Numerical Analysis of Heterogeneous Oxidation Reaction on Multi-stage Air Inlet Downdraft Gasifier

Gasification technology is one of the thermochemical conversion methods that can be a solution to overcome the negative municipal solid waste (MSW) impact. Syngas application from gasification on the internal combustion engine has problems with tar content. one method for reducing tar content is by means of a multi-stage air inlet in the reduction zone to initiate heterogeneous oxidation reactions. In this study a three-dimensional computational fluid dynamic model was used to simulate gasification reactions. The simulation was carried out using a one-phase model with k epsilon turbulence model, P1 radiation model, devolatilization model using kobayashi model, MSW fuel modeled as a discrete phase that moves in the continuous phase, and the reactions that occur are volumetric and particle surface reaction in which the interaction of turbulence-chemistry using finite-rate/eddy-dissipation. The ratio of air used is 10%, 20%, 30%, and 40% between oxidation and reduction. Based on the simulation results, there is an increase in syngas composition, especially CO because there is a heterogeneous oxidation reaction between carbon in the reduction zone with oxygen which also triggers a rise in temperature in the oxidation zone. CO2 concentration decreases due to an increase in the rate of boudouard reaction. but when the amount of air continues to increase there is a decrease in temperature in the oxidation zone because the amount of air for the oxidation reaction decreases, the simulation results obtained can be used to optimize the downdraft gasifier by adding air input to the reduction zone.