Abstract:
A volatile liquid vapor recovery system is used to recover vapors produced in the loading of shipping vehicles with volatile liquid product from a storage tank. The recovery system uses a primary vessel with an adsorption bed for adsorbing the volatile liquid vapors and venting clean air including oxygen to the atmosphere. The recovery system regenerates the adsorption bed by recovering the volatile liquid vapors from the adsorption bed and directly delivering said vapors to the storage tank. The system may be adapted to remove oxygen from the primary vessel prior to regeneration, such as by purging and venting the primary vessel with a purge gas or by providing a secondary vessel to receive oxygen and vapors from the primary vessel prior to regeneration of the first adsorption bed. Adsorbed volatile liquid vapor from the secondary vessel can be recycled to the primary vessel for conservation.

Description:
[0001]    This application claims priority to U.S. PROVISIONAL Patent Application Ser. No. 62/060,679, filed Oct. 7, 2014, the disclosure of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to an apparatus and process for recovering volatile liquids from air-volatile liquid vapor mixtures expelled from vessels such as transportation vehicles during loading, and, more particularly, to an improved apparatus and process that efficiently removes oxygen from the recovered volatile liquid vapor and returns said recovered volatile liquid vapor to a storage tank used to load said vessels. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the process of loading volatile liquid products into a vessel, such as for transport, volatile liquid vapor is produced. Venting such vapor into the atmosphere is problematic both from an environmental perspective, and because valuable product is lost in the process. For example, a typical loading facility&#39;s air permit may be limited to 50 tons per year of volatile organic compounds (VOCs). By loading a single 200 barrel truck each day and venting the gases into the atmosphere, 14.8 tons of the 50 ton annual limit will be exhausted. Accordingly, volatile liquid vapor recovery systems have been used to remove and recover the volatile liquid vapor. 
         [0004]    Another consideration in the loading and recovery process is that an empty tanker truck or railcar includes a relatively large volume of air. About 21% of that air is oxygen. When a tanker truck is filled with a volatile liquid product, that air is displaced into the volatile liquid vapor recovery system normally utilized to collect the volatile liquid vapor produced during the filling or loading process. That system traps volatile liquid vapors which are absorbed by a bed of adsorbent and vents much of the “clean” air to the atmosphere. 
         [0005]    However, in a conventional recovery system, air, including oxygen, is maintained in the overhead space of the reaction vessel containing the bed of adsorbent and in the lines leading to the vent. This can be problematic, as loading facilities generally have limits regarding the amount of oxygen that may be present. For example, a natural gas facility is typically limited to 10 ppm per ft 3  of oxygen in the natural gas sales pipe line. When vapor balancing a 200 barrel load to a storage tank in order to reduce emissions, the process will inject on average 16 ft 3  per minute of a 124,000 ppm O 2  gas for a one hour period. Conventional vapor recovery systems are not equipped to both remove the oxygen from the recovery system and to return oxygen free (or significantly oxygen reduced) recovered volatile liquid vapor to a storage tank. 
         [0006]    Accordingly, the present invention addresses the need to efficiently remove oxygen from a volatile liquid vapor recovery system. 
       SUMMARY OF THE INVENTION 
       [0007]    This document describes a system that virtually eliminates ingestion of air, including the oxygen contained therein, into a storage tank from a volatile liquid vapor recovery system when the volatile liquid vapors trapped in a bed of adsorbent are released from the bed of adsorbent and returned to the storage tank. 
         [0008]    In a first embodiment, a vapor recovery system for recovering volatile liquid vapor produced when loading a vessel from a storage tank is disclosed. The vessel may comprise a transportation vessel, such as a truck, a train car, or any other shipping vessel. The storage tank may include an underground storage tank such as one used to store a volatile liquid product before being loaded for transport. 
         [0009]    The system may comprise a product handling circuit including a primary reaction vessel holding a first bed of adsorbent adapted to adsorb the volatile liquid vapor and a primary conduit for transporting volatile liquid vapor from the vessel to the primary reaction vessel, and a bed regeneration circuit including a secondary reaction vessel holding a second bed of adsorbent, said secondary reaction vessel adapted to receive vapor from the primary reaction vessel, a vapor pump wherein an upstream end of said vapor pump is connected by a first conduit to said primary reaction vessel and by a second conduit to said secondary reaction vessel and wherein a downstream end of said vapor pump is connected by a third conduit to said secondary reaction vessel and is further connected to a fourth conduit adapted to directly connect the primary reaction vessel to the storage tank, via the vapor pump. In the context of this disclosure, the term “directly connect” or “directly connected” shall mean that two elements are connected to one another without any further separation, adsorption, or absorption element between the two elements. 
