MP-PIC Simulation on Solid Dispersion in a 350 MW CFB Boiler

Abstract

Solid dispersion has an important effect on fuel distribution and temperature uniformity in a circulating fluidized bed (CFB) boiler furnace. To investigate lateral and axial solid dispersion behavior in large-scale CFB furnaces, the multiphase particle-in-cell (MP-PIC) method coupled with chemical reactions was established using a 350 MW CFB boiler as an object. Influence factors including superficial velocity, primary air ratio, fuel particle size d p, and density ρp were studied numerically. In addition, the fuel dispersion characteristics using the particle property changing models including the shrinking size model, constant size model, and partial shrinking model were explored and compared. The computed result of solid dispersion shows that the average displacement of particles is enhanced by superficial velocity and primary air ratio. The solid dispersion coefficient in the width direction D x has a magnitude of 0.1 m2/s, while the coefficient in the depth direction D y is an order of magnitude larger than that of D x . Besides, particle initial size and density have a great impact on displacement and dispersion coefficient, especially in the direction of larger dimensions (furnace depth direction). In terms of particle property changing models, results show that particle size reduction exerts more influence on solid dispersion characteristics compared to density reduction.