JPH0755370A - Evaporating device for low-temperature liquefied gas - Google Patents

Abstract

PURPOSE:To provide the evaporating device, in which an ice layer is not formed around the outer periphery of a heat transfer tube, the structure of which is strong, and in which vibration related to fluid is not caused and LNG is distributed uniformly to respective heat transfer tubes. CONSTITUTION:The evaporating device for low-temperature liquefied gas is constituted of a heat transfer tube 30, arranged vertically and liquefied gas is conducted to flow therethrough, while heating fluid is supplied to flow down along the outer peripheral surface of the same tube 30 to evaporate the liquefied gas through heat exchange between the heating fluid and the liquefied gas. The heat transfer tube 30 is constituted of a triple structure made by an inner tube 31, an intermediate tube 32 and an outer tube 33. The inflow port 31a of the liquefied gas is provided at the top of the inner tube 31 and an outflow port 33c, opened toward the inside of the intermediate tube, is provided at the lower end of the same. The lower end of the intermediate tube 32 is formed so as to be a closed structure having a bottom and an outflow port 32a, opened toward the inside of the outer tube 33, is provided at the top of the same tube 32. The top of the outer tube 33 is formed so as to be a closed structure equipped with a ceiling and the send-out port 33c of evaporated gas is provided at the lower end of the outer tube 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low temperature liquefied gas vaporizer represented by liquefied natural gas.

[0002]

There are many types of low-temperature liquefied gas, such as chlorine, ammonia, sulfur dioxide, alkanes such as methane, ethane and propane, alkenes such as ethylene, propylene and butylene, and oxygen and nitrogen. Used as a gas for a predetermined purpose. Of these, liquefied natural gas, which is a mixture of the alkanes and alkenes, is currently mainly used as a fuel for thermal power generation and a raw material for city gas,
Considering that the handling amount is enormous as compared with other low-temperature liquefied gas, and the low-temperature liquefied gas often refers to liquefied natural gas, the low-temperature liquefied gas will be described below by taking the liquefied natural gas as a representative.

Liquefied natural gas (hereinafter referred to as LNG) is usually transferred or stored as a liquid at low temperature and high pressure, but is vaporized in advance when it is actually used. An open rack vaporizer (hereinafter referred to as ORV) is often used to vaporize a large amount of LNG.

FIG. 7 is a schematic perspective view showing an example of the ORV. As shown in this figure, the ORV is a kind of heat exchanger, and heats and vaporizes LNG by heat exchange with seawater. That is, seawater is collected in the trough 8 from the seawater header 6 through the sprinkler nozzle 7, and drips from both side edge portions of the trough 8 while wetting the outer surface of the panel (heat transfer tube) 3. On the other hand, LNG is LNG manifold 1 to L
It is sent to the NG header 2, heated by heat exchange with the seawater, vaporized and raised in the panel 3, and led out from the NG header 4 to the NG manifold 5.

The panel 3 is an assembly in which a plurality of heat transfer tubes 3a made of metal pipes extending vertically as shown in FIG. 8 are arranged side by side in contact with each other in the lateral direction. While LNG rises inside 3a, heat is obtained from the seawater flowing down the outer peripheral surface of heat transfer tube 3a to be vaporized, and natural gas (hereinafter referred to as NG) can be obtained.

[0006]

By the way, since the conventional heat transfer tube 3a is a simple metal tube as shown in FIG. 8, the heat flow is very good and the outer peripheral surface of the heat transfer tube 3a is The heat retained by the flowing seawater can be easily transferred to L inside the heat transfer tube 3a.
Although it shifts to NG, conversely, the cold heat held by the LNG in the heat transfer tube 3a shifts to the seawater outside the tube, and the seawater flowing down while wetting the outer peripheral surface of the heat transfer tube 3a easily freezes. As a result, the icing layer 3b may be formed on the outer peripheral surface of the heat transfer tube 3a.

