Fluidization Characteristics of Silicon Carbide in Fluidized Bed Under Microwave Irradiation

Cunfeng Ke ^a, Qingang Xiong ^b, Yaning Zhang ^a, Yunlei Cui ^a,

Liqing Li ^a, Bingxi Li ^a

^a School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

^b IT Innovation Center, General Motors, Warren, MI 48092, USA

Abstract Microwave-assisted pyrolysis of biomass is increasingly hot in recent years due to the many advantages of microwave irradiation over electric heating, i.e., fast, efficient, etc. However, this promising technology suffers from low temperatures in the reaction unit due to the poor microwave absorbability of biomass. In this case, microwave absorbent is needed. The main objective of this study is to investigate the fluidization characteristics of silicon carbide (SiC) which can be used as an efficient microwave absorbent in fluidized bed under microwave irradiation. SiC volume fractions and temperature fields at different fluidization velocities (0.3, 0.4, 0.5, 0.6, and 0.7 m/s), microwave powers (500, 600, 700, 800 and 900 W), initial volume fractions (0.20, 0.25, 0.30, 0.35, 0.40), and particle diameters (0.3, 0.4, 0.5, 0.6, 0.7 mm) are detailed. The results show that initial increases in the fluidization velocity benefit the fluidization whereas a column appears in the bed when the fluidization velocity is further increased, and the critical fluidization velocity is 0.6 m/s. Increases in microwave power accelerate the heating while the heat cannot be transferred to the airflow in time. The microwave power of 500 W shows better SiC distribution and better temperature distribution. Increases in initial volume fraction result in better particle distribution and better heat transfer performance, and the initial volume fraction should be lower than the highest value (0.40). Increases in particle diameter deteriorate the fluidization, and the best particle diameter is 0.3 mm.

Keywords: fluidization characteristics; silicon carbide; microwave irradiation; numerical simulation