Simulation and optimization of heating rate and thermal uniformity of microwave reactor for biomass pyrolysis

Abstract

Owing to the widespread utilization of hydrogen energy, hydrogen production from biomass by microwave pyrolysis has gained considerable research attention. In this study, a microwave reactor was modeled, and a dielectric coefficient measurement system was used to measure the variation in the dielectric coefficient of biomass during pyrolysis. Microwave power density, loading radius, and bulk density were varied and optimized by simulations for hydrogen production from biomass. To verify the advantages of the optimization method used in this study, an orthogonal experimental design was adopted as the comparison group. The results showed that when the control strategy of variable microwave power density was adopted (40 W/g for 500 °C, 50 W/g for 500–700 °C, and 20 W/g for above 700 °C), the optimal loading radius was 27.5 mm (the height-to-diameter ratio of the corresponding microwave reactor was 1.818) and the optimal bulk density was 370 ± 5 kg/m3, at which a favorable heating rate and thermal uniformity for hydrogen production from biomass were achieved. Under the conditions optimized in this study, thermal uniformity higher than that of the comparison groups was obtained, and its coefficient of variation was only a third of that of the comparison groups.