HK1065521B - Tank pressure management system - Google Patents

Description

Tank pressure regulating system

Technical Field

The present invention relates generally to tank pressure regulation systems, and more particularly to systems and methods for regulating pressure in an oil storage tank.

Technical Field

At a service station, as is well known in the art, a person can fill the vehicle's fuel tank from an underground storage tank through a nozzle. Without a vapor recovery system, when liquid gasoline is vented of vapor, the vapor is typically vented to the atmosphere from the vehicle's fuel tank and/or during refueling.

To address the issue of steam loss at the nozzle, a "class II" steam recovery system is installed. More specifically, a vapor recovery system is provided on the fuel supply nozzle to reduce the amount of vapor discharged that may flow into the atmosphere when the liquid is discharged. One such vapor recovery system is known as a "balanced" vapor recovery system having a rubber sleeve surrounding the fuel delivery nozzle that extends to form a seal with the filler tube of the vehicle fuel tank. The steam overflowing from the automobile oil tank is collected and flows into the oil storage tank through the rubber sleeve.

Another known class II vapor recovery system used with fuel delivery nozzles includes a "vacuum assisted" vapor recovery system. Such systems employ a vacuum pump to collect vapor from the vehicle tank through a passage in the nozzle and return the removed vapor to the tank.

While class II vapor recovery systems have indicated some of the problems found in the prior art, it has been found later that such systems can create adverse pressure on the storage tank when more vapor is returned to the tank than is added to the vehicle's fuel tank. As a result, vehicles have been developed with on-board refueling vapor recovery devices (ORVRs) to prevent vapor from escaping the vehicle fuel tank. However, it has been found that the class II vapor recovery system, rather than collecting vapor from the ORVR vehicle, collects fresh air and, therefore, also presents a problem of pressurizing the oil reservoir. Thus, as the ORVR vehicle begins to be used, it is imperative to ensure that the conditions in which both vapor recovery systems (ORVR and class II) coexist do not produce more emissions than before (when class II is installed alone) due to over-pressure in the storage tank.

Initially, for ORVR equipped vehicles, the class II vapor recovery system is adapted to slow or stop class II vapor recovery. To this end, various sensors are incorporated into the class II system to detect the presence of the ORVR vehicle and regulate vapor recovery accordingly. While such class II sensors are effective in slowing or stopping vapor recovery from the ORVR vehicle, a problem remains in that the vehicle cannot be refueled because the class II system maintains tank pressure by exchanging gasoline and vapor with the vehicle's fuel tanks. Thus, the vehicle is not being refueled and the free vaporization of the gasoline pressurizes the storage tank (e.g., due to higher temperatures or simply due to the natural tendency of the hydrocarbon fluid to vaporize). To address this problem, new systems have been developed to regulate the reservoir pressure.

More recently, systems employing high-tech "membrane technology" have been utilized to regulate the pressure in the storage tank. For example, in U.S. patent No. 5,464,466 to gilbaco, steam from an oil storage tank is circulated by a pump through a membrane that separates clean air from hydrocarbon vapors, which are vented to the atmosphere, and the hydrocarbon vapors are returned to the oil storage tank.

Another system that employs "membrane technology" includes applicant's own system, known as a "vapor storage system". The vapor storage system condenses the vapor from the storage tank to form liquid gasoline, and then filters the remaining hydrocarbon vapors through a membrane. Upon separation and membrane filtration, the liquid gasoline and saturated steam are returned to the storage tank and clean air is released to the atmosphere.

The present invention addresses some of the problems of systems employing "membrane technology" and is based, in the first place, on the recognition that membranes in such systems may fail, potentially leading to the discharge of hazardous hydrocarbon vapors into the surrounding environment. Furthermore, by means of the invention, the tank pressure can be regulated without releasing any air or steam into the surrounding environment.

Another problem, which is once again emphasized by the present invention, is that the membranes used in "membrane technology" eventually wear out and need to be replaced. Membrane replacement can be expensive and can result in undesirable emissions if not replaced properly or timely. Furthermore, the tank pressure regulating system needs to be closed at the time of membrane replacement, and thus, it is possible to increase the pressure in the tank. If the pressure in the tank rises above atmospheric pressure, a leak or release of pressure to be prevented by the pressure regulating system can occur.

