Patent Publication Number: US-7222647-B2

Title: Apparatus for dispensing compressed natural gas and liquified natural gas to natural gas powered vehicles

Description:
RELATED APPLICATIONS 
   The present application is a divisional of U.S. patent application Ser. No. 10/435,166, filed on May 9, 2003 now U.S. Pat. No. 6,899,146. 

   GOVERNMENT RIGHTS 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to fueling stations for dispensing natural gas to vehicles and, more particularly, to fueling stations having the capacity to provide and dispense both compressed natural gas (CNG) and liquified natural gas (LNG) on-demand. 
   2. State of the Art 
   Natural gas is a known alternative to combustion fuels such as gasoline and diesel. Much effort has gone into the development of natural gas as an alternative combustion fuel in order to combat various drawbacks of gasoline and diesel including production costs and the subsequent emissions created by the use thereof. As is known in the art, natural gas is a cleaner burning fuel than many other combustion fuels. Additionally, natural gas is considered to be safer than gasoline or diesel since natural gas rises in the air and dissipates, rather than settling as do other combustion fuels. However, various obstacles remain which have inhibited the widespread acceptance of natural gas as a combustion fuel for use in motor vehicles. 
   To be used as an alternative combustion fuel, natural gas is conventionally converted into compressed natural gas (CNG) or liquified (or liquid) natural gas (LNG) for purposes of storing and transporting the fuel prior to its use. In addition to the process of converting natural gas to CNG or LNG, additional facilities and processes are often required for the intermediate storage of, and the ultimate dispensing of, the natural gas to a motor vehicle which will burn the natural gas in a combustion process. 
   Conventional natural gas refueling facilities are currently prohibitively expensive to build and operate as compared to conventional fueling facilities. For example, it is presently estimated that a conventional LNG refueling station costs approximately $350,000 to $1,000,000 to construct while the cost of a comparable gasoline fueling station costs approximately $50,000 to $150,000. One of the reasons for the extreme cost difference is the cost of specialized equipment used in handling, conditioning and storing LNG which is conventionally stored as a cryogenic liquid methane at a temperature of about −130° C. to −160° C. (−200° F. to −250° F.) and at a pressure of about 25 to 135 pounds per square inch absolute (psia). 
   An additional problem inhibiting the widespread acceptance of natural gas as a combustion fuel for motor vehicles is that, currently, some motor vehicles which have been adapted for combustion of natural gas require CNG while others require LNG thus requiring different types of fueling facilities for each. For example, LNG facilities conventionally dispense natural gas from storage tanks wherein the natural gas is already conditioned and converted to LNG. The LNG is often conventionally delivered to the storage tanks by way of tanker trucks or similar means. On the other hand, CNG facilities often draw natural gas from a pipeline or similar supply, condition the natural gas and then compress it to produce the desired end product of CNG. 
   Some efforts have been made to provide LNG and CNG from a single facility. For example, U.S. Pat. No. 5,505,232 to Barclay, issued Apr. 9, 1996 is directed to an integrated refueling system which produces and supplies both LNG and CNG. The disclosed system is stated to operate on a small scale producing approximately 1,000 gallons a day of liquefied or compressed fuel product. The Barclay patent teaches that a natural gas supply be subjected to passage through a regenerative purifier, so as to remove various constituents in the gas such as carbon dioxide, water, heavy hydrocarbons and odorants prior to processing the natural gas and producing either LNG or CNG. Thus, as with conventional CNG facilities, it appears that the system disclosed in the Barclay patent requires location in close proximity to a natural gas pipeline or similar feed source. 
   Additionally, the system disclosed in the Barclay patent requires the natural gas to be processed through a liquefier regardless of whether it is desired to produce LNG or CNG. The requirement of an on-site liquefier may unnecessarily increase the complexity and cost of constructing a natural gas refueling facility, thus keeping the facility from being a realistic alternative to a conventional gasoline fueling facility. 
   Another example of a combined LNG and CNG fueling facility is disclosed in U.S. Pat. No. 5,315,831 to Goode et al, issued May 31, 1994. The Goode patent discloses a fueling facility which includes a volume of LNG stored in a cryogenic tank. LNG is drawn from the storage tank and dispensed to vehicles as required. CNG is produced by drawing off a volume of the LNG from the storage tank and flowing the LNG through a high-efficiency pump and a vaporizer system, which CNG is then dispensed to a vehicle as required. 
   While the Goode and Barclay patents disclose integrated fileling stations which purportedly provide the capability of dispensing LNG and/or CNG, improvements to such facilities are still desired in order to make such fueling facilities efficient, practical and comparable in costs of construction and operation relative to conventional gasoline fueling facilities. 
