SYSTEM AND METHOD OF PETROL VAPOUR RECOVERY

The present invention relates to a system for, and method of, recovering volatile gasoline/petroleum vapours during the supply, handling and distribution of petroleum products for use in road transport and in particular, but not exclusively, when these activities are performed at a petrol filling station. The system and method are especially adapted to recover the volatile petroleum vapours from delivery tanker vehicles when the tankers discharge or deposit their loads into underground fuel storage tanks at a petrol filling station. The system is also configured so as to recover volatile vapours from individual petrol pumps when being used to dispense petrol into vehicle petrol tanks thereby mitigating damage to the environment and minimising exposure of harmful vapours to individuals dispensing petrol.

BACKGROUND

Conventionally, when a petrol delivery tanker carrying a load arrives at a delivery site, for example a commercial petrol vending site, the tanker body is connected via an outlet port and hose so that petrol is voided from the tanker into an underground fuel storage tank. Voiding can be performed under gravity or it can be pressure assisted. Petrol passes from the delivery tanker through a conduit system to an underground storage tank, from where, via a separate set of dedicated conduits customers/users can access the petrol at individual pumping stations. A moderately busy petrol filling station comprising about six petrol pumps will receive at least one delivery of petrol per day whereas a larger, for example, motorway service station, may receive as many as five fuel deliveries per day. Accordingly, delivery, voiding from the tanker and filling individual vehicles with petrol is a constant 24/7 process.

There are three stages of vapour recovery. Stage 1 A vapour recovery concerns the control and elimination of unwanted emissions of petrol vapour which occur at distribution terminals. Stage 1 B vapour recovery concerns the recovery of fumes which escape when fuel is delivered to storage tanks at retail petrol stations and Stage Il vapor recovery systems collect petroleum/gasoline vapors from vehicles' fuel tanks while customers dispense petroleum products into their vehicles at petrol/gasoline dispensing facilities. The present invention is concerned with vapour recovery at Stage 1 B and Stage II.

It is to be understood that the space above the level of petroleum in the underground storage tank contains petrol vapours, sometimes to a saturated level. Upon filling the fuel storage tank with the delivery load, these vapours are necessarily displaced by the incoming liquid and are vented to the atmosphere via extended pipes in a so called vent stack arrangement. The discharge of such vapours to the atmosphere is not only wasteful but is damaging to the environment and can create a risk of explosion, in addition, inhalation or other contact with petrol vapours can present a serious health hazard. In order to mitigate this vapour release or what is termed in the art as "Stage ^" I B" vapour recovery (vapour balancing) it is known to modify the petrol storage vent system so that the vapours displaced during unloading are returned to the delivery tanker. In petrol stations having Stage 1 B vapour recovery in place a hose is connected from a receptacle on the vent system of the filling station to a fitting on the tanker which is in turn connected to the ullage of the tanker. In theory, as the liquid is transferred to the underground tank, vapours are drawn into the ullage or empty space of the tanker. The tanker then returns to its terminal with, theoretically a consignment of petroleum vapour. Once back at the terminal these vapours are expelled as the tanker is refilled and the vapours are passed through the terminal's own vapour recovery system. In practice this system is not very efficient. Reports suggest that in the event of any petrol being recovered it is seldom more than 1 -2 litres per tanker, this is in comparison to the 35,000 litres of a normal delivery load. The terminal vapour recovery units have massive power consumption so that the carbon footprint for this operation is substantially negative. A further disadvantage of the prior art vapour recovery Stage 1 B is that the tanker theoretically returns to the terminal with an unacceptable cargo of highly explosive vapours. In practice it is likely that a substantial amount of the vapours are dispersed from the tanker during the course of its return journey to the terminal through vents in the tanker body and thus contributes further to environmental pollution. It is also possible that due to the high vapour pressure of the petrol as it is transferred to the underground storage tank much of it will be discharged to atmosphere via a pressure and volume valve that is built into the conduit system.

