Sewage Sludge-Derived Producer Gas Valorization with the Use of Atmospheric Microwave Plasma

Abstract

Atmospheric microwave plasma was applied to the processing of the partially cleaned producer gas obtained from sewage sludge gasification. The plasma processing resulted in residual tar compounds conversion and changes in the gas composition. During the tests with a different gas flow rates and microwave power inputs, liquid and gaseous samples were collected to evaluate the plasma reactor's performance. The conversion efficiency ranged from 19 to 100% and it depended on the specific energy input (SEI), gas flow rate, initial tar concentration, and the nature of the tars compounds. Generally, it was shown that the conversion rate increased with the SEI and that the aliphatic, cyclic and substituted compounds were converted much easier than benzene. Moreover, applying plasma led to the production of heavier aromatics (i.e. naphthalene, indene, acenaphthylene) but the rise in their concentration was significantly smaller than the amount of converted compounds. The gas composition changes revealed in the increase of H 2 and CO concentration that was an effect of hydrocarbons and CO 2 conversion. Additionally, it was indicated that the microwave plasma reactor's performance was noticeably worse than in the case of the laboratory test with a simulated producer gas. This was mainly attributed to differences in the reactors' geometry, lower hydrogen concentration and the presence of inorganic deposit on the reactor's walls that might have inhibited microwaves transfer. In general, the microwave plasma technology seems promising in the context of cleaning and upgrading the producer gas, however, further optimization research is necessary to make it more reliable and less energy consuming. Graphic AbstractBiomass-derived producer gas treatment in the context of tar conversion is a current and important research issue. Many plasma techniques have been investigated to solve the problem of tar's presence. However, most of them considered simplified model mixtures of gas and a model tar compound. There is a negligible amount of research that applies a real producer gas obtained in the gasification process. Moreover, none of them includes microwave plasma, which has a few promising features considering producer gas valorization. Therefore, the main goal and novelty of this work were to investigate the microwave plasma treatment of the gas derived from sewage sludge gasification and to compare it with the results obtain in laboratory research using model mixtures.

Tar Removal by Nanosecond Pulsed Dielectric Barrier Discharge

“…Number of tar components-in this work 3 tar representatives were used together while in most cases only 1 or 2 are used [11,15,16,[22][23][24][25][26][27][28][29][30][31][32][33][34]. Excluding a few works performed on real biomass producer gas [9,14,21] only Kong et al [17], Eliott et al [10], Jamroz et al [12] and Yu et al [35] used at least 3 tar components, but in nitrogen, argon and oxygen as a plasmaforming gas; 3. DBD plasma with a catalyst-this has been studied by many researchers [18] and is called a one-stage configuration since the catalytic material is in contact with the plasma.…”

“…However, none of the above works was carried out in such a complex mixture which is very close to the real biomass producer gas. As was mentioned in the Introduction, only Marias et al [9], Materazzi et al [21] and Wnukowski et al [14] have tested plasma application for tar removal from real biomass producer gas. The latter gives SEI value of 5184 J/L at which almost all tar compounds were completely converted.…”

“…Its advantage is instant high gas temperature and high reactivity due to the presence of energetic electrons, ions, and radicals. The largest amount of research is related to arc, dielectric barrier, corona and microwave discharges and their combinations with catalytic materials [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. An excellent review of the application of plasma-catalyst systems for tar removal was presented in [18] and most recent [19].…”

[Retracted] Migration and Deposition Law of Pollutants in Urban Sewage Confluence Pipe Network from the Perspective of Ecology

“…Because the sewage treatment plant is generally far away from the city, the sewage transportation flow time is long, which contains C, N, P, and other pollutants in the pipeline anaerobic environment which will occur a series of physical and chemical series reactions, resulting in changes in the types, concentrations and properties of pollutants, affecting the subsequent sewage treatment process [6][7][8][9][10]. In addition, there are some problems in the sewage pipeline system, such as mixing of rain and sewage, lack of organic matter, sediment blockage, and toxic and harmful gases, which will inevitably cause environmental pollution, especially the pollution of water resources and endanger people's production and life [11][12][13]. Therefore, this paper studies the migration and deposition law of pollutants in urban sewage confluence pipe network, in order to provide ideas for the rational design of urban sewage pipe network and pipe cleaning.…”

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

“…Benzene, on the other hand, while not problematic in the context of tar condensation, is rather unwanted in the case of fuel cells or synthesis processes as it may create a carbon deposit on anodes and catalysts [32,33]. It should be noted that a more detailed description of MW plasma, its impact on syngas components, and the interaction between them are the subjects of previous works [16,30,31,34]. The results presented in this section are included due to the fact that a different gas composition was applied and a different tar surrogate was chosen when compared to previous works.…”