Abstract:
A gasoline vapor treating system includes a single hydrocarbon filter apparatus interconnected to a fuel tank having a range of vapor pressures therein, said filter apparatus receiving hydrocarbon vapors from said tank for one vapor pressure in said fuel tank and said filter apparatus delivering air and hydrocarbon vapor to said tank from said filter responsive to another vapor pressure in said tank lower than said one vapor pressure, said filter operated serially between hydrocarbon loading and hydrocarbon unloading cycles without reference to any other hydrocarbon removal apparatus. A balance nozzle includes a mechanism to mechanically operate a vapor valve therein before the fuel valve is opened.

Description:
PRIORITY CLAIM 
     Applicant claims the benefit of the filing date of May 10, 2006 of U.S. provisional patent application Ser. No. 60/746,933. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to reduction of hydrocarbon vapor emissions attendant fueling of vehicles with hydrocarbon fuel and more particularly to methods and apparatus for filtering hydrocarbon vapor from fueling system emissions and retaining hydrocarbon vapor within a fueling system. 
     BACKGROUND OF THE INVENTION 
     It has been increasingly important to reduce or eliminate emission of hydrocarbon vapors attendant the fueling of vehicles with hydrocarbon fuels, such as liquid gasoline. Certain jurisdictions such as California regulate hydrocarbon emissions to ever decreasing minimums In order to meet various even more restrictive standards, various methods and devices have been proposed. One such prior system includes the use of a vapor recover nozzle such as an assist nozzle associated with a dispenser, an underground storage tank (UST) and a vacuum pump for pumping captured vapors back to the UST. Another system includes the use of a vapor recover nozzle such as a “balance” nozzle associated with a dispenser and a UST where captured vapors passively flow back to the UST. A yet further system includes a vapor recovery nozzle, a dispenser and/or UST, together with dual hydrocarbon filtering canisters operating in a parallel process mode. One canister operates to filter out hydrocarbon vapor emissions from the UST while the other canister is subjected to a reverse air flow to clean or “unload” captured hydrocarbon fractions in it, previously filtered out of a stream of air and vapor discharging from the UST. The canister functions are reversed or cycled as desired for alternate filtering and cleaning, opposite to each other. 
     It is desired to provide less costly, less complex emissions reducing or eliminating apparatus and methods without the use of vacuum assist at either the fuel nozzle or at any hydrocarbon filter. 
     Accordingly, it is one objective of the invention to provide improved methods and apparatus for capturing and retaining hydrocarbon emissions resulting from a fueling process from an underground storage tank. 
     A further objective of the invention has been to provide an improved hydrocarbon filter apparatus and process for filtering hydrocarbons from vapor within an underground storage tank. 
     A yet further objective of the invention has been to provide passive or balanced apparatus and methods for filtering hydrocarbons from emissions from an underground storage tank of hydrocarbon fuel and for passively cleaning or unloading a hydrocarbon filter without use of any vacuum assist. 
     A further objective of the invention has been to provide apparatus and processes to filter hydrocarbon emissions resulting from a fueling process with less costly and less complex apparatus and processes than in current use. 
     SUMMARY OF THE INVENTION 
     To these ends, the invention, in one embodiment, contemplates an underground storage tank (UST) of fuel operably interconnected to a dispenser and a vapor recovery nozzle of any suitable configuration for dispensing liquid fuel, such as gasoline, from the UST into a fuel consuming vehicle. While fuel is being dispensed, liquid fuel is flowing out of the UST, decreasing vapor pressure above the fuel in the tank. The UST is operably connected to atmosphere through a valved hydrocarbon filtering canister. 
     Operationally, according to the invention, while fuel is being dispensed, the resulting decrease in vapor pressure in the UST to a level below about −2.0 inches water column and less is operable to cause a valve to open to draw atmosphere through the canister and toward the UST to clean or unload hydrocarbon fractions previously adsorbed in the canister. When fuel dispensing ceases, and according to the invention, vapor pressure increases, in the UST to a level above about +0.20 inches water column, the same valve opens and hydrocarbon vapor is transferred through the canister toward its vent, to atmosphere, the hydrocarbon fractions being adsorbed in the canister and removed from the discharging vapor. 
