Project Proposal for an Iron Ore Pelletizing Plant

Individual Assignment

Mineral Engineering II

R. M. Azoor

100860K

Department of Earth Resources Engineering

University of Moratuwa

Contents

1 Introduction .......................................................................................................................................... 3

2 The Iron Ore Pelletizing Process ........................................................................................................... 4

3 Flow Sheet for the Pelletizing Process .................................................................................................. 5

4 Production Quantities ........................................................................................................................... 6

5 Suggested Machines ............................................................................................................................. 7

5.1 Crushing and Grinding Circuit ....................................................................................................... 7

5.2 Pelletizing Machine ....................................................................................................................... 8

6 Cost ....................................................................................................................................................... 9

6.1 Capital ........................................................................................................................................... 9

6.2 Operating Cost .............................................................................................................................. 9

7 Environmental Considerations ............................................................................................................ 10

List of Figures

Figure 1: Fired Pellets .................................................................................................................................... 3

Figure 2 : Crushing Circuit ............................................................................................................................. 7

Figure 3: Pellet Mill ....................................................................................................................................... 8

Figure 4 : Dust reduction by watering ........................................................................................................ 10

1 Introduction

Raw iron ore is ground and formed into pellets to be fed into the blast furnace as raw material. These

pellets are spherical in shape and are of 1 to 2 cm in diameter. These pellets are porous and allow for a

better air flow and heat distribution through the pellet, resulting in a better reduction into iron in the

blast furnace. For this reason, pellets are preferred over fine powder as blast furnace feed.

The preparation of iron ore pellets begins with the crushing and grinding of iron ore into a fine powder,

and adding reducing additive coke (C) and binding agents and mixing. The mixture is added to a

pelletizing machine or ball mill along with a pre determined amount of moisture to form green pellets.

These green pellets are air dried and subsequently oven dried to harden the pellets. Green pellets are

fired in a furnace to produce fired pellets which are ready to be used in a blast furnace.

This brief report concerns with the prerequisites, requirements and the logistics in establishing a new

pelletizing plant of a given output. This report outlines the pelletizing process, the cost involved in

establishing and operating the plant and also logistical matters. Other details such as waste disposal,

emissions and environmental considerations are also dealt with very briefly.

Figure 1: Fired Pellets

2 The Iron Ore Pelletizing Process

The required amount of Hematite Iron ore is taken from the stockpiles and fed into the primary crusher.

The output from the primary crusher is sieved and the undersize is fed into the secondary crusher while

the oversize is fed back into the primary crusher.

The output of the secondary crusher is fed in a similar manner after a sieving process into a rod mill for

further size reduction.

The rod mill discharge is also sieved and fed into a ball mill for powdering.

The resultant powder is sieved by a 180 or 250 micron sieve and mixed with coke (carbon) of the same

size similarly prepared by crushing grinding and milling and sieving. Portland cement is also added to the

mixture. The amount of these additives added are 5% of the mass of the iron ore.

The mixture is mixed thoroughly inside a ball mill and transferred to a pelletizing machine. Once in the

pelletizing machine, a level of moisture of approximately 9% is introduced by spraying water into the

mixture.

This will result in the formation of iron ore pellets.

Once the pellets have reached the required size, they are removed and left to air dry for about a day.

Then the hardened pellets are oven dried to completely remove the moisture in them.

Finally the dried pellets are fired in a furnace to prepare the fired iron ore pellets.

3 Flow Sheet for the Pelletizing Process

(-)

Iron Ore (Hematite)

Primary Crusher

Sieve - 5-10 cm

Secondary Crusher

Sieve - 0.5-2 cm

Rod Mill

Sieve - 300µm

TEMA Disk mill

Sieve - 180/250µm

Pelletizing

Green Pellets

Air Drying - 2 days

Oven Drying - 110C

Furnace - 1000C

Fired Pellets

Primary Crusher

Sieve - 5-10 cm

Secondary Crusher

Sieve - 0.5-2 cm

Rod Mill

Sieve - 300µm

TEMA Disk mill

Sieve - 180/250µm

Coke (C)

Cement

Spray Water - 9%

(-)

(-)

(-)

(+)

(+)

(+)

(+) (-)

(-)

(-)

(-)

(+)

(+)

(+)

