JP6136971B2 - Method and apparatus for mixing cryogenic liquid in storage tank - Google Patents

Description

  The present invention prevents and eliminates stratification of low-temperature liquid generated in a storage tank in which low-temperature liquefied gas (hereinafter referred to as “LNG”) and other low-temperature liquefied gas (hereinafter referred to as “LNG”) are stored. In particular, the present invention relates to a method and apparatus for mixing a cryogenic liquid in a storage tank that prevents and eliminates the stratification by stirring and mixing the cryogenic liquid in the storage tank.

Generally, a cryogenic liquid is a mixture of a plurality of components. For example, LNG contains heavier components than methane such as ethane, propane, and butane in addition to methane as a main component, and the ratio thereof is not constant depending on the production area of LNG and the refining process. Therefore, even if it is the same kind of low-temperature liquid, the density differs depending on the composition.
If cryogenic liquids with different densities are mixed into the cryogenic liquid in the storage tank, the denser cryogenic liquid will settle to the lower layer of the tank, while the lower density cryogenic liquid will be released to the upper layer. As a result, the low-temperature liquid in the storage tank is stratified into a liquid having a low specific gravity (upper layer) and a liquid having a high specific gravity (lower layer).

The cryogenic liquid stored in the storage tank is constantly heated by heat input from the surroundings of the storage tank, but the temperature of the cryogenic liquid is balanced without increasing due to the evaporation from the free liquid surface. doing. The evaporation component at this time is mainly a light component having a low boiling point.
However, when stratification occurs in the low-temperature liquid in the storage tank, the temperature of the upper layer liquid can be evaporated from the free liquid level, so the temperature does not rise, but the lower layer liquid does not have a free liquid level that can be evaporated, so It accumulates inside and the temperature rises. That is, the density of light components increases in the upper layer and the density of the lower layer decreases as the temperature rises. When the density difference between the upper layer and the lower layer becomes smaller than a certain limit value, the stratification cannot be maintained and the upper layer and lower layer liquids are mixed while the lower layer liquid reaches the free liquid level. When the liquid in the lower layer reaches the free liquid level, the energy stored up to that point is released, and the amount of evaporation increases rapidly.

The cryogenic liquid storage tank is equipped with a facility for treating evaporative gas evaporating from the cryogenic liquid. However, when the amount of evaporating gas exceeds its processing capacity, it is dissipated from the safety valve. If the cryogenic liquid is LNG, its evaporative gas is a flammable gas and large amounts of emissions should be avoided for safety. Moreover, if the amount of evaporation increases to exceed the processing capacity of the safety valve, the internal pressure of the storage tank continues to rise, and in the worst case, it may lead to destruction of the storage tank.
Thus, the stratification of the low-temperature liquid in the storage tank is accompanied by a dangerous phenomenon that the amount of evaporation rapidly increases, and therefore means for reliably preventing the stratification is required. As one of the means, the low temperature liquid in the storage tank is agitated and mixed uniformly.

As a technique for performing such stirring and mixing, Patent Document 1 proposes a layering prevention device in a low-temperature liquefied gas tank as shown below.
“In the upper position of the inner bottom of the low-temperature liquefied gas tank, the liquid riser pipe with the lower end as the liquid suction port and the upper end as the liquid outlet is in an upright state, and a space is formed between the tank bottom surface and the liquid suction port. The compressed BOG pipe branched from the downstream side of the BOG compressor provided in the low temperature liquefied gas tank is connected to the lower end of the liquid riser pipe, and the compressed BOG is ejected from the lower end into the liquid riser pipe. And a stratification preventing device in a low-temperature liquefied gas tank, characterized in that the liquid is introduced into the liquid riser pipe ”(see claim 1 of Patent Document 1).

  Further, Patent Document 2 discloses a “stratification elimination device for liquid in a storage tank that is provided in a storage tank that causes liquid stratification in the storage tank due to a change in the physical properties of the receiving liquid, and is close to the bottom of the storage tank on the side wall. A lower mixing nozzle that ejects liquid upwards in the storage tank is disposed at a position, and an intermediate mixing nozzle that ejects liquid upward in the storage tank is disposed at an intermediate position in the vertical direction of the side wall. A device for removing the stratification of the liquid in the storage tank, comprising a circulation pump for taking out the liquid from the storage tank and circulatingly supplying the liquid to the lower mixing nozzle and the intermediate mixing nozzle ”(refer to claim 1 of Patent Document 2). ) Has been proposed.

