Jindal Steel & Power Ltd.

SUBMITED BY

Brijesh SurgeDip. In Mechanical Engg.Govt. Polytechnic Jashpur

A 

PROJECT REPORT 

ON

 A

DRI

INDEX:-

* Introduction of DRI* Iron making.* Direct reduced iron process

(DRI).* Raw materials for DRI.* Sponge iron discharge

temperature.* Description of kiln.* Process in kiln.* Heat transfer in rotary kiln.* Process control parameters.* Reaction in kiln.* Quality of total product.* Uses of sponge iron.* Safety for trainee.

Introduction of DRI

Sponge iron is a term given to the product obtained by reduction of

iron ore in solid state. Sponge iron is a mixture of reduced metallic

iron, unreduced iron oxide and the associated with gangue

constituents of the original ore. It is also known as directly reduced iron {DRI}, metallized ore etc. much of the oxygen associated with the iron oxide is eliminated there by raising the content of metallic iron. Hence it is known as metallized ore.

PROCESSES OF MAKING SPONGE IRON:-

A Large No Of DRI Processes Available Today –

 

* Coal Based Processes Using Rotary Kilns.

 

* Coal Based Processes Using Other Type Of Reactors Like Rotary Hearth

Furnaces.

 

* Batch Type Gas Based Processes Using Reactors.

 

* Continuous Gas Based Processes In Shaft Furnaces.

 * Gas Based Processes Using Fluidised Bed Reactors

COAL BASED DRI PROCESS:-

These processes has an essentially been designed to carry out reduction using solid reluctant like non-metallurgical coal. Additional liquid or gaseous fuel may be burnt to generate the working temperature.

RAW MATERIALS FOR DRI PROCESS :-

There are following materials which are used as raw material for DRI process. * Non cocking coal * dolomite* pallets of iron ore

DESCRIPTION OF KILN:-

The kiln has been designed based on certain L/D ratio, percentage

degree of inclination, rpm etc.Kiln has a length of 70.8 m and a shell diameter of 4.2 meter. the kiln has inclination of 2.5% ,rests on four support stations .iron–ore dolomite and about 43-45% coal of the total coal charged into kiln from the feed end while the remaining 55-57% of the coal pneumatically feed into the kiln from the kiln outlet in two different size ranges at adjustable rates.

PROCESS IN KILN:- (Block Diagram) 

HEAT TRANSFER IN ROTARY KILN:-

For the solid reduction of iron ore, a reasonable tem. Of reduction

(1000-1100) has to be maintained over the length of the kiln. To

faceplate heat transfer, and discharge the material, a rotary action is

imparted to kiln.

PROCESS CONTROL PARAMETERS:-

In the operation of any DRI rotary kiln the following process parameters are

paramount:

 1. FEED RATE & PROPERTION OF MATERIAL 

2. KILN TEMPERATURE MEASURMENT

3. CONTROL OF GASEOUS ATMOSPHERE  4. GAS PRESSURE INDSIDE THE KILN 5. KILN ROTATION

REACTION IN KILN:-

SPONGE IRON DISCHARGE TEMPERATURE

The temperature of the sponge iron discharged from the rotary cooler is significant to prevent its re-oxidation during storage. This temperature is maintained below 700 C .For hotter material the cooler rpm is increased accordingly.

Coal Injection:

In general a mix of fine and coarse coal 40% to 50% of the total coal requirement for the process is fed from the discharge end through a coal injector. Coal is injected in such a way that fresh coal falls at various zones of the kiln so as to maintain the temperature profile.

Mean Particle Size

The mean particle size ratio of iron ore to feed coal shall be in the

range of 1.2 to 1.5 depending up on the characteristics of coal.

The mean particle size of iron ore shall be restricted to 11mm in order to achieve uniform Fe metallic of all grain size fraction of the product.

Retention Time

The time travelled by the materials in the kiln is taken as a reference for the assessment of the kiln condition. In case of a fresh kiln the retention time for a 100TPD kiln at 0.45rpm is 6-7 hrs,10-11hrs for a 350TPD kiln at 0.47rpm,.12-13hrs for 500tpd kiln at 0.43rpm.

QUALITY OF THE PRODUCT:

The important constituents determining the quality of sponge iron are the Fe total, Fe metallic , sulphur, phosphorous, carbon and gangue content.

Fe total:The Fe total content in sponge iron purely depends on Fe content in iron ore the degree of reduction achieved in the process. Fe total content of 90%min is required for steel making requirement.

Sulphur content: The sulphur content in sponge iron is controlled by adding 1-6mm of limestone/dolomite along with feed materials which picks up sulphur from the coal preventing the sulphur pick up in sponge iron. The sulphur content in sponge iron can be controlled in the range 0.012 to 0,025%.

Phosphorous content:The phosphorous present in the iron ore is retained as P2O5 in sponge iron without any change. The phosphorous content in sponge iron is generally varies from 0.06% to 0.09%.

Gangue content:As the removal of oxygen in iron ore takes place in solid state, the gangue content present in iron ore(mainly silica and alumina) remains in sponge iron without any change. In general the gangue content in sponge iron varies from 4% to 8%.  Carbon content:The carbon content in sponge iron produced by coal based rotary kiln processes are generally low and is in the range of 0.08% to 0.20%.The carbon content in gas based processes can be controlled to a level of 1.5% to 2.0% based on requirement for steel making. 

Size Distribution:The size distribution of sponge iron lumps varies with decrepitating behavior of iron ores. As the Fe metallic content in sponge iron varies for each size fraction control of feed size of iron ore is very important for achieving uniform Fe metallic content. The typical size distribution and Fe metallic for each fraction is as given below.Particular

s+16 mm +12 mm +10 mm +5 mm -4 mm

Fe metallic

79.36 82.28 83.35 81.54 85.01

Fe total 90.00 91.31 92.55 91.76 95.55

Percent 4.21 14.74 27.37 33.68 20.00

USES OF SPONGE IRON:- 

DRI has been successfully used in the following steel melting units:Electric arc furnaces, as a substitute for scrap.Basic oxygen furnaces, as a coolant during the blow,& as a substitute for scrap in the initial charge.Induction furnaces , as a feedstock.Open hearth furnaces , as a charge for melting. Ladle furnaces , as trimming addition.

SAFETY RULES FOR TRAINEE:- 

1. Always use safety Helmet & shoes during the plant training.

2. Don’t very near to the hot metal.

3. Don’t go very near to moving machines.

4. Don’t enter in a prohibited area.

5. Beware of gas & fumes.

6. Don’t touch machines & instrument.