   In view of the shortcomings in the art, it would be advantageous to provide an integrated fueling system which is able to dispense LNG, CNG or both on demand and which is of simple construction, provides simple, efficient operation and otherwise improves upon the current state of the art. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with one aspect of the present invention a fueling station is provided. The fueling station includes at least one pump configured to boost a pressure of a volume of liquefied natural gas (LNG) supplied thereto including at least one pressurized output configured to supply pressurized LNG. At least one diverter valve is operably coupled to the at least one pressurized output of the at least one pump, wherein the at least one diverter valve is configured to selectively divert the flow of any pressurized LNG flowing from the at least one pressurized output of the at least one pump between a first flow path and a second flow path. At least one LNG dispensing unit is in fluid communication with the first flow path. A vaporizer is in fluid communication with the second flow path. The vaporizer is configured to receive and convert pressurized LNG to compressed natural gas (CNG). At least one CNG dispensing unit in fluid communication with the vaporizer. 
   In accordance with another aspect of the invention another fueling station is provided. The fueling station includes a multiplex pump configured to boost the pressure of volume of liquified natural gas (LNG) supplied thereto. The multiplex pump includes at least two pistons wherein each piston has an individual pressurized output configured to provide a supply of pressurized LNG. At least one LNG dispensing unit is disposed in selective fluid communication with the pressurized output of each of the at least two pistons of the multiplex pump. A vaporizer, configured to receive and convert LNG to compressed natural gas (CNG), is placed in selective fluid communication with the pressurized output of each of the at least two pistons of the multiplex pump. At least CNG dispensing unit in is disposed in fluid communication with the vaporizer. 
   In accordance with another aspect of the present invention a natural gas fueling facility is provided. The fueling facility includes a source of saturated liquified natural gas (LNG) such as a cryogenic storage tank containing a volume of saturated natural gas. The fueling facility further comprises at least one fueling station. The fueling station includes a multiplex pump in fluid communication with the source of saturated LNG. The multiplex pump includes at least two pistons wherein each piston has an individual pressurized output configured to provide a supply of pressurized LNG. At least one LNG dispensing unit is disposed in selective fluid communication with the pressurized output of each of the at least two pistons of the multiplex pump. A vaporizer, configured to receive and convert LNG to compressed natural gas (CNG), is placed in selective fluid communication with the pressurized output of each of the at least two pistons of the multiplex pump. At least CNG dispensing unit is disposed in fluid communication with the vaporizer. 
   In accordance with a further aspect of the present invention, a method is provided for dispensing natural gas fuel. The method includes providing a supply of saturated liquified natural gas (LNG) at a first pressure to a pump. The saturated LNG is passed through a pump to increasing the pressure of the saturated LNG to a second elevated pressure. A first flow path is provided between the pump and an LNG dispensing unit. A second flow path is provided between the pump and a compressed natural (CNG) dispensing unit. LNG is selectively passed through the first flow path, the second flow path or through both the first and the second flow paths. The pressure of any LNG flowing through the first flow path is reduced to an intermediate pressure, at least a portion of which reduced pressure LNG is subsequently dispensed through the LNG dispensing unit. Any LNG flowing through the second flow path is vaporized to produce CNG therefrom, at least a portion of which CNG is dispensed through the CNG dispensing unit. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
       FIG. 1  is a perspective of an exemplary fueling facility according to an embodiment of the present invention; 
       FIG. 2  is a perspective of an exemplary fueling station according to an embodiment of the present invention; 
       FIG. 3  is another perspective of the fueling station shown in  FIG. 2 ; 
       FIG. 4  is a simplified schematic of a fueling station according to an embodiment of the present invention; 
       FIG. 5  is a process flow diagram of a fueling station according to an embodiment of the present invention; 
       FIGS. 6A through 6E  are diagrams of potential multiplexing arrangements in accordance with various embodiments of the present invention; 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , an exemplary fueling facility  100  is shown for on-demand dispensing of LNG, CNG or both. The fueling facility  100  may include one or more fueling stations  102 A and  102 B for dispensing fuel to, for example, a motor vehicle configured to operate through the combustion of natural gas. A storage tank  104 , configured for the cryogenic storage of LNG at, for example, approximately 30 psia and under saturated conditions, supplies LNG to the fueling stations  102 A and  102 B. It is noted that, while 30 psia is discussed as an exemplary pressure of an LNG supply, other pressures may be acceptable, including pressures as low as 0.5 psia, so long as they are capable of providing a flow from the LNG supply (e.g., the storage tank  104 ) to the pump  106  as shall be described in more detail below herein. It is further noted that, while the LNG supply is referred to herein as saturated LNG, such generally refers to a liquid substantially at equilibrium under specified temperature and pressure conditions. More generally, the LNG supply is in a liquid state capable of being pumped. 
   With both fueling stations  102 A and  102 B being substantially similar in construction and operation, reference only to the components of the first fueling station  102 A will be made for sake of convenience and simplicity. The storage tank  104  is coupled to the pump  106  which, depending on current demand, provides pressurized LNG to either an LNG dispensing nozzle  108  for dispensing into a vehicle&#39;s tank, or to a vaporizer  110  for conversion of the LNG to CNG through the addition of thermal energy thereto. The vaporizer  110  is coupled with a CNG outlet  112  which is coupled to a CNG dispensing device (not shown in  FIG. 1 ) for the dispensing thereof to a vehicle&#39;s tank. In one embodiment, the CNG dispensing device may be remotely located from the fueling station (e.g., by several hundred feet or more) and coupled with the CNG outlet  112 , for example, by way of underground piping. In another embodiment, the CNG dispensing device may be collocated with the fueling station  102 A. 
