(19)
(11)EP 2 772 677 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
24.07.2019 Bulletin 2019/30

(21)Application number: 14157104.2

(22)Date of filing:  27.02.2014
(51)International Patent Classification (IPC): 
F17C 7/02(2006.01)

(54)

Bulk cryogenic liquid pressurized dispensing system and method

Sammel-Kryoflüssigkeitsausgabesystem und Verfahren

Système de distribution pressurisée de liquide cryogénique en vrac et procédé


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 01.03.2013 US 201313782922

(43)Date of publication of application:
03.09.2014 Bulletin 2014/36

(73)Proprietor: Chart Industries, Inc.
Ball Ground GA 30107 (US)

(72)Inventors:
  • Drube, Paul
    Ball Ground, Georgia 30107 (US)
  • Neeser, Timoty
    Ball Ground, Georgia 30107 (US)
  • Stousland, Tyler
    Ball Ground, Georgia 30107 (US)

(74)Representative: Stafford, Jonathan Alan Lewis et al
Marks & Clerk LLP 1 New York Street
Manchester M1 4HD
Manchester M1 4HD (GB)


(56)References cited: : 
EP-A2- 2 453 160
US-A- 4 888 955
US-A1- 2003 126 867
WO-A2-2004/005791
US-A- 5 590 535
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] This application is a continuation-in-part of U.S. Patent Application No. 13/216,666, filed August 24, 2011, currently pending.

    [0002] The present invention generally relates to systems for storing and dispensing fluids and, more particularly, to a bulk cryogenic liquid pressurized dispensing system and method.

    [0003] WO2004/005791 A2 discloses a system for dispensing a cryogenic liquid.

    [0004] It is well known that cryogenic liquids, or liquids having similar properties, have found great use in industrial refrigeration and freezing, cryo-biological storage repository and lab test applications. Cryogenic liquids are typically stored in thermally insulated bulk tanks which consist of an inner vessel mounted inside, and thermally isolated from, an outer vessel. The liquid is then directed from the tank through thermally isolated pipes to a supply point where it is used for a variety of applications such as industrial, medical, or food processing.

    [0005] Prior art bulk tanks typically use a pressure regulator at the top of the bulk tank. Such a system is limited in its flexibility. When the tank is full there is a certain amount of liquid head pressure. This head pressure is added to the tank vapor pressure and this is the supply pressure out of the tank. For some applications it may be important to maintain a constant supply pressure. As the liquid level in the tank drops from usage the vapor pressure in the tank needs to increase to compensate for the decrease in head pressure.

    [0006] A mechanical pressure regulator is set to open when the pressure in the bulk tank drops below a set point and closes when it rises above the set point. The regulator is usually set to provide enough pressure inside the tank to operate at low liquid levels. This means that the supply pressure will be higher when the tank is full and drop off as the liquid level drops. As a result, a user may experience product losses or loss in efficiency near the bottom of the tank. This is not ideal for high flow rates where the condition of the supplied cryogenic liquid is important.

    [0007] Failure to install a properly designed system for storing and dispensing cryogenic liquid with consistent quality causes wasted energy in lost cooling power. The poor control of the liquid conditions allows the outlet pressure to fluctuate so wildly that many times customers cannot utilize the lower one-third of the tank's capacity. The primary culprit of this complaint stems from a reduction in tank outlet pressure (tank vapor + liquid head pressure) at the liquid withdrawal point. This leads to a reduction in liquid flow rate at the application and as a result, inconsistent cooling.

    [0008] In applications such as food freezing where the product is moving at a specified rate in the tunnel, it's critical that the quality of the cryogenic liquid being dispensed is consistent so the process can be tuned for maximum production throughput. If it becomes out of tune from liquid conditions changing at the application, the only recourse a plant manager has control over (other than slowing down production) is to call their liquid supplier and expedite the tank refill in order to restore the liquid to pre-tuned conditions. Not only is this an emergency delivery, but it's usually before the desired refill point so the tank can't take a full trailer load. The fresh liquid resolves the problem because it is usually colder and lowers the overall liquid saturation pressure, but more importantly, the pressure at the bottom of the tank is increased so the tuned liquid nitrogen flow rate is restored. A simple electrical analogy is like a voltage outage has just been restored. The cryogenic food freezer, like any electrical appliance wants to run on a constant supply pressure or voltage, so the liquid nitrogen flow rate or amperage draw remains constant.

    [0009] A need therefore exists for a bulk cryogenic liquid pressurized dispensing system and method that addresses the above issues.

    [0010] A first aspect of the present invention provides a system for dispensing a cryogenic liquid according to claim 1.

    [0011] The system may further comprise a liquid fill line in communication with the interior of the bulk tank via a fill line adapted to be connected to a source of liquid for refilling the bulk tank. The system may further comprise a fill vent line in communication with the top portion of the interior of the bulk tank, said fill vent line having a distal end adapted to be connected to the source of liquid during refilling of the bulk tank.

    [0012] The cryogenic liquid may be liquid nitrogen.

    [0013] The system may further comprise a baffle positioned in the bottom portion of the interior of the bulk tank.

    [0014] In the system according to the first aspect, the saturation pressure sensor may include a pressure bulb.

    [0015] The liquid dispensing line may be insulated.

    [0016] The pressure builder may have a first stage and a second stage. The first stage of the pressure builder may include a plurality of parallel heat exchangers. The second stage of the pressure builder may include a plurality of series heat exchangers.

    [0017] In the system of the first aspect, the bulk tank may be insulated.

    [0018] The system of the first aspect may further comprise:

    i. a pressure builder outlet line in communication with the outlet of the pressure builder and the top portion of the interior of the bulk tank; and

    j. a vent line in communication with the pressure builder outlet line, said vent line including the vent valve.



    [0019] The controller may be a programmable logic controller.

    [0020] A second aspect of the present invention provides a method of dispensing cryogenic liquid at a generally constant pressure according to claim 9.

    [0021] The cryogenic liquid may be liquid nitrogen.

    [0022] Step g. may include opening a pressure builder valve.

    [0023] Step g. may include opening a vent valve.

    [0024] A third aspect also disclosed herein is a system for dispensing a cryogenic liquid comprising:
    1. a. a bulk tank defining an interior that is adapted to contain a supply of the cryogenic liquid;
    2. b. a pressure builder having an inlet in communication with a bottom portion of the interior of the bulk tank and an outlet in communication with a top portion of the interior of the bulk tank;
    3. c. a liquid dispensing line in communication with the bottom portion of the interior of the bulk tank;
    4. d. a liquid level sensor adapted to detect a level of a supply of cryogenic liquid contained within the interior of the bulk tank;
    5. e. a vapor pressure sensor in communication with the top portion of the interior of the bulk tank and adapted to measure a vapor pressure above a supply of cryogenic liquid contained within the interior of the bulk tank;
    6. f. an outlet liquid temperature sensor in communication with the liquid dispensing line and adapted to measure an outlet liquid temperature of cryogenic liquid flowing there through;
    7. g. a tank liquid temperature sensor in communication with the bottom portion of the interior of the bulk tank;
    8. h. a pressure building valve in circuit between the bottom portion of the interior of the bulk tank and the inlet of the pressure builder;
    9. i. a vent valve in communication with the top portion of the interior of the bulk tank; and
    10. j. a controller in communication with the liquid level sensor, the vapor pressure sensor, the outlet liquid temperature sensor, the tank liquid temperature sensor, the pressure builder valve and the vent valve, said controller programmed to control operation of the pressure builder valve and the vent valve based on data from the sensors so that cryogenic liquid flowing through the dispensing line is maintained at a generally constant pressure.