         [0010]    In one aspect, the system may include a first flow control valve in said first conduit for isolating said product handling circuit from said regeneration circuit when loading the vessel with volatile liquid product and collecting volatile liquid vapor on said first bed of adsorbent in said primary reaction vessel. The system may further include a second flow control valve in the second conduit for controlling flow of volatile liquid vapor from said secondary reaction vessel to said vapor pump. A third flow control valve may be provided in said third conduit for controlling flow of volatile liquid vapor from said vapor pump to said secondary reaction vessel. A fourth flow control valve may be provided in said fourth conduit for controlling flow of volatile liquid vapor from said vapor pump to said storage tank. 
         [0011]    The product handling circuit may further include an atmospheric relief valve between said vessel and said primary reaction vessel. 
         [0012]    In a further aspect, the system may include a source of nitrogen connected to said primary reaction vessel. 
         [0013]    In another aspect, the system may include a diffusion nozzle connected to said fourth conduit for delivering volatile liquid vapors into volatile liquid product held in said storage tank. 
         [0014]    The system may further include a recycle conduit connecting said regeneration circuit to said product handling circuit between said inlet and said primary reaction vessel, and a fifth flow control valve in said recycle conduit for controlling flow from the regeneration circuit to the product handling circuit. 
         [0015]    The product handling circuit may include a first pump and a bypass line around said first pump. 
         [0016]    In one aspect, the primary reaction vessel may comprise multiple reaction vessels connected in series. 
         [0017]    In another embodiment, a method is disclosed for recovering volatile liquid vapors produced when loading a tank. The method may include the steps of collecting volatile liquid vapors on a first bed of adsorbent in a primary reaction vessel while loading a volatile liquid product into the tank, displacing volatile liquid vapors and oxygen from said primary reaction vessel and collecting said volatile liquid vapors on a second bed of adsorbent in a secondary reaction vessel while venting said oxygen to atmosphere, regenerating said first bed of adsorbent by removing volatile liquid vapors from said first bed of adsorbent and directing said volatile liquid vapors to a storage tank directly connected to said primary reaction vessel, said storage tank holding volatile liquid product, and regenerating said second bed of adsorbent by removing volatile liquid vapors from said second bed of adsorbent and collecting said volatile liquid vapors on said first bed of adsorbent in said primary reaction vessel. 
         [0018]    The method may further include the step of purging said first bed of adsorbent in said primary reaction vessel with an inert gas during regeneration of said first bed. In one aspect, the method may include moving said oxygen from said first reaction vessel through said second reaction vessel before venting said oxygen to atmosphere. 
         [0019]    In a further embodiment, a vapor recovery system is disclosed for recovering volatile liquid vapor from a composition including volatile liquid vapor and oxygen produced when loading a loading vessel from a storage tank of volatile liquid product. The system may include a product handling circuit including a primary reaction vessel holding a first bed of adsorbent adapted to adsorb the volatile liquid vapor, a primary conduit for transporting the composition from the loading vessel to the primary reaction vessel, and a primary exhaust for venting oxygen to atmosphere, an oxygen removal circuit, including a secondary reaction vessel holding a second bed of adsorbent, a vapor pump, a first conduit connecting the primary reaction vessel to an upstream end of the vapor pump, a second conduit connecting a downstream end of the vapor pump to the secondary reaction vessel, and a secondary exhaust for venting oxygen to atmosphere, a product recovery circuit, including a third conduit connecting the downstream end of the vapor pump to the storage tank, wherein the product recovery circuit connects the primary reaction vessel to the storage tank with no separation, adsorption, or absorption vessel therebetween, and a recycle circuit, including a fourth conduit connecting the secondary reaction vessel to the upstream end of the vapor pump, and a recycle conduit connecting the downstream end of the vapor pump to the primary reaction vessel. In one aspect, the circuits may include at least some overlap, including the vapor pump comprising at least a part of the oxygen removal circuit as well as the product recovery circuit and the recycle circuit. 