   With continued reference to  FIG. 1 , and also referring to  FIGS. 2 and 3 , which show additional perspective views of the fueling station  102 A (without the vaporizer  110  and showing only one LNG dispensing nozzle  108  for purposes of clarity and convenience), various piping and associated components, denoted generally as  113  in  FIG. 2 , are included in the fueling station  102 A and serve to interconnect various mechanical and thermodynamic components thereof. For example such piping and other components  113  may include various types of valves, flow meters, pressure regulators and runs of pipe or tubing associated with the operation of the fueling station  102 A, as will be discussed in greater detail below, many of which components  113  may be housed within a cold box  114  ( FIGS. 1 and 3 ) which is configured to thermally insulate such components from the surrounding environment. Such a configuration may include locating the discharge portion of the pump  106  within the cold box  114  while locating the portion of the pump which generates any substantial thermal energy substantially without the confines of the cold box  114 . 
   It is noted that, while the exemplary embodiment of the present invention shows a cold box  114  housing various components, such components may each be individually insulated from the surrounding environment and from one another instead of, or in addition to, the placement of such components within a cold box  114 . It is further noted that various valves, piping, tubing or other components associated with the production of CNG (such components being set forth in greater detail below herein) may also be insulated depending, for example, on the environment in which the fueling facility is placed in service. 
   The fueling stations  102 A and  102 B may be mounted on a skid  116  such that the entire fueling facility  100  may be prefabricated and then transported to a specific site. The skid  116  may be fabricated as a single unit or may include individual skids  116 A and  116 B each associated with individual fueling stations  102 A and  102 B respectively. In the exemplary embodiment shown in  FIG. 1 , the individual skids  116 A and  1161 B are coupled together so as to form a containment berm  116 C formed about the storage tank  104 . Thus, in the embodiment shown, the storage tank  104  is not necessarily mounted on the skid  116  and is independently installed relative to the individual skids  116 A and  116 B. The use of skids  116 A and  116 B in fabricating and assembling the fuel stations  102 A and  102 B also enables relocation of the fueling facility  100  with relative ease if and when such relocation is desired. 
   It is noted that, while the exemplary fueling facility  100  is shown to include two fueling stations  102 A and  102 B supplied by a common storage tank of saturated LNG, other embodiments are contemplated and will be appreciated by those of ordinary skill in the art. For example, additional fueling stations may be coupled with the storage tank  104  depending, for example, on the capacity of the storage tank  104 . Alternatively, the fueling facility  100  may include a single fueling station if so desired. It is also noted that while the fueling stations  102 A and  102 B of the exemplary fueling facility  100  are each shown to include a single LNG dispensing nozzle  108  and a single CNG outlet  112 , the fueling stations  102 A and  102 B may employ multiple LNG nozzles  108  and/or multiple CNG outlets  112  if so desired and in order to meet anticipated demands. 
   Referring now to  FIG. 4 , a schematic of an exemplary fueling station  102 A is shown. The fueling station  102 A is coupled to the LNG storage tank  104  by way of a feed line  120 . The storage tank  104  contains a volume  122  of saturated LNG and a volume  124  of natural gas vapor which provides a vapor head within the storage tank  104 . The feed line  120  provides LNG to the pump  106  which may desirably be configured as a low-volume, high-pressure pump. As pressurized LNG exits the pump  106 , depending on the fueling demands being placed on the fueling station  102 A, it may flow through an LNG flow path  126  or a CNG flow path  128 . 
   If a demand for LNG is initiated, the pressurized LNG flows from the pump  106 , through a mixer  130 , the function of which shall be discussed in more detail below, through a flow meter  132  and may be dispensed from an LNG dispensing nozzle  108  to a vehicle tank  134 . A circulation line  136  (recirculation line) may circulate unused or excess LNG back to the storage tank  104  from the LNG flow path  126 . 
   A bypass line  138  may be provided to enable the diversion of a volume of LNG from the feed line  120  around the pump  106  and into the LNG flow path  126  such as, for example, during start up of the pump at the initiation of a demand for LNG at the LNG dispensing nozzle  108 . A check valve  140  may be placed in the bypass line  138  to prevent any pressurized LNG which may be present in the LNG flow path  126 , such as from the pump  106  after start-up thereof, from flowing back to the storage tank  104  through the feed line  120 . 
   If a demand for CNG is initiated, pressurized LNG flows from the pump  106  through the CNG flow path  128 . The CNG flow path  128  includes a vaporizer  110  which transfers thermal energy to the natural gas so as to produce CNG from the pressurized LNG. CNG exits the vaporizer  110  and passes through a mixer  142 , the function of which shall be described in more detail below, through a meter  144  and is dispensed to a CNG vehicle tank  146  through the CNG dispensing nozzle  112 . While, if desired, the CNG produced from the LNG may be placed in an adequately rated pressure vessel  148  and stored for future dispensing into a CNG vehicle tank  146 , an advantage of the present invention is that intermediate storage of CNG is not required for the fueling of CNG vehicles. Rather, the CNG may be produced and dispensed on-demand from the LNG supply. In other words, the CNG may flow substantially directly from the vaporizer  110  to the CNG outlet  112  and/or associated CNG dispensing unit. It is to be understood that “substantially directly” allows for a diversion of some of the CNG flowing from the vaporizer  110  as well as the introduction of one or more additives to the CNG flowing from the vaporizer  110 . Rather, the term “substantially directly” indicates that intermediate storage is not required or utilized between the production of the CNG by the vaporizer  110  and the dispensing thereof to a vehicle&#39;s fuel tank. 
