Chemical looping combustion is an indirect combustion process that uses a solid metal oxide as an oxygen carrier to transport oxygen from the air to the fuel to effect combustion. After the fuel conversion, the oxygen-depleted solid oxygen carrier must be re-oxidised back to the oxygen-rich form to start a new cycle. Our research focuses on the development and optimisation of oxygen carriers for use with gasified biomass or coal.  Because these fuels contain contaminants such as sulphur and chlorine, cheaper oxygen carriers such as those based on iron are preferable.  These oxygen carriers are most commonly fabricated by complex methods such as freeze granulation and wet-impregnation, but only a few papers have focused on the development of Fe-based oxygen carriers using mechanical mixing techniques and many improvements are possible to these techniques as currently implemented. Here, we present the detailed preparation procedures of Fe-based oxygen carriers using a number of mechanical mixing techniques.  A range of analytical methods were applied to assess the chemical and physical properties of the particles and to determine their suitability for use in large scale chemical-looping systems. The reduction kinetics (the rate limiting step in the CLC of gaseous fuels) were assessed for the OC particles consisting of pure Fe2O3 and 60wt.% Fe2O3 on an Al2O3 support  using a thermogravimetric analyser (TGA) and also a fluidised bed. The aim of the work was to produce and investigate inexpensive particles of high reactivity and robust physical characteristics.  The effects of small quantities of H2S on the long-term reactivities of some particles was also studied, since (as discussed above) it is likely that such contaminants will be present in syngas produced from gasifiers.

Effects of different preparation methods on chemical looping compounds

247th National Meeting (2014)

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