There have been a number of incidents, during and after road tanker deliveries, at petrol filling stations provided with Stage 1 B vapour recovery where:-

• Large quantities of petrol have flowed out from the fill pipes of storage tanks.

• Fill pipes have become pressurised resulting in vapour and/or petrol being released to atmosphere when the cap is removed. Such situations are potentially dangerous, as the person removing the cap is at risk of being engulfed in vapour

or wetted with petrol. In addition, there is the risk of serious physical injury being sustained where quick-release caps are in use, as these devices can be displaced with considerable force when the release mechanism is actuated.

It will be understood that current practices of Stage 1 B are not completely satisfactory as vapour escape still occurs and it is especially unsatisfactory to the petrol filing station owner since the vapours recovered in liquid form are not returned to the purchaser but rather kept by the individuals involved in tanker distribution or the tanker owners at the terminal depots. Since there is are very meager profit margins to be had at filling stations associated especially with large supermarket chains, any petrol that could be recovered by the filling stations themselves on site would offer an immediate advantage over the prior art.

It will be appreciated that there are two other situations where vapour release occurs at the petrol vending stations. Firstly, vapour release occurs due to evaporation when petroleum is stored in the underground storage tank. During this passive or stand-by mode vapours in the storage tank are displaced to atmosphere by a build up of pressure in the underground storage tank (vapour pressure). Where a pressure and vacuum (P&V) valve is fitted to a venting system vapours will still be discharged to atmosphere whenever the vapour pressure exceeds the release setting of the pressure and suction valve. To eliminate the possibility of underground storage tank overpressure the P&V valve is normally set to around 30mb. The vapour pressure of petrol under normal storage conditions is well in excess of this so there is a constant release to atmosphere of vapours.

In addition to Stage 1 B vapour recovery and the constant evaporation from the storage tank, there is a small amount of vapour loss each time a customer or user dispenses petrol from individual dispensers or pumps into their vehicle. This represents a yet further scenario of vapour loss, i.e. when a car is refuelled at the pump then once again vapours are expelled. The volume of vapour dispelled is estimated to be equal to or more than the volume of liquid fuel transferred. At this time these vapours are discharged to atmosphere creating all of the issues described in the introduction above. This is referred to as "Stage M" vapour loss and Stage Il legislation (to be in force by 2010 for petrol stations selling more than x10 ⁶ I/year) will require that these vapours must be recovered and release of noxious vapour to the environment prevented. Prior art Stage Il systems typically consist of special nozzles and coaxial hoses at each

petrol/gasoline pump that captures vapors from the vehicle's fuel tank and routes them to the station's underground or aboveground storage tank(s) during the refueling process. However, there is still substantial vapour loss to atmosphere and inadequate vapour recovery with such sytems

There is therefore a need to provide an improved system and method of efficiently recovering petrol vapours and preventing their escape to atmosphere from a variety of sources especially at petrol filling stations. The present invention provides an improvement to both Stage 1 B and Stage Il vapour recovery in addition to vapour recovery from underground storage tanks in a passive 'stand-by' mode and will offer immediate benefit to the environment, the filling station proprietors and consumer alike.

There is also a need for a simplified system that can easily be fitted to existing gasoline/petroleum dispensing outlets.

BRIEF SUMMARY OF THE DISCLOSURE

According to a first aspect of the invention there is provided a system for recovering volatile petroleum vapours from a petrol filling station site during dispensing of liquid petroleum from a first unit to a second storage unit, the system comprising a delivery pipe for directing liquid petroleum from the first unit to the second storage unit, a vapour recovery unit in fluid connection with the storage unit by means of a connecting pipe one end of which protrudes into an upper portion of the storage unit above its fluid level, the vapour recovery unit comprises a heat exchanger unit having at least one expansion valve to control flow of a liquid refrigerant therethrough, a compressor unit for compressing gaseous refrigerant back into its liquid form, an inlet port and inlet pipe for receiving petroleum vapours from the storage unit via the connecting pipe and an outlet port and outlet pipe for collecting condensed petrol from the vapour recovery unit, the vapour recovery unit further comprises a connection to a vent stack for eliminating vapour free gases to atmosphere.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Reference herein to a "petrol filling station" is intended to include a garage or petrol station, commercial or otherwise where a road vehicle or the like can receive petrol or fuel from a storage unit.

