Tar and CO2 removal from simulated producer gas with activated carbon and charcoal

Steam gasification of biomass produces gases such as CO, CO2, H2, CH4, H2O, C2–C5 hydrocarbons, tars (aromatic hydrocarbons), NH3, HCN, and H2S, which are commonly known as producer gas. To produce liquid fuel, CO2 and tars have to be removed from the producer gas. The CO2 can be converted into a useful product such as CO using the reverse Boudouard reaction (CO2 + C ↔ 2CO). Tars can be removed in the presence of carbon by adsorption. Using simulated producer gas flow, reactor studies (200 °C–950 °C) of the reverse Boudouard reaction and the adsorption of toluene and ethylene, tar surrogates, were conducted with different commercially activated carbon and mesquite charcoal. The study showed that the reverse Boudouard reaction is limited by kinetics. The concentration of CO from the reverse Boudouard reaction approaches equilibrium with increase in temperature and residence time. The adsorption of the tar surrogate toluene in the presence of carbon at lower temperature of 200 °C–300 °C is a useful removal mechanism.

► Producer gas is produced during biomass gasification, which has CO2.
► CO2 is converted to CO using carbon by the reverse Boudouard reaction.
► The reverse Boudouard reaction is limited by kinetics.
► Carbon was also used to adsorb toluene tar surrogates.
► Toluene in the producer gas was adsorbed at temperatures of 200 °C–300 °C.