Ozonation of Odorous Compounds in Gases Emitted from Rubber Processing Industries

This study aimed at the removal of odorous compounds in gases emitted from rubber processing industries. Simulated odorous gas for test was prepared by mixing fresh air and an odorous gas drawn from an oven in which a sample of rubber powder was kept either at 160°C (for a thermal plastic rubber) or 200°C (for a thermal setting rubber). The prepared odorous gas was then premixed with a definite amount of ozone-enriched air and introduced into a contact system. The contact system consists of two sieve-plate columns connected in series and each column has four 1-L chambers. Depending on with or without introducing circulating scrubbing water into the columns, the oxidation reaction could be either wet or dry one. Results indicate the wet oxidation got better performances than the dry one. The former got 97 and over 90% removal of VOCs (volatile organic compounds) and odorous intensity removal, respectively, with the operation conditions of initial ozone concentration 4.0 ppm, THC (total hydrocarbon) concentrations 6.5–10.3 ppm (methane equivalent), oxidation temperature 37.3°C, gas empty bed retention time (EBRT) 12 s, and liquid/gas rate ratio 0.01 m/m. With conditions similar to those cited above, odor concentration (dilutions to the threshold, D/T) in the test gas could be reduced from 1,738–3,090 to 31–98 with EBRTs of 11.4–14.5 s. Activated carbon is effective for both physical and chemical removals of residual VOCs, odorous compounds, and ozone in the effluent gas from the ozonation system. Economical analysis indicates that around US$ 0.16 is required for treating 1,000 m of the tested foul gas by the proposed ozonation process.