When such an ice accretion layer 3b is formed on the surface of the heat transfer tube 3a, heat transfer is hindered because ice does not have such a large thermal conductivity, and the heat conduction of the heat transfer tube 3a including the ice adhesion layer 3b occurs. Will be bad. Then, when icing that is larger than the design amount occurs, the cold heat of the LNG rising in the heat transfer tube 3a does not transfer favorably to seawater, so that the heat transfer tube 3a becomes lower than the design temperature and a large heat shrinkage occurs. It will be. When such heat shrinkage occurs, thermal stress is generated in the panel 3, and in an extreme case, the panel 3 is damaged, which is a disadvantage.

Therefore, in order to avoid such inconvenience, the panel 3 is prevented from being damaged by taking into consideration the temperature drop due to the formation of the icing layer 3b and the shrinkage amount obtained from the length of the heat transfer tube 3a. Equipment design is performed, but this is a major limitation in designing the structure of the panel 3.

Under these circumstances, in recent years, a double tube heat transfer tube has been proposed by Japanese Patent Laid-Open Nos. 3-286989 and 4-254,096.
In these publications, LNG is once supplied to the inner pipe of the double pipe from the upper part or the intermediate part and passes through an annular passage formed between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe. NG
Are configured to be derived.

With such a double-pipe structure, LNG is vaporized in the inner pipe to become NG, and this NG is heat-exchanged with seawater through the outer pipe through the outer pipe in the two-stage structure. Since it is performed, it is the NG that is not so cold that directly exchanges heat with the seawater through the outer pipe, and as a result, the freezing of the seawater is effectively suppressed.

Further, since the outer tube and the inner tube are provided independently of each other so that heat shrinkage does not interfere with each other,
The difference in heat shrinkage between them does not lead to panel damage.

Further, LNG is configured to be supplied into the inner tube from the upper or middle portion of the heat transfer tube, and seawater flowing down the outer peripheral surface of the heat transfer tube does not come into contact with the surface of the header section of the LNG. There is also an advantage that the inconvenience that the variation of the temperature distribution in the header portion becomes large is avoided, and the generation of thermal stress due to the large variation is suppressed.

However, the structure disclosed in Japanese Patent Laid-Open No. 386969/1990 has a structure in which the inner tube is completely accommodated with a predetermined gap formed inside the outer tube. Such a double structure is extremely difficult to fabricate, and the inner tube is in a state of floating in the air inside the outer tube, which is a structural weak point.

Further, in the one disclosed in the above-mentioned JP-A-4-254096, LNG is supplied in the heat transfer tube in a descending flow, and LNG is vaporized while descending. The vaporized NG upward flow interferes with each other to easily cause pressure pulsation in the heat transfer tube. If this pressure pulsation becomes large, it may develop into a so-called fluid-related vibration that shakes the entire apparatus, and the safety of the entire apparatus may be impaired.

Further, in the above-described downward flow in the LNG heat transfer tube, since the liquid head which is effective for uniform distribution of the upward flow cannot be used, the heat transfer tubes arranged in parallel as a panel are evenly distributed. Whether LNG is distributed or not is uncertain, and there is a problem that anxiety remains.

The present invention has been made in order to solve the above-mentioned problems, and an ice layer is not formed on the outer peripheral surface of the heat transfer tube, the structure is strong, and the fluid-related vibrations are high. It is an object of the present invention to provide a low-temperature liquefied gas vaporizer in which LNG is evenly distributed to each of a large number of heat transfer tubes arranged in parallel.

