Vapour recovery method and apparatus

Technical Field.

The invention relates to a method for collecting residual gases in fuel filling plants and in fuel tanks, and an apparatus therefor. The term tank is intended to cover both mobile and fixed tanks: for this reason, the ^p resent invention relates both to filling operations for vehicles and other thermal engines, and tc tanks usec for containing fuel in refineries and storage ^p lants, including vehicle fuel earners and the like.

Background Art.

During filling operations of liquid fuel such as for example petrol, diesel and the l ke, a part of the fuel passes from a liquid to a gassy state.

Inhalation of these gases is known to be damaging bot ^h to humans and the environment.

For these reasons such gases should advantageously be eliminated or at least limited aε much as ^p ossible.

Legislative steps have been taken which recognise the danger caused by such fumes with regard to operators working in the vicinity thereof, as well as for users and the environment. Indeed, there are already norms in force both in Italy and abroad which attempt to limit or eliminate the above-mentioned emissions in fuel refilling plants.

With reference to the specific case cf fuel distribution plants, an attempt at a solution to the problems outlined provides fuel distributors wherein the dis ^p ensing ^p istol is provided with a sorx of sucker terminal which achieves

a seal between the pistol and the mouth of the filling conduit on the vehicle. The fuel dispensing pipe is coupled coaxially to a second pipe connected to a suction pump, which latter aspirates the gas and discharges same into a conduit leading to the underground fuel tank. This type of process contains at least two drawbacks. A first of these relates to environmental safeguarding and is connected to the fact that the use of the fuel storage tank for the collection of the gases means that those very gases are released into the environment on each refilling operation of said tank. So the gases reach the environment eventually anyway.

A second drawback relates to the expense of the work needed to adapt existing fuel filling plants to this method. For each distributor a gas aspiration pump must be connected up to one of the filling station underground tanks, and these are often situated at a considerable distance from the distributor, leading to extensive excavation, refilling and recovering work. The problem of gaseous residues is of considerable importance in relation to the transport of fuels and refilling of the tankers in refineries. Indeed, after having emptied their load into fuel station tanks, the tankers are full of residual gases This in effect means that the same tankers, once empty, represent a real danger of explosion.

From the environmental point of view, a further negative characteristic of the present method of utilisation of vehicle fuel tankers is connected with the exchange of fuel between said tanker trucks and the fixed tanks found in refineries (or intermediate fuel storage plants) In this case the gaseous residues are collected in storage tanks and burned off. The resulting candle-like flame is a familiar sight in refineries, but burning off also contributes to envi romental pollution.

Disclosure of the Invention.

The aim of the present invention is to eliminate the above-mentioned drawbacks using a method which causes gaseous residues to condense and enable the resulting liquid to be reused or in any case collected without any escape thereof into the environment.

The liquid obtained from the condensation can be collected in a special container tank or, in the specific case of filling stations, can be reintroduced into the dispensing pistol supply circuit, for example at the fuel supply pump.

Rei ntroductl on of the liquid into the pistol supply circuit advantageously enables any need for supplementary tanks and connection conduits to be eliminated. In the case of tanker trucks, the liquid obtained from condensation can preferably be collected in collection tanks, situated at the fuel filling stations or

The condensation can be effected in vaπous ways: one preferable way is to cool the gassy residues down to a temperature which liquifies them. Other methods might employ pressurisation or chemical processes which lead to

A cooling method, as mentioned above, can be constituted by a refrigeration unit associated to an aspiration pump for the gas residues, in the case of fuel filling stations said unit being connected to the fuel supply pump. In this way, the gassy residues aspirated by the pump are condensed by the refrigeration unit and the liquid thus obtained is reintroduced into the fuel filling circuit through the supply pump, for example through the conduit leading to the air separator chamber of the pump. The technical characteristics of the invention emerge clearly from the appended claims, and the advantages of the invention will better emerge from the detailed

descπption that follows, made with reference to the accompanying drawings, which represent a non-limiting embodiment of the invetion herein described purely by way of example, and in which: figure 1 is a schematic view, with parts in different scale and represented by blocks, of a possible embodiment of the invention, relating specifically to application thereof in a fuel filling station- figure 2 is a schematic front view, with some parts removed and others represented by blocks, of a possible embodiment of a fuel distributor made according to the present invention; figure 3 is a block diagram relating to the carrying out of the method of the invention. With reference to the figures of the drawings, and in particular to the diagram of figure 3, the method for the collection of gassy residues in refuelling plants and in fuel tanks includes the following phases. First the gassy residues are removed during the fuel erogation phase.