Reference herein to a "heat exchanger" is intended to include any device which is capable of transferring heat through a conducting wall from one fluid to another.

Preferably, the first unit is a petrol delivery tanker.

Preferably, the second storage unit is a petrol storage tank and more preferably it is an underground storage tank. Underground petrol storage tanks are typically cylindrical in shape and are positioned underground to lie in a horizontal direction.

Preferably, the inlet pipe is provided with an expansion flow valve to regulate vapour ingress to the vapour recovery unit (VRU).

Preferably, the heat exchanger is of sufficient efficiency to permit a muti-pass system for greater dwell time.

For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger. The exchanger's performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence. Figure 1 shows a suitable arrangement for use with the present invention.

Preferably, the VRU is fitted in Zone-O. The area known as the "Zone-O" on a petrol station forecourt is the area where individuals dispense petrol into vehicles and where a delivery tanker may make its delivery.

Preferably, the VRU has no mains voltage electrics. Preferably, the VRU comprises a power and control unit that is installed remotely from where the VRU is positioned. It is desired that the power and control unit is not situated in this Zone-O area for safety reasons.

Preferably, the power and control unit is configured to require a single phase mains electrical supply, preferably it is modified so that it is capable of operating using a low voltage AC or DC supply. In this way the potential hazard of electrical components in the Zone-O area is avoided.

In one embodiment of the invention, the power source comprises two compressors, preferably at least one compressor is a large compressor to handle the load when a tanker makes a delivery and an additional small compressor to handle stage Il recovery loads together with natural evaporation loss. Alternatively a variable speed motor can be fitted to allow a duty range from 0-maximum in infinitely variable stages.

In another embodiment of the invention, the compressor is a swash plate compressor which provides variable piston stroke and can be used either in conjunction with a conventional electric motor or a switched reluctance drive motor. Preferably, the circulating liquid refrigerant in the heat exchange unit is a zero ozone depletion blend of HFC refrigerants, the refrigerant is prefereably for example Forane™ 404A or R404A which is a blend of R-125, R-143a, and R-134a.. The refrigerant is selected not only for its cooling properties but also that when in gaseous form it is substantially non-toxic or hazardous.

Preferably the flow of liquid refrigerant is controlled by an expansion flow valve.

Preferably, the system includes a non-resettable intrinsic safe volume meter to provide an accurate real time indication of liquid recovered.

It is desirable that the actual volume of vapour recovered to liquid form be visible and measured as an indication of the system's efficiency,

It will be appreciated that the system of the present invention thus provides a means for vapour recovery during petrol delivery and also in a passive mode when the storage tank is also releasing vapours but to a much lesser extent than during a delivery. The volatility of petrol is an established fact and the rate of evaporation and vapours volume will be at a maximum on delivery due to churning of the liquid petrol and also vapour displacement from the storage tank but vapour release will also occur during periods of storage. The present system allows for recovery in each situation. The first unit or delivery tanker is releasably in connection with the delivery pipe so that petrol is delivered to the storage tanker, the VRU is permanently in connection with the upper part of the storage tank so that vapours may be collected both during delivery of petrol and when petrol is merely being stored.