[0017]

In the vaporizer for low temperature liquefied gas according to claim 1 of the present invention, the liquefied gas is circulated inside the heat transfer tubes arranged in the vertical direction, and the outer periphery of the heat transfer tubes is also provided. A heating fluid is supplied so as to flow down to a surface, and in the vaporizer of a low temperature liquefied gas configured so that the liquefied gas is vaporized by heat exchange between the heating fluid and the liquefied gas, the heat transfer tube is It has a triple structure of a pipe, a middle pipe and an outer pipe, and a liquefied gas inflow hole is provided at the top of the inner pipe, and an outflow hole opened toward the inside of the middle pipe is provided at the lower end, The lower end of the outer tube has a closed structure with a bottom, and an outflow hole opening toward the inside of the outer tube is provided at the top, and the top of the outer tube has a closed structure with a ceiling and is vaporized at the lower end. Characterized by a gas delivery hole It is intended to.

In the vaporizer of low temperature liquefied gas according to a second aspect of the present invention, a heating greenhouse, which is a space in which the middle pipe and the inner pipe do not exist, is formed in the lower part of the outer pipe, and the lower end of the heating chamber is vaporized. A vaporizer for low-temperature liquefied gas according to claim 1, characterized in that a discharge hole for said gas is provided.

A vaporizer of low temperature liquefied gas according to a third aspect of the present invention is the vaporizer of low temperature liquefied gas according to the first or second aspect, wherein the outer peripheral surface of the inner pipe is heat-insulated. It is a feature.

A vaporizer for low temperature liquefied gas according to a fourth aspect of the present invention is the vaporizer for low temperature liquefied gas according to the first, second or third aspect, wherein the outer peripheral surface of the inner pipe and the inner peripheral surface of the middle pipe are One or both of an inner annular fluid passage formed between the inner tube and the outer annular fluid passage formed between the outer circumferential surface of the middle tube and the inner circumferential surface of the outer tube are formed in a spiral structure. It is characterized by that.

[0021]

According to the low-temperature liquefied gas vaporizer of the first aspect, the liquefied gas supplied from the top of the heat transfer tube consisting of the inner tube, the middle tube and the outer tube is first fed to the liquefied gas inflow hole of the inner tube. Is supplied to the inside pipe from the bottom, and moves from the outflow hole at the lower end into the inside pipe. The liquefied gas that has moved into the middle pipe rises in the middle pipe and moves into the outer pipe from the outflow hole in the upper part.

On the other hand, since the heating fluid flows down the outer peripheral surface of the heat transfer tube (outer tube), the heating fluid and the fluid in the outer tube (gas in which the liquefied gas is vaporized) are passed through the wall surface of the outer tube. The heat exchange is performed by the heat exchange, and the heat exchange is performed between the fluid in the outer pipe and the fluid in the middle pipe through the wall surface of the middle pipe. Further, heat exchange is performed between the fluid in the middle pipe and the fluid in the inner pipe via the wall surface of the inner pipe.

As described above, the liquefied gas supplied to the inner pipe receives heat from the heating fluid through the fluid existing between the three wall surfaces and the three wall surfaces, so that the amount of heat received is small, Although the temperature rises in the inner tube, it remains liquid. Then, the fluid whose temperature has risen rises in the middle pipe, and while receiving heat from the heating fluid from the intermediate wall surface through the wall surface of the outer tube and the fluid inside the outer tube, vaporization is started.

The fluid descending from the upper portion of the outer tube into the outer tube receives the heat of the heating fluid via the wall surface of the outer tube, is completely vaporized, and is led out of the system from the gas delivery hole at the bottom of the outer tube. To be done. That is, the fluid is a liquid liquefied gas in the inner pipe, a gas-liquid mixed state in the middle pipe, and a gas in the outer pipe.

As described above, the liquefied gas introduced into the heat transfer tube is gradually heat-exchanged with the heating fluid as the heat source by the heat transfer tube having the triple structure, so that the liquefied gas in the inner tube is cooled by heat. Is not directly transmitted to the heating fluid, and as a result, the outer peripheral surface of the outer tube is not extremely cooled, and no icing layer is formed on the outer peripheral surface of the outer tube (that is, the outer peripheral surface of the heat transfer tube). .

