JPH08291899A - Vaporizer for liquefied natural gas and cooling and stand-by holding method thereof - Google Patents

Abstract

PURPOSE: To prevent heat source fluid from freezing in a device by providing a cutoff valve in a heating medium liquid pipe out of a heating medium vapor pipe for guiding heating medium vapor from an evaporator to vaporizers, and the heating medium liquid pipe for refluxing heating medium liquid condensed-liquefied in the vaporizers to the evaporizer. CONSTITUTION: The inlet ports 2b to 4b of vaporizers 2 to 4 are connected to a heat medium vapor exhaust port 1a of an evaporator 1 through a cutoff valve S-1 by a heat medium vapor pipe 5, and the exhaust ports 2a to 4a of vaporizers 2 to 4 are connected to a heating medium liquid inlet port 1b of the evaporator 1 through a cutoff valve S-2 by a heating medium liquid pipe 6. When a failure occurs in a control system, a supply system of heat source fluid, or when there is a possibility of drop in the temperature of heating medium in the evaporator 1 below zero deg.C, the cutoff valve S-1 provided in the heat medium vapor pipe 5 and the cutoff valve S-2 provided in the heating medium liquid pipe 6, are shut off to stop the evaporation of heating medium in the evaporator 1. Further, when only the cutoff valve S-2 provided in the heating medium liquid pipe 6 is shut off to seal the heating medium liquid in the vaporizers 2 to 4, the heat exchange between the heating medium vapor and LPG is restricted to stop the evaporation in the evaporator 1.

Description

Detailed Description of the Invention

[0001]

The present invention relates to liquefied natural gas (hereinafter,
LNG) vaporizer and its cooling standby holding method, more specifically, a heat exchanger in which two fluids are brought into contact with each other with a metal wall interposed therebetween so that heat is transferred between the fluids, so-called indirect heat. It consists of a group of exchangers and uses L or L as a heat source, such as hot water or seawater (hereinafter referred to as heat source fluid).
The present invention relates to a device for vaporizing and heating NG and a method for holding and cooling it.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 61-24634 shown in FIG. 2 shows a conventional device which is composed of a multi-tube type indirect heat exchanger group and which vaporizes and heats LNG by using a heat source fluid as a heat source. The device shown has been proposed.

As shown in FIG. 2, the essence of this proposal is supplied from a conduit 4 to a group of tubes in the intermediate heat medium type indirect heat exchanger 1 containing the intermediate heat medium 1a. , The intermediate heat medium 1 by the heat source fluid flowing out from the conduit 5.
a is heated and evaporated, and the evaporated intermediate heat medium vapor
The LNG supplied from the conduit 6 is heated to the tube group 7 housed in the heat exchanger 1. The vapor of the intermediate heat medium is condensed and liquefied by heat exchange with LNG, drops to the lower liquid phase portion, and repeats evaporation again.

The LNG heated by the heat exchanger 1 is supplied to the conduit 8
To the shell-and-tube heat exchanger 2 and further heated in the heat exchanger 2 by the heat source fluid supplied from the conduit 3 and heated to a temperature suitable for use, and then the conduit as vaporized natural gas. It is a device of the type that is discharged from No. 9. The drawbacks of this conventional apparatus are the following three points.

(1) A method of directly exchanging heat between LNG and a heat source fluid in the multi-tube heat exchanger 2 without passing through an intermediate heat medium is adopted, and flammable LNG leaks to the heat source fluid line. There is a great risk.

The reason is that the operating pressure of LNG in this type of LNG vaporizer is usually 20 to 50 kg / cm ² G, whereas the operating pressure of the heat source fluid is as low as 10 kg / cm ² G or less,
Even if a small defect such as a pinhole occurs in the heat exchanger 2, a large amount of LNG leaks to the heat source fluid line. In particular, when hot water of a factory or power plant is used as the heat source fluid, if LNG leaks to this hot water line, flammable gas will be diffused in the factory or power plant, resulting in catastrophe.

(2) Direct heat exchange between the heat source fluid that freezes at a temperature near 0 ° C. and the LNG always causes a risk of freezing the heat source fluid in the heat exchanger 2.
When freezing occurs in the heat exchanger 2, it takes a long time to melt the ice and the LNG vaporization operation must be stopped during the ice melting operation. Further, if ice is generated even if it does not reach freezing, erosion occurs due to the detached ice pieces, the heat exchanger 2 is damaged, and the above (1)
Will increase the risk of.

