JP5173639B2 - Natural gas processing equipment and liquefied natural gas carrier - Google Patents

Description

  The present invention relates to a natural gas processing facility and a liquefied natural gas carrier ship (LNG ship) equipped with the same.

In the LNG ship, low-temperature liquefied natural gas is stored in a cargo tank at atmospheric pressure and transported. This liquefied natural gas (LNG) is evaporated by heat input into the cargo tank, and accumulates in the cargo tank as boil-off gas. As a result, the pressure in the cargo tank increases, and it is necessary to continuously extract a part of the cargo tank.
In order to effectively use this boiled gas, almost all LNG ships use boil-off gas as fuel for boilers, gas-fired internal combustion engines, etc., to add propulsive force and inboard power.

By the way, when the amount calculated | required as a fuel with respect to the quantity of the generated boil-off gas is small, excess boil-off gas will be discharged | emitted out of a ship, ie, will be thrown away wastefully. In particular, the loss becomes large when berthing or low-speed navigation is performed for a long time in a loaded state.
In order to suppress this loss, an LNG ship including a reliquefaction device that reliquefies excess boil-off gas and returns it to the cargo tank has been proposed (see Patent Document 1).

JP 2001-132898 A

For example, when natural gas such as boil-off gas is used as boiler fuel, the required natural gas pressure is low, so if it is re-liquefied with a re-liquefaction device as it is, the efficiency will deteriorate. Moreover, if reliquefaction is performed with low efficiency, the reliquefaction apparatus becomes larger in order to process the same predetermined amount.
Therefore, in order to increase the pressure of the natural gas supplied to the reliquefaction apparatus, it has been proposed to install a compressor in the natural gas supply line.

By the way, a normal compressor used in a ship uses a motor to drive it. Since this motor is disposed between the compressor and the bulkhead, a bulkhead seal is required. In addition, a speed reducer is interposed to adjust the rotational speed of both. For this reason, a large installation space is required, and electric power is required as power for operating the motor.
Further, even if two fuel supply compressors installed in parallel as in Patent Document 1 (one is originally provided as a spare) are used, the piping and operation control of related parts are complicated. After all, a large installation space is required. Moreover, the motive power which drives it is required. It does not perform the original function of spare. On the other hand, a two-stage compressor can be used, but it becomes difficult to share with a conventional boiler supply (one-stage compression), and a dedicated additional equipment is required.
If the reliquefaction equipment-related structure becomes large in this way, for example, when installing a reliquefaction equipment on an LNG ship that uses natural gas such as existing boil-off gas as boiler fuel, it will be drastically including the removal of the existing system. Remodeling work is required, which is not realistic.

  In view of the above problems, an object of the present invention is to provide a natural gas processing facility that can be installed in a small space as a small and highly efficient reliquefaction plant.

In order to solve the above problems, the present invention employs the following means.
That is, the natural gas processing facility according to the present invention includes a fuel supply line that compresses natural gas by a fuel compressor and supplies the fuel to the boiler, and a natural gas that takes in and conveys the natural gas compressed by the fuel compressor. A re-liquefaction plant having a gas transfer line and a refrigeration cycle section for cooling and re-liquefying the natural gas transferred in the natural gas transfer line by a circulating refrigerant, wherein the refrigeration cycle The section includes a first booster compressor that compresses the refrigerant circulated along the refrigerant flow path, and expands the refrigerant that has been compressed and then cooled to lower the temperature and drives the first booster compressor first expander and the said in the refrigerant flow path the first booster compressor first expander that The branch above first expander between the interposed branch flow path merge at the downstream side, and a second expander for expanding the refrigerant flowing through the branch flow path, is provided with, the native The gas transport line is provided with a second booster compressor that is driven by the second expander and compresses the natural gas.

  In the refrigeration cycle unit, for example, a refrigerant is circulated along the refrigerant flow path by a refrigerant compressor. The refrigerant cooled after being compressed by the refrigerant compressor is cooled again after being compressed by the first booster compressor. This refrigerant is divided into a refrigerant flow path and a branch flow path at the upstream position of the first expander and is sent. The refrigerant that has passed through the refrigerant flow path is depressurized and expanded by the first expander, so that the temperature is further lowered. The first expander takes out the force when the refrigerant expands as a rotational force, and rotates the booster compressor via the directly connected shaft. On the other hand, the refrigerant that has passed through the branch flow path is decompressed and expanded by the second expander to be further cooled, and merges with the refrigerant that has been cooled to the low temperature by the first expander. This low-temperature state refrigerant cools the surroundings by giving the cold to the surroundings, for example, condenses natural gas conveyed in a natural gas conveyance line. Thereafter, the refrigerant is sent to the refrigerant compressor to complete one cycle.

