Process Simulation of Fixed Bed Downdraft Gasifier for Rice Husks and Sawdust

The objective of the research was to figure out the performance of a fixed bed downdraft gasifier fed by mixtures of rice husk and sawdust using Aspen Plus simulation and to compare to the present work. The gasification model was applied with varying equivalence ratio, i.e., 0.23 to 0.35. The characteristics of the gasification temperature, syngas composition of CO, H2, CO2 and CH4 and the Lower Heating Value (LHV) were observed and studied. In addition, the mixtures of rice husk and sawdust fed by gasifier reactor model are analyzed. As seen from the comparison of simulation results and the referenced ones, the value of syngas composition in are comparable. The average deviation of CO and CH4 contents is slightly higher than the referenced ones. Meanwhile, the average deviation of H2 and CO2 contents are slightly lower than the referenced ones. Also, the simulation results showed that in the range of gasification temperature of 800-1000 ⁰C, the content of CO increased while the compositions of CO2 and CH4 decreased. In addition, the composition of H2 reached its peak at the temperature of 900 ⁰C. As a consequence, the measure calorific value of syngas reached its peak when the temperature and Equivalence Ratio (ER) were applied at 900 ⁰C and 0.3 respectively. Also, the added volume ratio of sawdust on rice husk resulted in an encroachment on the calorific value of syngas. It also increased the content of CO and H2 and decreased the content of CO2 and CH4. These conditions showed that variating mixture of sawdust ratio would optimize the quality of syngas.