Further, since vaporization does not occur in the inner pipe in which the liquefied gas is in a downward flow, pressure pulsation in the pipe caused by vaporization in the downward flow does not occur, and as a result, so-called fluid-related vibration vaporization device. Can effectively prevent damage.

Further, since the vaporization of the liquefied gas is carried out by the upward flow, the liquid head can be used for distribution from the LNG header to each heat transfer tube, and stable distribution is easy.

According to the apparatus for vaporizing low-temperature liquefied gas according to the above-mentioned claim 2, since the heating chamber which is a space without the middle pipe and the inner pipe is formed in the lower portion of the outer pipe, heating in this heating chamber is performed. All the heat of the working fluid is used for heating the gas, and the amount of the low temperature due to the vaporization of the liquefied gas in the middle pipe is recovered to a temperature that can be supplied to the user.

According to the low-temperature liquefied gas vaporizer of the third aspect, since the outer peripheral surface of the inner pipe is subjected to the heat insulating treatment, heat transfer is suppressed in the inner pipe by this heat insulating treatment. It becomes easier to keep the liquefied gas in the tube in a liquid state.

According to the low-temperature liquefied gas vaporizer of the fourth aspect, the inner annular fluid passage formed between the outer peripheral surface of the inner pipe and the inner peripheral surface of the middle pipe, and the outer peripheral surface of the middle pipe. Since one or both of the outer annular fluid passages formed between the inner peripheral surface of the outer tube and the outer peripheral fluid passage are formed in a spiral structure, the moving distance of the liquefied gas in each passage becomes long, and As the convection time in the passage of liquefied gas etc. becomes longer, the centrifugal force generated by the vortex flow of liquefied gas etc.
Heavy liquid droplets of liquefied gas or the like in a gas-liquid mixed state are attracted to the inner wall surface of the middle pipe in the middle pipe, which contributes to heat exchange and makes it possible to increase heat exchange efficiency.

[0031]

FIG. 1 is a cross-sectional side view of a heat transfer tube applied to a low temperature liquefied gas vaporizer according to the present invention, and FIG.
It is the sectional view on the AA line of FIG. An overall view of the vaporizer according to the present invention is omitted. However, the structure is basically the same as that shown in FIG. 7 described above, but the vertical positional relationship between the LNG (liquefied natural gas) manifold 1 and the NG (natural gas) manifold 5 is as shown in FIG. The LNG manifold 1 is arranged in the upper part and the NNG is arranged in the lower part.
A G manifold 5 is provided.

Therefore, in the prior art, LNG was introduced from the lower part of the heat transfer tube 3a shown in FIG. 7 to become NG and was withdrawn from the upper part of the heat transfer tube 3a, but in the heat transfer tube 30 of the present invention, LNG is As shown in FIG. 1, the heat transfer tubes 30 are introduced from the upper portion and led out from the lower portion.
A large number of such heat transfer tubes 30 extending in the vertical direction of the present invention are arranged side by side so as to abut each other to form a panel 3 as shown in FIG. 7.

Further, in the low temperature liquefied gas vaporizer of the present invention, the liquefied gas (represented by LNG in this embodiment) is circulated inside the heat transfer tubes 30 arranged in the vertical direction, and The heating fluid (seawater S) supplied from the trough 8 is supplied so as to flow down to the outer peripheral surface of the heat transfer tube 30, and the LN is exchanged by heat exchange between the seawater S and the LNG.
Basically, G is converted to vaporized gas (NG).

An LNG header 2 is branched to the LNG manifold 1 and an NNG header 5 is branched to the NG manifold 5.
The G header 4 is branched. A heat transfer tube 30 is provided between the LNG headers 1 and the NG header 4,
The NG headers 1 and the NG headers 4 are communicated with each other via the heat transfer tubes 30, and the LNG supplied from the LNG headers 1 is the LNG header 2, the heat transfer tubes 30, and the NG.
It is adapted to be led out to the NG manifold 5 through the header 4.