         [0020]    The system may further include a primary valve in the primary conduit, a first valve in the first conduit, a second valve in the second conduit, a third valve in the third conduit, a fourth valve in the fourth conduit, and a recycle valve in the recycle conduit. The product handling circuit may be adapted to transport the composition from the loading vessel to the primary reaction vessel and vent oxygen to atmosphere when the primary valve and primary exhaust are opened and when the first valve and the recycle valve are closed. The oxygen removal circuit may be adapted to transport the composition from the primary reaction vessel to the secondary reaction vessel via the vapor pump and vent oxygen to atmosphere when the first valve, the second valve, and the secondary exhaust are open and when the primary exhaust, the primary valve, the third valve, the fourth valve, and the recycle valve are closed. The product recovery circuit may be adapted to regenerate the first bed of adsorbent by transporting adsorbed volatile liquid vapor from the primary reaction vessel directly to the storage tank via the vapor pump when the first valve and third valve are open and when the primary exhaust, the second valve, and the recycle valve are closed. The recycle circuit may be adapted to regenerate the second bed of adsorbent by recycling the adsorbed volatile liquid vapor from the secondary reaction vessel directly to the primary reaction vessel via the vapor pump and vent oxygen to the atmosphere when the fourth valve, the recycle valve, and the primary valve are open and the first valve, the second valve, and the third valve are closed. 
         [0021]    In another embodiment of the present invention, a vapor recovery system is disclosed for recovering volatile liquid vapor from a combination of volatile liquid vapor and oxygen collected when loading a loading vessel with volatile liquid product from a storage tank. The system may comprise a product handling circuit including a primary reaction vessel having an inlet side and an outlet side, said primary reaction vessel holding a first bed of adsorbent adapted to adsorb the volatile liquid vapor, a primary conduit connected to the inlet side for transporting volatile liquid vapor and oxygen from the loading vessel to the primary reaction vessel, and an exhaust connected to the outlet side for venting oxygen to atmosphere, and a bed regeneration circuit adapted to remove volatile liquid vapor from the first bed of adsorbent, said bed regeneration circuit including a vapor pump wherein an upstream end of said vapor pump is directly connected by a first conduit to the inlet side of said primary reaction vessel and wherein a downstream end of said vapor pump is directly connected by a second conduit to said storage tank. 
         [0022]    The system may further include a primary flow control valve in said primary conduit and a first flow control valve in the first conduit, said primary and first flow control valves adapted to isolate said product handling circuit from said regeneration circuit. The primary valve in an open condition and the first valve in a closed condition may allow volatile liquid vapor to flow from the loading vessel to the primary reaction vessel for collection on said first bed of adsorbent. The primary valve in a closed condition and the first valve in an open condition may allow volatile liquid vapor to flow directly from the primary reaction vessel to the storage tank. 
         [0023]    In one aspect, the bed regeneration circuit may include a first purge gas source connected to the outlet side of the primary reaction vessel, and the bed regeneration circuit may be adapted to transport a first purge gas from said first purge gas source through the primary reaction vessel, though the first conduit and the second conduit, and into the storage tank. The bed regeneration circuit may further include a second purge gas source connected to the inlet side of the primary reaction vessel, and the bed regeneration circuit may be adapted to transport a second purge gas from the second purge gas source through the primary reaction vessel and out the exhaust to atmosphere. 
         [0024]    In another aspect, the bed regeneration circuit may include a secondary reaction vessel holding a second bed of adsorbent, said secondary reaction vessel adapted to receive vapor and oxygen from the primary reaction vessel, a third conduit connecting a downstream end of the vapor pump to the secondary reaction vessel, and a fourth conduit connecting the secondary reaction vessel to an upstream end of the vapor pump. The third conduit may include a third valve for controlling flow from the vapor pump to the secondary reaction vessel, and wherein the fourth conduit includes a fourth valve for controlling flow from the secondary reaction vessel to the vapor pump. The system may include a recycle conduit connecting said regeneration circuit to said product handling circuit between the downstream end of the vapor pump and the primary conduit, and may further include a fifth flow control valve in said recycle conduit for controlling flow from the bed regeneration circuit to the product handling circuit. The third and fourth conduits may connect to an inlet side of the secondary reaction vessel. In this aspect, the bed regeneration circuit may include a secondary exhaust connected to an outlet side of the secondary reaction vessel. 
         [0025]    The system may include a diffusion nozzle connected to said second conduit for delivering volatile liquid vapors from the primary reaction vessel into the volatile liquid product held in said storage tank. 