    [0025] The liquid level sensor may be a differential pressure gauge in communication with the top and bottom portions of the interior of the bulk tank.

    [0026] The tank liquid temperature sensor may be a saturation pressure sensor. The saturation pressure sensor may include a pressure bulb.

    [0027] A fourth aspect also disclosed herein is a method of dispensing cryogenic liquid at a generally constant pressure comprising the steps of:
    1. a. providing a bulk tank;
    2. b. storing cryogenic liquid in the bulk tank;
    3. c. providing a liquid dispensing line in communication with the bulk tank;
    4. d. flowing cryogenic liquid through the dispensing line;
    5. e. detecting a liquid level of the cryogenic liquid in the bulk tank;
    6. f. detecting a vapor pressure above the cryogenic liquid in the bulk tank;
    7. g. detecting a tank liquid temperature of the cryogenic liquid in the bulk tank;
    8. h. detecting an outlet liquid temperature of the cryogenic liquid flowing through the dispensing line; and
    9. i. vaporizing liquid from a bottom portion of the bulk tank and directing it to a top portion of the bulk tank and venting vapor from the top portion of the bulk tank based on the detected liquid level, detected vapor pressure, detected tank liquid temperature and detected outlet liquid temperature.


    [0028] Detecting the tank liquid temperature may include detecting a saturation pressure in the bottom portion of the bulk tank

    [0029] Non-limiting embodiments of the present invention will now be described with reference to some of the following figures, in which:

    Figs. 1A-1C, not according to the invention, are schematic views illustrating a liquid CO2 tank filled, approximately half full and in need of refilling, respectively;

    Fig. 2 is a perspective view of an alternative embodiment of the baffle of the system of the present invention;

    Fig. 3 is a graph illustrating improvements in snow yield v. temperature possible with the system of Figs. 1A-1C;

    Fig. 4 is a perspective view showing an alternative embodiment of the heat exchanger coil of the system and method of Figs. 1A-1C;

    Fig. 5 is a side elevational view of the heat exchanger coil of Fig. 4;

    Fig. 6 is a schematic view illustrating an embodiment of the system of the invention;

    Fig. 7 is a graph illustrating how the outlet pressure of the system of Fig. 6 stays generally constant in accordance with an embodiment of the method of the invention;

    Fig. 8 is a flow chart illustrating the processing performed by the programmable logic controller of the system of Fig. 6 in controlling the vent valve in accordance with an embodiment of the system and method of the invention;

    Fig. 9 is a flow chart illustrating the processing performed by the programmable logic controller of the system of Fig. 6 in controlling the pressure building valve in accordance with an embodiment of the system and method of the invention;

    Fig. 10 is a schematic view illustrating an embodiment of the system of the invention;

    Fig. 11 is a flow chart illustrating the processing performed by the programmable logic controller of the system of Fig. 10 in controlling the vent valve in accordance with an embodiment of the system and method of the invention;

    Fig. 12 is a flow chart illustrating the processing performed by the programmable logic controller of the system of Fig. 10 in controlling the pressure building valve in accordance with an embodiment of the system and method of the invention.



    [0030] A system, indicated in general at 10 in Figs. 1A-1C includes a bulk tank, indicated in general at 12, that includes an inner tank 14 surrounded by outer jacket 16. The tank preferably is vertically oriented, being sized so as to have a height that is greater than the width of the interior 17 of the inner tank 14. Inner tank 14 is preferably sized to hold a reservoir of liquid having a depth of at least 1.82 m (6 feet). The annular insulation space 18 defined between the inner tank 14 and outer jacket 16 may be vacuum-insulated and/or at least partially filled with an insulation material so that inner tank 14 is insulated from the ambient environment. As an example only, the insulation material may include multiple layers of paper and foil that are preferably combined with the vacuum insulation in the annular insulation space.

    [0031] When used for food freezing and/or refrigeration processes, the inner tank 14 is preferably constructed of grade T304 stainless steel (food grade). Such an inner tank provides operating temperatures down to -196°C (-320°F). at pressures of around 25,1 bar a (350 psig). Outer jacket 16 is preferably constructed of high grade carbon steel. Pre-existing tanks could be retrofitted with stainless steel inner tanks for use in food processing applications of the present invention.

    [0032] While the invention will be described below in terms of liquid carbon dioxide for use in food refrigeration and/or freezing processes, it should be understood that the invention may be used for other liquids useful in refrigeration and/or freezing related processes, including cryogenic liquids.

    [0033] As illustrated in Figs. 1A-1C, the inner tank 14 features a top portion 19 to which a fill vent line 20 is connected. In addition, a liquid fill line 22 is connected to a lower portion of the inner tank 14, as will be described in greater detail below. The distal end of the fill vent line 20 is provided with a fill vent valve 24 while the distal end of the liquid fill line 22 is provided with liquid fill valve 26, and both are adapted to be connected to a source of liquid, such as a tanker truck, for refilling the bulk tank. The fill vent line 20 provides a vapor balance during the refilling operation.

    [0034] A baffle 30 is positioned within the lower portion of the interior tank 14. The baffle is preferably constructed of stainless steel and has a thickness of approximately 2,7 mm (0.105 inches). The baffle features a shallow cone shape and is circumferentially secured to the interior surface of the inner tank 14. The baffle features a number of openings 32 that permit passage of liquid. The functionality of the baffle will be explained below.

    [0035] An internal heat exchanger coil 34 is positioned in the bottom portion 35 of the tank and is connected by coil inlet line 36 to a refrigeration system 38. A coil outlet line 42 joins the internal heat exchanger coil 34 to the refrigeration system 38 as well. Coil inlet line 36 optionally includes a coil inlet valve 44 while coil outlet line 42 optionally includes a coil outlet valve 46.

    [0036] While a single coil heat exchanger is indicated at 34 in Figs. 1A-1C, the heat exchanger could alternatively feature a number of coils, connected either in series or in parallel or both. For example, an alternative embodiment of the heat exchanger coil 34 is indicated in general at 45 in Figs. 4 and 5. As indicated in Figs. 4 and 5, the heat exchanger 45 includes four coils 47a, 47b, 47c and 47d connected in parallel with an inlet 49 and an outlet 51. Alternatively, coils 47a-47d could be connected in series. As another example, the heat exchanger coil may include two or more concentric coils connected in parallel or in series.

    [0037] A liquid dispensing or feed line 52 exits the bottom 53 of the inner tank 14 and is provided with liquid feed valve 54 and liquid feed check valve 56.

    [0038] A pressure builder inlet line 60 also exits the bottom portion of the inner tank 14 and connects to the inlet of pressure builder 62. The pressure builder inlet line 60 is provided with a pressure builder inlet valve 64, and automated pressure builder valve 66 and a pressure builder check valve 68. A pressure builder outlet line 72 exits that pressure builder 62 and travels to the top of the inner tank 14. The pressure builder outlet line 72 is provided with a pressure switch 74 and a pressure builder outlet valve 76. As will be explained in greater detail below, the pressure switch 74 is connected to the automated pressure builder valve 66.

