Product distributions from isothermal co-pyrolysis of coal and biomass

Abstract

Co-gasification and co-pyrolysis of coal and biomass are being studied as a means to reduce the carbon footprint of an IGCC plant. Co-feeding creates many challenges in the thermochemical conversion of coal/biomass such as the variable nature of biomass feedstocks, potential nonlinear reaction rate effects during conversion and the varying composition of the products. An experimental study on isothermal co-pyrolysis of Illinois #6 coal and switchgrass was done in a drop reactor at 900°C to investigate the effects of co-feeding on pyrolysis product distributions under conditions relevant to transport gasifiers. Coal/biomass mixtures were fed to the reactor in feed ratios of 100/0, 85/15, 70/30, 50/50, and 0/100, while primary gaseous products (CO, CO2, CH4, H2 and H2O) were monitored and analyzed online. Ultimate analysis of solid and liquid products is used to track the distribution of the feedstocks’ elements and energy content into its pyrolysis products, while GC–MS and ash elemental analyses are provided to more fully characterize these products. Experimental results show that under the conditions studied, product distributions do not display any non-linear effects, and can be estimated as a mass-weighted sum of the product distributions of the pure feedstocks. This result is likely due to the higher temperatures used in this study, though it is inherently useful in the development of higher-temperature gasification systems.