Abstract:
A system for producing pressurized gas(es) from polar molecular liquids without the need to compress the gas(es) through outside Systems and methods for efficiently converting liquid natural gas (LNG) to compressed natural gas (CNG) and to low pressure natural gas (NG). The system efficiently modifies and controls the parameters of volume, pressure, and temperature in converting liquid natural gas (LNG) to compressed natural gas (CNG) and eventually to low pressure natural gas (NG) for the purpose of storing and dispensing the same for use in a variety of commercial, industrial, and in particular, residential applications.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to systems for efficiently converting liquid natural gas (LNG) to compressed natural gas (CNG), also known as pressurized natural gas (PNG), and further to low pressure natural gas (NG). The present invention relates more specifically to a system for efficiently modifying and controlling the parameters of volume, pressure, and temperature in converting liquid natural gas (LNG) to compressed natural gas (CNG) and eventually to low pressure natural gas (NG) for the purpose of storing and dispensing of each of the same for use in residential applications, as well as in a variety of commercial and industrial applications. 
         [0003]    2. Description of the Related Art 
         [0004]    Many efforts have been made in the past to efficiently store and convert liquid natural gas (LNG) to compressed natural gas (CNG) and then to dispense it as low pressure natural gas (NG). Most of these efforts suffer from significant losses and dependence on distributed heat energy during the processes of compressing and/or de-compressing the systems within which the quantities of natural gas, at various temperatures, pressures, and volumes, are maintained and transferred. Although the use of natural gas in industry, commercial manufacturing, and residential applications has and is continuing to increase, the ability to store, transport, and convert the low volume high quantity forms of natural gas has lagged behind the demand for natural gas in a variety of applications, particularly home fueling. Such storage, transportation, and conversion problems have become especially acute in the smaller residential applications associated with the use of natural gas. The ability to efficiently store, transport, and convert natural gas (typically in the form of CNG or LNG) has inhibited the ongoing growth of the natural gas industry for use in residential applications. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a LNG to CNG conversion system with an optional NG supply and backup system, and an optional method for adding hydrogen gas to enhance the NG and CNG. The invention takes in LNG and by controlled warming converts it to vapor CNG, having the additional room to expand into but still contained within a small enough volume to result in an ideal fueling vapor pressure of CNG such as 3,000-3,600 psi. The warming conversion can occur as the result of thermal transfer using ambient temperature and lapse of time. The oval shape of the converter of one of the exemplary embodiments encourages movement of air and further enhances uniform thermal transfer. 
         [0006]    Warming can also occur by using one of many types of heat sinks Natural gas within the system may be used for combustion to warm the thermal heat sink. Outside heat sources such as exhaust stacks or direct solar may also be used. The shape of the expansion chamber allows the thermal evolution of the heating of the LNG without resulting in dead end pockets of cold or hot gasses. The oval shape causes efficient heating and stage transference and enhanced thermal gas movement, as can be observed by thermal imaging. Optionally, if desired, the gas movement may be mechanically, electrically, or otherwise enhanced resulting in quicker and/or more consistent system-wide warming resulting in less thermal shock to equipment. The stack shape of the preferred embodiment is less expensive to construct and provides greater separation of the lower density gas production. 
         [0007]    The function of the internal conduit in the present system is to isolate, in a practical cost efficient manner, the LNG, but not the CNG, from the outside pipe and allow the LNG to vaporize without touching the outside of the pipe, lessening metal stress that could occur from a localized cold spot on an otherwise non-stressed temperature vessel exterior, which could result in system life shortening metal fatigue or premature failure. To this end, a drip containment system and method shown as a partial pipe in the cross section to promote against such events occurring. 
         [0008]    The system of the present invention will be used in a primary way to fuel natural gas (primarily methane) transportation vehicles such as cars, trucks, carts, lifts, cycles, etc. The present invention&#39;s CNG component can also be used as a feed stock for hydrogen production. The fuel made ready for use by the system of the present invention is superior to fuel supplied by non-LNG “natural gas” or mixed LNG sources and natural gas together, because it will be chemically more homogenous. Water is removed. Liquid distillates, such as butane, ethane, and propane, which can settle out of methane vapor (CH 4 ) in excess proportions are removed in the production of LNG when they freeze or separate, and as a result, these impurities are prevalent in the system&#39;s fuel production in known proportions. As opposed to other home fueling equipment, the fuel supplied by the system of the present invention is superior because it will not begin as residential NG chemically altered with sulphur or other chemicals, or contain water which can foul hydrogen fuel cells or leave unwanted deposits in internal combustion engines. The methane fuel supplied by the system of the present invention can easily be additionally enhanced by the addition of hydrogen gas to the expansion chamber to supplement those hydrocarbon molecules which have ability to take on additional hydrogen atoms, making it superior fuel compared to non-hydrogen additive systems, but being cleaner as well as providing more energy. 
         [0009]    The system of the present invention will be used as transportation compressed natural gas (CNG) or pressurized natural gas (PNG) fueling station. The system of the present invention will further be used as a natural gas supply (NG) such as for a residence. The system of the present invention will be used as a reserve backup natural gas supply such as for a residence for purposes including emergency. The system of the present invention will be used as a supplemental natural gas supply point for a natural gas distribution system. The system of the present invention will be used as a point of sale of natural gas. The system of the present invention will be used for peak supply storage of natural gas. 
         [0010]    This invention is scalable to allow dimensional changes which result in different beneficially targeted volumes and pressures for increased usefulness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a partially schematic, partial cross-sectional, elevational view of the system of the present invention for converting LNG to CNG. 
           [0012]      FIG. 2  is a partially schematic, partial cross-sectional, top plan view of the system of the present invention shown in  FIG. 1 . 
           [0013]      FIG. 3  is a detailed cross-sectional view of the system of the present invention taken along cross-section lines A-A′ in  FIG. 2 . 
           [0014]      FIGS. 4A-4D  are detailed views of an LNG personal supply tank device of the present invention. 
           [0015]      FIGS. 5A-5H  are schematic block diagrams showing a variety of applications of the LNG to CNG to NG system and methods of the present invention. 
           [0016]      FIGS. 6A-6G  are partially schematic block diagrams showing an elevational view of an alternate preferred embodiment of the present invention for converting LNG to CNG and identify the progression of steps implemented to carry out the process of the invention. 
           [0017]      FIG. 7  is a perspective view of a preferred embodiment of the phase change container structure of the present invention showing one implementation of a number of the structures shown generally in  FIGS. 6A-6G . 
       
