Patent Publication Number: US-11649929-B2

Title: Gas dispensing system with tank pressure and heat management

Description:
CLAIM OF PRIORITY 
     This application claims the benefit of U.S. Provisional Application No. 63/009,614, filed Apr. 14, 2020, the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to a cryogenic storage and delivery systems for providing gas to a use device or process and, more particularly, providing gas to a use device or process while managing the heat and pressure in the cryogenic tank. 
     BACKGROUND 
     Cryogenic tanks are an efficient way of storing cryogenic fluids for use as gases. The gas is typically stored in a liquefied state because it occupies a much smaller volume. Liquefied natural gas, for example, occupies approximately 1/600 th  the space as a liquid versus in the gaseous state. Temperature and pressure regulation of cryogenic tanks is extremely important. Liquefied gas is stored in insulated cryogenic tanks because of the low temperature requirements and typically at lower pressures. Furthermore, the stored cryogenic liquid is typically saturated, so that the gas and liquid states simultaneously exist at a desired temperature and pressure. 
     Use devices often require the delivery of gas from the cryogenic tank system at a specific temperature and pressure. While providing gas to use devices, the pressure and temperature in the cryogenic tank may fluctuate. When temperature and/or pressure increase too much, it may be required to vent gas to the atmosphere, causing a loss of stored product. It is, therefore, desirable to have a cryogenic delivery tank system for providing gas to a use device which can manage internal temperature and pressure and prevent loss of product. 
     A prior art system for dispensing gas from a cryogenic liquid storage and delivery tank, as shown in  FIG.  1   , includes a cryogenic tank  100  with cryogenic liquid  110  and vapor  120  in the headspace above the liquid level line  115 . The cryogenic tank includes an inner shell  101  and an outer shell  102 . The cryogenic tank system includes a vapor or first pipe or line  400  from cryogenic tank  100  to a product vaporizer  12  and to a distribution outlet valve  10 . Pipe or line  400  can include a number of manual isolation valves, such as valve  30 . Pipe or line  400  also includes an economizer regulator  6 . A liquid or second line  300  leads from the liquid portion of the tank to vaporizer  12  and distribution outlet valve  10 . In addition, the system includes a pressure building or third line  500  which leads from the liquid portion of the tank to pressure building vaporizer  13  and back to the tank  100 , and includes a pressure building regulator  7 . 
     When the distribution valve  10  is opened, gas from the system is taken for consumption by a use device or process. The regulator  7  is set to open at approximately 30 bar, while the economizer  6  is set to open at approximately 32 bar. Accordingly, if the tank pressure is higher than 32 bar, gaseous vapor from the tank head or top space is supposed to flow to the product vaporizer  12 . However, the economizer  6  is a small regulator with a small capacity (kv or cv value) and, therefore, only a low flow rate is accommodated without a large pressure drop across the economizer. Gas flows through line  400  when the economizer  6  is open, as shown in  FIG.  2    as path  401 . When the pressure in the headspace of the tank drops below approximately 32 bar, economizer  6  closes. 
     Regardless if economizer  6  is open or closed, liquid from the bottom of the tank travels to the vaporizer  12  through liquid pipe  300  along path  301 , as shown in  FIG.  3   , to meet the consumption requirements when the dispensing or distribution valve  10  is open. 
     Should the tank pressure drop below the pressure building regulator  7  set point, this regulator opens and, as illustrated in  FIG.  4   , liquid flows along line  501  to pressurize the tank using the vapor from the pressure building vaporizer  13 . 
     Depending on the amount of gas taken by the use device or process at  10 , the product vaporizer  12  will be flooded. Closing the distribution valve  10  will stop the gas offtake and the pressure will rise sharply in the product vaporizer  12  due to the evaporation of the residual liquid remaining therein. The generated pressure pushes the vapor and the heated liquid, which has not yet evaporated, back to the bottom of the tank. The economizer  6  is closed at that time. During frequent cycling (gas consumption, interruption, gas consumption, etc.), this process rapidly heats the liquid in the tank. After some time, the pressure in the tank will build to the main relief valve set point. The safety valves, indicated in general at  600 , will then open which results in loss of a portion of the stored fluid. 
