Executive Summary : | Gas-based reduction of iron oxides, particularly with H2 as the reductant, can be carried out with significantly less specific energy input because of lower temperature requirements. Also, the CO2 emissions from such a process will be remarkably less with the direct CO2 emissions being zero if pure H2 is used. In this work, a fundamental study on the reduction of iron oxides using H2-CO mixtures will be performed in the temperature range 550-1100°C with the aim of determining the technical feasibility of a low-temperature alternative ironmaking process based on the counter-current reduction of iron oxide particles by H2-CO mixtures in a moving bed reactor. Iron ore concentrates will be used directly without any pre-treatment, and they will be either formed into green pellets, or simply into a loose layer of particles. The temperature at which a bed of concentrate will be reacting under interparticle diffusion control mechanism will be determined by formulating the global rate-expression for reduction incorporating the effects of temperature and partial pressure of gases (in the H2-CO mixtures). Since wüstite (FexO) is known to form in the Fe-O system at temperatures greater than 560°C, the effect of wüstite formation on the reduction rate will be modeled. Also, since the shape of the agglomerate is expected to affect the reduction rate, a model will be developed to account for the effect of the shape of the agglomerate on the reduction rate under different controlling mechanisms. The global rate-equation will be used together with the models which will account for the effects of shape and wüstite formation in designing a moving bed reactor. The reactor will be based on the proposed technology and will produce iron that can feed a steelmaking process at a capacity comparable to other alternative ironmaking technologies. |