CO₂ conversion to CO by fluidized bed biomass gasification: Analysis of operational parameters

Abstract

Thermochemical conversion of CO₂ with biomass to CO in fluidized bed gasifiers is promising for a sustainable carbon economy. Knowledge about this process is expanded by investigating experimental parameters influencing CO₂ conversion in such a system and combining them to demonstrate effective conversion. Wood char and CO₂ are fed to a lab-scale gasifier in 53 semi-continuous experiments. Six experimental parameters are varied: temperature, bed material type, initial bed-to-fuel ratio, initial fuel loading in the reactor, feed CO₂ flow rate, and fuel particle size. The results are compiled in a semi-empirical model based on reaction kinetics. High temperatures and high fuel-gas contact times are favorable for increasing CO₂ conversion, with the latter achieved through high initial fuel loadings in the reactor and low feed gas flow rates. Choosing olivine instead of silica sand as a bed material also results in higher CO₂ conversions. The highest CO₂ conversion demonstrated in this paper is 86.1%. This experiment produces a gas with 82.75% CO, 10.01% H₂, and 5.90% CO₂ (nitrogen-free and dry).