EP2344413A1

EP2344413A1 - Fuel vapor management system with proportioned flow splitting

Info

Publication number: EP2344413A1
Application number: EP09737299A
Authority: EP
Inventors: Michael F Tschantz
Original assignee: Meadwestvaco Corp
Current assignee: WestRock MWV LLC
Priority date: 2008-10-10
Filing date: 2009-10-08
Publication date: 2011-07-20
Anticipated expiration: 2029-10-08
Also published as: EP2344413B1; CN103754814B; CN102245494A; WO2010042704A1; CN103754814A

Abstract

A fuel vapor management system for recovering fuel vapors displaced from vehicle fuel tanks, or the like, during the filling thereof from a bulk storage tank (102) is disclosed that has excellent emission control and pressure management. A flow splitter (108) is disclosed that utilizes positive pressure and locates downstream of a vacuum pump (111). The flow splitter is used to direct a portion of the gasoline vapors and air returned from the vehicle to an adsorbent canister (115) and the remaining portion to the UST (102), in such a proportion that a selected UST vacuum may be achieved. The flow splitter (108) may be included as a part of the vapor management system that relies upon a rapidly purging canister system and may be regenerated between vehicle refuelings, while minimizing canister volume requirements and stabilizing negative UST pressures. The disclosed system may be installed at the dispenser or centrally located.

Description

IN THE UNITED STATES PATENT AND TRADEMARK OFFICE Acting as International Receiving Office (RO/LJS)

International Patent Application For

FUEL VAPOR AAANAGEMENT SYSTEM WITH PROPORTIONED FLOW SPLITTING

This non-provisional application relies on the filing date of provisional U.S. Application Serial No. 61 /104422 filed on October 10, 2008, having been filed within twelve (12) months thereof, which is incorporated herein by reference, and priority thereto is claimed under 35 USC § 1.19(e).

BACKGROUND OF THE DISCLOSURE [0001 ] When fuel is pumped from a bulk storage tank into the fuel tank of a vehicle or the like, air and vapors inside the vehicle fuel tank are displaced during the filling process. The displaced vapor flow contains VOCs that can lead to ground level ozone formation and human exposure to HAPs if exhausted into the atmosphere. Service station based refueling vapor controls (also known as Stage Il controls) capture these vapors and return them to an underground fuel storage tank (UST).

[0002] Vacuum Assist Stage Il vapor management system is a technology that utilizes a vacuum pump to mechanically draw air and vapors from the vehicle to the UST. The drawn air is metered to provide a fixed ratio, called the air-to- liquid (A/L) ratio, with the volume rate of liquid fuel dispensed to the vehicle. The A/L ratio may be specified by local or national regulations and typically ranges between 0.9 and 1 .2. Under the frequent conditions when the A/L ratio is greater than 1 .0 or when the HC concentration in the returned stream is below the saturation concentration inside the UST, UST pressurization will take place. The quantity of air at equilibrium (or at saturation) in the ullage space of a UST at a given pressure is dependent upon a number of factors, primarily relating to the fuel vapor pressure which is a function of fuel properties and temperature. In some situations, an excess of air may be delivered into the UST that can lead to pressurization. These situations include when: (1 ) the A/L ratio is greater than 1 ; (2) there is a negative fuel Reid Vapor Pressure (RVP) difference between the initial fuel in the vehicle and the LJST; (3) there is a negative temperature difference between the vehicle's fuel tank and the LJST; or (4) there is less than ideal recovery efficiency at the vehicle and in-leakage, as a result of a poor seal between the dispenser nozzle and the vehicle's fill-port. LJST pressurization may lead to fuel vapor venting through the LJST vent and /or through leaks in the LJST system, thus resulting in VOC emissions to the atmosphere and /or to groundwater contamination. Ideally, the LJST pressure should be maintained below atmospheric.

[0003] Vapor processors or pressure management systems are often required to reduce the LJST pressure and to minimize the fuel vapor emitted from the vacuum assist Stage Il vapor management systems at gasoline dispensing facilities (GDFs). Vapor processors utilize technologies that separate air from fuel vapors, pump the purified air to the atmosphere, and return the fuel vapors to the LJST. The vapor processors are typically sized to meet the demand of the vapor management systems such that a slight system vacuum or ambient pressure is maintained in the LJST. Examples of the technologies currently used for vapor processors are membrane separators, carbon switch-bed adsorbers, refrigerated condensers, and flares or catalytic burners.

