions, hence is very suitable for industrial application.


Sombo Coal ashes were shown to be sufficient for industrial

ash can be used to, the recital of the cement containing


2001) ash has a significant

face of the fuel. The values of volatile matter and



Fixed Carbon and Ash content comparison trend of Achibo-Sombo Coal

Table 3.The sample analyzed result of moisture, volatile matter, fixed carbon and ash

contents

Sample

S/N Sample Id

1 WJBH-1

2 WMBH-1

3 ABH-2

4 SHBH-2

5 AQS-1

6 AQS-2

7 AQS-3

8 AQS-4

9 AHBS-1

10 AHBS-2

11 AHBS-3

12 ADS-1

13 DAS-2

14 SGS-12

15 SGS-14

Average

Figure 33.Graphic representation of proximate analysis

57

.The sample analyzed result of moisture, volatile matter, fixed carbon and ash

Proximate analysis

Moisture% Volatile Matter% Fixed Carbon %

5.38 21.27 6.29

7.30 23.57 13.50

10.24 34.03 23.67

8.39 29.71 19.01

30.27 36.26 33.23

24.04 28.95 24.90

23.64 29.19 25.11

12.00 37.29 31.88

22.77 27.94 25.92

30.12 32.10 30.77

24.08 31.27 24.02

29.09 30.61 27.84

8.69 30.31 22.89

27.07 29.09 26.69

29.72 34.94 31.07

19.52 30.44 24.45

Graphic representation of proximate analysis by line chart

.The sample analyzed result of moisture, volatile matter, fixed carbon and ash

Fixed Carbon % Ash %

67.05

55.63

32.06

42.90

0.25

22.11

22.06

18.83

23.36

7.01

20.64

12.46

38.10

17.16

4.27

25.59

Figure 34.Graphic representation of proximate analysis by column chart

4.4.5. Sulfur Distribution

For assessing coal quality, sulfur is the main element because a high amount of sulfur

is a risk for technological applications and environmental impact. Sulfur is the crucial

relevant factor in assessing the c

of the study area from core sample very low < 0.02% (SHBH

the outcrop sample from Northeastern of the study a

coal seam one, 1.90% (AQS

Southwestern, and Western parts are the lowest sulfur contents than the all outcrop

sample except (WMBH

The sulfur distribution in Achibo q

one to seam three,(AQS

bed thickness but coal seam number four is high sulfur content than the second an

third bed.

58

Graphic representation of proximate analysis by column chart

4.4.5. Sulfur Distribution


technological applications and environmental impact. Sulfur is the crucial

levant factor in assessing the coal quality. The sample collected from Southwestern

of the study area from core sample very low < 0.02% (SHBH-2) ranges to high ranges

sample from Northeastern of the study area Achibo quarry site section

oal seam one, 1.90% (AQS-1). All samples taken from the borehole Eastern,


ample except (WMBH-1) (Table 4).

The sulfur distribution in Achibo quarry site section in terms of coal seam from seam

one to seam three,(AQS-1),(AQS-2), and (AQS-3), are decrease respect to the c

oal seam number four is high sulfur content than the second an

Graphic representation of proximate analysis by column chart


technological applications and environmental impact. Sulfur is the crucial

oal quality. The sample collected from Southwestern

2) ranges to high ranges

rea Achibo quarry site section

1). All samples taken from the borehole Eastern,


oal seam from seam

), are decrease respect to the coal

oal seam number four is high sulfur content than the second and

59

But sulfur contents of the Hada Bekela stream section is directly proportional with the

coal bed thickness means of increased from coal seam one to coal seam three (AHBS-

1.AHBS-2, and AHBS-3). The utmost variation in the sulfur contents in terms of coal

bed is probably the changes in the sulfide contents in the coal bed. The variation of

the sulfur contents in the Coal seam is due to sedimentary evolution and interbeded

sediments. According to (Chou, 1997 and Liu et al., 2007), the abundance of sulfur

distribution in coals is associated with the depositional environment of coal seams.

The outcrop sample collected from the Debeso Lithostratigraphic section coal bed no

1 (ADS-1, 1.18%) is identical sulfur contents with the Achibo-quarry site section of

Coal bed no 4 (AQS-4, 1.18%) (Table4.2). The sulfur analyzed from the Northern

parts of the study area Sombo Lithostratigraphic section of Genji stream coal bed no1

(SGS-12, 0.58%) is the same as the Achibo quarry site section coal bed no 2 (AQS-2,

0.58%). The sulfur analyzed in the Eastern parts Dawe Abote stream section (DAS-2,

0.74 %) is relatively high than the Sombo-Genji stream of the Western section (SGS-

14, 0.67 %). The sulfur distributions of study area were laterally increased from West

to East towards NE parts.

According to Chou (2012) based on the percentage of sulfur content coals have been

classified into three types namely; low sulfur (< 1% sulfur contents)(SHBH-2,ABH-

2,WJBH-1,AQS-3,AQS-2,SGS-12,SGS-14,DAS-2,WMBH-1, and AHBS-1),medium

sulfur ( > 1% to < 3% sulfur content) (AHBS-2,AQS-4,ADS-1,AQS-1,and AHBS-3

),and high sulfur coals ( > 3% sulfur content ) depend on the sample analyzed, ten

samples are belongs to low and five samples are medium sulfur contents. From the

analyzed samples no samples were categorized under high sulfur contents, and then

the Achibo-Sombo coal is categorized belongs to low and medium sulfur contents.

60

Table 4.Sulfur (%) and Calorific value (Btu/lb) analysis result

S/N Sample ID Sulfur% Calorific value Btu/lb

1 WJBH-1 0.45 2323.044

2 WMBH-1 0.79 3306.798

3 ABH-2 0.29 6489.09

4 SHBH-2 <0.02 5091.678

5 AQS-1 1.90 9166.23

6 AQS-2 0.58 7578.162

7 AQS-3 0.57 7628.724

8 AQS-4 1.18 9378.684

9 AHBS-1 0.93 7296.678

10 AHBS-2 1.13 7673.364

11 ABS-3 1.21 6887.556

12 ADS-1 1.18 7385.31

13 DAS-2 0.74 5845.986

14 SGS-12 0.58 6915.726

15 SGS-14 0.67 8374.86

Figure 36.Graphic representation of sulfur distribution by line chart

Figure 35.Graphic representation of sulfur

61

Graphic representation of sulfur distribution by line chart

Graphic representation of sulfur increment in Achibo-Sombo by column chart

Graphic representation of sulfur distribution by line chart

Sombo by column chart

62

Coals of the Study area formation in all borehole samples WJBH-1, WMBH-1, ABH-

2, and SHBH-2 samples do not show any significant variations in their sulfur contents

and as mentioned earlier are considered as low-sulfur coals. The low sulfur contents

in the Sombo (SGS-12 and SGS-14) a coal seam and relatively low proportions of

pyritic sulfur suggest a proper freshwater environment during the deposition of the

peat of the Sombo coal. From the moderate amount of organic sulfur present in the

Achibo quarry site (AQS-1, AQS-2, AQS-3, and AQS-4) and Hada Bekela stream

(AHBS-1, AHBS-2, and AHBS-3) coal seam, it can be inferred that the parent plant

debris included a moderate amount of sulfur.

The Western, SW and Northern coals are fairly low sulfur Coals used extensively as

gas Coal and also as smithing and steam coal. The Northeast except; Achibo quarry

site section (coal bed 2 and 3), Hada Bekela stream section (coal bed 1 ), and East

coal stream section excluding the Dawe Abote stream section of the coal bed found in

those Lithostratigraphic sections are medium sulfur contents used for domestic and

steam purposes. Generally, the sulfur contents of the study area are very low to

moderate in the percentage used for industrial applications.

