Abstract:
A dispenser nitrogen purge and heater system for a liquid natural gas (LNG) fueling dispenser, comprising a nitrogen purge enclosure; a nitrogen container containing nitrogen; a nitrogen feed line for feeding nitrogen from the nitrogen container to the nitrogen purge enclosure; a heater for heating an interior space within the enclosure; and a fan assembly for circulating the nitrogen within the interior space

Description:
FIELD OF THE INVENTION 
       [0001]    The invention broadly relates to a dispenser nitrogen purge and heater system for a liquid natural gas (LNG) fueling dispenser. 
       BACKGROUND OF THE INVENTION 
       [0002]    In certain cold and humid regions such as Canada and parts of the United States, LNG fuel dispensers can experience ice and/or frost build-up issues. The ice tends to build up on the process piping of the fuel dispenser in a fashion that limits maintenance access and dispenser operation. As a further complication, the ice cannot be melted without potentially irreparably damaging the dispenser electronics disposed below the melting ice. 
         [0003]    There currently exists several unsatisfactory solutions to this ice build-up on LNG fuel dispensers located in cold and humid regions. One such solution involves ceasing use of the dispenser to allow it to thaw out. However, this solution is extremely inefficient and can take an indefinite amount of time. Another solution involves spraying water continuously on the piping until the ice was melted. However, this solution can damage the dispenser electronics located below the piping. 
       SUMMARY OF THE INVENTION 
       [0004]    Certain embodiments of the present invention are directed toward a dispenser nitrogen purge and heater system for a liquid natural gas (LNG) fueling dispenser. The system addresses the above-identified issues associated with ice build-up on LNG fuel dispensers, particularly in cold and humid regions. Specifically, the system prevents ice from forming on the process piping in the dispenser enclosure, thereby permitting maintenance access and allowing full dispenser operation. 
         [0005]    The nitrogen purge and heater system embodiments described herein are directed toward providing preventative maintenance for LNG fueling dispensers. By way of example, the system: (i) protects against water damage to electronics, (ii) allows service access to dispenser components, and (iii) eliminates frost from generating on the exterior of the process piping purge enclosure. 
         [0006]    One embodiment of the invention is directed toward a dispenser nitrogen purge and heater system for a liquid natural gas (LNG) fueling dispenser, comprising a nitrogen purge enclosure; a nitrogen container containing nitrogen; a nitrogen feed line for feeding nitrogen from the nitrogen container to the nitrogen purge enclosure; a heater for heating an interior space within the enclosure; and a fan assembly for circulating the nitrogen within the interior space. The nitrogen purge enclosure can form a portion of the LNG dispenser. 
         [0007]    In operation, the heater maintains the interior space of the nitrogen purge enclosure at a temperature above freezing. In some embodiments, the heater is controlled to keep the temperature of the interior space within a desired temperature range. The fan assembly may comprise a fan attached to the nitrogen purge enclosure by way of a magnetic coupler. In certain embodiments, nitrogen is introduced through a nitrogen inlet of the enclosure at a rate of approximately 1 cubic feet per minute to ensure a positive purge pressure. In further embodiments, nitrogen is introduced into the enclosure at a rate of between 0.75 and 1.25 cubic feet per minute to ensure a positive purge pressure. The nitrogen purge and heater system inhibits ice and frost from generating in the interior space during operation of the LNG dispenser. In addition, the nitrogen purge and heater system eliminates frost from generating on an exterior of the nitrogen purge enclosure, and prevents frost from generating on process piping within the enclosure. The process piping can include piping insulation in the form of pipe wrap that is secured by custom fitting and VELCRO. 
         [0008]    In some embodiments, the nitrogen purge enclosure is formed of sheet metal that is sealed to minimize the nitrogen purge flow rate required to maintain a substantially moisture-free environment in the interior space. A top panel of the enclosure can be removable to allow maintenance access. The panel can be made of a suitable material such as poly(methyl methacrylate) (PMMA). In certain embodiments, the nitrogen purge enclosure is completely sealed such that it is substantially air tight. In further embodiments, the enclosure is sealed to an extent needed to minimize a nitrogen leak rate of the enclosure to allow a relatively low nitrogen container capacity. 
         [0009]    Other features and aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the invention. The summary is not intended to limit the scope of the invention, which is defined solely by the claims attached hereto. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a diagram illustrating a dispenser nitrogen purge and heater system in accordance with an embodiment of the invention. 
