Treatment of VOCs emitted from surface-coating operations by a biotrickling filter packed with wood chips

• Main Authors: Hung-yu Wu, 吳宏佑
• Other Authors: Ming-Shean Chou
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/16804311811781750332

碩士 === 國立中山大學 === 環境工程研究所 === 101 === Surface coating of metal surfaces provides decoration and corrosive prevention for the surfaces. Normal coating processes include paint coating (dipping, spraying, or rolling), drying, baking, and cooling. In the processes, volatile organic compounds (VOCs) in paints emit to vented gases and the VOC-laden gases should be treated before venting into the atmosphere depending on the emitted VOC concentration, emission rate, and regulations. In the past decades, low-VOC paints have been developed for the purposes of cost reduction and environmental protection. Concentrations of VOCs in the vented gases are decreasing as compared with those in the past, and accordingly, technologies for further reduction of VOCs in the gases should be developed. Biological degradation of low concentrations in waste gases has merits of simple equipments, simple operations, and low costs. This study used a pilot-scale trickling-bed biofilter to test its feasibility for removing VOCs in a gas stream containing VOCs vented from several brands of paints for steel coating. The biofilter (BF) was made of transparent acrylic resin for observation of the media during the test. The BF was packed with 4 liters (10 cm sq.×40 cmH) of wood chips for pulp manufacturing with average sizes 2.03cm×2.25cm, wet packing density 470 kg/m3, void fraction 0.57, and specific surface area 300 m2/m3. Evaporated VOCs from test paints with air were introduced into the BF for performance tests on the effects of gas EBRT (empty bed retention time) through the packed section on the VOC removal efficiency. Results indicate that with an EBRT of 12 s and circulation liquid pH 7.0-8.0, 90% VOCs of 10-180 mg/m3 (expressed as methane equivalent) in the influent gas could be removed. An additional test was performed for the elimination of styrene in an effluent gas from a resin plate manufacturing plant by a BF packed with 60 L fern chips with wet packing density 200 kg/m3, void fraction 0.80, and specific surface area 790 m2/m3. Results indicate that with an EBRT of 10 s and circulation liquid pH 7.0-8.0, 80% styrene of 20-60 mg/m3 (expressed as methane equivalent) in the influent gas could be removed.