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| Product: Sponge Iron |
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| Introduction |
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| Sponge iron is a metallic product produced through direct reduction of iron ore in the solid state. It is a substitute for scrap and is mainly used in making steel through the secondary route. The process of sponge iron making aims to remove the oxygen from iron ore. The quality of sponge iron is primarily ascertained by the percentage of metallization (removal of oxygen), which is the ratio of metallic iron to the total iron present in the product. |
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Sponge iron manufacture is highly sensitive to raw material characteristics. Therefore, it is essential to examine the chemical and physical characteristics of raw materials, both individually and in combination. The basic raw materials for the production of sponge iron are iron ore, non-coking coal and dolomite |
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| Properties of the product |
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| Properties of Sponge Iron |
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High iron content and high degree of metallization |
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Uniform and consistent quality |
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Lower sulphur and phosphorus content |
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Negligible tramp element |
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Minimum dust generation during material handling |
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Good flowability in bins, pipes and conveyors for continuous and trouble free charging |
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Superior technical support to induction furnace operators |
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| Quality and certification |
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| Quality |
WPSL Employees at all levels shall continually strive to provide consistent and reliable, Quality products & services to their external and internal customers and try to exceed in their expectations. This goal shall be sustained, through committed teamwork and continual improvements in the Quest for excellence.
WPSL takes pride in its product quality and the timeliness of its delivery schedules.
This modern plant is equipped with a digital control system. The advanced microprocessor based control allows for a complete automated functioning, ensuring a high quality of output.
Strict metallurgical control is maintained at every stage of production, from receipt of raw materials to dispatch of finished products. The Company has a dedicated Quality Assurance Department with a well equipped laboratory and trained technicians to monitor the process and materials at different points.
The Company is pursuing ISO:9000 Certification. It is in the process of developing and implementing quality systems throughout the Company. It hopes to achieve the Certification in 2006-07. |
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| Products Specification |
| WPSL has 4 x 100 tonnes per day (TPD) rotary kilns. The combined capacity will be 1,30,000 TPA. A part of the sponge iron is consumed ourself to produce steel, the rest is sold to other Steel Manufactures. |
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| Chemical Properties: |
| Elements |
Sponge Iron Lumps |
Sponge Iron Fines |
| Fe (M) |
80 ± 2% |
80 ± 2% |
| Fe (T) |
90 ± 2% |
90 ± 2% |
| Mtz % |
88± 2% |
88± 2% |
| P |
0.06% |
0.06% |
| S |
0.04% |
0.04% |
| C |
0.25% |
1.00% |
Non-magnetic
(Char & Other Process Contaminants) |
1% (max.) |
2% (max.) |
| Sio2 + Al2O3 |
6% (max.) |
6% (max.) |
| Cao + Mgo |
1% (max.) |
1% (max.) |
| Size (mm) |
3 to 20 |
0 - 4 mm |
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| Physical Properties : |
| Elements |
Sponge Iron Lumps |
Sponge Iron Fines |
| Bulk Density (gm/cc) |
1.80 |
1.75 |
| Cold Crushing Strength |
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(WPSL) reserves tech right to change specifications with out notice consequent to improvements effected in the process) |
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Chemical analysis indicated above refers to only magnetic fraction of material and not in combination with Char and other contaminants. |
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Estimation of metallic iron is by “By Mercuric Chloride" method. |
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Degree of metallization indicated the degree of reduction to iron oxide to iron carbide. |
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| Technology |
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S - Steel company of Canada
L - Lurgi of Germany
R - Republic Steel Corporation
N - National lead of USA |
| SL/RN technology is a coal based rotary kiln reduction process |
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| Process |
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Summery
A long slightly inclined to the horizontal slowly rotating kiln is employed to carry out the reduction. The charge is fed from that end which is at a higher level it travel under gravity aided by the rotating motion through several heating zones & the reduced charge come out from the other of the kiln.