[0004] U.S. Patent No. 5,305,807 discloses the fuel vapor management system for a LJST using a single activated carbon canister to control LJST pressures between high and low levels. During load mode, a dedicated vacuum pump pulls a mixture of air and fuel vapor from the ullage space of the LJST (based either on pressure triggers or a timer) and delivers the mixture to the activated carbon canister. The fuel vapors are adsorbed onto the activated carbon in the canister, and fresh air is vented from the system to result in a temporary slight negative pressure of !4" w.c. to 1 " w.c. During purge mode, a series of solenoid valves permits the same vacuum pump to reduce the pressure in the carbon canister to nearly full vacuum (i.e., zero atmosphere). As a result, the adsorbed fuel vapors are desorbed from the activated carbon and discharged back into the ullage of the LJST. Preferably, air is prevented from entering the canister through its vent by means of a check valve. During this period of time, the LJST pressure may rise as a result of continuing refueling vapor management operations. The system is intended to operate for about 15 minutes out of every 2 hours. Single carbon bed systems traditionally operate based on pressure limit triggers, wherein the overall maximum system pressure may be maintained below some threshold, but the LJST pressure can fluctuate over a wide range below the maximum. One drawback of this system is that a full vacuum is necessary to effectively purge the activated carbon canister. If a significant volume of fresh purge air is utilized during canister regeneration, the LJST pressure will increase rapidly. Another drawback is that the LJST pressure can fluctuate over a wide range including positive pressures. The issue of leveling out pressure fluctuations has been addressed by using systems incorporating switch-bed adsorbers.

[0005] The fuel vapor management systems using activated carbon switch- bed adsorbers are usually designed in a similar fashion to those used for fuel vapor management systems of tank loadings at tank farms. These switch-bed systems utilize two carbon beds that operate out of phase in load mode and purge mode. In load mode, by utilizing a network of valves, the vapors in the LJST are vented to one activated carbon bed in the switch-bed system. The fuel vapors therein are adsorbed onto the activated carbon, allowing air to vent from the adsorber to the atmosphere while maintaining atmospheric pressure in the system. Furthermore, a vacuum pump may be used to pump air and vapor from the LJST to one adsorber in the load mode and permit the LJST to develop a negative pressure relative to the ambient. In purge mode, a vacuum pump pulls a nearly full vacuum on the carbon canister to desorb hydrocarbons and return them to the LJST. A small amount of air may be allowed to enter the purging canister to provide improved regeneration, but the vacuum level remains nearly full. So long as the volume of air used during purge is less than the volume of air being vented to the out-of- phase loading canister, a negative LJST pressure may be maintained. The drawback of this system is that each carbon canister must be sized to accommodate the total excess vapor and air mixture of the GDF resulting from both excess air pumped into the LJST and the re-establishment of equilibrium in the LJST. As a result, this system demands a substantially large carbon canister, and consequently a high capacity vacuum pump. Furthermore, a large canister commonly results in thermal and channeling problems that causes poor efficiency and further adds to the size of the canister and the regeneration vacuum pump.

[0006] U.S. Patent No. 3,874,427 discloses the fuel vapor management system that addresses the requirement of a substantially large carbon bed, but the carbon bed is not regenerated and must be replaced at a frequency dependent upon the capacity of the canister to adsorb hydrocarbons. In this system, a vacuum pump is placed in a vapor return line downstream of the vehicle fuel tank and an adsorbent canister which prevents the fuel vapors from reaching the atmosphere. The vapors are pulled from the vehicle by vacuum and subjected alternately to an adsorbent canister or to the bulk fuel storage tank. The vacuum pump is run at a rate substantially equal to the rate at which fuel is being dispensed or proportioned by the A/L ratio so that the entire returned vapors are pulled by the pump and subjected through the adsorptive material during the load mode until the LJST reaches a target negative pressure. The system utilizes a plenum to increase the volume of the vapor return piping at a point, or points, external to the underground bulk storage tank, a timer and/or a solenoid, magnetic, flow, pressure, mechanical or other activated valves.

[0007] There is a still need for a vapor management system that demands a significantly smaller size of adsorbent canister(s) and that does not require full vacuum yet entails a shorter regeneration time to regenerate the fuel loaded- adsorbents. Furthermore, it is desirable to have a system that can maintain a stable negative LJST pressure.

SUMMARY OF THE DISCLOSURE

[0008] A fuel vapor management system for recovering fuel vapors displaced from vehicle fuel tanks, or the like, during the filling thereof from a bulk storage tank is disclosed that has excellent emission control and pressure management. A flow splitter is disclosed that utilizes positive pressure and locates downstream of a vacuum pump. The flow splitter is used to direct a portion of the gasoline vapors and air returned from the vehicle to an adsorbent canister and the remaining portion to the LJST, in such a proportion that a selected LJST vacuum may be achieved. The flow splitter may be included as a part of the vapor management system that relies upon a rapidly purging canister system and may be regenerated between vehicle refuelings, while minimizing canister volume requirements and stabilizing negative LJST pressures. The disclosed system may be installed at the dispenser or centrally located.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic view of one embodiment of the disclosed vapor management system for a central vacuum Stage Il vapor management system, wherein the fuel capturing component includes an adsorbent material;

[0010] FIG. 2 is a schematic view of one embodiment of the disclosed vapor management system for a central vacuum Stage Il vapor management system, wherein the fuel capturing component includes a member separator; [0011 ] FIG. 3 shows the different locations of the vacuum pump in the disclosed vacuum assist Stage Il vapor management system: each vacuum for the fuel dispenser unit(Figure 3A) and a central vacuum Stage Il vapor management system (Figure 3B);

