Abstract:
A fixed and/or stationary modular unit consists of a hydraulic fluid tank, a pressurization pump, and a compressed gas transportation system consisting of a cylinder or set of cylinders. Each cylinder has two ends, a charging end and a dispensing end, with actuated valves positioned at each end. A pair of valves are located at each charging end of each cylinder, with one valve connected to an incoming hydraulic fluid line and the other valve connected to a hydraulic fluid return line. A valve is connected at the dispensing end of each cylinder. Adapters at each end of the cylinder have curved J-tubes that extend into the cylinder. The J-tube on the charging end curves downward and the J-tube on the dispensing end curves upward. The cylinder or sets of cylinders are inclined to a desired level for the dispensing process.

Description:
[0001]    This application claims priority to provisional application 61/050,033, filed May 2, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention is a hydraulic pressurization station and/or equipment, also known as an “HPU” (Hydraulic Pressurization Unit), which can be connected to an over-the-road semi trailer (OST) of the type known as a horizontal cylinder (or tubular-cylinder) trailer. This invention also applies to a compressed gas pressurization and control system of an over-the-road semi trailer for the compressed gas dispensing line, maintaining a constant pressure throughout the entire operation. 
       BACKGROUND OF THE INVENTION  
       [0003]    Compressed natural gas (CNG) is any natural gas that has been processed and treated for transportation, in bottles or cylinders, at ambient temperature and at a pressure approaching the minimum compressibility factor. 
         [0004]    Natural gas is colorless, odorless, and lighter than air, and it easily dissipates into the atmosphere when it leaks. It bums with a flame that is almost invisible, and it has to be raised to a temperature above 620° C. in order to ignite. By way of comparison, it should be noted that alcohol ignites at 200° C. and gasoline at 300° C. For safety reasons, natural gas is odorized with sulfur for marketing purposes. 
         [0005]    Natural gas is an alternative to oil and therefore, it has great strategic importance, since it is a fossil fuel found in porous subsurface rock. It usually has low levels of pollutants, similar to nitrogen, carbon dioxide, water and sulfur compounds that remain in a gaseous state at atmospheric pressure and ambient temperature. Compressed natural gas is stored at a pressure of 220 bars or 3190 psi and is transported in trailers of varying volumetric capacity, depending on legislation and customer/project requirements. 
         [0006]    The principal advantage of using natural gas is the preservation of the environment. In addition to economic benefits, it is a non-polluting fuel and it burns cleanly, so its combustion products that are released into the atmosphere do not need to be treated. 
         [0007]    The great need to transport and store natural gas has contributed to increasing gas research around the world. Traditionally, only a handful of methods of transporting and storing large quantities of gas have turned out to be feasible. The main problem in storing and transporting gas is the fact that it remains a gas far below ambient temperature and that a small quantity of gas occupies a large amount of space. The solution is to reduce the space gas occupies. Initially, the condensation of gas to a liquid was the mainly recommended logical solution. A typical natural gas (which is about 90% CH4) can be reduced to 1/600 of its gaseous volume when it is compressed into a liquid. Technically speaking, gaseous hydrocarbons in the liquid state are known as liquefied natural gas, which is more commonly known as LNG. 
         [0008]    As indicated by the term, LNG involves liquefying natural gas and normally includes transporting and storing natural gas in a liquid state. Although liquefication would seem to be a solution as far as storage and transportation problems are concerned, there are certain disadvantages. First, in order to liquefy natural gas, it must be cooled to approximately −162° C. at atmospheric pressure before it liquefies. Second, LNG tends to warm up over long storage or holding periods, thus it does not remain at low temperature, which is required in order for it to remain in a liquid state. Cryogenic methods have been used to keep LNG well within the required temperature range while being transported, and the carrier system used to transport LNG must be fully cryogenic. Third, LNG must be regassified by distillation before it can be used, The cryogenic process requires a high initial cost to load and unload LNG. The container system and storage vessels require rare metals to keep the temperature at 160° C., so it cannot be justified as an economic alternative. 
         [0009]    In order to solve the technical problems of ambient conditions of storage and transportation of LNG, as well as its temperature and high costs, a method of transporting compressed natural gas was developed. Natural gas is compressed or pressurized at high pressures. This is what is commonly called compressed natural gas or CNG. 
