The iron and steel industry is one of the largest industrial sources of CO2 emissions which accounts for approximately 6.7% of total world CO2 emissions in 2010. Up to date, the solutions to reduce CO2 emissions in the iron and steel industry can be feasible but extremely expensive or difficult to do. Therefore, it is important to develop new carbon capture technologies coupled with energy intensive process that will reduce the impact of the global climate change on the continued fossil energy use. Chemical looping combustion, having potential for realizing very efficient and low cost CO2 capture, can be a good candidate to reduce CO2 emissions in the iron and steel industry when combined with FINEX process developed by POSCO in KOREA. Such technologies as fluidized beds, Fe-based particles as oxygen carriers, a reduction process, and a recycling of waste materials developed in FINEX can be applied to a CLC system combined with FINEX process.
As a feasibility study, metal oxides of the iron and steel industry as oxygen carries and FINEX off-gas as a fuel were investigated for a hydrogen production and power generation with high efficiency. As metal oxides, the intermediate products of the iron and steel industry with average particle sizes of 1mm and 25 microns were selected and tested in small fixed and fluidized beds. The proper kinetic model for a redox reaction of the metal oxides was found to be the Jander equation based on the three-dimensional diffusion mechanism with stable cyclic reactions at 700 and 800 oC. In the fluidized beds, large particles were well fluidized while the small particles were fluidized with Geldard B particles of above 60 weight %. In air reactor, reduced iron of the large particles proceed to partial oxidation to Fe3O4 with the fully oxidized outer surfaces of Fe2O3, which eventually prevents the oxygen transport for the full oxidation of iron oxides. Temperature of the reactor increased from 700 to 1150 oC. In hydrogen reactor of the small particles mixed with Geldard B particles of 60 weight %, the yield of hydrogen production was about 70 ~90% during the stable redox cyclic reactions.
The obtained results show a possibility for the hydrogen production and power generation. They will contribute to designing an innovative ironmaking process with less CO2 emissions in the future.
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