         [0026]    The primary reaction vessel may comprise multiple reaction vessels connected in series. 
         [0027]    In a further embodiment of the present invention, a method is disclosed for recovering volatile liquid vapors and removing oxygen resulting from loading volatile liquid product into a loading vessel from a storage tank. The method may comprise collecting the volatile liquid vapors on a first bed of adsorbent in a primary reaction vessel and exhausting oxygen from said primary reaction vessel, and regenerating said first bed of adsorbent by removing volatile liquid vapors from said first bed of adsorbent and directly delivering said volatile liquid vapors to the storage tank. 
         [0028]    In one aspect, the method may include displacing volatile liquid vapors and oxygen from said primary reaction vessel and collecting said volatile liquid vapors on a second bed of adsorbent in a secondary reaction vessel while venting said oxygen to atmosphere. In this aspect, the method may further include regenerating said second bed of adsorbent by removing volatile liquid vapors from said second bed of adsorbent and collecting said volatile liquid vapors on said first bed of adsorbent in said primary reaction vessel. 
         [0029]    In another aspect, the method may include the step of displacing oxygen from the primary reaction vessel with a purge gas and venting said oxygen to atmosphere. 
         [0030]    In still another embodiment, the invention relates to a vapor recovery system for recovering volatile liquid vapor from a composition including volatile liquid vapor and oxygen produced when loading a loading vessel from a storage tank of volatile liquid product. The system comprises a product handling circuit including a primary reaction vessel holding a first bed of adsorbent adapted to adsorb the volatile liquid vapor, a primary conduit for transporting the composition from the loading vessel to the primary reaction vessel, and a primary exhaust for venting oxygen to atmosphere. The system further includes means for removing oxygen from the primary reaction vessel. In addition, the system comprises a product recovery circuit including a vapor pump with an upstream end and a downstream end, a first conduit connecting the primary reaction vessel to the upstream end of the vapor pump, a second conduit directly connecting the downstream end of the vapor pump to the storage tank, and a first purge gas source, wherein the product recovery circuit is adapted to deliver a first purge gas from the first purge gas source through the primary reaction vessel, the first conduit, and the second conduit to the storage tank, wherein the product recovery circuit connects the primary reaction vessel to the storage tank with no separation, adsorption, or absorption vessel therebetween. 
         [0031]    In one aspect of this embodiment, the means for removing oxygen may comprise a second purge gas source connected to the primary reaction vessel which may be adapted to deliver a second purge gas to the primary reaction vessel and displace oxygen from said primary reaction vessel and may be further adapted to vent said oxygen and said second purge gas to atmosphere. 
         [0032]    In another aspect, the means for removing oxygen may comprise a secondary reaction vessel holding a second bed of adsorbent, the vapor pump, a third conduit connecting the downstream end of the vapor pump to the secondary reaction vessel, and a secondary exhaust connected to the secondary reaction vessel for venting oxygen to atmosphere. The system may further include a recycle circuit, including a fourth conduit connecting the secondary reaction vessel to the upstream end of the vapor pump, and a recycle conduit connecting the downstream end of the vapor pump to the primary reaction vessel. 
         [0033]    The system may further include a diffusion nozzle attached to the second conduit for diffusing volatile liquid vapor into the volatile liquid product in the storage tank. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a block diagram of one embodiment of a vapor recovery system for reducing volatile liquid vapor emissions while simultaneously substantially eliminating oxygen ingestion; 
           [0035]      FIG. 2  is a block diagram similar to  FIG. 1  but illustrating Phase 1 operation of the system; 
           [0036]      FIG. 3  is a block diagram similar to  FIG. 1  but illustrating Phase 2 operation of the system; 
           [0037]      FIGS. 4A and 4B  are block diagrams similar to  FIG. 1  but illustrating Phase 3 operation of the system; 
           [0038]      FIG. 5  is a block diagram similar to  FIG. 1  but illustrating Phase 4 operation of the system; 
           [0039]      FIG. 6  is a block diagram of another embodiment of a vapor recovery system of the present invention; 
           [0040]      FIG. 7  is a block diagram similar to  FIG. 6  but illustrating a product handling phase of operation of the system; 
           [0041]      FIGS. 8A and 8B  are block diagrams similar to  FIG. 6  but illustrating a product recovery phase of operation of the system; and 
           [0042]      FIG. 9  is a block diagram similar to  FIG. 6  but illustrating an oxygen removal phase of operation of the system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    A vapor recovery system  10  is provided for recovering volatile liquid vapor produced when loading a tank T of a tanker truck, a railcar or the like. The vapor recovery system  10  includes a product handling circuit  12  and a bed regeneration circuit  14 . 