[0012] FIG.4 is a schematic view of one embodiment of the disclosed vapor management system, showing a flow splitter device positioning downstream from the Stage Il vacuum pump to proportionally direct the returned vapor to the LJST and the vapor capturing component;

[0013] FIG. 5 is a schematic view showing various embodiments of the present disclosure to split the flow on the conduit connection around the flow splitter and to isolate the vapor capturing device during regeneration of FIG. 4: Figures 5(A), 5(B), 5(C), and 5(D);

[0014] FIG. 6 is a schematic view showing one embodiments of the present disclosure on the conduit connection around the flow splitter of FIG. 4;

[0015] FIG. 7 is a schematic view showing one embodiments of the present disclosure on the conduit connection around the flow splitter of FIG. 4; and

[0016] FIG. 8 is a schematic view showing one embodiments of the present disclosure on the conduit connection around the flow splitter of FIG. 4. DESCRIPTION OF THE DISCLOSURE

[0017] The present disclosures now will be described more fully hereinafter, but not all embodiments of the disclosure are necessarily shown. While the disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof.

[0018] A fuel vapor management system of one embodiment of the present disclosure comprises:

(a) a bulk fuel storage tank; (b) a vent conduit for the fuel storage tank;

(c) a refueling nozzle;

(d) a fuel delivery conduit communicating at one end with liquid fuel in the bulk storage tank and communicating at an other end with the refueling nozzle; (e) a vapor return conduit communicating at one end with the refueling nozzle;

(f) a pump in the vapor return conduit;

(g) a flow splitter mounted on an opposite end of the vapor return conduit adapted to divide the vapor return conduit into a first branch and a second branch, wherein the second branch connects the flow splitter with an ullage portion of the bulk fuel storage tank; (h) a vapor capturing component capable of capturing fuel in the returned vapor, communicating with the first branch of the flow splitter during a load mode;

(i) a purge conduit communicating at one end with the vapor capturing component during a purge mode and communicating at an other end with the second branch or the ullage, optionally the purge conduit includes a vacuum pump; and (j) a vent conduit for the vapor capturing component.

[0019] The disclosed fuel vapor management system is suitable for use as a

Vacuum Assist Stage Il vapor management system utilizing a vacuum pump to mechanically draw air and vapors from the vehicle to the LJST.

[0020] FIG. 1 shows one embodiment of the disclosed fuel vapor management system. A dispenser of conventional fuel pumps 101 is mounted above an underground fuel storage tank 102 that has a vent conduit 103 to release pressure inside the LJST. When desired, the vent conduit 103 may include a pressure/vacuum valve 104 to control the venting process. One end of a fuel delivery line 105 communicates with the submersible pump 106 in the LJST 102, while the other end communicates the discharge of dispenser 101 and subsequently a refueling nozzle 106. One end of a vapor return line 107 is connected to the refueling nozzle106, and at the other end is connected to a flow splitter 108 where it is divided into a first branch 109 and a second branch 110. The vapor return line 107 has a vacuum pump 11 1 to pull the returned vapor to the flow splitter 108. The first branch 109 connects the flow splitter 108 with an ullage portion of the LJST 102. The second branch 1 10 is connected at one end to a three- way means 112 and at the other end to the flow splitter 108. Although three-way means 112 is shown in FIG.1 , it is to be understood that other means may be used without departure from the spirit of the present disclosure. The three-way valve means 112 is adapted to divide the vapor conduit 1 13 alternative into a loading conduit 110 and a purge conduit 1 14. The loading Conduit 1 10 communicates to a vapor capturing component 115 capable of capturing fuel in the returned vapor. The vent conduit 1 16 has one end connecting to the vapor capturing component 1 15 and at the other end opening to an atmosphere. The vent conduit 1 16 may include a pressure valve 117 to regulate positive pressures during load and vacuum during purge. The purge conduit 1 14 may connect to the second branch 109 or directly to the ullage space of the LJST 102. When desired, the purge conduit 1 14 may have a vacuum pump to produce a vacuum in vapor capturing component 1 15 and to pull the vapors in the conduit to the ullage area of the LJST 102. Pressure valve 117 may also be two separate lines and valves to regulate purge air flow during purge and a low pressure drop during load.

[0021 ] In the load mode, fuel in the LJST 102 is delivered to the automobile fuel tank through the conduit 105, the discharge of station pump 101 , and ultimately the refueling nozzle 106. A mixture of air and fuel vapor in the automobile fuel tank that is displaced during the fueling process plus additional air from outside the automobile is pulled into the conduit 107 by the pump 1 11. A positive pressure is developed between pump 1 11 and flow splitter 108. The returned vapor flow in the conduit 107 is divided by the flow splitter 108 to the first branch 109 and the second branch 110.

