Macroscopic fuel reactor modelling of a 5 kWth interconnected fluidized bed for in-situ gasification chemical looping combustion of coal

A macroscopic model is developed to simulate the fluid dynamics with the transfer of heat and mass in the fuel reactor and the riser of a novel 5 kW(th) interconnected fluidized bed system for chemical looping combustion of coal. The fuel reactor and the riser are divided into a bottom bed consisting of bubble and emulsion phases, a freeboard with splash and transport phases, a transition zone with different cross-section areas and a riser providing the driving force to recirculate solids between the fuel and air reactors. The developed model is validated by the experimental cases with different operation conditions such as thermal power, temperature and coal feeding rate. Subsequently, the effects of reactor temperature, solids inventory, oxygen carrier to coal ratio and compositions of the fluidizing agent on the reactor performance are analyzed in details by the help of the validated model. The sensitivity analysis shows that the reactor temperature is the most relevant parameter affecting the combustion efficiency and CO2 capture efficiency. Furthermore, increasing the oxygen carrier to coal ratio increases the combustion efficiency but decreases the CO2 capture efficiency, while increasing the volume fraction of CO2 in the fluidizing agent has the opposite effect on the performance of this experimental unit.