In this conventional method, even if the heat exchanger 1 is designed so that the LNG is heated to a temperature at which the ice is not generated in the heat exchanger 2, the load of the LNG changes or the heat source fluid changes. If flow rate fluctuations occur, there is still a risk of freezing. In particular, in a multi-tube heat exchanger, uneven flow is likely to occur in the fluid flowing in the tube group, and ice is likely to be produced in the tube in which the flow velocity of the fluid is slow.

(3) Most of LNG is used for mass consumption such as fuel and city gas in power plants for business use, and the LNG vaporizer is also large in size and often used in plural series. In multiple series LNG vaporizers, etc., it is necessary to adjust the number of operating series of equipment according to the consumption state of vaporized natural gas, but adjust the number of operating series of equipment with the LNG load completely stopped. I can't.

The reason for this is that when cryogenic LNG flows into the vaporizer at room temperature at the start of vaporization operation, a large thermal stress is generated in the components of the apparatus due to a rapid temperature change, and thermal fatigue is caused by the repeated thermal stress. Is progressed and the mechanical life is shortened.

In order to suppress the thermal stress at the start of the vaporizing operation to a low level, it is necessary to keep the vaporizing apparatus at rest at a predetermined low temperature with LNG flowing to some extent, that is, to perform a cooling standby holding operation. . If the flow rate of LNG required for this cooling standby holding operation is large, unnecessary vaporized natural gas will be generated, leading to a waste of energy.

As a conventional cooling standby holding method for an LNG vaporizer, Japanese Patent Laid-Open No. 4-1811 shown in FIG. 3, FIG. 4 and FIG.
The method described in Japanese Patent Publication No. 00 has been proposed. The essence of this proposal is, as shown in FIG. 3, FIG. 4 and FIG. 5, that the intermediate heat medium in the intermediate heat medium type indirect heat exchanger 1 is controlled by a command from the pressure detection unit 12 that detects the pressure of the intermediate heat medium. A method of adjusting the LNG supply amount as shown in FIG. 3 (adjusting with the flow rate adjusting valve 8a) so that the temperature or pressure (detected by the pressure detector of (12)) becomes a predetermined value, or shown in FIG. Such a method for adjusting the flow rate of the heat source fluid (adjusting with the flow rate adjusting valve 6a) and a method for adjusting both the supply amount of LNG and the flow rate of the heat source fluid (adjusting with the flow rate adjusting valves 6a, 8a) as shown in FIG. Is.

In this conventional method, there is a structural problem of the intermediate heat medium type indirect heat exchanger 1, and it is possible to reduce the flow rate of LNG required for waiting for cooling of the LNG vaporizer. The reason is that the intermediate heat medium type indirect heat exchanger 1 has the liquid of the intermediate heat medium in the lower part and the saturated vapor of the intermediate heat medium in the upper part, and the heat transfer pipe 10 of the LNG vaporizer always keeps the saturated vapor. Therefore, the flow rate of LNG required for cooling standby is determined by the amount of heat transfer between the LNG in the heat transfer tube 10 and the saturated steam of the intermediate heat medium, and the amount is approximately as follows (1 ) Expression can be displayed.

L = UA (T _S −T _L ) _LM / (H _LO −H _LI ) ………………………… (1) where L: LNG LNG required for cooling standby of the vaporizer.
Flow rate U: Overall heat transfer coefficient between LNG and intermediate heat medium vapor A: Surface area of LNG vaporizer heat transfer tube T _S : Temperature of intermediate heat medium vapor in LNG vaporizer _TL : Temperature of LNG in LNG vaporizer (T _S −T _L ) _LM : Logarithmic mean temperature difference between the intermediate heat carrier vapor and LNG in the LNG vaporizer H _LI , H _LO : LNG enthalpy at the inlet and outlet of the LNG vaporizer

