Fumes emitted from coffee bean roasters contain various chemicals such as aldehydes, pyridine, volatile fatty acids, and ketones. These chemicals have high odor intensities and are sensitive to human breathing organs and eyes. In Taiwan, most of these fumes are not well controlled before venting to the atmosphere.
This research attempted to eliminate these odorous and offensive chemicals by chemical scrubbing methods. Sodium hypochlorite oxidation followed by hydrogen peroxide reduction (hypochlorite-peroxide) was investigated first. After that, ozone oxidation followed by hydrogen peroxide reduction (ozone-peroxide) was also tried. In both methods, hydrogen peroxide acted as a reducing agent for the elimination of either residual chlorine or ozone emitted from the oxidation reaction.
Experimental results indicated that both methods were effective. An oxidative scrubbing liquid with an initial effective chlorine content of 200 mg/L and a pH of 12, and an reducing scrubbing liquid with an initial hydrogen peroxide concentration of 1% and a pH of 12 could remove an average of 85% of total hydrogen carbons (THC) in the fume gas from a coffee bean roaster. With a dose of 10 ppm ozone in the fume gas to the oxidative scrubbing liquid (water only) followed by an reducing scrubbing liquid with an initial hydrogen peroxide concentration of 0.3% and a pH of 12, an average removal of 80% of the THC could be removed. An odor intensity (expressed by the dilution to threshold ratio) of 9,772 in the original fume could be reduced to as low as 31 by both methods.
As indicated by the data from GC/MS (gas chromatography-mass spectrometry) analysis for the hypochlorite-peroxide method, acrolein, vinyl acetate, 2-butanone, and acetone in the roaster fume could almost completely be eliminated. Traces of chlorinated hydrocarbons as potential secondary pollutants were detected in the treated gases from the hypochlorite-peroxide scrubbing system. While by the ozone-peroxide one, satisfactory results were also obtained with no chlorinated hydrocarbons emitted. An economical analysis shows that the ozone-peroxide approach is a practical one for actual control applications.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0907110-214137 |
| Date | 07 September 2010 |
| Creators | Su, Wei-hsiang |
| Contributors | Ming-Shean Chou, Wen-Hsi Cheng, Chung-Shin Yuan |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0907110-214137 |
| Rights | not_available, Copyright information available at source archive |
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