JP 2000-193196 A Japanese Patent Laid-Open No. 9-203500

The anti-stratification device of Patent Document 1 blows a compressed gas phase into the bottom of a liquid riser installed vertically in a low-temperature liquefied gas tank, and acts as a bubble pump to mix the low-temperature liquefied gas in the low-temperature liquefied gas tank It is.
However, the liquid level in the low temperature liquefied gas tank is not constant. It changes greatly with respect to the liquid level at the time of full liquid, and the change amount reaches several tens of meters in a large tank. If the upper end of the liquid riser is not located near the full height, even if BOG is blown into the lower end of the liquid riser in the low liquid level state, the liquid flows out from the upper end of the liquid riser. Therefore, only the blown BOG will rise in the liquid riser. That is, the circulation mixing effect cannot be exhibited.

In the stratification elimination device of Patent Document 2, the liquid in the storage tank is supplied to the lower mixing nozzle and the intermediate mixing nozzle by a circulation pump and injected into the storage tank. However, the jet flows in the surrounding liquid and diffuses. Therefore, there is a limit to the reaching height. This reaching height is also affected by the density difference between the jet liquid density (heavy) and the ambient liquid density (light), and decreases as the density difference increases.
When the liquid level in the storage tank is high, mixing in the region where the jet does not reach becomes insufficient, so another nozzle is installed at an intermediate height.
However, when the height of the storage tank is high or the density difference is large, the required power of the circulation pump increases to ensure the arrival height of the jet, and at the same time, it may not be sufficient to provide two nozzles. In addition, there is a problem that complicated control for switching the nozzles according to the liquid level and the stratified interface position is required.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a method and apparatus for mixing a cryogenic liquid in a storage tank that can effectively stir and mix the low-temperature liquid in the storage tank with simple equipment. It is said.

(1) The mixing method of the cryogenic liquid in the storage tank according to the present invention is a mixing method of the cryogenic liquid in the storage tank that mixes the cryogenic liquid stored in the storage tank,
An evaporative gas condensing and mixing step of condensing the evaporative gas by mixing the evaporative gas generated in the reserving tank with the low-temperature liquid extracted from the storage tank; and pumping the cryogenic liquid in the liquid pump have a gas-liquid two-phase flow ejection step for ejecting a gas-liquid two phase flow by flash boiling by ejection into a cryogenic liquid in the reservoir,
The evaporative gas condensing and mixing step detects the pressure and temperature of the mixed cryogenic liquid, and adjusts the flow rate of the evaporating gas to be mixed so as to boil under reduced pressure in the gas-liquid two-phase flow ejection step based on the detected pressure and temperature. Is.
(2) Further, in the above (1), the evaporative gas condensation and mixing step detects the pressure and temperature of the mixed cryogenic liquid, and based on this, the mixed cryogenic liquid is brought to a saturation temperature or lower. The flow rate of the evaporative gas is adjusted so as to be.

( 3 ) Further, in the above (1) or (2) , the evaporative gas condensation and mixing step is performed using a venturi type mixing nozzle.

( 4 ) Further, in any one of the above (1) to (3) , the evaporative gas condensing and mixing step is characterized in that the evaporative gas is mixed with a low-temperature liquid by increasing the pressure by a gas compressor. Is.