4.4.6 Calorific Value

The calorific values determine the heat potential of coal; usually expressed in Btu per

pound. It is the attribute of Coal-based on its chemical composition and moisture

content. The great important fuel attribute is its calorific or heat value (Aina et al.,

2009). This indicates the amount of heat released per unit of mass of combusted coal

and is of great importance in setting the coast of particular coals for combustion

applications.

The calorific value of sample taken in the study area the core sample collected from

the borehole sample Id (WJBH-1, WMBH-1, ABH-2, and SHBH-2) as well as the

outcrop sample from the stratigraphic section ranges from 2323.044 ( WJBH-1) to

9378.684 (AQS-4) in Btu/lb (Table 4). From the four borehole samples, the calorific

value of the core sample analyzed from the Eastern 6489.09 Btu/lb (ABH-2) is higher

than the (SHBH-2, WMBH-1, and WJBH-1), SW and Western parts respectively

(Table 4).

The eleven (11) outcrop sample from the quarry site and stream section Northern,

and Eastern parts, from the quarry site section coal bed n

in the NE is the higher calorif

the Northern parts stream sample, Sombo Genji section two samples were taken both

sides East and West of stream sides from this West side is higher calorific value

8374.86 Btu/lb ( SGS

the Eastern parts of the study area, stratigraphic section of Achibo Debeso stream

section Coal bed no1 calorific value is 7385.31 Btu/lb (ADS

Abote stream section Coal seam n

calorific value of Coal analyzed in the Northeastern parts Achibo quarry site and

Hada Bekela stream sections, its different heat value from bed to bed vertically in the

downside sample Id (AQS

(AQS-2) is less than the first bed because of the inorganic impurities also the sample

Id (AHBS-1),(AHBS-2), and (AHBS

Table 4) heat value for reason that altered of

Figure 37.Graphic representation of calorific value increment by column chart

63

The eleven (11) outcrop sample from the quarry site and stream section Northern,

and Eastern parts, from the quarry site section coal bed no 4 (AQS-

is the higher calorific value from all sample analyzed in all study area. In



8374.86 Btu/lb ( SGS-14 ) than the Eastern 6915.726 Btu/lb ( SGS


1 calorific value is 7385.31 Btu/lb (ADS-1) greater than Dawe

Abote stream section Coal seam no 2 which is 5845.986 Btu/lb (DAS



downside sample Id (AQS-1),(AQS-2),(AQS-3), and (AQS-4) the

2) is less than the first bed because of the inorganic impurities also the sample

2), and (AHBS-3) from this section Coal bed n

) heat value for reason that altered of mineral matter.

Graphic representation of calorific value increment by column chart

The eleven (11) outcrop sample from the quarry site and stream section Northern, NE

-4) 9378.684 Btu/lb

ic value from all sample analyzed in all study area. In



astern 6915.726 Btu/lb ( SGS-12) parts. From


1) greater than Dawe

45.986 Btu/lb (DAS-2). The



4) the coal bed no 2

2) is less than the first bed because of the inorganic impurities also the sample

3) from this section Coal bed no 3 is the least (

Graphic representation of calorific value increment by column chart

Figure 38.Graphic representation comparison of volatile matter versus fixed carbon

Figure 39. Graphic representation of ash versus moisture content by line chart

64

Graphic representation comparison of volatile matter versus fixed carbon

Graphic representation of ash versus moisture content by line chart

Graphic representation comparison of volatile matter versus fixed carbon

Graphic representation of ash versus moisture content by line chart

65

CHAPTER FIVE

5. DISCUSSION

5.1 Depositional Environment

The sedimentary strata of the study area were largely found between the basement

complex and alluvial sediment, Basement complex and Upper Basalt (figure 26 and

27). The sedimentary layers found within these rock units vary in vertical thickness

with lateral extension. The relative thickness difference of coal seams and different

sedimentary strata in the study area is commonly large.

From lithostratigraphic (section 4.3) the presence and thickness of coal seams,

Siltstone, and Sandstone Shale represent the optimization of flood plain and swamp

deposits. Parallel laminated Oil Shale (figure 19 to 25) indicated that the sediments

were deposited in floodplain environments with the habitual variation of current

energy conditions. The thin dark Mudstone connected with Coal seams (figure 26,

BH-5) indicated deposition by vertical accretion in back swamp environments. The

Mudstone was may deposit in floodplain ponds, lakes, and weakly developed

paleosols.The vertical and lateral evolutions of these environments show existence

water body dry and wet. During these different times, different strata were formed.

From the Borehole data (figure 26 and 27) shows, that the lower beds of the

sedimentary strata is greatly composed of different Shale and rarely by Claystone.

The coal seams are exist concentrated at the between a part of the sedimentary strata.

Some of these strata show gradational change from one rock unit to the other. This

gradation change of the stratigraphic unit is occasionally observed between Mudstone

and Claystone and between Carbonaceous Shale and Oil shale and between Siltstone

and Sandstone, and vertical sequence in lateral extension. The sedimentary rocks

deposited in the study area were represented fluvial and lacustrine environments.

5.1.1. Fluvial Deposits

The change of lithology from course to fining upward from Sandstone to Siltstones,

like (BH-7) and Mudstone to moreover channeling is reliable with fluvial deposit.

66

The sedimentary rocks existence of Mudstone, Sandstone, and Coal beds present in

the Western parts, (Witate section), NE, and E parts of the study area were interpreted

as fluviatile deposits. The presence of Sandstone from the lithostratigraphy of BH-3,

BH-5, and BH-7 is probably deposited by the river. The other deposits exist ordinarily

in a group of Mudstone, Sandstone, and coal lenses, observed in the section of the

Northeastern and Southeast of the study area by channel and overbank conditions.

Depend on nature and lithological association depositional environment of the study

area coal-bearing strata can be interpreted to represent braided river sediments

(lithostratigraphic section of Hada Bekela and Achibo quarry site). The thin beds of

Mudstone (figure 26 and 27), BH-5, BH-10 andBH-18, the assemblage of Coal lenses,

are developed on the top of the bars. Thin laminated, finer Sandstone beds are formed

due to waning flow. The habitual occurrences of the fine sediments with Coal

stringers, as a whole indicate the presence of repeated periods of overflows. It is

known that Coal seams in the active braided plain regime are commonly thin and

laterally limited, due to a fast-shifting and short-lived over bank settings (Collinson,

1996).

From the ( figure 26 and 27 ), BH-5, BH-10 and BH-18 the layering of Mudstone

intercalated with Coals are deposits as vertical accretion in reducing energy flood

basins then marshes distal from the active channel. According to Bustin and Palsgrove

(1997), well-preserved plant fossils with thinly laminated Mudstone explain slow

deposition from suspension.

The thin fine to medium sand sediments distributed in Achibo, Hada Bekela and

Sombo section streams are indicated of an isolated crevasse splay.The cross

lamination in this section are represents weak strength of the stream thickness express

a short period of deposition. The indication of thin beds of Coal is the sign of a high

water table in the depression of the distal flood plain.

According to Hughes and Lewis (1982) Most of the sediment carried out onto the

floodplain is suspended load that will be mainly Clay- and Silt-sized debris but may

include fine sand if the flow is rapid enough to carry sand in suspension. As water

leaves the confinement of the channel it spreads out and loses velocity very quickly.

67

5.1.2. Lacustrine Deposits

The distribution of Oil shale (figure 19 to 25) in all sections of the study area and

different lithology coal-bearing strata are indicated lacustrine depositional

environments. The mixtures of siliciclastic sediments with organogenic and chemical

sediments consist of the lacustrine successions. The study area were mainly controlled

by Carbonaceous shale, gray Siltstones, coal seams and Sandstones.The horizontal

lamination and massive sedimentary structures composed of plant fossil and rare

animal fossils. According to (Wolela, 2010), the coastal lake environment is

conducive to the growth of plant material and subsequent development of peat and

Coal.

