Gasification kinetics of Barapukurian coal char using carbon dioxide and steam reactants

Abstract

Gasification of coal is a cost-effective and sustainable technology to produce syngas and hydrogen with integrated carbon capture and storage system. This study investigates the gasification characteristics of Barapukurian bituminous coal (BBC) char under carbon dioxide (CO2) and steam atmosphere using a thermogravimetric analyser (TGA). The char was prepared through a rapid pyrolysis process in a high temperature entrained flow gasifier at a temperature of 1200 °C. TGA experiments were conducted under atmospheric pressure over 700–1200 °C. Factors affecting intrinsic gasification kinetics, such as diffusion and mass transfer limitations, were optimised before conducting TGA experiments at various temperatures. Three established kinetic models of the volumetric model (VM), grain model (GM) and random pore model (RPM) fitted well with the experimental data. The activation energy determined from CO2 gasification was 1.20–1.25 times higher than that of steam gasification, indicating a higher reactivity under steam than CO2. The order of reaction using CO2 and steam was determined to be 0.67 and 0.95 at 900 °C. Graphical abstract

Gasification of Solid Fuels (Coal, Biomass and MSW): Overview, Challenges and Mitigation Strategies

“…The gasification performance vastly depends on the reactivity of coal/biomass/MSW char. For example, the reactivity of coal/biomass/MSW determines the degree of recycling and size and configuration of the gasifier, which subsequently dominates the oxidant requirement and overall system performance [98,99]. However, the reactivity of char is not constant for coal with a specific rank or biomass but varies with their physical and chemical properties [100].…”

“…The alkali and alkaline earth materials (AAEM) present in the ash helps to catalyse the char reactivity [79,83,84]. However, the inorganic ash minerals may have an adverse effect if they melt and sinter in the pores of char particles [99]. Micropores blocked by ash minerals prevent the gasification reagents from accessing the active sites of the char, resulting in a lower reactivity [83].…”

“…Whilst considering the effect of fuel properties, there is no general trend on the gasification reactivity based on the coal rank [102]. Generally, lower-rank coal possesses higher reactivity than higher-rank coal due to the higher proportion of oxygen-containing functional groups, micropores, and greater dispersion of catalytic inorganic compounds [99,103].…”

“…Studies conducted by different authors [66,67] reported that the reactivity of lowerrank coal is much higher than that of higher-rank bituminous coal, which increases with increasing temperature, as shown in Figure 3. [99,103].…”

“…The following generic formula can be used to express the immediate carbon-conversion rate during gasification [99,107]:…”