     Only a single canister is required, and the apparatus and methods perform without any vacuum assist. The single filter canister is “loaded” during periods wherein fuel is not being dispensed and is cleaned or unloaded during periods where fuel is being dispensed, the entire system being driven passively primarily as a function of vapor pressure in the UST. Thus, according to the invention, a single canister is operationally cycled in serial fashion and not in parallel or in tandem with any other hydrocarbon filter. 
     Pressure sensors, hydrocarbon sensors and one or more valves on one or more sides of the filter canister are operationally interconnected through a programmable control to accomplish the operational cycle described above, and as will be described in more detail. 
     As compared to known systems, the invention provides for hydrocarbon emission control more cheaply and with less complexity than prior known systems, and without the need for any active vacuum or vapor assist. 
     These and other objectives and advantages of a preferred embodiment of the invention will become readily apparent from the following detailed written description and from the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing illustrating components of the invention and the function and process of certain components thereof; 
         FIG. 2  is a table illustrating the parameters of a fueling operations for mixes of vehicle types; 
         FIG. 3  is a chart showing pressures occurring in a vapor recovery system with no filter; 
         FIG. 4  is a chart similar to  FIG. 3  but showing pressure levels occurring in a system according to the invention; 
         FIG. 5  is a cross-sectional view of components of one form of balance nozzle useful with the system of the invention; 
         FIG. 6  is a cross-sectional view taken along lines  6 - 6  of  FIG. 5  and illustrating a dynamic seal and step stop of the nozzle; and 
         FIG. 7  is a cross-sectional view taken along lines  7 - 7  of  FIG. 5  and showing the secondary shut-off apparatus of the nozzle. 
     
    
    
     DETAILED DESCRIPTION 
     Turning now to the Figures, the invention is schematically illustrated in  FIG. 1  and comprises a system  10  including a fuel or gasoline dispenser  11  (preferably above ground), an underground storage tank  13  for fuel/gasoline and referred to herein as the “UST”  13 , a gas supply line and vapor return line  12 , a vent line, a vapor vent or passage  14 , a pressure relief vent cap  15 , a vapor passage or conduit  16 , a vapor passage or conduit  16 A, a hydrocarbon adsorbing filter canister  17 , a vapor vent line  18  with a pressure relieve or open cap  19  and a control  20 . Also provided as shown are high pressure sensor  25 , low pressure sensor  26 , solenoid operated valve  27 , hydrocarbon sensor  28  and optional flow restrictions  29 ,  30  in lines  16 A,  18 , respectively. 
     It will be noted that filter  17  is a filter of any suitable manufacture for filtering hydrocarbons out of the vapor transferred from UST  13  to filter  17 . Preferably, the filter media, mass and flow characteristics are selected as functions of the volume of anticipated hydrocarbon vapor to be filtered. Such filters are preferably in the form of a canister with couplings, or ends suitable for attachment to lines or conduits  16 A and  18  as illustrated. Media may comprise activated carton or any other suitable form of hydrocarbon adsorptive media. 
     Control  20  comprises a control panel, together with such programmable electronic controls of any type as are well-known in the control industry, functioning according to the invention as will be described. 
     Sensor  25  is pre-set to sense a predetermined higher, pressure in line  16  and is capable of sending a signal through line  33  to control  20  indicating a pressure level in line  16  of about +0.20 inches or higher. Sensor  26  is pre-set to sense a predetermined lower pressure in line  16  and is capable of sending a signal through line  34  to control  20  when pressure in line  16  reaches −2.0 inches of water column or lower. Sensor  25  can be set to indicate pressures of up to +0.50 inches of water column and higher, while sensor  26  can be set to indicate lower pressures of −2.5 inches of water column or lower. Lines  33 ,  34  are control input lines to control  20 . Line  35  is an output line from control  20  to solenoid valve  27 . Solenoid valve  27  is operated to open vapor passage  16 A when the sensor  25  signals control  20  in the presence of a high pressure of about +0.20 inches of water column, preferably, or alternatively, somewhat higher up to +0.50 water column. Solenoid valve  27  is also operated to open when sensor  26  signals a lower pressure of preferably about −2.0 inches of water column in passage  16  or alternatively somewhat lower pressure of about −2.5 inches water column. 
