Carbon dioxide assisted co-pyrolysis of coal and ligno-cellulosic biomass

Abstract

This work mechanistically investigated the influence of CO2 in co-pyrolysis of sub-bituminous coal and main constituents of ligno-cellulosic biomass (cellulose and hemicellulose). Our experimental work identified the crucial role of CO2 in co-pyrolysis of coal and biomass. For example, CO2 not only enhanced the thermal cracking behavior of VOCs evolved from the thermal degradation of a carbonaceous solid sample (i.e., sub-bituminous coal, cellulose, and xylan) via blocking the addition reaction, but also directly reacted with VOCs and CO2. The genuine effects induced by CO2 led to a significant reduction of condensable hydrocarbons (i.e., tar), which directly lead to a significant enhancement of syngas production and modification of ratio of CO to H2: the ratio of CO to H2 was increased approximately ∼1200% at 680°C in pyrolysis of coal in the CO2 environment and the ratio of CO to H2 was adjustable by means of using a different amount of CO2 during the pyrolysis process of carbonaceous samples. Furthermore, the identified role of CO2 would be applicable to the in-situ air pollution control in various industrial applications, such as steelworks. Lastly, the identified role of CO2 in pyrolysis will be applied in the gasification process since pyrolysis is the intermediate step for the gasification process.