The heat transfer tube 30 according to the present invention includes an inner tube 31 and
It has a triple structure of a middle pipe 32 and an outer pipe 33. A liquefied gas inflow hole 31a is provided at the top of the inner pipe 31, and an outflow hole 31b that opens toward the inside of the middle pipe 32 is provided at the lower end. Further, a bottom portion 32b having a closed structure is formed at the lower end of the middle pipe 32, and an outflow hole 32a opened toward the inside of the outer pipe 33 at the top.
Are formed.

Further, a ceiling-shaped ceiling portion 33b having a closed structure is provided at the top of the outer tube 33, and a gas delivery hole 33c for communicating with the NG header 4 is provided at the lower end. There is.

From the inner wall surface of the outer tube 33, a plurality of supporting projections 34 are provided to project toward the center, and the bottom 32b of the middle tube 32 is supported on the upper portions of the plurality of supporting projections 34. It has become.

In such a heat transfer tube 30, an inner annular fluid passage 41 is formed between the outer peripheral surface of the inner tube 31 and the inner peripheral surface of the middle tube 32, and the outer peripheral surface of the middle tube 32 and the outer tube 33.
An outer annular fluid passage 42 is formed between the inner annular surface and the inner peripheral surface. Further, the outer annular fluid passage 42 is hung in the space below the supporting protrusion 34 inside the outer pipe 33.
A heating chamber 37 for heating G is formed, and a gas delivery hole 33c for delivering vaporized NG is provided at the lower end of the heating chamber 37.

On the outer peripheral surface of the inner tube 31, a heat insulating layer 50 that has been subjected to a heat insulating process is formed. In the case of the present embodiment, the heat insulating layer 50 is formed by winding a known heat insulating material such as glass wool or foaming synthetic resin around the outer peripheral surface of the inner tube 31, but the heat insulating layer 50 according to the present invention is as follows. It is not limited to the winding of a heat insulating material, for example, as shown in FIG.
Alternatively, the heat insulating layer 50a may be formed by the outer jacket portion 51 and the heat insulating chamber 52 as shown in FIG. 4 which is a cross-sectional view taken along the line BB.

That is, the heat insulating layer 50a is composed of an outer jacket portion 51 surrounding the outer peripheral surface of the inner tube 31 and an annular heat insulating chamber 52 formed between the outer jacket portion 51 and the outer peripheral surface of the inner tube 31. The heat insulating effect is enhanced by the self-vaporized gas staying in the heat insulating chamber 52. It should be noted that brass wool, rock wool, foamable synthetic resin, or the like may be loaded in the heat insulating chamber 52 to suppress gas convection and further increase the heat insulating effect.

In the present invention, the heat insulating layer 5
The attachment of 0 and 50a to the outer peripheral surface of the inner pipe 31 is performed by the LNG in consideration of the thermodynamic heat balance of the heat transfer pipe 30.
It is performed under the design condition that vaporization does not result in NG while moving inside. Further, regarding the diameters and lengths and thicknesses of the inner pipe 31, the middle pipe 32, and the outer pipe 33, as well as the materials constituting them, the thermodynamics of the heat input from the seawater S and the heat output carried away by the LNG. The design calculation is executed and determined by a predetermined known method in consideration of the heat balance. As a result of such a design calculation, LNG descends in a liquid state in the inner pipe 31 and rises in a gas-liquid mixed state while vaporizing the inner annular fluid passage 41,
The outer annular fluid passage 42 is completely NG, and the heating chamber 37 is configured to raise the temperature of the NG to a predetermined temperature.