   Referring now to  FIG. 5 , a process flow diagram is shown of a fueling station  102 A in greater detail. In describing the fueling station  102 A depicted in  FIGS. 1 and 3 , various exemplary components may be set forth for use in conjunction with an exemplary embodiment of the fueling station  102 A. However, as will be appreciated by those of ordinary skill in the art, other suitable components may be utilized and the scope of the present invention is in no way limited to the specific exemplary components set forth in describing the present embodiment. 
   As indicated above, LNG is provided from a storage tank  104  (not shown in  FIG. 3 ) through a feed line  120 . A shutoff valve  160  is positioned in the feed line to control the flow of LNG between the storage tank  104  and the fueling station  102 A. In one embodiment, an exemplary shut off valve may include a normally closed 2″ ball valve with a solenoid or similar actuator and rated for service at approximately 300 psia and −240° F. Other components may be coupled to the feed line  120  for monitoring various characteristics of the LNG as it passes therethrough. For example, a pressure transducer  162  and a temperature sensor  164  may be coupled to the feed line in order to monitor the pressure and temperature of the incoming LNG. Similarly, a flow meter (not shown) may be coupled to feed line  102  for determining the rate of flow of the LNG entering the fueling station  102 A and/or for determining the cumulative volume of LNG entering the fueling station  102 A during a given period of time. A strainer  166  may also be coupled to the feed line  120  so as to ensure the quality of the LNG which is being processed by the fueling station  102 A. 
   The feedline  120  may be diverted into one of two bypass lines  138 A and  138 B (as there are two independent LNG dispensing nozzles  108 A and  108 B in the presently described embodiment shown in  FIG. 3 ) such as during a start-up phase of the fueling station  102 A as will be discussed in further detail below. The feed line  120  also provides LNG to the pump  106  through a branching of three different supply lines  168 A,  168 B and  168 C. The pump  106 , as shown in  FIG. 3 , may include a high pressure, low volume triplex-type pump configured to pump, for example, approximately twenty-four (24) gallons per minute (gpm) (8 gpm×3 pistons) at a pressure of approximately 5,000 psia. Such a pump is commercially available from CS&amp;P Cryogenics located in Houston, Tex. 
   Each of the supply lines  168 A- 168 C is configured to supply an individual one of the three pistons  170 A- 170 C of the triplex-type pump  106 . Similarly, each of the pistons  170 A- 170 C pumps pressurized LNG into an associated pressure line  172 A- 172 C. Additionally, individual vent lines  174 A- 174 C are coupled with each piston  170 A- 170 C and provide a flow path  176  back to the tank  104  (not shown) through appropriate valving and piping. The pump may also include a pressure relief valve  175  to prevent over pressurization and potential failure of the pump  106 . 
   The pressure lines  172 A- 172 C provide pressurized LNG to either or both of the LNG flow paths  126 A and  126 B, to the CNG flow path  128 , to all of the aforementioned paths simultaneously, or to any combination thereof through the appropriate control of various valves and flow control mechanisms as set forth below. Considering first the LNG side of the fueling station, pressurized LNG may flow through diverter valves  178 A- 178 C, each of which in the exemplary embodiment may include a normally open ¾″ control valve rated for service at approximately 5,000 psia and at −240° F. The pressurized LNG passes through any combination of the diverter valves  178 A- 178 C depending on demand. Due to lack of back pressure the pressurized LNG may experience a drop in pressure to, for example, approximately 300 psia as it passes through the diverter valves  178 A- 178 C. 
   It is noted that the pump  106  need not produce an elevated pressure (e.g., 5,000 psia) but, rather, may provide pressurized LNG at the pressure needed to deliver LNG to a vehicle&#39;s tank. Thus, for example, the pump  106  may produce pressurized LNG at a pressure of, for example, approximately 300 psia which, thus does not necessarily experience a reduction in pressure as it passes through the diverter valves  178 A- 178 C. However, the pump  106  may still build up the pressure of any LNG diverted to the vaporizer  110  to a desired pressure (e.g., 5,000 psia) while providing LNG at a “reduced” pressure (as compared to that diverted to the vaporizer  110 ) to the LNG flow paths  126 A and  126 B. 
   In one exemplary scenario, the pump  106  may be producing LNG through the pressurized output lines  172 A- 172 C at a pressure of approximately 300 psia. If, for example, diverter valves  178 A and  178 B are open and diverter valve  178 C is closed, LNG flows through diverter valves  178 A and  178 B to the LNG flow paths  126 A and  126 B at a pressure of approximately 300 psia while LNG is diverted by diverter valve  178 C to the vaporizer and builds to a desired pressure (e.g., 5,000 psia). In such a scenario, energy is conserved by pumping LNG at the pressure which is required to dispense LNG to a vehicle&#39;s tank, while independently building pressure of diverted LNG to a required pressure for the conversion of the LNG to CNG in the vaporizer  110 . 