    [0039] In operation, with reference to Fig. 1A, after the tank 12 has been filled, the inner tank 14 contains a supply of liquid CO2 80 with a headspace 82 defined above. Fill valves 24 and 26, feed valve 54 and automated pressure builder valve 66 are closed, while coil inlet and outlet valves 44 and 46 and pressure builder inlet and outlet valves 64 and 76 are open. While the description below assumes that the feed valve 54 is closed, it may be open in alternative modes of operation, also described below. As an example only, the refill transport provides the liquid CO2 at a pressure of approximately 19,6 bar a (270 psig), and a temperature of approximately -23°C (-10°F).

    [0040] The pressure switch 74 senses the pressure in headspace 82 via pressure builder outline line 72. If the pressure is below the target pressure of 21,7 bar a (300 psig), the pressure switch 74 opens automated pressure builder valve 66 so that liquid CO2 flows to the pressure builder 62. The liquid CO2 is vaporized in the pressure builder and the resulting gas travels through line 72 to the headspace 82 so that the pressure in inner tank 14 is increased. Pressure builder check valve 68 prevents burp backs through the pressure builder inlet line 60 and into the bottom of the tank that could cause undesirable mixing between the liquid CO2 below the baffle and the remaining liquid CO2 above the baffle. Pressure building continues until pressure switch 74 detects the target pressure of 21,7 bar a (300 psig) in the inner tank 14. When the pressure switch detects the pressure of 21,7 bar a (300 psig), will close the automated pressure builder valve 66 so that pressure building is discontinued. At this pressure, the liquid CO2 80 will have an equilibrium temperature of approximately 0°F.

    [0041] The bottom portion of the tank is provided with a temperature sensor 90, such as a thermocouple, that communicates electronically with a temperature controller 92. Sensor 90 can alternatively be a pressure sensor or a saturation bulb. The temperature controller 92 controls operation of the refrigeration system 38 and may be a microprocessor or any other electronic control device known in the art. When the temperature controller detects, via the temperature sensor, a temperature that is higher than the desired or target temperature, it activates the refrigeration system 38. Continuing with the present example, the temperature sensor detects the -18°C (0°F) temperature of the liquid CO2 in the inner tank and activates the refrigeration system 38. A refrigerant fluid in liquid form then travels through line 36 to the internal heat exchanger coil 34 and is vaporized so as to subcool the liquid CO2 in the bottom portion of inner tank 14. The vaporized refrigerant fluid travels back to the refrigeration system 38 via line 46 for regeneration. More specifically, the refrigeration system 38 includes a condenser for re-liquefying the refrigerant fluid. As an example only, the refrigerant fluid is preferably R-404A/R-507.

    [0042] The refrigeration system and internal heat exchanger coil continue to subcool the liquid CO2 in the bottom portion of the inner tank until the target temperature, -40°C (-40°F) for example, is reached. The temperature controller 92 senses that the target temperature has been reached, via the temperature sensor 90, and shuts down the refrigeration system 38.

    [0043] Due to stratification in the inner tank and the baffle 30, even though the liquid CO2 below the baffle has been subcooled, the pressure remains at 300 psig for pushing the liquid CO2 from the tank during dispensing. The headspace 82 preferably operates at 21,7 bar a (300 psig) to allow direct replacement of older systems so as not to alter the food freezing equipment set up for 21,7 bar a (300 psig). More specifically, stratification occurs throughout the liquid CO2 80 between the CO2 gas in the headspace 82 of the inner tank and the subcooled liquid CO2 in the bottom portion of the tank. The baffle assists in the stratification by creating a cold zone in the bottom of the tank that is mostly insulated from the remaining liquid CO2 above the baffle. This improves the efficiency of the internal heat exchanger coil in subcooling the liquid beneath the baffle and inhibits migration of the subcooled liquid into the warmer liquid above the baffle. As a result, the tank holds an inventory of high pressure equilibrium liquid CO2 in the region above the baffle, similar to that available from a conventional high pressure storage vessel, and an inventory of high pressure, subcooled liquid CO2 in the region or zone below the baffle.

    [0044] As an example only, for a tank having an inner tank height of 8,83 m (29 feet), and an inner tank width of 8 feet, the baffle 30 would ideally be positioned 2,13 m (7 feet) from the bottom of the tank. In general, the baffle 30 is preferably positioned approximately 24% of the total height of the inner tank from the bottom of the inner tank or at a level where approximately 30% of the tank volume is below the baffle.

    [0045] When the tank target pressure and target subcooled liquid temperature have been reached, the liquid feed valve 54 may be opened so that the subcooled liquid CO2 may be dispensed through feed line 52 and expanded at atmospheric pressure to make snow or otherwise used for a food freezing or refrigeration process. In an alternative mode of operation, the liquid feed valve 54 may be left open during filling for operation of the system during filling or prior to full refrigeration at a reduced efficiency. Check valve 56 prevents burp backs through the feed line 52 and into the bottom of the tank that could cause undesirable mixing between the subcooled liquid CO2 and the remaining liquid CO2 above the baffle.

    [0046] As illustrated in Fig. 1A, the liquid feed line 52 is provided with a pressure relief check valve 94 that communicates with fill vent line 20 via liquid feed vent line 95. In the event that the pressure within the feed line 52 rises above a predetermined level, the pressure relief valve 94 automatically opens so that pressure is vented through line 20.

    [0047] As illustrated in Fig. 1B, the level of the liquid CO2 80 drops as liquid CO2 is dispensed through feed line 52. As this occurs, liquid CO2 travels from the region above the baffle 30, through the openings 32 of the baffle, and into the zone below the baffle. Temperature sensor 90 constantly monitors the temperature of the liquid CO2 in the zone below baffle 32 and pressure switch 74 constantly monitors the pressure within the head space 82 above the liquid CO2. The pressure switch opens the automated pressure building valve 66 as is necessary to maintain and hold the tank operating pressure at approximately 21,7 bar a (300 psig) via the pressure builder 62. Temperature sensor 90 and temperature controller 92 similarly activate refrigeration system 38 as is necessary to maintain the temperature of the liquid CO2 in the zone below the baffle at approximately -40°C (-40°F) via the internal heat exchanger coil 34.

    [0048] It should be noted that alternative automated control arrangements known in the art may be substituted for the temperature sensor and controller 90 and 92 and/or the pressure switch and automated pressure building valve 74 and 66. For example, in an alternative embodiment of the system, a single system programmable logic controller (PLC) is connected to a pressure sensor in the head space 82 of the tank and the temperature sensor 90 so as to control operation of the refrigeration system 38 and the pressure builder 62.

    [0049] With reference to Fig. 1C, when the level of liquid CO2 reaches 25% above the baffle 30, dispensing of liquid CO2 through feed line 52 may be halted by closing feed valve 54. In the PLC embodiment, feed valve 54 is automated and a liquid level detector, which is in communication with the PLC, is positioned in the tank. The liquid level detector signals the PLC when the liquid level in the tank reaches the 20% above baffle 30 level, and the PLC then automatically shuts the feed valve 54 and provides a notification to the user, such as an illuminated light or audible warning.

    [0050] It should be noted that liquid may be dispensed to levels lower than 25% above the baffle, but the heat exchanger coil 34 may become less efficient as the liquid level drops lower than the coil.

    [0051] A tanker truck, or other liquid CO2 delivery source, is connected to the fill vent line 20 and the liquid fill line 22 via fill connections 102. Fill vent valve 24 and liquid fill valve 26 are opened so that the inner tank 14 is refilled with liquid CO2.