(+)

4 Production Quantities

Required Final Output per day = 2 tonnes

Mass of coke lost during firing = 5% of feed mass

Therefore, Mass before firing = 2/0.95 = 2.2tonnes

Optimum moisture content = 9%

Therefore mass of pellets before drying = 2.1/(1-0.09) = 2.3tonnes

Mass of dry, ground iron ore = 2.3-0.09*2.3 = 2.1 tonnes

Assuming Sieving efficiency is 80%,

Ball mill discharge = 2.1/0.8 = 2.7 tonnes

Assuming losses of 5% at each comminution stage,

Rod Mill Discharge = 2.7/0.95 = 2.9 tonnes

Secondary Crusher Discharge = 2.9/0.95 = 3.1 tonnes

Primary Crusher Discharge = 3.1/0.95 = 3.3 tonnes

Therefore, Fresh ore feed rate = 3.3-0.2*3.3 = 2.7 tonnes

Required Capacities per day for Crushers are as follows,

Primary Crusher = 4 tonnes

Secondary Crusher = 4 tonnes

Rod Mill = 4tonnes

Ball Mill = 4 tonnes

5 Suggested Machines

While it is not possible acquire machines with the exact production volumes given in the previous

section, the machines with the closest production capabilities available in the market are given below.

5.1 Crushing and Grinding Circuit

High Output Iron Ore Grinding Circuit For Pelletizing Plant

Price : 200000 $

Figure 2 : Crushing Circuit

Table 1 : Crusher Circuit Details

Condition: New Type: Vertical Mill

Power(W): 165~385 Capacity(t/h): 1-14t/h

Brand Name: Clirik Model Number: HGM series

Warranty: 1 Year,1 year After-sales Service Provided: Engineers available to service

machinery overseas

Input size: ≤20mm Finished size: 5-47um

Delivery: 1 month Capacity: 1~14 t/h

Control

system:

ABB/Siemens Sound proof: Yes

5.2 Pelletizing Machine

Pellet Ball Mill

Price : 4000 $

Figure 3: Pellet Mill

Table 2 : Pelletizing Machine Details

Condition: New Type: Ball Mill

Power(W): as the model Capacity(t/h): depends on your choise

Brand Name: Xingbang Model Number: MQ/MBS

Weight: various Certification: CE,ISO9001:2000,CQC

After-sales Service Provided: Engineers available to service

machinery overseas

Ball mill output size(mm): 0.074~2.0

Voltage: 380V or as client's requirements Ball mill Type: both wet and dry

Maintenance: easy and convenient Spare parts of ball mill: supply whole year

Export countries: Eastern Northern Europe, Mid

East, Africa, South

American,ect.

OEM&ODM: OK

6 Cost

6.1 Capital Grinding Circuit = 20000 $

Pelletizing Mill = 4000 $

Set up cost and other accessories (approx) = 10000 $

Total Capital Cost = 214000 $

6.2 Operating Cost

Operating Cost per tonne of pellets produced. (Data from "Iron and Steel Vision 2020" and applicable to

the Indian industry.)

Power Consumption = 6 $

Fuel Consumption = 10 $

Coke = 0.7 $

Cement = 0.5 $

Labor = 2 $

Miscellaneous = 2 $

Total cost per tonne = 21.2 $

Total operating Cost 21.2*

7 Environmental Considerations

As considered in this report, if the hematite ore used in the pelletizing process is of 60% or higher Fe

content, chemical beneficiation methods such as froth floatation is not required. Therefore, chemical

treatment methods and waste water treatment methods used to remediate the byproducts of chemical

methods will not be considered in this case.

However the pelletizing process outlined here does pose some environmental threats in the form of

dust and gaseous emissions.

Dust generation is the main consideration here as dust is generated during each ore crushing and

grinding stage. To remediate this, standard techniques such as using dust covers in crushers and

grinders, and employing a thorough dust ventilation system can be done.

Dust generation in stockpiles could be minimized by periodic spraying of water over the stockpiles.

Figure 4 : Dust reduction by watering

Gaseous emissions take place only during the firing process. And such CO2 emissions are remediated by

having a tall emission pipes built into the furnace itself. However if the pellets are fed into a blast

furnace for iron production, gaseous emissions should be given more serious consideration.