As shown from the lithostratigraphic section of (figure 19 to 25 ), the presence of

Carbonaceous shale, Oil shale, and Coally shale are indicated the manifestation of a

lacustrine environment. The formation of some coal seams and Coally shale more

input of plant fragments to the coastal area is required. Specifically of laminated Oil

shale beds are characteristic of higher depth. The occurring pattern of Mudstone

indicates continuous filling of the lake by the siltation process to form lenses of mud.

The presence of plant fossils like roots, leaves and stems at the study area founded in

Oil shale beds is the sign of plant drift to the lake.

Generally, the lacustrine environments of this area are validation by, cyclic deposition

of sediments and by frequent sedimentary structures, such as lamination and fissility

in shale. This lake estate of sedimentation is also confirmed by the types of flora and

some faunal found in the sediments.

5.2. Quality Interpretation of Coal

The Coal deposit existed around study area is highly exposed along the NE

(Stratigraphic section of Achibo, Hada Bekela, and Sombo section), moderately

exposed along with E (Debeso and Dawe section), at the W and SW it is deposited

underground (from borehole data), while it is rare along the SE and central parts of

the study area with different quality having varies in thickness intercalated with other

sedimentary strata (Figure 19 to 24). The Coal has distinct in thickness, color from

bed to bed, and section to the section.

68

The various sedimentary structures as though seam splitting; cleat, lamination, and

bedding existing. The presence of some structures likes seam splitting and cleats

observed from the stream section of the study area have their own effects on the

quality of coal deposited. The splitting of the coal seam is due to delta collapsing,

clastic material like; Sand and Silt sediments based on the depositional condition of

Coal deposited environments. The presence of cleats in Coal influences the

production of Coal bed and occurrences of coal due to openings of gaseous molecules

through the cleats (volatile matter, moisture, and sulfates) are escaping and filling the

secondary minerals such as clay, pyrite, and calcite may affect the quality of coals.

The coal founded along the NE parts of the stratigraphy section is relatively more

acceptable quality than the other section. Particularly Achibo quarry site section and

Sombo section are better quality than other sections with characteristics of sub-

conchoidal fracture during hammered and better shinning when compared to the other

section of these indications of increasing rank coals.

5.2.1. Grade

Coal grade is an economic or technological classification of the relative quality of a

Coal for a particular use and a variety of grades of coal are defined for different uses

or markets in different industries and countries, and for the needs of a particular

process (https://www.uky.edu/KGS/coal/coal-grade.php). Coal grade is refers to

inorganic composition in coal, like ash and sulfur content in coal is change an

economic classification of the relative quality of a coal for particular use. The

calorific value of coal is one of the primary measure coal values as a fuel for reason

that it is directly affected by mineral matter.

The grade of coals is defined for variety uses based on quality grades. The coal which

contains low ash and low sulfur are used for steam coal. The grades of steam coal are

related to sulfur content with ash yield. The word low sulfur coal is used for coals

with below one percent of sulfur. The higher amount of ash contents reduces the

amount of calorific value of coal.

AccordingtoGovernment of India Ministry of coal (http://www.coal.nic.in/point4.html.co

al Grades) the ash content is important parameter to determine the coal price as coals

purity and efficiency greatly depend on ash content.

69

Table 5.Coal Grade

General specification grades of cocking Coal Based on

Government of India Ministry of Coal

Sample Id which found

in this standard ranges

Grade Ash

Steel Grade-I Not-exceeding 15% AQS-1,SGS-14,AHBS-

2,ADS-1

Steel Grade-II Exceeding 15% but not Exceeding 18% SGS-12

Washery Grade-I Exceeding 18%but not Exceeding 21% AQS-4,AHBS-3

Washery Grade-II Exceeding 21% but not Exceeding 24% AQS-2,AQS-3,AHBS-1

Washery Grade-III Exceeding 24% but not Exceeding 28% _

Washery Grade-IV Exceeding 28% but not Exceeding 35% ABH-2

The Coal analyzed of the studied area has a different grading scale from the steel

grade-I to washery grade-IV. The steel grade Coal which has not exceeded 15% ash

content contains the Achibo section (AQS-1), Hada Bekela stream section (AHBS-2),

Achibo Debeso section (ADS-1), and Sombo section (SGS-14). The Eastern parts of

the Sombo section (SGS-12) contain ash contents between 15% - 18% categorized

under Steel Grade-II. The sample ash percentage ranges (18%-21%) (AQS-4, AHBS-

3), grouped to the Washery Grade-I, the sample collected from Achibo section Coal

bed no 2 and 3 (AQS-2, AQS-3) and Hada Bekela section coal bed no 1 (AHBS-1)

are ash contents between 21% -24% are grouped to Washery Grade-II Coal.

The core sample collected from the borehole in the study area all ash contents are

above the standard (Table 3) except sample Id (ABH-2) is categorized under Washery

Grade-IV Coal. Also, the Dawe section coal sampled is greater than the standard

given in the table above.

70

The proximate analysis and calorific value of the samples collected from Achibo

quarry site and Hada Bekela stratigraphic section shows that it is sub-bituminous C to

lignite A in rank and various in grade from bed to bed; steel Grade I ( AQS-1, SGS-

14, AHBS-2), steel Grade II ( SGS-1 2), washery Grade I (AQS-4, AHBS-3) and

washery Grade II ( AQS-2, AQS-3, AHBS-1) (Table 5 and 6 ).

The coal-bearing sediments present along the Eastern parts found by making

horizontal bed have better thickness particularly the Dawe section (Figure 19)

relatively Debeso Lithostratigraphic section (Figure 20) while unusual condition

thickness with the quality, the Dawe section is high thick from the stream section but

less quality it is categorized lignite B in rank. It is a relatively lower rank than the

Debeso section (Lignite A) (Table 6) in the same orientation. The Coal deposited

along W and SW is high in thickness from (borehole data) while the lowest rank in

the study area is grouped under lignite B rank and grade even below to the

classification used because of great amount of ash contents.

Some of the sample analyses results are showed unusual conditions, such as high

fixed carbon content with low calorific value ( sample Id: AQS-1 with AQS-4, AQS-3

with AHBS-1 ). The unusual and irrelevant analysis results of those particular Coal

samples as a result of their composition. These particular Coal samples probably have

high proportions of inorganic components, such as clastic material, sulfides, and silica

in the form of intercalations, concretions, and nodules, which are syn or post-

depositional inclusions. The presence of these inorganic components in those

particular Coal samples may increase the content of ash above the normally expected

limit and have been the cause for unusual fixed carbon content and calorific value.

Generally, the Coal quality of NE and E of the study area is high quality than NW, W,

SW, and S parts. Particularly Achibo quarry site section, Sombo section, and Hada

Bekela section are more suitable for economic uses than the other section of the study

area.

5.2.2. Rank

The rank of the coal has combined the result of the function of heat, pressure, and

time; the rank determination depends on several parameters and no single parameter is

workable through concentrated coal rank range.

71

The vitrinite reflectance measurement is a great use in the determination of coal rank

independent on the chemical composition of the coal. Nevertheless, this measure is

cannot be reliable for low-rank coals due to the low metamorphic grade (O’Keefe et

al., 2013). Accordingly, calorific value and moisture contents are commonly used as

an alternative to the parameters in the rank determination for low-rank coals.

The total moisture of the Achibo quarry site section (average, 22.48% on dry basis)

and Hada Bekela section (average, 25.65% on dry basis), Debeso section (average,

29.09% on dry basis), and Dawe section (average, 8.69% on dry basis) part sample of

Northeastern and Eastern parts coal deposits cannot be considered equal to bed

moisture through possible loss of water during coal transport from one bed to the

other bed of strata. Consequently loss of water during sample transport from the

sampling site is possible, even though the studied samples were collected from the

borehole and outcrop in possibility place. According to (Taylor et al., 1998) for rank

determination, the volatile matter content is the main parameter important, mainly in

the low-rank coal. For the combustion purposes, the Sombo and Achibo quarry

section is the low sulfur and ash content relative to the other and then a good applicant

for a clean coal combustion feedstock.