The fuel supply line compresses the boil-off gas generated in the cargo tank and the natural gas obtained by gasifying the liquefied natural gas in the cargo tank by the fuel compressor and supplies it as fuel to the boiler.
When this natural gas is left over, or at all times, the natural gas that has exited the fuel compressor is extracted and transported through a natural gas transport line. This natural gas is compressed by the second booster compressor, cooled and condensed by the low-temperature refrigerant conveyed through the refrigerant flow path. The condensed natural gas is separated into a liquefied natural gas which is a liquid component and a natural gas which is a gas by a gas-liquid separator. The liquefied natural gas is returned to the cargo tank.
Thus, since natural gas is compressed twice by the fuel compressor and the second booster compressor, heat exchange with the refrigeration cycle unit can be performed efficiently. Thereby, size reduction of a reliquefaction plant can be achieved.

Moreover, since the second booster compressor is driven by the rotational force when the refrigerant taken out by the second expander of the refrigeration cycle section expands, a member for driving it separately is unnecessary. In addition, combined with the simplicity of the structure itself, the reliquefaction plant can be further downsized.
Further, since the power for driving the second booster compressor is obtained from the refrigerant passing through the second expander, additional power such as electric power for driving the second booster becomes unnecessary, and energy efficiency is improved by improving the efficiency of the nitrogen cycle. it can.
Thus, the reliquefaction plant can be made small and highly efficient, and the installation space can be reduced. For this reason, for example, when a reliquefaction plant is installed in a natural gas carrier using natural gas such as existing boil-off gas as boiler fuel, the remodeling work can be greatly reduced. In addition, even when applied to new ships, design changes can be easily made.

Moreover, in the said invention, it is desirable to provide the cooling member which cools the said natural gas supplied to said 2nd booster compressor.
Since the natural gas introduced into the second booster compressor is thus cooled by the cooling member, the compression efficiency in the second booster compressor can be improved.
Thereby, since heat exchange with a refrigerating cycle part can be performed more efficiently, size reduction of a reliquefaction plant can be achieved.

Moreover, in the said invention, the said cooling member is good also as a slow-heater which sprays and cools a part of liquefied natural gas reliquefied to the said natural gas through the said natural gas conveyance line.
This eliminates the need for a separate cooling heat source, simplifying the piping and reducing the size of the reliquefaction plant.

  Moreover, in the said invention, the junction part to the said refrigerant flow path of the said branch flow path is made into the high temperature position where the refrigerant temperature in the said refrigerant flow path is higher than the refrigerant temperature in the position immediately after said 1st expander. Also good.

In this case, the refrigerant temperature at the high temperature position is determined by the amount of refrigerant flowing through the refrigerant flow path and the refrigerant temperature, and the amount of refrigerant flowing from the branch flow path and the refrigerant temperature. Thus, the refrigerant temperature at the high temperature position can be set as appropriate.
During the heat exchange between the refrigerant and the natural gas, the state of the refrigerant is maintained in a gaseous state, so that the rate of temperature increase is substantially constant. On the other hand, natural gas changes its state in the form of gas, mixture of gas and liquid, and liquid state. For example, the state changes further when impurities such as nitrogen are contained. The temperature drop rate varies. For this reason, deviation arises in the temperature change of a refrigerant and natural gas.
In this invention, since the temperature of the refrigerant | coolant in a high temperature position can be adjusted, the deviation in the temperature change of a refrigerant | coolant and natural gas can be corrected in this high temperature position. Therefore, the heat exchange efficiency between the refrigerant and natural gas can be improved.

  A liquefied natural gas carrier according to the present invention is equipped with the above-described natural gas processing equipment.

According to the liquefied natural gas carrier of the present invention, since the natural gas processing equipment using a compact reliquefaction plant is mounted, the installation space required for these can be reduced.
For this reason, for example, when a reliquefaction plant is installed in a natural gas carrier using natural gas such as existing boil-off gas as boiler fuel, the remodeling work can be greatly reduced. In addition, even when applied to new ships, design changes can be easily made.