In equation (1), the overall heat transfer coefficient U, the surface area A of the heat transfer tube, and the enthalpies H _LI and H _LO of LNG are substantially constant, and the flow rate of LNG required to wait for cooling of the LNG carburetor is within the carburetor. The temperature T _S of the intermediate heat medium vapor and the temperature T _L of the LNG are determined, but the temperature T _{L of} the LNG is also determined by the cooling standby temperature of the carburetor. After all, in order to reduce the flow rate of LNG required for cooling standby, it depends on how low the intermediate heat medium vapor temperature T _S in the carburetor can be suppressed, but the heat source fluid is 0 ° C. like hot water or seawater. In the case of a fluid that freezes in the vicinity, the temperature T _S of the intermediate heat medium vapor can be set only near 0 ° C., and as a result, the flow rate of LNG required for cooling standby cannot be reduced.

[0016]

DISCLOSURE OF THE INVENTION The present invention eliminates the drawbacks found in the conventional apparatus as described above, and prevents flammable gas such as LNG from leaking to the heat source fluid (hot water or seawater). It is an object of the present invention to provide a vaporization apparatus for LNG and a cooling standby holding method thereof, which does not freeze the heat source fluid therein, hardly uses LNG, and can hold the cooling standby of the apparatus.

[0017]

Means and Actions for Solving the Problems Means adopted by the present invention for solving the above problems are as follows.

1. A plurality of indirect heat exchangers are provided, and at least one of the indirect heat exchangers is used as a heat medium evaporator (hereinafter referred to as “evaporator”) that transfers heat with a phase change, and also as another heat exchanger. The vaporizer is used as a vaporizer of LNG (hereinafter referred to as vaporizer), and a heat source fluid such as hot water or seawater is caused to flow through the vaporizer to generate heat medium vapor from a heat medium and the heat medium vapor is vaporized. A method in which LNG is converted into vaporized natural gas by conducting heat exchange with LNG to a vaporizer, and the heat medium liquid condensed and liquefied by heat exchange with LNG is returned to the evaporator to circulate and use the heat medium. Of the heat medium vapor from the evaporator to the vaporizer (hereinafter referred to as heat medium vapor pipe), and the liquid of the heat medium condensed and liquefied by the vaporizer is returned from the vaporizer to the evaporator. A conduit (hereinafter referred to as a heat transfer liquid pipe) To both of you),
Alternatively, an LNG vaporizer having a shutoff valve only on the heat transfer medium pipe.

2. A state in which the cutoff valves provided in the heat medium vapor pipe and the heat medium liquid pipe are shut off to completely stop the flow of the heat medium between the evaporator and the vaporizer, or only the shutoff valve provided in the heat medium liquid pipe And controlling the flow rate of LNG to the vaporizer so that the temperature of the LNG introduction part of the vaporizer reaches a predetermined temperature in a state where the liquid of the heat medium is enclosed in the vaporizer. 2. The cooling standby holding method for the LNG vaporizer according to 1 above.

Next, the structure and operation of the LNG vaporizer according to the present invention, and the method and operation of the cooling standby holding method according to the present invention will be specifically described in detail with reference to FIG. 1 is a system diagram according to an embodiment of the present invention.
Inside, 1 shows an evaporator and 1A shows a tube group of an evaporator for flowing a heat source fluid. The vapor V of the heat medium is accommodated in the upper portion of the evaporator 1 on the cylinder side, and the heat medium vapor outlet 1a is provided in communication with the vapor phase.

At the lower part of the evaporator 1 on the barrel side, the liquid L of the heat medium is contained to the extent that the tube group 1A is immersed, and an inflow port 1b of the heat medium liquid L is provided in communication with the liquid phase. ing. Further, at the end of the evaporator 1, an inlet 1c and an outlet 1d for the heat source fluid, which are communicated with the tube group 1A of the evaporator 1, are provided.

In FIG. 1, reference numerals 2, 3 and 4 denote vaporizers, and each vaporizer has a U-shaped tube group 2 for flowing LNG.
Equipped with A, 3A and 4A. Heater vapor inlets 2b, 3b and 4b are provided on the upper side of the vaporizers 2 to 4 on the body side, and discharge ports 2a, 3a and 4a of the heat medium liquid are provided on the lower side of the body. . Moreover, the U-shaped tube groups 2A to 4 of the respective carburetors 2 to 4 are provided at the ends of the respective carburetors 2 to 4.
LNG inflow ports 2c, 3c, 4c communicating with A and LNG discharge ports 2d, 3d, 4d after being heated by the heat medium vapor in each of the vaporizers 2 to 4 are provided.