    [0052] As an alternative to shutting feed valve 54, when the level of liquid CO2 in the tank reaches the level 20% above the baffle, 32, the tanker truck, or other CO2 liquid delivery source, may be connected to fill connections 102, and the dispensing of liquid CO2 may continue uninterrupted. The pressure builder 62 and refrigeration system 38 and coil 34 operate under the direction of the pressure switch 74 and automated pressure building valve 66 and the temperature sensor 90 and temperature controller 92 as described above to maintain the approximate 21,7 bar a (300 psig) pressure and -40°C (-40°F) temperature (below baffle 30) within inner tank 14. As a result, the system permits the delivery of subcooled liquid CO2 to continue uninterrupted.

    [0053] As noted previously, the baffle 30 helps separate the liquid underneath the baffle from the liquid above so that the liquid below is not disturbed. This increases the efficiency in creating and maintaining the subcooled state of the liquid CO2 below the baffle. Positioning the fill line opening 104 of the liquid fill line 22 above the baffle helps prevent the incoming liquid CO2 from disturbing the subcooled liquid CO2 under the baffle, which further aids in increasing efficiency in creating and maintaining the subcooled state of the liquid CO2 below the baffle.

    [0054] An example of a suitable pressure builder 62 is the sidearm CO2 vaporizer available from Thermax Inc. of South Dartmouth, Massachusetts. An example of a suitable refrigeration system 38 is the Climate Control model no. CCU1030ABEX6D2 condensing unit available from Heatcraft Refrigeration Products, LLC of Stone Mountain, Georgia.

    [0055] While the baffle of Figs. 1A-1C is shown to be cone shaped, the baffle alternatively could be provided with a disk shape, as illustrated at 130 in Fig. 2. The baffle 130 is also preferably constructed from stainless steel that is approximately 2,7 mm (0.105 inches) thick and includes openings 132 and 134 to permit liquid CO2 to travel from the upper region of inner tank 114 to the zone or region below the baffle.

    [0056] As yet another alternative embodiment of the baffle, the baffle takes the form of a plurality of glass or STYROFOAM insulation beads, indicated in phantom at 138 in Fig. 1B, that float between upper and lower screens 140 and 142, respectively. The screens may be mounted to ring-like frames that are circumferentially attached to the interior surface of inner tank 13. The bead material is chosen so that the beads have a density which allows them to float on the denser subcooled liquid CO2 up to the level of upper screen 140. The beads are large enough in both size and number that the cross section of the inner tank 14 is generally covered. As a result, the beads form a floating baffle arrangement that creates an insulation layer between the subcooled liquid CO2 below and the remaining liquid CO2 above. In this regard, reference is made to U.S. Patent No. RE35,874.

    [0057] By dispensing subcooled liquid CO2, the present invention improves snow yield when the liquid is expanded to ambient pressure, as illustrated in Fig. 3. More specifically, by subcooling the liquid CO2 in the region or zone below the baffle, the snow yield rises from slightly over 42% for liquid CO2 at equilibrium temperature for -18°C (0°F) to over 52% at equilibrium temperature for -42°C (-43°F). This equates to an increase in refrigeration capacity of the subcooled liquid CO2, which permits faster food throughput in food freezing operations. An example of suitable snow making equipment (snowhorn), which was used to create the data of Fig. 3, is available from Gray Tech Carbonic, Inc..

    [0058] The increase in snow yield and refrigeration capacity of the above system results in less carbon dioxide consumption. As a result, there is less CO2 gas delivered to the environment, which makes the system and method of the invention a "green" technology. In addition, the baffle of the system increases the efficiency of the refrigeration system in subcooling the liquid CO2 below the baffle. This permits smaller, and thus more efficient, compressors to be used in the refrigeration system.

    [0059] An embodiment of the system of the invention is indicated in general at 200 in Fig. 6. Similar to the system 10 of Figs. 1A-1C, the system 200 includes a bulk tank, indicated in general at 212, that includes an inner tank 214 surrounded by outer jacket 216. The tank preferably is vertically oriented, being sized so as to have a height that is greater than the width of the interior 217 of the inner tank 214. The annular insulation space 218 defined between the inner tank 214 and outer jacket 216 may be vacuum-insulated and/or at least partially filled with an insulation material so that inner tank 214 is insulated from the ambient environment. As an example only, the insulation material may include multiple layers of paper and foil that are preferably combined with the vacuum insulation in the annular insulation space.

    [0060] As an example only, bulk tank 212 may range in size from 41,6 m3 to 60,6 m3 (11,000 gallons to 16,000 gallons) and may have a pressure capacity of 13,1 bar a (175 psig). Examples of tank size include 2,89 m (114 inches) in diameter with a height ranging from 11,43 m to 15,24 m (450 inches to 600 inches). When used for food freezing and/or refrigeration processes, the inner tank 214 is preferably constructed of grade T304 stainless steel (food grade). Outer jacket 216 is preferably constructed of high grade carbon steel.

    [0061] While the invention will be described below in terms of liquid nitrogen, it should be understood that the invention may be used for other cryogenic liquids useful in refrigeration and/or freezing related processes, such as industrial, medical or food processing.

    [0062] As illustrated in Fig. 6, the inner tank 214 features a top portion 219 to which a fill vent line 220 is connected. In addition, a liquid fill line 222 is connected to a lower portion of the inner tank 214. The distal end of the fill vent line 220 is provided with a fill vent valve while the distal end of the liquid fill line 222 is provided with liquid fill valve, and both are adapted to be connected to a source of liquid, such as a tanker truck, for refilling the bulk tank. The fill vent line 220 provides a vapor balance during the refilling operation.

    [0063] A liquid dispensing or feed line 252 exits the bottom 253 of the inner tank 214 and is provided with liquid feed valve 254 and liquid feed check valve 256. The dispensing line is also provided with vacuum insulation 257. The dispensing line 252 is constructed to attach directly to a vacuum jacketed house line for delivery of the cryogenic liquid inside the plant.

    [0064] A pressure builder inlet line 260 also exits the bottom portion of the inner tank 214 and connects to the inlet of a high performance pressure builder, indicated in general at 262. As illustrated in Fig. 6, a first stage of the pressure builder features a number of parallel heat exchangers 261. The outlet of the first stage of the pressure builder communicates with the inlet of a second stage of the pressure builder 262 which includes a number of series heat exchangers 263. As an example only, the high performance pressure builder may take the form of the pressure building system disclosed in commonly owned U.S. Patent No. 6,799,429.

    [0065] The first stage of the pressure builder 262 preferably supports withdrawal rates up to 4,5 m3/h (20 GPM) while the second stage of the pressure builder preferably supports demands up to 9,1 m3/h (40 GPM). To support these flow rates, the dispensing line 252 preferably is either 1 ½" or 2" in diameter.

    [0066] The pressure builder inlet line 260 is provided with an automated pressure builder valve 266 and a pressure builder check valve 268. A pressure builder outlet line 272 exits pressure builder 262 and travels to the top of the inner tank 214. The pressure builder outlet line is provided with a vent line 242 which includes an automated vent valve 244.

    [0067] With reference to Fig. 6, after the tank 212 has been filled, the inner tank 214 contains a supply of liquid nitrogen 281 with a headspace 282 defined above.

    [0068] To promote stable liquid withdrawal during a product refill, the system incorporates a low-mounted internal horizontal baffle 230 with a side wall bottom fill designed to direct the incoming liquid up the side of the vessel during bottom filling. The baffle is circumferentially secured to the interior surface of the inner tank 214 by spaced braces. In addition to the spaces between the baffle braces, the baffle features a central opening 232 that permits passage of liquid. The baffle also aides in deflecting unwanted heat from the vessel bottom supports and piping penetrations up the sides of the tank to promote liquid stratification, which keeps the liquid colder at the tank bottom to feed the application.

