Technology and equipment for production sponge iron from hematite are fines through Rotary Hearth Furnace has been demonstrated in a setup in China having feed capacity 100,000 Ton per annum. Mean diameter of Furnace is 13.5m. Scale – up of design is ready for 500,000 Ton per annum sponge iron capacity. Low grade Iron ore fines can be utilized, and further processing of produced hot DRI is feasible in electric furnace for desired grades of iron and steel. Coal as reductant is preferable of high grade, whereas lower grades are tolerated.

The methodology envisages cold briquetting of iron ore fines and reductant coal along with limestone/dolomite flux as compared to traditional high temperature agglomeration method. This amounts to lesser investment, easy operation and low input material handling cost and more environmental friendly. In Rotary Hearth Furnace,waste heat of exhaust gas is utilized efficiently by heatup of combustion gasous fuel and combustion air. Dust removal of exhaust gas is in dry bag filter without cosuming fresh water.

Production Line For DRI Sponge Iron has following sectional units :

  1. Raw material storage and Drying in rotary dryer : Rotary dryer’s works on hot gas from producer gas fired furnace.
  2. Raw material Blending and Briquetting :Iron ore fine fed through belt conveyor. Pulverized Coal supplied through pipeline. Betonies and Flux dumped by truck. Materials are loaded to Belt conveyor after weighing , and mixture is passed over to Mixing units. Wheel Rubbing Mill mixes the ingredients and then loaded into high pressure ball – press machines. Shaped green pellets are screened by Roller screen, and then are loaded into Rotary Hearth Furnace.
  3. Reduction of Iron ore in Furnace :Green pellets fed by feeder/material  distributor of rotary hearth furnace gets roasted and reduction by CO results in DRI Sponge Iron. In rotary hearth furnace, carbon containing pellet is progressively heated to max.  1400°C  to produce DRI.
    Fuel is producer gas with CV : 1300Kcal/NM³
    Max. furnace temperature    : 1400° C

    DRI specifications:
    Specific gravity                  : 1.8-2.0 Ton/M³
    Granularity                        : < 30mm
    Discharge Temperature    : 800°C

  4. Finished DRI product on Cooling :Cylindrical cooler brings down temperature of DRI pellet to 300°C with about 300mm dia. Swirling action in cooler with installation angle moves the material from feeding end to discharge end. The two ends are sealed by nitrogen, thus air can be stopped.

Cold clean gas (pressurized 15 kPa ) from two-stage coal gasifiers are considered.

Water : Makeup water is required for Cooling water in circulation Furnace seal has separate circulating water being turbid.
Power : Power distribution is to be planned on consideration of further processing of hot DRI in electric furnace for requisite grades of iron/steel.

Production Process and technology for direct production of Sponge Iron from Iron Ore fines without any need of either palletization nor sintering is offered adopted Tunnel kiln and Hematite Iron ore fines. Shape of produced sponge iron is in form of briquette having better density compared to DRI FROM Rotary kiln. Machinery and equipment chosen are up-to-date, reliable, energy saving and environment friendly. Modules are available for 75,000 TPA and 150,000 TPA comprising of three kilns in a group-kiln length is 185m and 260 m in aforesaid module respectively.

Process:

  1. Hematite Iron ore fines (TFe˃ 60 % ) is sized ˂ 1mm ina Hammer mill. Cylindrical Briquettes with hollow core are formed out of same in a Press and then to be put in Silicon Carbide saggers, one over another. They are piled up there with annual space left out from stagger wall. Limestone and Coal Powder are sized in Jaw crusher and Hammer mill. Their mix is put in annual space and hollow core, after pile up of Iron ore briquette in Staggers mentioned as above. Staggers are then placed in Trolley car.
  2. Loaded cars travel in Tunnel kiln three ( 3) such Tunnel kiln are envisaged. Tunnel kiln is fired with producer gas from coal gasification. Reduction temp. is 1140 -1200 degree and reduction time -42 hours. Sponge iron produced from staggers is in briquette from for further end use. Any removal of impurities in above sponge iron could be carried out by Magnetic separation. It requires size reduction of same before magnetic separation step. Fine sponge iron is then Briquetted to have Cold Briquetted Iron of requisite specifications and shelf life.

    Raw material standards :

     Iron ore fines :  TFe>60%,  SiO₂ + Al₂O₃< 7.5%, CaO <2.5%. MgO < 1.5%
                               Gangue <10%, S< 0.06%,P < 0.06%, Moisture < 10%
    Coal                 :  FC > 60%, Volatile < 20%, Ash <10%,Sulpher < 1%,Moisture < 10%,.
    Fusion temp. > 1200°C
    Limestone        :  CaO > 50%

    Sponge Iron Standards:
    For TFe 67%

    1. H90: TFe 90-92, S 0.02-0.025, P 0.04-0.06, Other Oxides < 6%
    2. H88; TFe 88-90, S 0.025-0.03, P 0.06-0.08, Other Oxides < 7.5%

    Sponge Iron Grades :  TFe 80-83%       84-86%
    With Iron ore finess      TFe 61-63%       63-65%

    Consumption Norms :  
    Ore fines     1.4 T/T
    For TFe 67%    Coal       0.45 T/Tcharge
    Limestone       0.1   T/T charge
                 
    Utilities :
    Producer gas
                   Coal   0.65 T/T
                   Water    0.1  M³/T
                  
    Power Load :
    Size Reduction and Handling, Briquetting,
    Tunnel kiln    : 2500 Kw ( 75,000 TPA Module )