Studying the Effect of Pyrolysis Gas Composition on the Gasification Syngas Composition using CPFD Simulation

Abstract

A CPFD model for biomass gasification in a bubbling fluidized bed was developed using the Barracuda Virtual Reactor 17.4.1 commercial CFD code. Three simulation cases were performed at varying the reactor temperature and pyrolysis gas compositions. The effect of the pyrolysis step was found to be significant, especially on the production of CO, H2, and CH4. This is mainly because that the pyrolysis step converts 85% of the biomass weight into volatiles. Comparing the simulation results with the experimental data showed a good agreement on predicting CH4 and H2, whereas CO2 was overestimated, and CO was underestimated. This might be due to inaccuracies in the pyrolysis gas composition or high rates in the water-gas-shift reaction used in the simulation. The effects of temperature on the synthesis gas composition were further investigated. Increasing the temperature from 800°C to 900°C, increased the concentration of CO and H2 by 2.4% and 1.6% respectively, while decreased the concentration of CO2 and CH4 by 1.3% and 0.5%, respectively. The trends of gas compositions showed a good agreement with other literature data, except the trend of CH4. This might be due to the neglect of tar composition in the volatiles.