According to the present invention, the first expander and the second expander are installed in parallel in the refrigeration cycle unit, and the natural gas transport line is driven by the second expander to supply natural gas. Since the second booster compressor for compression is provided, heat exchange between the natural gas and the refrigerant can be performed efficiently, and the reliquefaction plant can be downsized.
Further, since the second booster compressor is driven by the rotational force when the refrigerant taken out by the second expander of the refrigeration cycle section expands, a separate member for driving it is unnecessary, and the structure Combined with its simplicity, the reliquefaction plant can be further downsized.
Further, since the power for driving the second booster compressor is obtained from the refrigerant passing through the second expander, no external power for driving the second booster compressor is required, saving space and energy.
Thus, the reliquefaction plant can be made small and highly efficient, and the installation space can be reduced. For this reason, for example, when a reliquefaction plant is installed in a natural gas carrier using natural gas such as existing boil-off gas as boiler fuel, the remodeling work can be greatly reduced. In addition, even when applied to new ships, design changes can be easily made.

Below, the natural gas processing equipment 1 of the LNG ship concerning one Embodiment of this invention is demonstrated using FIG. 1 and FIG.
FIG. 1 is a block diagram showing an overall schematic configuration of a natural gas processing facility 1 of an LNG ship. The LNG ship includes a plurality of cargo tanks 5 that store liquefied natural gas (hereinafter sometimes referred to as LNG) 3. There are various types of cargo tanks 5. For example, a moss-type tank has a substantially spherical shape as shown in FIG.
The natural gas processing facility 1 includes a fuel supply line 7 and a reliquefaction processing unit (reliquefaction plant) 9.

The fuel supply line 7 gasifies the LNG 3 stored in the cargo tank 5 and supplies it to the burner 13 of the boiler 11 as fuel.
The fuel supply line 7 includes a BOG pipe 17 that transports the boil-off gas 15 generated in the cargo tank 5, an LNG pipe 19 that transports the LNG 3 in the cargo tank 5 by being vaporized by the vaporizer 21, and a BOG pipe 17 and A mist separator 23 into which natural gas conveyed by the LNG pipe 19 flows, a fuel pipe 24 that conveys natural gas from the mist separator 23 to the boiler 11, and a compressor for fuel that compresses the natural gas conveyed by the fuel pipe 24. 25, a gas heater 27 that heats the natural gas compressed by the fuel compressor 25, and a gas flow rate control valve 28 that adjusts the flow rate of the natural gas.

The mist separator 23 has a function of removing the liquid component.
Two fuel compressors 25 having the same structure are arranged in parallel, and one of them is set as a spare in the event of a failure. The fuel compressor 25 is configured to be driven by a motor.
The two fuel compressors 25 are provided with a free flow line 29 in which the fuel compressors 25 are not installed in parallel. The free flow line 29 is provided with an on-off valve 31 that opens and closes and a check valve 33 that prevents inflow from the outlet side of the fuel compressor 25.
The free flow line 29 is used, for example, to supply natural gas to the boiler 11 with the pressure on the mist separator 23 side when the two fuel compressors 25 are stopped.

The reliquefaction processing unit 9 reliquefies excess natural gas or the like.
The reliquefaction processing unit 9 includes a refrigeration cycle unit 35 and a liquefaction processing unit 37.
The refrigeration cycle unit 35 is a refrigerant circulated through a refrigeration pipe (refrigerant channel) 39 (for example, nitrogen is used as the refrigerant. In addition, for example, hydrogen and helium are targets). The cold heat is supplied to the liquefaction processing unit 37.
The refrigeration cycle unit 35 includes a refrigerant compressor 41, a booster compressor (first booster compressor) 43, a cold expander (first expander) 45, a precooler 47, a condenser 49, and a supercooler. 51 is provided as a main element.

  The refrigeration cycle section 35 is provided with a refrigeration pipe 39 that configures a closed system by connecting these elements. The refrigeration pipe 39 includes a precooling pipe section 53 that enters the cold expander 45 via the booster compressor 43, the precooler 47 and the condenser 49, and the cold expander 45, the supercooler 51, the condenser 49, and the precooler 47. And a cooling pipe portion 55 that enters the refrigerant compressor 41 via the.

