Abstract
ABSTRACT
The commercial oxidation of hydrocarbons to produce oxygenated organics also generates byproduct water. This water ultimately appears as a waste distillation "tower bottoms" containing residual amounts of the oxygenated organics. Because such wastewater streams can be sizeable (> 8000 gal/hr) and have little mineral content, they have been considered for recycle use as cooling tower water or boiler feed water. Either use, however, would require that the dissolved organics be removed or otherwise destroyed and the pH adjusted.
This paper describes the use of technology known as advanced oxidation processes (AOP) as a means of reducing dissolved organics in such a process water stream. The raw process wastewater contained at least six identifiable organic compounds and several C5+ alcohols. The TOC level of the process water was 2500 ppm (±500 ppm) while the COD was approximately 13.500 ppm. A ninety percent reduction in the COD level was sought in order for the wastewater to be reused.
Based on the experimental results obtained from a Taguchi statistical approach for design of experiments, temperature was found to have the greatest impact on TOC reduction. Hydrogen peroxide was the most effective chemical oxidizer investigated and was more effective at elevated temperatures. Two organic acids, acetic and formic, were present in the water and could not be removed by air stripping techniques alone. They were also found to be resistant to oxidation. For this particular waste process water stream our results indicated that the desired 90% reduction in the dissolved TOC could be achieved in a period of less than thirty minutes; but only under saturated conditions of 1.0 MPa (10 atm), 180°C (350°F) and elevated peroxide concentrations. Chemical oxidation was the rate controlling mechanism in TOC reduction, while reagent oxidizer costs dominated economic considerations.
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