The Ethiopian coal and Oil shale are mostly found interbeded with the Cenozoic

volcanic of the Ethiopian plateau. According to Dai (2012) volcanic ashes may well

mix with coal itself and thus, could lower the quality of the coal if it is not possible to

remove them in the preparation plant The ash content can be amended with selected

mining if wanted as the contributors of ash in Achibo coal is the Claystone of

volcanic origin (tonsteins).The low sulfur and low ash content coal used for the

potential raw material for industrial application.

According to Wolela (2008) the Ethiopian coal ranks fall under the soft coal series

(lignite to bituminous coal), and genetically classified under humic, sapropelic, and

mixed coals .The values of volatile matter and ash content observed in the study are

good and acceptable.

A significant factor in determining coal quality is coal rank. The ranks of coal (from

high to low carbon content) are as follows: anthracite, bituminous , sub-bituminous,

and lignite respectively. As you move along the coal rank the heat is given out

reduces and the dryness of the fuel and moisture content becomes lagers.

72

In the low-rank coal, the volatile matter is a purpose measure because it reflects the

hydrogen and carbon contents of the coal and is an indicator of rank. Moisture

contents have been used as a rank indicator in lignite and sub-bituminous coals.

Instead of low-rank coals, moisture is a crucial factor because the Coal needs to be

transported, handled, and stored, and the existence of moisture in large amounts will

obstruct these operations and guide to greater costs. Moisture is also replacing an

equal amount of burn material and thus reduces the heating value, there by

complicating the combustion process.

According to the ASTM (American Society for Testing and Materials) classifications

(D 388-1999) is used on a worldwide basis this is based on two coal properties, the

fixed carbon values and the calorific values (on d.m.m.f.basis). According to ASTM

(D388-1999) if gross calorific value (Btu/lb) between 8,300 to 9,500Btu/lb grouped

sub-bituminous “C” , 6,300 to 8,300Btu/lb lignite “A” ,< 6,300 Btu/lb lignite “B”.

The Coal in the study area was belongs to the lower rank Coal classifier depend on the

gross calorific value (Table 4 ).The Coal analyzed in the study area the results is no

Coal which has a greater calorific value higher than 9378.684 Btu/lb that leads to

classifying depend on their Calorific value, based on this scheme the rank of Coal in

all section of the studied area ranges from lowest energy value (2323.044, 3306.798,

and 5091.678, 5845.986 Btu/lb) the core sample from western and Southwestern

borehole and Dawe section, categorized under lignite B respectively. The Coal sample

collected from the quarry site section and stream from bed to bed some varied in rank.

From the Achibo-quarry site section, the first and fourth Coal seams have low-rank

Coal sub-bituminous C while the second and third beds were classified as lignite

A.The Coal sample taken from the Hada Bekela stream section all belongs to lignite

A.The Coal collected from the lithostratigraphy of the Sombo Genji section was high-

rank coals next to the Achibo-Sombo section relative to the other sections; it was

classified into sub-bituminous C and lignite A.

73

Table 6.Rank classification based on ASTM (D388-1999)

S/N

Sample Id

Calorificvalue

(Btu/lb,(m.m .m.f.b)

Rank

Agglomerating character

1 WJBH-1 2323.044 Lignite B Non agglomerating

2 WMBH-1 3306.798 Lignite B Non agglomerating

3 ABH-2 6489.09 Lignite A Non agglomerating

4 SHBH-2 5091.678 Lignite B Non agglomerating

5 AQS-1 9166.23 Sub bituminous C Non agglomerating

6 AQS-2 7578.162 Lignite A Non agglomerating

7 AQS-3 7628.724 Lignite A Non agglomerating

8 AQS-4 9378.684 Sub bituminous C Non agglomerating

9 AHBS-1 7296.678 Lignite A Non agglomerating



12 ADS-1 7385.31 Lignite A Non agglomerating

13 DAS-2 5845.986 Lignite B Non agglomerating

14 SGS-12 6915.726 Lignite A Non agglomerating

15 SGS-14 8374.86 Sub bituminous C Non agglomerating

Generally, the laboratory result analyzed samples in the study area indicates the

Coals have medium to high moisture content, volatile matter, and ash content, and

low sulfur with few samples are medium sulfur, relatively low fixed carbon content.

The majority of the Coal samples fall within lignite “A” to lignite “B”; some are sub

bituminous “C” ranks and none agglomerating. Comparatively, the calorific value of

Coal Btu/lb from Achibo, Hada Bekela, and Sombo Genji section are greater than that

of Dawe Abote stream section in the Eastern parts, and Witate in the Western side.

The Coal with the highest calorific value is the best and cleanest type of coal to use.

Generally, the Achibo quarry site section Coal bed no1 and 4, and Sombo section

Coal bed no1 sample Id ( SGS-14) are higher ranks from the study area classified

under sub-bituminous C in steel Grade I for ( AQS-1 and SGS-14) and washery Grade

II for ( AQS-4. The studied Coal sample categorize Lignite B, Lignite A, and sub-

bituminous C with steel Grade I and II, washery Grade I, washery Grade II and IV),

(Table 5 and Table 6 ).

74

Figure 40.Rank and Grade correlation of lithostratigraphic column of each stream

section.

Hint: SG- I = steel Grade I, WG-I=Washery Grade I, SG-II=Washery Grade II

5.3. Comparison within Yayu coal deposits

The different of the Coal seams are deposits throughout in the Geba Basin with the

specific locality and varieties in physical, chemical, quality parameters, depositional

environments, and other characteristics. The Achibo –Sombo Coal deposit is which

have high amount tones of Coal in different in quality parameter like, moisture

content, volatile matter, Fixed carbon, ash, calorific value, and sulfur situate in the

Geba basin.

75

As compared the Achibo-Sombo Coals based on the quality characteristics within the

other specific locality found in the Geba Basin reported from Geological Survey of

Ethiopia (2001),(Appendix I; A, B, C,and D) with the present study ( Table 3, and

4),selected some representative sample ( Table 7).

The Achibo-Sombo has higher moisture content than the Yayu, Sheno, Witate and

Dawe, but Dawe and Witate are relatively the equivalent in the moisture contents. The

volatile matter of Witate and Achibo-Sombo is higher than the Dawe, Sheno and

Yayu.

Achibo-Sombo and Witate are relatively the same in the volatile matter even though

Yayu is the very low in volatile matter compared with the other localities of Coal

within Yayu. Achibo-Sombo coal is higher fixed carbon than the other in Geba Basin

next to the Witate Coal deposits, while Yayu and Sheno Coals are very low than

Witate by volatile matter, but Dawe Coal is intermediate.

In the case of ash contents, Dawe coal is higher than the Yayu, Sheno, Witate and

Achibo-Sombo, but in contrast, the ash contents of Coal in Achibo-Sombo is very low

particularly from this paper (Table 3, and 4) sample picked from Achibo Coal seam

No 1 (AQS-1) and from Sombo section from Coal seam No1 (SGS-14) are very low

in ash contents compared with the other Coal deposit in the Geba Basin.

The Achibo-Sombo coal is very low in the sulfur contents than Sheno, Witate, Yayu

and Dawe Coal deposits, but Sheno and Witate are very higher sulfur contents than

the other (Table 7), and Yayu sulfur content is intermediate. The calorific value of

Witate and Achibo –Sombo are relatively very high than Sheno, Dawe and Yayu. The

calorific value of Yayu and Dawe are very low than Sheno Coal. The calorific values

of the Coal samples have no systematic trend (Table 4). However, some coal seams

with high calorific value are located in the upper section of coal seams.

