Iron Ore Reduction with Coal/Carbon

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INTRODUCTION

The use of coal instead of coke as reductant in the iron and steel industry has become more important because this industry realised that coking coal supply could soon be less than demand (Nashan et al., 2000). Furthermore, the future trend is expected to tend toward process consolidation by reducing the number of reactors needed to produce steel from raw material (Wiesinger, 2000). Accompanied with the trend in coal usage has emerged several processes that use iron ore fines, which are not compatible with older iron making technologies when not agglomerated or pelletised (Sarma and Fruehan, 1998).
Most of these processes use natural gas to reduce fine iron ore to directly reduced iron (DRI). A few processes that use coal as reductant to produce DRI have been developed. These are the rotary kiln type processes: SL/RN (Bornman and Ackerman, 1993), Accar (Rierson, 1993), Davy DRC (Haworth et al., 1995) and rotary hearth based processes: Fastmet (Hoffman and Harada, 1997) and Comet (Borlée et al., 1999) processes. Of these processes, only the rotary kiln type processes have been commercialised on a large scale. The only commercially established coal based process to produce hot metal is the Corex process (Flickenschild et al., 1996). Other hot metal processes have been developed: AISI (Aukrust, 1992), Hismelt® (Cusack et al., 1995), Dios (Saito, 1992), Romelt (Romenets et al., 1999), Ausmelt (Floyd, 2000) and Technored (Contrucci, 2000). The first commercial Hismelt® plant has been successfully hot commissioned in October 2005 in Kwinana, Western Australia and production will be ramped up to full capacity over three years to 800 000 t/year (Rio Tinto News Release, 2006).
Thus, it is evident from the development of the above mentioned processes that the use of coal and iron ore fines is becoming more important as traditionally used feed stocks of iron ore and coal are depleted. Only the Comet (Borlée et al., 1999) process uses coal and iron ore fines in a fixed material bed, although in alternate layers, to produce DRI. The hot metal production processes do use coal and iron ore fines, but these raw materials are reacted through bath smelting.
The IFCON® process is a direct steelmaking process reacting iron ore fines and coal in a single vessel to produce crude liquid steel. Material mixture of ore fines, coal and fluxes of -10 mm is fed onto the liquid metal bath to form heaps floating on the metal bath. The freeboard is heated by combustion of natural gas and an air and oxygen blast blown into the freeboard via burners. In addition to the natural gas that is combusted in the freeboard, the coal volatiles and reduction product gas from the heaps are combusted to generate heat in the freeboard. The upper portion of the heap where solid state reduction takes place is heated by fossil fuel energy generated in the freeboard. The bottom ends of the heaps are heated from the metal bath, which is in turn heated by inductors.

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Introduction
Chapter I: Literature Survey
1.1. Background
1.2. Iron Ore Reduction with Coal/Carbon
1.3. Indicators for Heat Transfer Contro
1.4. Chemical Reaction Rates
1.4.1. Reduction
1.4.2. Gasification
1.5. Conclusion
Chapter II: Experimental
2.1. Experimental Set-up
2.1.1. Furnace
2.1.2. Gas Lines
2.2. Calibration
2.2.1. Radiation Network
2.2.2. Emissivity Measurement
2.2.3. Sample Surface Temperature Measurement
2.2.4. Calibration of Radiation Network Calculation
2.3. Conclusion
Chapter III: Results and Discussion
3.1. Introduction
3.2. Effect of Increased Heat Transfer
3.3. Effect of Layer Thickness
3.4. Effect of Volatiles in Coal
3.5. Phase chemistry of Metal and Oxide Phases
3.6. Effect of Particle Size
3.7. Conclusions and Future Work
Chapter IV: References
Chapter V: Appendices

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