Vapor recovery

A gas recirculation system is a device for the reduction of volatile organic compounds (English VOCs volatile organic compounds ') in service stations, which is effective during the refueling of motor vehicles with petrol ( in international scientific circles this is called STAGE II).

In principle, there are two technical approaches: passive and active feedback systems.

• Passive feedback systems are based on that between the feeding connector on the motor vehicle and the gas return line a gas-tight connection is made. The gases are then returned ( in analogy to Stage I, the vapor return ) by the filled fuel in the gas return line and ultimately into the fuel storage tanks. This system will not be pursued in Germany since about 1992, as the dispensing valve to handle very uncomfortable in this case would be ( great weight, considerable effort to press the sealing collar ). In the U.S., such systems are isolated in operation.

• Active recovery systems based on the fact that at the beginning of the fueling operation, a negative pressure at the gas inlet opening in the nozzle is produced. This vacuum is generated by a gas recirculation pump that is installed in the gas recirculation system. In German gas recirculation systems, the recycled flow rate must be equal to the filling volume flow. Since the tank customer at the nozzle can choose the filling volume flow, an appropriate regulation of the gas recycle flow rate is required. The 21 Federal Emission Regulation ( 21 BlmSchV ) ( Germany ) allows a maximum deviation of ± 5 % at a refueling volume flow of 38 l / min here.

By means of a suction device by means of negative pressure of the displaced during the refueling portion of the fuel gas -air mixture - of the fuel tank of the vehicle above the liquid gasoline fuel is - returned to the storage tanks. This measure - such as the vapor return - significantly to a reduction in hydrocarbon emissions.

In Germany, a total of three different system configurations of the active gas recirculation are used:

• The gas recirculation pump runs at a constant speed. The volume flow of returnees fuel vapor / air mixture - regulated depending on the votes amount of petrol - by means of a proportional valve.

• The gas recirculation pump runs at a constant speed. The release of the returnees fuel vapor / air mixture is released at each dispensing tube by an on-off valve, the control of the gas flow rate is also realized by a proportional valve. This system configuration is mainly for multi - product columns ( engl. MPD ' multi-product dispensers ') represented.

• The regulation of the gas flow rate is ensured by the variable speed of the gas recirculation pump. The release of the returnees fuel vapor / air mixture is either individually at each dispensing hose, or released to any petrol pump by a on-off valve.

The legal requirements for such a gas recirculation system in the Federal Republic of Germany in the Twenty-First Regulation implementing the Federal Pollution Control Act ( Ordinance on the control of hydrocarbon emissions during refueling of motor vehicles - 21 BlmSchV ) of 7 October 1992 ( Federal Law Gazette I p 1730 ) set (last modified on 6 May 2002 (Federal Law Gazette I p 1566) ).

Automatic monitoring device for vapor recovery systems

Since the coming of the last change of 21 BlmSchV of 18 May 2002 in force was for gas stations that were rebuilt after the deadline of 1 April 2003 for the first time the equipment of vapor recovery systems ( Stage II) with an automatic monitoring device ( ' Aüe ' abbreviated ) for duty. For petrol stations that were built before April 1, 2003, a certain transitional arrangements shall apply in relation to their retrofitting. These transitional arrangements will depend on the amount of tax petrol (reference year 2002) and based on the location of the gas station.