The refrigerant compressor 41 is a two-stage centrifugal compressor driven by a steam turbine 57. In addition, in a ship without a driving steam facility (diesel propulsion ship or the like), a motor drive having a compressor speed control function may be used. In addition, the refrigerant compressor 41 is not limited to this type, and a suitable type such as a screw compressor can be used as long as it generates a differential pressure in the refrigeration pipe 39.
The refrigerant compressor 41 sucks and compresses a low-temperature / low-pressure gaseous refrigerant to form a high-temperature / high-pressure gaseous refrigerant.
The refrigerant compressor 41 has an intercooler 59. A first aftercooler 61 is provided between the refrigerant compressor 41 and the booster compressor 43.
In order to adjust the amount of refrigerant, a pipe having a refrigerant buffer tank 63 is connected before and after the refrigerant compressor 41.

The booster compressor 43 compresses the refrigerant introduced from the first aftercooler 61 so that the refrigerant is heated to a high temperature and a high pressure, and is supplied to the preliminary cooling pipe unit 53. A second aftercooler 65 is provided on the downstream side of the booster compressor 43.
The cold expander 45 expands the refrigerant whose temperature has been lowered through the second aftercooler 65, the precooler 47, and the condenser 49 by decompression to form a low-temperature and low-pressure gaseous refrigerant. The booster compressor 43 connected coaxially with the cold expander 45 is rotated using the force when the refrigerant expands as a rotational force.
The low-temperature and low-pressure gaseous refrigerant from the cold expander 45 is sequentially sent to the supercooler 51, the condenser 49 and the precooler 47 through the cooling pipe 55 to exchange heat.

A branch pipe (branch) connecting the branch point A between the precooler 47 and the condenser 49 in the precooling pipe part 53 and the junction point B between the condenser 49 and the subcooler 51 in the cooling pipe part 55. A flow path) 67 is provided. Since the branch point A is upstream of the cold expander 45 and the junction (junction portion, high temperature position) B is downstream of the cold expander 45, the branch pipe 67 connects the front and rear of the cold expander 45.
Since the condenser 49 exists between the branch point A and the cold expander 45, the refrigerant temperature at the branch point A is higher than the refrigerant temperature at the inlet of the cold expander 45.
Since the supercooler 51 exists between the junction B and the cold expander 45, the refrigerant temperature at the junction B is higher than the refrigerant temperature at the outlet of the cold expander 45.

The branch pipe 67 is provided with a hot expander (second expander) 69 that expands the refrigerant passing through the branch pipe 67 by decompression to produce a low-temperature and low-pressure gaseous refrigerant.
A first bypass pipe 71 is provided between the upstream side of the booster compressor 43 in the refrigeration pipe 39 and the downstream side of the second aftercooler 65, which is connected / disconnected by opening / closing of a valve.
A second bypass pipe 73 is provided between the upstream side of the cold expander 45 in the refrigeration pipe 39 and the downstream side of the supercooler 51, which is connected / disconnected by opening / closing a valve.
When the refrigeration cycle unit 35 is started, the first bypass pipe 71 and the second bypass pipe 73 are opened. As a result, the refrigerant does not pass through the booster compressor 43 and the cold expander 45, so that the resistance due to them disappears and the refrigerant compressor 41 can be started.

The liquefaction processing unit 37 includes a natural gas supply pipe (natural gas transport line) 77 for transporting the natural gas compressed by the fuel compressor 25 to the separator 75, and LNG reliquefied from the separator 75 to the cargo tank 5. A reliquefied gas pipe 79 to be sent is provided.
The natural gas supply pipe 77 includes a slow heatr (cooling member) 81 for cooling the natural gas being conveyed, and a gas compression booster compressor (second booster compressor) 83 for compressing the natural gas from the slow heatr 81. , Is provided.
The gas compression booster compressor 83 is coaxially connected to the hot expander 69. Therefore, the gas expansion booster compressor 83 is rotated by rotating the hot expander 69 using the force when the refrigerant passing through the branch pipe 67 expands as a rotational force.

An LNG supply pipe 85 is branched from the reliquefied gas pipe 79. The slow heatr 81 reduces the temperature of the natural gas by spraying the LNG supplied from the LNG supply pipe 85 onto the natural gas from the fuel compressor 25.
The temperature of the natural gas supplied to the gas compression booster compressor 83 can be adjusted by adjusting the amount of LNG supplied to the slow heat generator 81 by the adjustment valve 87 provided in the LNG supply pipe 85.