The present invention therefore provides a system which is installed close to the offset fill system and connects into the existing vent stack. The vapour recovery section uses a refrigerant to cool the petrol vapour in order to condense out the liquid petroleum. An expansion valve is fitted which controls the flow of the liquid refrigerant based on the temperature of the heat exchanger. This will change the flow of refrigerant to suit the amount of petrol vapour to be condensed and works in conjunction with an inverter control on the compressor section of the apparatus. The heat exchanger uses the latent heat of evaporation of the refrigerant to provide the cooling of the vapours. The refrigerant passes from the heat exchanger in gaseous form to the compressor section by means of for example a copper pipe system. At the compressor section the gaseous refrigerant is compressed back into a liquid giving up its latent heat of condensation to the surroundings. A liquid refrigerant line transports the refrigerant back to the expansion valve where the process is repeated.

Preferably, in an alternative embodiment of the invention, the system further comprises a first connecting conduit in fluid connection with the inlet port of the VRU and an underground vapour return pipe association with an individual petrol pump, the first connecting conduit being positioned so as to allow passage of volatile petrol from individual petrol pumps to the VRU.

Vapours from individual petrol pumps may be, in one embodiment of the invention, returned to the ullage of the underground storage tank from where they may be directed to the VRU for vapour recovery. In an alternative embodiment of the invention and in a more direct recovery process, the vapours released when dispensing at an individual pump are returned by a suction line to a pump line manifold and thereon in to the VRU inlet port via the inlet pipe.

In this latter embodiment preferably a petrol resistant line, ideally flexible and ideally in the form of a plastics or the like pipe, is moused or fed along a suction line which feeds the dispensed petrol line from the storage tank to the individual pump.

Preferably, the VRU includes a further second connecting conduit for releasably connecting directly to a pipe associated with the first unit or petrol delivery tanker. In this further embodiment of the invention, the delivery tanker may be directly connected to the VRU so that vapours released during dispensing of the petrol load into the storage unit from the tanker itself are directed to the VRU. In this embodiment of the invention, vapours formed in the ullage of the delivery tanker are passed, preferably under suction to the VRU from whence liquid petrol may be recovered. It will be appreciated that this embodiment allows for vapour recovery from the delivery tanker at the site of delivery and prevents the potential risk of tanker return to terminal with a load of volatile potentially hazardous petrol vapours.

Preferably, the system includes one or more compressor inverter units associated with any one of the conduit systems to speed up or slow down vapour recovery so as to match the flow and/or generation of vapours within the system.

Preferably, the system includes one or more gate-valve arrangements strategically positioned so as to allow isolation of a part of the conduit system for maintenance purposes.

A particular advantage of the system of the present invention resides in the simultaneous potentially three-fold vapour recovery at a vending/dispensing station in the scenarios from (i) tanker delivery, (ii) passive stand-by vapour release when petrol is in a storage unit and (iii) when individual petrol pump dispensing activities occur.

A yet further advantage of the system of the present invention resides in the simplicity of a retro-fit to existing petrol stations. The system of the present invention can be readily, easily and cheaply installed in existing petrol dispensing facilities. The system of the present invention can be connected to an existing vent stack system at a petrol station and provides a safe stand alone unit with the added safety feature of entirely mechanical parts within a Zone-0 area.

The Vapour Recovery System of the present invention has been specifically designed to be very simple and advantageously be simply retro-fitted and yet able to prevent the release of vapours to atmosphere during all aspects of a filling station operation. Whilst there are prior art systems which individually address Stage 1 B and Stage Il recovery the present system combines Stage 1 B with recovery of pre-collected stage Il vapours as part of an overall vapour recovery package in addition and uniquely to recovery of vapours from evaporation loss in passive or stand-by recovery mode.

The system of the present invention recovers vapours when replenishment of underground tanks by road tankers occurs. It also can simultaneously collect vapours from stage Il systems where vapours are collected from the fill nozzle during dispensing of petrol and condensing and recovery of vapours which would otherwise be released to atmosphere during normal operation of the filling station either open for business or closed due to vapours in the underground storage tank ullage being at a higher pressure than the venting system will permit. By explanation the vapour pressure of petrol falls in the range 500-60OmB whereas the pressure and suction valve (if fitted) often installed as part of a stage 1 B recovery system is set to a maximum positive pressure of around 35mB. On this basis vapours are likely to be released to atmosphere even when there is no activity at the filling station. The system of the present invention prevents this from release by condensing the vapours and returning the liquid petrol to the underground storage tank.