   Returning to LNG side of the fueling station  102 A, any LNG exiting the diverter valves  178 A- 178 C is then directed through either, or both, of LNG control valves  180 A and  180 B. LNG control valve  180 A controls the supply of LNG through the first LNG flow path  126 A while LNG control valve  180 B controls the supply of LNG through the second LNG flow path  126 B. Thus, through proper actuation of the LNG control valves  180 A and  180 B, the LNG may be directed to flow through a specified one of the LNG flow paths  126 A and  126 B or to both simultaneously. Exemplary LNG control valves  180 A and  180 B may include a normally closed 1″ on/off control valve rated for service at approximately 300 psia and at −240° F. Such control valves  180 A and  180 B may also function as diverter valves depending, for example, on the operational configuration of the fueling station  102 A. 
   As the LNG flow paths  126 A and  126 B are substantially similar, only one of the flow paths  126 A is described in further detail for sake of convenience and simplicity in description and illustration. LNG flowing from the control valve  180 A may be mixed with a defined volume of CNG from diverted CNG line  182 A to control the temperature of the LNG flowing through the LNG flow path  126 A. The warmed LNG then flows through a mass flow meter  184 A, through another control valve  186 A which may be configured similar to LNG control valves  180 A and  180 B, and finally through LNG dispensing nozzle  108 A to a vehicle&#39;s LNG tank  134  (see  FIG. 2 ). An exemplary dispensing nozzle  108 A may include a 1″ break away nozzle assembly  192 A rated for service at approximately −240° F. 
   Sensors, such as a temperature sensor  188 A and a pressure transducer  190 A, may be placed in the LNG flow path close to the dispensing nozzle  108 A to monitor the characteristics of LNG being dispensed and to assist in controlling the production of an dispensing of LNG. For example, the temperature of LNG within the LNG flow path  126 A may be monitored to assist in controlling the flow rate of any CNG injected thereinto by way of CNG warming line  182 A. 
   The LNG flow path may also include a pressure relief valve  194 A so as to maintain the pressure in the LNG flow path  126 A at or below a defined pressure level. An exemplary pressure relief valve may include a 1″ pressure relief valve rated for service at approximately 300 psia and at −240° F. 
   A user interface and display unit  196 A may be operatively coupled with the fueling station  102 A such that a user may initiate demand of LNG through LNG dispensing nozzle  108 A and to monitor the progress of fueling activities. Another user interface and display unit  196 B may be associated with the dispensing of fuel from the LNG dispensing nozzle  108 B. Similarly, while not specifically shown in  FIG. 3 , a user interface and display unit may be associated CNG dispensing nozzles  112  (see  FIGS. 1 and 2 ). 
   Referring back to LNG flow path  126 A, a circulation line  136 A may be used to circulate excess LNG back to the tank  104  (see  FIGS. 4 and 5 ) as may be required during the fueling process such as when a vehicle&#39;s LNG tank is filled to capacity or when a user otherwise terminates the fueling of a vehicle. Also, inlet receptacles  200 A and  200 B (see also  FIG. 3 ) are provided, for example, for coupling with a vehicle&#39;s LNG tank during fueling. The receptacles  200 A and  200 B are coupled with the recirculation lines  198 A and  198 B to provide a flow path back to the storage tank  104  (see  FIGS. 1 and 2 ) from a vehicle&#39;s tank or tanks as will be appreciated by those of ordinary skill in the art. Such receptacles  200 A and  200 B may also be coupled with the dispensing nozzles  108 A and  108 B during periods when vehicles are not being refueled. Such coupling of the dispensing nozzles  108 A and  108 B with the inlet receptacles  200 A and  200 B may provide for recirculation of LNG and, thus, cool various components of the fueling station  102 A as well as the LNG flowing through such components. 
   It is noted that the fueling station may be configured to utilized one of various techniques. For example, when not dispensing LNG fuel to a vehicle&#39;s tank, the pump  106  may continue produce a pressurized output and the output may be circulated through the LNG flow paths  126 A and  126 B such as described above herein. Either or both of the LNG dispensing units  108 A and  108 B may be coupled with an associated inlet receptacle  200 A and  200 B to circulate LNG through the associated recirculation lines  198 A and  198 B and, ultimately, back to the tank  104 . Since substantially continuous circulation of LNG through the dispensing units  108 A and  108 B and associated inlet receptacles  200 A and  200 B may cause the LNG nozzles  192 A and  192 B to freeze up after a period of time, control valves  186 A and  186 B may be used to stop flow through the dispensing units  108 A and  108 B and circulate the LNG back through circulation lines  136 A and  136 B respectively. 