Generally, the Achibo-Sombo coal has very low in the sulfur and ash contents than all

localities of coal deposit within Yayu, but relatively high in moisture contents. The

Achibo-Sombo and Witate are similar in volatile matter, fixed carbon and calorific

value and higher than the other Coal deposits within Geba Basin. Based on the above

mentioned the Achibo-Sombo and Witate Coals are more suitable for economical.

Table 7.Proximate, Calorific value and Sulfur analysis results from GSE

report (2001), Picked from ( Appendix I). Proximate and sulfur (%), CV (Kcal/Kg),

and ABH-2, AQS-1, and SGS

Spl. No Depth interval (m)

W3-8 158.27-158.57

W3-18 177.11-177.41

Y2-1 150.6-151.01

Y2-8 166.28-166.58

Shl-14 442.38-442.68

Shl-20 444.38-444.76

D01-9 99.51-99.92

D01-17 117.82-118.21

ABH-2 (144m)

AQS-1 Out crop(1.7m)

SGS-14 Out crop (4m)

Note: Spl=sample, W=Witate, Y=Yayu, Sh=Sheno, D=Dawe,

ABH=Achibo Bore hole, AQS=Achibo quarry site seam 1,

SGS=Sombo Genji steram seam 1 Sample

Figure 41.Graphic Representation of proximate value comparison trend of Geba Basin

Coal deposits. 76

Proximate, Calorific value and Sulfur analysis results from GSE


1, and SGS-14 are selected from the present study.

Depth interval (m) Moisture Volatile

matter

Fixed carbon Ash

158.57 10.4 38.7 33.5 17.4

177.41 5.5 34.5 32.1 27.9

151.01 20.5 19.3 17.3 42.9

166.58 25.7 24.4 27.5 22.5

442.68 20.0 29.7 30.2 20.0

444.76 18.6 25.6 23.2 32.6

4.5 25.4 17.0 53.1

118.21 11.6 31.3 33.7 33.4

10.24 34.03 23.67 32.06

Out crop(1.7m) 30.27 36.26 33.23 0.25

Out crop (4m) 29.72 34.94 31.07 4.27

Spl=sample, W=Witate, Y=Yayu, Sh=Sheno, D=Dawe,


SGS=Sombo Genji steram seam 1 Sample no 4

Graphic Representation of proximate value comparison trend of Geba Basin

Proximate, Calorific value and Sulfur analysis results from GSE unpublished


14 are selected from the present study.

Ash Calorific

value

Sulfur

17.4 5014 3.5

27.9 4900 2.4

42.9 1894 2.8

22.5 3350 2.7

20.0 4015 3.2

32.6 2975 3.2

53.1 2272 2.2

33.4 4341 1.2

32.06 3605.05 0.29

0.25 5092.35 1.90

4.27 4652.70 0.67

Spl=sample, W=Witate, Y=Yayu, Sh=Sheno, D=Dawe,


Graphic Representation of proximate value comparison trend of Geba Basin

Figure 42.Calorific value increment comparison trend of Geba Basin coal deposit

5.4. Comparison with the Corresponding Coal deposit in Ethiopia

Coal deposits in Ethiopia found through NW (Chilga Basin

Yayu Basin, Lalo-Sapo Basin, Gojeb

Ethiopia (Mush Valley and Wuchale area) by varieties of chemical, physical, and

Figure 43.Graphic representation of sulfur value increment comparison trend

of the Geba Basin coal deposit.

77

Calorific value increment comparison trend of Geba Basin coal deposit


Coal deposits in Ethiopia found through NW (Chilga Basin), SW (Delbi

Sapo Basin, Gojeb-Chida Basin, Nejo Basin) and, central of


Graphic representation of sulfur value increment comparison trend

of the Geba Basin coal deposit.

Calorific value increment comparison trend of Geba Basin coal deposit


), SW (Delbi-Moye Basin,

Chida Basin, Nejo Basin) and, central of


Graphic representation of sulfur value increment comparison trend

78

depositional characteristics. This varieties are own role in the uses plus commercial

path.To make the comparative value of the Achibo-Sombo coal with the other

deposits of this valuable resource compared with the other place of Ethiopian Coal

deposits (Appendix II),(Table 8),(Figure 44 and 45) with discussed in the same unit

of measurement. For this comparison moisture, FC, CV, Sulfur and ash are preferred

since those are the main importance to identify the Coal for utilization and direct

effect on the Coal.The chosen results of Coal deposits are the good results to mostly

main emphasis on their relevance and higher status. Achibo-Sombo Coal has higher

fixed carbon than Mush valley and Lalo- sapo but lower than Delbi Moye, Chilga,

Yayu, Wuchale and Gojeb Chida however, relatively equivalent with Nejo Coal

deposit. The ash value of Achibo- Sombo Coal is the very low than all Ethiopian

Coal, particularly from the Achibo quarry site section (AQS-1) and from Sombo

section (SGS-1), (Table 3) are compared with the other Ethiopian Coal (Appendix II),

but from the one core sample (WJBH-1) analyzed from Western parts of the study

area is higher than the other Ethiopian Coal deposits. The calorific value of Achibo-

Sombo Coal is higher than the other Ethiopian Coal deposit next to Gojeb-Chida and

Delbi Moye, that means Yayu, Lalo-Sapo, Chilga, Wuchale, Mush valley, and Nejo

are lower in calorific value than Achibo-Sombo Coal deposit. Even so, the calorific

value of Achibo –Sombo is relatively similar to Yayu and Gojeb-chida Coal deposit

(Table 8). The Achibo-Sombo Volatile matter and moisture contents are relatively

higher than the other Ethiopian Coals, but volatile matter is lower than the Yayu

Coals.

The sulfur content of Achibo- Sombo Coal is very low than other Ethiopian Coals

except Gojeb chida. However, from in this paper (Table 4) sample analyzed from

Southwestern of the study area core sample Id (SHBH-2) is closer to extinct the sulfur

contents which compared with the Gojeb Chida, then when compared with sulfur

contents of Achibo –Sombo Coal deposits it is very lower than the other Ethiopian

Coal deposits.

Even though, the sulfur contents of Wuchale, and Delbi Moye Coal deposits are

higher than the Yayu, Mush valley and Nejo Coal deposits, but Chilga and Lalo-Sapo

are relatively the same (Table 6).

79

The key out comes in this study as the value of sulfur content is rise, the quality of

the Coal is fall and rise the environmental problem. Therefore the Achibo-Sombo

Coal has lower in sulfur content than the other Ethiopian Coals; it is the vital for

economic uses.

Table 8.Laboratory analysis of Ethiopian Coal deposits results (%), Calorific value in

cal/g comparison.

Location Exact

Locality

Moist

ure

Volatile

Matter

Fixed

Carbon Ash

Calorific

value Sulfur

Delbi - Moye

BH-18

(70.2m) 1.5 26.2 56.9 16.9 6900 2.1

BH-10 (132m) 1.8 25.9 37.5 36.9 5030 1.3

Yayu

BH7-2

(123.6m) 16.72 40.89 34.8 24.3 4724 1.93

BH8-1 (146m) 6.98 43.03 39.18 17.79 4350.4 1.83

Mush Valley Mush valley

outcrop 22.4 34.1 23.9 19.6 3658 1.2

Nejo Achacha

outcrop 5.4 36.2 28.2 30.2 3530 1.2

Wuchale Totito outcrop 1.4 18 35.2 45.4 3710 2.6

Chilga BH-31

(54.8m) 10.7 22.6 40.1 26.6 4007.2 0.8

Gojeb - Chida Outcrop

(1.2m) 7.7 29 32.3 31 5480 0.3

Lalo-Sapo Waro outcrop 12 18.2 11.5 58.3 4015 0.6

Achibo-Sombo

ABH-2

(144m) 10.24 34.03 23.67 32.06 3605.05 0.29

Achibo

outcrop

(0.6m)

12.00 37.29 31.88 18.83 5210.38 1.18

Sombo

outcrop (4m) 29.72 34.94 31.07 4.27 4652.70 0.67

Note: Achibo-Sombo is the present study findings while the remaining

data were obtained from (Wolela, 2007)

80

Figure 44.Ash, Fixed carbon, and Sulfur comparison trend of Ethiopian coals

Figure 45.Calorific value comparison trend of Ethiopia coals increments by column

charts.