     For this prior art design, the economization function has a very small working window. The economization works only when there is high pressure within the tank and very low consumption by the use device or process through distribution valve  10 . At higher consumptions, the flow rate and thus pressure drop across the economizer  6  increase and primarily only the liquid is taken from the tank  100 . This causes the pressure to build in the tank which may require venting of cryogen from the tank. 
     It is desirable to provide a cryogenic delivery tank for supplying gas to use devices with improved maintenance of a desirable temperature and pressure in the cryogenic tank. 
     SUMMARY OF THE DISCLOSURE 
     There are several aspects of the present subject matter which may be embodied separately or together in the methods, devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto. 
     In one aspect, a system for cryogenic gas delivery includes a cryogenic tank containing a cryogenic liquid and a gas within a headspace above the cryogenic liquid. The system also includes a first vaporizer and a second vaporizer and a use outlet. A first pipe is configured to transfer gas from the headspace through the first vaporizer to the use outlet. A second pipe is configured to transfer liquid from the tank through the first vaporizer so that a first vapor stream is directed to the use outlet. A third pipe is configured to build pressure within the tank by transferring liquid from the tank through the second vaporizer so that a second vapor stream is directed back to the headspace of the tank. A first regulator valve is in fluid communication with the second pipe. The first regulator valve is configured to open when a pressure on an outlet side of the first regulator drops below a first predetermined pressure level. A second regulator valve is in fluid communication with the third pipe. The second regulator valve is configured to open when a pressure inside the tank drops below a second predetermined pressure level. The first predetermined pressure level is higher than the second predetermined pressure level. 
     In another aspect, a method of providing gas from a cryogenic tank to a use device while maintaining a temperature and pressure within the tank includes liquid stored in a delivery tank includes opening a dispensing valve to start distributing gas to a use device. At a first tank pressure, gas is directed through a first pipe and a first vaporizer to the use device. At a second tank pressure, liquid is directed from the tank through a second pipe and the first vaporizer to the use device. At a third tank pressure, liquid is directed from the tank through a third pipe and a second vaporizer and back to the tank. The dispensing valve is closed to stop distributing gas to a use device and any residual liquid or gas in the first vaporizer is returned back to the top of the tank by the first pipe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic illustration of a prior art cryogenic delivery tank system. 
         FIG.  2    is a schematic illustration of a first gas delivery function of the system of  FIG.  1   . 
         FIG.  3    is a schematic illustration of a second gas delivery function of the system of  FIG.  1   . 
         FIG.  4    is a schematic illustration of pressure building function of the system of  FIG.  1   . 
         FIG.  5    is a schematic illustration of one embodiment of a delivery tank system of the current disclosure. 
         FIG.  6    is a schematic illustration of a first gas delivery function of the system of  FIG.  5   . 
         FIG.  7    is a schematic illustration of a second gas delivery function of the system of  FIG.  5   . 
         FIG.  8    is a schematic illustration of a pressure building function of the system of  FIG.  5   . 
         FIG.  9    is a schematic illustration of another embodiment of a delivery tank system of the current disclosure. 
         FIG.  10    is a schematic illustration of another embodiment of a delivery tank system of the current disclosure. 
         FIG.  11    is a schematic illustration of a first gas delivery function of the system of  FIG.  10   . 
         FIG.  12    is a schematic illustration of a second gas delivery function of the system of  FIG.  10   . 
         FIG.  13    is a schematic illustration of another embodiment of a delivery tank system of the current disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An embodiment of the disclosure provides a storage and delivery tank with a heat and pressure management function. 