Thus, while systems employing membrane technology are certainly helpful for pressure regulation in oil storage tanks, there is room for further improvement in tank pressure regulation systems with improved performance. It is therefore desirable to regulate the tank pressure in an efficient, cost-effective manner, and without the use of membranes and/or with other techniques than membranes.

Disclosure of the invention

Accordingly, the present invention seeks to solve the above problems and disadvantages and to improve upon existing tank pressure regulation systems. More specifically, it is an object of the present invention to provide a closed system and method for regulating the pressure of an oil storage tank.

To achieve the foregoing and other objects, and in accordance with the exemplary embodiments of the invention, a tank pressure regulation system includes a vapor condensation system in fluid communication with a storage tank, and a collection tank in fluid communication with the vapor condensation system and a storage tank. In one embodiment, the collection tank includes an air/vapor outlet and a liquid outlet, an air/vapor conduit coupling the air/vapor outlet of the collection tank to a storage tank, and a liquid conduit coupling the liquid outlet of the collection tank to a storage tank. Thus, the tank pressure regulation system of the present invention provides a closed system for condensing liquid gasoline from air/vapor to reduce the tank pressure and return all of the air, vapor and liquid to an oil storage tank without venting the air or vapor to the atmosphere.

To further achieve the above and other objects, there is provided, according to an embodiment of the present invention, a method of adjusting air/vapor pressure of an oil storage tank, including the steps of: monitoring the pressure in an oil storage tank, removing air/vapor from the oil storage tank when the monitored pressure reaches a first predetermined value, separating liquid from the air/vapor, returning all remaining air/vapor to an oil storage tank, and returning the separated liquid to an oil storage tank. The present invention thus provides a method for condensing liquid gasoline in air/vapor to reduce the pressure in the storage tank and returning all of the air, vapor and liquid to a storage tank without venting the air or vapor to the atmosphere.

Other embodiments, combinations, advantages and objects of the present invention will be apparent to those skilled in the art from the following description. Alternate embodiments of the present invention are also illustrated and described below for purposes of illustration. It will be understood that the invention includes other various aspects, objects and embodiments, all without departing from the scope of the invention. Accordingly, the drawings, objects, and descriptions will be regarded as illustrative and exemplary in nature, and not as restrictive.

Drawings

FIG. 1 is a schematic diagram of the piping and control of a system according to an embodiment of the present invention.

Figure 2 is a schematic view of a system according to the invention for a simpler gasoline station.

Detailed Description

Referring now in detail to the drawings in which like numerals indicate like elements, there is shown an example of a closed system 10 for regulating pressure in a storage tank 12. The canister 12 of the present embodiment is suitable for containing hydrocarbons, such as petroleum-based fuels, but may also contain other types of materials, such as non-hydrocarbon volatiles or non-volatile chemicals or fluids.

In fig. 1, the pressure regulation system 10 includes a controller 15, a vapor condensing system 20, a collection tank 30, a liquid conduit 32, an air/vapor conduit 34, and a pressure regulator 42. As shown, the pressure regulating system 10 also includes a liquid discharge valve 40, on/off pressure switches 44 and 45, and high and low safety off pressure switches 48 and 49, all of which are coupled to the controller 15.

The vapor condensing system 20 may include a pressure pump 22 (also referred to as a "compressor"), a motor 24, and a condenser 26. In another embodiment, the vapor condensing system 20 may include any conventional components effective for condensing liquid gasoline in air/vapor. As will be further noted below, a pressure pump 22 selectively draws air/vapor from the storage tank 12 and pushes them through the condensing system. The condensed hydrocarbon liquid (e.g., gasoline) is returned to the tank 12 through a liquid conduit 32 and the air/vapor is returned to the tank 12 through an air/vapor conduit 34. It is desirable that all of the vapor initially removed from the storage tank 12 be condensed and/or otherwise returned to the original storage tank (or to a separate storage tank, not shown) via return lines (32, 34 and 38), and the tank pressure regulation system of the present invention is said to be "closed". Thus, the system and method of the present invention prevents the venting of air/steam to the atmosphere. As will be discussed below, while an emergency ventilation system may be used in conjunction with the system and method of the present invention, it is desirable that the system remain substantially closed during normal operation.

