CA1048892A - Method and system for handling volatile liquid vapors - Google Patents

Abstract

Abstract of the Disclosure Emission to atmosphere of the vapor of a volatile liquid, such as gasoline, displaced from a receiving tank being filled with the liquid from a liquid storage tank of a liquid dispensing system, is reduced by conveying the displaced vapor from the receiving tank to the storage tank and cooling the vapor and the liquid in the system to a reduced vapor pressure which the system can sustain without vapor emission. In one described embodiment, the displaced vapor is returned directly to the storage tank, and the vapor and liquid in the storage tank are cooled by recirculation of the tank vapor through a cooling circuit, such as a refrigeration circuit. In a second des-cribed embodiment, the displaced vapor from the receiving tank and recirculat-ing vapor from the storage tank are combined and returned to the storage tank through the cooling circuit. Within the flow path of the displaced vapor from the receiving tank is a normally closed pressure responsive valve which opens to permit flow of the displaced vapor into the dispensing system only when the vapor pressure in the receiving tank exceeds atmospheric pressure so as to prevent air leakage into the dispensing system. The vapor pressure in a storage tank located above ground is regulated to balance the vapor and atmos-pheric pressures in such a way as to avoid breathing of the tank in response to atmospheric temperature changes.

Description

i~8892 This invention relates generally to the field of ~tmospheric pollution prevention and control. The invention relates more particularly to a method of and system for handling the vapor of a volatile liquid, such as gasoline, at a liquid dispensing station to prevent vapor emission to the atmosphere when dispensing the liquid into a receiving tank.
As will appear from the ensuing description, the invention may be utilized in a variety of volatile liquid handling systems. One particularly useful application of the invention, however, is controlling the emission of gasoline vapor to the atmosphere at gasoline dispensing stations, such as bulk gasoline loading stations or distribution plants, service stations, and the like, when dispensing gasoline into automative fuel tanks, gasoline trans-port tankers, and the like. The invention will be described in connection with the service station application. With regard to bulk loading stations, it should be noted that the gasoline vapor emission problem is particularly serious, first because of the large volume of gasoline handled and second, . ..
because of atmospheric heating as well as breathing of the storage tanks which are commonly located above ground.
When the fuel tank of a gasoline powered machine, such as an automobile, truck, boat or the like, is filled with gasoline from a gasoline dispenser or pump of the kind in current use at gasoline dispensing stations, the liquid gasoline entering the tank displaces gasoline fumes or vapor from the tank. Moreover, the turbulent flow of the entering gasoline produces additional gasoline vapor which is also displaced from the tank. This dis-placed gasoline vapor, if permitted to vent to atmosphere, would constitute a major source of air pollution. In this regard, it is only necessary to con-sider the enormous volume of gasoline which is dispensed each day, even at a single dispensing station, to fully appreciate the magnitude of air pollution which such gasoline vapors would produce.
An attempt has been made to eliminate this source of air pollution by providing gasoline dispensing systems with a vapor recovery circuit for 4~

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effecting return flow of tne gasoline vapors displaced from fuel tanks to the gasoline storage tanks. Inherent in this method of controlling emission of gasoline vapors into the atmosphere is a problem to which the present inven-tion is addressed. The problem, referred to resides in the fact that the existing vapor recovery systems are capable of sustaining only a relatively low maximum gasoline vapor pressure in the gasoline dispensing system without . .
leakage of gasoline vapors to the atmosphere. This maximum vapor pressureis on the order of two ounces per square inch gage. If the gasoline vapor pressure exceeds this maximum pressure level, gasoline vapor will escape to the atmosphere. Considering that the vapor pressure of gasoline stored at 70F in an underground tank is on the order of 5 p.s.i.a., it is readily apparent that the vapor pressure must be reduced to prevent emission of gaso-line vapors into the atmosphere due solely to the vapor pressure of the stored gasoline. Further reduction of the vapor pressure in the storage tank is necessary to accommodate the gasoline vapors from the fuel tanks which are filled from the gasoline dispensers.
According to the present invention there is provided the method of handling the vapor of a volatile liquid, such as gasoline, at a dispensing station having a liquid dispensing system including at least one storage tank for said liquid and means for dispensing liquid from each storage tank into receiving tanks, said dispensing means comprises a nozzle insertable into the filler tube of receiving tanks and including a liquid passage through which said liquid enters a receiving tank and a vapor passage through which vapor is displaced from the receiving tank, comprising the steps of: efecting flow of the displaced vapor from receiving tanks to a storage tank, blocking displaced vapor flow through said vapor passage when the pressure in the receiving tank is less than ambient pressure, recirculating vapor from each - r~$~ storage tank, through~t~ vapor cooling zone, back to a storage tank, cooling the vapor within said cooling zone to reduce the vapor pressure in said dis-pensing system, and returning to a storage tank liquid condensate evolved in ,:

