Interaction between Coal and Biomass during Co-Gasification: A Perspective Based on the Separation of Blended Char

Co-gasification of coal and biomass is an important way to reduce the consumption of fossil fuels and achieve the efficient utilization of biomass resources. Two kinds of biomass containing corn straw (CS) and poplar sawdust (PS) were blended with different coal. Then, the coal char was separated from the blended char after co-pyrolysis based on the difference in particle size. The structural properties, including alkali and alkaline earth metals (AAEMs), microcrystalline structures, and molecular structures of the char samples were analyzed. Gasification reactivity of the char was determined by thermogravimetric analyzer (TGA). Results indicated that K and Mg contents in biomass evaporated easily and deposited on coal char, resulting in the increase in those in coal char during co-pyrolysis, and then the AAEMs contents in coal char were determined by the AAEM species and contents in biomass. Meanwhile, the inhibition effect on the graphitization degree of coal char increased with increasing blend ratio. Likewise, the inhibition effect of CS was higher than that of PS at the same blend ratio. The catalytic activity of inorganic mineral played a much more important role in predicting gasification reactivity than graphitization degree, and then the combination of alkali index and stacking layer number was proposed to better predict the reactivity of coal char.

Automated summary

Co-gasification of coal and biomass is an important method for reducing fossil fuel consumption and utilizing biomass resources efficiently. The structural properties and gasification reactivity of coal char were studied after co-pyrolysis with two different types of biomass. The results showed that K and Mg from biomass easily evaporated and deposited on coal char, leading to an increase in AAEMs content. The inhibition effect on the graphitization degree of coal char increased with increasing blend ratio, and the catalytic activity of inorganic mineral played a more important role in predicting gasification reactivity.