(5) mixing device storage tank cryogenic liquid according to the present invention, the all off gas generated in the storage tank or the withdrawal evaporated gas extracting a portion tube, withdrawn cryogenic liquid withdrawing cryogenic liquid in the reservoir A pipe, a liquid pump provided in the cryogenic liquid extraction pipe for pumping the cryogenic liquid in the storage tank, and an evaporative gas extracted from the evaporative gas extraction pipe from the cryogenic liquid extraction pipe A condensing and mixing unit that condenses the evaporative gas to be mixed with the low-temperature liquid, a flow rate adjusting valve that adjusts a flow rate of the evaporating gas supplied to the condensing and mixing unit, and the condensing and mixing unit in the storage tank. A cryogenic liquid introduction pipe that introduces a cryogenic liquid whose temperature has risen further into the cryogenic liquid in the storage tank, and a cryogenic liquid that is provided in the cryogenic liquid introduction pipe and is introduced by the cryogenic liquid introduction pipe. A gas-liquid two-phase flow ejection nozzles for ejecting a gas-liquid two phase flow by flash boiling, a pressure gauge for detecting the pressure of the blended cryogenic liquid provided in the cold liquid inlet pipe, provided in the cold liquid inlet pipe A thermometer for detecting the temperature of the mixed cryogenic liquid, and the flow rate adjustment so as to boil under reduced pressure when the gas-liquid two-phase flow jet nozzle is jetted by inputting detection information of the thermometer and the pressure gauge And a control unit for adjusting the valve .
(6) Further, in the above (5), the control unit detects the pressure and temperature of the mixed cryogenic liquid so that the mixed cryogenic liquid becomes a saturation temperature or less based on the detected pressure and temperature. The flow rate adjusting valve is adjusted.

( 7 ) Further, in the above (5) or (6) , the condensing and mixing section is constituted by a venturi type mixing nozzle.

( 8 ) Further, in any of the above (5) to (7), a gas compressor for increasing the pressure of the evaporated gas is provided in the evaporated gas extraction pipe.

  The method for mixing the cryogenic liquid in the storage tank according to the present invention includes an evaporative gas condensing and mixing step of condensing the evaporative gas by mixing the evaporative gas generated in the storage tank with the low-temperature liquid extracted from the storage tank, and the evaporation A gas-liquid two-phase flow jetting step in which a low-temperature liquid whose temperature has risen from the inside of the storage tank by the gas condensation and mixing step is jetted into the low-temperature liquid in the storage tank to be boiled under reduced pressure and jetted as a gas-liquid two-phase flow; Since the bubble-containing liquid in the gas-liquid two-phase state is discharged as a jet into the liquid in the storage tank, the stirring effect of the low-temperature liquid in the storage tank is high.

It is explanatory drawing of the cryogenic liquid mixing apparatus in the storage tank in one embodiment of this invention. It is explanatory drawing of the one aspect | mode of the condensation mixing part which is a part of FIG. It is explanatory drawing containing the partial cross section of the other aspect of the condensation mixing part which is a part of FIG.

Prior to describing the method of mixing the cryogenic liquid in the storage tank of the present embodiment, the cryogenic liquid mixing apparatus in the storage tank used in the method will be described with reference to FIG.
The cryogenic liquid mixing apparatus 1 in the storage tank according to the present embodiment (hereinafter simply referred to as “mixing apparatus 1”) includes an evaporating gas extraction pipe 5 for extracting the evaporating gas (BOG) generated in the storage tank 3, and the storage tank 3 The low-temperature liquid extraction pipe 9 for extracting the low-temperature liquid 7, the liquid pump 11 provided in the low-temperature liquid extraction pipe 9 for pumping the low-temperature liquid 7 in the storage tank 3, and the evaporative gas extracted from the evaporative gas extraction pipe 5 Is brought into contact with the low-temperature liquid 7 extracted from the low-temperature liquid extraction pipe 9 to condense the evaporated gas and mix with the low-temperature liquid 7, and the condensation and mixing unit 13 raises the temperature from the inside of the storage tank 3. A cryogenic liquid introduction pipe 15 for introducing a cryogenic liquid (mixed cryogenic liquid) into the cryogenic liquid 7 in the storage tank 3, and a mixed cryogenic liquid provided in the cryogenic liquid introduction pipe 15 and introduced by the cryogenic liquid introduction pipe 15. Squirt In which by flash boiling and a gas-liquid two-phase flow ejection nozzles 17 for ejecting a gas-liquid two-phase flow in the.
Hereinafter, each configuration will be described in detail.

<Reservoir>
The storage tank 3 stores a low-temperature liquid 7 such as liquefied natural gas (LNG), for example.