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said cooling zone.
Thus the vapor and liquid in the dispensing system is cooled to a reduced vapor pressure equal to or less than the maximum vapor pressure which the dispensing system will sustain without vapor emission to atmosphere. As ; noted earlier, in the case of gasoline, this maximum vapor pressure is on the order of two ounces per square inch gage. The rate of heat transfer from the vapor to the vapor cooling medium is regulated in response to the vapor pres-sure in the dispensing system to maintain the vapor pressure at its required low level. The liquid condensate evolved in the vapor cooling process is returned to the storage tank. The invention is described in connection with the dispensing of gasoline at automobile service stations and the like. ~low-ever, it will become apparent as the description proceeds that the invention may be utilized to advantage in any gasoline handling facility which presents the described vapor emission problem including, for example, bulk gasoline loading stations.
From another aspect, the invention provides a system for handling the vapor of a volatile liquid, such as gasoline, at a dispensing station having a liquid dispensing system including at least one storage tank for said liquid and means for dispensing liquid from each storage tank into receiving tanks, wherein said dispensing means comprises a nozzle insertable into the filler tube of receiving tanks and including a liquid passage through which said liquid enters a receiving tank and a vapor passage through which vapor is displaced from the receiving tank, comprising: means for effecting flow of the displaced vapor from receiving tanks through said vapor passage to a stor-age tank, pressure responsive valve means for blocking displaced vapor flow through said vaporpassage when the pressure in the receiving tank is less than ambient pressure, a vapor cooling circuit including a vapor cooling zone, means for recirculating vapor from each storage tank through said cooling zone, back to a storage tank, means within said cooling zone for cooling the vapor flowing through said cooling zone to reduce the vapor pressure in said dis-10~89Z
pensing system, and means for returning to a storage tank liquid condensate evolved in said cooling zone.
Two gasoline dispensing systems are described. Each described system embodies the usual service station dispensing components including storage tanks for containing different grades of gasoline and gasoline dis-pensers for the various grades. The nozzle and hose of each dispenser con-tain a vapor passage through which gasoline vapor is displaced from an auto-mobile fuel tank being filled from the dispenser. This displaced vapor from a fuel tank is preferably conveyed to the storage tank containing the heaviest lo leaded grade of gasoline. For convenience in the ensuing description, this storage tank which receives the displaced vapor is referred to as the vapor collection tank or simply collection tank. Gasoline vapor from all the stor-age tanks is recirculated through a refrigeration zone wherein the vapor is cooled to the desired vapor pressure. The cooled vapor and the liquid gasoline condensate produced in the refrigeration zone are returned to the vapor collection tank.
In one described gasoline dispensing system of the invention, the displaced vapor passages of the several gasoline dispensers communicate to the recirculating flow path of the storage tank vapors upstream of the vapor refrigeration and condensation zone. Accordingly, the displaced vapors are combined with the recirculating storage tank vapors and flow with the latter through the refrigeration zone to the vapor collection tank. Flow of the combined vapors through the refrigeration zone to the collection tank is in-- duced by a pump or blower upstream of the zone. This pump or blower creates in the displaced vapor passages of the gasoline dispensers a reduced pressure for inducing inflow of displaced vapors from fuel tanks. Flow of the dis-placed vapors to the recirculation flow path of the storage tank vapors occurs through a low point to which gravitates any liquid gasoline in the flow path resulting from condensation or splashing of the gasoline in a fuel tank being filled. This low point connects to the vapor collection tank through a vapor iO41~92 seal for flow of liquid gasoline from the low point to the tank. In this embodiment, a normally closed pressure responsive valve is placed in the dis-placed vapor passage of each dispenser. This valve normally blocks the vapor passage and is set to open in response to the vapor pressure in the fuel tank only when this pressure is greater than atmospheric pressure so as to prevent drawing of air into the dispensing system. According to another fea-ture, the dispensing nozzle of each gasoline dispenser is equipped with both gasoline and vapor valves operated by a common actuator. These valves are opened and closed simultaneously by the actuator to simultaneously open and close the gasoline dispensing and displaced vapor passages of the dispenser.
In some gasoline dispensing systems, such as most bulk plants, the gasoline storage tanksmay be located above ground. Such tanks are subject to breathing due to changes in the gasoline vapor pressure with atmospheric temperature changes. Such breathing of the tanks may be reduced or eliminated by providing the tanks with a heating and cooling system responsive to a con-trol parameter, such as the difference between tank pressure and atmospheric pressure, for maintaining tank pressure substantially equal to atmospheric pressure.
Gasoline dispensing stations present another potential method of gasoline vapor emission to the atmosphere, namely displacement of the vapors from the storage tanks when the latter are filled from a tanker truck. The vapor handling system of the present invention is not designed to process these vapors, except possible for that portion of the vapors which are forced through the vapor cooling circuit because of their relatively high vapor pres-sure due to the relatively high temperature of the gasoline in a tanker truck.
~ Rather, provision is made for displacement of the vapors back to the tanker - truck for return to the bulk processing plant.
Figure 1 is a flow diagram of a gasoline dispensing system embody-ing a vapor handling system according to the invention;