         [0010]    Various methods have been proposed for storing and transporting compressed gases, such as natural gas, in pressurized vessels for overland transportation. The gas is typically stored and transported at high pressure and low temperature to maximize the amount of gas contained in each gas storage system. For example, compressed gas must be in a dense single-fluid state characterized as a very dense gas with no liquid. 
         [0011]    CNG is typically transported over land in tanker trucks or tank wagons. Tankers have storage containers such as pressurized metal vessels. These storage vessels have high burst strengths and withstand the ambient temperature at which CNG is stored. 
         [0012]    Before compressed natural gas is transported, the desired operation state is obtained first, normally by compressing the gas to a high temperature and then cooling it to a low temperature. After the compressing and cooling process, CNG is loaded into the holding vessels of the storage system. The CNG is then shipped to its destination. 
         [0013]    Upon arrival at destination, the CNG is unloaded, typically at a terminal with a number of high-pressure storage vessels or a feedline into a high-pressure turbine. If the terminal is at a pressure of 69 bar or 1000 psi for example, and the storage vessels are at 138 bar or 2000 psi, then valve must be opened and the gas must be expanded at the terminal until the pressure in the vessels falls to a final pressure between 69 bar or 1000 psi and 138 bar or 2000 psi. 
         [0014]    With conventional procedures, the CNG that has been shipped remains in the storage vessels (residual gas), which is then compressed in the terminal storage vessels by means of compressors. These compressors are expensive and increase the capital cost of the unloading process. Further, the temperature of the residual gas is raised by the heating effect of compression. The high temperature increases the required storage capacity, unless the temperature is lowered or excess gas is removed, thereby increasing onshore costs for transporting CNG. There would also be high energy consumption. 
         [0015]    A new technique in necessary to reduce costs and the complexity of unloading CNG. The following technique may solve one or more of these problems. The present technique exceeds the deficiencies described by providing hydraulic pressurization equipment that is capable of servicing the motor vehicles efficiently while maintaining the same pressure at all times. 
       SUMMARY OF THE INVENTION  
       [0016]    A fixed and/or stationary modular unit consists of a hydraulic fluid tank, a pressurization pump, and a compressed gas transportation system consisting of a cylinder or set of cylinders. Each cylinder has two ends, a charging end and a dispensing end, with actuated valves positioned at each end. A pair of valves are located at each charging end of each cylinder, with one valve connected to an incoming hydraulic fluid line and the other valve connected to a hydraulic fluid return line. A valve is connected at the dispensing end of each cylinder. Adapters at each end of the cylinder have curved J-tubes that extend into the cylinder The J-tube on the charging end curves downward and the J-tube on the dispensing end curves upward. The cylinder or sets of cylinders are inclined to a desired level for the dispensing process. 
         [0017]    Gas is dispensed from the dispensing end of the cylinder by opening the valve at the dispensing end. The valve connected to the incoming hydraulic fluid line is opened and hydraulic fluid is pumped from the tank and into the cylinder to maintain a constant pressure within the cylinder. When the cylinder is exhausted, the valve at the dispensing end of the cylinder is closed. The valve connected to the incoming hydraulic fluid is also closed, and the valve connected to the hydraulic fluid return line is opened. Remaining gas in the cylinder expands and discharges the hydraulic fluid from the cylinder and into the return line where it travels back into the hydraulic fluid tank. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]      FIG. 1(   a ) is a schematic of the hydraulic pressurization equipment (HPU) portion of the compressed gas filling system as comprised by the present technique;. 
           [0019]      FIG. 1(   b ) is a detailed schematic of the over-the-road compressed gas semi trailer portion of the compressed gas filling system as comprised by the present technique; 
           [0020]      FIG. 2  is a side view of a horizontal gas cylinder in its original orientation; 
           [0021]      FIG. 3  is a side view of a horizontal gas cylinder inclined to a desired angle; 
           [0022]      FIG. 4  is an end view of cylinders being supported by a cradle device connected to a hydraulic lift; 
           [0023]      FIG. 5  is an assembled cylinder, showing the adapters illustrated in  FIGS. 6 and 7 ; 
           [0024]      FIG. 6  is a sectional view of the internal charging/discharging port at the bottom end of a horizontal gas cylinder; 
           [0025]      FIG. 7  is a sectional view of the internal gas-dispensing port at the upper end of a horizontal gas cylinder; 
           [0026]      FIG. 8  is a sectional view of a tilted gas cylinder with some hydraulic oil in the cylinder; 
           [0027]      FIG. 9  is a sectional view of a nearly depleted tilted gas cylinder with a large amount of hydraulic oil in the cylinder; 
           [0028]      FIG. 10  is a flow chart of the gas cylinder dispensing cycle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    Referring to  FIG. 1(   a ), the gas dispensing system consists of a hydraulic pressurization unit (HPU, which is connected to an over-the-road compressed gas semi trailer ( FIG. 1   b )). In an alternate embodiment, the HPU can be mounted on and a part of the over-the-road trailer itself. The over-the-road semi trailer may carry compressed natural gas, hydrogen, or other compressed gas cylinders. 