<Vapor extraction pipe>
The evaporative gas extraction pipe 5 is a pipe that extracts all or part of the evaporative gas generated in the storage tank 3 and supplies the evaporative gas generated in the storage tank 3 to the outside. Branching from the evaporative gas delivery pipe 21, the other end communicates with the condensing and mixing unit 13.
As shown in FIG. 1, the evaporative gas delivery pipe 21 is provided with a gas compressor 19 that compresses the evaporative gas to increase the pressure. The evaporative gas extracted from the evaporative gas delivery pipe 21 is a gas compressor. After the pressure is increased by 19, all or part of the pressure is supplied to the condensing and mixing unit 13 through the evaporative gas extraction pipe 5.
Further, the evaporative gas extraction pipe 5 is provided with a flow rate adjusting valve 20 so that the flow rate of the evaporative gas supplied to the condensing and mixing unit 13 can be adjusted. The flow rate adjustment by the flow rate adjustment valve 20 is performed by the control unit 22 as described later.

The high pressure by the gas compressor 19 is not essential, and the evaporating gas generated from the storage tank 3 may be supplied to the condensing and mixing unit 13 as it is. In that case, the evaporative gas extraction pipe 5 may be provided by branching from the front side of the gas compressor 19 of the evaporative gas delivery pipe 21, or one end side may be opened above the liquid surface of the cryogenic liquid 7 of the storage tank 3. It may be provided separately from the evaporative gas delivery pipe 21.

<Cryogenic liquid extraction pipe>
The cryogenic liquid extraction tube 9 is a tube for extracting the cryogenic liquid 7 from the storage tank 3. The cryogenic liquid extraction pipe 9 is provided with a liquid pump 11 for pumping the cryogenic liquid 7 to the condensing and mixing unit 13.
As shown in FIG. 1, the cryogenic liquid extraction pipe 9 may be branched from a cryogenic liquid delivery pipe 27 for supplying the cryogenic liquid 7 to the outside, or may be provided separately from the cryogenic liquid delivery pipe 27. Good.
When the cryogenic liquid extraction pipe 9 is branched from the cryogenic liquid delivery pipe 27, a first on-off valve 29 is provided in the vicinity of the branching portion as shown in FIG.

<Condensation mixing section>
The condensing and mixing unit 13 brings the evaporative gas extracted from the evaporative gas extraction pipe 5 into contact with the low temperature liquid 7 extracted from the low temperature liquid extraction pipe 9 to condense the evaporative gas and mix it with the low temperature liquid 7. is there.
As an aspect of the condensing and mixing unit 13, for example, as shown in FIG. 2, the cryogenic liquid 7 and / or the header 31 that can temporarily store the mixed cryogenic liquid is configured, and the evaporative gas is introduced into the lower portion of the header 31. A mouth may be provided.
The evaporative gas introduced into the header 31 contacts the low temperature liquid 7 and is condensed by heat exchange and mixed with the low temperature liquid 7. On the other hand, the low temperature liquid 7 receives heat from the evaporative gas and rises in temperature.

As another aspect of the condensing and mixing unit 13, for example, a venturi type mixing nozzle 33 as shown in FIG. 3 may be used.
The venturi-type mixing nozzle 33 includes a low-temperature liquid inflow path 35 into which the low-temperature liquid 7 flows, a diameter-reduced part 37 on the downstream side of the low-temperature liquid inflow path 35 and a diameter of the flow path, and the vicinity of the diameter-reduced part 37. The evaporative gas suction part 39 into which the evaporative gas is sucked and a discharge port 41 on the downstream side of the evaporative gas suction part 39 from which the mixed low-temperature liquid mixed with the condensed evaporative gas is discharged. Is.

In the venturi-type mixing nozzle 33, the flowing low temperature liquid 7 is increased in flow velocity at the reduced diameter portion 37, and the evaporative gas is sucked from the evaporative gas suction portion 39 by the so-called venturi effect and is entrained in the low temperature liquid 7. By using the venturi-type mixing nozzle 33, the pressure increase range of the gas compressor 19 can be reduced, or the gas compressor 19 itself can be omitted in some cases.
On the other hand, by increasing the pressure of the evaporated gas by the gas compressor 19, in the venturi-type mixing nozzle 33, the flow velocity necessary for entraining the gas phase due to the venturi effect is higher than the ejection speed in the gas-liquid two-phase flow ejection nozzle 17. And small enough. That is, the reduction and enlargement of the flow path cross-sectional area necessary for exhibiting the venturi effect is relatively small, and the pressure loss in the venturi-type mixing nozzle 33 is reduced.

