Modelling and statistical analysis of plastic biomass mixture co-gasification

Abstract

In this work, an Aspen Plus model was developed to study the plastic/biomass co-gasification thermodynamically. Tar inclusion and temperature restricted equilibrium approach were applied for model modification. Using different gasifying agents, it was found that steam co-gasification is superior to air and oxygen-gasified processes in terms of gas composition and lower heating value (LHV). The use of an oxygen/steam mixture enhances H2 production if the steam to fuel ratio (S/F) is kept low. The modelling results were integrated with Response Surface Methodology to study the impacts of temperature (T), steam to fuel ratio (S/F), and plastic to biomass ratio (P/B) and their interactions within the steam co-gasification process. It was found that T and S/F, and their interaction, are the most influential parameters. Increasing the T, S/F, and P/B was favourable for enhancing H2 production, gas yield (GY), and carbon conversion efficiency (CCE), while CO content and LHV can be negatively affected. Using ANOVA results, empirical correlations were derived for estimating the responses (H2, CO, CO2, CH4, LHV, GY, and CCE). The optimum condition obtained using the desirability function (DF) approach was T = 921 °C, S/F = 1.186, and P/B = 74.99, at which the overall desirability function was found to be DF = 0.9.