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Gasoline Vapor Recovery |
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Problem
The California Air Resources Board (CARB) has adopted regulations requiring that all retail gasoline stations utilize Enhanced Vapor Recovery systems to reduce the emissions of gasoline vapors during gasoline dispensing. The purpose for these regulations is to combat the formation of ground-level ozone due to hydrocarbon emissions. In addition to reducing air pollution, fuel savings will be realized since the recovered vapors are returned to the underground storage tanks. Solutions Two classes of solutions are available for gasoline vapor recovery at stations utilizing dispensing pumps with balance vapor collection. These are: carbon adsorption and membrane gas separation. Carbon adsorption is simple and works well when the majority of vehicles being filled are equipped with on-board vapor recovey (ORVR). In locations where most vehicles do not have on board vapor recovery, carbon adsorption cannot be used. In contrast to carbon adsorption, membrane gas separation systems can be used regardless of whether the majority of vehicles are ORVR equipped or not. Membrane gas separators can also be used at stations utilizing dispensing pumps with vacuum assisted vapor collection. Membrane Gas Separators Two kinds of membranes are available for recovery of gasoline vapor, silicone rubber and CMS fluoropolymer. Competitive silicone membrane based vapor processors pass the hydrocarbon portion of the vapor, and the retained gas (largely air) is vented. Should the system fail, safeguards must be built into the vapor processors to prevent uncontrolled release of gasoline vapors into the atmosphere. Such systems generally require a complex mechanical system to operate properly, including a fan, pump, condenser, valving, and the membrane cartridge. CMS fluoropolymer membranes operate by permeating and venting relatively clean air to the atmosphere, while retaining and recycling gasoline vapors to the tank. Essentially no emissions would then occur should there be power or system failures. No condenser is required for CMS membrane systems, resulting in less complex, more reliable mechanical systems. Performance CMS membrane cartridges for controlling gasoline vapor emissions from underground storage tanks are designed to operate in vapor processors. Vapor processors using CMS membrane cartridges have been certified by CARB to comply with the CARB Phase II Enhanced Vapor Recovery regulations. System performance measurements showed total fugitive gasoline vapor emissions to be 27 % of the maximum allowable emissions of 0.38 pounds of gasoline vapor per 1000 gallons of liquid gasoline dispensed. The vapor processor typically reduces gasoline vapor in the air vented from the underground storage tank to less than 2%. Related Publications
Koch, W. H., ‘Developing Technology for Enhanced Vapor Recovery: Part 1 – Vent Processors’, Petroleum Equipment & Technology, Feb/Mar 2001, pp. 16-22.
http://www.t-r-i.com/gifs/xPET2-01.pdf
Contact us
If you have a process where you wish to control and recycle hydrocarbons, solvents or other organic vapors, contact
CMS today for an evaluation of CMS gas separation membranes in your specific application. |
Typical Site 
Performance 99% Efficiency |
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