According to a further aspect of the invention, there is provided a method of recovering volatile petroleum vapours from a storage unit at a petrol filling station both during delivery of liquid petroleum from a delivery tanker to said storage unit and also during periods of passive evaporation from said storage unit, the method comprising directing volatile petroleum vapours through a closed conduit system to a vapour recovery unit comprising a heat exchanger and compressor arrangement, the conduit system being

permanently in connection an upper region of the storage unit and the storage unit being releasably and sealably in fluid connection with the delivery tanker.

It will be appreciated that, in practice that a delivery tanker connection is for the duration of delivery of the petrol cargo and as such during delivery is connected into the closed system but upon completion of delivery the tanker connection is released and sealed so as to maintain a closed system of interconnecting pipes/conduits and thus vapour flow to the VRU.

Preferably, the method also includes the step of collecting vapours from the delivery tanker itself by means of a direct connection from the ullage of the delivery tanker to the VRU.

Preferably, the method further includes vapour recovery from individual pumps when being used to dispense petrol to individual vehicles.

Preferably, the methods of the present invention further include any one or more of the features associated with the first aspect of the invention.

It will be appreciated that the method of the present invention, when in use and during delivery of petrol to a filling station is capable of recovering approximately 0.1 to 1 .0% of a delivery load in addition to recovering vapours released by evaporation from the standby or passive mode of evaporation during storage.

It is believed that the method of the present invention is unique in being capable of collecting vapours round-the-clock from at least three different sources (tanker delivery, passive evaporation during storage and individual pump dispensing) in addition to the optional collection of vapours and subsequent recovery from the petrol delivery tank itself, all whilst at the petrol station premises. A further advantage of the system and method of the present invention, especially when collecting vapours form the individual pumps and when dispensing petrol to vehicles is that noxious volatile vapours such as benzene (a known human carcinogen) may also be collected and thus reduces hazardous health risks.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a through section of a vapour recovery unit heat exchanger.

Figure 2 shows one embodiment of the system of the present invention for recovering volatile petrol vapours during a tanker delivery and from underground fuel storage tanks.

Figure 3 shows an alternative embodiment of the system of the present invention for recovering both volatile petrol vapours during a tanker delivery and from dispensing petrol from petrol pump units.

Figure 4 shows the embodiment of Figure 3 when in use dispensing petrol into a vehicle tank.

Figure 5 shows the connecting pipe configuration of the vapour recovery unit, vent stack and petrol pump manifold unit.

DETAILED DESCRIPTION

The system of the present invention may be installed at a petrol filling station and comprises two main components, a Vapour Recovery Unit (VRU) and a power control unit. The VRU is typically installed adjacent to the remote fill point where the tanker would park to make a delivery. The VRU advantageously has no mains voltage electrics. The power and control unit operating the VRU is installed away from the "Zone 0" area in a suitable location and requires as little as a single phase mains electrical supply, with modification it is capable of operating using a low voltage AC or DC supply. The two units are interconnected by a two pipe system. A low voltage control cable may be added to provide additional facilities.

The system and method of the present invents have been designed to recover petrol vapours under the following circumstances:-

• Tanker Delivery

The VRU is connected to the (Stage 1 B existing) vapour recovery fitting on the petrol station venting system. The displaced vapours pass directly through the VRU section

and the vapours are condensed into liquid petrol. It is possible to recover between 35 - 50 litres of reusable petrol from a delivery of 35,000 litres. The pressure drop (frictional loss) through the VRU is less than the overpressure setting of the P&V valve so all vapours will be recovered and the P&V valve will remain shut. The tanker recovery hose may still be connected as required. The suction provided by this connection may aid the flow of petrol and vapours through the system. Figures 2-4 shows the connections to the VRU and the direction of flow of both petrol and vapours.

