Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C7/00—Methods or apparatus for discharging liquefied, solidified, or compressed gases from pressure vessels, not covered by another subclass
  • F17C7/02—Discharging liquefied gases
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C5/00—Methods or apparatus for filling containers with liquefied, solidified, or compressed gases under pressures
  • F17C5/02—Methods or apparatus for filling containers with liquefied, solidified, or compressed gases under pressures for filling with liquefied gases
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
  • F17C2227/01—Propulsion of the fluid
  • F17C2227/0107—Propulsion of the fluid by pressurising the ullage
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
  • F17C2250/04—Indicating or measuring of parameters as input values
  • F17C2250/0404—Parameters indicated or measured
  • F17C2250/043—Pressure
  • F17C2250/0434—Pressure difference
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
  • F17C2250/06—Controlling or regulating of parameters as output values
  • F17C2250/0605—Parameters
  • F17C2250/0626—Pressure

Definitions

• the present invention relates to a method for regulating the pressure of a cryogenic fluid reservoir connected to an installation consuming this fluid, which reservoir contains, under a storage pressure greater than atmospheric pressure, a cryogenic fluid in the liquid phase at the bottom of the tank and in the gaseous phase at the top of the tank, this tank being adapted to supply the consumer installation with liquid withdrawn from the bottom of the tank, as well as to be supplied from the outside with fluid. It also relates to such a reservoir.
• the invention applies very particularly to so-called “low storage pressure” tanks, that is to say the maximum pressure reached at the top of the tank is generally less than about 4 bars, the pressure indicated here and the pressures indicated below being in absolute bars.
• Such reservoirs are commonly used to store a cryogenic fluid, that is to say a fluid which, at atmospheric pressure is liquid at a temperature much below 0 ° C. They are connected to at least one consumer installation, such as a tunnel for freezing food products.
• the storage pressure of the tank being higher than atmospheric pressure, the opening of a valve placed on the pipe connecting the tank to the consuming installation causes the liquid to move from its point of drawing to its point of use, without forced drive and despite the pressure drops.
• the pressure of the gas is conventionally regulated at the top of the tank so that this pressure remains substantially equal to a predetermined value , fixed, generally of the order of 2 to 3 bars.
• the pressure of the liquid at the bottom of the tank varies depending on the height of the liquid inside the tank, so that, as the liquid level drops, the pressure of the withdrawn liquid drops and tends to get closer to the gas pressure at the top.
• a liquid height of about 10 meters implies a differential of pressure of the order of 0.6 bar between the gas pressure at the top and the liquid pressure at the bottom of the tank, at the level of the draw-off.
• the aim of the present invention is to propose a regulation method which guarantees a substantially constant rate of drawing from the bottom of the tank and which, more generally, improves the storage, supply and withdrawal performance of the cryogenic fluid tank.
• the subject of the invention is a method for regulating the pressure of a cryogenic fluid reservoir as defined above, in which the pressure of the gas at the top of the reservoir is varied according to the operating state of this tank.
• the term “operating state” of the tank should be understood to mean the various phases which it passes through during its use: drawing of liquid causing a drop in level, replenishment of the tank causing a rise in level. , or the stand-by phases of the consuming installation where the tank is therefore at rest.
• the pressure of the liquid maintained at said predetermined value is measured at the point of drawing of the liquid towards the consuming installation; - the pressure of the liquid maintained at said predetermined value is measured at the highest point of altitude along a line connecting the reservoir to the consuming installation; - When liquid is drawn from the tank and the liquid level drops, the liquid taken from the bottom of the tank is vaporized to form gas sent to the top of said tank;
• the invention also relates to a cryogenic liquid reservoir, of the type containing, under a storage pressure higher than atmospheric pressure, a cryogenic fluid in liquid phase at the bottom of the reservoir and in gaseous phase at the top of said reservoir, this reservoir comprising means for connection to an installation consuming the fluid contained in the tank, and means for supplying said fluid from the outside, said tank comprising both means for pressurizing the gas at the top of the tank, means evacuation to the outside of said gas, and a control unit of said pressurizing and evacuation means according to the operating state of this tank.
• a nitrogen tank 1 containing liquid nitrogen at the bottom, also called “tank”, and nitrogen gas at a pressure of about 2 bars at the top, also called “head” .
• the liquid level inside the tank is marked with the reference N.
• the bottom of the tank 1 is connected to a consuming installation 2, for example a freezing tunnel, via a connection pipe 3 provided with a closing valve. 4.
• the point of connection of the pipe 3 to the tank 1, which is denoted P, is commonly called “drawing point”.
• the tank 1 includes means 5 for pressurizing the gas at the top of the tank.
