Plasma-assisted decomposition of a biomass gasification tar analogue into lower hydrocarbons in a synthetic product gas using a dielectric barrier discharge reactor

Abstract

Cleaning product gas from biomass gasification is one of the major challenges for the application of biomass as a renewable energy source for power generation and value-added chemical synthesis. Non-thermal plasmas are a novel alternative technology for decomposing such tar compounds. In this research, the use of a dielectric barrier discharge (DBD) reactor was investigated for the decomposition of toluene (a tar surrogate) in a synthetic product gas containing H2, CO and CO2. The effect of residence time (0.95–2.82 s), plasma power (5–40 W), concentration (20–82 g/N m3), and temperature (ambient −400 °C) were investigated. It was demonstrated that the percentage removal of tar increased with increasing plasma power and residence time. 99%+ removal of toluene was observed at a plasma power of 40 W (the highest power used) and a residence time of 2.82 s (the highest residence time used). At ambient temperature, the toluene decomposition products include CO, lighter hydrocarbons, and solid residue. Unfortunately, at low temperatures, there was substantial solid residue formation. The synergetic effect of temperature and plasma was investigated to determine whether it could decrease residue formation. It was found that the solid residue completely disappeared at 400 °C. Furthermore, the selectivity and the yield of lower hydrocarbons increased with operating temperature. However, the yield of CO decreased due to the termination of radicals through the combination of CO and O at higher temperatures. Overall, this work demonstrates that toluene can be almost completely converted to smaller molecules by a DBD non-thermal plasma, and that a degree of control can be established by varying power, residence time and temperature, including eliminating the problem of solid residue formation.