    [0069] As illustrated in Fig. 6, the system 200 includes a liquid level sensor preferably in the form of a differential pressure gauge 280, which communicates with the head space of the tank interior via low phase line 282 and the bottom of the tank interior via high phase line 284. In addition, a vapor pressure sensor 286 communicates with the headspace of the tank via low phase line 282.

    [0070] In addition, the dispensing line 252 is provided with a liquid outlet temperature sensor 288 while the bottom of the tank interior is provided with a tank liquid temperature sensor that is preferably a saturation pressure sensor 292 that communicates with a pressure bulb 294. The pressure bulb 294 is a capped pipe inside the bottom of the tank surrounded by liquid. Inside the pipe is gaseous nitrogen. The liquid cools the pipe and condenses the gas inside. The pressure inside the pipe is the saturation pressure of the liquid. The pressure sensor 292 is in communication with the interior of the pipe. As will be explained below, the tank liquid temperature may be calculated from the saturation pressure detected by the pressure sensor 292.

    [0071] Liquid level gauge 280, vapor pressure sensor 286, liquid outlet temperature sensor 288 and saturation pressure sensor 292 each communicate with a controller, such as programmable logic controller ("PLC") 300 in Fig. 6. The PLC also communicates with, and controls operation of, automated pressure building valve 266 and automated vent valve 244. An example of a suitable PLC is the Allen-Bradley MicroLogix 830 available from Rockwell Automation, Inc. of Milwaukee, Wisconsin. It should be noted that devices other than a PLC, including, but not limited to, pressure switches, may be used as the controller 300.

    [0072] The PLC performs with the system 200 as a dynamic pressure builder to maintain a constant pressure for the liquid nitrogen flowing through dispensing line 252 by varying the vapor pressure in the tank via the pressure building valve 266 and the vent valve 244. The PLC takes sensor inputs for the liquid level (from differential pressure gauge 280), tank vapor pressure (from vapor pressure sensor 286), and tank temperature (from saturation pressure sensor 292) to calculate when to operate the pressure builder. In addition, the PLC calculates the necessary vapor pressure in order to deliver saturated liquid at the usage point using the liquid outlet temperature detected by sensor 288, in combination with the other data inputs noted above.

    [0073] With regard to tank temperature, the PLC calculates the tank liquid temperature using the saturation pressure from saturation pressure sensor 292.

    [0074] The PLC uses the tank liquid temperature and level of the liquid as well as the pressure of the vapor to calculate the pressure at the bottom of the tank (vapor pressure + liquid head = pressure at the bottom of the tank).

    [0075] Using the liquid outlet temperature detected by sensor 288 in the liquid dispensing line, the PLC 300 determines the required saturation pressure at the outlet and compares it with the pressure at the bottom of the tank calculated above. If the pressure at the bottom of the tank is too low (lower than the required outlet saturation pressure), the PLC will automatically open pressure building valve 266 so that the pressure builder 262 receives liquid from the bottom of the tank and vaporizes it. The vapor travels to the top of the tank via line 272 so as to pressurize it. As described above, stratification of the liquid in the tank and the baffle 230 help isolate the liquid at the bottom of the tank from temperature increases. Conversely, if the pressure at the bottom of the tank is too high (higher than the required outlet saturation pressure), the PLC 300 will open the vent valve 244 to vent vapor from the tank headspace through lines 272 and 242 to the atmosphere to lower the pressure in the tank.

    [0076] In view of the above, the PLC 300 enables the customer to set their requirements using input device 302 (which may be, for example, a computer keyboard or control panel) with very tight parameters (such as +/- 0,2 bar (2 psi)) to operate these two valves. For example, in a typical food freezing application, the pressure builder can be set to 2,7 bar a (25 psig) and the vent at 3,4 bar a (35 psig). These pressure set points are at the bottom of the tank, not at the traditional top vapor space. Not only is the band tighter in comparison to traditional regulators, but the system precisely controls the outlet pressure regardless of the tank liquid level.

    [0077] As illustrated in Fig. 7, the PLC program makes real-time adjustments so as the liquid level falls in normal use, the set point to turn on the pressure builder valve increases to compensate for the loss in liquid head pressure. The result is a generally consistent outlet pressure through the dispensing line 252 to the application regardless of tank liquid level.

    [0078] Flowcharts illustrating examples of the processing performed by the PLC 300 of Fig. 6 are provided in Figs. 8 and 9, where Fig. 8 illustrates processing performed with regard to control of the vent valve 244 and Fig. 9 illustrates processing performed with regard to the pressure building valve 266.

    [0079] The system 200 is designed to run in two different modes, "Optimized" and "Basic." In Optimized mode, which is described above, the PLC 300 does all of the necessary calculations to deliver saturated liquid to the delivery point. The Basic mode is used if the liquid outlet/dispensing line temperature sensor 288 experiences a failure. It is a fall back mode to continue operation with simplified programming. The Basic mode is designed to deliver liquid at a constant outlet pressure (which may not necessarily be saturation pressure) from the tank. Both of these modes operate with the dynamic pressure builder.

    [0080] In Optimized mode, the system has the option to incorporate a "black out" period. In many food freezing applications, a cryogenic liquid supply system will operate for 16 hours and then have an 8 hour period of non-use. This time is used to clean and disinfect the freezing chambers. This time is referred to as the black out period. During the black out period the operator has the opportunity to lower the saturation pressure of the stored liquid if it is necessary. That is, the system incorporates another key feature in its design, the automatic liquid desaturation cycle. If the user has blackout (non-use) time periods programmed into the PLC 300, the vent valve can automatically be directed to open and blow down the tank to conditions to or even below the desired outlet pressure. Once the vent valve closes, the pressure builder can turn on and create the desired amount of sub-cool (the difference between the vapor pressure and the saturation pressure of the liquid). This feature is desirable in applications with erratic usage patterns that cause the liquid to take on heat (from being idle) and for those where consistent liquid quality is critical for the application. This feature is primarily driven by the PLC input from the actual liquid nitrogen temperature in the bottom of the tank (from the saturation pressure sensor 292).

    [0081] To control the outlet pressure at the bottom of the tank during the refill process (which uses vent and refill lines 220 and 222), the driver still follows their normal procedure of adjusting the top and bottom fill valves to hit the "instructed fill target pressure" by monitoring the tank pressure gauge. However, the tank pressure gauge shows the liquid pressure at the bottom of the tank (vapor pressure + liquid head), not the traditional low-phase line vapor pressure. Thus, unknowingly, the driver reduces the vapor pressure as the tank is filling, holding the outlet pressure stable without changing their filling procedure. This also keeps the application on-line and unaffected by a tank refill process.

    [0082] The system of Figs. 6-9 described above therefore is well suited to users who consume large amounts of liquid nitrogen at high flow rates or simply want better control of their liquid supply. The system offers is an excellent alternative to a modified standard bulk tank and provides a more productive solution for such users.

    [0083] An alternative embodiment of the system is illustrated in Figs. 10-12. The system, indicated in general at 400 in Fig. 10, features a construction identical to the system of Fig. 6 with the exceptions described below. As illustrated in Fig. 10, the system 400 includes a tank storage pressure sensor preferably in the form of a pressure sensor 402 which communicates with the liquid space of the tank interior via high phase line 404, which leads from the pressure sensor 402 to the bottom of the tank interior. As a result, the pressure sensor 402 provides the storage pressure of the liquid nitrogen at the bottom portion of the tank (Pbottom).

