The Reactivity and Kinetics of Yanzhou Coal Chars from Elevated Pyrolysis Temperatures During Gasification in Steam at 900–1200°C

This paper studied on the steam gasification reactivity and kinetics for Yanzhou coal chars prepared at elevated pyrolysis temperatures, using a fixed-bed reactor at the atmospheric pressure and gasification temperature ranging from 900°C to 1200°C. The following conclusions were reached mainly. The effect of gasification temperatures on the gasification reactivity was stronger than that of pyrolysis temperatures under the condition of elevated pyrolysis temperatures. Changes of reaction rate and surface area had a similar trend, but the relationship between the change of surface area and that of reaction rate was not proportional during the reaction process. While simulating the steam gasification reaction of Yanzhou coal chars at the temperatures of 900–1200°C, the shrinking un-reacted core model (SUCM) was superior to the volume reaction model (VRM) and the reaction–diffusion model based on the shrinking un-reaction core model was more favourable, which suggested that the diffusion had an effect on the reaction process, but its effect was not rather strong. Therefore, it may be considered that the reaction process was mainly controlled by the chemical reaction. Apparent activation energies obtained for the steam gasification of Yanzhou coal chars ranged from 127.17 kJ mol−1 to 196.55 kJ mol−1. Moreover, it was also found that kinetic parameters were in accord with the isokinetic relationship, according to which the calculated isokinetic temperature for all the reactions was 1197°C.