Source apportionment of carbon during gasification of coal-biomass blends using stable carbon isotope analysis

Stable carbon isotope analysis, a unique analytical technique, has been utilized for distinguishing and quantifying the individual contributions of coal and biomass feedstocks in the generation of carbon containing gases during the gasification of their blends. For this purpose, corn stover (CS) and switchgrass (SG) were individually blended up to 30% by weight with two different Montana coals, namely, DECS-38 sub-bituminous coal (SB) and DECS-25 lignite coal (LG) and gasified at atmospheric pressure with varying O2/steam ratios. Gasifying at a constant O2/steam ratio while increasing percentage of biomass in the feedstock resulted in an increase of δ13C (‰) values for the carbon containing product gases. An increase in the concentration of oxygen in the feed stream at a constant biomass percentage leads to the depletion of 13CO and enrichment of 13CO2 in the blends with corn stover while an enrichment of both 13CO and 13CO2 was observed in blends with switchgrass. Based on isotope mass balance considerations, the contribution of corn stover was in the range of 1% - 40% for CO generation and 6% - 69% for CO2 generation. Switchgrass, on the other hand, contributed up to 53% for CO generation and only 46% for CO2 generation.