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Figure 2 shows in fragmentary fashion a dispensing system with an above ground gasoline storage tank;
Figure 3 illustrates a modified vapor cooling chamber for the vapor handling system;
Figure 4 illustrates gasoline service station embodying a modi-; fied gasoline dispensing system according to the invention;Figure 5 is an enlarged view, partially in section> of a gasoline dispensing nozzle and associated components utilized in the service station system of Figures 4; and Figure 6 is a flow diagram of the gasoline dispensing system in . Figure 4.
~ Referring first to Figure 1, the illustrated volatile liquid dis-pensing system 10 is a gasoline dispensing system located at a gasoline dis-pensing station which is assumed to be an automotive service station, that is a gasoline station, but which may be a bulk gasoline processing facility, or other gasoline dispensing station. The gasoline dispensing system 10 includes a vapor recovery means and, except for such vapor recovery means, is conven-tional. Accordingly, it is unnecessary to either describe or illustrate the dispensing system per se in elaborate detail.
Suffice it to say that the gasoline dispensing system 10 shown - has dispensing islands 12 each including a number of gasoline dispensers 14 commonly referred to as gasoline pumps. In the particular dispensing system shown, each island 12 has three dispensers 14 for dispensing three different grades of gasoline. The corresponding dispensers on the islands are connec-ted through gasoline supply conduits 16 to common gasoline storage tanks 18.
That is to say, each tank 18 is connected through a supply conduit 16 to two dispensers which dispense the particular grade of gasoline contained in the tank.
Each gasoline dispenser 14 is conventional and has a hose terminat-ing in a dispensing nozzle for insertion into the filler tube of an automotive 1(~4~9~
fuel tank and a pump for pumping gasoline from the corresponding storage tank 18 through the respective supply conduit 16, hose and nozzle into the fuel tank. It will be understood, of course, that each dispenser also includes a flow meter for measuring and indicating the number of gallons dispensed and their total cost, valving and switches for controlling the gasoline flow and gasoline pump, and other elements found in a standard gasoline dispenser.
As noted earlier, when gasoline is dispensed into the fuel tank of an automotive vehicle, gasoline vapors are displaced from the tank. These vapors, if released into the atmosphere, would constitute a major source of air pollution. In order to alleviate this air pollution, the present gasoline dispensing system is provided with a vapor recovery means20 for cooling and ; conveying the displaced vapors to the gasoline storage tank 18 containing the heaviest leaded gasoline, as explained presently. As noted earlier, this tank is referred to herein as a vapor collection tank or simply collection tank and is assumed to be the center tank in Figure 1.
It will be recalled from the earlier discussion that the existing gasoline dispensing systems having provision for displaced vapor recovery are capable of preventing gasoline vapor escape or emission to the atmosphere only when the gasoline vapor pressure in the gasoline dispensing system is on the order of two ounces per square inch or less. If the vapor pressure exceeds this maximum pressure level, gasoline displaced from a fuel tank being filled will escape to atmosphere past the seal between the dispenser nozzle and fuel tank filler pipe. The vapor recovery means 20 of the present invention is designed to maintain the vapor pressure in the gasoline dispensing system 10 - at or below this maximum pressure level so as to materially reduce or prevent gasoline vapor release to the atmosphere when filling aùtomotive fuel tanks.
Vapor recovery means 20 comprises vapor passages 22 through which gasoline vapors displaced from fuel tanks being filled from the dispensers 14 are conveyed to the center storage tank 18 (vapor collection tank) and a vapor cooling circuit 24 through which gasoline vapors in the storage tanks 18 are )4889~
recirculated to cool and condense the vapors. This cooling circuit includes ,- a vapor cooling means 25 having a vapor cooling and condensing chamber 26 pro-viding a vapor cooling zone 28) a vapor inflow conduit 30 leading from the vapor space in each gasoline storage tank 18 to the cooling chamber, and a vapor and condensate return conduit 32 leading from the cooling chamber to the . center gasoline storage tank 18. The dispenser vapor passages 22 extend through and along the dispenser nozzles and hoses and connect to a conduit leading to the center storage tank, such that the vapors displaced from fuel tanks being filled are conveyed to the latter tank. Gasoline vapors in the upper vapor spaces of the storage tanks 18 flow through the condui,ts 30 to the cooling chamber 26 where the vapors are cooled to reduce their pressure to or below the maximum pressure (two ounces per square inch gage) which the vapor recovery means 20 will sustain without vapor release to the atmosphere. The cooled vapors and condensate return through conduit 32 to the center storage tank.
The vapors entering the cooling chamber 26 are cooled by heat transfer to a cooling medium 34 located within the cooling zone 28 in the path ,' of the entering vapors. In this case, the cooling medium comprises the cooling or refrigerating coils of a refrigeration unit 36. This refrigeration unit ,~ recirculates refrigerant through the coils 34 to cool or chill the entering gasoline vapors to the required low temperature and pressure. A baffle or distributor 38 is placed between the coils and the vapor inlet to the coo]ing chamber 26 to distribute or deflect the vapors generally uniformly over the coils. The cooling chamber 26 and refrigeration unit 36 are located remote , from one another and from the storage tanks 18 and have a sealed or flame proof construction to eliminate the hazard of gasoline v~apor ignition by sparks from the refrigeration unit.
'- Refrigeration unit 36 is controlled by a pressure sensitive switch 40 in the vapor inflow line to the cooling chamber 26. Switch 40 is , 30 set to activate the refrigeration unit for cooling the gasoline vapors enter-~4~9Z
ing the chamber when the vapor pressure in the inflow line rises to some pre-set pressure level at or below the two ounce maximum pressure level referred to earlier. The switch inactivates the unit when the vapor pressure drops to some lower preset level, thus to maintain the vapor pressure at the proper low pressure level required to avoid gasoline vapor emission to the atmosphere.
In the particular vapor recovery means illustrated the vapor pressure differential between the storage tanks 18 and the cooling chamber 26 is utilized to transport gasoline vapors from the tanks to the chamber.
Return flow of the chilled vapors and condensate from the cooling chambcr to the cen~er storage tank occurs by gravity. To this end, the cooling chamber is located above the level of the storage tanks. The vapor inflow conduits 30 connect to the top of the chamber and the vapor return conduit 32 extends from the bottom of the chamber. In connection with the gravity return of the chilled vapors, it will be understood that cooling the relatively warm gaso-line vapors entering the cooling chamber 26 increases their density such that the chilled vapors settle to the bottom of the chamber and then gravitate back to the center storage tank.
The chilled vapors and condensate exit from the bottom of the cooling chamber 26 through vapor and condensate outlets 42 and 44, respective-ly. The vapor outlet 42 comprises a stand pipe 46 arising above the normal level L of the condensate C in the bottom of the chamber and an inverted dome 48 mounted over the stand pipe in a manner such that only the coldest and most dense vapor directly above the condensate may enter the stand pipe. The condensate outlet 44 comprises a stand pipe 50 arising to the normal conden-sate level L and an inverted dome 52 mounted over the stand pipeand extending below the condensate level, such that only condensate ma~y exit through the stand pipe.
If necessary, vapor recirculation through the vapor cooling circuit 24 may be assisted by mechanical means such as a fan, blower, or the like.

