Numerical study of gasification pelletized municipal solid waste using multi-stage air inlet downdraft gasifier

The three-dimensional computational fluid dynamic model is used to simulate the gasification process using a modified downdraft gasifier with two levels of air inlet in the pyrolysis and partial oxidation zone. The aim of this study is to know the influence of air in pyrolysis zone to the gasification performance. Simulation arrangement using k-epsilon for turbulence model, radiation model using P1, kinetic devolatilization model using two competing rates, municipal solid waste pellet fuel is modelled as granular particles and modelled by discrete phase and multiple surface reaction model completed with finite rate/Eddy dissipation. From the simulation results, the maximum syngas composition obtained for CO, H2, CH4, CO2, and H2O was 30.85%, 16.74%, 2.25%, 0.5%, and 0.57%, respectively with LHV 5.325 kJ/kg. Air inlet at pyrolysis zone initiate the pyrolysis reaction under oxidative environment and create a new combustion zone (pyrolysis oxidative zone) with the temperature of 785°C and the partial oxidation temperature reach out 1135oC. The heat energy for the endothermal reaction (drying and pyrolysis) is obtained additional from the heat energy released by the oxidative pyrolysis zone. The modelling results from this study can be used as a reference to improve downdraft gasification performance.