| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 97 === Custom-made atmospheric argon (Ar) micro-plasma system was employed to decompose dimethyl sulfide (DMS) into non-foul smell species. They were thereafter trapped by scrubber or solidification treatment to avoid spreading from the factory to the atmosphere. The as-designed system takes the advantages of low energy consumption, operation in atmospheric condition, short treatment time. In this study, the decomposition mechanism and efficiency were respectively discussed.
In the experiments, the compositions of argon plasma, reactants, and products were characterized using optical emission spectrometer and various gas-phase analyzers. Argon plasma contained excited species such as Ar*, O*, OH*, and e-. From the experimental results, DMS, with a concentration of 400 ppm mixed with argon plasma, was decomposed within the treatment time of 6.7 × 10-4 sec and converted into other excited species such as C*, C2*, CN*, CO*, and CH*. When gaseous products were away from the treatment system, the existing excited species tended to be recombined and formed some stabilized compounds or species, which were presumably survival in two states: solid particles and gaseous phases. The former ones were likely formed by the decomposition and agglomeration of CH3S*, CH3*, CH2S*, CH2*…etc., and then deposited upon the inner glass tube. After a period of time, the agglomerate was clearly observed like a distribution of yellow solid particles, which were furthermore analyzed as the combination of alkyl, C-S, a few C-O, and C-N. For the gaseous phases, low molecular-weight active species were mostly recombined into relatively thermodynamic stable species, like hydrogen sulfide (H2S), carbon disulfide (CS2), carbon monoxide (CO), and hydrogen (H2).
To improve the treatment efficiency, a double-electrode plasma system was utilized to extend the plasma reaction time. For example, with the applied power of 90 W, 400 ppm DMS in argon plasma was reduced to 150 ppm using a single-electrode plasma system, while the comparable quantity was completely degraded into H2S, CS2 and H2 using a double-electrode system. As increased the applied power of the double-electrode system to 140 W, the gaseous product H2S, owing to relatively low binding energy (92 kcal/mole), was easily decomposed and the concentration was decreased compared with 90 W, whereas the concentrations of CS2 and H2 were increased due to the decomposition of H2S.
In the case of recycling gaseous waste, NaOH solution was utilized to separate H2S from the gaseous products, while active carbon was subsequently used to form CS2 and H2. CS2 was collected by active carbon. The release of H2 was possibly used for energy regeneration. From the above measurements on the decomposition of DMS, the reaction mechanism of atmospheric micro-plasma system with respect to gaseous waste treatment was primarily established. Furthermore, a multiple-electrode system was anticipated to control the release of hazardous gaseous waste and promote a friendly and sustainable environment.
Keywords: Atmospheric, micro-plasma, dimethyl sulfide(DMS), decomposition mechanism, argon, efficiency.
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