     Accordingly, valve  27  opens line  16 A to pass vapor between UST  13  and filter  17  when vapor pressures in line  16  exceed about +0.20 inches water column or when vapor pressures in line  16  are less than about −2.0 inches water column. For pressures between about +0.20 inches water column and about −2.0 inches water column, valve  27  is closed. Other pre-sets or pressures may be used but these pressures are preferred. 
     It will be appreciated the pressures noted are relative to ambient pressure of about 0.0 inches water column. It will also be appreciated that pressures in vapor passage  16  are approximately equal to vapor pressure in the vapor area  40  above surface  41  of liquid fuel such as gasoline  42  in UST  13 . 
     Several other structural features of system  10  are noted prior to a detailed description of operation. 
     Hydrocarbon sensor  28  is operatively coupled to control  20  via a line  36  input to control  20 . 
     Pressure relief of vent cap  15  on line  16  is set to crack open at about −8.0 inches of water column pressure or about +3.0 inches of water column pressure. In this way, dangerous over pressures or vacuums are relieved and avoided. 
     Pressure or vacuum relief cap  19  over line  18  may be open for passage of gases into or out of passage  18  at any pressure or it too may be set to pass gases in either direction in response to a preset pressure. Preferably, cap  19  is an open rain or weather guard cap. 
     Finally, it will be appreciated that line  12  operably connects dispenser  11  to UST  13  and in any form of suitable conduit capable of transferring liquid gas  42  from UST  13  to dispenser  11  and of transferring vapor from dispenser  11  to UST  13 . Passage  12  may have a gas passage extending to the bottom of UST  13 , and a vapor outlet oriented proximate the upper interior of UST  13 . 
     Dispenser  11  has an outlet hose  22  operably connected to a fuel dispensing nozzle  23 . Nozzle  23  is any suitable fuel dispensing/vapor recovery nozzle capable of transferring fuel to a vehicle, for example, from UST  13  and from capturing vapors attendant such transfer for return to UST  13  through hose  22 , dispenser  11  and conduit  12 . 
     While a “vapor assist”-type nozzle of any well-known manufacture might be adapted with intelligence for use in system  10 , it is preferred to use a “balance”-type nozzle of any suitable manufacture. Examples of “balance”-type nozzles  23  which could be used are as follows: Nozzle Model 11VF available from OPW Fueling Components of 9393 Princeton Glendale Road, Hamilton, Ohio 45011. Nozzle Model V available from Husky Corporation of 2325 Husky Way, Pacific, Mo., 63069; or Nozzle Model A4005 or A4015 available from Emco Wheaton of 2300 Industrial Park Drive, Wilson, N.C., 27893. 
     Moreover, such vapor recovery balance nozzles and components thereof are described in U.S. Pat. Nos. 5,665,576; 5,421,382; 5,121,777 and 4,825,914, all of which are expressly incorporated herein by reference as if fully set forth here. 
     Also, and while the nozzles in the following patents are primarily for use in vapor assisted systems, U.S. Pat. Nos. 6,851,628; 6,951,229 and 7,134,580 showing “assist” type nozzles are also incorporated herein by reference as if fully set forth herein. The balance nozzle further described herein is similar to the assist nozzles in these latter patents, excepting for the lack of an “assist” mechanism, the mechanical vapor valve, the stem seal and stem shoulder, and the secondary shut-off mechanism described herein. 
     In this regard, a preferred “balance”-type nozzle generally comprises a nozzle for dispensing gasoline and for capturing and transferring vapors through a coaxial hose back from the vicinity of a vehicle tank outlet to the dispenser  11  and UST  13 , as a function of vapor pressure and without extraneous vacuum assist. Such nozzles in the past have typically included a vapor valve opened by the action of a sealing boot engaging the gasoline fill tube of a vehicle. 
     This has proven to be quite unreliable in generating a substantially tight vapor seal when the nozzle is not in use. This can occur since a bellows actuated vapor valve can be activated at any time just by having the bellows compressed, by hand, or by misplacement in the dispenser nozzle boot. Without this substantially tight vapor seal during non-dispensing periods, if the storage tank is in vacuum, uncontrolled air is drawn in, encouraging gasoline evaporation and emissions, or if the storage tank is in pressure, without the tight vapor seal, uncontrolled and unmonitored emissions are continuously occurring. In contrast, and as described herein, a balance valve useful with system  10  contains a lever actuated vapor valve which only opens when liquid gasoline is being dispensed. 
