Chemical looping gasification of cotton stalk with Cu/Ni/olivine in a Micro-fluidized bed Reactor: Gaseous products distribution and kinetics

Gas releasing characteristics and kinetics of chemical looping gasification (CLG) of cotton stalk (CS) under isothermal conditions have been investigated in a micro-fluidized bed reactor analyzer (MFBRA). NiO and CuO supported on olivine (Cu/Ni/O) used as oxygen carriers (OCs). The kinetic parameters for the formation of the main gaseous products were analyzed by model fitting method. Results indicated that due to the synergistic effect of CuO and NiO, the carbon conversion has been reached to 97.2% for 9Cu/6Ni/O. The Shrinking core, Jander equation and Ginstling-Brounshtein equation with their higher fitting coefficients were selected to calculate the activation energy (Ea). Ea for CH4 and H-2 decreased while Ea for CO2 increased with the presence of OCs. The Ea of CO generated from olivine were increased, while Ea of 15Cu/O, 15Ni/O and 9Cu/6Ni/O decreased. Further comparing the Ea, in the CLG process, the gasification effect of different OCs on the gas composition is different. The kinetics of CLG of CS with 15Cu/O, 15Ni/O and 9Cu/6Ni/O were calculated to be 81 similar to 103 kJ/mol, 116 similar to 147 kJ/mol and 99 similar to 133 kJ/mol respectively, which indicate that the prepared bimetallic OC can be a more suitable OC for CLG both in terms of conversion effect and Ea due to synergistic effect of Ni and Cu.