Steam reforming of toluene and naphthalene as tar surrogate in a gliding arc discharge reactor.

Steam reforming of mixed toluene and naphthalene as tar surrogate has been investigated in an AC gliding arc discharge plasma, with particular emphasis on better understanding the effect of steam and CO2 on the reaction performance. Results show that H2, C2H2 and CO are the major gas products in the plasma steam reforming of tar for energy recovery. The addition of a small amount of steam remarkably enhances the conversions of both toluene and naphthalene, from 60.4% to 76.1% and 57.6% to 67.4%, respectively, as OH radicals formed by water dissociation create more reaction pathways for the conversion of toluene, naphthalene and their fragments. However, introducing CO2 to this process has a negative effect on the tar reforming. Optical emission spectroscopic diagnostics has shown the formation of a variety of reactive species in the plasma process. Trace amounts of monocyclic and bicyclic aromatic condensable by-products are also detected. The destruction of toluene and naphthalene can be initiated through the collisions of tar surrogates with energetic electrons, N2 excited species, OH and O radicals etc. Further optimization of the plasma tar destruction is still needed because the complexity of the tar component in a practical gasifier could decrease the tar conversions.