Since the low-temperature liquefied gas vaporizer of the present invention is constructed as described above, the LNG headers 1 to L are
LNG supplied to the heat transfer tube 30 via the NG header 2
Is first introduced into the inner pipe 31 and descends in a liquid state. At this time, LNG and NG rising in the inner annular fluid passage 41
The heat of the seawater S overflowing from the trough 8 is received via the gas-liquid mixture consisting of and the inner wall of the inner pipe 31, but the heat insulating layer 50 or the heat insulating layer 50a is formed on the outer peripheral surface of the inner pipe 31. Therefore, the LNG in the inner pipe 31 is suppressed by these and the temperature does not rise so much, and the bottom portion 3 of the middle pipe 32 is kept in a liquid state.
Reach 2b.

The LNG reaching the bottom 32b of the middle tube is
From there, the heat of the seawater S rises through the inner annular fluid passage 41 and the heat of the seawater S is rejected in the outer annular fluid passage 42 and the middle pipe 32.
Is supplied through the tube wall of the inner annular fluid passage 41 in the gas-liquid mixed state.
Rise inside.

When the LNG reaches the outflow hole 32a of the middle pipe 32, the LNG becomes almost completely NG and descends the outer annular fluid passage 42 to reach the heating chamber 37. This heating greenhouse 3
In 7, the NG receives heat from the seawater S via the tube wall of the outer tube 33 to further raise the temperature. After that, the NG is led to the NG manifold 5 via the gas delivery hole 33c.

The LN introduced into the heat transfer tube 30 in this way
Since the heat exchange between G and the seawater S that is the heating fluid as a heat source is performed stepwise by the heat transfer tube 30 having the triple structure, the cold heat of the LNG in the inner tube 31 is not directly transmitted to the heating fluid. As a result, the outer peripheral surface of the outer tube is not extremely cooled, and the ice accretion layer is not formed on the outer peripheral surface of the outer tube (that is, the outer peripheral surface of the heat transfer tube).

Further, the inner pipe 3 in which LNG is in a downward flow
Since vaporization does not occur within 1, the pressure pulsation in the pipe caused by vaporization in the downward flow does not occur, and as a result, damage to the vaporizer due to so-called fluid-related vibration can be effectively suppressed.

Since the heating chamber 37, which is a space in which the middle pipe 32 does not exist, is formed in the lower half of the outer pipe 33, all the heat of the seawater S is due to the NG heating in this heating chamber 37 portion. LNG in the middle pipe 32 used for
The NG, which has been cooled to a low temperature due to the vaporization, is recovered to a temperature at which it can be supplied to the user.

Further, a heat insulating layer 50 is formed on the outer peripheral surface of the inner pipe 31,
If the heat insulating layers 50 and 50a are formed, the heat transfer to the inner pipe 31 is suppressed by forming the heat insulating layer 50a, and the LNG in the inner pipe 31 can be more easily held in a liquid state.

FIG. 5 is a partially cutaway perspective view showing another example of the heat transfer tube. In the case of this example, the middle pipe 32 and the outer pipe 33
A plurality of spiral ribs 60 are projected on the inner wall surface of the, and the spiral passages 70 having a spiral structure are formed in the inner annular fluid passage 41 and the outer annular fluid passage 42 by the ribs 60. By constructing the annular fluid passages 41 and 42 in this way, the moving distance of LNG or NG in each passage becomes longer, the convection time in the passage becomes longer correspondingly, and especially in the inner annular fluid passage 41. , Due to the centrifugal force generated by the vortex flow of the fluid, a heavy liquid droplet (that is, LN
G) is attracted to the inner wall surface of the middle pipe 32, which contributes to heat exchange, which makes it possible to increase heat exchange efficiency.

FIG. 6 is a partially cutaway perspective view showing another example of the heating chamber for the outer tube. In the case of this example, a cross twist tape heat transfer promoting body 80, which is a spiral member, is installed in the heating chamber 37 formed in the lower portion of the outer tube 33 to divide the heating chamber 37 into four, and each of them is spiraled. The heating chamber 37a is formed. Therefore, the spiral heating chamber 37a increases the moving distance of NG, and the efficiency of heat exchange is correspondingly increased.
Further, if a spiral heat transfer fin is provided on the outer peripheral surface of the outer tube 33, the heat transfer area is increased, which also contributes to an increase in heat exchange efficiency.