[0022] The returned vapor in the first branch 109 is delivered to the ullage space of the LJST 102. The pressure level inside the LJST is controlled such that a negative pressure is maintained throughout the load mode. The returned vapor in the second branch 110 is subjected to the three-way valve means 112 that is opened to the conduit 113 such that the returned vapor in the second branch 1 10 enters into the vapor capturing component 1 15. The fuel vapor in the returned vapor flow is adsorbed by the adsorbents inside the vapor capturing component 1 15, allowing air in the returned vapor to vent into the atmosphere through a positive pressure valve 1 17 in the vent conduit 116 at a predetermined setpoint.

[0023] During the purge mode, no fuel is discharged from the LJST to the automobile fuel tank at the relevant dispenser. The three-way valve means 112 is opened between the conduits 1 13 and 1 14. When desired, at least one of these conduits may include a vacuum pump to reduce the pressure in vapor capturing component 1 15. The fresh air is also drawn into the vapor capturing component 1 15, wherein the adsorbed fuel vapors are desorbed from the adsorbents. In the disclosed system wherein the purge conduit 1 14 connects directly to ullage space of the LJST 102, the desorbed fuel vapor exits the vapor capturing component 1 15 and flows through the conduit 1 13, the three-way valve means 112, the conduit 1 14 to ultimately the ullage space in the LJST 102. In the disclosed system wherein the purge conduit 114 connects to the second branch 109, the desorbed fuel vapor exits the vapor capturing component 1 15, flows through the conduit 1 13 and the three-way valve means 1 12, and then merges with the returned vapor in the first branch 109 through the conduit 1 14. When desired, a vacuum pump may be used to purge the vapor capturing component 115.

[0024] Any known three-way valve means may be used in the present disclosure. Examples of such three-way valve means include, but are not limited to solenoid valves, mechanical valves, and a like. Additionally, multiple lines with a single valve may be used in the system of the present disclosure.

[0025] The vapor capturing component suitable for use in the present disclosure may include a vapor adsorbent element and a container containing the vapor adsorbent element. In one embodiment wherein more than one container of adsorbent is used, the containers are arranged in parallel with each other. When desired, a single flow splitter may be used, and the actuation of the three-way valve means 1 12 may be triggered based upon the number of dispensers in use.

[0026] Any known regenerable adsorbents for fuel vapors may be used in the present disclosure. Examples of such adsorbents include, but are not limited to, activated carbon, zeolite, activated alumina, carbon black, charcoal, silica gel, molecular sieves derived from natural or synthetic zeolites, and combinations thereof. The adsorbent may be in a variety of forms. These include, but are not limited to, honeycomb, pellet, granular, fiber, powder, sheet, and combinations thereof. Activated carbon adsorbent may be derived from a variety of materials. These include, but are not limited to, wood, wood dust, wood flour, cotton linters, peat, coal, coconut, lignite, carbohydrates, petroleum pitch, petroleum coke, coal tar pitch, fruit pits, fruit stones, nut shells, nut pits, sawdust, palm, vegetables, rice hull, straw, synthetic polymer, natural polymer, lignocellulosic material, and combinations thereof.

[0027] In one embodiment of the present disclosure, the vapor capturing component includes one or more canisters of activated carbon adsorbent. [0028] In one embodiment of the present disclosure, the adsorbent element includes activated carbon honeycomb.

[0029] FIG. 2 shows one embodiment of the disclosed fuel vapor management system. An island of conventional fuel pumps 201 is mounted above an underground fuel storage tank 202 that has a vent conduit 203 to release pressure inside the LJST. When desired, the vent conduit 203 may include a pressure valve 204 to control the venting process. One end of a fuel delivery line 205 communicates with the submersible pump 206 in the LJST 202, while the other end communicates the discharge of pump 201 and subsequently a refueling nozzle 206. One end of a vapor returned line 207 is connected to the refueling nozzle 206, and at the other end is connected to a flow splitter 208 where it is divided into a first branch 209 and a second branch 210. The vapor returned line 207 has a vacuum pump 211 to pull the returned vapor to the flow splitter 208. The first branch 209 connects the flow splitter 208 with an ullage portion of the LJST 202. The second branch 210 is connected to a fuel vapor capturing component 212 capable of capturing fuel in the returned vapor. The vent conduit 213 has one end connecting to the fuel vapor capturing component 212 and at the other end opening to an atmosphere. When desired, the vent conduit 1 16 may include a pressure valve 214. The recycle conduit 215 connects the vapor capturing component 212 to the ullage space of the LJST 102. When desired, the recycled conduit 215 may have a vacuum pump to pull the vapors in the conduit to the ullage area of the LJST 102.