    
    
     SUMMARY OF REFERENCED ELEMENTS 
       [0018]      
         [0000]    
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Ref. No. 
                 Description 
               
               
                   
               
             
             
               
                 301 
                 LNG fill portal for cryogenic like vessel. 
               
               
                 302 
                 Outer container for LNG. 
               
               
                 303 
                 Inner container for LNG approximate ratio being 1:2.4 by volume of expansion 
               
               
                   
                 chamber shown scaled at 40 gallons made of a high nickel content steel or 
               
               
                   
                 aluminum alloy. 
               
               
                 304 
                 Neck pipe, one way with valve connects LNG container to CNG expansion 
               
               
                   
                 chamber inner pipe valve must be dual specification of LNG temperature and 
               
               
                   
                 CNG pressure strength. 
               
               
                 305 
                 Inner oval pipe volume approximate ratio being 1:1 by volume to inner 
               
               
                   
                 container made of a high nickel content steel or aluminum alloy. 
               
               
                 306 
                 Oval pressure vessel expansion chamber, preferably duplex stainless steel. 
               
               
                 307 
                 Transfer holes to vent vaporizing LNG transforming to CNG into expansion 
               
               
                   
                 chamber in a uniform manner. 
               
               
                 308 
                 Safe vent before failure connected to expansion chamber. 
               
               
                 309 
                 Leak detect and alarm, ultrasonic preferred. 
               
               
                 310 
                 Swing arm dispensing tube. 
               
               
                 311 
                 CNG specific fill start/stop/auto stop. 
               
               
                 312 
                 CNG specific fill attachment. 
               
               
                 313 
                 Vent and stand pipe connected to expansion chamber. 
               
               
                 314 
                 Heat sink to air in heat transfer for the benefit of vaporization LNG. May be a 
               
               
                   
                 water bath, may be as cooling fins, or refrigeration coil. 
               
               
                 315 
                 Vertical and lateral support. 
               
               
                 316 
                 Heat exchange for heat sink such as available from exhaust stack or direct heat. 
               
               
                 317 
                 Optional hydrogen input to enhance CNG quality as available from electrolysis 
               
               
                   
                 at depth or other. 
               
               
                 318 
                 Optional supply NG from inner container. 
               
               
                 319 
                 Control and instrument panel LNG to CNG system. 
               
               
                 320 
                 Internal LNG drip pipe. 
               
               
                 321 
                 Pressure reducing valve for (318) and (322). 
               
               
                 322 
                 Optional supply NG from expansion chamber. 
               
               
                 323 
                 Chemical additives to natural gas to be used for residential fuels often use a 
               
               
                   