           [0011]      FIG. 2  is a front view of a LNG dispenser having ice build-up on the front face of the dispenser. 
           [0012]      FIG. 3  is a side view of a LNG dispenser having ice build-up on a side face of the dispenser. 
           [0013]      FIG. 4  is a perspective view showing ice build-up on process piping within the dispenser. 
           [0014]      FIG. 5  is a perspective view showing ice build-up on dispenser valves of the dispenser. 
           [0015]      FIG. 6  is a perspective view of the outside of the dispenser, wherein an upper portion of the dispenser cabinet forms the nitrogen purge enclosure of  FIG. 1 . In other embodiments, the nitrogen purge enclosure can form a different portion of the dispenser cabinet such as a lower portion of the cabinet, or any other suitable area within the cabinet. 
           [0016]      FIG. 7  is a perspective view showing the inside of the nitrogen purge enclosure of  FIG. 1 , wherein the enclosure panels have been removed. 
           [0017]      FIG. 8  is a perspective view showing the fan and heater within the nitrogen purge enclosure of  FIG. 1 , wherein the enclosure panels have been removed. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In the following paragraphs, the present invention will be described in detail by way of example with reference to the attached drawings. Throughout this description, the preferred embodiment and examples shown should be considered as exemplars, rather than as limitations on the present invention. As used herein, the “present invention” refers to any one of the embodiments of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s). 
         [0019]      FIG. 1  is a diagram illustrating a dispenser nitrogen purge and heater system  100  for an LNG dispenser in accordance with an embodiment of the invention. The system  100  comprises nitrogen container  110 , nitrogen feed line  120  for feeding nitrogen to a nitrogen purge enclosure  125 , heater  130 , and fan assembly including fan  140  and fan motor  145 . The nitrogen purge enclosure  125  provides a large interior space  160  containing heater  130 , fan  140 , and process piping  155  of the LNG dispenser. Additionally, system  100  can include thermostat  150  or other means for regulating the temperature inside of the enclosure  125 . 
         [0020]    In operation, dispenser nitrogen purge and heater system  100  prevents ice from forming on the process piping  155  within nitrogen purge enclosure  125 , thus permitting maintenance access and allowing full dispenser operation. Without using a nitrogen purge, ice build-up can occur on process piping  155  when the LNG dispenser is in use. The build-up can be particularly severe in cold and humid climate regions. However, this problem is resolved by adding the nitrogen purge and heating system  100  described herein. In some embodiments, the nitrogen purge enclosure  125  is located at a top portion of the LNG dispenser. By way of example, the LNG dispenser can comprise an AK-1000 LNG Dispenser manufactured by NorthStar, Inc. The top portion of the dispenser forms the nitrogen purge enclosure  125 . 
         [0021]    With continued reference to  FIG. 1 , the heater  130  has an electrical classification that is suitable for its use. Heater  130  is employed to maintain the nitrogen purge enclosure  125  at a temperature above freezing. The heater  130  can be controlled using thermostat  150  to keep the temperature within enclosure  125  within a desired temperature range. In other embodiments, a temperature probe can be employed for regulating the heater  130 . The temperature probe may be governed by a programmable logic controller (PLC) of the dispenser, thereby allowing remote monitoring of the purge system, and providing advanced notice of failure issues such as fan stoppage, heater failure, nitrogen purge leaks, etc. The fan  140  circulates both the heat and the nitrogen throughout the interior space  160  of the nitrogen purge enclosure  125 . By way of example, the fan  140  can comprise a conventional fan that is 8-inches in diameter. In some embodiments, the fan assembly including fan  140  and fan motor  145  is attached to the nitrogen purge enclosure  125  by way of one or more magnetic couplers, thereby obviating the need to add an additional access hole to allow the fan  140  to operate in the enclosure  125 . 
         [0022]    Nitrogen is provided to the nitrogen purge enclosure  125  by way of the nitrogen container  110 . In some embodiments, the nitrogen container  110  comprises an on-site nitrogen generator. In other embodiments, the nitrogen container  110  comprises a nitrogen storage bottle. In certain embodiments, nitrogen is introduced into the enclosure  125  at a rate of 1 cubic feet per minute to ensure a positive purge pressure. In further embodiments, nitrogen is introduced into the enclosure  125  at a rate of between 0.75 and 1.25 cubic feet per minute to ensure a positive purge pressure. During operation of the LNG dispenser, the nitrogen purge inhibits ice and frost from generating. Without the nitrogen purge, this ice and frost would have to be melted, which can then drip onto the dispenser electronics located underneath the process piping  155 . By inhibiting ice generation, the nitrogen purge protects against water damage to the dispenser electronics. In addition, the nitrogen purge eliminates frost from generating on the exterior of the nitrogen purge enclosure  125 . 