         [0044]    The product handling circuit  12  may include (a) a storage tank  16 , such as the underground storage tank illustrated in the drawing  FIGS. 1-5 , (b) a volatile liquid product outlet  18  that is connected to the tanker truck T, (c) a volatile liquid vapor inlet  20  that is also connected to the tanker truck and (d) a primary reaction vessel including a first bed of adsorbent. In the illustrated embodiment the primary reaction vessel comprises two vessels  22   a,    22   b  connected in series with each vessel including a bed of adsorbent  24   a,    24   b.  While two vessels  22   a,    22   b  are shown, it could be appreciated that substantially any number of vessels from  1 -n may be provided as long as they have the necessary capacity to capture all volatile liquid vapors generated during loading of the tanker truck T. 
         [0045]    As further illustrated in  FIG. 1 , the product handling circuit  12  may include a primary conduit  27 , which may include a valve  31  for transporting volatile liquid vapor to the primary reaction vessels  22   a,    22   b.  Further the circuit  12  may include an optional first pump  26  for inducing flow through the primary conduit  27 . The circuit  12  may include an optional bypass line  28  with a solenoid valve  30  for bypassing the first pump  26  if present. A vent  32  is connected to the primary reaction vessel  22  as is an optional source of purge gas  34 , such as nitrogen. In addition, an atmospheric relief valve  35  is connected in the circuit  12  between the volatile liquid vapor inlet  20  and the primary reaction vessel  22   a,    22   b  (or first pump  26  if present). 
         [0046]    The bed regeneration circuit  14  may include a secondary reaction vessel  36  having a second bed of adsorbent  38 . The bed regeneration circuit  14  may also include a vapor pump  40  wherein an upstream end  42  may be connected by a first conduit  44  to the primary reaction vessel  22  and by a second conduit  46  to the secondary reaction vessel  36 . In addition, a downstream end  48  of the vapor pump  40  is connected by a third conduit  50  to the storage tank  16  and by a fourth conduit  52  to the secondary reaction vessel  36 . Further, the bed regeneration circuit  14  includes a recycle conduit  54  that connects the downstream end or minimum  48  of the vapor pump  40  to the product handling circuit  12  between the inlet  20  and the primary reaction vessel  22 /optional first pump  26 . 
         [0047]    The bed regeneration circuit  14  may also include a first flow control valve  56  in the first conduit  44 , a second flow control valve  58  in the second conduit  46 , a third flow control valve  60  in the third conduit  50 , a fourth flow control valve  62  in the fourth conduit  52  and a fifth flow control valve  64  in the recycle conduit  54 . Further an optional diffusion nozzle  66  may be provided on the end of the third conduit  50  for delivering volatile liquid vapors into the volatile liquid product P held in the storage tank  16 . 
         [0048]    With reference to  FIG. 2 , during a Phase 1 of operation, volatile liquid product P is delivered from the storage tank  16  to the tanker truck T. This is done by connecting the volatile liquid product outlet  18  on the delivery line  68  and the volatile liquid vapor inlet  20  to the tanker truck T. Volatile liquid product P is delivered to the tanker truck T through the delivery line  68  and outlet  18  by gravity feed, a dedicated pump (not shown) in the delivery line  68  or a pump (not shown) on the tanker truck T. As the volatile liquid product P is delivered to the tanker truck T, volatile liquid vapor is produced. During Phase 1, valves  33 ,  56  and  64  are closed, while valves  30 ,  31 , and  32  are opened. This volatile liquid vapor passes through the inlet  20  and travels along the conduit  70  to primary reaction vessels  22   a,    22   b.  The optional pump  26  may be operated to ensure flow of vapor to the reaction vessels  22   a,    22   b  where the volatile liquid vapor is captured on the beds of adsorbent  24   a,    24   b  and air/oxygen is returned to atmosphere through the vent  32 . The atmospheric relief valve  35  ensures that the vapor pressure within the product handling circuit  12  never exceeds a safe operating maximum or minimum value. Phase 1 may be referred to as utilizing the product handling circuit of the present invention. 