                 sulfur compound (enhancing leak detection). 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    The present invention provides an LNG to CNG to NG system and method. This system may be optionally enhanced by a system generating hydrogen gas such as an electrolysis at pressure and/or at depth system. The system may also be optionally enhanced by a steam and methane reformation system, including as a heat exchange mechanism described. In the system of  FIGS. 1 &amp; 2 , an oval CNG expansion chamber 2.4 times the size of the LNG cryogenic container is provided with center tube circles vented. High nickel alloy steel and some aluminum alloys are preferably used in the construction of this system where there is contact with cryogenic liquids. The system further includes passive and active heat sinks The system includes LNG fill portal  301  for the cryogenic like vessel. Also disclosed are outer container  302  and inner container  303  for the LNG. Again, the approximate ratio of the container volume being 1:2.4 to the volume of oval pressure vessel expansion chamber  306 . 
         [0020]    Neck pipe  304  provides a one way flow with valve that connects the LNG container to the CNG expansion chamber inner pipe Inner oval pipe  305  has a volume in the approximate ratio of 1:1 with inner container  303 . Oval pressure vessel expansion chamber  306  is preferably made of duplex stainless steel. Transfer holes  307  are provided to vent vaporizing LNG into oval pressure vessel expansion chamber  306  in a uniform manner. A safe vent valve  308  is provided before oval pressure vessel expansion chamber  306 . A leak detection and alarm device  309  is also provided, with an ultrasonic type device preferred. 
         [0021]    Swing arm dispensing tube  310  extends to provide the manner of dispensing the CNG. A CNG specific fill valve  311  provides start, stop, and auto stop for the flow. A CNG specific fill attachment  312  is also provided. Vent and stand pipe  313  is connected to oval pressure vessel expansion chamber  306 . Heat sink  314  to air is provided for heat transfer for the vaporization of the LNG. Vertical and lateral supports  315  are shown for the structural support of the system. Heat exchange  316  is shown such as is available from the exhaust stack in the steam and NG reformation system described above. Hydrogen input  317  is further provided to enhance CNG quality and is available from an electrolysis at depth system mentioned above, or an electrolysis at pressure system. Optional natural gas (NG) supply  318  is provided to enhance CNG quality as is also available from a steam and NG reformation system as mentioned above. Control and instrument panel  319  is provided to monitor CNG volume, pressure, and temperature in the system, as well as to show time, elapsed time, and to indicate a percentage to add hydrogen. 
         [0022]    Reference is made to  FIG. 3  which is a cross-section view of taken along section line A-A′ in  FIG. 2 . Oval pressure vessel expansion chamber  306  is shown surrounding inner oval pipe  305 . Below and within expansion chamber  306  is internal LNG drip pipe  320 . Collectively,  FIGS. 1-3  demonstrate the method of the present invention by reference to the details of the system designed to carry out the method at ambient parameters. 
         [0023]      FIGS. 4A-4D  provide detailed views of an LNG personal supply tank component of the system of the present invention. Portable LNG tanks without wheels (less than 7 gallons liquid or weighing about 50 lbs.) and portable LNG tanks with wheels (carrying about 25 gallons) may become an integral part of delivery, fueling the phase change and adjusting system of the present LNG to CNG to NG system. This personal LNG tank  330  would preferably be a high pressure bottle  334  (or  340  or  342 ) surrounded by insulation  332  (or  338 ). Appropriate valves  336  and fill/dispense attachments  344  would be utilized. Such an element may be a standalone liquid container for other LNG devices as well. 