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It will be understood from the foregoing description, that the vapor cooling circuit 24 is effective to maintain the gasoline vapor pressure - in the gasoline dispensing system 10 at or below the two ounce pressure level necessary to avoid release of gasoline vapors to the atmosphere when filling automotive fuel tanks. In the event that the cooling circuit should fail, it may be necessary to vent the excess vapor pressure to atmosphere. To this end, the cooling circuit has a pressure relief valve 54 which is set to vent the system when the vapor pressure rises to some preset level, such as 1 p.s i. gage.
Storage tanks 18 are filled from a tanker truck 55 through fill lines 56 extending from the tanks to capped couplings 58 (only one shown) for connection to the filling hose 60 of the tanker. The gasoline vapors dis-placed from the tanks are returned to the tanker truck through vapor return ` conduits 62 extending from the tanks to capped couplings 64 ~only one shown) for connection to a vapor return hose 66 of the tanker. It is thus unnecessary for the present dispensing system 10 to process all the latter gasoline vapors, which, because of the relatively high temperature of the gasoline in a tanker truck and the large volume of the storage tanks 18, would require a substan-,.l tially larger vapor cooling circuit than that required to process the vapors - 20 from automotive fuel tanks. The tanker truck 55 transports the vapors back to a bulk gasoline plant or other facility for disposal and processing to liquid form.

