| Summary: | 博士 === 國立中山大學 === 環境工程研究所 === 107 === This study compares the performances of fern and plastic chips as packing media for the biofiltration of a styrene-laden waste gas stream emitted in a plant for the manufacture of plastic door plates. Fern chips (with a specific surface area of 1,090 m2/m3) and plastic chips (with a specific surface area of 610 m2/ m3) were packed into a pilot-scale with a total media volume of 50 L for the performance test. Field waste gas with styrene concentrations in the range of 161-2,390 mg/Am3 (@28-30oC) was introduced to the bed and a fixed EBRT (empty bed retention time) of 21s, a volumetric gas flow rate of 8.57 m3/hr, and superficial gas velocity of 53.6 m/hr was maintained throughout the experimental period. Nutrients containing metal salts, nitrogen, phosphorus, and milk were supplemented to the filters for maintaining the microbial activities. Results reveal that the biotrickling filter developed in this study had the highest styrene elimination capacities (170 g/m3hr for fern-chip packing and 300 g/m3hr for plastic-chip packing) among those cited in the literature. The plastic medium is a favorable substitute for endangered fern chips. The thermal-setting nature of plastic chips limits their recycle and reuse as raw materials and the study provides an opportunity for the utilization of the materials.
In addition, the study used a bench-scale biotrickling filter packed with mixed plastic chips with specific surface area of 61050 m2/m3 to test its performance for the removal of volatile organic compounds (VOCs) vented from paint-spraying operations. A paint containing ethyl acetate, butyl acetate, toluene, and xylenes as main solvents was used. The influent THC (total hydrocarbon) concentrations were in the range of 27-234 ppm (expressed as methane equivalent) and EBRT (empty bed retention time) for the gas flowing through the empty bed space were 4.8-11.4s in the experimental period of 125 days. Results show that a maximum THC(total hydrocarbon) removal capacity K of 86 g as methane/m3h with EBRT of 4.8-8.2s being obtained and the value implies that it is possible to effectively eliminate the volatile organic compounds (VOCs) with the short EBRT(empty bed retention time) as compared with other related studies. Ethyl acetate and butyl acetate were more easily absorbed and removed by the microbial films than toluene and xylenes because of the much lower volatility and higher water affinity of the former two compounds.
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