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EMERGING TECHNOLOGY REPORT: DESTRUCTION OF ORGANIC CONTAMINANTS IN AIR USING ADVANCED ULTRAVIOLET FLASHLAMPS
Citation:
Johnson, M. D., W. Haag, AND P. G. Blystone. EMERGING TECHNOLOGY REPORT: DESTRUCTION OF ORGANIC CONTAMINANTS IN AIR USING ADVANCED ULTRAVIOLET FLASHLAMPS. U.S. Environmental Protection Agency, Washington, DC, EPA/540/R-93/516 (NTIS 93-205383), 1993.
Description:
This paper describes a new process for photo-oxidation of volatile organic compounds (VOCs) in air using an advanced ultraviolet source, a Purus xenon flashlamp. The flashlamps have greater output at 200-250 nm than medium-pressure mercury lamps at the same power and therefore cause much more rapid direct photolysis of VOCs, including methylene chloride (CH2Cl2), chloroform (CHCl3), carbon tetrachloride (CC14 ), 1,2dichloroethane (1,2-DCA), l,l,1-trichloroethane (TCA), Freon 113 and benzene. The observation of quantum yields greater than unity indicate the involvement of chain reactions for trichloroethene (TCE), perchloroethene (PCE), 1,l-dichloroethene (DCE), chloroform, and methylene chloride. TCE was examined more closely because of its widespread occurrence and very high destruction rate. Two full scale air emission control systems for TCE were constructed at Purus and tested at a Lawrence Livermore National Laboratory (LLNL) Superfund Site. The systems were operated at flash frequencies of 1 - 30 Hz, temperatures of 33 - 60°C, flows up to 300 scfm (260 ppmv TCE) and concentrations up to 10,600 ppmv (100 scfm). Residence times ranged from 5 to 75 seconds. In all cases except at the lowest flash frequency, greater than 99% removal of TCE was observed. Careful attention was paid to product formation and mass balances. The main initial photo-oxidation product of TCE was dichloroacetyl chloride (DCAC), which upon further photolysis was converted in part to dichlorocarbonyl (phosgene or DCC) and possibly formyl chloride, and ultimately to HCl and CO2. Further treatment of photooxidation products is recommended for full-scale operation.