         [0049]    Phase 2 of the operation is an optional phase that may be initiated after the tanker truck T has been loaded with volatile liquid product P. Phase 2 of the operation is illustrated in  FIG. 3 . During Phase 2 of operation, valves  30 ,  31 ,  32 ,  58 ,  60 , and  64  are closed and valves  56  and  62  are opened. Pump  40  is then activated and a light vacuum is drawn on the primary reaction vessels  22   a,    22   b  so that oxygen in those reaction vessels and the first of the volatile liquid vapors are displaced and moved from the reaction vessels  22   a,    22   b  through the first conduit  44  to the upstream end  42  of the pump  40 . The oxygen and vapors are then driven by the pump  40  through the downstream end  48  and the fourth conduit  52  and fourth flow control valve  62  to the secondary reaction vessel  36  wherein volatile liquid vapors are adsorbed by the second bed of adsorbent  38  while oxygen is exhausted into the atmosphere through the vent  72 . In one embodiment, as illustrated in  FIG. 3 , a second vapor pump  41  may be provided in parallel with the first vapor pump  40 , for aiding in drawing vapors from the primary reaction vessels  22   a,    22   b.  Once a majority of the oxygen has been removed from the primary reaction vessels  22   a,    22   b,  the third phase may be initiated. Phase 2 may be referred to as utilizing the oxygen removal circuit. 
         [0050]    The Phase 3 is a two-part phase, as is illustrated in  FIGS. 4A and 4B . In the event that the optional Phase 2 is utilized, the third phase may be initiated by closing vent  72  and the fourth flow control valve  62  and by opening the third control valve  60  (the fifth flow control valve  64  remains closed). In the case of a user proceeding directly from Phase 1 to Phase 3, valves  30 ,  31 ,  32 , and  58  may be closed, and valves  56  and  60  may be opened. During part one of the third phase of operation, a deeper vacuum is drawn on the primary reaction vessels  22   a,    22   b  to regenerate the beds  24   a,    24   b  of adsorbent. More specifically, the pump  40  generates a vacuum that removes the previously captured volatile liquid vapors from the beds  24   a,    24   b  of adsorbent in the primary reaction vessels  22   a,    22   b  which travel through the first conduit  44  and first flow control valve  56  to the upstream end  42  of the pump  40  and then travel through the pump  40  and the downstream end  48  of that pump through the third conduit  50  and third flow control valve  60  to the storage tank  16 . In the illustrated embodiment, the conduit  50  includes a diffusion nozzle  66  on the end thereof that is provided in the storage tank  16  below the upper level of the volatile liquid product P so that the volatile liquid vapors are diffused into the product in the storage tank where they are condensed. 
         [0051]    During part two of Phase 3, as illustrated in  FIG. 4B , valve  33  may be opened and a purge gas may be drawn through the beds of absorbent  24   a,    24   b  in the primary reaction vessels  22   a,    22   b  to purge the beds of volatile liquid vapors at the end of the third phase. This purge gas may include any gas suitable for a given condition, such as air, nitrogen, or methane (such as in the case of a petroleum based product). In this embodiment those volatile liquid vapors are delivered directly from the primary reaction vessels  22   a,    22   b  to the storage tank  16  with the purge gas. Significantly, it should be appreciated that oxygen originally present in the primary reaction vessels  22   a,    22   b  may be vented to the atmosphere through the second reaction vessel  36  during the second phase and, as such, the majority of the oxygen is not returned to the storage tank  16  with the volatile liquid vapor. Thus, the presence of oxygen is minimized or substantially eliminated upstream of the tanker truck T from the storage tank  16 . Phase 3 may be referred to as utilizing the product recovery circuit of the present invention. 
         [0052]    After the beds of adsorbent  24   a,    24   b  in the primary reaction vessels  22   a,    22   b  have been completely regenerated, Phase 4 of the operation may be initiated, as is illustrated in  FIG. 5 . It should be noted that Phase 4 is also an optional phase, and generally may only be necessary in the event that optional Phase 2 is utilized. During phase 4 valves  33 ,  56 ,  60  and  62  are closed and valves  32 ,  58 ,  64 , and  74  are opened. The vapor pump  40  (and optionally the second vapor pump  41 ) then draws purge air through purge conduit  76 , through the secondary reaction vessel  36  and second bed of adsorbent  38 , the second conduit  46  and the second flow control valve  58  to the upstream end  42  of the pump  40 . This desorbs the volatile liquid vapors absorbed on the second bed of adsorbent  38  which then pass through the pump  40  past the downstream end  48  and then along the recycle conduit  54  and the bypass line  28  back to the primary reaction vessels  22   a,    22   b.  There, volatile liquid vapors are absorbed onto the beds of adsorbent  24   a,    24   b  while the oxygen and other gases present in the purge air are then vented to the atmosphere through the vent  32 . This completes the regeneration of the second bed  38  of adsorbent. As a result, the entire operating cycle has been completed and the system  10  is now ready for Phase 1 operation and the capture of volatile liquid vapors from loading the next tanker truck T. Phase 4 may be referred to as utilizing a recycle circuit of the present invention. 
