PhD ThesisIn this project, a non-thermal plasma dielectric barrier discharge (“DBD”) reactor was used to
reduce the concentration of tar in the product gas, and its performance was evaluated at
different reaction conditions. Toluene and benzene were used as tar model compounds. The
effects of reaction parameters such as the residence time, concentration, wall temperature and
plasma power on tar removal were studied in a tubular dielectric barrier discharge (DBD)
plasma reactor at ambient pressure. The percentage removal of tar increased with increasing
plasma power and residence time to as high as 99% in various carrier gases (CO2, H2, and N2)
and gas mixtures. However, the decomposition of tar analogue compounds decreased with
increasing concentration. It was found that most of the toluene converted into solid residue
due to the polymerization of hydrocarbon radicals produced in the plasma system at ambient
temperature in all carrier gases (CO2, H2, N2, and mixtures). The other products were lower
hydrocarbons, CO, and H2, depending upon the type of carrier gas. The synergetic effect of
power and temperature was investigated to decrease the unwanted solid deposition. It was
observed that selectivity to lower hydrocarbons increased to 99% at 400 oC and 40 W, with
the non-thermal plasma. In these conditions solid formation was completely prevented. The
maximum selectivities to methane were 60 % and 81% for toluene and benzene, respectively.
However, in other carrier gases (N2 and CO2), the selectivity did not increase beyond 15 %,
even with increasing temperature, and solid formation was observed even at elevated
temperatures. However, in the gas mixtures, solid formation was significantly reduced when
increasing the temperature due to presence of H2. Therefore, the plasma power and
surrounding temperatures can be used to control the product distribution in the presence of H2
carrier gas