     In any event, the balance nozzles which may be useful with this invention typically include a boot for sealing to the vehicle for effective capture of hydrocarbon vapor. 
     Nozzle 
     Accordingly,  FIG. 5  illustrates one form of modified balance nozzle  50  (like nozzle  23 ) which may be useful with system  10 . Nozzle  50  includes a collapsible bellows  51  which has a forward face  52  for sealing with a gasoline filler tube mouth during refueling. Nozzle  50  has an interlock (not part of this invention) which disables the gas valve actuating lever  53  until bellows  51  is collapsed against a vehicle filler tube with spout  54  therein. 
     Nozzle  50  has a vapor valve  56  mounted coaxially with gas valve  57  for movement therewith. However, upon actuation of lever  53 , vapor valve  56  is cracked open prior to opening of gas valve  57 . 
     The mechanical vapor valve  56  starts to open with the main lever  53 , before the liquid valve  57  opens. This action allows the mechanical vapor valve  56  to simulate the operation of a traditional balanced nozzle that has a vapor valve in the spout/bellows area. 
     The “boot-actuated” vapor valve on a traditional balanced nozzle will open when the nozzle is inserted into the fill pipe of the vehicle. However, as stated above, these types of vapor valves are also prone to leakage when they are hung up in the dispenser boot. There is a spring loaded flapper switch located in the dispenser boot that electronically deactivates the dispenser when the nozzle is hung up and any pressure on the bellows by its flapper switch could potentially open the valve and cause a leak in the system. A mechanical valve, such as valve  56  in nozzle  50  herein, is immune to this problem. 
     Mechanical vapor valves have been used in vacuum assist nozzles such as shown in several of the noted patents. Assist nozzle modules are available from OPW Fueling Components of 9393 Princeton Glendale Road, Hamilton, Ohio 45011, however, these vapor valves typically do not open before the liquid valve. 
     Because a vacuum assist nozzle inherently has a much higher pressure drop through the vapor path (primarily due to the hose design), they therefore need a vacuum pump to “assist” the gasoline vapors through the vapor recover system. There is no need for the vapor valve to be open prior to the dispensing fuel, since the vacuum pump will overcome the higher back pressure of a partially closed valve. 
     A balanced system has a much lower pressure drop through the vapor path and does not rely on a vacuum pump to pull the vapors through the system. Instead, the nozzle creates a tight seal on the vehicle fill pipe and when fuel is dispensed into the tank, the vapors are forced through the vapor path of the nozzle and pushed into the hose. If fuel was allowed to be dispensed (at a slow rate) with the vapor valve closed, then the vapor path could become pressurized and simulate a blockage. 
     On the balanced nozzle  50 , there is a secondary shutoff mechanism  70  ( FIG. 7 ) located opposite the primary shutoff mechanism that will not allow the nozzle to operate if a blockage is detected in the vapor path of the nozzle or the balanced hose. A pressurized vapor path can create a dangerous condition by causing fuel to be ejected from the vehicle fill pipe when the nozzle is retracted from the vehicle. The secondary shut off mechanism is not required on assist nozzles. 
     More particularly, the space to the left of a diaphragm  71  ( FIG. 7 ) is connected to the vapor path of the nozzle through a small drilled hole (not shown), between the vapor valve and the inlet (hose end). If a blockage occurs due to liquid in the vapor path of the hose  22  ( FIG. 1 ), pressure will build up in the vapor path of the nozzle  23 ,  50  ( FIG. 1 ) while gasoline is being dispensed (presuming there is a tight seal of bellows face  52  ( FIG. 5 ) on the vehicle fill pipe face). This pressure will act on the diaphragm and displace it to the right, which will make contact with the push link  72  and ultimately push the latching rollers  73 ,  74  out of the notch  75  in the latch stem  76 . This action will close the main valve and not allow the flow of gasoline through the nozzle. 
