Characterization of tar evolution during DC thermal plasma steam gasification from biomass and plastic mixtures: Parametric optimization via response surface methodology

Abstract

Thermal plasma gasification has stimulated much recent interest for lower tar content, higher syngas yield, and more efficient energy utilization than conventional gasification. This context evaluated the influences of operating conditions (input power, the high-density polyethylene (HDPE) content, and steam/carbon (S/C) ratio) on tar evolutions during the plasma co-gasification of wood sawdust and HDPE. The single-factor analysis reveals that the increase in input power has a positive influence on the reduction of tars (from 1.13 g·Nm−3 to 0.84 g·Nm−3) and the conversion from light tars to heavy tars, simultaneously. The experimental tar concentrations at the HDPE proportion of 60% and 80% are 1.01 g·Nm−3 and 0.93 g·Nm−3, respectively, lower than the theoretical values, indicating a synergistic effect between wood sawdust and HDPE. The tar concentration shows a turbulent variation between 0.87 g·Nm−3 and 2.76 g·Nm−3 with the S/C ratio increasing. The light/heavy PAHs are the dominant compounds in the tars from plasma gasification and little phenols or furans are found in the components of tars. By using response surface methodology (RSM), a regression model between the three independent parameters and responses is gained and can effectively predict experimental results. According to this model, a minimum tar concentration of 0.54 g·Nm−3 can be obtained under the optimal conditions, which is comparatively lower than that from conventional gasification (1–100 g·Nm−3).