Simulation of coal pressurized pyrolysis process in an industrial-scale spout-fluid bed reactor

Abstract

A three-dimensional Eulerian-Lagrangian model, facilitated with multiphase particle-in-cell (MP-PIC) method, was developed to simulate gas-solid flow and pyrolysis characteristics of coal (with the capacity of 500 thousand tons per year) in an industrial-scale spout-fluid bed reactor (H = 16.6 m and D = 3.1 m), aiming at providing guidance for industrial application of pressurized grade conversion of coal. The performance of the reactor and the effects of operating parameters such as coal feeding rate, semi-coke to coal ratio, and particle sizes were numerically investigated. It was found that the flow pattern in this case is a “jet in the fluidized bed with bubbling”. The raise of pressure has a positive impact on the spouting structure and the flow uniformly. The increase of the semi-coke to coal ratio is beneficial to the coal pyrolysis, but the improvement of the pyrolysis is limited and the number of particles in the reactor will be sharply increased. With the increase of particle sizes, the flow pattern in the pyrolysis reactor tends to be stable while the mixing effectiveness is getting worse. It is suggested that the particle size of the material should range within 0–6 mm.