    [0084] In addition, the bottom of the tank interior is provided with a saturation pressure sensor 406 that communicates with a pressure bulb 408. The pressure bulb 408 may be a capped pipe inside the bottom of the tank surrounded by liquid. Inside the pipe is gaseous nitrogen. The liquid cools the pipe and condenses the gas inside. The pressure inside the pipe is the saturation pressure of the liquid. The pressure sensor 406 is in communication with the interior of the pipe, and thus provides the saturation pressure of the liquid nitrogen (Psat).

    [0085] Storage pressure sensor 402 and saturation pressure sensor 406 each communicate with a controller, such as programmable logic controller ("PLC") 410 in Fig. 10. The PLC also communicates with, and controls operation of, automated pressure building valve 412 and automated vent valve 414. An example of a suitable PLC is the Allen-Bradley MicroLogix 830 available from Rockwell Automation, Inc. of Milwaukee, Wisconsin. It should be noted that devices other than a PLC, including, but not limited to, pressure switches, may be used as the controller 410.

    [0086] The PLC performs with the system 400 as a dynamic pressure builder to maintain a constant pressure for the liquid nitrogen flowing through dispensing line 416 by varying the vapor pressure in the tank via the pressure building valve 412 and the vent valve 414. The PLC 410 takes sensor inputs from the storage pressure sensor 402 and the saturation pressure sensor 406 and compares Pbottom with Psat to determine when to operate the pressure builder. For example, if Pbottom is below Psat, the PLC 410 may open the pressure building valve 412 so that the liquid nitrogen at the bottom of the tank will become subcooled. Alternatively, if the Pbottom rises above Psat, the PLC 410 may open vent valve 414.

    [0087] Flowcharts illustrating examples of the processing performed by the PLC 410 of Fig. 10 are provided in Figs. 11 and 12, where Fig. 11 illustrates processing performed with regard to control of the vent valve 414 and Fig. 12 illustrates processing performed with regard to the pressure building valve 412.

    [0088] While the preferred embodiments of the invention 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 scope of the invention which is defined by the appended claims.


    Claims

    1. A system for dispensing a cryogenic liquid comprising:

    a. a bulk tank (214) defining an interior that is adapted to contain a supply of the cryogenic liquid;

    b. a pressure builder (262) having an inlet (260) in communication with a bottom portion of the interior of the bulk tank (214) and an outlet (272) in communication with a top portion of the interior of the bulk tank (214);

    c. a liquid dispensing line (252) in communication with the bottom portion of the interior of the bulk tank (214);

    d. a storage pressure sensor (402) configured to detect a pressure of a supply of cryogenic liquid contained within a bottom portion of the interior of the bulk tank (214);

    e. a saturation pressure sensor (292, 406) in communication with the bottom portion of the interior of the bulk tank (214) ;

    f. a pressure building valve (266) in circuit between the bottom portion of the interior of the bulk tank (214) and the inlet of the pressure builder (262);

    g. a vent valve (244) in communication with the top portion of the interior of the bulk tank (214); and

    h. a controller (300, 410, PLC) in communication with the storage pressure sensor (402) and the saturation pressure sensor (292, 406), the pressure builder valve (266) and the vent valve (244), said controller (300, 410, PLC) programmed to determine a bottom pressure using data from the storage pressure sensor (402), determine a saturation pressure of the cryogenic liquid, compare the bottom pressure with the saturation pressure and control operation of the pressure builder valve (266) and the vent valve (244) based on data from the storage pressure (402) and saturation pressure sensors (292, 406) so that, as a liquid level of a supply of the cryogenic liquid in the bulk tank (214) falls during dispensing of the cryogenic liquid through the liquid dispensing line (252), a pressure set point to turn on the pressure builder valve (266) increases to compensate for a loss in a liquid head pressure so that cryogenic liquid flowing through the dispensing line (252) is maintained at a constant pressure.


     
    2. The system of claim 1 further comprising a liquid fill line (220) in communication with the interior of the bulk tank (214) via a fill line adapted to be connected to a source of liquid for refilling the bulk tank (214), optionally wherein the system further comprises a fill vent line in communication with the top portion of the interior of the bulk tank (214), said fill vent line having a distal end adapted to be connected to the source of liquid during refilling of the bulk tank (214).
     
    3. The system of claim 1 wherein the cryogenic liquid is liquid nitrogen
     
    4. The system of claim 1: (i) further comprising a baffle (230) positioned in the bottom portion of the interior of the bulk tank (214); and/or (ii) wherein the saturation pressure sensor (292, 406) includes a pressure bulb; and/or (iii) wherein the liquid dispensing line is insulated.
     
    5. The system of claim 1 wherein the pressure builder (262) has a first stage and a second stage, optionally wherein the first stage of the pressure builder (262) includes a plurality of parallel heat exchangers (261) and/or wherein the second stage of the pressure builder (260) includes a plurality of series heat exchangers.
     
    6. The system of claim 1 wherein the bulk tank (214) is insulated.
     
    7. The system of claim 1 further comprising:

    i. a pressure builder outlet line (272) in communication with the outlet of the pressure builder and the top portion of the interior of the bulk tank (214); and

    j. a vent line in communication with the pressure builder outlet line (272), said vent line including the vent valve (244).


     
    8. The system of claim 1 wherein the controller is a programmable logic controller.
     
    9. A method of dispensing cryogenic liquid at a constant pressure comprising the steps of:

    a. providing a bulk tank (214) ;

    b. storing cryogenic liquid in the bulk tank (214) ;

    c. providing a liquid dispensing line (252), in communication with the bulk tank (214) ;

    d. flowing cryogenic liquid through the dispensing line;

    e. detecting a bottom pressure of the cryogenic liquid in the bulk tank (214);

    f. detecting a saturation pressure of the cryogenic liquid in the bulk tank (214); and

    g. comparing the bottom pressure and the saturation pressure;

    h. vaporizing liquid from a bottom portion of the bulk tank (214) and directing it to a top portion of the bulk tank (214) and venting vapor from the top portion of the bulk tank (214) based on the detected bottom and saturation pressures; and

    i. increasing a pressure set point for vaporizing liquid from the bottom portion of the bulk tank (214) as a liquid level of stored cryogenic liquid falls during dispensing of the stored cryogenic liquid.


     
    10. The method of claim 9 wherein the cryogenic liquid is liquid nitrogen.
     
    11. The method of claim 9 wherein step g. includes: (i) opening a pressure builder valve (266); or (ii) opening a vent valve (244).
     
    12. The system of claim 1 wherein the storage pressure sensor (280) is a differential pressure gauge that is also adapted to detect a pressure of a cryogenic vapor in the top portion of the tank and further comprising:

    i. a vapor pressure sensor (286) in communication with the top portion of the tank, said vapor pressure sensor (286) also in communication with the controller (300, PLC);

    j. a liquid outlet temperature sensor (288) in communication with the liquid dispensing line, said liquid outlet temperature sensor (288) also in communication with the controller (300, PLC); and wherein said controller is programmed to determine the bottom pressure using a tank liquid temperature from the saturation pressure sensor (292), a liquid level from the differential pressure gauge (280) and a vapor pressure from the vapor pressure sensor (286) and to determine the saturation pressure using a liquid outlet temperature from the liquid outlet temperature sensor (288).