~lowever, the tank truck unloading rate into the storage tanks 18 and the vapor pressure of the gasoline in the truck may be such that the vapor cooling circuit 24 will be required to process a portion of the vapors dis-placed from the storage tanks. In this regard, it will be understood that the cooling circuit and the loading vapor conduits must be designed to handle be-tween them all the vapors during loading of the storage tanks. It can be demonstrated that for an average automobile service station, this may be accom-plished with a refrigeration unit 36 of one-ton capacity and vapor conduits on 1~4~9'~
the order of 2" to 3" in diameter. It can be further demonstrated that such refrigeration unit and conduit sizes are capable of handling the vapors with-out opening of the pressure relief valve 54.
In the gasoline dispensing system of Figure 1, the gasoline stor-age tanks 18 are buried in the ground. Some storage tanks, however, may be above ground, as in Figure 2. In this case, the tanks tend to "breathe", as . the vapor pressure of the stored gasoline changes with changes in the atmos-pheric temperature. To avoid this breathing) it may be desirable or necessary ; to provide a heater 68 for heating the stored gasoline when the temperature .:; 10 drops to maintain the gasoline vapor pressure near atmospheric pressure. The heater is controlled by a pressure switch 70 responsive to the vapor pressure in the tank.
Figure 3 shows a vapor cooling chamber 72 for the present vapor handling system 11 having modified chilled vapor and condensate outlets 74, 76.
Outlet 74 is a combined vapor and condensate outlet including a stand pipe 78 rising to the normal condensate level L in the chamber. Over this stand pipe is a sleeve 80 which extends above and below the condensate level. An inver-ted dome 82 is mounted over the sleeve. Chilled vapor exits through the annular space between the dome 82 and sleeve 80 and then through the stand pipe 78. Condensate exits through the annular space between the sleeve 80 and stand pipe 78 and then through the stand pipe. Outlet 76 is a condensate drain controlled by a valve 84 for rapidly draining condensate from the cool-ing chamber.
The gasoline dispensing system 100 of Figures 4-6 is generally similar to that of Figure 1 and like the latter system has a number of gasoline dispensers or pumps 102 located on islands 103 and connec~ted through supply conduits 106 to underground storage tanks 104 containing different grades of gasoline. Each dispenser 102 has a hose 108 terminating in a dispensing nozzle 110 for insertion into the filler tube of an automotive fuel tank. Con-nected in the supply conduits 106 are pumps 112 for pumping gasoline from the :.

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storage tanks 104 to their respective dispensers 102. The gasoline is dis-pensed from a dispenser to a vehicle fuel tank through the dispenser hose 108 and nozzle 110. The dispensing system 100 also includes a vapor recovery means 114 for recovering the gasoline vapor displaced from a fuel tank during filling of the tank from a dispenser and cooling the vapor in the dispensing system to the reduced vapor pressure necessary to avoid escape of vapor to the atmosphere.