The fuel erogation, for example, might be a refuelling of a motor vehicle at a fuel filling station, or by the filliπg-up of a tanker truck at a refinery or fuel storage plant, or by the unloading of fuel from a tanker truck into a fuel filling station. The reference made above to the erogation phase refers specifically to any operations connected with the dispensing of the fuel, including the collection of gassy residues contained in a fixed or mobile tank used for containing fuel . In figure 3 block 1 represents the "source" of erogation, while block 2 indicates the "destination" of the fuel and E represents a possible erogation path.

The phase indicated using the letter P involves the removal of the gassy residues of the fuel, which can be performed at the same time as the filling operation, as in

the case of a motor vehicle in a filling station, or can be carried out subsequently, as in the case of gassy residues from a fixed or mobile tank. The subsequent phase involves condensing, using special means represented by block 3, the gassy residues up until they pass into the liquid state.

Condensation can be performed, as mentioned above, in various ways. One possible procedure is to cool the gassy residues by means of a refrigeration unit, up until a liquid is obtained.

The liquid obtained thus is then reintroduced into the fuel erogation circuit (by sending same to source 1), as shown by path R of figure 1, or, as indicated by arrow R' (in a broken line) sent to a special collection tank 4 (also shown in a broken line).

In the specific case of fuel distributors, illustrated in figures 1 and 2, the method can include introduction of the liquid obtained (which is the same as the fuel dispensed from the distributor) into the fuel supply circuit at the supply pump.

Figures 1 and 2 are a schematic representation of a fuel distributor 10. The distributor 10 is provided with at least one dispensing pistol 11, for connecting with a mouth 17 of a car 13 fuel tank 12. The dispensing pistol 11 is situated at the free end of a double-conduit pipe 14. One of the two conduits in the pipe 14, the one indicated by 16 in figure 1, which is coaxial to and external of the other conduit 15, erogates the fuel in a direction indicated by E. The remaining conduit 15 connects an end 20 of the pipe 14, which end 20 is sealedly associable to the mouth 17, to an aspiration pump 21. The fuel contained in a tank 22 is sent by a supply pump 23 (in direction E) along the conduit 16 of the pipe 14 to fill the fuel tank 12 The gassy residues denoted by 19, which fill the tank 12 area remaining above

the fuel level 18, are aspirated along the communication holes 15 and sent by the pump 21 in direction P, towards the means for condensing 3. The liquid obtained by action of the means for condensing 3 can be sent to a collection tank 4 (in direction R' , the tank 4 and path 4' being represented in broken lines in figure 1) or reintroduced into the fuel supply circuit, at the supply pump 23, for example by means of a conduit 24. The conduit 24, which represents the means for connecting the means for condensing 3 to the fuel supply pump 23, can be associated to an air separator chamber 25 of the supply pump 23 with a single-acting valve 26 connected to the discharge pipe 27 of the separator chamber 25, as illustrated in figure 2. The apparatus can be associated, with a connection represented by 28 in a broken line in figure 2, to the control panel 29 of the fuel distributor 10. In this way, at least the aspiration pump 23 and the means for condensing 3 are activatable by activation of the dispensing pistol 11. The means for condensing 3 can advantageously be arranged in a zone above the distributor 10, so as to enable the liquid obtained to drop into the supply pump 23. In the case of gassy residue collection in a fixed or mobile tank (such as for example in cases concerning tanker truck-filling station tank or refinery-tanker truck transfer), the apparatus will comprise at least ^* an aspiration pump for the gassy residues connected to a tank access aperture; means for condensing the gassy residues, producing a liquid and means for associating the liquid thus obtained with a collection tank.