Prediction of bubble fluidisation during chemical looping combustion using CFD simulation

Bubble fluidisation in the fuel reactor adopted in chemical looping combustion (CLC) has a siganificant impact on the operation efficiency. Although a variety of numerical modellings of fluid dynamic process in the fuel reactors have been conducted, studies on predicting the fluidised bubble behaviours in the cylindrical fuel reactor where the effect of the heterogeneous reaction is also considered are still lacking. In this paper, the use of correlations of fluid dynamic parameters to characterise the fluidised bubble formation in the fuel reactor was proposed. A correlation parameter relating the time-dependent fluidised bubbles to the local eddies was introduced by correlating the local gas velocity fluctuation with the pressure fluctuation. The existence of a strong correlation between the concentration of gaseous reactants or products and local vortices was also demonstrated. Three-dimensional multiphase CFD model coupled with the heterogenoeous reaction kinetics was employed to study the details of CLC process in the fuel reactor. The results clearly indicated that the approach used in the present work can effectively monitor the formation of fluidised bubble in the dense fluidised bed during the heterogeneous reaction and may be used in the CLC as an indicator for monitoring the reduction rate as the locally embedded large eddies are strongly associated with the fluidised bubble occurrance.