         [0053]    In one aspect, Phase 3 may be considered a bed regeneration circuit. In another aspect, Phase 2, Phase 3, and Phase 4 may jointly be referred to as utilizing the bed regeneration circuit of the present invention. 
         [0054]    In a further embodiment, as illustrated in  FIG. 6 , a vapor recovery system  110  is provided for recovering volatile liquid vapor produced when loading a tank T of a tanker truck, a railcar or the like. The vapor recovery system  110  includes a product handling circuit  112  and a bed regeneration circuit  114 . 
         [0055]    The product handling circuit  112  may be adapted to receive volatile liquid vapor produced when volatile liquid product P from a storage tank  16  is loaded via a volatile liquid product outlet  18  that is connected to the tanker truck T. A volatile liquid vapor inlet  20  that is connected to the tanker truck may be adapted to deliver the volatile liquid vapor to the product handling circuit  112 , which may include a reaction vessel including a first bed of adsorbent  124 . In the illustrated embodiment the reaction vessel comprises two vessels  122   a,    122   b  connected in series with each vessel including a bed of adsorbent  124   a,    124   b.  While two vessels  122   a,    122   b  are shown, it could be appreciated that substantially any number of vessels from 1-n may be provided as long as they have the necessary capacity to capture all volatile liquid vapors generated during loading of the tanker truck T. 
         [0056]    As further illustrated in  FIG. 6 , the product handling circuit  112  may include an optional first pump  126 . The first pump may be connected to a primary conduit  127  with a valve  131  for regulating flow therethrough. Further the circuit  112  may include a bypass line  128  with a solenoid valve  130  for bypassing the first pump  126  if present. A vent  132  is connected to the reaction vessels  122   a,    122   b  as is a first purge source  134  as a first source of purge gas. The first purge source  134  may supply any gas suitable for a given condition, such as air, nitrogen, or methane (such as may be used in the case of the volatile liquid being a petroleum product). In the case of the first purge source  134  supplying air, the first purge source may simply be a vent open to atmosphere. An atmospheric relief valve  135  may be connected to the circuit  112  between the volatile liquid vapor inlet  20  and the reaction vessel  122   a,    122   b  (or first pump  126  if present). 
         [0057]    The bed regeneration circuit  114  may include a vapor pump  140  connecting the reaction vessel  122   a,    122   b,  via a first conduit  144  directly to the storage tank  16  via a second conduit  150 . The first conduit  144  may include a first valve  156 , and the second conduit  150  may include a second valve  160 . Further an optional diffusion nozzle  166  may be provided on the end of the second conduit  150  for delivering volatile liquid vapors into the volatile liquid product P held in the storage tank  16 . 
         [0058]    The bed regeneration circuit  114  may also include a second purge source  170 , which may supply a purge gas, such as nitrogen or methane (such as may be used in the case of the volatile liquid being a petroleum product). The second purge source  170  may be connected to an inlet of the reaction vessel  122   a,    122   b  via a purge conduit  174 . A purge valve  172  may be provided in conjunction with the purge conduit  174  to regulate flow therethrough. 
         [0059]    With reference to  FIG. 7 , during a product handling phase of operation, volatile liquid product P is delivered from the storage tank  16  to the tanker truck T. This is done by connecting the volatile liquid product outlet  18  on the delivery line  68  and the volatile liquid vapor inlet  20  to the tanker truck T. Volatile liquid product P is delivered to the tanker truck T through the delivery line  68  and outlet  18  by gravity feed, a dedicated pump (not shown) in the delivery line  68  or a pump (not shown) on the tanker truck T. As the volatile liquid product P is delivered to the tanker truck T, volatile liquid vapor is produced. During the product handling phase, valve  133 ,  156 , and  172  are closed, while valves  130 ,  131 , and  132  are opened. This volatile liquid vapor passes through the inlet  20  and travels along the conduits  127 ,  128  to primary reaction vessels  122   a,    122   b.  The optional pump  126  may be operated to ensure flow of vapor to the reaction vessels  122   a,    122   b  where the volatile liquid vapor is captured on the beds of adsorbent  124   a,    124   b  and air/oxygen is returned to atmosphere through the vent  132 . The atmospheric relief valve  135  ensures that the vapor pressure within the product handling circuit  112  never exceeds a safe operating maximum or minimum value. 
