Tar Removal by Nanosecond Pulsed Dielectric Barrier Discharge

Abstract

Featured Application: Biogas and biomass producer gas cleaning.Abstract: Plasma-catalytic reforming of simulated biomass tar composed of naphthalene, toluene, and benzene was carried out in a coaxial plasma reactor supplied with nanosecond high-voltage pulses. The effect of Rh-LaCoO 3 /Al 2 O 3 and Ni/Al 2 O 3 catalysts covering high-voltage electrode on the tar conversion efficiency was evaluated. Compared to the plasma reaction without a catalyst, the combination of plasma with the catalyst significantly enhanced the conversion of all three tar components, achieving complete conversion when an Rh-based catalyst was used. Apart from gaseous and liquid samples, char samples taken at five locations inside the reactor were also analyzed for their chemical composition. Char was not formed when the Rh-based catalyst was used. Different by-products were detected for the plasma reactor without a catalyst, with the Ni-and Rh-based catalysts. A possible reaction pathway in the plasma-catalytic process for naphthalene, as the most complex compound, was proposed through the combined analysis of liquid and solid products. electron density and energy, plasma homogeneity, simple design and operation, capacity to induce reactions at relatively ambient temperature, atmospheric operational pressure, and very low level of coke production [20]. The novelty of this work lies in the combination of four problems that have so far been studied independently or in a smaller combination, i.e.,: Appl. Sci. 2020, 10, 991 A typical voltage pulse is presented in Figure 2. It does not depend on the reactor geometry, condition of the dielectric barrier, presence of catalysts, or gas composition. Its half-measured width is 9 ns, which ensures fast energization of electrons and inhibits their thermalization. This way, energy delivered to the discharge is not wasted in gas heating but consumed by electrons and further the production of radicals via electron-induced dissociation of molecules.

The Effect of Packing Material Properties on Tars Removal by Plasma Catalysis

“…Finally, gaseous as well as solid compounds identified in the FTIR spectra based on detailed analysis of functional groups were confronted with the compounds reported as by-products in the works of other authors related to naphthalene decomposition by plasma and plasma catalysis [24,33,35,36,40,44,93,[100][101][102][103][104]. The comparison showed a good match and supported our findings.…”

“…Indeed, several discharges have been employed and investigated in the naphthalene removal process by plasma catalysis: corona discharge [35,36], dielectric barrier discharge (DBD) [37][38][39][40][41][42][43], gliding arc discharge [44,45], and even plasma jet [46]. The discharges have been combined with several catalytic materials, most frequently with Ni-based catalysts (Ni/γAl 2 O 3 [37,38,40,44], Ni/ZSM-5, Ni/SiO 2 [41] and Ni/Co-based catalyst [45]) due to their availability and selectivity towards formation of syngas constituents in catalytic processes [23]. However, their high activities are obtained only when operated at elevated temperatures (>780 • C) [47].…”

“…However, their high activities are obtained only when operated at elevated temperatures (>780 • C) [47]. Besides Ni-based catalysts, other materials have also been investigated in a plasma catalytic process of naphthalene removal, including MnO 2 [35], γAl 2 O 3 [36], Rh-LaCoO 3 /Al 2 O 3 [40], TiO 2 /diatomite [43], and Pt/γAl 2 O 3 [46].…”

Warm Plasma Application in Tar Conversion and Syngas Valorization: The Fate of Hydrogen Sulfide

“…26%, 9%, and 22%, respectively. A high lack of hydrogen and oxygen is caused by the presence of steam, which was not analyzed, but was produced according to reaction (7). The lack of carbon is due to the presence of olefins (mostly acetylene) and hydrogen cyanide.…”

“…Being electricity-sourced devices, plasma setups allow for a quick ON and OFF procedure and flexible control of the process parameters. The most common plasma techniques investigated for tar conversion are: corona discharge [5,6], dielectric barrier [7][8][9], arc plasma [10], gliding arc plasma [11][12][13][14][15], and microwave (MW) plasma [16,17]. Among them, gliding arc plasma and microwave plasma have been subjected to quite intensive investigation in recent years.…”