[0030] During fueling of a vehicle, fuel in the LJST 202 is delivered to the vehicle fuel tank through the conduit 205, the discharge of station pump 201 , and ultimately the refueling nozzle 206. A mixture of air and fuel vapor in the automobile fuel tank that is displaced during the fueling process is pulled into the conduit 207 by the pump 21 1 . The stream of returned vapor in the conduit 207 is divided by the flow splitter 208 to the first branch 209 and the second branch 210. The returned vapor in the first branch 209 is delivered to the ullage space of the LJST 102. The pressure level inside the LJST is controlled such that a negative pressure is maintained throughout the load mode. The excess pressure may be released to the atmosphere through the vent conduit 203. The returned vapor in the second branch 210 is subjected into the fuel vapor capturing component 212, wherein the fuel vapor and air in the returned vapor stream are separated from the air. The separated fuel vapors exists the vapor capturing component 212 through the conduit 215, while air exists the vapor capturing component 212 through the positive pressure valve 214 in the vent conduit 213 to the atmosphere at a predetermined setpoint.

[0031 ] It is to be understood that FIGs 1 and 2 represent only some embodiments of the vapor management systems of the present disclosure. One skilled in the arts may modify the setup of the system yet may still within the scope of present disclosure. Examples of such setup modifications include, but are not limited to, the following: the vapor capturing component may be dedicated directly to each fuel dispenser unit; or several vapor capturing components may be manifolded together so that there is one vapor capturing component for each fuel dispenser but not necessarily dedicated to a specific dispenser. FIG.3 illustrates examples of these modifications for the location of the vacuum pump in the vacuum assist Stage Il vapor management system. In FIG.3A, one vacuum pump 211 is dedicated to each fuel dispenser unit 201 . In FIG.3B, several fuel dispenser units 201 share a central vacuum pump 21 1.

[0032] Any known vapor capturing components suitable for the separation of fuel vapor from air may be used in the disclosed system shown in FIG. 2. In one embodiment, the vapor capturing component may contain a membrane separator having a selective semipermeable barrier that allows only air in the returned vapor flow to pass through, and not the fuel vapor.

[0033] The present application discloses a method of controlling pressure for the Vacuum Assist Stage Il vapor management system, while enhancing the efficiency of emission control. As shown in FIG.4, the flow splitter 408 positioning downstream to a Stage Il vacuum pump provides a means to split the flow of gasoline vapors and air returned from a Stage Il vapor nozzles 406 and proportionally direct it to the LJST 402 and to a vapor capturing system 415. Various conduit connections around the flow splitter may be used for the present disclosure.

[0034] FIG.5 shows four examples of such conduit connections around the flow splitter, wherein 502 is a LJST, 51 1 is a stage Il vacuum pump, 515 is a vapor capturing system, 508 is a flow splitter, and 530 is a manual or automatic control valve. In FIG. 5(A), the control valve 530 is positioned between the flow splitter 508 and the LJST 502. In FIG. 5(B), the control valve 530 is positioned between the flow splitter 508 and the vapor capturing system 515. In FIG. 5(C), one control valve 530 is positioned between the flow splitter 508 and the LJST 502, and the other control valve 530 is positioned between the flow splitter 508 and the vapor capturing system 515. In FIG. 5(D), a manual or automatic control valve, or a three-way valve, or a flow splitter 540 is positioned at the intersection of the LJST 502, the flow splitter 508 and the vapor capturing system 515.

[0035] FIG.6 shows another embodiment of such conduit connections around the flow splitter, wherein 601 is a fuel dispensing unit, 602 is a LJST, 61 1 is a stage Il vacuum pump, 608 is a flow splitter, 615 is a vapor capturing system, 630 is a manual or automatic control valve, 650 is a vent to atmosphere or to filter, and 660 is an orifice or restriction.

[0036] FIG. 7 shows another embodiment of such conduit connections around the flow splitter, wherein 701 is a fuel dispensing unit, 702 is a LJST, 71 1 is a stage Il vacuum pump, 708 is a flow splitter, 715 is a vapor capturing system, 730 is a manual or automatic control valve, 750 is a vent to atmosphere or to filter, and 760 is an orifice or restriction.

[0037] FIG.8 shows another embodiment of such conduit connections around the flow splitter, wherein 801 is a fuel dispensing unit, 802 is a LJST, 81 1 is a stage Il vacuum pump, 808 is a flow splitter, 815 is a vapor capturing system, 830 is a manual or automatic control valve, 850 is a vent to atmosphere or to filter, and 860 is an orifice or restriction. [0038] One skilled in the art would appreciate that other configurations of conduit connections around the flow splitters may be used without departure from the concept of the present disclosure.

[0039] Several techniques may be used for the disclosed flow splitter. The flow splitter itself may be as simple as a pipe tee with the restriction of one or both of the tee outlets being controlled to divert a proportion of flow of the vapors to the vapor capturing device. In one embodiment, the flow splitter may be a pressure control valve wherein the feedback from the LJST pressure acts to maintain the LJST pressure to some predetermined setpoint. In one embodiment, the flow splitter may be a fixed splitter wherein the level of flow splitting may be adjusted and calibrated to meet selected performance. Any known flow splitter techniques may be used in the present disclosure. These include, but are not limited to, the following: using a control valve with pressure feedback from the LJST; setting the ratio of flow using orifices or pipe diameters; using an adjustable valve or orifice; a non-adjustable valve or orifice; or T-connector.