• Individual Pump (Stage 2)

The system of the present invention has been designed to recover these vapours when used in conjunction with a suitable stage 2 nozzle system. If the collected vapour is returned to the ullage of the underground storage tank then they may be recovered in conjunction with the "evaporation loss" vapours as described in a "passive" situation hereinafter. Where the vapours are not returned to the ullage and a more direct recovery is required then the vapours can be passed through the VRU by means of suitable plumbing where a direct conversion from vapour to liquid can take place. The invention allows for a small petrol resistant line to be "moused" along the suction line which feeds the dispensed petrol from the underground tank to the pump. This vapour line is extracted from the suction line at a convenient T' under for example, the manhole cover, and then transferred to the vent pipe.

The VRU system can operate efficiently through a wide range of duties automatically. From the vapours produced by one car being refuelled to a full tanker delivery of 35,000 litres in 20 minutes.

• Evaporation Loss (Passive or Stand-By Recovery)

Petrol is a volatile liquid and will evaporate whilst in the underground storage tank. The rate of evaporation is dependent on temperature and other factors. In a sealed tank petrol will evaporate until vapour pressure is reached at which point the vapours will be saturated. In the present system, since a P&V valve is fitted this will release long before vapour pressure is achieved. Unless large volumes of liquid petrol are being drawn off at the pumps it is most likely that vapours will be escaping to atmosphere via the P&V valve.

With the system of the present invention this can be avoided and even more vapour recovered which would otherwise be lost to atmosphere.

A sensor in the venting system is able to energise the VRU when pressure is increased but before the P&V set point. This way the vapours which would have been discharged pass through the VRU and return to the tank as liquid. As soon as the tank pressure has returned to atmospheric the control system turns off the VRU. These actions are fully automated in practice.

With reference to Figure 1 , there is shown a vapour recovery unit in through cross- section. The VRU comprises a heat exchanger unit (A) with a concertina arrangement (1 ) through which liquid refrigerant flows. The liquid refrigerant is supplied by a pipe (2) from a store and is under the control of a mechanical expansion flow valve (7). The refrigerant exits the unit (A) via outlet port and pipe (3). On exit the refrigerant will have given up its latent heat of evaporation and will be in gaseous the gaseous refrigerant is passed to a compressor unit and converted back into liquid form so that it can be re- circulated in the heat exchanger. Volatile vapours from the variety of sources as hereinbefore described enter the VRU via inlet port and pipe (4) and pass over the convoluted refrigerant containing pipe-work system (1 ) of the heat-exchanger whereby the vapours are cooled and give up their latent heat of evaporation energy thereby becoming liquid petrol. Recovered liquid petrol is collected via outlet (5) and vapour free air can then be passed to atmosphere at vent (6). It is desired that vapours enter the VRU at an upper region so that liquid can be recovered and drained at a lower region assisted by gravity.

Turning to Figure 2, there is shown one embodiment of the invention for recovering volatile petrol vapours during a tanker delivery and for vapour recovery from a storage unit during passive or stand-by mode. It is to be understood that vapour release will be at a maximum when a delivery occurs due to the agitation or churning of liquid petroleum on delivery and on entering the storage unit (8) positioned below ground level (9). Petrol is delivered from a delivery tanker which is connected at point (B) to a fill pipe (10). Typically the delivery or fill pipe (10) is 4 inches in diameter and passes into the underground storage unit (8) through a lid (1 1 ) and down to a lower region of the storage unit (8). As will be apparent liquid fuel resides in area (12) and displaces or pushes up any vapour from area (13), especially during delivery of liquid fuel.

Fuel vapour in area (13) then passes via pipe or vent line (14) through lid (11 ). Pipe (14) is typically a 2 inch vent line and is connected to VRU (A) from where liquid vapours can be recovered. Connection (18) to the VRU can be via an existing recovery branch (17) connected to vent stack (15).

