MP-PIC simulation on CO2 gasification of biomass in a pilot plant circulating fluidized bed gasifier

Abstract

CO2 gasification of biomass offers a potential carbon-negative solution which combines biomass-to-energy conversion with carbon capture and utilization. In this study, biomass gasification with CO2 in a pilot plant circulating fluidized bed (CFB) gasifier is numerical investigated via a reactive multiphase particle-in-cell (MP-PIC) model. Gas-solid hydrodynamics and thermochemical characteristics under different percentages of CO2 in gasifying agent (mixed with air from 0 to 100 wt%) are comprehensively analyzed, in terms of the biomass conversion, bed temperature, gas species distributions, chemical reaction rates, product gas yields, lower heating value of product gas (LHVgas) and cold gas efficiency (CGE). Simulation results indicate that the CO2 percentage in gasifying agent has insignificant influence on gas–solid distribution, while it directly affects the char conversion and product gas compositions. CO2 gasification favors the CO production, increases the CO/H2 ratio in product gas and mitigates the CO2 emission. However, increasing the CO2 percentage in gasifying agent results in a decreased char conversion rate and reduced bed temperature, which restricts the use of pure CO2 as gasifying agent. The optimal CO2 percentage occurs to 60 wt% where the gasifier has the best thermochemical performance, i.e., the highest compositions of combustible gases, the largest LHVgas and CGE. This research sheds light on biomass gasification with CO2 in a large-scale CFB facility, and would be helpful for the design and scale-up of this technology.