oa Impacts of Feeding 100% Biomass on Gasifier Performance and Precombustion CO2 Capture

For pressurized gasification, precombustion CO2 capture requires less energy and smaller equipment than does amine-based postcombustion CO2 capture. However, equipment and processes that have been designed and validated on coal-fired gasification may not operate as expected when converting to biomass-fired gasification. Pilot-scale tests on cofiring biomass with various ranks of coal showed that behavior was nonlinear, meaning that performance when firing 100% biomass cannot be predicted by extrapolating from trends with increasing blend ratios of biomass in coal. Operating at lower pressures with tar cracking helped with stable feeding and operation when gasifying 100% biomass but also reduced CO2 capture and thermal efficiencies. Measurements of major tar compounds in the syngas, CO2 capture solvent, and product gas streams revealed that gasification with different feedstocks and at different conditions leads to changes in how tar accumulates and then partitions to various downstream processes. Results from the pilot-scale testing were used to construct accurate Aspen models that could be scaled for economic and lifecycle analysis under various operating assumptions.