<Cryogenic liquid introduction pipe>
The cryogenic liquid introduction pipe 15 introduces the mixed cryogenic liquid whose temperature has been raised by the condensation mixing unit 13 from the inside of the storage tank 3 into the cryogenic liquid 7 in the storage tank 3.
In the vicinity of the condensing and mixing unit 13 in the cryogenic liquid introduction pipe 15, there are a pressure gauge 43 for detecting the pressure of the mixed cryogenic liquid flowing through the inside, and a thermometer for detecting the temperature of the mixed cryogenic liquid flowing through the inside. 45 is provided.
The low temperature liquid introduction pipe 15 is provided with a second on-off valve 47. Further, a bypass pipe 49 that short-circuits the upstream side of the condensing and mixing unit 13 and the downstream side of the second on-off valve 47 is installed, and the bypass pipe 49 is provided with a third on-off valve 51.

<Gas-liquid two-phase flow ejection nozzle>
The gas-liquid two-phase flow jet nozzle 17 is provided in the low-temperature liquid introduction pipe 15 and jets the mixed low-temperature liquid introduced by the low-temperature liquid introduction pipe 15 so as to boil under reduced pressure to be jetted as a gas-liquid two-phase flow. It is.
The gas-liquid two-phase flow ejection nozzle 17 has a reduced diameter of the discharge port 17a in order to eject the mixed low-temperature liquid supplied from the low-temperature liquid introduction pipe 15 at high speed.

<Control unit>
The control part 22 inputs the detection information of the pressure gauge 43 and the thermometer 45, and controls the flow volume adjusting valve 20 based on this, and adjusts the evaporative gas flow volume supplied to the condensation mixing part 13. FIG.
The greater the amount of gas phase entrained in the condensing and mixing unit 13, the greater the amount of gas phase discharged from the gas-liquid two-phase flow ejection nozzle 17, and the mixing and stirring power in the storage tank 3 is improved. Therefore, it is preferable to adjust the entrainment amount of the gas phase while monitoring the mixing state of the storage tank 3. As a method of monitoring the mixing state of the storage tank 3, the temperature distribution in the height direction in the storage tank 3 by a plurality of thermometers or density meters (not shown) installed in the height direction in the storage tank 3. One example is measuring the density distribution.

However, in the present invention, the gas-liquid two-phase flow ejection nozzle 17 is compact, the fluid that has exited the condensing and mixing unit 13 is stably supplied to the gas-liquid two-phase flow ejection nozzle 17, and the liquid pump power is reduced. After the evaporating gas is entrained in the mixing section 13, the liquid phase is set. The low-temperature liquid introduction pipe 15 heading from the condensing and mixing unit 13 to the gas-liquid two-phase flow ejection nozzle 17 is often a downward flow, and the downward flow in the gas-liquid two-phase flow state is unstable in flow, This is because the pressure loss increases. Therefore, the upper limit of the entrainment amount of the evaporating gas is until the saturated mixing state is obtained in the condensing and mixing unit 13.
The flow rate of such evaporative gas is detected by the pressure gauge 43 provided on the outlet side of the condensing and mixing unit 13 to detect the pressure of the mixed cryogenic liquid, and the saturation temperature is obtained based on the detected pressure. Check whether the temperature of the low-temperature fluid on the outlet side is equal to or lower than the saturation temperature. If the temperature is higher than the saturation temperature, the flow rate adjusting valve 20 is adjusted so that the flow rate of the evaporating gas is reduced so You can do it.

  In addition, the control unit 22 determines whether to mix the cryogenic liquid 7 in the storage tank 3 or to perform normal delivery of the cryogenic liquid 7, the flow rate adjusting valve 20, the first on-off valve 29, the second on-off valve 47, and Switching is performed by opening / closing control of the third opening / closing valve 51.

