||Various air pollution problems arise with industrial development in Taiwan in the past three decades. Accompanying the problems, people in Taiwan are increasingly concerned about their own living environments. According to the annual reports issued by the Taiwan (R.O.C.) Environmental Protection Agency, the odor complaint cases increased drastically from about 20,600 in 2001 to 86,000 in 2016. Among which, 55% of the odor complaints were from industrial sources. The best solution for reducing the complaint cases is to eliminate odorous emission from their sources.|
The present study aimed at eliminating odorous compounds in gases exhausted from surface coating lines of a local plant for decorating automobile parts. The main odorous compounds of the solvents in the paints are toluene, xylenes, ethyl acetate and butyl acetate. A full-scale biotrickling filter (BTF) packed with PP balls containing PU forms therein was used to treat the gas for the purpose of oxidizing the odorous compounds. In addition, a process of scrubbing the gas with aqueous hypochlorous acid solution followed by aqueous alkaline H2O2 solution was tried to oxidize the compounds and reduce the emitted chlorine emitted from the hypochlorous acid solution, for the odor control of the test gas.
Results indicate that 81% of THC (total hydrocarbons) and 83% of NMHC (non-methane hydrocarbons) in the exhausted gas could be reduced by the BTF at an EBRT (empty bed retention time) of around 10s for the gas flowing through the packed space. The removal efficiencies of THC and NMHC were up to 75 and 60%, respectively, by the two-stage chemical scrubbing process. By the scrubbing process, odor concentrations of the gas could be reduced from 174,000 (dilutions to threshold) to values that meet the regulation one (<2,000).
Key words: biotrickling filter, chemical scrubbing, hypochlorous acid, odor control.