Turning now to the flow of fluid through the pressure regulating system 10 of the illustrated embodiment of the present invention, the controller 15 energizes the motor 24 upon receiving an "on" signal from the cracking pressure switch 44. As will be discussed below, the controller 15 may be implemented by discrete logic on a circuit board to ensure the sequence of operations. When the controller 15 energizes the motor 24, the pressure pump 22 removes air/vapor from the oil reservoir 12. As shown in FIG. 1, a reserve tank suction tube 50 establishes a fluid path from the tank 12 to an inlet 52 of the pressure pump 22. If desired, a canister suction particulate filter 54 may be provided at the suction line of the pressure pump 22 to filter particulates from the air/vapor from the storage tank 12 to which the pressure pump 22 may draw a vacuum. The reservoir suction tube particulate filter 54 may be any type of particulate filter commercially available.

The pressure pump 22 also typically increases the temperature of the air/steam by compression. In one embodiment, the pressure pump 22 may be a rotary vane pump, a diaphragm or any other type of pressure pump and may be driven by a two-motor, single-phase AC motor 24. The pressure pump 22 discharges the air/steam through an outlet or vent 56. High and low safety shutoff pressure switches 48, 49 or the like are shown communicating with the discharge port 56 of the pressure pump 22 for sensing the discharge pressure. The sensed pressure of the exhaust port 56 is communicated to the controller 15.

The pressure pump 22 is shown discharging air/steam to a condenser 26. It is desirable here for the condenser 26 to be implemented by means of an air cooler/radiator and to be cooled by the surrounding air. Further, the condenser 26 may be provided with an external fan (not shown) to assist in the condensing/cooling process. In another embodiment, any conventional heat exchanger may be employed to cool the air/steam. For example, the condenser 26 may be a non-insulated pipe section, or provided by a length of rubber tubing disposed over a pipe.

The condenser 26 condenses the air/steam from the discharge 56 of the pressure pump 22. As the temperature of the air/vapor decreases, the liquid gasoline condenses, forming air/vapor/liquid. In the illustrated embodiment, partially condensed air/vapor/liquid flows from the outlet of the condenser 26 to the inlet of the collection tank 30. The configuration of the collection tank 30 may be any configuration suitable for collecting liquids, including, but not limited to, a typical tube. The collection tank 30 may be sized larger to support larger amounts of air/vapor mixture and liquid, or to accommodate an extended cycle time, as will be discussed later.

The air/vapor/liquid is then naturally separated into liquid and air/vapor mixed portions in the collection tank 30. In one embodiment, the inlet of the collection tank 30 is designed to decelerate the air/vapor/liquid as it enters the collection tank 30, thereby allowing the liquid to "drip" from the air/vapor/liquid and collect at the bottom of the collection tank 30. In another embodiment, the air/vapor/liquid can be physically separated in the collection tank using a steel mesh or other common liquid/gas separation device.

The total pressure in the collection tank 30 increases proportionally with the increase in volume of the air/vapor mixture and liquid within the collection tank 30. As the air/vapor mixture and liquid are released from the collection tank 30, the pressure within the collection tank 30 drops. In the embodiment shown in fig. 1, the collection tank 30 has two outlets, namely one air/vapour outlet 33 and one liquid outlet 31. One air/vapor conduit 34 is coupled to air/vapor outlet 33 and one liquid conduit 32 is coupled to liquid outlet 31. The two tubes (34 and 32) intersect to form a single return tube 38 for returning the air/vapor mixture and liquid to the storage tank 12. However, the air/steam pipe 34 and the liquid pipe 32 may be separately returned to the oil tank 12, if necessary. Further, it should be understood that air/steam tube 34 and liquid tube 32 may be combined to form a single tube, thereby having a single outlet for both the air/steam mixture and the liquid.