     


    Ansprüche

    1. Kryoflüssigkeitssausgabesystem, umfassend

    a. einen Sammeltank (214), welcher ein Inneres definiert, welches dazu geeignet ist, einen Kryoflüssigkeitsvorrat zu enthalten;

    b. einen Druckbilder (262), welcher einen Einlass (260) in Kommunikation mit einem unteren Abschnitt des Inneren des Sammeltanks (214) und einen Auslass (272) in Kommunikation mit einem oberen Abschnitt des Inneren des Sammeltanks (214) besitzt;

    c. eine Flüssigkeitsausgabeleitung (252) in Kommunikation mit dem unteren Abschnitt des Inneren des Sammeltanks (214);

    d. einen Speicherdrucksensor (402), welcher konfiguriert ist, um einen Druck eines innerhalb eines unteren Abschnitts des Inneren des Sammeltanks enthaltenen Kryoflüssigkeitsvorrates (214) zu erfassen;

    c. einen Sättigungsdrucksensor (292, 406) in Kommunikation mit dem unteren Abschnitt des Inneren des Sammeltanks (214);

    f. ein Druckbilderventil (266) in einem Kreislauf zwischen dem unteren Abschnitt des Inneren des Sammeltanks (214) und dem Einlass des Druckbilders (262);

    c. ein Entlüftungsventil (244) in Kommunikation mit dem oberen Abschnitt des Inneren des Sammeltanks (214); und

    h. ein Steuergerät (300, 410, PLC) in Kommunikation mit dem Speicherdrucksensor (402) und dem Sättigungsdrucksensor (292, 406), dem Druckbilderventil (266) und dem Entlüftungsventil (244), wobei das Steuergerät (300, 410, PLC) programmiert ist, um einen Bodendruck zu bestimmen, indem es Daten vom Speicherdrucksensor (402) verwendet, einen Sättigungsdruck der Kryoflüssigkeit zu bestimmen, den Bodendruck mit dem Sättigungsdruck zu vergleichen und den Betrieb des Druckbilderventils (266) und des Entlüftungsventils (244) basierend auf Daten vom Speicherdruck- (402) und vom Sättigungsdrucksensor (292, 406) in einer Weise zu steuern, dass, wenn ein Flüssigkeitsspiegel eines Vorrates an Kryoflüssigkeit in dem Sammeltank (214) beim Ausgeben der Kryoflüssigkeit durch die Flüssigkeitsausgabeleitung (252) fällt, ein Drucksollwert zum Einschalten des Druckbilderventils (266) sich erhöht, um einen Abfall in einem Flüssigkeitskopfdruck so zu kompensieren, dass Kryoflüssigkeit, welche durch die Flüssigkeitsausgabeleitung (252) strömt, bei einem konstanten Druck gehalten wird.


     
    2. System nach Anspruch 1, zudem beinhaltend eine Flüssigkeitsfüllleitung (220) in Kommunikation mit dem Inneren des Sammeltanks (214) über eine Füllleitung, welche dazu geeignet ist, mit einer Flüssigkeitsquelle zum Nachfüllen des Sammeltanks (214) verbunden zu werden, wobei optionsweise das System zudem eine Füllentlüftungsleitung in Kommunikation mit dem oberen Abschnitt des Inneren des Sammeltanks (214) beinhaltet, wobei die Füllentlüftungsleitung ein distales Ende besitzt, welches dazu geeignet ist, mit der Flüssigkeitsquelle beim Nachfüllen des Sammeltanks (214) verbunden zu werden.
     
    3. System nach Anspruch 1, bei welchem die Kryoflüssigkeit flüssiger Stickstoff ist.
     
    4. System nach Anspruch 1: (i) zudem beinhaltend eine Umlenkung (230), welche in dem unteren Abschnitt des Inneren des Sammeltanks (214) positioniert ist; und/oder (ii) wobei der Sättigungsdrucksensor (292, 406) einen Druckkolben beinhaltet; und/oder (iii) wobei die Flüssigkeitsausgabeleitung isoliert ist.
     
    5. System nach Anspruch 1, bei welchem der Druckbilder (262) eine erste Stufe und eine zweite Stufe besitzt, wobei optionsweise die erste Stufe des Druckbilders (262) eine Vielzahl von parallelen Wärmetauschern (261) umfasst und/oder wobei die zweite Stufe des Druckbilders (260) eine Vielzahl von Reihen-Wärmetauschern umfasst.
     
    6. System nach Anspruch 1, bei welchem der Sammeltank (214) isoliert ist.
     
    7. System nach Anspruch 1, zudem Folgendes beinhaltend:

    i. eine Druckbilderauslassleitung (272) in Kommunikation mit dem Auslass des Druckbilders und dem oberen Abschnitt des Inneren des Sammeltanks (214); und

    j. eine Entlüftungsleitung in Kommunikation mit der Druckbilderauslassleitung (272), wobei die Entlüftungsleitung das Entlüftungsventil (244) umfasst.


     
    8. System nach Anspruch 1, bei welchem das Steuergerät eine speicherprogrammierbare Steuerung ist.
     
    9. Verfahren zur Ausgabe von Kryoflüssigkeit bei konstantem Druck, folgende Schritte beinhaltend:

    a. Bereitstellen eines Sammeltanks (214);

    b. Speichern von Kryoflüssigkeit in dem Sammeltank (214);

    c. Bereitstellen einer Flüssigkeitsausgabeleitung (252), in Kommunikation mit dem Sammeltank (214);

    d. Strömen von Kryoflüssigkeit durch die Ausgabeleitung;

    e. Erfassen eines Bodendrucks der Kryoflüssigkeit in dem Sammeltank (214);

    e. Erfassen eines Sättigungsdrucks der Kryoflüssigkeit in dem Sammeltank (214); und

    g. Vergleichen des Bodendrucks und des Sättigungsdrucks;

    h. Vernebeln von Flüssigkeit aus einem unteren Abschnitt des Sammeltanks (214) und Leiten davon zu einem oberen Abschnitt des Sammeltanks (214) und Entlüften von Dampf aus dem oberen Abschnitt des Sammeltanks (214), basierend auf dem erfassten Boden- und dem erfassten Sättigungsdruck; und

    i. Erhöhen eines Drucksollwertes zum Vernebeln von Flüssigkeit aus dem unteren Abschnitt des Sammeltanks (214), wenn ein Flüssigkeitsspiegel der gespeicherten Kryoflüssigkeit beim Ausgeben der gespeicherten Kryoflüssigkeit abfällt.


     
    10. Verfahren nach Anspruch 9, bei welchem die Kryoflüssigkeit flüssiger Stickstoff ist.
     
    11. Verfahren nach Anspruch 9, bei welchem Schritt g. Folgendes beinhaltet: (i) Öffnen eines Druckbilderventils (266); oder (ii) Öffnen eines Entlüftungsventils (244).
     
    12. System nach Anspruch 1, bei welchem der Speicherdrucksensor (280) ein Differenzdruckmesser ist, welcher ebenfalls dazu geeignet ist, einen Druck eines Kryodampfes in dem oberen Abschnitt des Tanks zu erfassen, und welches zudem Folgendes beinhaltet:

    i. einen Dampfdrucksensor (286) in Kommunikation mit dem oberen Abschnitt des Tanks, wobei der Dampfdrucksensor (286) ebenfalls mit dem Steuergerät (300, PLC) in Kommunikation steht;

    j. einen Flüssigkeitsauslasstemperatursensor (288) in Kommunikation mit der Flüssigkeitsausgabeleitung, wobei der Flüssigkeitsauslasstemperatursensor (288) ebenfalls mit dem Steuergerät (300, PLC) in Kommunikation steht;
    und wobei das Steuergerät programmiert ist, um den Bodendruck unter Verwendung einer Tankflüssigkeitstemperatur vom Sättigungsdrucksensor (292), eines Flüssigkeitsspiegels vom Differenzdruckmesser (280) und eines Dampfdrucks vom Dampfdrucksensor (286) zu bestimmen, und um den Sättigungsdruck unter Verwendung einer Flüssigkeitsauslasstemperatur vom Flüssigkeitsauslasstemperatursensor (288) zu bestimmen.