The mixing method of the cryogenic liquid in the storage tank using the cryogenic liquid mixing apparatus 1 in the storage tank configured as described above will be described.
When mixing of the cryogenic liquid in the storage tank is not performed, the flow rate adjustment valve 20 is closed, the first on-off valve 29 is opened, and the second on-off valve 47 and the third on-off valve 51 are closed. As a result, the required amount of the cryogenic liquid 7 in the storage tank 3 is supplied to the use side by the liquid pump 11 via the cryogenic liquid delivery pipe 27, and the evaporative gas is compressed by the gas compressor 19 to be sent to the evaporative gas delivery pipe 21. Is supplied to the use side.

When mixing in the storage tank 3, the 2nd on-off valve 47 is opened, the 3rd on-off valve 51 is closed, and the flow regulating valve 20 is made into a predetermined opening degree. The first opening / closing valve 29 appropriately adjusts the opening according to the demand on the use side.
As a result, the cryogenic liquid 7 in the storage tank 3 is supplied to the condensing and mixing unit 13 via the cryogenic liquid extraction pipe 9 by the liquid pump 11. On the other hand, the evaporative gas is compressed by the gas compressor 19 and supplied to the condensing and mixing unit 13 through the evaporative gas extraction pipe 5.
In the condensing and mixing unit 13, when the high-temperature evaporative gas comes into contact with the low-temperature low-temperature liquid 7, the evaporative gas condenses into a liquid and is mixed with the low-temperature liquid 7. The low-temperature liquid) becomes a temperature higher than the temperature in the storage tank 3 (evaporative gas condensation and mixing step).
The mixed cryogenic liquid is supplied to the gas-liquid two-phase ejection nozzle via the cryogenic liquid introduction pipe 15 in a liquid phase state.
The mixed low-temperature liquid supplied to the gas-liquid two-phase jet nozzle is boiled under reduced pressure by being jetted at a high speed from the gas-liquid two-phase jet nozzle, and jetted into the low-temperature liquid 7 as a gas-liquid two-phase flow (gas-liquid two Phase flow ejection process).

As shown in FIG. 1, the gas-liquid two-phase flow discharged into the storage tank 3 has a higher arrival height than the liquid-phase single-phase jet due to the rising effect of bubbles contained in the jet, and the stirring and mixing effect Will improve.
Further, even after the jet is diffused, a liquid-phase upflow accompanying the upflow of bubbles is formed, and the stirring and mixing effect is increased.
On the condition that the stirring / mixing capacity is not so required, the storage tank 3 is formed by a liquid single-phase jet by closing the second on-off valve 47, opening the third on-off valve 51, and closing the flow rate adjusting valve 20. It is also possible to stir and mix the inside.

As described above, according to the present embodiment, the gas-liquid two-phase flow is discharged from the gas-liquid two-phase ejection nozzle into the liquid in the storage tank 3 as a jet, so that the low-temperature liquid 7 in the storage tank 3 High stirring effect.
In the present embodiment, the evaporative gas extraction pipe 5 and the low-temperature liquid extraction pipe 9 of the present embodiment are provided by branching from the existing evaporative gas delivery pipe 21 and the low-temperature liquid delivery pipe 27. It can be easily installed, and modification costs can be reduced.
In the present embodiment, the vaporized gas that has come into contact with the low temperature liquid 7 in the condensing and mixing unit 13 is in the liquid phase, so that the supply from the condensing and mixing unit 13 to the gas-liquid two-phase flow ejection nozzle 17 is stable. The power of the liquid pump 11 for supplying to the gas-liquid two-phase flow ejection nozzle 17 can be reduced.
Furthermore, since a part of the evaporated gas is condensed and returned to the storage tank 3, the effect of reducing the amount of evaporated gas to be processed by another process sent from the evaporated gas delivery pipe 21 is also obtained.

  In the above description, the first on-off valve 29, the second on-off valve 47, the third on-off valve 51, and the flow rate adjusting valve 20 are automatically opened and closed using the control unit 22, but in the present invention, the control unit This includes a case where these valve relationships are individually opened and closed manually or the like without having 22.