In this embodiment, the air/steam line 34 includes a pressure regulator 42 for controlling the system operating pressure. When the pressure in the collection tank 30 exceeds a predetermined pressure value (e.g., 25 p.s.i.), the pressure regulator 42 opens and air/steam is returned to the storage tank 12 via the air/steam line 34. In another embodiment, the system may be configured such that controller 15 sends a signal to drain valve 40 to open when the pressure in collection tank 30 reaches a predetermined value. The pressure of the air/steam mixture in the collection tank 30 pushes the air/steam mixture toward the storage tank 12 from which it came. In another embodiment, a vacuum pump may be provided on the air/vapor line 34 to draw air/vapor toward the oil reservoir 12. In addition, a second or secondary vapor recovery system 20 and collection tank 30 may be provided in the air/vapor line 34, if desired, to further condense the air/vapor mixture and further separate the air/vapor/liquid. The pressure regulator 42 closes as soon as the pressure in the collection tank 30 falls below a predetermined pressure value.

When the pressure pump 22 of the vapour condensation system 20 is in operation, a drain valve 40 (in the illustrated embodiment a solenoid valve) provided on the liquid line 32 is closed. After "closing" the pressure switch 49 generates a signal to the controller 15 to stop the motor 24 of the pressure pump 22 (i.e., when the pressure pump 22 is not in operation), the controller 15 sends a signal to the drain valve 40 to open. In another embodiment described above, the controller 15 may send an open signal to the drain valve 40 when the motor 24 of the pressure pump 22 is in operation. Furthermore, in another embodiment, the drain valve 40 is a pressure actuated or float valve, such that the drain valve 40 may be opened without first receiving a control signal from the controller 15.

The opening of the drain valve 40 allows the liquid collected in the collection tank 30 to drain into the storage tank through the liquid line 32. In another embodiment, air/vapor remaining in collection tank 30 when drain valve 40 is open may also flow through liquid line 32 into tank 12.

In another embodiment, the liquid conduit 32 has an effective downward slope to accommodate gravity flow of condensed liquid to the storage tank 12. In another embodiment, the liquid may be pumped to the storage tank 12. It will be understood by those skilled in the art that the air/vapor mixture and liquid may be returned to more than one storage tank, or to a storage tank other than the one from which the air/vapor originated.

The method of operation of the tank pressure regulation system of the present invention will now be described. The pressure switches 44, 45 monitor the pressure of the storage tank 12. Pressure switches (44 and 45) communicate with the tank 12 to monitor and generate corresponding pressure signals. In the embodiment shown in figure 1, the "on" pressure switch 44 generates a signal when the internal pressure of the canister 12 reaches about 0.1 "w.c. to about 0.25" W.C "(i.e., when the internal pressure of the canister 12 is slightly over-pressurized). It should be appreciated that the pressure switch 44 may generate a signal at any desired predetermined tank pressure. The pressure signal is sent to the controller 15. In the illustrated embodiment, the controller 15 may be implemented by discrete logic of a circuit board for performing a series of operations to be described below. It should be understood, however, that the controller 15 may comprise a PC or other computer that is programmed with a software application to execute the appropriate logic.

When the controller receives a pressure signal from the "on" pressure switch 44, the controller outputs a signal to actuate the motor 24 of the pressure pump 22 to draw air/vapor from the storage tank 12 into the pressure pump 22.

Thus, the liquid gasoline is separated from the air/vapor removed from the storage tank 12. The pressure pump 22 compresses and heats the air/vapor from the storage tank 12, and the compressed air/vapor is then pushed toward the condenser 26. The condenser 26 cools the air/vapor (e.g., with ambient or cooled air) to form an air/vapor/liquid. As described above, the high and low pressure safety switches 48 and 49 monitor the pressure of the air/steam as it is pushed toward the condenser 26. In one embodiment, such as for a refueling setting, when the discharge pressure drops below about 15psig, the low pressure switch 49 generates a low pressure signal that is sent to the controller 15 to activate an alarm, such as the occurrence of certain conditions, and/or to de-energize the pump of the present invention. Conversely, when the discharge pressure exceeds about 25psig, the high pressure switch 48 generates a high pressure signal that is sent to the controller 15 to activate an alarm and/or de-energize the pump of the present invention.