   It is additionally noted that, the fueling station  102 A may be configured for passive cooling, meaning that the pump  106  need not be operated to in order to circulate LNG through the LNG flow paths  126 A and  126 B. For example, the elevation head of the LNG supply (e.g., within the LNG tank  104 ) may be sufficient to cause LNG to flow through the supply lines  168 A- 168 C and through a bypass associated with each piston  170 A- 170 C of the pump  106 . Any LNG flowing through the bypass of the pump  106  would then flow through the LNG paths  126 A and  126 B and subsequently circulate, for example, through circulation lines  136 A and  136 B back to the tank. Thus, the present invention may take advantage of the head of the LNG supply to render passive cooling to the various component of the fueling station  102 A without the need to expend energy in the operation of the pump  106 . 
   Still referring to  FIG. 5 , sensors, such as, for example, temperature sensors  202 A and  202 B, for determining characteristics of the incoming or recirculated LNG may also be provided in association with the inlet receptacles  200 A and  200 B as may be desired. Additionally, check valves  204 A and  204 B may be provided to ensure that LNG already present in the circulation lines  136 A and  36 B does not inadvertently flow backwards into a vehicle&#39;s LNG tank or tanks. 
   It is noted that the configuration of the fueling station  102 A and, more particularly, the LNG flow path, enables LNG to be provided at a vehicle&#39;s LNG tank at a relatively high pressure of up to, for example, approximately 300 psia and at a relatively cold temperature of, for example, −240° F. Significantly, this enables the collapsing of an existing vapor head formed within a vehicle&#39;s LNG tank rather than requiring the purging of any vapor within the vehicle&#39;s LNG tank prior to introducing the LNG therein. 
   Referring back to the bypass lines  138 A and  138 B, LNG provided from the storage tank  104  (see  FIGS. 1 and 4 ) is allowed to enter the LNG flow paths  126 A and  126 B providing what may be termed flood fuel at the start up of a fueling station  102 A. The flood fuel ensures that LNG, rather than gas or vapor, is present in the LNG flow paths  126 A and  126 B prior to fuel being supplied by the pump at elevated pressures (e.g., 300 psia) which might otherwise result in surge bangs within piping which defines the LNG fuel paths  126 A and  126 B. 
   Still referring to  FIG. 5 , the CNG side of the fueling station is now considered. Starting at pressure lines  172 A- 172 C as they exit the pump  106 , if any or all of the LNG control valves  178 A- 178 C are in the closed position (or at least partially closed), at least a portion of the pressurized LNG will flow into the CNG flow path  128 . For example, if control valve  178 C is in a closed position, the LNG associated with pressure line  172 C will flow to the vaporizer  110  as indicated by LNG diversion line  208 . Thus, pressurized LNG (e.g., approximately 5,000 psia) may be introduced into the vaporizer  110  which transfers thermal energy to the LNG for the conversion of LNG into CNG. An exemplary vaporizer  110  may include an ambient forced air vaporizer  110  having the capacity to admit LNG at a flow rate of up to 24 gpm, at a pressure of approximately 5,000 psia and at a temperature of approximately −240° F. The vaporizer  110  may be configured to convert the LNG to CNG which exits therefrom at a relatively elevated temperature of, for example, approximately ±10° F. of the ambient temperature, at pressure of up to approximately 5,000 psia and at a flow rate of up to approximately 1,600 standard cubic feet per minute (scfm). Such an exemplary vaporizer is commercially available from Thermax Incorporated of Dartmouth, Mass. It is noted that such values of temperature, pressure and volumetric flow rater are exemplary and that the may be scaled up or down depending, for example, on the size and capacity of the pump  106  and the configuration of the associated piping. 
   A small amount of LNG, which is supplied through an LNG cooling line  210 , may be mixed with CNG leaving the vaporizer  110  to lower the temperature thereof. In one embodiment, for example, as much as four (4) gpm may diverted through the cooling line  210  for mixture with the CNG to control the temperature thereof. Sensors, such as a temperature sensor  212  and/or a pressure transducer  214 , may be positioned in the CNG flow path  128  to monitor characteristics of the CNG flowing therethrough and to assist, for example, in controlling the amount of LNG being mixed with the CNG exiting the vaporizer. The amount of LNG being mixed with CNG may be controlled by a control valve  216  such as, for example, a ½″ normally closed control valve rated for service at approximately 5,000 psia. 
   As noted above, a portion of CNG may similarly be diverted to warm LNG prior to the dispensing thereof. In diverting a portion of CNG, a pilot controlled pressure regulating valve  218  may be used to reduce the pressure of the CNG prior to its mixing with LNG. An exemplary pressure regulating valve  218  may be configured to reduce the pressure of the CNG from approximately 5,000 psia to approximately 300 psia with a flow rate capacity of approximately 800 scfm. After a portion of CNG is directed through the pressure regulating valve  218 , the reduced pressure CNG may be split into two warming lines  182 A and  182 B for warming LNG in LNG flow paths  126 A and  126 B respectively. Control valves  220 A and  220 B may be used to distribute and otherwise control the flow of reduced pressure CNG to the warming lines  182 A and  182 B. Exemplary control valves may include a ¾″ normally closed proportional control valves rated for service at a pressure of approximately 300 psia and at a temperature of −240° F. 