DESCRIPTION OF SYMBOLS 1 Low temperature liquid mixing apparatus in storage tank 3 Storage tank 5 Evaporative gas extraction pipe 7 Low temperature liquid 9 Low temperature liquid extraction pipe 11 Liquid pump 13 Condensing mixing part 15 Low temperature liquid introduction pipe 17 Gas-liquid two-phase flow ejection nozzle 17a Discharge port 19 Gas compression Machine 20 Flow rate adjusting valve 21 Evaporative gas delivery pipe 22 Control part 27 Cryogenic liquid delivery pipe 29 First on-off valve 31 Header 33 Venturi type mixing nozzle 35 Cryogenic liquid inflow path 37 Reduced diameter part 39 Evaporative gas suction part 41 Ejection port 43 Pressure gauge 45 Thermometer 47 Second on-off valve 49 Bypass pipe 51 Third on-off valve

Claims (8)

A method for mixing cryogenic liquid in a storage tank that mixes cryogenic liquid stored in a storage tank,
An evaporative gas condensing and mixing step of condensing the evaporative gas by mixing the evaporative gas generated in the reserving tank with the low-temperature liquid extracted from the storage tank; and pumping the cryogenic liquid in the liquid pump have a gas-liquid two-phase flow ejection step for ejecting a gas-liquid two phase flow by flash boiling by ejection into a cryogenic liquid in the reservoir,
The evaporative gas condensing and mixing step detects the pressure and temperature of the mixed cryogenic liquid, and adjusts the flow rate of the evaporating gas to be mixed so as to boil under reduced pressure in the gas-liquid two-phase flow ejection step based on the detected pressure and temperature. Mixing method of cryogenic liquid in storage tank. The evaporative gas condensing and mixing step detects the pressure and temperature of the mixed cryogenic liquid, and adjusts the flow rate of the evaporative gas so that the mixed cryogenic liquid becomes a saturation temperature or less based on the detected pressure and temperature. The method for mixing the cryogenic liquid in the storage tank according to claim 1. The method for mixing a cryogenic liquid in a storage tank according to claim 1 or 2, wherein the evaporative gas condensation and mixing step is performed using a venturi-type mixing nozzle. Vapor condensing mixing step, the mixing method of storage tank cryogenic liquid according to any one of claims 1 to 3 characterized by mixing the evaporated gas in the cryogenic liquid to increase the pressure by a gas compressor. An evaporative gas extraction pipe for extracting all or part of the evaporative gas generated in the storage tank, a low-temperature liquid extraction pipe for extracting the low-temperature liquid from the storage tank, and a low-temperature liquid in the storage tank provided in the low-temperature liquid extraction pipe A liquid pump that pumps liquid, and the evaporative gas extracted from the evaporative gas extraction pipe is brought into contact with the low-temperature liquid extracted from the low-temperature liquid extraction pipe to condense the evaporative gas and mix it with the low-temperature liquid. A condensing and mixing unit, a flow rate adjusting valve that adjusts the flow rate of the evaporative gas supplied to the condensing and mixing unit, and a cryogenic liquid whose temperature has risen more than that in the storage tank by the condensing and mixing unit into the cryogenic liquid in the storage tank A cryogenic liquid introduction pipe to be introduced, and a gas-liquid two which is provided in the cryogenic liquid introduction pipe and is boiled under reduced pressure by ejecting the cryogenic liquid introduced by the cryogenic liquid introduction pipe and ejected as a gas-liquid two-phase flow A flow jet nozzle, and a thermometer for sensing the pressure gauge, the temperature of the mixture already cryogenic liquid provided in cryogenic fluid inlet tube for detecting the pressure of the blended cryogenic liquid provided in the cold liquid inlet pipe, the And a control unit for inputting the detection information of the thermometer and the pressure gauge and adjusting the flow rate adjusting valve so as to boil under reduced pressure when the gas-liquid two-phase flow ejection nozzle is ejected. Mixing device for cryogenic liquid in the tank. The said control part detects the pressure and temperature of the said mixed cryogenic liquid, and adjusts the said flow regulating valve so that the said mixed cryogenic liquid may become below saturation temperature based on this. The cryogenic liquid mixing device in the storage tank described. The said condensing mixing part is comprised by the venturi type mixing nozzle, The mixing apparatus of the cryogenic liquid in a storage tank of Claim 5 or 6 characterized by the above-mentioned. The mixing device for a cryogenic liquid in a storage tank according to any one of claims 5 to 7, wherein a gas compressor for increasing a pressure of the evaporation gas is provided in the evaporation gas extraction pipe.