Biomass and coal cofiring gasification with pre-combustion carbon capture: Impact of mixed feedstocks on CO2 absorption using a physical solvent

Abstract

Advances in co-gasification of coal and biomass are resulting in more interest in poly-generation facilities that can produce hydrogen rich syngas for producing chemicals, fuels and energy, with much lower carbon emissions. When biomass is blended with hydrocarbon feedstocks like coal (biomass cofiring) and when the carbon dioxide (CO₂) produced during the gasification process is captured using pre-combustion CO₂ capture technologies, it is possible to emit less CO₂ into the atmosphere than it took to grow the biomass material, resulting in net negative or low CO₂ emissions.

Here, we present the first carbon capture pilot plant data for CO₂ removal from coal and biomass derived syngas using physical solvent absorption. The physical solvent (DEPG at 35.0 L·h⁻¹ and 10.5 °C) was tested in a packed absorption column under pre-combustion CO₂ capture conditions using the biomass derived syngas mixtures (3.54 MPa at 3.4 std. m³·h⁻¹ and 53.1 °C) to assess any changes in the absorption process resulting from co-gasification. Overall, the CO₂ absorption performance of the solvent did not appear to be impacted by the varying feedstock compositions as indicated by average CO₂ removal efficiency of 97.3 % with a standard deviation of 1.6 % across all trials. Despite minor accumulation of organic gas species in the solvent and gas streams exiting the absorber, there did not appear to be any strong correlations between CO₂ capture performance and coal type or biomass type or mixture concentration. These results indicate traditional physical solvent absorption processes can be used with minimal impact from novel gasification feedstock mixtures including coal, wood and corn stover mixtures, but longer term testing is recommended to fully assess the impact of accumulating inorganic and organic species from biomass feedstock.