       FIG.  5    illustrates a cryogenic delivery tank system  200  of the current disclosure including cryogenic tank  203 . Cryogenic tank  203  is employed to store cryogenic liquid. As examples only, the cryogenic liquid can be nitrogen, helium, oxygen or any other known cryogenic fluid. 
     In the illustrated embodiment, cryogenic tank  203  has an inner shell  201  and an outer shell  202 , where the inner shell defines an interior of the tank. Cryogenic liquid  210  is stored within the interior of the inner shell  201 . Cryogenic liquid  210  occupies a specific volume of cryogenic tank  203 , with the remaining volume occupied by cryogenic gas or vapor  220 . The liquid level  215  is included for illustrative purposes, but the liquid level may vary, especially at different events (after delivery of gas by the system, refilling the tank with liquid, etc.). 
     In the illustrated embodiment, the cryogenic tank  203  is a vertical tank. In other embodiments, the tank  203  may be a horizontal tank. 
     Cryogenic tank  203  of the current invention, although shown as double walled, can be single or triple walled as well. The cryogenic tank can be made from copper alloy, nickel alloy, carbon, stainless steel or any other known material in the art. 
     Cryogenic tank  203  may have insulation between inner and outer walls (or shells) and/or may be vacuum insulated. Single or multilayer insulation of any known materials for insulation can be utilized. 
     The inner vessel  201  can be joined to the outer vessel  202  by one or more inner vessel support members. For example, as known in the art, the inner vessel support member may connect the neck and base of the inner vessel to the outer vessel. 
     Cryogenic delivery system  200  includes at least one vaporizer and preferably at least two for converting a liquefied gas to a gas for use in by a use device or process. Various types of vaporizers can be used for the vaporizers disclosed herein, such as ambient air, circulating water, electric, fuel-fired, steam, or water bath vaporizers. In one embodiment, an ambient air vaporizer is utilized. Cryogenic delivery system  200  has at least a first vaporizer  12  and a second vaporizer  13 . Vaporizer  12  functions as a product vaporizer and converts liquid from the tank to vapor and warms the vapor, or warms vapor from the headspace of the tank, to the appropriate pressure and temperature for the use device. Vaporizer  13  functions as a pressure building vaporizer for raising the pressure of the cryogenic tank by taking liquid from the tank and forming a gas before returning it to the headspace of the tank. Although three vaporizers are shown for each of the product and pressure building vaporizers, more or fewer vaporizers can be included in cryogenic delivery system  200 . 
     A number of connected transfer pipes or lines provide different functions with regard to the tank and use device as part of cryogenic delivery system  200 . Cryogenic delivery system  200  includes a liquid line  350  from the liquid portion of the tank, which provides liquid for converting to gas through the vaporizer  12  and to the use outlet  250 , which connects to a use device or process. Vapor line  450  provides gas from tank  203  for distribution to the use device through the use outlet  250  after moving through vaporizer  12 . Pressure building line  550  directs liquid from the tank  203  to the pressure building vaporizer  13  for circulation of a resulting vapor stream back into the tank  203 , so that the pressure in the tank may be increased. Although specific detail is not shown in the figures, both ends of each transfer pipe can feature a number of specific fittings. For instance, each one may comprise a removable and reusable seal. Each pipe end may also include a valve or vent. The cross-sections of this pipe and other structures can have various shapes, such as a circle, ellipsis, square, triangle, pentagon, hexagon, polygon, and other shapes. 
     The transfer pipes of the cryogenic delivery tank system  200  may have a number of valves. Line  450  has an isolation valve  32 , while line  350  has a valve  10 , that in the embodiment of  FIG.  5    is an isolation valve. Line  550  has an isolation valve  8 . Use outlet  250  may have a dispensing valve that is opened to provide gas to the use device or process. 
     The valves of the system can be, but are not limited to, glove valves, ball valves, check valves, gate valves, tilting disk check valves, swing-check or stop-check valves. 
     Valves can also be electromechanical valves, such as solenoid valves. In one embodiment, the dispensing valve at the use outlet  250  is a solenoid valve. 
