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Development and Testing of an Improved Fish Smoking Kiln

by

A. A. Fagge, Lawal A.O*. and Andefiki. T**

*National Agricultural Extension & Research liaison Services

**Dept. Of Agricultural Engineering

Ahmadu Bello University, Zaria

faggeaa@gmail.com

Keywords: Improved Smoking Kiln, Consumption rate, temperature andThermal efficiency

Abstract

An improved smoking Kiln was constructed using a 2mm gauge mild steel for thecabinet, and the combustion units, a galvanise iron pipe was used for heatdistribution. Heat generated from a burning charcoal enters the smoking chamberthrough the perforated pipes. The kiln maintained a relatively uniform temperatureof 600C at all the trays inside the chamber and smoke an ice fish satisfactorily within4 hours. The fuel consumption rate was 1.25kghr-1 and the thermal efficiencyobtained was 93.6%.

Introduction

Fish constitutes about 41% of the total animal protein intakeby the average Nigerian hence there is great demand for fishin the country. Nigeria requires about 2.66 million metrictons of fish annually to satisfy the dietary requirement ofits citizens (160 Million) (ATA, 2011)

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Fish harvesting, handling, processing and distribution providelivelihood for millions of people and also providing foreignexchange earning to many countries (Al-Jufaili and Opera,2006)

According to Akinneye et al. (2007) and Davies and Davies(2009) the development of appropriate fishing machinery andtechniques that ensure effective production, handling,processing and storage cannot be over emphasized especiallynow that acqua-cultural development is gaining popularity inNigeria. Generally, there is abundant fish catch in the dryseason. During this period, ponds, lakes and streams and otherwater bodies experience reduced water level which makes foreasy harvest and subsequent scarcity of fish during flood andraining seasons ( Eyo, 1997). It is imperative to process andpreserve some of the fish caught in this period of abundance,so as to guarantee a sustainable supply of fish during offseason and increased profit potentials of the fisher-folks(Davies and Davies, 2009). High post harvest losses oftenoccurs as a result of poor handling and inefficient smokingkilns which is associated with or characterized by long timeprocessing, where most fish got spoiled before they wereprocessed. Poor preservation greatly reduced the quality andquantity of the products with the existing traditionaltechniques. According to Tawari (2006) and Davies and Davies,(2009) to improve the quality of fish and fishery products,traditional processing technology must be improved upon inNigeria,

Akinola et al. (2006) described a number of preservationmethods such as drying, smoking, freezing, chilling andbrining. The most prominent fish preservation method inNigeria is smoke drying. This could be adduced to the factthat most of the fish communities have no access toelectricity or large cold rooms to freeze their products.Appropriate processing of fish enables maximal use of rawmaterial and production of value-added products which is

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obviously the basis of processing profitability (Ito, 2005;Davies and Davies, 2009).

Even though various traditional methods are employed topreserve and process fish for consumption and storage inNigeria, smoking is the most widely practiced method. Manyspecies of fish available in the country can be smoked and ithas been estimated that 70-80% of the domestic marine andfreshwater catch are consumed in smoked form.The use of traditional ovens such as rectangular mud oven,cylindrical mud oven and cylindrical metal oven (drum) werethe major methods of smoking fish by women using fire woodwith which many problems are encountered.

Material and Method

The factors considered in the design and fabrication of theImproved fish smoking kiln were: air flow system, heatdistribution system, spacing, smoking (drying) temperature,total weight of products, ease of loading and unloading,vapour condensation, hygiene and durability of materials used.

A mild steel was used for the construction of the dryingchamber and the combustion chamber, while a galvanizeperforated iron pipe was used for heat distribution throughthe drying chamber in order to prevent corrosion of thematerial. Plates 1.1 and 1.2 shows the front view and backview of the fabricated Kiln

The drying chamber consists of two trays (layers) made frommild steel and its rectangular in shape with overalldimensions of 50cm X 40cm X 80cm. A chimney was provided atthe top of the chamber for moisture migration to preventvapourized moisture condensation on the products duringsmoking process.

A radial flow fan (blower) powered by either AC or DC motorsupplies ambient air from the surrounding to the burner(combustion chamber) containing the desired quantity ofcharcoal.

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Heat from this combustion chamber is distributed by forcedconvection to the product on the trays through the perforatedpipes (hot air vent). Moisture removed from the fish escape tothe atmosphere through the chimney to provide quick drying ofthe product in the cabinet.