The air/vapor/liquid is then sent to a collection tank 30 where the air/vapor/liquid is separated into an air/vapor mixture and liquid. When the pressure in the collection tank 30 reaches a predetermined value, the pressure regulator 42 opens to allow the air/vapor mixture in the collection tank 30 to return to the storage tank 12 via an air/vapor line 34. In one embodiment, when the pressure in the collection tank 30 reaches a predetermined value, the controller sends an open signal to drain valve 40 to return the liquid and, if desired, the air/vapor mixture to the storage tank 12.

In the illustrated example of a gasoline station, when the internal pressure of the tank 12 is between about-0.1 "w.c. and about-0.5" w.c. (i.e., when the tank 12 has a slight internal vacuum), the "off" pressure switch 45 sends a signal to the controller 15 to de-energize the motor 24 of the pressure pump 22. When the motor 24 is de-energized (i.e., the separation step is complete), the controller 15 sends a signal to the drain valve 40 disposed on the fluid path 32. When drain valve 40 receives a signal from the controller that motor 24 has been de-energized, drain valve 40 opens and the fluid in collection tank 30 returns to storage tank 12 via fluid line 32. As mentioned above, it should be understood that the air/vapor line 34 and the liquid line 32 may be combined to form a single line for both the air/vapor mixture and the liquid, thereby forming a single outlet. In the illustrated embodiment, one cycle is complete as soon as liquid is drained from the collection tank 30.

In another embodiment, the tank pressure regulation system cycles to control the expansion of the vapor in the storage tank. For example, in one embodiment, the system may be designed to operate continuously for approximately ten minutes on a periodic basis (i.e., remove air/vapor, condense air/vapor, separate air/vapor/liquid and return air/vapor mixture and liquid mixture). After about ten minutes, the steam condensation system 20 is turned off for about two minutes and then turned back on if necessary for the canister pressure. In this way, the collection tank 30 can drain and return fluid to the storage tank. As discussed above, one way to increase the cycle time (e.g., the amount of time the system is running continuously) is to increase the size of the collection tank 30. To prevent dangerous levels of pressure in the storage tank, an emergency air vent 60 is provided in one embodiment to relieve pressure. The emergency air opening 60 can be, for example, a solenoid valve or a pressure regulating valve. The emergency port may include a membrane filter, if desired, to prevent release of hydrocarbons to the atmosphere in the event of an emergency. It should be understood, however, that the system 10 does not require operation of the emergency air vent 60 in accordance with the present invention.

The tank pressure regulation system of the present invention may be used alone or in combination with other vapor recovery systems and/or tank pressure regulation systems to regulate the tank pressure. For example, FIG. 2 shows an embodiment of the apparatus wherein the system 10 is used in conjunction with the aforementioned class II vapor recovery system for a simple gasoline station. In another embodiment, the system 10 may be used in conjunction with another tank pressure regulation system (e.g., the steam storage tank described above). In the embodiment shown in fig. 2, the class II system delivers vapor from the service station pump 64 to the storage tanks 12, 112 and 212 via a pump return conduit 66. In this embodiment, each storage tank 12, 112, and 212 contains a different grade of gasoline. To regulate the tank pressure created by the air/vapor returning from the class II system and the gasoline naturally evaporating from the storage tanks 12, 112, and 212, the system 10 removes the air/vapor from the storage tanks 12, 112, and 212 through the tank suction line 50 as described above. Whenever the system 10 separates the air/vapor into liquid and air/vapor mixtures, all of the separated components (liquid and air/vapor mixtures) are returned to a storage tank 12. In the embodiment shown in fig. 2, the system manages three storage tanks 12, 112 and 212, and the separated liquid and air/vapor mixture is returned to the lowest stage of storage tank 12. It should be understood, however, that the liquid gasoline and air/vapor mixture may be returned to any storage tank. Moreover, if desired, the system 10 may provide more than one storage tank 12, 112, 212 so that the separated liquid and air/vapor mixture may be returned to its original tank.

When used in conjunction with other vapor recovery systems or tank pressure regulation systems (e.g., class II or vapor reservoirs), it is envisioned that the tank pressure regulation system of the present invention will be most effective when refueling is slow or during the night when a refueling station is shut off. At this point, other vapor recovery systems cannot control the tank pressure (because they are inactive). In this case, the tank pressure regulation system may condense gasoline at a slightly higher rate than natural gasoline liquid evaporation to reduce the tank pressure when needed.

