Towards a hybrid Eulerian-Lagrangian CFD modeling of coal gasification in a circulating fluidized bed reactor

Numerical model of coal gasification in circulating fluidized bed (CFB) using Eulerian-Lagrangian approach is presented in this paper. The Dense Discrete Phase Model (DDPM) model of ANSYS FLUENT is used to simulate the flow of the particulate phase in the coal gasifier. The coal particles, with a size distribution, are tracked in the fluid velocity field including coupling between the phases. Kinetic Theory of Granular Flow is utilized to model the particles' interactions. The analyzed CFB comprises a small scale experimental facility in which coal is gasified in air and air/steam mixture. The reactor is composed of a barrel like bottom part with developed internal recirculation of the solid phase and 3.74 m high riser section. The homogenous gas phase reactions are modeled using the finite rate and eddy dissipation models. The heterogeneous reactions on coal particles surface are modeled using the finite rate chemistry. A total number of 14 reactions are considered. Results of the simulations were compared with experimental data.