• These means 5 comprise a line 6 connecting the bottom of the tank to its top, and is provided, from upstream to downstream, with an apparatus 7 for measuring the pressure of liquid nitrogen, for example a manometer, with a closing valve 8 (preferably a solenoid valve) and a vaporizer 9.
• the tank 1 also includes means 10 for venting the gas at the top of the tank.
• These means 10 comprise a line 11 for evacuation to the outside, provided upstream downstream of a pressure gauge 12, a closing valve 13 and possibly an air exhaust member not shown, commonly called "silent".
• a unit 15, ensuring the control of the means 5 for pressurizing the crown, as well as the means 10 for venting the crown, is connected, for example by electrical connections, on the one hand to the pressure measuring devices 7 and 12, and on the other hand to the valves 8 and 13.
• the control unit 15 is thus adapted, on the one hand, to know, continuously or at regular intervals, the pressure of liquid nitrogen at bottom of tank 1 and nitrogen gas at the top of this tank and, on the other hand, to compare the value of the pressure at the bottom with a predetermined value chosen, modifiable by the user.
• the unit 15 is also able to control the opening, total or partial, as well as the closing of the valves 8 and 13 so as to regulate the pressures of the bottom and the top of the tank 1, as will be explained in detail below. .
• Means 16 for supplying nitrogen are also provided, so as to regularly, possibly continuously, supply liquid nitrogen to the tank 1.
• these means 16 comprise a supply line 17 through the bottom of the tank 1 allowing a filling said to be "at source”, and possibly a supply line 18 through the top of the tank allowing filling said to be "in rain”.
• the reservoir 1 also includes an overflow member 19 known per se, intended to limit the height of the liquid inside the reservoir.
• the level of the liquid N is shown at its maximum. Illustrated in this figure is the example of a 50,000 liter tank, giving rise to a height N of about 10 meters, which in such a case creates a pressure differential between the top and the bottom of the tank. about 0.6 bar.
• the operation of the reservoir 1, the pressure of which is regulated according to the invention, is as follows:
• the latter is in the state described above, that is to say that the gas pressure at the top is substantially equal to 2 bars and that the pressure of liquid at the draw point P is approximately 2.6 bars.
• the predetermined pressure value stored in the control unit 15 is chosen to be substantially equal to 2.6 bars.
• control unit 15 keeps the liquid pressure at the draw-off point P substantially constant, throughout the nitrogen withdrawal period.
• the flow rate of the line 3 connecting to the consuming installation 2 thus remains substantially constant, limiting the operating disturbances of this installation 2.
• the tank 1 When the tank 1 is supplied (or replenished) with liquid nitrogen, for example by filling at source, the liquid level inside the tank 1 increases, causing a corresponding increase in the gas pressure at the top of the tank.
• the unit 15 detects, through the measurements of the pressure gauge 7, an increase in pressure, and then controls the opening of the vent valve 13, this which decreases the gas pressure at the top and, therefore, that of liquid at the bottom of the tank.
• the unit 15 maintains the opening of the valve 13 as long as the liquid pressure at the bottom of the tank remains above the aforementioned predetermined value.
• the regulation of the reservoir 1 is substantially similar when the supply of liquid nitrogen is carried out from the top.
• Source filling is however preferred to rain filling, the latter tending on the one hand to reduce the gas pressure more significantly, and on the other hand to heat the liquid.
• the control unit 15 is adapted to improve the capacity for conserving the frigories of the stored liquid. To do this, when the container 1 is not requested to be drawn off and will not be a priori for a period of several hours (for example at night), the unit 15 controls the total opening of the shut-off valve. air 13. The gas pressure at the top of the tank then changes from a storage value of approximately 2 bars to substantially atmospheric pressure (residual pressure of a few hundred grams). In this state, the reservoir 1 is no longer able to supply the installation 2, the movement of the fluid inside the pipe 3 no longer being ensured.
• the unit 15 controls the re-pressurization of the top of the tank, via the means 5, until the liquid pressure at the bottom of the tank reaches the aforementioned predetermined value.
• the measurement of the liquid pressure is not carried out, as previously, substantially at the level of the point of drawing of the liquid, but is carried out at the level of the highest altitude point along the line 3 of connection between the tank 1 and the consuming installation 2.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (7)

Cited By (3)

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• 2002
  • 2002-07-05 FR FR0208449A patent/FR2841963B1/fr not_active Expired - Fee Related
• 2003
  • 2003-06-24 AT AT03762706T patent/ATE453829T1/de not_active IP Right Cessation
  • 2003-06-24 AU AU2003260622A patent/AU2003260622B2/en not_active Ceased
  • 2003-06-24 CA CA2491022A patent/CA2491022C/fr not_active Expired - Fee Related
  • 2003-06-24 EP EP03762706A patent/EP1521933B1/de not_active Expired - Lifetime
  • 2003-06-24 DE DE60330777T patent/DE60330777D1/de not_active Expired - Lifetime
  • 2003-06-24 WO PCT/FR2003/001938 patent/WO2004005791A2/fr not_active Ceased

Non-Patent Citations (1)

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