         [0060]    After the tanker truck T has been loaded with volatile liquid product, or after the bed of adsorbent has been at least partially saturated with adsorbed volatile liquid vapor, a product recovery phase may be initiated, as is illustrated in  FIGS. 8A and 8B . During the initial portion of the product recovery phase, as shown in  FIG. 8A , the adsorbed volatile liquid vapor may be removed from the reaction vessels  122   a,    122   b,  and delivered directly to the storage tank  16 . This portion of the product recovery phase requires that valves  156  and  160  be opened, while valves  130 ,  131 ,  132 ,  133  and  172  are closed. 
         [0061]    During this phase, the vapor pump  140  may draw a vacuum on the reaction vessels  122   a,    122   b  to regenerate the beds  124   a,    124   b  of adsorbent. More specifically, the vacuum created by the vapor pump  140  removes the previously captured volatile liquid vapors from the beds of adsorbent  124   a,    124   b.  A second vapor pump may be provided in parallel with the first vapor pump  140 , for aiding in drawing vapors from the primary reaction vessels  122   a,    122   b.    
         [0062]    The recovered vapors may travel through the first conduit  144  and the first valve  156 , through the vapor pump  140 , and through the second conduit  150  and second valve  160  to the storage tank  16 . Accordingly, the reaction vessels  122   a,    122   b  and the storage tank are directly connected to one another, as there is no separation, adsorption, or absorption element therebetween. The recovered product may be vented into the storage tank  16  above the product P, or may be released below the level of the product P, so as to be diffused and condensed therein. In one embodiment, diffusion nozzle  166  may aid in the diffusion of the recovered volatile liquid vapor within the product. 
         [0063]    As is illustrated in  FIG. 8B , valve  133  may be opened to complete the product recovery phase. This allows purge gas to flow from the first purge source  134 , through the reaction vessels  122   a,    122   b.  Vapor pump  140  may draw the purge gas and remaining recovered volatile liquid vapor from the reaction vessels  122   a,    122   b,  and deliver said purge gas and vapors directly to the storage tank  16 . This purge gas and vapor combination may follow the same path as the vapors in the first portion of the product recovery phase, such as via first conduit  144  and second conduit  150 , to the storage tank  16 . 
         [0064]    In some instances, it may be desirable to remove oxygen or any other gases in the reaction vessels  122   a,    122   b,  such as prior to the product recovery phase. This may be advantageous in the case of the presence of oxygen or other gas being detrimental to the product in the storage tank. Accordingly, an optional oxygen removal phase may be implemented, as is illustrated in  FIG. 9 . During the oxygen removal phase, valves  132  and  172  may be opened, and valves  130 ,  131 , and  133  may be closed. This allows a second purge gas from the second purge source  170  to flow through the purge conduit  174 , through the reaction vessels  122   a,    122   b,  and vent through valve  132 , so as to exit the system, such as in the case of venting to atmosphere. In one aspect, the second purge gas may be an inert gas such as nitrogen, or any other gas with little or no effect on the product P in the storage tank  16 . For instance, the second purge gas may be methane in the case of the product P comprising a petroleum product. 
         [0065]    The oxygen removal phase allows the second purge gas to force oxygen (and/or any other undesirable gas) out of the reaction vessels  122   a,    122   b,  leaving the oxygen or other undesirable gas removed or substantially removed from the system. Accordingly, during the subsequent product recovery phase, the storage tank is contaminated with little to no oxygen or other undesirable gas. 
         [0066]    The foregoing has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Obvious modifications and variations are possible in light of the above teachings. For example, while the illustrated embodiment includes a diffusion nozzle  66  on the end of the conduit  50  in the storage tank  16  beneath the surface of the liquid product P, such a diffusion nozzle is not required. Volatile liquid vapors may be simply returned to the storage tank  16  and released in the head space above the surface of the liquid product P if desired. All such modifications and variations are within the scope of the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.