         [0023]    In some embodiments, the nitrogen purge enclosure  125  is formed of sheet metal that is sealed to minimize the nitrogen purge flow rate required to maintain a substantially moisture-free environment. The top panel  170  of the enclosure can be removable for maintenance access. In certain embodiments, the nitrogen purge enclosure  125  is substantially completely sealed. In further embodiments, the enclosure  125  is not completely sealed, but is sealed to the extent needed to minimize the leak rate to permit a relatively low nitrogen generator capacity. The process piping  155  can include piping insulation  180  such as pipe wrap that is secured by custom fitting and VELCRO. Piping insulation  180  helps keep the heat transfer to the LNG product at a minimum level. 
         [0024]      FIG. 2  is a front view of a LNG dispenser  200  having ice build-up  205  on the front face  210  of the dispenser. This ice build-up can be caused by operation of the system in cold and humid environments. According to embodiments of the invention, the LNG dispenser  200  can be formed with, or retrofitted to include, the nitrogen purge and heater system  100  of  FIG. 1  in order to prevent the ice build-up shown in  FIG. 2 . 
         [0025]      FIG. 3  is a side view of the LNG dispenser  200  of  FIG. 2  showing ice build-up  205  on a side face  220  of the dispenser  200 . 
         [0026]      FIG. 4  is a perspective view showing ice build-up  205  on process piping  230  within the LNG dispenser  200  of  FIG. 2 . 
         [0027]      FIG. 5  is a perspective view showing ice build-up on dispenser valves  240  of the LNG dispenser  200  of  FIG. 1 . 
         [0028]      FIG. 6  is a perspective view of the outside of an LNG dispenser  600  having a nitrogen purge enclosure  125  housing the nitrogen purge and heater system  100  illustrated in  FIG. 1 . In the illustrated embodiment, the LNG dispenser  600  comprises a large cabinet, wherein an upper portion of the dispenser cabinet forms the nitrogen purge enclosure  125 . In other embodiments, the nitrogen purge enclosure can form a different portion of the dispenser cabinet such as a lower portion of the cabinet, or any other suitable area within the cabinet. In some configurations, the LNG dispenser  600  is formed with the nitrogen purge and heater system  100  of  FIG. 1  in order to prevent the ice build-up shown in  FIGS. 2-5 . In other embodiments, the LNG dispenser  600  is retrofitted to include the nitrogen purge and heater system  100  of  FIG. 1  in order to prevent the ice build-up shown in  FIGS. 2-5 . 
         [0029]      FIGS. 7 and 8  are perspective view showing the inside  160  of the nitrogen purge enclosure  125  of  FIG. 1 , wherein the enclosure panels have been removed. In particular, the fan  140  is disposed at the bottom panel  610  of the enclosure  125 , and the heater  130  is disposed near the left panel  620  of the enclosure  125 . The inlet  630  of the nitrogen feed line  120  is formed in a lower portion of the left panel  620  adjacent to the bottom panel  610 . 
         [0030]    One skilled in the art will appreciate that the present invention can be practiced by other than the various embodiments and preferred embodiments, which are presented in this description for purposes of illustration and not of limitation, and the present invention is limited only by the claims that follow. It is noted that equivalents for the particular embodiments discussed in this description may practice the invention as well. 
         [0031]    While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the invention, which is done to aid in understanding the features and functionality that may be included in the invention. The invention is not restricted to the illustrated example architectures or configurations, but the desired features may be implemented using a variety of alternative architectures and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical partitioning and configurations may be implemented to implement the desired features of the present invention. Also, a multitude of different constituent module names other than those depicted herein may be applied to the various partitions. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise. 
         [0032]    Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead may be applied, alone or in various combinations, to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments. 
         [0033]    Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future. 
         [0034]    A group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although items, elements or components of the invention may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated. 
         [0035]    The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, may be combined in a single package or separately maintained and may further be distributed across multiple locations. 
         [0036]    Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives may be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.