Figure 46.Sulfur value comparison trend of Ethiopian coals increments by line chart

81

value comparison trend of Ethiopia coals increments by column

Sulfur value comparison trend of Ethiopian coals increments by line chart

value comparison trend of Ethiopia coals increments by column

Sulfur value comparison trend of Ethiopian coals increments by line chart

82

5.5. Economic significance of the Achibo-Sombo coal

The main goal of the Coal quality assessment is to decrease dependency on imported

energy sources like natural gas and oil. A total of about 297,000,000 tons of coal

reserve registered in the country, the Achibo –Sombo Coal deposit is hosting the first

biggest lignite to sub-bituminous (around 200,000,000 tons) in Ethiopia (Wolela.A,

2008). Even so, the proximate, sulfur, and calorific value analyses from the borehole

and all stratigraphic section of the study area verify the low quality (medium to high

ash content, low calorific values, low and medium sulfur contents). Consequently, any

Coal deposit capable of coking Coal production might be helpful to reducing imports.

Nevertheless, the studied Coals display low rank and fixed carbon contents and high

volatile matter contents. Furthermore, the high ash and medium sulfur content, the

presence of mineralogical composition (like. pyrite, clay minerals, carbonates) could

behold problematic for these processes due to possible corrosion, slagging and

irregular heating (Collot,2006, Wagner,2008).

The Ethiopian demand is covered by Coal from certain fields and imports for different

applications such as domestic heating, cement manufacturing, electricity generation,

coking, gasification, etc. Therefore the Achibo Sombo Coal deposit will be attractive

for local people and our country.

Coal is a bountiful resource which is important for a long time to produce energy in

the form of heat and electricity by converting into having value of the three states

liquid, solid, and gaseous products. The greatest general and economic uses of Coal

are in that heat is generated to produce steam, which in change the turbines which

produce electricity.

Since Coal varies in economic importance, particularly the ash and sulfur values are

usual considerations in most the real deal for any coal usage. According to

(Mukherejee and Borthakur,2003), the supervise of high sulfur Coals produces sulfur

dioxide which guides to acid rain ( environmental effect) and corrosion of boilers,

pipelines, and other machineries. Also high the amount of sulfur in Coal is unsuitable

for different uses of Coal. In steel manufacturing, the low sulfur content in Coal is

used for cooking.

83

According to Thomas (1992) the sulfur contents of Coals less than 0.8% are used for

to make coke for steel (WJBH-1,WMBH-1,ABH-1,SHBH-2, AQS-1,AQS-2,AQS-

3,DAS-2,SGS-12,SGS-14) specifically are falls under this uses. As Speight (2012) the

Coal ranks under bituminous, sub-bituminous, and lignite are used for fuel in steam

electric power generation (AQS-4, AQS-1,SGS-14,AQS-2, AQS-3, AHBS-1, AHBS-

2,AHBS-3,SGS-12,ADS-1, ABH-1) the first three samples are under sub-bituminous

C and the respective samples are Lignite A ranks may suitable for this application.

The high amount of ash content in Coal is may pose an ecological and environmental

problem. The high ash content produced from the Coal during an industrial

application may affect some of the combustion processes. Coals with high ash yield

are not preferred, as a large feed rate is needed to generate the same amount of energy

(Mastalerz et al., 2008). While an increase in ash content seriously affects the

combustion in fixed bed or stoker boilers, it hardly affects the degree of combustion

in pulverized burners and circulating fluidized bed combustors (Chatenet, 1965). A

higher amount of ash content reduces the calorific value of Coal, causes health and

environmental damages, and lowers the boiler efficiency.

Thus ash content is an important parameter to determine the coal price as coal’s purity

and efficiency greatly depend on ash content(.http://www.coal.nic.in/point4.html.Coal

Grades). Coal ash reflects a variety of mineral contained; some of them might be used

for industrial interest. Usage of coal fly ash in cement production is the most common

application (Liyanage et al., 2014 and Yao et al., 2015). The ash contents varied

significantly from section to the section which the coal is extracted from the quarry

site section and Hada Bekela stream section also other section which found in the

study area and less significant from core sample analyzed.

A higher amount of moisture content in the coal is to reduce the gasifier temperature

and consequently the rate of conversion of carbon during gasification (Schobert,

1995). The moisture limit is to ensure acceptable pneumatic conveying characteristics

of coal (Yun et al., 2008). High-moisture Coals are commonly in low-rank Coals that

are low calorific value. The high moisture content decreases the calorific value; it

increases the consumption of Coal for heating and lengthens the time of heating.

84

The importance of moisture contents in Coals are reduced transportation costs while

increases combustion efficiency, safety, and reduces the amount of exhaust gas, allow

the air pass from the bed, and sprayed in the oven to save from the fusion. Total

moisture is important in assessing and controlling the commercial processing of coals.

In coking processes, Coals with a great amount of moisture content is require more

heat for vaporization of the moisture, which leads to longer coking cycles and reduces

production.

The moisture contents of Coal in the study area are range from 5.38 % to 30.27%

therefore, it is usable for economic commercial of coals. The Coal samples were taken

from stratigraphic section of NE and E parts of the study area a relatively high amount

of moisture contents than the W and SW. The high moisture content is May due to the

distribution of surface water and forest coverage study area.

The amount of volatile matter in Coal reduces with increasing Coal rank. Volatile

matter is clearly related to Coal rank; as rank increases, volatile matter content

decreases (Stach and others, 1982). The volatile matter is to decrease the calorific

value of Coal. It has an inverse trend of fixed carbon with rank. Higher volatile matter

in coals is used because it is evolved as gas instantaneously, leaving behind a small

amount of char with higher porosity (Mastalerz et al., 2008). The volatile matter of

Coal samples analyzed from core samples are less than the stream and quarry site

samples except (ABH-2) which is found in Eastern parts of the study area. Another

hand the volatile matter of NE and E parts are greater than the amount of W and SW

stratigraphic section of the study area. According to ( Miller,2005) in the steel

industry the high amount of volatile Coals with medium-volatile and/or low-volatile

Coals to advance the strength of the coke ( AQS-4,,AQS-1,SGS-14,ABH-2,AHBS-

2,ADS-1,DAS-2,AHBS-3AQS-3,SGS-12, SHBH-2, AHBS-1,AQS-2 ,WMBH-1 ,and

WJBH-1 ) .

