Removal of Carbonyl Sulfide Using Activated CarbonAdsorption Systems

摘要

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S),methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor controlprocesses is activated carbon adsorption; however, very few studies have been conducted onCOS adsorption. COS is not only an odor causing compound but is also listed in the Clean AirAct as a hazardous air pollutant.Objectives of this study were to determine: · the adsorption capacity of 3 different carbons for COS removal, · the impact of relative humidity on COS adsorption, · the extent of competitive adsorption of COS in the presence of hydrogen sulfide, · whether ammonia injection would increase COS adsorption capacity.BPL (peat-based), VPR (bituminous coal-based), and Centaur (physically modified to enhanceH2S adsorption) carbons were tested in 3 laboratory-scale columns, 6” in depth and 1” indiameter. COS concentrations varied from 35 to 49 ppm. Relative humidities of 17%, 30%,50%, and 90% were tested. For competitive adsorption studies, hydrogen sulfide was tested at60 ppm, with COS at 30 ppm. COS, relative humidity, H2S, and ammonia concentrations weremeasured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corporation 1000 series portable analyzer, and Drager Accuroammonia sensor, respectively.It was found that the adsorption capacity of Centaur carbon for COS was higher than the other 2carbons, regardless of relative humidity. As humidity increased, the percent decrease inadsorption capacity of Centaur carbon, however, was greater than the other 2 carbons. Thecarbon adsorption capacity for COS decreased in proportion to the percent of H2S in the gasstream, indicating that the carbon did not preferentially adsorb one compound over the other.Ammonia, which has been found to increase adsorption capacity for H2S, did not increase thecapacity for COS.