[0040] In the vapor management system of U.S. Patent No. 5,305,807, the returned fuel vapor from the vehicle is sent back to the LJST and then drawn from the LJST to the activated carbon canister. Contrary, in the vapor management system of present disclosure, the return fuel vapor is pumped from the vehicle directly to the vapor capturing component. As a result, in the disclosed vapor management system the vapors are treated and concentrated before reaching the UST.

[0041 ] Unlike the vapor management system in the U.S. Patent No. 3,874,427, the pressure inside the UST of the disclosed system may be maintained at a relatively constant pressure by diverting a portion of the returned vapor stream to the vapor capturing device and the remaining portion to the ullage space of the UST. The disclosed system diverts the returned vapor stream into two portions such that only a portion of the returned vapor is subjected to the vapor capturing device. As a result, the adsorbent required for the disclosed system is regenerable and may be substantially smaller than that required for the known vapor management system, particularly the system of U.S. Patent No. 3,874,427.

[0042] The disclosed vapor management system has excellent fuel emission control and pressure management. In the system of U.S. Patent No. 3,874,427, when the activated carbon in canister becomes saturated and no longer effective in adsorbing fuel vapors, it is essential to remove the fuel-loaded canister from the system and replaced with an identical canister containing fresh or regenerated activated carbon. The manual replacement process of each fuel-loaded carbon canister is burdensome, labor demanding, and maintenance intensive. In the contrary, the fuel-loaded adsorbent element in the vapor capturing device of the disclosed system may be regenerated in-line during purge mode. Accordingly, the disclosed system significantly reduces the labor cost and cost of replacement parts, which is typically required for replacing the fuel-loaded carbon canister as in the system of U.S. Patent No. 3,874,427.

[0043] Moreover, the fuel-loaded adsorbent element in the vapor capturing component of the disclosed system may be effectively regenerated in a remarkably shorter time period and at substantially higher pressure than those of known vapor management systems. In one embodiment of the present disclosure, the fuel- loaded adsorbent element may be regenerated in less than 3 minutes at a pressure of more than 0.2 atmospheres absolute pressure. In one embodiment of the present disclosure, the fuel-loaded adsorbent element may be regenerated in less than 2 minutes at the pressure of more than 0.3 atmospheres absolute pressure. The vapor management system of known arts typical requires full vacuum (i.e., zero pressure) or nearly full vacuum in order to permit regeneration of the fuel- loaded adsorbent in the vapor capturing component.

[0044] In the disclosed system, a moderate purge vacuum level may provide a driving force for desorption of hydrocarbons from the adsorbent in combination with a moderate air purge flow. An alternative means to promote desorption rather than using vacuum may be to draw air through the vapor capturing device (i.e, purging). For example, if a vapor capturing element, such as carbon bed, has a fixed working capacity with 100 bed volumes of air at 1 atm pressure, then only 25 bed volumes of air would be required to achieve the same fixed working capacity at 250 mbar pressure and the vapor concentration would be increased significantly. The amount of air available for purge is based displacing hydrocarbons desorbing from the adsorbent material to maintain a driving force for continued desorption. For example, if hydrocarbons at 25% vapor concentration are loaded onto the adsorbent, the hydrocarbons could be concentrated to >50% during purge at 250 mbar operating pressure.

[00451 Example 1: If 9 psi RVP fuel at 70⁰ F is delivered from a LJST at 10 gallons per minute to refuel a vehicle initially containing 9 psi RVP fuel at 60⁰F, air and gasoline vapors will be displaced from the vehicle at a rate of approximately 10.6 gallons per minute. If the vapor management system was operating with a recovery efficiency of 80% and with an A/L ratio of 1.1 , the system would be pulling vapors at 1 1 gallons per minute at a concentration of 26.6% hydrocarbons. The returned vapor stream would be split such that 3.4 gallons per minute were delivered to the vapor capturing device and 7.6 gallons per minute were returned to the LJST. Approximately 1 .1 liters of carbon honeycomb would be required to adsorb the 19 grams of hydrocarbons delivered to it over two minutes of time. The canister would be purged at 250 mbar operating pressure with a flow rate of 0.9 gallons per minute of purge air in less than one minute after refueling was completed. Under these operating conditions, a gauge pressure of -6 inches water column could be maintained in the LJST.

[0046] Example 2: If 7 psi RVP fuel at 70° F is delivered from a LJST at 60 gallons per minute to refuel six vehicles at three dispenser units simultaneously, each vehicle initially containing 9 psi RVP fuel at 80⁰F, air and gasoline vapors will be displaced from the all the vehicles at a rate of approximately 56.5 gallons per minute. If the vapor management system was operating with a recovery efficiency of 100% and with an A/L ratio of 1 .2, the vapor management system would be pulling air and vapors at 72 gallons per minute at a concentration of 20.6%. If the vapor management system were operated utilizing a single flow splitter on a vapor return manifold, the returned vapor stream would be split such that 23.6 gallons per minute were delivered to six vapor capturing devices (3.9 gallons per minute to each) and 48.4 gallons per minute were returned to the LJST. Approximately 1 .4 liters of carbon honeycomb would be required to adsorb 22.7 grams of hydrocarbons delivered to each adsorber over two minutes of time. Each canister would be purged at 250 mbar operating pressure with a flow rate of 0.9 gallons per minute of purge air in less than one minute after refueling was completed. Under these conditions, a gauge pressure of -6 inches water column could be maintained in the UST.