     


    Revendications

    1. Système de distribution d'un liquide cryogénique comprenant :

    a. un réservoir en vrac (214) définissant un intérieur qui est conçu afin de contenir une alimentation en liquide cryogénique ;

    b. un système de formation de pression (262) présentant une entrée (260) en communication avec une partie inférieure de l'intérieur du réservoir en vrac (214) ;

    c. une ligne de distribution de liquide (252) en communication avec la partie inférieure de l'intérieur du réservoir en vrac (214) ; et une sortie (272) en communication avec une partie supérieure de l'intérieur du réservoir en vrac (214) ;

    d. un capteur de pression de stockage (402) configuré afin de détecter une pression d'une alimentation de liquide cryogénique contenu dans une partie inférieure de l'intérieur du réservoir en vrac (214) ;

    e. un capteur de pression de saturation (292, 406) en communication avec la partie inférieure de l'intérieur du réservoir en vrac (214) ;

    f. une vanne de formation de pression (266) en circuit entre la partie inférieure de l'intérieur du réservoir en vrac (214) et l'entrée du système de formation de pression (262) ;

    g. une vanne de purge (244) en communication avec la partie supérieure de l'intérieur du réservoir en vrac (214) ; et

    h. un système de commande (300, 410, PLC) en communication avec le capteur de pression de stockage (402) et le capteur de pression de saturation (292, 406), la vanne de système de formation de pression (266) et la vanne de purge (244), ledit système de commande (300, 410, PLC) étant programmé afin de déterminer une pression inférieure en utilisant des données provenant du capteur de pression de stockage (402), de déterminer une pression de saturation du liquide cryogénique, de comparer la pression inférieure avec la pression de saturation et de contrôler le fonctionnement de la vanne de système de formation de pression (266) et de la vanne de purge (244), sur la base de données provenant des capteurs de pression de stockage (402) et de pression de saturation (292, 406) de sorte que, lorsqu'un niveau de liquide d'une alimentation en liquide cryogénique dans le réservoir en vrac (214) chute pendant la distribution du liquide cryogénique à travers la ligne de distribution de liquide (252), un point de consigne de pression permettant d'allumer la vanne de système de formation de pression (266) augmente afin de compenser une perte de la pression de tête de liquide de sorte qu'un liquide cryogénique s'écoulant à travers la ligne de distribution (252) est maintenu à une pression constante.


     
    2. Système selon la revendication 1, comprenant en outre une ligne de remplissage de liquide (220) en communication avec l'intérieur du réservoir en vrac (214) via une ligne de remplissage adaptée afin d'être raccordée à une source de liquide permettant de remplir le réservoir en vrac (214), éventuellement dans lequel le système comprend en outre une ligne de purge de remplissage en communication avec la partie supérieure de l'intérieur du réservoir en vrac (214), ladite ligne de purge de remplissage présentant une extrémité distale adaptée afin d'être raccordée à la source de liquide pendant le remplissage du réservoir en vrac (214).
     
    3. Système selon la revendication 1, dans lequel le liquide cryogénique est un azote liquide.
     
    4. Système selon la revendication 1 : (i) comprenant en outre un déflecteur (230) positionné dans la partie inférieure de l'intérieur du réservoir en vrac (214) ; et/ou (ii) dans lequel le capteur de pression de saturation (292, 406) inclut une ampoule sous pression ; et/ou dans lequel la ligne de distribution de liquide est isolée.
     
    5. Système selon la revendication 1, dans lequel le système de formation de pression (262) présente un premier étage et un second étage, éventuellement dans lequel le premier étage du système de formation de pression (262) inclut une pluralité d'échangeurs de chaleur parallèles (261) et/ou dans lequel le second étage du système de formation de pression (260) inclut une pluralité d'échangeurs de chaleur en série.
     
    6. Système selon la revendication 1, dans lequel le réservoir en vrac (214) est isolé.
     
    7. Système selon la revendication 1, comprenant en outre :

    i. une ligne de sortie de système de formation de pression (272) en communication avec la sortie du système de formation de pression et la partie supérieure de l'intérieur du réservoir en vrac (214) ; et

    j. une ligne de purge en communication avec la ligne de sortie de système de formation de pression (272), ladite ligne de purge incluant la vanne de purge (244).


     
    8. Système selon la revendication 1, dans lequel le système de commande est un contrôleur logique programmable.
     
    9. Procédé de distribution d'un liquide cryogénique à une pression constante comprenant les étapes consistant à :

    a. fournir un réservoir en vrac (214) ;

    b. stocker un liquide cryogénique dans le réservoir en vrac (214) ;

    c. fournir une ligne de distribution de liquide (252), en communication avec le réservoir en vrac (214) ;

    d. faire s'écouler le liquide cryogénique à travers la ligne de distribution ;

    e. détecter une pression inférieure du liquide cryogénique dans le réservoir en vrac (214) ;

    f. détecter une pression de saturation du liquide cryogénique dans le réservoir en vrac (214) ; et

    g. comparer la pression inférieure et la pression de saturation ;

    h. vaporiser un liquide depuis une partie inférieure du réservoir en vrac (214) et la diriger vers une partie supérieure du réservoir en vrac (214) et aérer la vapeur depuis la partie supérieure du réservoir en vrac (214) sur la base des pressions inférieure et de saturation détectées ; et

    i. augmenter un point de consigne de pression afin de vaporiser du liquide depuis la partie inférieure du réservoir en vrac (214) lorsqu'un niveau de liquide du liquide cryogénique stocké tombe pendant la distribution du liquide cryogénique stocké.


     
    10. Procédé selon la revendication 9, dans lequel le liquide cryogénique est un azote liquide.
     
    11. Procédé selon la revendication 9, dans lequel l'étape g. inclut: (i) l'ouverture d'une vanne de système de formation de pression (266) ; ou (ii) l'ouverture d'une vanne de purge (244).
     
    12. Système selon la revendication 1, dans lequel le capteur de pression de stockage (280) est une jauge de pression différentielle qui est également adaptée afin de détecter une pression d'une vapeur cryogénique dans la partie supérieure du réservoir et comprenant en outre :

    i. un capteur de pression de vapeur (286) en communication avec la partie supérieure du réservoir, ledit capteur de pression de vapeur (286) étant également en communication avec le système de commande (300, PLC) ;

    j. un capteur de température de sortie de liquide (288) en communication avec la ligne de distribution de liquide, ledit capteur de température de sortie de liquide (288) étant également en communication avec le système de commande (300, PLC) ;
    et dans lequel ledit système de commande est programmé afin de déterminer la pression inférieure en utilisant une température de liquide de réservoir provenant du capteur de pression de saturation (292), un niveau de liquide provenant de la jauge de pression différentielle (280) et une pression de vapeur provenant du capteur de pression de vapeur (286) et afin de déterminer la pression de saturation en utilisant une température de sortie de liquide provenant du capteur de température de sortie de liquide (288).


     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description