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Vapor recovery means 114 is similar to the vapor recovery means embodied in the dispensing system of Figure 1. Thus, the vapor recovery means 114 comprises vapor return passages 116 (Figure 5) which extend through the nozzles 110 and hoses 108 of the gasoline dispensers 102 and vapor conduits 118 through which gasoline vapor displaced from fuel tanks being filled from the dispensers flows to the storage tank 104 which serves as the vapor collec-tion tank (center tank). Vapor recovery means 114 also includes vapor cooling means 120 through which gasoline vapor in the storage tanks 104 is recirculat-ed to cool the gasoline vapor and liquid in the dispensing system to the reduced vapor pressure necessary to avoid vapor emission to the atmosphere.
The cooled gasoline vapor and liquid gasoline condensate are returned to the center ~vapor collection) storage tank 104.
At this point, it is significant to recall that in the gasoline dispensing system of Figure 1, the vapor displaced from a fuel tank being filled flows directly to the vapor collection storage tank under the action of gravity and vapor pressure differential. Moreover, the dispensing system of Figure 1 is maintained at the reduced vapor pressure necessary to avoid vapor emission to the atmosphere by recirculating vapor from the storage tanks, through a vapor cooling path separate from the flow path of the displaced vapor from the fuel tank to the vapor collection tank. Return of the cooled vapor to the vapor collection tank occurs under the action of gravity and vapor pressure differential.
In contrast, in the gasoline dispensing system 100 of Figures ~4~g2 4-6, the vapor displaced from a fuel tank being filled and the recirculating vapor from the gasoline storage tanks are combined and flow together to the vapor collection tank through a common flow path containing the vapor cooling means 120 and a blower or pump 121 for inducing the flow of the combined vapors through the cooling means to the collection tank.
The dispensing system lO0 will now be described in more detail.
Turning first to Figure 5, the gasoline dispensing nozzle 110 of each gasoline dispenser 102 embodies generally conventional dispensing nozzle structure including a gasoline inlet 122 which connects to the dispenser hose 108, a spout 124 for insertion into tl-e filler tube of a vehicle fuel tank, a normal-ly closed dispensing valve 126 between the inlet and spout, and a valve operat-ing mechanism (not shown) activated by a lever 128 for opening the valve to dispense gasoline through the spout in respotlse to depression of the lever.
- A seal 129 is placed about the spout 124 for sealing the fuel tank filler tube.
It should be noted that the nozzle, and particularly its conventional nozzle structure, has been illustrated in simplified, somewhat diagrammatic fashion for the sake of clarity.
According to the present invention, the nozzle 110 is equipped with a vapor valve 130 which opens and closes with the gasoline dispensing valve 126. This vapor valve has a vapor inlet 132 and a vapor outlet 134.
Connected to the inlet 132 is a tube 136 which extends along and is secured in any convenient way to the nozzle spout 124 for insertion with the spout into a fuel tank filler tube. Connected to the vapor valve outlet 134 is a tube 138 which extends along and is secured in any convenient way to the nozzle hose 108. Tube 138 connects to the respective displaced vapor conduit 118. The vapor tubes 136, 138 provide the vapor return passage 115 of the respective dispenser.
The vapor conduits 118 from the gasoline dispensers 102 connect to negative or suction side of the blower 121 through common vapor conduits 140, 141. Conduit 140 has a low point 142 to which gravitates any liquid gasoline in the conduit due to condensation or splashing of gasoline from fuel tanks being filled into the nozzle vapor passages 116. Liquid gasoline drains from this low point to the center vapor collection tank 104 through a drain conduit 143. The upper vapor spaces in the storage tanks 104 communi-cate to the negative or suction side of blower 121 through conduits 144, an elevated manifold 145, and a common conduit 146. As explained below, the positive or exhaust side of blower connects to the vapor cooling means 120.
The vapor cooling means 120 of the dispensing system 100, like that of the dispensing system of Figure 1, comprises a vapor cooling and condensing chamber 148 (Figure 6) and a refrigeration unit 150 for recirculat-ing cold refrigerant through the vapor cooling and condensing zone lSl of the chamber. The positive side of blower 121 exhausts into the upper end of the cooling chamber 148. Accordingly, the combined displaced vapor from fuel tanks and recirculation StOrage tank vapor flow through and are cooled and condensed within the cooling zone 151. The liquid gasoline condensate returns through conduit 153 to the center tank 104, which contains the most leaded gasoline.
The cooled vapor returns to all three tanks 104 through conduit 152 and its branches 152a. The drain and condensate conduits 143, 153 extend to the - bottom of the collection tank and open to the tank through liquid seals 154.
It will now be understood that the blower 121 acts to recirculate vapor from all the storage tanks 104, through the vapor cooling means 120, to the center vapor recovery tank and to induce flow of vapor displaced from fuel tanks being filled through the displaced vapor passages 116, 118, 140~ 141 to the recirculating flow path of the storage tank vapor. The displaced vapor combines with the recirculating tank vapor at the blower inlet, and flows with the latter vapor, through the cooling means to the vapor collection tank. A
safety relief valve 156 is provided in the elevated manifold 145 for venting vapor to atmosphere in the event of excessive vapor pressure in the system due to failure of the cooling means 120.
According to a feature of the invention, pressure responsive : l~J4~892 shut-off valves 158 may be connected in the individual displaced vapor con-duits 118 from the gasoline dispensers 102. These valves are normally closed and open in response to a preset pressure slightly greater than atmospheric pressure in the fuel tanks being filled.
The dispensing system 100 has lines 160, 162 for filling and evacuating displaced vapor from the storage tanks 104, like the dispensing system of ~igure l.
The operation of the dispensing system 100 is readily understand-able from the preceding description. Thus, gasoline vapor in the gasoline storage tanks 104 continues to recirculate under the actiorl of blower 121 through the vapor cooling means 120 to maintain the vapor in the dispensing system at the required low vapor pressure to prevent vapor escape to atmos-phere. When filling a vehicle fuel tank from a gasoline dispenser 102, its dispensing nozzle 110 is inserted into the fuel tank filier tube and the nozzle lever 128 is depressed to open the nozzle dispensing and vapor valves 126, 130. Gasoline is thereby dispensed into the tank and tends to displace gasoline vapor from the tank. Opening of the vapor valve 130 exposes the cor-responding dispenser vapor shut-off valve 158 to the pressure in the fuel tank through the vapor passage 116. Initially, this dispenser vapor shut-off valve 158 is closed. When the internal pressure in the fuel tank builds up to the required pressure level slightly greater than atmospheric pressure the valve 158 opens. This permits flow of the displaced vapor from the fuel tank to the blower 121, where the displaced vapor combines with the recirculating storage tank vapor and flows witn the latter through the vapor cooling means 120 to the vapor collection tank 104. Valves 160 are provided to block leak-age of air into the dispensing system through the disp~aced vapor passages 116.