When used alone, it is envisioned that the tank pressure regulating system 10 of the present invention is effective for regulating the pressure of an oil storage tank throughout the day. In this case, the size or multiples of the size of the components of the tank pressure regulation system may be determined based on the number and/or size of the storage tanks (i.e., pressure control requirements) regulated by the system.

The foregoing description of the various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many variations, modifications, and variations will be apparent to those of ordinary skill in the art. For example, the tank pressure regulating system according to the present invention may be assembled into many different devices and operated in many different ways. Thus, while some alternative embodiments of a tank pressure regulation system have been discussed in detail, other embodiments will be apparent to, or may be readily developed by, those skilled in the art. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variations as discussed above, and all aspects as fall within the spirit and broad scope of the appended claims.

Claims (19)

1. A pressure regulation system for an oil storage tank, comprising:

a vapor condensing system in fluid communication with an oil storage tank;

a collection tank in fluid communication with the vapor condensing system, the collection tank further comprising an air/vapor outlet and a liquid outlet;

a fluid conduit coupling said fluid outlet and the reservoir;

an air/steam conduit coupling said air/steam outlet and an oil storage tank;

the liquid and air/vapor lines provide a closed system to return all air, vapor and liquid from the collection tank to the storage tank.

2. The pressure regulating system of claim 1, further comprising a pressure regulator disposed in the air/steam line.

3. A pressure regulating system as defined in claim 2, wherein the pressure regulator regulates the air/steam line between an on/off state.

4. The pressure regulating system of claim 1, further comprising a drain valve disposed in the fluid conduit.

5. The pressure regulation system of claim 4, wherein the drain valve is configured to open only when the vapor condensation system is not operating.

6. The pressure regulation system of claim 1, further comprising a pressure monitor to monitor the air/steam pressure in the storage tank.

7. A pressure regulating system as claimed in claim 1, wherein the vapour condensation system comprises an ambient air cooler.

8. A method of regulating air/steam pressure in an oil storage tank, comprising the steps of:

monitoring the pressure in the oil storage tank;

removing air/steam from the oil storage tank when the monitored pressure reaches a first predetermined value;

separating liquid from the air/vapor;

returning all remaining air/steam to the storage tank;

returning the liquid to the storage tank.

9. The method of regulating air/steam pressure in an oil storage tank of claim 8, wherein said separating step comprises cooling said air/steam with an ambient cooler.

10. The method of regulating the air/steam pressure of an oil storage tank of claim 8, wherein said liquid is delivered to said oil storage tank through a first outlet of a collection tank and air/steam is delivered to said oil storage tank through a second outlet of a collection tank.

11. A method of regulating pressure in an oil storage tank as claimed in claim 8, wherein said air/vapour and said liquid are returned through an outlet of a collection tank.

12. The method of regulating pressure in an oil storage tank of claim 8, further comprising the step of terminating air/vapor removal when said monitored pressure is below a second predetermined value.

13. The method of regulating pressure in an oil storage tank of claim 8, further comprising the step of closing the drain valve when air/vapor is removed from an oil storage tank.

14. The method of regulating pressure of a storage tank of claim 13, wherein said fluid is delivered to a storage tank after said separating step is completed.

15. A pressure regulation system for an oil storage tank, comprising:

a vapor condensing system in fluid communication with an oil storage tank;

a collection tank in fluid communication with the vapor condensation system, the collection tank further comprising at least one outlet;

a conduit connecting said outlet port to an oil storage tank;

the conduit provides a closed system to return all air, vapor and liquid from the collection tank to the storage tank.

16. The pressure regulating system of claim 15, wherein the conduit is configured to return air/vapor to a storage tank.

17. The pressure regulating system of claim 15, wherein the conduit is configured to return fluid to a storage tank.

18. The pressure regulating system of claim 15, wherein the conduit is configured to return air/vapor and liquid to a storage tank.

19. A pressure regulating system as claimed in claim 1 or 15, wherein the pressure regulating system is coupled with more than one oil storage tank.