Syngas production from municipal solid waste with a reduced tar yield by three-stages of air inlet to a downdraft gasifier

Municipal solid waste is potentially converted into gaseous fuel through gasification. Tar, the by product, must be reduced to a minimum. In this study, tar was suppressed by applying multi-stage downdraft gasifier with three air inlets in the zone of pyrolysis, oxidation, and reduction in which the whole air for the entire zone was regulated at 21.12 kg/h according to the equivalent ratio (ER) of 0.4. Fixed equivalent ratio was used as a benchmark for single stage numerous air ratios for the three zones were investigated used to obtain optimum performance. The optimum ratio was found to be 10:80:10. LHV and CGE were increased as the increase in CO, H₂ and CH₄ concentrations which were triggered by the increase in temperature and the increased rate of the reaction that produces the gas. Char and air oxidation reactions not only occurred in the partial oxidation zone but also occurred in the pyrolysis and reduction zones or the oxidative pyrolysis and heterogeneous oxidation reactions so that the layers of hot zones increased. Tar passed the larger hot zones was favorable for the thermal cracking of tar. Pyrolysis temperature rose of from 449 °C to 521 °C and energy neutral point has been reached so that changes like endothermic be exothermic. The air in the reduction zone activated the char layer to be more reactive. Improved performance multi-stage air inlet as compared with single stage gasifier can be used as a reference in the optimization of operating parameters for the wider applications of further MSW gasification.