         [0030]    The HPU consists of a hydraulic fluid tank  6 , a motor  13 , a flexible coupling  12  used to join rotating shafts, a suction and pressurization pump  1 , an outgoing manifold block  16 , a return manifold block  19 , a pressure-control sensor  58 , an electricelectronic control panel (not visible), and programmable logic controller (PLC) software. The HPU also consists of control valves  3 ,  4 ,  5 ,  17 , manual shutoff valves  10 ,  25 ,  28 ,  31 ,  48 , and particle filters  11 ,  46 . The HPU also consists of manual release valves  24 ,  27 ,  30 ,  34 . The outgoing manifold block  16  consists of valves  4 ,  5 ,  17 , pressure sensor  58 , excess-flow valve  3 , a check valve  14 , and restrictors  21 . The return manifold block  19  consists of solenoid shutoff valve  5 . Mounted to the oil reservoir tank  6  are photoelectric control sensors  63 ,  64 , oil level switches  7 , and a reservoir tank pressure switch (not visible). The HPU is used to charge compressed natural gas (CNG), hydrogen, or other compressed gas cylinders to a specific pressure. The HPU regulates the cylinder pressure by pumping hydraulic oil into the cylinders in order to maintain a specific pressure. The outgoing manifold block  16  controls the flow of hydraulic oil from the HPU to the compressed gas semi trailer. The return manifold block  19  controls the flow of hydraulic oil from the compressed gas semi trailer back to the HPU. 
         [0031]    Referring to  FIG. 1(   b ), the HPU ( FIG. 1(   a )) is connected to an over-the-road compressed gas semi trailer comprised of gas cylinder module  59 , of which each module may consist of a single cylinder or grouped sets of horizontal (tubular) cylinders. For example, in this embodiment, module  59  is comprised of cylinders  39   a - d . Each cylinder has a charging end  62  and a dispensing end  61 , whereby a set of valves consisting of the following: safety devices  40   a - d , manual shutoff valves  41   a - d ,  44 , a pressure gauge  43 , and actuated shutoff valves  42   a - d , are connected at the dispensing end  61 . The downstream connection from shutoff valve  44  is connected to a compressed gas loading/unloading line  54 . A set of valves consisting of: pressure gauges  38   a - d , manual shutoff valves  37   a - d , and actuated shutoff valves  35   a - d ,  36   a - d , are connected at the charging end  62 . 
         [0032]    The upstream connections from actuated shutoff valves  35   a - d  are connected to an incoming line  52 , which has a quick connect/disconnect coupling mechanism positioned at its end. The downstream connections from actuated shutoff valves  36   a - d  are connected to oil return line  53 , which has a quick connect/disconnect coupling mechanism positioned at its end. The upstream connections from the actuated shutoff valves  35   a - d  are connected parallel to one another. The downstream connections from actuated shutoff valves  42   a - d  are connected parallel to one another. The downstream connections from actuated shutoff valves  35   a - d  are connected with the charging end  62  of each of the cylinders  39   a - d  in series. The downstream connections from actuated shutoff valves  36   a - d  are connected parallel to one another. The upstream connections from actuated shutoff valves  42   a - d  are connected with the dispensing end  61  of each of the cylinders  39   a - d  in series. 
         [0033]    Each module on the over-the-road compressed gas semi trailer is connected similarly. The cylinders on the over-the-road semi trailer are charged with compressed gas at another location. Subsequent to charging with compressed gas, the over-the-road semi trailer is transported to a gas filling station where an HPU is installed. In an alternate embodiment, the HPU can be mounted on the over-the-road trailer. The over-the-road compressed gas semi trailer is connected to the HPU with three hoses: an outgoing oil line  57 , an oil return line  56 , and a compressed gas line  55 . 