In this embodiment of the invention the system is designed to recover vapours during delivery and storage and as will be apparent from the Figure it is also adapted to optionally recover vapours from the tanker itself at connection (C) via a connection system into VRU (A). The connection ideally creates suction which aids flow of delivery of fuel into storage unit (8). The system is also connected to a vent stack (15) and is provided with gate safety valves (16). As hereinbefore described the VRU and tanker delivery is situated in Zone-0 and as such the power and control unit (not shown) is situated remotely so that all actions in Zone-0 are purely mechanical thereby avoiding electrical means in the hazardous/sensitive Zone-0 area. It will also be appreciated from connection (18) to VRU that the system can be easily fitted to existing petrol stations without major reconstruction changes to existing pipe networks.

In the embodiment depicted in Figure 3, there is shown a further embodiment of the system in which petrol vapours may also be recovered from an individual petrol pump (18). In a typical petrol garage arrangement several petrol pumps (18) draw petrol from reservoir (12) by means of a suction lines (24). Petrol is then drawn up a suction line (20) in a flow line direction from storage unit (8) to pump (18). The pumps are all fed in this way and commonly vented by a manifold (23) to a stack vent pipe (15). However, in the present invention a further connection is provided between a vapour return pipe (19) connected to a Stage-2 recovery system positioned in the petrol pump (18). The vapour return pipe (19) is positioned within the suction line (20) and receives vapours from a moused line (25). In use, when petrol is being dispensed from pump (18) vapours are returned via the flexible mouse line (25) which is petrol resistant and flexible, ideally a plastics tube and returned via vapour return pipe (19). This vapour return pipe (19) is connected via a connecting pipe (21 ) and connection (22) so that vapours pass into vent line (14) and onto VRU (A). Since petrol pumps are typically inter-connected in existing facilities by manifold (23) and vent stack (15), the modifications hereinbefore described may be easily made to connect all pumps with the Stage-2 vapour collecting assembly (25, 19, 21 , 22, 14, 23, A).

Figure 4 shows the system of Figure 3 when car (27) is being filled via nozzle (26) with petrol from storage unit (8) at a pump (18). Vapours released during dispensing of petrol at pumps are moused by a line (25) within pump (18) so as to return via vapour return pipe (19) and connection pipe (21 ) to vapour recovery unit (A).

With reference to Figure 5, there is shown in greater detail the connecting pipe configuration of VRU (A) and vent stack (15). Manifold (23) receives vapours from individual pumps and storage unit via vent pipes (14, 28, 29, 30), these then combine into pipe (38) which is closed off from vent stack (15) by gate valve (16), vapour pass into VRU (A) and vapour free air is released by pipe (31 ) back into the vent stack (15) and then to atmosphere (37). As will be apparent from the Figure, vapours are essentially redirected from direct release to atmosphere by a system of pipes directing them to VRU (A). The VRU also has a connection (C) to recover vapours from the delivery tanker itself when dispensing/delivering its petrol load and for recovering vapours from the underground storage unit on delivery and in passive stand-by mode (B, 10, 14, 23, 38, 18). The system is also provided with a number of mechanical flow volume control valves (33, 34, 32, 35, 36) operated remotely by a power control unit outside Zone-O.

The system of the present invention is believed to be capable of recovering up to 0.5% or more of a delivery load lost in evaporation of petrol and also of recovering vapours released in passive storage in addition to recovering Stage-2 vapour loss during dispensing petrol at pumps. The system of the present invention can be easily and economically fitted to existing petrol stations and also can be economically operated 24 hours per day all year round. It is estimated that for 4 kW of cooling power only 2.5 kW of electricity is required, this relates to approximately 3.5kwhrs of energy to condense 50 litres of vapours at a current commercial rate of 28p per tanker load which makes the system of the present invention advantageously both economical and environmentally friendly.