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Details
For the direct reduction of iron ore the main furnace used is rotary kiln. The rotary kiln is the refractory lined cylindrical vessel on which blowers are mounted & the air pipes, to provide combustion air to the kiln there is a strut up burner at the kiln discharge end which is oil fired to heat up the rotary kiln. When the desired temp. is reached, Iron ore , coal & lime stone or dolomite are fed from kiln feed end and also coal is blown from kiln discharge end. |
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The start up burner which uses oil for initial heat up is withdrawn. Now the coal if the desired temp. for reduction process. Since the kiln has a downward slope to ( 2-1/2%) from the feed end side to discharge end side, its rotation causes the iron ore & coal to mix and travel through the system. The rotational speed of the kiln is adjustable as per the feed rate & percentage of metallization. The % age of inclination, rotational speed the length of the time the material is exposed to the atmosphere, the temperature all to be taken into consideration the kiln has three functions. |
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It is a heat exchanger |
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It is a vessel for chemical reaction |
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It is conveyor of solids |
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Degree of metallization indicated the degree of reduction to iron oxide to iron carbide. |
| Fr the Better the heat transfer & better the metallization |
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The following reaction takes place inside the kiln.
Fe2O3 + 3 CO = 2 Fe + CO2
However the reduction from oxide to metal does not occurs in one step but by a gradual removal of oxygen giving rise to various intermediate oxides the reduction chain may be expressed as follows:
2 Fe2O3 ------------------------- 2 Fe3O4 ------------------- 6 FeO -------------6 Fe
Hematite Magnetite Wustite Iron
The degree of reduction between each stage is as follows:
11% 22% 67%
3Fe2O3--------------------- 2Fe3O4-------------------------- 6FeO--------------6 Fe
The byproduct of above reaction is carbon die oxide (CO2).
This Co2 reacts with carbon from coal to produce CO.
CO2 + C = 2 CO.
The above reaction is known as bound ward reaction which is reversible. |
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| Raw Materials and procurement of the same |
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| Raw Materials for Sponge Iron Making: |
| Coal |
| Important factors determining coal quality are: |
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Chemical properties such as fixed carbon, ash content, volatile matter, etc.: & |
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Physical properties viz., reactivity and ash fusion temperature. |
Welspun sources its entire coal requirement from the imported coal by the China & South Africa. |
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| Iron Ore |
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In sponge iron making, iron ore is reduced in solid state. Unlike in the conventional steel melting processes, the gangue content of iron ore cannot be separated as a slag. Therefore, it becomes imperative to select an ore with a high Fe content and a low gangue content, to optimize yield during steel making. Apart from this, to ensure a better kiln campaign life and output, the iron ore is made to undergo a series of other tests viz. shatter, tumbler & abrasion indices, reducibility etc.
By virtue of its location, Hospet & Orissa regions which has one of the finest quality iron ore in the region. |
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| Dolomite |
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Dolomite acts in the process as a desulphuriser, removing sulphur from the feed mix during the reduction process. It is mixed in small proportion along with other raw materials before charging into the kiln. It is procured by the Rajasthan regions. |
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| Any specific features if any |
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| Environment : |
| The sponge iron kilns give off hot gases rich in carbon monoxide. WPSL has installed 4 Nos of 10 TPH Waste Heat Recovery Boilers (WHRB) and 1 Nos of AFBC Boiler of 20 TPH ( With ESP's & Ash Condentioning system) and is using these gases to generate steam. steam to produce 12 Mwe power. |
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WPSL has in place 8 nos of varies capacity pollution control system ( Bag Filter). It has also been planting trees in and around the premises to keep it green.. Apart of Above activity Company has introduced the Water Sprinkler system to control the pollution of Open Field & Road Aera . The company's commitment to environment is visible on the plant site. |
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Advantages of Sponge Iron |
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Chemical composition is uniform & known. |
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It contains no undesirable impurities. |
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It permits dilution with low cost scrap. |
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Easy to handle & transport. |
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Permits automatic continuous charging. |
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Less noise during melt down. |
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More predictable price structure. |
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No trump elements. |
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