A comparative investigation of kinetics of biomass steam gasification using a pre-validated model

The present work investigated the kinetics of major biomass gasification reactions from a modelling point of view. A pre-validated Aspen Plus model was employed to evaluate the reactions with MATLAB used as a post-processor. Different combinations of char gasification and the water-gas shift (WGS) reactions were paired and compared with experimental data from pilot gasifiers. A variety of bed materials, namely silica sand, olivine, and a mixture of olivine/calcite, were considered to assess each reaction pair for their effectiveness. Tar conversion via steam reforming and thermal cracking was modelled using a semi-empirical approach from literature. Product gas characteristics and its sensitivity to temperature variation, as well as the energy performance of the gasifier, were used as the comparison yardsticks. Five experimental case studies were employed to validate the simulation results. Our investigations demonstrated that a few of the reaction pairs (combined WGS reaction and char gasification) can be effectively linked with the catalytic behaviour of bed material. Nevertheless, a tar conversion mechanism proved critical in the validation process, thereby impacting the main findings. The results from this study helps address a long-standing issue regarding the simulation of biomass gasification by providing categorised kinetics of main reactions for various gasification conditions.