Inlet 2b for heat medium vapor of each vaporizer 2-4,
3b and 4b are connected to a heat medium vapor discharge port 1a of the evaporator 1 via a shutoff valve (S-1) by a heat medium vapor conduit 5,
The heat medium liquid outlets 2a, 3a, 4a of the vaporizers 2 to 4 are also provided.
Is connected to the heat transfer medium inlet 1b of the evaporator 1 via the cutoff valve (S-2) by the heat transfer medium conduit 6.

The LNG inflow port 2c of the vaporizer 2 is provided with LNG.
LNG of the vaporizer 2 is connected to the supply conduit 7 of
2d is connected to the LNG inlet 3c of the carburetor 3 by the conduit 8, and the LNG outlet 3d of the carburetor 3 is connected to the LNG inlet 4c of the carburetor 4 by the conduit 9 and the LN of the carburetor 4 is connected.
The G outlet 4d is connected to a vaporized natural gas conduit 10.

The heat source fluid supplied from the heat source fluid inlet port 1c to the evaporator 1 via the heat source fluid supply conduit 11 flows in the tube group 1A of the evaporator 1 and the heat source fluid outlet port 1d to the conduit 12. While being discharged, the heat medium liquid L in the evaporator 1 is heat-exchanged and cooled. On the other hand, the heat medium in the evaporator 1 heated by the heat source fluid boils to generate heat medium vapor.

The heat medium vapor generated in the evaporator 1 is
The U-shaped tube group 2A of each carburetor 2-4 is blown into the barrel side of each carburetor 2-4 installed at a higher position through the conduit 5.
After heat exchange with LNG flowing through 4A to condense and liquefy, it is refluxed into the heat medium liquid phase of the evaporator 1 through the conduit 6 due to the head difference. That is, a self-circulating flow of the heat medium is formed between the evaporator 1 and the vaporizers 2 to 4.

L supplied from the LNG supply conduit 7
The NG is sequentially heated by the heat medium vapor in the vaporizer 2, the vaporizer 3, and the vaporizer 4, and the LNG discharge port 4d of the vaporizer 4 becomes vaporized natural gas heated to a temperature suitable for use, It is supplied to the place of use from the conduit 10.

The purpose of the vaporizers 2 to 4 is to heat cryogenic LNG with a heating medium vapor to obtain vaporized natural gas at a temperature suitable for use. The number of constituent bases can be arbitrarily selected. However, it is suitable to use two or more units.
The reason is that when the number of constituent units is reduced, the heat transfer area per carburetor must be increased, and the tube plate of the carburetor becomes larger accordingly, which causes a problem in measures against thermal stress. Is. It is also possible to reduce the number of carburetors by making the structure of the vaporizer in which a plurality of tube groups (bundles) are mounted in the same body.

The tube group in the vaporizer is U shown in the embodiment of FIG.
It is a good idea to make the tube shaped like a tube to prevent deformation of the tube due to heat shrinkage, but the vaporizer after the LNG has been heated to some extent,
For example, in the vaporizer 4 in FIG. 1, a plate type indirect heat exchanger can be used. The method of introducing the heat medium vapor into the vaporizers 2 to 4 is not limited to the parallel introduction method shown in FIG. 1, but is also a series introduction method, that is, the heat medium liquid discharge port 4a of the vaporizer 4 and the heat medium vapor of the vaporizer 3. A method of connecting the heat medium liquid discharge port 3a of the vaporizer 3 and the heat medium vapor flow inlet 2b of the vaporizer 2 to the inflow port 3b can also be adopted.

The heat medium usable in the present invention is a substance which is vaporized in the evaporator and liquefied in the vaporizer, that is, a substance which causes heat transfer with a phase change of the gas-liquid under the operating conditions of the LNG vaporizer. Non-flammable, low freezing point, non-toxic,
In addition, any substance that does not pose a problem in terms of global environmental protection,
2,2,2-Tetrafluoroethane (abbreviated name HFC-13
4a) and the like are suitable.