   Various additives may be also introduced into, and mixed with, the CNG as it flows through the CNG flow path  128 . For example, upstream of the branch containing the pressure regulating control valve  218 , a source of odorant  222  may be coupled with the CNG flow path  128  to introduce and mix odorant therewith. The odorant may be added to the CNG to assist in the detection of any CNG which may leak from a vehicle&#39;s CNG tank, piping, engine or from some other storage vessel. 
   A source of lubricant  224  may also be coupled with the CNG flow path  128  to introduce and mix lubricant therewith. The lubricant may be added to the CNG for purposes of lubricating various motor vehicle components during processing and combustion of the gas. For example, the lubricant may be added to provide necessary lubrication of an injection device or similar fuel delivery system associated with a motor vehicle consuming and combusting CNG as will be appreciated by those of ordinary skill in the art. 
   The CNG flow path  128  carries CNG to a CNG dispensing unit  226  which may be coupled to a CNG outlet  112  and is configured for dispensing of the CNG fuel into a vehicle&#39;s CNG tank. The CNG dispensing unit  226  may include, for example, a 1000 or 5000 Series Dispenser or a 5000 Series Fleet Dispenser commercially available from ANGI Industrial LLC, of Milton, Wis. Such exemplary CNG dispensing units may include integrated filters, multiple dispensing hoses or nozzles, and have integrated controllers associated therewith. Such dispensers may be configured to accommodate a flow rate substantially equivalent to, or greater than, the output of the vaporizer  110 . 
   As discussed above, while not necessary with the present invention, CNG may also be dispensed to a storage facility  148  (see  FIG. 2 ) if so desired. While not shown in  FIG. 3 , a user interface and display may be operatively coupled with the fueling station  102 A so that a user may initiate requests and monitor the progress of the CNG fueling activities. 
   A vapor bleed line  228  is coupled to the CNG path  128  and is further coupled with a vapor return line  230 . The vapor return line  230  is configured to receive any vapor bled off from the CNG dispensing unit  226 , which may include vapor bled off a vehicle&#39;s CNG tank and fed back through the CNG dispensing unit. Vapor drawn off from these two lines  228  and  230  may be combined and through a pressure regulator  231  fed to a vapor management system which may include, for example, circulation back into the storage tank  104  ( FIGS. 1 and 4 ). An exemplary pressure reducing valve  231  may be configured to reduce the pressure of vapor from approximately 5,000 psia to approximately 25 psia. 
   Further examples of an appropriate vapor management system may include for example, metering the gas back into a residential grid, use of the gas as a fuel for on site heating needs, further compression of the gas for use as vehicle fuel, or simply venting of the gas to the atmosphere as allowed by applicable regulations. 
   As set forth above, LNG may be circulated back to the storage tank  104  (see  FIGS. 1 and 2 ) from various points along the LNG flow path  126 . Similarly, CNG may be circulated back to the tank  104  from the CNG flow path  128 . For example, CNG circulation line  232  may be configured to draw CNG from a location downstream of the pressure regulating control valve  218 , and prior to its mixture with LNG, to circulate the CNG back to the storage tank  104  (see  FIGS. 1  and  2 ) and, more particularly, into either the vapor containing volume  124  (see  FIG. 2 ), as indicated at line  234 A, or to the LNG containing volume  122  (see  FIG. 2 ), as indicated at line  234 B. Control valves  236 A and  236 B may be used to control the flow of CNG back to the storage tank  104 . Exemplary control valves may include a ¾″ normally closed ball valve rated for service at approximately 300 psia and at a flow rate of approximately 720 scfm. 
   While the example set forth in  FIG. 5  illustrates a multiplexing arrangement which utilizes a multiplex pump  106  and diverter valves  178 A- 178 C associated with the individual pistons of the pump  106 , other multiplexing arrangements may also be utilized. Such multiplexing arrangements may include, for example, those shown in  FIGS. 6A through 6E . 
   Referring first to  FIG. 6A , a single piston pump  106 ′ (or possibly an individual piston of a multiplex pump) may be coupled to an associated supply line  168 ′ and vent line  174 ′ in a manner similar to that described above. The pressure line  172 ′ fed by the pump  106 ′ may branch into a plurality of individual pressure lines  172 A′- 172 C′ each being associated with diverter valves  178 A- 178 C. The diverter valves  178 A- 178 C may then selectively direct the pressurized LNG to the vaporizer  110  or to the LNG flow path  126  in a manner consistent with that described and set forth with respect to  FIG. 5 . 
   Referring to  FIG. 6B , a single piston pump  106 ′ is coupled to an associated supply line  168 ′, pressure line  172 ′ and vent line  174 ′ in a manner similar to that which has previously been described herein. The pressure line  172 ′ may be coupled to a proportional directional diverter valve  178 ′ which proportionally diverts the pressurized LNG between the vaporizer  110  and the LNG flow path  126  (see  FIG. 5 ) in a controlled manner. In other words, the proportional directional diverter valve  178 ′ may incrementally control the flow of the pressurized LNG between the vaporizer  110  ( FIG. 5 ) and the LNG flow path  126  ( FIG. 5 ) such that all of the pressurized LNG may flow in either direction, or any desired combination of flow (e.g., 70% in one direction and 30% in the other direction) may be achieved. 
