Study on CO2 gasification reactivity of biomass char derived from high-temperature rapid pyrolysis

Three biomass chars, corncob char (CC char), palm shell char (PS char) and soybean straw char (SS char), prepared at different pyrolysis temperatures (1073 K, 1273 K and 1473 K) under nitrogen atmosphere, the gasification characteristics of which were studied at different heating rates by means of non-isothermal thermogravimetric method. Effects of biomass type, pyrolysis temperature on chemical component, morphologic structure, carbonaceous structure of char, and further on gasification characteristics were investigated. Results showed that the order of gasification reactivity of these three chars from high to low was SS char, CC char, and PS char. With the increase of pyrolysis temperature, gasification reactivity of char decreased. The gasification properties of char were determined by carbonaceous structure, which meant the gasification reactivity decreased with the increase of the uniformity of carbonaceous structure. Three nth-order representative gas-solid reaction models, random pore model (RPM), volume reaction model (VM), unreacted core model (URCM) were applied to describe the reactive behavior of chars. A marked compensation effect exists in the gasification reaction of different chars. Concluded from kinetics analysis that the RPM performed best, of which, the activation energies lay in the range of 183.1-263.4 kJ/mol.