The natural gas supply pipe 77 is connected to the upper part of the separator 75 through the condenser 49 after leaving the gas compression booster compressor 83. The natural gas conveyed by the natural gas supply pipe 77 is cooled and condensed by the refrigerant passing through the cooling pipe section 55 in the condenser 49.
The condensed natural gas is introduced into the separator 75 and separated into a liquid component and a gas component.
The reliquefied gas pipe 79 is connected to the cargo tank 5 from the lower part of the separator 75 through the supercooler 51.
The reliquefied gas pipe 79 is provided with a reliquefied gas flow rate adjustment valve 89 on the downstream side of the subcooler 51.

A gas supply pipe 91 having a flow rate adjusting valve connected from the top of the separator 75 to the junction C on the upstream side of the slow heat generator 81 in the natural gas supply pipe 77 is provided.
A gas supply branch pipe 93 provided with a flow rate adjusting valve connected from the gas supply pipe 91 to the fuel pipe 24 is branched.

The cold expander 45, the hot expander 69, the precooler 47, the condenser 49, and the supercooler 51 are housed compactly in a device block 95 having a substantially rectangular parallelepiped shape having a heat-proof structure.
Since the gas compression booster compressor 83 and the booster compressor 43 are small in size, they are attached to be embedded in the equipment block 95 as shown in FIG. Thereby, the gas compression booster compressor 83 and the booster compressor 43 are insulated simultaneously.

As shown in FIG. 1, the slow heatr 81 and the separator 75 are vertically arranged and attached inside a liquid column 97 having a substantially cylindrical shape.
The refrigerant compressor 41, the refrigerant buffer tank 63, and the steam turbine 57 are arranged in the engine room MR in which the boiler 11 is installed, and the equipment block 95 and the liquid column 97 are installed in the cargo equipment room CM.

Operation | movement of the natural gas processing equipment 1 concerning this embodiment demonstrated above is demonstrated.
In the refrigeration cycle unit 35, the refrigerant compressor 41 is driven by the steam turbine 57 to compress the low-temperature / low-pressure gaseous refrigerant introduced from the refrigeration pipe 39 into a high-temperature / high-pressure gaseous refrigerant.
This high-temperature and high-pressure gaseous refrigerant is cooled by the first aftercooler 61 and introduced into the booster compressor 43.
In the booster compressor 43, the introduced gaseous refrigerant is compressed and is again brought to high temperature and high pressure.

This refrigerant is sent to the preliminary cooling pipe section 53, cooled by the second aftercooler 65, and then cooled by the low-temperature and low-pressure gaseous refrigerant passing through the cooling pipe section 55 when passing through the precooler 47 and the condenser 49. Introduced into the cold expander 45.
The refrigerant introduced into the cold expander 45 is expanded by decompression to be a low-temperature / low-pressure gaseous refrigerant.
The low-temperature and low-pressure gaseous refrigerant is sent to the cooling pipe section 55, passes through the supercooler 51, and cools it by giving the cold to the surroundings.

On the other hand, a part of the refrigerant flowing through the preliminary cooling pipe portion 53 is branched from the branch point A on the downstream side of the precooler 47 to the branch pipe 67. The refrigerant flowing through the branch pipe 67 is introduced into the hot expander 69 and expanded by decompression to be a low-temperature and low-pressure gaseous refrigerant. This refrigerant is merged into the cooling pipe section 55 at the merge point B on the downstream side of the subcooler 51.
The refrigerant temperature at the junction B is determined by the refrigerant amount and refrigerant temperature after passing through the supercooler 51 and the refrigerant amount and refrigerant temperature that merge from the branch pipe 67.
Therefore, the refrigerant temperature at the junction B can be appropriately set by adjusting the refrigerant quantity and refrigerant temperature after passing through the supercooler 51 and the refrigerant quantity and refrigerant temperature joining from the branch pipe 67. .

When the refrigerant having joined at the junction B passes through the condenser 49 and the precooler 47, the refrigerant is cooled by giving the cold to the surroundings.
Thereafter, the refrigerant is sent to the refrigerant compressor 41 to complete one cycle.
In the refrigeration cycle unit 35, by performing this cycle continuously, subcooler 51 cooling pipe 55 passes, to provide a cold in the condenser 49 and the flop les cooler 47.

