Assessment of the strategies for reducing volatile organic compound emissions in the automotive industry in Taiwan

Automotive coating processes must adhere to consumer preferences, such as anti-rust, weatherproof and overall appearance of coatings. Some solvents are added as thinners and additives to avoid excessive viscosity of the coating materials and to increase facility in painting. In addition, solvents use in the automotive industry in Taiwan is estimated at 7200 ton/year in major coating processes, including electrodeposition coating, primer coating, top coating, and bar coating. Volatile organic compounds (VOCs) are not easily controlled. It is important to know the VOC-pollution sources and emission characteristics before treating the VOCs in automobile industry. In this study, 80 stacks in five factories were tested to evaluate emission characteristics in each VOC-source, After examining the flue gases, the amount of solvents used for washing spray gun and base coating are estimated at 3350 ton/year, and about 1700 ton/year for primer coat and clear coat. The organic solvents include toluene, xylene, ethyl acetate, n-butyl acetate, and ketone. VOC emission factors from each plant ranges between 500 and 650 g-VOC/1 coating. To reduce the amount of coating and waste liquor, recommended methods include increasing gun spray efficiency, lengthening the same color-painting period, reducing the solvent content in painting and adding treatment equipment. The high-solid content painting, waterborne coat. and powder coat should be used for traditional painting. Moreover, carbon adsorption bed and zeolite rotator recovery system can replace scrubbers, since they can be used as solvent recovery equipment. (C) 2002 Elsevier Science B.V. All rights reserved.