         [0024]    The feasible elements do exist for this new component of the system. These may be characterized as liquid individual natural gas (LiNG) devices and pressurized liquid individual natural gas (PLiNG) devices. This accessory would be a cryogenic container with an LNG specific input port and output port. It would be constructed with at least one container within a container and further nesting of containers possible. It would preferably be structured with layers of insulation, vacuum layers, and layers of reinforcement. The container would preferably be engineered at a 2:1 length to width ratio and comprise nickel at 7%-9% where there is contact with liquid. The container may hold a cold thermal mass to deter gasification. It should be able to be emptied without tipping using a hand pump. The system of the present invention would use such a container as a “stage” to ramp down temperatures of the equipment in order to mitigate issues of thermal shock to the system. The container could also be used as a method of topping off the system of the present invention. 
         [0025]    Reference is next made to  FIGS. 5A-5H  which are schematic block diagrams showing a variety of applications of the LNG to CNG to NG system and methods of the present invention. In these diagrams residential area  200  is shown to implements the systems of the present invention receiving an LNG supply from LNG plant  202 . Internal to the area is LNG supply and cryogenic storage  204 . Through heat and time in the system of the present invention  206 , and from CNG storage  208 , the CNG may be utilized in CNG fueling  210  to applications  212 . Through pressure reduction  214  the system produces NG (&lt;30 psi)  216  for residential use  218  and optional natural gas distribution  220 . 
         [0026]      FIG. 5A  shows the preferred embodiment system and method.  FIG. 5B  the preferred residential use embodiment.  FIG. 5C  the addition of access to the NG distribution system.  FIG. 5D  the addition of the CNG fueling option.  FIG. 5E  the addition of the LNG fueling option  205 .  FIG. 5F  the addition of both the CNG and LNG fueling options.  FIG. 5G  adds the use of a refrigeration and LNG storage component  222 . Finally,  FIG. 5H  incorporates all of the above mentioned options. 
         [0027]    Reference is next made to  FIGS. 6A-6G  which show an alternate preferred embodiment of the structure of a system implementing the method of the present invention. This series of drawing figures discloses in partially schematic form (relative sizes represented) the basic structure of the system of the present invention and the progress of the method implemented with the system for converting LNG to usable CNG. 
         [0028]      FIG. 6A  discloses the essential components in the system and identifies operation of the system through a first step of loading LNG. In general, the system  400  comprises LNG container  402 , CNG maximum pressure container  404 , LNG-CNG phase change container  406 , NG powered heater  408 , CNG storage container  410 , and pressure reducer  412 . 
         [0029]    In the first step of the process where LNG is loaded into the system, valves leading into LGN container  402  are opened to receive the LNG. In  FIG. 6A  open valves are represented as open circles, with closed valves represented as darkened circles. One way valves and check valves are represented with triangles in circles. The CNG maximum pressure container  404  is at 5,000 psi while the LNG-CNG phase change container  406  is at 2,000 psi. Likewise, CNG storage container  410  may preferably be at 2,000 psi.  FIG. 6B  represents a balancing of pressure step in the operation of the system. Inlet valves are closed and valves between LNG container  402  and LNG-CNG phase change container  406  are opened. Thus beginning at 0 psi in LNG container  402  and ending at 500 psi. LNG-CNG phase change container  406  begins at 2,000 psi and ends at 500 psi. 
         [0030]    In  FIG. 6C  the step of charging phase change container  406  with LNG is carried out. In this view, the LNG is contained in a center Dewars like container within LNG-CNG phase change container  406 . A valve is opened between LNG container  402  and CNG maximum pressure container  404 . CNG maximum pressure container  404  begins at 5,000 psi and ends at less than whatever pressure is required to move the LNG into the phase change container  406 . CNG storage container  410  remains at 2,000 psi. 
