Muktar Bashir
Aston University, UK
Title: Modelling of steam gasification of char in a circulating fluidised bed
Biography
Biography: Muktar Bashir
Abstract
Biomass is a renewable source of energy with huge potential to replace or supplement conventional fosil fuels. Biomass gasification is a thermal conversion process to produce fuel or chemicals in the presence of a gasifying medium, mainly air, steam or air/steam mixture. The main challengies in this process is the presence of tar (heavy hydrocarbons) in the product gas, especially at low temperatures. The tar can be thermally cracked at high temperature (>1000 ºC) or catalytically reformed at lower temperature to produce a high quality fuel gas. Biochar, which is a pyroduct from biomass pyrolyis, has been reported to contribute to catalytic cracking of the tar in the presence of steam and carbon dioxide. In this study, steam gasification of biochar has been theoretically incvestigated to predict the product gas quality and to better undestand the extent of tar cracking in the presnece of biochar. The gasification was simulated in a circulating fluidised beds using a three-dimensional computational fluid dynamics (CFD) model based on two-fluid flow (Eulerian-Eulerian) approach and solved using the commeroial software FLUENT. The devolatilisation and heterogeneous gasification reactions have been implemented in FLUENT using in-house developed user-defined function (UDF). To allow for compartive analysis, the simulation was carried out with and without the inclusion of the tar reforming reactions. It has been found that the tar can be significantly reduced when taking into consideration the biochar catalytic effect, even at a reactor temperatuure well below the recommnded range for standard biomass gasification.