     The main stem  58  of nozzle  50  travels through the main valve sub-assembly at  59 . A dynamic seal  60  prevents leakage through the main valve section  57  around stem  58 . This dynamic seal  60  is accomplished with an elastomer lip seal or by any other suitable sealing expedient. 
     Finally, a stop ( 61 ) on the main stem controls the pre-travel of the vapor valve in the following manner. 
     In other nozzles, the mail fuel valve is connected directly to the main stem. When the operating lever is depressed, the stem moves upward and immediately opens the main valve. In contrast, in nozzle  50 , when the lever is depressed, the main stem  58  moves upward, but the vapor valve  56  opens first. There is a step  61  on the stem  58  that will only then start to open the main valve  57  after the vapor valve  56  is open slightly. 
     Because the main stem  58  goes through the main valve  57  to open the vapor valve first, seal  60  is used with the main valve  57  itself. The main valve  57  sub-assembly actually floats on the main stem  58  when it is in the closed position. 
     Operation 
     Operation of system  10  generally comprises three basic conditions:
     a. Valve  27  is closed, and no vapor or air is transferred through conduits  16 ,  16 A,  18 ;   b. When the gasoline storage tank (UST  13 ) achieves a pressure slightly above local atmospheric, such as about +0.20 inches water column, this pressure is sensed by the pressure sensor  25  which sends an electrical signal to the control panel, which in turn opens the valve  27  allowing gasoline vapor emissions to enter the canister  17 . Hydrocarbon vapor is adsorbed in filter  17  and the filter is “loaded” with hydrocarbon, thus cleaning hydrocarbon from the vapor emitted through passage  18 .   c. When the gasoline storage tank (UST  13 ) achieves a pressure slightly below local atmospheric, i.e. about −2.0 inches water column, this pressure is sensed by the pressure sensor  26  which sends an electrical signal to the control panel  20  which in turn opens the valve  27 , allowing atmospheric air to enter the canister filter  17  through cap  19  and vent conduit  18 . Air travels through canister  17  in an upstream direction to UST  13 . Hydrocarbon is released by the adsorbent material of filter  17  and joins the air in returning to the gasoline storage tank (UST  13 ).   

     In a yet fourth condition, where positive vapor pressures exceed about +3.0 inches or negative vapor pressures are less than about −8.0 inches, relief valve cap  15  opens to prevent damage, gas spill or other aberrations to UST  13 , or other components of system  10 , even though this may result in a hydrocarbon leak. 
     There are generally two types of vehicles which may be fueled by the invention including system  10 . These are vehicles with Onboard Refueling Vapor Recovery Systems (ORVR) and vehicles without such systems. The table of  FIG. 2  illustrates the comparison of fueling a population of ORVR vehicles from 10% to 100% of both classes of vehicles fueled, and is self-explanatory.  FIG. 2  illustrates a facility dispensing throughput of about 5000 gallons per day (18 hours) at about 278 gallons per hour. The ratio of the volume of vapor and air collected from the vehicles and returned to the UST  13  to the volume of gasoline dispensed from the UST  13  to the vehicle (i.e. V/L) is about 0.10 for ORVR vehicles and about 0.80 for non-ORVR vehicles. 
     The table of  FIG. 2  illustrates the overall performance of system  10  according to the invention within these parameters and illustrates the typical volumes of gasoline and vapors handled in system  10  in a typical dispensing day. 
     During normal customer dispensing, with any population of ORVR vehicles, the volume of air/vapor returned to the gasoline storage tank from the vehicle/nozzle interface is less than the volume of liquid gasoline leaving the storage tank  13 .  FIG. 2  shows the relationship between the vapor collected at the nozzle and the net negative volume in the storage tank in the presence of ORVR vehicle fueling; this net negative volume results in a reduction of storage tank pressure during dispensing into vehicles. 
     Referring now to  FIG. 3 , that FIG. Comprises a chart which illustrates, for comparative purposes, a dispensing history of dispensing events (vehicle fuelings) over a 48 hour period where system  10  of the invention is not used.  FIG. 3  illustrates vapor growth during non-dispensing times, i.e. from about 9 or 10 in the evening to about 7 or 8 a.m. the next day. When the facility is closed to dispensing, vapor pressure growth exceeds a level of +3.0 inches, thus cracking any system vents and dumping unfiltered hydrocarbons to the atmosphere. And negative pressure can reduce to lower than about −2.0 inches, increasing air intake into the system through pressure relief vents. 
