Simulation of air gasification of Napier grass using Aspen Plus

Abstract

In this research, a thermodynamic equilibrium model was developed using Aspen Plus for parametric study of syngas composition and product yield from air gasification of Napier grass in a fluidized bed gasifier. Operating conditions of gasification encompassing temperature, pressure, equivalence ratio (ER), and moisture content were manipulated and studied with further validation against experimental data. Tar cracking reaction was considered with M-cresol and heptane as represented species. Conversion of homogenous reactions was empirically correlated in MATLAB and further utilized to adjust the composition of CO, H2 and CH4 for prediction of experimental data with better accuracy, where the average mean error ranges from 0.20 to 0.25. Maximum lower heating value (LHV) was attained at 750 °C, contributed by the highest CH4 composition. ER change had limited effect on bioliquid yield but showed a significant contribution in lowering biochar yield. Lowering moisture content improved syngas quality significantly through the promotion of CO, H2 and CH4 production, with minimum biochar and bioliquid yield. The optimized LHV were 7.69 MJ/Nm3 at T = 750 °C, ER = 0.2 and moisture content of 4.5 wt%.