Experimental and kinetic studies on in-situ CO2 gasification based chemical looping combustion of low ash coal using Fe2O3 as the oxygen carrier

Chemical looping combustion (CLC) technology has grabbed the attention for rectifying the carbon capture issues with minimal energy penalty. The direct utilization of solid fuels such as coal and biomass in CLC by in-situ gasification technology would reduce the complexity of the overall process. In the present study, in-situ CO2 gasification of direct-coal fueled CLC experiments are conducted using a fixed bed reactor under atmospheric pressure in a batch-wise mode of operation. The low cost metal oxide, Fe2O3, is used as the oxygen carrier particles for the CLC of a low ash based North East Indian coal. Pyrolysis and CO2 gasification experiments are performed with and without the presence of metal oxides for estimating the CO2 yield. The results show that the CO2 yield is increased from 17.5% (without metal oxides) to 88.7% (with metal oxides) under the N-2 atmosphere. A highest CO2 yield of 96% is observed under in-situ CO2 gasification incorporated CLC conditions. Further, thermo gravimetric analysis (TGA) is conducted to study the conversion and instantaneous reactivity between the coal and metal oxides. It is estimated that 83% conversion of the coal-Fe2O3 mixture is attained under the CO2 atmosphere, while it is 57% in the N-2 atmosphere. The kinetic parameters are estimated using the TGA data for the reaction between coal and metal oxide under N-2 and CO2 atmosphere using reaction order models. It is found that the first and third order models show the best fit for the non-CLC and CLC process, respectively.