     Turning to system  10  according to the invention shown in  FIG. 1  and operationally illustrated in  FIG. 4 , the system cycles the single filter  17  between filtering and unloading states. 
     When dispensing stops or significantly slows, the pressure in the gasoline storage tank will rise. This typically occurs at night. 
     The high sensor  25  continuously monitors storage tank pressure. When the pressure in the storage tank exceeds the preset limit, the canister solenoid valve  27  is opened by the control panel  26 . This allows any further growth in the storage tank  13  to vent through the canister  17 . The adsorbent material in the canister  17  allows the cleaned or filtered air portion of the volume to pass through the canister and vent to atmosphere while the hydrocarbon portion of the volume is loaded onto the adsorbent material. Typically, the set point limit for this higher pressure is slightly above local atmospheric pressure. This is done so any growth in the tank that would cause pressure and fugitive emissions is controlled.  FIG. 4  shows an example where the high pressure is set at approximately +0.20 inch of water column. 
     When the customer dispensing begins again, the net negative volume exchange with the vehicles again draws the storage tank pressure in area  40  into a vacuum. The low pressure sensor  26  also continuously monitors the storage tank  13  pressure. When the pressure in the storage tank  13  falls below the preset limit, the canister solenoid valve  27  is opened by the control panel  20 . This allows atmospheric air to be drawn in to the storage tank  13  through the canister  17  and vent line  18 . As fresh air is passed through the canister  17  which contains adsorbed hydrocarbon, the hydrocarbons are removed and returned to the storage tank  13 . The cleaning or regenerating of the adsorbent material allows for the adsorbent material to be substantially free of hydrocarbon before the next loading cycle begins.  FIG. 4  shows an example where the low pressure sensor is set at approximately −2.0 inch of water column. An extra benefit of this unloading process is that with hydrocarbon returning to the storage tank  13  with the ingested air, less total air is drawn in which results in less evaporation and pressure growth during the next idle time and loading cycle. 
     In the event that during a loading cycle, the adsorbent material of filter  17  becomes substantially filled, hydrocarbon will begin to exhaust from the canister  17  to the atmosphere through vent line  18 . The exhaust hydrocarbon sensor  28  is continuously monitoring the effluent of the canister  18  and when a hydrocarbon concentration exists in the effluent in excess of the hydrocarbon sensor preset threshold, an audible and/or visual alarm will sound, and the solenoid valve  27  will be closed and not allowed to open even upon a high pressure sensing at sensor  25  until the system  10  is reset. This stops all flows out of the canister  17  to the environment. But, when this alarm condition exists, the control panel  20  will continue to allow the low pressure sensor  26  to open the solenoid valve  27  so the adsorbent material can be unloaded of hydrocarbon. 
     As above noted, typical adsorbent material canister emission control systems employ at least two canisters. This allows simultaneous loading of one canister and unloading of a second canister. The invention of the currently disclosed system  10  allows the adsorbent system to use only a single canister. This is accomplished by controlling the pressure swing in the storage tanks to definite and separate intervals; loading and unloading occur in a series instead of a parallel. As a result, cost and complexity of additional canisters is eliminated, as is the cost and complexity of an active vapor assist or vacuum system. 
     While the foregoing has discussed one invention embodiment primarily with a balance nozzle, as noted, an assist-type nozzle could be used with system  10 . Such an assist nozzle may or may not make a tight vapor seal to the vehicle fill neck, but has a vacuum source to pull air/vapor from the vehicle during dispensing. When filling an ORVR vehicle, the assist nozzle will sense the presence of the ORVR equipped vehicle and reduce the air/vapor flow returned to the gasoline storage tank by one of the following methods: measuring pressure or vacuum in the vehicle gasoline tank, measuring the hydrocarbon concentration in the air/vapor flow to the storage tank or other means. This again will result in a reduction in volume in the gasoline storage tank and will tend the pressure in said tank to reduce below local atmospheric pressure. With the gasoline storage tank below local atmospheric pressure, no gasoline vapor emissions from said tank will occur. 
     While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user.