(408e) Numerical Simulation of the Effects of Size Change in a Coal Gasifier Using Method of Moments Approach

The population balance model (PBM) and the governing computational fluid dynamics (CFD) equations were used to simulate the effect of size change in a coal gasification process using the finite size domain complete set of trial functions method of moments (FCMOM) approach. The goal of this study was to demonstrate the effect of property (e.g. size and density) variation of coal char particles in the simulation, design, and scale-up of gasification processes. In this study, the process of coal char gasification in a fluidized bed at elevated temperature in the presence of hydrogen and steam as gasification media was simulated. The coupling of coal char size variations, hydrodynamics of the system, and heterogeneous gasification reaction rate were included in the simulation. The heterogeneous gasification reaction was modeled based on the available experimental data from Gas Technology Institute (GTI) using the shrinking core model. The simulation results showed that the effect of particle property variations (e.g., size) during a process such as gasification of coal char in a fluidized bed plays a very significant role in the modeling and design of such processes. Initially, as the coal char particles were gasified, the coal became smaller; therefore, the effect of mixing in the particulate phase became more pronounced (as a result of the formation of bubbles). Ultimately, the effects of mixing became less significant due to a reduction in the bed height, which, in turn, suppressed the formation of larger bubbles.