[0047] The reason to have canisters containing adsorbent sized for each filling location (based upon some average or high average total volume delivered) is based on the fact that not every filling location will be dispensing fuel all the time. The break between vehicle fuelings allows time for the system to purge. For very busy locations, there may not be a lot of time between refueling events per dispenser (perhaps as low as one minute). Therefore, there is a need to be able to very quickly purge the system. The use of moderate vacuum and air purge can permit this, but only if there is little mass transfer resistance in the bed. The need to very quickly purge the canister requires that the canister be as small as possible and with an adsorbent that can purge very quickly. In one embodiment of the present disclosure, an adsorbent having very small particles and little thickness of medium may be used. One example of such adsorbent is an adsorbent having honeycomb structure. Since there can be a canister dedicated to each filling location, the canisters may be placed in the dispenser, in their island, or centrally located. If the canisters are centrally located, a common regeneration vacuum pump and flow splitter can easily be used. A single PCV may be used, and the canisters may be non-specific to a filling location (and open up on a first-come first-serve or as-needed basis). A centralized location could allow large vehicles to utilize additional, available canisters as the capacities of those used are reached.

[0048] The vapor management systems of the present disclosure offer many advantages compared to those of known arts. Some of these advantages include, but are not limited to, (1 ) only a moderate vacuum is required to regenerate the vapor capture element, thereby allowing a greater flexibility in vacuum pump selection and reducing cost and maintenance; (2) the system is modular; therefore, it may be easily expanded or contracted based on modifications to the gasoline dispensing facility (GDF) or changes in average throughput; (3) the system offers redundancy, such that the GDF can continue to operate (at least to some extent) even if part of the vapor management system goes down; (4) the LJST system can be operated at a relatively controlled and stable pressure by utilizing the vapor return flow splitter and/or the pressure control system to provide feedback from the LJST to the flow splitter; (5) the need to ensure vapor tightness of the site is greatly reduced because the LJST system may be regularly operated at a negative or ambient pressure; (6) the necessary adsorption capacity of the total system may be half that required by switch-bed technology; (7) the modular nature of the disclosed system may permit it to be centrally located or dispersed throughout the dispensers or refueling islands.

[0049] While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. It is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Claims

We Claim:

1 . A method of controlling volume of a fluid flow returned to an underground storage tank from a refueling nozzle in a fuel vapor management system, including a step of: using a flow splitter to direct a first portion of the returned fluid flow into the underground storage tank and a second portion of the returned fluid flow into a vapor capturing component, the flow splitter positioning downstream from a vacuum pump.

2. The method of Claim 1 , wherein the vapor capturing component includes:

(a) a vapor adsorbent element comprising a member selected from the groups consisting of activated carbon, zeolite, activated alumina, carbon black, charcoal, silica gel, membrane, molecular sieves, and combinations thereof; and

(b) a container containing the vapor adsorbent element.

3. The method of Claim 2, wherein a shape of the vapor adsorbent element includes a member selected from the groups consisting of honeycomb, pellet, granular, fiber, powder, sheet, and combinations thereof.

4. The method of Claim 2, wherein a source of the activated carbon includes a material selected from the group consisting of wood, wood dust, wood flour, cotton linters, peat, coal, coconut, lignite, carbohydrates, petroleum pitch, petroleum coke, coal tar pitch, fruit pits, fruit stones, nut shells, nut pits, sawdust, palm, vegetables, rice hull, straw, synthetic polymer, natural polymer, lignocellulosic material, and combinations thereof.

5. A fuel vapor management system for a fluid flow returned to an underground storage tank from a refueling nozzle, including:

(a) a flow splitter capable of diverting a portion of the returned fluid flow to a vapor capturing component and a remaining portion to the underground storage tank; and (b) a vacuum pump upstream of the flow splitter to force the returned fluid flow through the flow splitter.

6. The system of Claim 5, further comprising: (c) a valve to control an amount of the diverted fluid flow to the vapor capturing component, the amount being in a range of about 0% to about 99% of the total returned fluid flow.

7. The system of Claim 5, wherein the flow splitter is capable of diverting at least 1% of the displace vapor flow to the vapor capturing component.

8. The system of Claim 5, wherein a pressure inside the bulk fuel storage tank is maintained below one inch water column positive pressure.