For example, if HFC-134a is used as the heat medium, the heat source fluid is nonflammable HFC-134a.
The vapor of a exchanges heat with LNG. That is,
Like the conventional LNG vaporizer, all the places where the heat source fluid and the LNG directly exchange heat are excluded, and there is no possibility that the LNG leaks into the heat source fluid. For example, even if LNG leaks into the heat medium due to a defect in the vaporizer,
Does not exist in the liquid state under the operating conditions of the vaporizer barrel, that is, the heat medium, and no natural gas is mixed into the heat medium liquid of the evaporator.

Further, the natural gas leaking into the heat medium, as a non-condensable gas, may hinder the heat exchange between the heat medium and the LNG in the vaporizer. The pressure rises above the saturated vapor pressure of the heat carrier. Therefore, by monitoring the pressure and temperature of the heat medium in the evaporator using an appropriate process instrument (not shown), the minute leakage of LNG can be easily detected, and the supply of LNG is shut off based on this detection. It is possible to completely prevent LNG from leaking to the heat source fluid. As described above, according to the present invention, the above problems can be solved and hot water in a factory or a power plant can be used as a heat source fluid.

Next, it will be explained how the above-mentioned problem of not freezing the heat source fluid in the apparatus is achieved. As described above, according to the present invention, it is the heat medium that directly exchanges heat with the cryogenic LNG.
If a substance with a low freezing point such as C-134a is used, LN
The heat medium does not solidify to prevent normal operation of the G vaporizer, and the temperature of the heat medium in the evaporator is set to 0.
By keeping the temperature above ℃, it becomes impossible for the heat source fluid cooled by this heat medium to freeze.

As a means for keeping the temperature of the heat medium in the evaporator 1 at 0 ° C. or higher, in normal operation, the temperature of the heat medium is made 0 ° C. or higher, or the pressure of the heat medium circulation system is 0 ° C. Evaporator 1 so that the saturated vapor pressure of the heat medium at ℃ becomes higher than
It can be easily achieved by adjusting the flow rate of the heat source fluid supplied to the above and / or the flow rate of LNG supplied to the vaporizers 2 to 4.

The problem is whether or not the freezing of the heat source fluid can be prevented even in the event of an abnormality such as a failure of the control system or a failure of the supply system of the heat source fluid. This can be easily solved by the device of the present invention. When it is feared that the temperature of the heat medium in the evaporator 1 will be 0 ° C. or less, the means is a shutoff valve (S-1) provided in the heat medium vapor conduit 5 and a shutoff provided in the heat medium liquid conduit 6. In the vaporizer, the valve (S-2) is shut off to stop the evaporation of the heat medium in the evaporator 1, or only the shutoff valve (S-2) provided in the heat medium liquid conduit 6 is shut off. It is a means for stopping the evaporation of the heat medium in the evaporator 1 by enclosing the liquid of the heat medium in 2 to 4 and suppressing the heat exchange between the heat medium vapor and LNG.

Stopping the evaporation of the heat medium when the temperature of the heat medium reaches 0 ° C. means that the temperature of the heat medium is not lowered any more, and the freezing of the heat source fluid in the evaporator 1 is prevented. Will be done. Thus, according to the present invention, the LN
The heat source fluid does not freeze under any operating condition of the G vaporizer, and the above-mentioned object can be achieved.

Next, a method of holding the vaporizers 2 to 4 in the cooling standby state will be described. As described above, it is necessary to keep the vaporizers 2 to 4 that are temporarily stopped at a low temperature in preparation for the next operation start. In particular, with regard to the vaporizer 2 into which the coldest LNG is introduced at the start of operation, even if the LNG is supplied at a predetermined speed, the temperature is kept such that thermal stress does not reduce the mechanical life of the vaporizer 2. Although it must be kept, the above-mentioned problem is how to reduce the supply amount of LNG required for keeping the vaporizers 2 to 4 in the cooling standby state.

