Aim of the project “Multi-scale analysis and optimization of chemical looping gasification of biomass” of the Hamburg University of Technology (TUHH) with the Southeast University (SEU) is the detailed modeling and subsequent optimization of a Chemical Looping Gasification (CLG) process. For this purpose, the process is simulated using the multiphase particle-in-cell (MP-PIC) method, which allows a detailed simulation of even large-scale units with affordable computational efforts. This paper deals with the implementation and validation of the reaction model for the gasification reactions.