9. The system of Claim 5, wherein a pressure inside the bulk fuel storage tank is maintained below atmospheric pressure.

10. The system of Claim 5, wherein the flow splitter includes an adjustable valve.

1 1. The system of Claim 5, wherein the adjustable valve is automatically controlled to maintain a pressure in the fuel storage tank at a setpoint range of about -20 inches water column and 6 inches water column

12. The system of Claim 5, wherein the vapor capturing component includes: (a) a vapor adsorbent element comprising a member selected from the groups consisting of activated carbon, zeolite, activated alumina, carbon black, charcoal, silica gel, molecular sieves derived from natural or synthetic zeolites, and combinations thereof; and (b) a container containing the vapor adsorbent element.

13. The system of Claim 12, wherein a shape of the vapor adsorbent element includes a member selected from the groups consisting of honeycomb, pellet, granular, fiber, powder, sheet, and combinations thereof.

14. The system of Claim 12, wherein a source of the activated carbon includes a material selected from the group consisting of wood, wood dust, wood flour, cotton linters, peat, coal, coconut, lignite, carbohydrates, petroleum pitch, petroleum coke, coal tar pitch, fruit pits, fruit stones, nut shells, nut pits, sawdust, palm, vegetables, rice hull, straw, synthetic polymer, natural polymer, lignocellulosic material, and combinations thereof.

15. The system of Claim 12, wherein the vapor adsorbent element includes an activated carbon honeycomb.

16. The system of Claim 12, wherein the vapor capturing component further includes a refrigerated condenser.

17. The system of Claim 12, wherein the vapor capturing component further includes a membrane separator.

18. A fuel vapor management system, comprising:

(a) a bulk fuel storage tank; (b) a vent conduit for the fuel storage tank;

(c) a refueling nozzle;

(d) a vapor return conduit communicating at one end with the refueling nozzle;

(e) a pump in the vapor return conduit; (f) a flow splitter mounted on an opposite end of the vapor return conduit adapted to divide the vapor return conduit into a first branch and a second branch, wherein the second branch connects the flow splitter with an ullage portion of the bulk fuel storage tank; (g) a vapor capturing component capable of capturing fuel in the returned vapor, communicating with the first branch during a load mode; and (h) a vent conduit for the vapor capturing component.

19. The system of Claim 18, further comprising a vacuum pump for purging the vapor capturing component.

20. The system of Claim 18, further comprising a means of heating the vapor capturing component above 80⁰C during regeneration.

21. The system of Claim 18, further comprising a pressure control valve mounted on the vent conduit for the vapor capturing component.

22. The system of Claim 18, wherein the flow splitter includes an adjustable valve.

23. The system of Claim 22, wherein the adjustable valve is automatically controlled to maintain a pressure setpoint of the fuel storage tank.

24. The system of Claim 18, wherein the vapor capturing component includes:

(a) a vapor adsorbent element comprising a member selected from the groups consisting of activated carbon, zeolite, activated alumina, carbon black, charcoal, silica gel, molecular sieves derived from natural or synthetic zeolites, and combinations thereof; and

(b) a container containing the vapor adsorbent element.

25. The system of Claim 24, wherein a shape of the vapor adsorbent element includes a member selected from the groups consisting of honeycomb, pellet, granular, fiber, powder, sheet, and combinations thereof.

26. The system of Claim 24, wherein a source of the activated carbon includes a material selected from the group consisting of wood, wood dust, wood flour, cotton linters, peat, coal, coconut, lignite, carbohydrates, petroleum pitch, petroleum coke, coal tar pitch, fruit pits, fruit stones, nut shells, nut pits, sawdust, palm, vegetables, rice hull, straw, synthetic polymer, natural polymer, lignocellulosic material, and combinations thereof.

27. A fuel vapor management system for vapor in a vehicle fuel tank being displaced with fuel from a bulk fuel storage tank during fueling of vehicles, including a vapor capturing component capable of adsorbing fuel vapor in the displaced vapor flow, wherein: (i) the vapor capturing component comprises a vapor adsorbent element selected from the groups consisting of activated carbon, zeolite, activated alumina, carbon black, charcoal, silica gel, molecular sieves derived from natural or synthetic zeolites, and combinations thereof; and (ii) the vapor adsorbent element loaded with the fuel vapor is regenerated to a working capacity of more than 10 g/L for the fuel vapor in equilibrium with 9 psi RVP fuel, in less than 3 minutes at a pressure of more than 0.1 atmospheres absolute pressure.

28. The system of Claim 27, wherein a shape of the vapor adsorbent element includes a member selected from the groups consisting of honeycomb, pellet, granular, fiber, powder, sheet, and combinations thereof.

29. The system of Claim 27, wherein a source of the activated carbon includes a material selected from the group consisting of wood, wood dust, wood flour, cotton linters, peat, coal, coconut, lignite, carbohydrates, petroleum pitch, petroleum coke, coal tar pitch, fruit pits, fruit stones, nut shells, nut pits, sawdust, palm, vegetables, rice hull, straw, synthetic polymer, natural polymer, lignocellulosic material, and combinations thereof.