The boil-off gas 15 generated in the cargo tank 5 and the natural gas obtained by gasifying the LNG in the cargo tank 5 with the vaporizer 21 are mixed by the mist separator 23 and supplied to the fuel compressor 25 through the fuel pipe 24. . This natural gas is compressed by the fuel compressor 25, heated by the gas heater 27, and supplied as fuel to the burner 13 of the boiler 11.
At this time, the gas flow rate control valve 28 is controlled to automatically open and close in accordance with the amount of fuel required by the boiler 11.

When the natural gas is left or at all times, the natural gas that has exited the fuel compressor 25 is extracted and introduced into the slow heat generator 81 through the natural gas supply pipe 77.
The natural gas introduced into the slow heat generator 81 is cooled by spraying LNG supplied from the lower part of the separator 75 through the reliquefied gas pipe 79 and the LNG supply pipe 85.
The natural gas cooled by the slow heat generator 81 is compressed by a gas compression booster compressor 83 driven by a hot expander 69.
Thus, since the natural gas introduced into the gas compression booster compressor 83 is cooled by the slow heat generator 81, the compression efficiency in the gas compression booster compressor 83 can be improved.

In the condenser 49, the natural gas is cooled by the low-temperature and low-pressure gaseous refrigerant flowing through the cooling pipe section 55 of the refrigeration cycle section 35, and is supplied to the separator 75 in a saturated liquid state, that is, in a state where it is easily separated into gas and liquid. Sent.
In the separator 75 , the saturated natural gas is gas-liquid separated, and the liquid component is separated into the lower portion and the gas component is separated into the upper portion.
The lower LNG is returned to the cargo tank 5 through the reliquefied gas pipe 79.

As described above, the natural gas is compressed twice by being intermediate-cooled by the fuel compressor 25 and the gas compression booster compressor 83, so that heat exchange with the refrigeration cycle unit 35 can be performed efficiently. Thereby, size reduction of the refrigerating cycle part 35 can be achieved.
Moreover, since the compression efficiency in the gas compression booster compressor 83 can be improved, the gas compression booster compressor 83 can be downsized, and the equipment block 95 can be downsized.
Further, since the gas compression booster compressor 83 is driven by the rotational force when the refrigerant taken out by the hot expander 69 of the refrigeration cycle section 35 expands, a member for driving it separately is unnecessary. In addition, since the structure itself is simple, the device block 95, that is, the reliquefaction processing unit 9 can be further downsized.

Further, since the power for driving the gas compression booster compressor 83 is obtained from the refrigerant passing through the hot expander 69, no external power for driving the gas compression booster compressor 83 is required, and space and energy can be saved.
Thus, the reliquefaction processing unit 9 can be made small and highly efficient, and the installation space can be reduced. For this reason, for example, when installing the reliquefaction processing part 9 in the LNG ship which uses natural gas, such as the existing boil-off gas, as a fuel of a boiler, remodeling construction can be reduced significantly. In addition, even when applied to new ships, design changes can be easily made.

In the heat exchange between the refrigerant passing through the cooling pipe section 55 and the natural gas passing through the natural gas supply pipe 77 and the reliquefied gas pipe 79, the state of the refrigerant is maintained in a gaseous state, so that the rate of temperature increase is substantially constant. . On the other hand, natural gas changes in a gaseous state and a mixed state of gas and liquid in the condenser 49, and in a liquid state in the subcooler 51. For example, the state changes further when impurities such as nitrogen are contained. Therefore, even if the same amount of heat is given, the temperature decrease rate varies.
For this reason, deviation arises in the temperature change of a refrigerant and natural gas.

Since the refrigerant temperature and the refrigerant temperature after passing through the subcooler 51 and the refrigerant quantity and the refrigerant temperature that merge from the branch pipe 67 are appropriately set, the refrigerant temperature at the junction B can be set as appropriate. The deviation in the temperature change between the refrigerant and the natural gas can be corrected at the junction B.
Therefore, the heat exchange efficiency between the refrigerant and natural gas can be improved.

The low-temperature gas component accumulated in the upper portion of the separator 75 is sent to the natural gas supply pipe 77 at the junction C at the gas supply pipe 91, and the natural gas sent through the natural gas supply pipe 77 is cooled. The amount of cooling can be adjusted by adjusting the flow rate of the gas supply pipe 91 with the flow rate adjusting valve.
A part of the gas accumulated in the upper portion of the separator 75 is supplied to the fuel pipe 24 through the gas supply pipe 91 and the gas supply branch pipe 93 and supplied to the burner 13 of the boiler 11.