         [0034]    Referring to  FIGS. 2 ,  3 , and  4 , once the cylinder module is connected to the HPU, the cylinder module is inclined using a hydraulic jack  47  with one end of the jack attached to the over-the-road semi trailer and the other end attached to cradle supports  49  that span the contours of the bottom of the cylinder module. The cylinders  39   a - d  contained in cylinder module  59  are inclined to a specified angle θ with the charging end  62  forming the vertex point and the dispensing end  61  raised to form the proper angle θ. 
         [0035]    Referring to  FIGS. 5 ,  6 , and  7 , each cylinder has a special curved adapter  71  at the charging/discharging end  62  ( FIG. 6 ) and a special curved adapter  75  at the dispensing end  61  ( FIG. 7 ).  FIG. 6  illustrates the internal details of the gas charging area, which is at the bottom portion of the charging/discharging end  62  of the tubular type cylinder  39   a.  Adapter  71  consists of a curved tube  73  whose radius is dependent on the radius of curvature of the charging/discharging end  62  of the cylinder  39   a.  The adapter tube  73  curves downward toward the bottom surface of the charging/discharging end  62  of the cylinder  39   a.  The purpose of adapter  71  is to feed oil into the cylinder in a homogeneous form and to prevent blasts of oil into the cylinder. Additionally, when the oil is being discharged from the tank, adapter  71  helps prevents gas from entering the line discharging oil. This is due to the fact that the hydraulic fluid is more dense than the compressed gas within the cylinder, and as a result, a natural partition is created within the cylinder with a compressed gas layer formed atop a hydraulic fluid layer as hydraulic fluid enters the cylinder. 
         [0036]      FIG. 7  illustrates the internal detail of the gas dispensing area, which is at the upper portion of the dispensing end  61  of the tubular type cylinder  39   a.  Adapter  75  consists of a curved tube  77  whose radius is dependent on the radius of curvature of the dispensing end  61  of the cylinder  39   a.  The adapter tube  77  curves upward toward the top surface of the dispensing end  61  of the cylinder  39   a.  The purpose of adapter  75  is to increase gas dispensing efficiency and to prevent hydraulic fluid from entering the line receiving gas. Additionally, the curved adapter tube  77 , combined with the tilt of the tank, ensures that a maximum quantity of gas is dispensed before hydraulic oil reaches the tube  77 . As previously noted, this is due to the fact that the hydraulic fluid is more dense than the compressed gas within the cylinder. 
         [0037]    Referring back to  FIGS. 1(   a ) and  1 ( b ), in order to dispense the compressed gas from the cylinder module, the start button on the control panel (not visible) is pushed and the HPU begins unloading gas from compressed gas cylinder  39   a  of module  59  on the over-the-road semi trailer. The electronic control panel (not visible) sends a signal to actuated shutoff valve  42   a  on the dispensing end  61  of module  59 , and actuated shutoff valve  51  on the HPU, opening valves  42   a , and  51 , allowing the gas in cylinder  39   a  of module  59  to be dispensed. The gas dispensed from module  59  flows through gas line  54 , which has a quick connect/disconnect coupling mechanism positioned at its end, and hose  55  until it reaches gas line  32  of the HPU. When the gas reaches line  32  of the HPU, the gas flows through shutoff valve  31  and a hydraulic fluid separator  33 , and then through a shutoff valve  48 , particle filter  46 , an actuated shutoff valve  51 , and finally through the dispensing gas line  60 . As the gas is dispensed from module  59 , the pressure sensor  58  senses the gas pressure drop in cylinder  39   a,  and when the pressure reaches a selected level, such as  200  bar or less, the sensor  58  sends an electrical signal to the control panel (not visible), which then sends a signal that simultaneously actuates motor pump  13  and opens actuated shutoff valve  35   a  on the charging end  62  of module  59 . 