Claims (18)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The method of handling the vapor of a volatile liquid, such as gasoline, at a dispensing station having a liquid dispensing system including at least one storage tank for said liquid and means for dispensing liquid from the or each storage tank into receiving tanks, said dispensing means comprises a nozzle insertable into the filler tube of receiving tanks and including a liquid passage through which said liquid enters a receiving tank and a vapor passage through which vapor is displaced from the receiving tank, comprising the steps of: effecting flow of the displaced vapor from receiving tanks to a storage tank, blocking displaced vapor flow through said vapor passage when the pressure in the receiving tank is less than ambient pressure, recirculating vapor from the or each storage tank, through a vapor cooling zone, back to a storage tank, cooling the vapor within said cooling zone to reduce the vapor pressure in said dispensing system, and returning to a storage tank liquid condensate evolved in said cooling zone.

2. The vapor handling method of Claim 1 wherein: said method includes the additional steps of sensing the vapor pressure in said system and regulating the rate of vapor cooling in response to the sensed vapor pressure.

3. The vapor handling method of Claim 1 wherein: flow of displaced vapor from receiving tanks to the storage tank which receives the displaced vapor and recirculation of storage tank vapor through said cooling zone is effected by mechanical pumping action.

4. The vapor handling method of Claim 3 wherein: displaced vapor from receiving tanks and the recirculating storage tank vapor are combined and flow together through said cooling zone.

