Experimental and modeling studies on CO2 gasification of biomass chars

The CO2 gasification properties and kinetics of biomass chars including four kinds of herbaceous residues and two kinds of wooden residues have been studied by the method of isotherm-gravimetric analysis. In addition, the chemical components as well as physical structures of six chars were systematically tested. Results show that gasification reactivity of herbaceous residue char were better than that of wooden residue char. It was found that gasification reactivities of char were mostly determined by its carbonaceous structure. Four kinetic models were applied to describe the gasification behavior of biomass chars: the volumetric model (VM), the grain model (GM), the random pore model (RPM) and the modified random pore model (MRPM). It was found that the RPM and MRPM model were better for describing the reactivity of different chars. However, for the gasification process in which the peak gasification rate appears in high conversion range, the MRPM performs better. At the same time, a marked compensation effect was also presented between the activation energy and pre-exponential factor when the Arrhenius law was used to describe the temperature dependence of gasification rate of char.