The oven has a capacity of about 8.0 ̶ 16.0 kg of fish perbatch, the oven is easy to manipulate in terms of function.There is provision for adjusting the trays depend on the sizesof the fish to be smoked

Plate 1.1 Front view of the fabricated fish smoking kiln

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Plate 1.2 Back view of the fabricated fish smoking kiln

RESULTS AND DISCUSSIONS

A sample of fresh fish was bought and cured. The curingprocess of the fish was as follows;

(a) The freshfish obtained from market were gutted and the gills andintestines removed. They were then washed with clean water.

(b) The fishwere then soaked in a solution of salt for about 10 minutes.This retards bacterial action and aids dehydrationprocesses.

(c) The fish were then loaded into the smoking chamber readyfor smoking.

(d) Heat was supplied to the kiln by forced convection from a fan blowing air through the combustion chamber, into the perforated heat distribution pipes.

Results of performance test using AC to power the blower

The table 1.1 below shows the weight of fish on each layer(tray), oven temperature and relative humidity during thesmoking (drying) period.

Table 1. Performance test of the Kiln

S/N

Timeoftheday Oven

Weight offish (kg)

Change inweight Relati

ve

(Pm)tempt.˚C

of fish (kg) humidity %

Layer1

Layer2

Layer1

Layer2

1 12:00 33 1.1 1.1 0 0 802 12:10 35 1.07 1.08 0.04 0.03 803 12:20 37 1.04 1.05 0.03 0.03 804 12:30 38.5 1.02 1.03 0.02 0.02 805 12:40 40 1.01 1.02 0.01 0.01 80

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6 12:50 42 1 1.01 0.01 0.01 807 1:00 41 0.98 0.99 0.02 0.02 808 1:10 43 0.96 0.97 0.02 0.02 809 1:20 45 0.94 0.94 0.02 0.03 8010 1:30 47 0.91 0.92 0.03 0.02 8011 1:40 48 0.88 0.89 0.03 0.03 8012 1:50 49.5 0.86 0.87 0.03 0.02 8013 2:00 51 0.81 0.82 0.05 0.05 8014 2:10 53 0.76 0.77 0.06 0.05 8015 2:20 55 0.7 0.71 0.06 0.06 8016 2:30 56 0.68 0.69 0.02 0.02 8017 2:40 57 0.64 0.65 0.04 0.04 8018 2:50 59 0.58 0.59 0.06 0.06 8019 3:00 58 0.54 0.52 0.04 0.05 8020 3:10 60 0.49 0.49 0.05 0.03 6521 3:20 60 0.46 0.47 0.03 0.02 6522 3:30 59.5 0.43 0.44 0.03 0.03 6523 3:40 60 0.41 0.42 0.02 0.02 5724 3:50 59 0.4 0.4 0.01 0.01 5725 4:00 60 0.4 0.4 0.01 0.01 57

0

10

20

30

40

50

60

70

Oven tempt. ˚C

Time (min)

Temp

erat

ure

˚C

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Figure 1.1 Graph of temperature against time of the

Kiln

Figure 1.1 shows the relation of change in temperature withrespect to the period of smoking fish. The oven temperatureincreased progressively as from the start time till after 3hours when the oven temperature remained stable at 60˚C.

Figure 1.2 graph of fish weight against time.

Figure. 1.2 shows the change in weight of fish between thelayers (trays) during smoking period. The loss in weight onboth layers indicates that there was a progressive drying ofthe fish within the smoking chamber of the kiln.

The two graphs indicated the relation between the temperature,time and loss in weight of fish. The relative humidity in thedrying chamber changes from 80% initially to 57%.

The heat generated can be calculated by the followingexpression;

12:0012:3001:0001:3002:0002:3003:0003:3004:00

0

0.2

0.4

0.6

0.8

1

1.2

Weight of fish (kg) Layer 1Weight of fish (kg) Layer 2

Time (min)

Weig

ht

of

fi

sh

˚C

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Calorific value of charcoal = 7600kj/kg (Rogers et al ,1987)

Total processing time = 4 hours

4 hours ( 4×60×60) = 14400 seconds

Mass of charcoal used (burnt) = 5.0kg

Heat generated by burning 5.0 kg of charcoal will be = 7600×5 = 38000 kJ

Therefore the heat generated in kilo joules per hour will be =heatgeneratedbythecharcoal

processingtime = 380004

= 9500 kJ / hr

Heat dissipated by the charcoal box

Q =KA(t1−t2)x

Where;

