Gas recirculation
A vapor recovery system is a device for the reduction of volatile organic compounds ( English volatile organic compounds (VOC) ) in filling stations that during the refueling of motor vehicles with petrol is effective (in international scientific circles is called STAGE II).
In principle, there are two technical approaches: passive and active feedback systems.
- Passive return systems are based on the fact that a gas-tight connection is established between the inlet connection on the motor vehicle and the gas return line. The gases are then returned (in analogy to Stage I, the gas displacement ) through the filled fuel into the gas return line and thus ultimately into the fuel storage tanks. This system has not been pursued in Germany since about 1992, because in this case the nozzle would be very uncomfortable to handle (heavy weight, considerable effort required to press the sealing sleeve). Such systems are occasionally in operation in the USA.
- Active recirculation systems are based on the fact that when the fueling process begins, a negative pressure is generated at the gas inlet opening on the nozzle. This negative pressure is generated by a gas recirculation pump that is installed in the gas recirculation system. With German gas recirculation systems, the returned volume flow must be the same as the filling volume flow. Since the tank customer can freely choose the refueling volume flow at the nozzle, a corresponding regulation of the gas return volume flow is necessary. The 21st Federal Immission Control Ordinance ( ordinance to limit hydrocarbon emissions when refueling vehicles ) (Germany) allows a maximum deviation of ± 5% with a refueling volume flow of 38 l / min.
By means of a suction device, the part of the fuel gas-air mixture displaced during refueling - which is located in the vehicle's fuel tank above the liquid petrol - is returned to the storage tanks by means of negative pressure . This measure contributes - like the gas exchange - to a considerable extent to a reduction of the hydrocarbon emissions .
A total of three different system configurations for active gas recirculation are common in Germany:
- The gas recirculation pump runs at a constant speed . The volume flow of the fuel vapor / air mixture to be returned is regulated - by means of a proportional valve - as a function of the amount of gasoline delivered.
- The gas recirculation pump runs at a constant speed. The release of the fuel vapor / air mixture to be returned is released at each dispensing hose by an open / close valve, with the gas volume flow being regulated by a proportional valve. This system configuration is mainly represented in multi-product dispensers ( MPD ).
- The regulation of the gas volume flow is ensured by the variable speed of the gas recirculation pump. The release of the fuel vapor / air mixture to be returned is released either individually at each filling hose or at each filling pump through an open / close valve.
The legal requirements for such a gas recirculation system are in the Federal Republic of Germany in the twenty-first ordinance for the implementation of the Federal Immission Control Act ( ordinance to limit hydrocarbon emissions when refueling vehicles ) of October 7, 1992 ( Federal Law Gazette I, p. 1730 ), most recently changed on May 6, 2002 ( Federal Law Gazette I p. 1566 ).
Automatic monitoring device for gas recirculation systems
Since the last amendment to the 21st BImSchV came into force on May 18, 2002, gas recirculation systems (Stage II) have for the first time been equipped with an automatic monitoring device ('AÜE') for gas stations that were newly built after the deadline of April 1, 2003 abbreviated) mandatory. For petrol stations that were built before April 1, 2003, a certain transitional rule applies to their retrofitting. This transitional regulation is based on the quantity of petrol sold (reference year 2002) and the respective location of the petrol station.
| Amount of petrol sold in 2002 | The company is located ... | |
|---|---|---|
| ... within a study area according to § 44 BImSchG | ... not in a study area according to § 44 BImSchG | |
| > 5,000 m³ | January 1, 2005 | January 1, 2005 |
| 5,000 - 2,500 m³ | January 1, 2005 | January 1, 2006 |
| <2,500 - 1,000 m³ | January 1, 2007 | January 1, 2007 |
| <1,000 m³ | January 1, 2008 | January 1, 2008 |