The cooling standby holding method for the vaporizers 2 to 4 according to the present invention includes a shutoff valve (S-1) provided in the heat medium vapor conduit 5 and a shutoff valve (S-2) provided in the heat medium liquid conduit 6. ) Is shut off or only the shut-off valve (S-2) is shut off, a temperature controller 13 provided with a temperature detection end 13a in the LNG introduction part 2e of the carburetor 2 detects a value detected by the controller. LNG for standby operation of the carburetor 2 so that the control target set temperatures become equal
By directly adjusting the LNG flow control valve 15a provided in the conduit 7a, or by using the LNG flow controller 14
It is a so-called cascade control method in which the flow control valve 15a of the LNG is adjusted so that the detection signal of the flow rate detector 14a and the output signal of the temperature controller 13 coincide with each other. .

In the above embodiment, the method of waiting for cooling so that the temperature of the LNG introducing section 2e into which the coldest LNG is introduced at the start of operation is set to a predetermined value has been shown. The purpose is to use the LNG vaporizer. It means that the mechanical life of the carburetor is not reduced by the stoppage of the carburetor, and if the carburetor can be cooled and maintained at a predetermined temperature, the temperature of any position of the carburetor is detected and the temperature becomes a predetermined value. It is also possible to adjust the flow rate of LNG.

Further, during normal operation, the LNG flow rate is adjusted by using the LNG flow rate control valve 15 provided in the LNG supply conduit 7. However, the LNG flow rate required for holding the carburetor in the cooling standby state is very small. Therefore, the control valve 15a for small flow rate is used for the purpose of improving the control accuracy.

By shutting off the shutoff valves (S-1) and (S-2) provided in the heat medium vapor conduit 5 and the heat medium liquid conduit 6, the flow of the heat medium between the evaporator 1 and the vaporizers 2 to 4 can be prevented. Stop it completely,
Alternatively, it is possible to prevent the inflow of the heat medium vapor into the vaporizer by shutting off only the shutoff valve (S-2) provided in the heat medium liquid conduit 6 to confine the liquid of the heat medium in the vaporizer. The heat flow from the evaporator to the vaporizer is prevented regardless of the heat medium temperature in the evaporator, and the heat medium temperature in the vaporizer and the LNG temperature are in equilibrium. That is, in the formula (1), the heat medium temperature T _S in the vaporizer and the LNG temperature T _L become equal, and the LNG flow rate L required for cooling standby of the vaporizer becomes zero.

When the carburetor is held in the cooling standby state in such a state, the heat input to the carburetor is only the heat input from the atmosphere, but normally the carburetor is kept cold by a heat insulating material such as rigid polyurethane foam. And the heat input from the atmosphere is extremely small. That is, according to the present invention, the flow rate of LNG required for holding the carburetor in the cooling standby state can be extremely small, and the above problems can be easily solved.

[0043]

EXAMPLES Table 1 shows the specifications of each device in the equipment configuration shown in FIG.
In the LNG vaporizer having the value of, the LNG flow rate required to hold the vaporizer in the cooling standby state under the operating conditions shown in Table 2 is as follows.

[0044]

[Table 1]

[0045]

[Table 2]

(Example 1) A shutoff valve (S-1) provided in the heat medium vapor conduit 5 and a shutoff valve (S-) provided in the heat medium liquid conduit 6
In the state where 2) is shut off, the flow rate of LNG for maintaining the temperature of the LNG introduction part 2e of the vaporizer 2 at around -85 ° C is:
The average for 12 hours after reaching the steady state was 8 kg / hr.

(Embodiment 2) In order to keep the temperature of the LNG introduction part 2e of the vaporizer 2 at around -85 ° C with only the shutoff valve (S-2) provided in the heat transfer medium conduit 6 being shut off. LNG
The average flow rate was 6 kg / hr for 12 hours after the steady state was reached.

(Comparative Example 3) Similar to the conventional cooling standby holding method of the vaporizer, the shutoff valve (S-1) and the shutoff valve (S) are used.
-2) is opened, the flow rate of the heat source fluid supplied to the evaporator 1 is set to a predetermined value, and the pressure of the heat medium in the evaporator 1 is 2 kg / cm ² G (about 0 of HFC-134a). C. (saturated vapor pressure of C) is adjusted so that the LNG supply amount to the vaporizers 2 to 4 is adjusted so that the temperature of the LNG introduction part 2e of the vaporizer 2 can be maintained near -85 ° C. Minimum flow rate is 75
It was 0 kg / hr. That is, according to the present invention, the flow rate of LNG required to hold the vaporizer in the cooling standby state is about 1/1 of the conventional flow rate.
It will be 00.

