Volatile organic compounds (VOC) in air can be recovered by simple condensation. However, if the concentration of VOCs in the air is dilute, as is the case when VOCs are emitted from paint spray booths or during the filling of storage tanks, direct condensation would not be economical because of the large volume of air involved. Thin-film, non-porous membranes specially made of a hydrophobic resin are capable of recovering VOCs from fuel vapor for direct recycle/reuse. In the vapor permeation process, the VOCs are removed from the VOC-air mixture and condensed back to a liquid phase with very high selectivity. A vacuum is applied and the VOCs are recovered in a condenser. An inert gas sweep also can be used in place of the vacuum to achieve similar and, in some cases, superior results.
The objective of this project was to develop a cost-effective technology suitable for preventing the loss of fuel hydrocarbon components and other VOCs to the atmosphere.
Research has been performed on the recovery of VOCs, chiefly chlorofluorocarbons, from the air by the vapor permeation process. This research project extended this technology to petroleum hydrocarbons in order to control evaporative fuel and paint spray booth emissions. This applied research involved bench-scale laboratory tests to define the separation capability of selected membranes and their performance using various levels of vacuum and inert gas sweep; design and fabrication of a prototype system; field testing at an appropriate Department of Defense facility; and, finally, engineering analysis of the results including a performance analysis to determine cost and payback period.
Bench-scale evaluation of candidate resin materials in gasoline vapor streams was conducted in a membrane test cell. High removal rates for fuel components were observed. A bench-scale test also was completed for paint spray booth emission reduction. This project was completed in FY 1997 and has been transitioned to the Environmental Security Technology Certification Program.
Successful development of this technology provided a cost-effective approach for the elimination of a source of hydrocarbon emissions to the atmosphere and evaporation fuel losses during fuel handling and storage. Other benefits include the recovery of paint booth spray emissions in a liquid form and the potential cost savings over activated carbon, which was the technology of choice for VOC control for low-level sources. Implementation of this technology in the civilian sector can alleviate VOC emissions sufficiently to provide offsets to the military operations if widely adopted.