K = thermal conductivity of mild steel 45.5 W/mk

A = area of the charcoal box 1.2 m2

T1 = temperature of the charcoal in the combustion chamber

T2 = temperature of outside wall of the combustion chamber

X = thickness of the mild steel 3.0mm = 0.003m

Therefore, Q =45.5×1.2×(260−190)0.003

Q = 1092000 watts

But, 1watt =1 J/hr

Therefore, heat dissipated by charcoal box = QProcessingtime

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= 12740004

= 318000 Joules per hour

Amount of heat dissipated = heat dissipated × area

= 318500 × 1.2

= 382200 Joules per hour

= 382200/1000

= 382.2 kJ/ hr

The total heat dissipated = heat dissipated by the kilnsmoking chamber + heat dissipated by the charcoal box

Total heated dissipated = 225.26 + 382.2

= 607.64 kJ / hr

Thermal efficiency of the kiln

The fuel efficiency of the kiln can be calculated as

Useful heat = heat generated - total heat dissipated

= (9500 ̶ 607.64) kJ/hr

= 8892.36kJ / hr

Therefore, thermal efficiency =usefulheatoutput (

kjhr

)

heatgenerated(kjhr )

× 100

Fuel efficiency = 889.239500 × 100 = 93.6%

Fuel Consumption rate

This determined the rate at which fuel (charcoal) is used up.

Fuel consumption rate = amount(mass)ofcharcoalused(kg)processingtime(hour )

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5.0kg4hour =1.25 kg/hr

Therefore the fuel consumption rate = 1.25kg/ hr

Conclusions

An improved fish smoking kiln was designed and fabricated.Performance evaluation gave a thermal efficiency of 93.6%. Thekiln attained an internal temperature of 60˚C after about 3hours and maintained it afterwards. The fish from each layerreduced from 1.10kg to 0.4kg after smoke - drying for fourhours. The smoked fish was neat and uniform in colour. Thekiln is not limited to fish smoking alone; meat and similarproducts can also be dried using the kiln.

REFERENCES

Agricultural Transformation agenda Document (ATA). (2011). Federal Ministry of Agriculture and Rural Development, Nigeria

Akinneye, J.O., Amoo, I.A. and Arannilewa, S.T. (2007).Effect of drying methods on the nutritionalcomposition of three species of fish (Bonga sp, Sardinella spand Heterotis niloticus). Journal of Fisheries International,2(1):99-103.

Akinola, O.A., Akinyemi, A.A. and Bolaji, B.O. (2006).Evaluation of Traditional and solar drying systems towardsenhancing fish storage and preservation in Nigeria (AbeokutaLocal Government as a case study) Journal of FisheriesInternational 1(2-4): 44-49.

Al-Jufaili, M.S. and Opara, L.U. (2006). Status of fisheriesPost harvest Industry in the Sultanate of Oman: Part 1Handling and Marketing System of Fresh Fish. Journal ofFisheries International, 1(2-4): 144 -149.b

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Clucas, I. J. and Sctcliffe, P.J. (1987). An introduction tofish handling and processing. Report of the Tropical ProductsInstitute, pp 143-186.

Delgade, C. L., Wada, M.W.N., Rosegrant, S.M. and Ahmed, M.(2003). Fish for 2020: Supplyand demand in changing globalmarkets. International Food Policy Reseach Institute,Washington, D.C. and World Fish Centre, Penanng, Malaysia.

Davies, R.M. (2006). Mechanization of fish industry in Nigeriastatus and potential for selfsufficiencyin fish production. Apaper presented at a one-day workshop on intensive fishfarming. 19th August, 2006. 10pp.Davies, R.M. and Davies, O.A. (2009). Traditional and ImprovedFish Processing Technologies in Bayelsa State,Nigeria.European Journal of Scientific Research, 26(4): pp. 539-548.

Eyo, A.A. (1997). Post-harvest losses in the fisheries ofKainji Lake. A consultancy report submitted to Nigerian/German(GTZ) Kanji lake fisheries promotion project, March 1995,75pp.

FAO. (1995). TCDC in fish smoking. In Learning fromexperience. Rome.

Khoshmanesh, S. (2006). Design of Solar Dehydrator, Coupledwith Energy Storage in Rock Bed Reservoir for Fish DryingProcess. International Conference

Tawari, C.C. (2006). Effectiveness of Agricultural agencies infisheries management and production in the Niger Delta. Doctorof Philosophy (Ph.D) thesis, Rivers State University ofScience and Technology, Port Harcourt, Nigeria(Unpublished).180pp

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Figure 3. Orthographic View of the Fish Smoking Kiln