[0049]

As described in detail above, according to the present invention, there is a risk that the flammable gas may leak into the heat source fluid and the LN.
There is no risk of the heat source fluid being frozen in the G vaporizer,
Hot water from factories or power plants can be used as the heat source fluid. In addition, the flow rate of LNG required for maintaining the cooling standby of the LNG vaporization device is extremely small, and the energy saving effect is obtained when the present invention is applied to the facility for city gas generation or the fuel facility for power generation, which has a particularly large load fluctuation. Is greatly improved.

[Brief description of drawings]

FIG. 1 is a system diagram of an LNG vaporizer according to an embodiment of the present invention.

FIG. 2 is a system diagram showing a conventional LNG vaporizer.

FIG. 3 is a system diagram showing a cooling standby holding method of a conventional LNG vaporizer.

FIG. 4 is a system diagram showing another cooling standby holding method of another conventional LNG vaporizer.

FIG. 5 is a system diagram showing another cooling standby holding method for a conventional LNG vaporizer.

[Explanation of symbols]

 1 Heat Medium Evaporator 1A Evaporator Tube Group 1a Heat Medium Vapor Discharge Port 1b Heat Medium Liquid Inlet 1c Heat Source Fluid Inlet 1d Heat Source Fluid Discharge Port V Heat Medium Vapor Phase in Evaporator L Evaporator Heat medium liquid phase 2,3,4 LNG vaporizer 2A, 3A, 4A Vaporizer tube group 2a, 3a, 4a Heat medium liquid discharge port 2b, 3b, 4b Heat medium vapor inlet 2c, 3c , 4c LNG inlet 2d, 3d, 4d LNG outlet 2e LNG inlet 5 Heat medium vapor conduit 6 Heat medium liquid conduit S-1, S-2 Shut-off valve 7, 7a LNG supply conduit 8, 9 LNG Conduit 10 for vaporized natural gas 11 supply conduit for heat source fluid 12 discharge conduit for heat source fluid 13 temperature controller 13a temperature detection end 14 flow controller 14a flow detection end 15, 15a LNG flow control valve

Front page continuation (72) Inventor Shunichi Yasui 1 Higashishinmachi, Higashi-ku, Nagoya, Chubu Electric Power Co., Inc. (72) Inventor Masahiro Tokuda 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute ( 72) Inventor Masato Kaneko 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute (72) Inventor Keijiro Yoshida 2-5-1, Marunouchi Chiyoda-ku, Tokyo Sanryo Heavy Industries Co., Ltd.

Claims (2)

[Claims] 1. A plurality of indirect heat exchangers are provided in which two fluids are brought into contact with each other across a metal wall so that heat is transferred between the fluids, and at least one of the indirect heat exchangers is provided. Other indirect heat exchangers are used as vaporizers for liquefied natural gas, as heat medium evaporators that transfer heat with phase change,
A heat source fluid is passed through the evaporator to exchange heat with a heat medium in the evaporator to generate heat medium vapor, and the heat medium vapor is guided to the vaporizer to be heat-exchanged with liquefied natural gas to liquefy natural gas. A device of a system in which a gas is vaporized natural gas, and a heat medium liquid condensed and liquefied by exchanging heat with the liquefied natural gas is returned from the vaporizer to the evaporator to circulate the heat medium. At least one of a heat medium vapor conduit for guiding a heat medium vapor from the evaporator to the vaporizer and a heat medium liquid conduit for returning the heat medium liquid condensed and liquefied in the vaporizer to the evaporator, A vaporizer for liquefied natural gas, characterized in that a shutoff valve is provided in the heat transfer medium conduit. 2. The vaporizer of the carburetor is provided with a shutoff valve provided on the heat medium vapor conduit and the heat medium liquid conduit, and at least one of the shutoff valves provided on the heat medium liquid conduit is shut off. LN
2. A cooling standby holding of the liquefied natural gas vaporizer according to claim 1, wherein the amount of liquefied natural gas supplied to the vaporizer is adjusted so that the temperature of the G introduction part becomes a predetermined temperature. Method.