85

CHAPTER SIX

6. CONCLUSION AND RECOMENDATION

6.1 .Conclusion

Based on the current study it was concluded that, the stratigraphy of the study area has

different lithologies that differ in their thickness both in their lateral as well as vertical

extent. This is due to variation in depositional environment and geological

configuration of the basin. The sedimentary nature of the study area is sandwiched

between lower Basalt and the alluvial sediments. It is consists of upper Basalt, Oil

Shales, Sandstones, Carbonaceous shale, coal seams, Siltstones, Clay stones, Mud

stones and Shale which revealed different thicknesses both in vertical and lateral

extent. The laboratory proximate analyzed results indicated that, the moisture, volatile

matter, fixed carbon, and ash contents value range from 5.38 to 30.27 %, 21.27 to

37.29%, 6.29 to 33.23%, and 0.25 to 67.05% respectively. The calorific values and

sulfur content analyzed samples are ranged from 2323.044 to 9378.684 Btu/lb and

<0.02 to 1.90% respectively. From this it was concluded that, the Coal has low and

high quality based on calorific value and sulfur content, respectively. The majority of

Coal samples fall within lignite “A”, four samples is lignite “B” and three samples are

sub-bituminous “C” ranks and non-agglomerating. Thus, it was concluded that the

general quality assessment of coal samples taken from Western, SW borehole and

Dawe section is less for economic utilization as compared to the Ethiopian coal of

Wuchale, Lalo-Sapo, and Nejo. However, the Coal samples which were taken from

the stratigraphic section of Debeso, Achibo quarry site, Hada Bekela, and Sombo with

a significant thickness have good quality and can be used for economic utilization.

86

6.2. Recommendation

From the stratigraphy, proximate, calorific value and sulfur analysis of the coals, the

main and fundamental recommendations are drawn which are helpful for the

exploration, industrial application, and sustainability of the Achibo Sombo coal

deposits, SW Ethiopia. The stratigraphic log and correlations are based on physical

properties, the average thickness and depth of the coal-bearing strata as exposed on

the surface, and some borehole data. In order to be sure about the coal seam

continuous in the subsurface and change in the quality, different and detailed

exploration is required particularly in the NE and E parts of the study area. The

proximate, calorific value, and sulfur analysis of exposed coal and some core samples

were studied in this paper. However, due to the time and cost limitation, this analysis

was not cover a few aspects. Thus, XRD analysis in order to know the mineralogical

composition of coal for farther constructive information of the Achibo- sombo coal

quality is recommended.

87

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94

Appendix I

Proximate, Calorific value and sulfur analysis results from GSE unpublished report

(2001), Proximate and sulfur (%), CV (Kcal/Kg)