[0051]

As described above, in the vaporizer of low temperature liquefied gas according to the present invention, the liquefied gas is circulated inside the heat transfer tubes arranged in the vertical direction, and the heating fluid is provided on the outer peripheral surface of the heat transfer tubes. Is supplied so that the liquefied gas is vaporized by heat exchange between the heating fluid and the liquefied gas, in the vaporizer of the low-temperature liquefied gas, the heat transfer tube includes an inner tube and a middle tube. It has a triple structure with an outer pipe, and a liquefied gas inflow hole is provided at the top of the inner pipe and an outflow hole opening toward the inside of the middle pipe is provided at the lower end, and the lower end of the middle pipe is the bottom. Is provided with an outflow hole that is open toward the inside of the outer tube, and the top of the outer tube is a closed structure with a ceiling, and a vaporized gas delivery hole is provided at the lower end. It is provided.

Therefore, the liquefied gas supplied from the top of the heat transfer tube consisting of the inner tube, the middle tube and the outer tube is first supplied from the liquefied gas inflow hole of the inner tube into the inner tube, and then the liquefied gas from the outflow hole of the lower end to Move into the pipe. The liquefied gas that has moved into the middle pipe rises in the middle pipe and moves into the outer pipe from the outflow hole in the upper part.

On the other hand, since the heating fluid flows down the outer peripheral surface of the heat transfer tube (outer tube), the heating fluid and the fluid in the outer tube (gas in which the liquefied gas is vaporized) pass through the wall surface of the outer tube. The heat exchange is performed by the heat exchange, and the heat exchange is performed between the fluid in the outer pipe and the fluid in the middle pipe through the wall surface of the middle pipe. Further, heat exchange is performed between the fluid in the middle pipe and the fluid in the inner pipe via the wall surface of the inner pipe.

As described above, since the liquefied gas supplied to the inner pipe receives heat from the heating fluid via the fluid existing between the wall surfaces of the triple layer, the heat receiving amount is small, Although the temperature rises in the inner tube, it remains liquid. Then, the fluid whose temperature has risen rises in the middle pipe, and while receiving heat from the heating fluid from the intermediate wall surface through the wall surface of the outer tube and the fluid inside the outer tube, vaporization is started.

The fluid descending from the upper part of the outer tube into the outer tube receives the heat of the heating fluid via the wall surface of the outer tube, is completely vaporized, and is led out of the system from the gas delivery hole at the bottom of the outer tube. To be done. That is, the fluid is a liquid liquefied gas in the inner pipe, a gas-liquid mixed state in the middle pipe, and a gas in the outer pipe.

As described above, the liquefied gas introduced into the heat transfer tube is gradually heat-exchanged with the heating fluid as the heat source by the heat transfer tube having the triple structure, so that the liquefied gas in the inner tube is cooled by heat. Is not directly transmitted to the heating fluid, and as a result, the outer peripheral surface of the outer tube is not extremely cooled, and no icing layer is formed on the outer peripheral surface of the outer tube (that is, the outer peripheral surface of the heat transfer tube). .

Further, since vaporization does not occur in the inner pipe in which the liquefied gas is in the downward flow, pressure pulsation in the pipe caused by vaporization in the downward flow does not occur, and as a result, so-called fluid-related vibration vaporizer Can effectively prevent damage.

Further, since the vaporization is carried out by the ascending flow, the liquid head can be used for distributing the heat transfer tubes, and stable distribution is easy.

By forming a warming room in the lower part of the outer tube, which is a space without the middle tube and the inner tube, all the heat of the heating fluid is used for heating the gas in this warming room. In order to reduce the construction cost and running cost, it is possible to recover the temperature that was low due to the vaporization of the liquefied gas in the middle pipe to the temperature that can be supplied to the user, and it is not necessary to provide a separate heating device. It is valid.