         [0031]      FIG. 6D  demonstrates the step of applying heat to the phase change container  406  to facilitate the overall process. In this view, NG powered heater  408  is auto ignited at gas detection and heats a coil positioned along the length of phase change container  406 . CNG maximum pressure container  404  is now below 5,000 psi, once again representing only the pressure required to move the LNG into the phase change container  406 . LNG container  402  varies in pressure until all of the NG is consumed in the process resulting in a 0 psi in LNG container  402 . CNG storage container  410  again operates at 2,000 psi. 
         [0032]      FIG. 6E  represents the step of joining the LNG-CNG phase change container  406  and the CNG storage container  410 . Each of these two containers are then optimally positioned at 2,000 psi. The valves indicated between the CNG containers are activated when the pressures are equal. 
         [0033]    Reference is next made to  FIG. 6F  which shows the step of gasification being completed. Once again, NG powered heater  408  is operable to facilitate the movement of LNG into the phase change container  4306  and thereby into the CNG storage container  410 . Given the volumes and pressures associated with the previous steps in the system, the balance pressure between LNG-CNG phase change container  406  and CNG storage container  410  should end up at approximately 5,000 psi. This is also the pressure in CNG maximum pressure container  404 . The process, facilitated by NG powered heater  408 , utilizes all of the LNG deposited into LNG container  402 . 
         [0034]    Finally, as shown in  FIG. 6G , dispensing of the CNG may occur. Once again, the LNG container  402  is at 0 psi having expended all of its volume either into powering the NG powered heater  408  or primarily in converting LNG to CNG through phase change container  406  into CNG storage container  410 . As shown in  FIG. 6G , CNG may be dispensed directly from CNG storage container  410  or may be dispensed through an optional pressure reducer  412  to dispense low pressure natural gas. Typical pressures for the low pressure natural gas may be less than two atmospheres. The dispensing process is a two stage process. As shown, the CNG storage container  410  would dispense until pressure equalizes the tank being filled. At that point, the isolating valve between the phase change container  406  will open and the tank pressure is topped off. 
         [0035]      FIG. 7  a perspective view of a preferred embodiment of the phase change container structure of the present invention showing one implementation of a number of the structures shown generally in  FIGS. 6A-6G . The critical features disclosed in  FIG. 7  the horizontal and vertical elements that make up the arrangement of the LNG container  502  and the LNG-CNG phase change container  504 . The arrangement show allows for the gravity feed of LNG from LNG container  502  (a Dewar container oriented vertically) into phase change container  504  (a partial Dewar container oriented horizontally). Phase change container  504  is preferably constructed of a single section of tubular wall for ease of manufacture and maintenance. Heating element  510  extends into phase change container  504  as, for example, deriving from NG powered heater  408  shown in  FIGS. 6A-6G . 
         [0036]    Operation of the structure of the system shown in  FIG. 7  is essentially the same as that shown in  FIGS. 6A-6G  with the same set of valves and flow conduits. The gravity feed structure of the embodiment shown in  FIG. 7  eliminates the need to have CNG maximum pressure container  404  to push the LNG into the LNG-CNG phase change container as this is now accomplished by gravity feed. Here again, the system lends itself to implementation in smaller (lower quantities) environments such as residential homes, small industrial applications, and the like. 
         [0037]    Although the present invention has been described in conjunction with a number of preferred embodiments, those skilled in the art will recognize modifications to these embodiments that still fall within the scope of the present invention. Alternately, the present invention may be implemented in conjunction with electrolysis at depth and/or pressure. Alternate embodiments in conjunction with differently sized systems are also anticipated.