5. The vapor handling method of Claim 4 wherein: the flow path of displaced vapor from receiving tanks to the point at which the displaced vapor combines with the recirculating storage tank vapor contains a low point to which gravitates liquid condensate produced in the flow path and any liquid entering the flow path from receiving tanks, and said method comprises the further step of draining liquid from said low point to a storage tank.

6. The vapor handling method of Claim 1, 3 or 4 wherein: storage tank is located above ground, and said method includes the additional step of regulating the temperature of the liquid in said above ground storage tank to maintain the vapor pressure therein substantially equal to atmospheric pressure.

7. The vapor handling method of Claim 1, 2 or 3 including the additional step of: simultaneously regulating liquid and displaced vapor flow through said passages in a manner such as to open said vapor passage to flow of displaced vapor only during dispensing of said liquid into a receiving tank.

8. The vapor handling method of Claim 1, 2 or 3 wherein: said dispensing station is a gasoline dispensing station having several storage tanks for different grades of gasoline; and wherein condensate formed from both displaced vapor from receiving tanks and the cooled recirculating vapor from said storage tanks is returned to the storage tank containing the heaviest leaded gasoline.

9. The vapor handling method of Claim 4 or 5 including the additional step of: simultaneously regulating liquid and displaced vapor flow through said passages in a manner such as to open said vapor passage to flow of displaced vapor only during dispensing of said liquid into a receiving tank.

10. A system for handling the vapor of a volatile liquid, such as gasoline, at a dispensing station having a liquid dispensing system including at least one storage tank for said liquid and means for dispensing liquid from the or each storage tank into receiving tanks, wherein said dispensing means comprises a nozzle insertable into the filler tube of receiving tanks and including a liquid passage through which said liquid enters a receiving tank and a vapor passage through which vapor is displaced from the receiving tank, comprising: means for effecting flow of the displaced vapor from receiving tanks through said vapor passage to a storage tank, pressure responsive valve means for blocking displaced vapor flow through said vapor passage when the pressure in the receiving tank is less than ambient pressure, a vapor cooling circuit including a vapor cooling zone, means for recirculat-ing vapor from the or each storage tank through said cooling zone, back to a storage tank, means within said cooling zone for cooling the vapor flowing through said cooling zone to reduce the vapor pressure in said dispensing system, and means for returning to a storage tank liquid condensate evolved in said cooling zone.

11. The vapor handling system according to Claim 10, including:
means for sensing the vapor pressure in said system and regulating the rate of vapor cooling in response to the sensed vapor pressure.

12. The vapor handling system according to Claim 10 wherein: said means for effecting displaced vapor flow and said means for recirculating storage tank vapor comprise mechanical pumping means.

13. The vapor handling system according to Claim 10 wherein: said means for effecting displaced vapor flow comprises conduit means connected to said vapor passage for conveying displaced vapor from receiving tanks to said vapor cooling circuit to combine with the recirculating storage tank vapor and flow with the latter vapor through said cooling zone.

14. The vapour handling system according to Claim 13 wherein:
said conduit means has a low point to which gravitates liquid condensate produced in the conduit means and any liquid entering the conduit means from receiving tanks, and a drain conduit connecting said low point of said conduit means to a storage tank for draining liquid from said low point to the latter tank.

15. The vapor handling system according to Claim 10 wherein:
a storage tank is located above ground, and means for regulating the temperature of the vapour in said above ground storage tank to maintain the vapor pressure therein substantially equal to atmospheric pressure.

16. A vapor handling system according to Claim 10 including:
means for simultaneously regulating liquid and displaced vapour flow through said passages in a manner such as to open said vapor passage to flow of displaced vapor only during dispensing of said liquid into a receiving tank.

17. The vapor handling system according to Claim 10, 11 or 12 wherein: said dispensing station is a gasoline dispensing station having several storage tanks for different grades of gasoline; and condensate formed from both displaced vapor from receiving tanks and the cooled recirculating vapor from said storage tanks are returned to the storage tank containing the heaviest leaded gasoline.

18. A vapor handling system according to Claim 10, 11 or 12 including: means for simultaneously regulating liquid and displaced vapor flow through said passages in a manner such as to open said vapor passage to flow of displaced vapor only during dispensing of said liquid into a receiving tank.