   Referring to  FIG. 6C , each piston  170 A- 170 C of a multiplex pump  106  is coupled to a corresponding supply line  168 A- 168 C, pressure line  172 A- 172 C and vent line  174 A- 174 C, respectively, such as set forth with respect to  FIG. 5  above herein. Each individual pressure line  172 A- 172 C is independently coupled with an associated proportional directional diverter valve  178 A′- 178 C′ respectively. Thus, the diverter valves  178 A′- 178 C′ each individually control the flow of pressurized LNG from their respective pistons  170 A- 170 C between the vaporizer  110  and the LNG flow path  126  in a manner consistent with that described and set forth with respect to  FIG. 5 . 
   Referring to  FIG. 6D , a single piston pump  106 ′ is coupled to an associated supply line  168 ′, pressure line  172 ′ and vent line  174 ′ such as previously described herein. The pressure line  172 ′ may be may be split such that a first branch  260  flows to a first proportional control valve  262  and a second branch  264  flows to a second proportional control valve  266 . The first and second proportional control valves  262  and  266  in combination control flow of pressurized LNG from the pressure line  172 ′ to the vaporizer  110  and the LNG flow path in a manner consistent with that described and set forth with respect to  FIG. 5 . 
   Referring now to  FIG. 6E , each piston  170 A- 170 C of a multiplex pump  106  is coupled to a corresponding supply line  168 A- 168 C, pressure line  172 A- 172 C and vent line  174 A- 174 C, respectively, such as set forth with respect to  FIG. 5  above herein. The individual pressure lines  172 A- 172 C are combined into a common pressure line  270  which feeds into a proportional directional diverter valve  178 ′. The proportional diverter valve  178 ′ diverts the pressurized LNG between the vaporizer  110  and the LNG flow path  126  (see  FIG. 5 ) in a controlled manner such as described above herein. 
   With any of the above exemplary embodiments, the flow of the pressurized LNG is multiplexed in the sense that it is capable of being diverted between the vaporizer  110  (and associated CNG flow path  128 ) and the LNG flow path  126  including the ability to divert substantially all of the pressurized LNG to either destination, as well as the ability to fractionally divide the flow of the pressurized LNG between the two destinations in substantially any desired combination (e.g., 70% vaporizer/30% LNG flow path; 40% vaporizer/60% LNG flow path; etc.). 
   The configuration of the exemplary fueling station  102 A as illustrated in  FIGS. 1 through 6E  offers various advantages over conventional prior art fueling stations and, further, provides considerable flexibility in the dispensing of LNG, CNG or both depending upon instant demand from a user. For example, the use of multiplexing, whether effected by a multiplex pump or through the appropriate configuration of valves and piping, enables the fueling station to provide substantially all of the output of pressurized LNG from the pump to either of the LNG flow paths  126 A and  126 B, to the CNG flow path  128 , or to divide the output of pressurized LNG among the various flow paths depending upon demand. If only LNG is desired, pressurized LNG may flow through pressure lines  172 A- 172 C, through diverter valves  178 A- 178 C, and into either or both LNG flow paths  126 A and  126 B as required by proper actuation of control valves  180 A and  180 B. 
   If the substantially simultaneous dispensing of both CNG and LNG is required, then a portion of the pressurized LNG is diverted through LNG diversion line  208 . For example, one or more diverter valves  178 A- 178 C may be closed, or partially closed, to cause pressurized LNG to flow through LNG diversion line  208  rather than to the control valves  180 A and  180 B and the corresponding LNG flow paths  126 A and  126 B. The pressurized LNG may then pass through the vaporizer  110  for production of CNG as set forth above herein. 
   If only CNG is desired, substantially all of the pressurized LNG may be diverted through LNG diversion line  208  by appropriate actuation of diverter valves  178 A- 178 C to produce a greater volume of CNG. It is noted, that the phrase “substantially all” is used above in discussing the flow of pressurized LNG when the dispensing of either only LNG or only CNG is desired. It is to be understood that the use of the term “substantially all” recognizes that a small amount of pressurized LNG may be diverted off for purposes of temperature control. For example, if only the dispensing of LNG is required, a small volume of pressurized LNG may be diverted through the vaporizer  110  to be injected into, and mixed with, the LNG through CNG warming lines  182 A and  182 B if so required. 
   The fueling station  102 A of the present invention further enables the dispensing of natural gas fuel in a thermally and cost efficient manner. For example, the integrated dispensing of LNG and CNG maintains the LNG in a relatively cold state and helps to avoid cool down runs as required in conventional fueling stations wherein cold LNG must be circulated through the system for a period of time in order to cool down the various components prior to dispensing the fuel into a vehicle&#39;s tank. Moreover, such a configuration provides passive cooling with an open supply of LNG through the pump  106  which may be circulated back to the tank  104  ( FIGS. 1 and 2 ). Such a configuration enables effectual instant, or on-demand, delivery of fuel. 
   Additionally, it has been estimated that the production and dispensing of CNG in accordance with the present invention provides as much as 20 to 1 savings as compared to the conventional production, transportation, storage and ultimate dispensing of CNG to motor vehicles for combustion thereby. 
   While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.