Further, if the outer peripheral surface of the inner pipe is heat-insulated, heat transfer is suppressed in the inner pipe by this heat-insulating treatment, and it becomes easier to keep the liquefied gas in the inner pipe in a liquid state. .

In addition, an inner annular fluid passage formed between the outer peripheral surface of the inner pipe and the inner peripheral surface of the middle pipe, and between the outer peripheral surface of the middle pipe and the inner peripheral surface of the outer pipe. If one or both of the outer annular fluid passages are formed in a spiral structure, the moving distance of the liquefied gas in each passage becomes long, and the convection time in the passage of the liquefied gas becomes long,
Due to the centrifugal force generated by the vortex flow of the liquefied gas, the heavy liquid droplets in the liquefied gas in the gas-liquid mixed state are attracted to the inner wall surface of the middle pipe, which contributes to heat exchange.
As a result, the heat exchange efficiency can be increased, which is convenient.

[Brief description of drawings]

FIG. 1 is a side sectional view of a heat transfer tube applied to a low-temperature liquefied gas vaporizer according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a partially cutaway side view illustrating an inner tube.

FIG. 4 is a sectional view taken along line BB of FIG.

FIG. 5 is a partially cutaway perspective view showing another example of the heat transfer tube.

FIG. 6 is a partially cutaway perspective view showing another example of a greenhouse for an outer tube.

FIG. 7 is a schematic perspective view showing an example of an open rack vaporizer (LNG vaporizer).

FIG. 8 is a partially cutaway perspective view showing an example of a conventional heat transfer tube.

[Explanation of symbols]

 1 LNG Headers 2 LNG Header 3 Panel 3a, 30 Heat Transfer Tube 3b Ice Layer 4 NG Header 5 NG Manifold 6 Seawater Header 7 Sprinkling Nozzle 8 Trough 30 Heat Transfer Tube 31 Inner Tube 31a Inlet Hole 31b Outlet Hole 32 Middle Tube 32a Outlet Hole 32b Bottom 33 Outer tube 33b Ceiling 33c Gas delivery hole 50, 50a Heat insulating layer 51 Outer shell 52 Heat insulating chamber 60 Rib 70 Spiral passage 80 Cross twist tape Heat transfer accelerator LNG Liquefied natural gas NG Natural gas

Claims (4)

[Claims] 1. A liquefied gas is circulated inside a heat transfer tube arranged in a vertical direction, and a heating fluid is supplied so as to flow down to the outer peripheral surface of the heat transfer tube. In a low-temperature liquefied gas vaporizer configured so that the liquefied gas is vaporized by heat exchange with the gas, the heat transfer tube has a triple structure of an inner tube, a middle tube, and an outer tube, and is provided at the top of the inner tube. An inflow hole for liquefied gas is provided, and an outflow hole that opens toward the inside of the middle pipe is provided at the lower end.The lower end of the middle pipe has a closed structure with a bottom, and the top portion faces the inside of the outer pipe. A low-temperature liquefied gas vaporizer characterized in that the outer pipe has a closed structure with a ceiling at the top and a vaporized gas delivery hole at the lower end. . 2. A heating chamber, which is a space without a middle pipe and an inner pipe, is formed below the outer pipe, and a vaporized gas delivery hole is provided at the lower end of the heating chamber. The low-temperature liquefied gas vaporizer according to claim 1. 3. The low-temperature liquefied gas vaporizer according to claim 1, wherein the outer peripheral surface of the inner pipe is heat-insulated. 4. An inner annular fluid passage formed between the outer peripheral surface of the inner pipe and the inner peripheral surface of the middle pipe, and formed between the outer peripheral surface of the middle pipe and the inner peripheral surface of the outer pipe. 4. The low-temperature liquefied gas vaporizer according to claim 1, wherein either or both of the outer annular fluid passages are formed in a spiral structure.