(Reductive Thermal and Photo-Thermal Oxidation Processes
for Enhanced Conversion of Chlorocarbons)
Two innovative processes, Reductive Thermal Oxidation (RTO) and Reductive Photo-Thermal Oxidation (RPTO), are designed to safely and cost-effectively convert chlorinated hydrocarbons (ClHC) into environmentally benign and useful materials in the presence of a reducing atmosphere. Both processes have evolved from M.L. Energia, Inc.'s, Reductive Photo- Dechlorination (RPD) technology, which does not permit the presence of air (oxygen).
The RTO/RPTO processes treat air streams laden with ClHCs. RTO converts ClHCs at moderate temperatures by cleaving carbon-chlorine bonds in the absence of ultraviolet light. RPTO operates under similar conditions but in the presence of ultraviolet light. Subsequent reactions between ensuing radicals and the reducing gas results in chain-propagation reactions. The presence of air (oxygen) during the conversion process accelerates the overall reaction rate without significant oxidation. The final products are useful hydrocarbons (HC) and environmentally safe materials including hydrogen chloride, carbon dioxide, and water.
The RTO/RPTO processes are shown in the figure below. The process consists of six main units: (1) input/mixer; (2) photo-thermal chamber; (3) scrubber; (4) separator; (5) storage/sale; and (6) conventional catalytic oxidation unit. Air laden with ClHCs is mixed with reducing gas and passed into a photo- thermal chamber, which is unique to the RTO/RPTO technology. In this chamber, the mixture is heated to moderate temperatures to sustain the radical chain reactions. Depending on the physical and chemical characteristics of the particular ClHCs treated, conversion can take place in two ways: the RTO process is purely thermal, and the RPTO process is photo-thermal. After suitable residence time, HCl is removed by passing the stream through an aqueous scrubber. The stream can then be treated in an optional second storage, or separated and sent to storage.
Excess reducing gas is recycled, and residual (sub parts per million) ClHCs, HCs, and CO are treated by catalytic oxidation. Volatile hydrocarbons can also be recycled as an energy source for process heating, if partial oxidation at the photo-thermal chamber does not generate enough heat.
This technology is designed to remove volatile hydrocarbons from air streams. Field applications include direct treatment of air streams contaminated with chlorocarbons, wastes discharged from soil vapor extraction or vented from industrial hoods and stacks, and those adsorbed on granular activated carbon. M.L. ENERGIA, Inc., claims that the process can also be applicable for in situ treatment of sites containing contaminated surface waters and groundwaters. The process has not yet been tested on these sites.
This technology was accepted into the SITE Emerging Technology Program in July 1994. During the first year, laboratory-scale tests were conducted on two saturated ClHCs (dichloromethane and trichloroethane) and on two representatives of unsaturated ClHCs (1,2- dichloroethene and trichloroethene). The RTO/ RPTO processes have demonstrated 99 percent or more conversion/dechlorination with high selectivity towards saleable hydrocarbon products (methane and ethane). During the second year, a field demonstration will be conducted with a pilot-scale prototype unit, followed by performance evaluation and cost analysis.
These processes will be available for commercialization after the completion of the field demonstration.
EPA PROJECT MANAGER:
Michelle Simon
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7469
Fax: 513-569-7676
TECHNOLOGY DEVELOPER CONTACT:
Moshe Lavid
M.L. ENERGIA, Inc.
P.O. Box 470
Princeton, NJ 08542-470
609-799-7970
Fax: 609-799-0312