Numerical investigation of biomass pyrolysis performance in a fluidized-bed reactor by a TFM-DEM hybrid model

Abstract

A hybrid model, which combines two-fluid model with discrete element method as well as a multi-component and multi-step pyrolysis scheme, has been developed to simulate biomass pyrolysis in a fluidized-bed reactor. Gas-solid flow pattern, bubble characteristics, biomass conversion behavior and pyrolysis products are systematically analyzed. Moreover, the differences among four operation parameters are highlighted. Results show that increasing gas velocity and operating pressure or decreasing bed material size reduces solid holdup in central region but increases solid rising and falling velocities. Raising gas velocity elongates the bubbles and improves their rising velocities. Increasing operating temperature or pressure accelerates particle mass loss and shrinkage. Additionally, a higher gas velocity and operating pressure are unfavorable to light gas and tar yields. A higher temperature is beneficial for energy recovery coefficient of light gas, while that of tar achieves its highest values at 773 K. All these observations help understand biomass fluidized-bed pyrolysis.