Experimental and modelling studies on combined pyrolysis and gasification of large coal particle in steam and CO2 ambience

The single-particle combined pyrolysis and gasification characteristics of Indian sub-bituminous coal in the presence of steam and CO2 is investigated separately in a custom-made reactor under isothermal condition (800 to 950 °C). A comprehensive transient model consists of two sub model—coal devolatilization and residual char gasification have been developed incorporating heat and mass transport limitations. The combined model is validated against the present experimental findings along with that reported in the literature. The major components of evolved volatiles during pyrolysis are CO2, CO, H2O, H2 and CH4 is measured quantitatively using Gas Chromatography (GC) with the corresponding values of 0.0562, 0.063, 0.0723, 0.4015 and 0.4068, respectively. The maximum rates of devolatilization are found to be 9.16 × 10–6, 1.06 × 10–5 and 1.33 × 10–5 kg/s, whereas the maximum gasification rate values are 1.22 × 10–7, 1.79 × 10–7 s and 2.60 × 10–7 kg/s at a respective reactor temperature of 800, 850 and 900 °C. The simulation is carried out to predict the reaction rate and time of devolatilization, and also the gasification rate, product gas (CO2, CO, H2) compositions and the particle temperature during gasification.