A) Wittete Bore hole No 3

Spl.No Depth interval ,m moisture Volatile

matter

Fixed

carbon

Ash Calorific

value

Sulfur

W3-1 147.1-147.40 7.9 36.9 34.0 21.3 4662 0.9

W3-2 147.40-147.60 9.8 29.7 29.3 31.2 3948 0.6

W3-3 147.72-148.02 12 36.3 30.8 20.9 5046 0.8

W3-4 152.65-152.95 13.7 29.1 25.8 31.4 3473 1.1

W3-5 152.95-153.25 7.6 34.3 32.1 26.0 4455 1.2

W3-6 153.25-153.55 9.4 31.1 29.8 29.6 3787 1.1

W3-7 153.55-153.83 5.4 34 36.7 23.9 4600 1.1

W3-8 158.27-158.57 10.4 38.7 33.5 17.4 5014 3.5

W3-9 158.57-158.87 10.4 35.8 32.8 21 4583 2.2

W3-10 158,87-159.22 7.1 25.2 20.2 47.5 2700 1.9

W3-11 160.45-160.75 3.6 34.4 31.6 30.3 4270 3.3

W3-12 160.75-161.05 2.3 27.8 21.8 48.1 2720 3.9

W3-13 167.11-167.44 13.0 37.8 38.6 10.7 5259 1.0

W3-14 169.07-169.38 11.1 37 35.2 16.8 5007 1.5

W3-5 Duplicate 7.6 35.3 31 26,2 - -

W3-6 Duplicate 9.4 31.3 29.6 29.7 37.93 1.1

W3-14 Duplicate 11.1 37.1 35 16.8 4964 1.2

W3-15 176.16-176.51 13.7 37.1 36.8 11.9 4904 1.5

W3-16 176.51-176.81 11.5 30.2 24.8 33.5 3474 1.5

W3-17 176.81-177.11 9.9 28,2 23.9 38 3170 1.9

W3-18 177.11-177.41 5.5 34.5 32.1 27.9 4900 2.4

W3-22 Duplicate 14.9 34.9 38.2 12 4924 0.7

W3-28 Duplicate 2.4 29.2 24.6 43.8 3436 1.9

95

B) Yayu Borehole No2

Spl.No Depth

interval,m

moisture Volatile

matter

Fixed

carbon

Ash Calorific

value

Sulfur

Y2-1 150.6-151.01 20.5 19.3 17.3 42.9 1894 2.8

Y2-2 156.07-156.27 21.3 24.6 22.8 31.4 2966 3.7

Y2-3 161.26-161.64 24.4 22.6 21.3 31.7 2521 1.6

Y2-4 161.64-161.94 25.6 24.8 26.4 23.3 3040 1.3

Y2-5 161.94-162.26 23.3 22.9 25,7 28.1 2969 1.9

Y2-6 162.73-163.19 25.2 23.3 27 24.5 3283 1.7

Y2-7 163.33-163.62 24 19.3 21.7 35.1 2163 1.9

Y2-8 166.28-166.58 25.7 24.4 27.5 22.5 3350 2.7

Y2-9 166.58-166.88 29.6 26.7 33.5 10.3 3996 2.7

Y2-10 166.88-167.06 23.3 20 23.3 35.4 2465 2.8

C) Sheno Bore hole No 1

Spl.No Depth interval,m moistur

e

Volatile

matter

Fixed

carbon

Ash Calorifi

c value

Sulfur

Shl-1 394.94-395.24 16.7 20.9 17.5 44.9 1911 1.9

Shl-2 395.24-395.54 14.0 16.2 9.2 60.6 1018 0,7

Shl-3 396.20-396.5 14.7 16.2 11.2 58.0 1215 0.9

Shl-4 396.50-396.80 16.0 16.3 10.5 57.2 1053 0.8

Shl-5 434.35-434.65 20.9 28.1 28.5 22.5 3810 2.6

Shl-6 434.65-434.85 21.4 26.0 27.2 25.3 3460 0.8

Shl-7 438.08.438.38 18.2 27.1 25.9 28.9 3320 1.8

Shl-8 438.38-438.68 20.5 29.5 30.0 20.0 4020 0.8

Shl-9 438.68-438.98 21.0 29.7 31.0 18.3 4090 0.9

Shl-10 438.98-439.28 17.0 21.2 28.0 33.5 3360 0.9

Shl-11 439.28-439.58 19.0 25.7 24.8 30.5 3090 0.9

Shl-12 439.58-439.88 17.4 21.7 18.6 42.6 2130 1.8

Shl-13 439.88-440.36 16.7 21.4 18.3 43.6 1970 2.1

Shl-14 442.38-442.68 20.0 29.7 30.2 20.0 4015 3.2

Shl-15 442.68-443.00 19.2 29.4 29.4 22.0 4020 2.1

Shl-16 443.00-443.30 15.2 20.0 15.6 49.3 1516 1.5

Shl-17 443.30-443.60 15.2 17.7 45.9 21.2 4800 1.2

Shl-89 443.60-444.00 15.1 21.0 14.3 49.6 1516 1.3

Shl-19 444.00-444,38 16.8 27.7 24.8 30.7 3444 3.0

96

Shl-20 444.38-444.76 18.6 25.6 23.2 32.6 2975 3.2

Shl-21 448.70-449.00 17.3 23.3 20.5 38.8 2463 2.8

Shl-22 449.00-449.30 17.3 23.5 21.0 38.3 2422 1.7

Shl-23 449.30-449.60 17.4 22.2 19.2 41.2 2260 1.2

Shl-24 449.60-449.90 15.2 14.4 18.3 42.2 2200 1.6

Shl-25 449.90-450.20 15.1 20.4 17.2 47.4 2200 1.7

Shl-26 450.20-450.50 19.2 23.3 22.7 34.8 2920 0.8

Shl-27 451.31-451.62 18.5 27.1 24.4 30.1 3470 1.4

Shl-28 453.16-453.60 25.3 29.8 35.6 9.3 4850 0.6

Shl-29 455.30-455.82 18.9 23.5 21.6 36.0 2655 0.7

D) Dawe bore hole N0.01

Spl.No Depth interval,m moisture Volatile

matter

Fixed

carbon

Ash Calorific

value

Sulfur

D01-1 93.35-93.65 20.6 30.1 26.5 22.9 3970 1.2

D01-2 93.65-93.95 22.9 28.9 24.8 21.5 3910 1.4

D01-3 93.95-94.25 22.7 30.6 29.1 17.6 4240 1.3

D01-4 94.25-94.74 20.8 21.8 19.4 38.0 2255 1.7

D01-5 96.60-96.90 15.0 18.9 13.8 52.3 1452 1.0

D01-6 96.90-97.20 20.4 27.7 28.3 23.8 3832 1.9

D01-7 97.20-97.50 14.1 18.3 10.0 57.7 1140 1.1

D01-8 97.50-98.00 18 22.5 19.0 40.7 2170 1.4

D01-9 99.51-99.92 4.5 25.4 17.0 53.1 2272 2.2

D01-10 100.28-100.58 5.6 28.0 19.4 47.0 2815 1.6

D01-11 100.58-100.88 6.7 23.9 17.7 51.8 2177 1.2

D01-12 100.88-101.34 12 23.3 20.1 44.8 2546 1.2

D01-13 114.14-114.57 8.7 5.4 23.3 22.5 2540 1.8

D01-14 116.3-117.03 8.5 3.0 23.4 65.2 3080 1.0

D01-15 117.03-117.46 5.3 31.1 27.6 36.0 3555 1.4

D01-16 117.46-117.82 8.5 30.0 30.3 31.2 3971 1.2

D01-17 117.82-118.21 11.6 31.3 33.7 33.4 4341 1.2

D01-18 120.30-120.70 10.9 26.3 23.8 39 2935 2.3

97

Appendix II

Coal Analysis result of Ethiopian Coals (Wolela.A, 2007)

Locality

Depth

(m

Thickne

ss (m)

Moist

ure

%

VM

%

Ash

%

FC

%

CV

cal/g

Sulfur

%

VR

(%)

Delbi

Moye

BH-18

40.75

0.65

2.3

18.9 52.6 29.1 3689 1.4

0.34

-

0.64

70.2 1.8

1.5

26.2

16.9

56.9

6900

2.1

117.4

0.65

1.5

22.2

28.5

49.3

5730

1.3

BH-19

30

0.6

2.7

28.5

27.4

49.9

5741

1.6

40

1.8

2.7

26.3

35.6

38.2

5040

0.4

81

1.05

3

24.9

42

33.2

4393

0.3

102

1.1

0.3

25.6

27.1

47

5780

0.3

BH-21

6

1 2.5 21.3 21.3 36.4 5080 1.7

79.85 2 0.3 17.9 39.9 42.2 4880 0.3

142 1.2 1.2 21.5 18.3 60.2 6900 0.3

147 1.3 1.5 21.4 24.9 54.2 6276 0.3

162.3 0.55 1.3 20.7 20.5 58.8 6743 0.3

BH-10

132 1.1 1.8 25.9 36.9 37.5 5030 1.3

BH-11 133.8 1 3.9 30.9 27.9 38.3 5622 0.6

BH-2 50.55 1.35 5.4 28.6 38.6 27.6 4300 0.4

59.7 2 5.6 32 15 47.4 6165 0.4

BH-1 93.85 2.2 2.3 36.5 13.9 47.3 6100 0.6

Yayu BH2-1 90.8 1.54 8.09 44.98 16.85 30.17 5788.9 1.65 0.3-

98

95.15 1.41 6.45 43.44 14.46 42.1 5604.9 1.85 0.4

BH3-1 53.5 1.55 21.1 45.15 15.46 39.39 56.23 1.41

58.4 1.35 15.88 41.57 15.94 42.49 5444.6 1.82

62.25 1.6 11.06 43.99 18.65 54.07 5099 1.56

102.35 0.6 18.53 42.46 18.34 39.2 5423.1 1.41

108.35 1.33 18.81 42 16.18 41.82 5418.3 1.86

111.64 2.8 8.9 40.27 18.57 41.16 5199 1.56

BH6-1 77.85 0.94 8.17 43.96 14.96 41.12 5618.6 1.12

82.7 1.91 12.41 48.7 15.61 35.69 5263.3 1.92

87.85 2.4 13.18 46.51 15.75 37.74 5649 1.99

BH7-2 112.5 0.72 26.31 44.51 14.66 40.83 5649 1.21

119.1 1.95 20.65 42.02 16.02 41.96 5430.2 2.07

123.6 2.79 16.72 40.89 24.3 34.8 4724 1.93

BH8-1 140.65 0.82 16.79 45.54 12.97 41.49 5806.7 1.48

146 1.52 6.98 43.03 17.79 39.18 4350.4 1.83

149.85 2.19 16.41 40.12 19.07 40.81 5280.1 1.29

BH10-1 78.35 2.1 10.98 46.53 11.32 42.15 5930.8 1.45

83 1.87 23.96 44.4 11.68 43.92 5811.7 2.33

86.9 1.27 12.14 37.97 25.01 37.02 4822.4 2.39

Mush

valley

Mush

valley

Out

crop

1.75 1.6 27.4 33.1 37.9 4390 1.2 0.34

-

0.46 22.4 34.1 19.6 - 3658.6 -

18.7 39.2 16.3 25.8 3656.2 1

1 20.3 35.1 18.8 25.8 3764.4 0.8

Nejo

Machakani Out

crop

6.1 38.7 16.7 38.5 4470 0.8

0.36

-

0.47

Aleltu 8.1 44.7 5.3 41.9 4990 0.9

Achacha 5.4 36.2 30.2 28.2 3530 1.2

Wuchale

Totito Out

crop

0.5 1.4 18 45.4 35.2 3710 2.6

0.3-

0.48 11.33 21.37 44 46.7 4516 1.8

0.4 12.32 29.71 22.64 48.72 5761 1.25

Chilga

BH-31 34.75 0.7 7 19.2 46.5 27 2430 0.6

0.34

-

BH-30 45.95 0.95 8.6 17 36.2 38.2 3465 0.8

53.2 0.7 9.3 21.1 39.4 37.2 2649 1

54.8 0.65 10.7 22.6 26.6 40.1 4007.2 0.8

22.5 0.35 10 22.8 24 43.2 4188.7 1.2

BH-34 54.5 0.8 8.2 20 43.7 28.1 2925 0.6

99

59.45 0.45 8.6 22.3 38 33.1 3548 0.6 0.54

23.2 0.8 6.9 11.5 54 20.6 2840.2 0.8

BH-27 28.3 0.4 7.1 21.2 31.3 30.4 3740 0.5

65.35 0.65 6.6 31.8 16.6 45.2 4599.5 0.4

70.4 0.85 13.2 15.8 49.8 21.2 2531.5 0.5

Gojeb

chida

3km south

of Gojeb

river

bridge

Out

crop

1 13 31 20 38.7 4800 0.6

0.3-

0.54

Out

crop

1.2 11 5.2 51.8 22.8 2490 0.2

Out

crop

0.4 10.7 32.2 18.9 38.2 4740 0.5

Out

crop

0.7 18.5 27.9 13.6 39 4740 0.4

Lalo-Sapo

Bokai

stream

Out

crop

1.2 7.7 29 31 32.3 5480 0.3

Waro

stream

Out

crop

2 13.4 32.4 20.9 33.1 4120 0.4

0.3-

0.64 Geta

stream

Out

crop

1 12 18.2 58.3 11.5 4015 0.6

0.7 9.1 20.5 52.4 18.1 2626 0.5

stratigraphy and of coal at achibo

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