         [0038]    As motor  13  runs, pump  1  suctions the hydraulic fluid from tank  6 , forcing it through manual shutoff valve  10  and particle filter  11 . Pump  1  then forces the hydraulic fluid through the outgoing block  16 , which regulates the fluid pressure at a selected range, such as  200 - 220  bar by means of flow valve  3 , control valve  5 , pressure sensor  58 , and PLC control software (not visible). The hydraulic fluid is forced through outgoing block  16 , through outgoing line  26  and outgoing line  57  to incoming oil line  52  of the over-the-road semi trailer. Control valve  3  also acts as an independent safety pressure relief valve, limiting system pressure to  240  bar in case of pressure sensor  58 , PLC (not visible), or other system component malfunction. The hydraulic fluid flows through actuated shutoff valve  35   a  and into cylinder  39   a  of module  59 , forcing the gas from cylinder  39   a  out the dispensing end  61  of the module ( FIG. 8 ). Once the pressure sensor  58  senses the gas pressure has reached a selected pressure, such as  220  bar, an electronic signal from the control panel (not visible) actuates control valve  17 , which allows the oil to flow back to the tank  6  through excess-flow valve  3 . After a short time delay, motor  13  is switched off. During this time, gas is being dispensed through dispensing line  60  and into a vehicle. 
         [0039]    As illustrated by  FIG. 10 , the gas is simultaneously dispensed and the process discussed above is repeated until the hydraulic fluid volume reaches 95% of the hydraulic volume capacity of cylinder  39   a  of module  59  ( FIG. 9 ). When the hydraulic fluid volume reaches 95% of the hydraulic volume capacity of cylinder  39   a,  level switch  7  of hydraulic fluid tank  6  sends an electronic signal to control panel (not visible), and the control panel (not visible) immediately begins unloading natural gas from cylinder  39   b.  If cylinder  39   b  is at the desired pressure, the control panel sends a signal to motor  13 , which had been on, and after a short time delay switches off. However, if cylinder  39   b  is at a pressure less than desired, motor  13  may remain on. Simultaneously, actuated shutoff valves  35   a  and  42   a  are closed, and any excess hydraulic oil traveling to cylinder  39   a  is allowed to flow back to the tank  6  through excess-flow valve  3 . At the same time, a signal is sent to actuated shutoff valves  36   a  and  17 , causing them to open. 
         [0040]    The residual 5% of the capacity of the hydraulic volume, which is high pressure gas, of cylinder  39   a  expands, making the hydraulic fluid that had been forced into cylinder  39   a  of module  59  return to tank  6 , flowing through valve  36   a  and return line  53 , hose  56 , and the HPU return line  29  to actuated shutoff valve  5  and the oil reservoir tank  6 , which is at atmospheric pressure. 
         [0041]    When photoelectric sensors  63  and  64  detect gas in return line  29 , the sensor sends an electrical signal to the control panel, which sends an electrical signal to actuated shutoff valves  36   a  and  5 , which had been open and now close, thereby shutting down the return of hydraulic fluid to tank  6 . In the event that sensors  63 ,  64 , do not detect the presence of gas, a pressure sensor (not visible) within tank  6  monitors the pressure within tank  6 . If the pressure in tank  6  were to rise above atmospheric, this would indicate that gas had entered tank  6 , and an electric signal would be sent to actuated shutoff valves  36   a  and  5 , closing them. 
         [0042]    As previously noted, while the oil discharge process is occurring for cylinder  39   a , compressed gas may be simultaneously unloaded from cylinder  39   b  (beginning another cycle). Additionally, once each cylinder in module  59  is exhausted, a second module with fully charged cylinders located on a second over-the-road semi trailer can begin unloading while the hydraulic fluid in final cylinder  39   d  is discharged. Once the hydraulic oil discharge process begins for cylinder  39   d,  hoses  57 ,  54  can be disconnected from module  59  and connected to the second module on the second semi trailer. Compressed gas may then be dispensed from the second module in the same manner as previously discussed, while cylinder  39   d  is discharging. When the hydraulic oil discharge process for cylinder  39   d  is complete, module  59  can be declined to its original position parallel to the ground ( FIG. 2 ), and hose  56  may be disconnected from module  59  and connected to the second module. Module  59  may then be taken away for refilling of cylinder  39   a - d . The number of cylinders in each module, and the number of modules depends solely on the volume of gas that needs to be transported and the manufacturing standards of the over-the-road semi trailer. 
         [0043]    The invention has significant advantages. The hydraulic pressurization equipment is capable of servicing motor vehicles efficiently while maintaining the same pressure at all times. The special curved adapters, together with the inclination of the cylinder module, ensure efficient dispensing and discharging of the cylinders with minimal risk of gas entering the discharge line or hydraulic fluid entering the dispensing line. The quick connect/disconnect qualities of the hose connection between the HPU and the cylinder module allow for timely and efficient transition from one module to another. 
         [0044]    While the invention has been shown in only a few of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.