     Pressure building line  550  includes pressure building regulator  16  and liquid line  350  includes liquid regulator  17 . In the embodiment illustrated in  FIG.  5   , vapor line  450  does not have a regulator valve or economizer. 
     Cryogenic tank system  200  may include devices or gauges for reading different characteristics of the tank system. These devices or gauges can show pressure, temperature, differential pressure, liquid level, etc. 
     Cryogenic tank system  200  may also include a control system. The control system may include a controller and optionally various sensors (such as pressure and temperature sensors) positioned on or in the system. The controller may be utilized to control various parts of the cryogenic tank system such as the valves of the cryogenic tank system  200 . The controller may be wired or wireless and is in communication with the optional sensors and those valves and other portions of the systems that it controls. The controller includes a processor or other computer device and can be programmable so as to regulate or initiate processes upon certain events or status information, including placing the system in the configurations described below. The controller may also provide information such as historical data or various types of indications to a user. 
     In the embodiment of  FIG.  5   , or any other embodiments of the current disclosure, the cryogenic tank system  200  includes at least one pipe for filling the tank with cryogenic liquid. In one embodiment there is a separate fill pipe and a separate withdrawal pipe. There may be other paths out of the inner vessel to fill and remove the liquid as well. The fill and withdrawal pipes may be any suitable conduit for conveying or allowing the flow of fluid therethrough. 
       FIG.  6    illustrates a first gas delivery function by the cryogenic tank system  200 . Valve  32  of line  450  is open and remains open through the operations described below. When the use device or process is connected and a dispensing valve is opened at the use outlet  250 , gas transfers from the headspace of the cryogenic tank  203 , so long as the pressure in line  450 , and thus on the outlet side of liquid regulator  17 , is higher than a specific pressure. In one embodiment, that pressure is approximately 30 bar. In other words, liquid regulator  17  is closed when the pressure on the outlet side (i.e. the pressure within line  450 ) is above approximately 30 bar. Gas travels from the cryogenic tank headspace through pipe  450  and product vaporizer  12  (where it may be warmed) to the use outlet  250 , as indicated in general by arrows  451 . Taking the vapor from the tank headspace significantly improves the overall heat management because removing the gas removes a significant amount of heat from the tank. Unlike the conventional system, there is no economizer or regulator on the line  450  to interfere with the gas transferring out of the tank headspace. 
       FIG.  7    illustrates a second gas delivery function by the cryogenic tank system  200 . As stated previously, liquid regulator  17  on line  350  is set to a specific pressure of approximately 30 bar. When the pressure in the cryogenic tank headspace lowers due to removal of the gas/vapor from the headspace, the pressure within line  450  will drop below 30 bar and liquid regulator  17  will open. Liquid will then flow from the tank through line  350  and the regulator  17  to the product vaporizer  12 . The resulting vapor will then flow through the use outlet  250  to the use device or process. The fluid path is shown in general by arrows  351  in  FIG.  7   . 
       FIG.  8    illustrates a pressure increasing function by the cryogenic tank system  200 . The pressure building regulator  16  on line  550  is set to open when the pressure within the tank drops to a specific pressure. In one embodiment, the specific pressure is approximately 29 bar. When the pressure in the cryogenic tank lowers to that specific pressure, due to removal of the gas/vapor from the headspace and/or liquid from the bottom of the tank, liquid will flow from the tank through line  550  to the pressure building vaporizer  13 . The resulting vapor will flow back to the cryogenic tank  203 , entering in the vapor headspace. The fluid path is shown in general by arrows  551  in  FIG.  8   . The pressure building regulator  16  closes when the pressure in the tank rises above approximately 29 bar. This maintains a desired pressure in the tank and to the product vaporizer  12 . 