In addition, this invention is not limited to this embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, in this embodiment, the gas compression booster compressor 83 is directly connected to the hot expander 69 by a shaft. However, as shown in FIG. 3, the gas compression booster compressor 83 includes a generator 101 directly connected to the hot expander 69. Reference numeral 83 may be operated by a high-speed motor 103 that is directly driven by electric power generated by the generator 101.

Further, in this embodiment, so that branching from the branch point A between the branch pipe 67 and the flop les cooler 47 in the preliminary cooling pipe 53 and the condenser 49, flop les as shown in FIG. 4 You may make it branch from the branch point D of the upstream of the cooler 47. FIG.
Furthermore, as shown in FIG. 5, the branch pipe 6 7 branches from the branching position E between the condenser 49 and the cold expander 45 in the preliminary cooling pipe section 53, the subcooler in the cooling pipe section 55 51 You may make it merge at the confluence | merging point (junction part) F which is the upstream of this. In this case, the temperature of the refrigerant flowing into the cold expander 45 and the hot expander 69 is substantially the same, and the refrigerant temperature at the confluence F can be set by the difference in expansion between the cold expander 45 and the hot expander 69. However, since the converging point F is upstream of the subcooler 51, the effect of adjusting the temperature change rate of the refrigerant temperature to the subcooler 51 Karapu Les cooler 47 does not have.

  Recently, a compressor that has been miniaturized as a whole in combination with a motor has been proposed. Even if this is used instead of the gas compression booster compressor 83, the reliquefaction processing section 9 can be downsized to some extent. In this case, since it is necessary to separately supply electric power for driving the motor, a large amount of power is required as compared with the power source using the hot expander 69, which is slightly disadvantageous in terms of efficiency.

It is a block diagram which shows schematic structure of the natural gas processing equipment concerning one Embodiment of this invention. It is a perspective view which shows the apparatus block and liquid column concerning one Embodiment of this invention. It is a block diagram which shows another embodiment of the gas compression booster compressor concerning one Embodiment of this invention. It is a block diagram which shows another embodiment of the branch piping concerning one Embodiment of this invention. It is a block diagram which shows another embodiment of the branch piping concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Natural gas processing equipment 7 Fuel supply line 9 Reliquefaction processing part 11 Boiler 25 Fuel compressor 35 Refrigeration cycle part 39 Refrigerant piping 43 Booster compressor 45 Cold expander 67 Branch piping 69 Hot expander 77 Natural gas supply piping 81 Slow heat 83 Gas Compression Booster Compressor B, F Junction

Claims (5)

A fuel supply line that compresses natural gas with a fuel compressor and supplies it to the boiler;
A re-liquefaction plant having a natural gas transfer line that takes in and transfers the natural gas compressed by the fuel compressor, and a refrigeration cycle section that cools and re-liquefies the natural gas transferred in the natural gas transfer line by circulating refrigerant. A natural gas processing facility comprising:
The refrigeration cycle section includes a first booster compressor that compresses the refrigerant that is circulated along the refrigerant flow path, and expands the refrigerant that has been compressed and then cooled to lower temperature and the first booster. A first expander that drives a compressor, and a branch that branches between the first booster compressor and the first expander in the refrigerant flow path and joins downstream of the first expander A second expander interposed in the flow path and expanding the refrigerant flowing in the branch flow path,
A natural gas processing facility, wherein the natural gas transport line is provided with a second booster compressor that is driven by the second expander and compresses the natural gas.   The natural gas processing facility according to claim 1, further comprising a cooling member for cooling the natural gas supplied to the second booster compressor.   The natural cooling device according to claim 2, wherein the cooling member is a slow heat cooler that sprays and cools a part of the liquefied natural gas reliquefied through the natural gas transfer line to the natural gas. Gas processing equipment.   The junction part of the branch channel to the refrigerant channel is a high temperature position in which the refrigerant temperature in the refrigerant channel is higher than the refrigerant temperature immediately after the first expander. Item 4. A natural gas processing facility according to any one of Items 1 to 3.   A liquefied natural gas carrier ship equipped with the natural gas processing facility according to any one of claims 1 to 4.

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