Numerical simulation and structural optimization of multi-compartment fluidized bed reactor for biomass fast pyrolysis

Abstract

A multi-compartment fluidized bed reactor for biomass fast pyrolysis was designed. Numerical simulation of gas-solid two-phase flow under cold state in the reactor was investigated by the CFD software - Ansys Fluent 16.0. The feed rate and internal structure of the reactor were optimized by studying the effects of the feed rates, the opening sizes of the compartment clapboards and the elevation angles of deflectors at the openings on the materials transport performance in the reactor. This pyrolysis reactor could achieve continuous production, which allowed the materials to flow sequentially and uniaxially between adjacent compartments, thus inhibiting the back-mixing of particles in conventional fluidized bed. The optimum feed concentration for the reactor was about 4.4 kg/m3 (the mass flow rate was 0.04 kg/s). The optimal opening size was 1/6 (5 cm) of the height of the compartment, and the optimal elevation angle of deflectors was 45°. Finally, the cold state experiments were conducted to verify the correctness of the numerical simulation and confirmed the rationality of the structural parameters of the reactor. Our studies have provided a new structural design of the reactors for biomass fast pyrolysis with numerical simulation.