Abstract
Tar removal is one of the greatest technical challenges of commercial gasification technologies. To find an efficient way to destroy tar with plasma, a rotating gliding arc (RGA) discharge reactor equipped with a fan-shaped swirling generator was used for model tar destruction in this study. The solution of toluene, naphthalene and phenanthrene is used as a tar surrogate and is destroyed in humid nitrogen. The influence of tar, CO2 and moisture concentrations, and the discharge current on the destruction efficiency is emphasized. In addition, the combination of Ni/γ-Al2O3 catalyst with plasma was tested for plasma catalytic tar destruction. The toluene, naphthalene and phenanthrene destruction efficiency reached up to 95.2%, 88.9%, and 83.9% respectively, with a content of 12 g/Nm3 tar, 12% moisture, 15% CO2, and a flow rate of 6 NL/min, whereas 9.3 g/kW·h energy efficiency was achieved. The increase of discharge current is advantageous in terms of decreasing black carbon production. The participation of Ni/γ-Al2O3 catalyst shows considerable improvement in destruction efficiency, especially at a relatively high flow rate (over 9 NL/min). The major liquid by-products are phenylethyne, indene, acenaphthylene and fluoranthene. The first two are majorly converted from toluene, acenaphthylene is produced by the co-reaction of toluene and naphthalene in the plasma, and fluoranthene is converted by phenanthrene.
Highlights
Owing to the rapid consumption of fossil fuels and increasing emphasis on environmental issues, the use of biomass and municipal solid waste (MSW) as alternative fuel has received considerable attention
The destruction efficiency decreases of g/Nm and phenanthrene were dissolved in toluene with a mass ratio of 1:1:20
Results and Discussions naphthalene destruction, where the destruction efficiency has a high value at a tar concentration of 20 g/Nm3
Summary
Owing to the rapid consumption of fossil fuels and increasing emphasis on environmental issues, the use of biomass and municipal solid waste (MSW) as alternative fuel has received considerable attention. The traditional methods for the removal or destruction of tar can be categorized into (i) mechanical separation (by Venturi scrubbers, water scrubbers, electrostatic precipitators (ESPs), rotational particle separators, or cyclones), which is unattractive since it causes secondary pollution and wastage of chemical energy contained in tar while shows low efficiency in tar removal [1,15,16]; (ii) thermal cracking, which normally requires 1250 ◦ C and takes a few seconds to get good results, and has the drawbacks of high cost and production of heavier products and agglomerated soot particles [17,18]; (iii) and catalytic cracking, which enables obtaining higher yields of valuable H2 and CO but has a significant limitation on the catalyst lifetime [2]. There is a lack of data for the study of multi-component tar, especially having a substance with more than two benzene rings For this reason, a toluene solution of naphthalene and phenanthrene as simulated tar is used to investigate the reaction of tar compounds in the RGA reactor. Phenanthrene were dissolved in toluene with a mass ratio of 1:1:20
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