     When consumption by the use device or process is stopped, liquid remaining in the product vaporizer  12  evaporates. The pressure generated by this action pushes back the heated liquid that has not yet been able to evaporate and the residual vapor. The liquid and vapor travel back through line  450  and into the headspace of the cryogenic tank  203 . The liquid regulator  17  will be closed due to higher pressure in the product vaporizer  12 . The pressure inside the tank will likely rise back above 29 bar, thus closing the pressure building regulator  16 . Excess heat in the form of vapor will again build at the top of the tank and enable gas/vapor removal from the top of the tank before switching to liquid withdrawal during the next gas delivery or dispensing cycle. 
     This improvement in design ensures that the cold liquid at the bottom of the tank will remain in the tank and will not be warmed as in the prior art system of  FIG.  1   . By keeping the liquid cold in the tank, it also maintains the thermal capacity of the stored liquid. Therefore, even if there is frequent cycling (gas consumption, interruption, gas consumption, etc.), the effects will be limited and result in less frequent opening of a relief valve and lower losses of the stored liquid. 
       FIG.  9    illustrates an additional embodiment of the current disclosure, wherein cryogenic tank system  225  uses a check valve  18  along liquid line  350 . The cryogenic tank system  225  can include all of the features of cryogenic tank system  200 , but with the additional check valve  18 . Check valve  18 , as a one-way valve, prevents liquid flow back to the bottom of the cryogenic tank from the product vaporizer  12  after the gas consumption is stopped in the event that the pressure in the product vaporizer is below the set point of liquid regulator  17  (and thus liquid regulator  17  is open). 
     Alternatively, the valve  10  of  FIG.  9    may be a globe check valve (and check valve  18  omitted) that prevents liquid flow back to the bottom of the cryogenic tank from the product vaporizer  12  after the gas consumption is stopped in the event that the pressure in the product vaporizer is below the set point of liquid regulator  17  (and thus liquid regulator  17  is open). 
       FIG.  10    illustrates an additional embodiment of the current disclosure, wherein cryogenic tank system  226  uses a loop  19  before the product vaporizer  12 . The cryogenic tank system  226  can include all of the features of cryogenic tank system  200 , but also includes the loop before the product vaporizer  12 . Notably, in the embodiment of  FIG.  10   , the loop  19  features a peak portion that physically rises above the product vaporizer  12 . As illustrated in  FIG.  10   , the vapor line  450  is attached to this peak portion of the loop. This embodiment, which may be desirable in some applications of the technology of the disclosure, prevents a portion of the liquid from the tank and line  350  from flowing simultaneously into line  450  as the remaining portion travels to the product vaporizer  12 . Such flow into line  450  would result in flow to the headspace of the tank so that line  450  would act as a pressure building circuit, which is undesirable. 
       FIGS.  11  and  12    illustrate a first and second gas delivery functions for the cryogenic tank system  226 .  FIG.  11    shows the gas path from the headspace of the cryogenic tank  203  to use outlet  250  and the use device or process when the liquid regulator  17  is closed, indicated in general by the arrows at  452 .  FIG.  12    shows the liquid path from cryogenic tank  203  through the open liquid regulator  17  and vaporizer  12  to the use outlet  250  and the use device or process, indicated in general by the arrows at  352 . As noted previously, loop  19  provides an additional structure to ensure that the liquid withdrawn from the cryogenic tank through line  350  does not flow into the gas line  450  through valve  32 . 
       FIG.  13    illustrates an additional embodiment of the current disclosure, where cryogenic tank system  227  uses a check valve  18  along line  350  along with the loop structure  19  of  FIGS.  10 - 12   . The cryogenic tank system  227  can include all of the features and functionality of cryogenic tank system  226  of  FIGS.  10 - 12   , but with the additional check valve  18 , the functionality of which is described above with respect to  FIG.  9   . As further described with respect to  FIG.  9   , in another alternative embodiment of the system of the disclosure, the valve  10  of  FIG.  13    may be a globe check valve (and check valve  18  omitted). 
     While the preferred embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the disclosure, the scope of which is defined by the following claims.