JP2012017030A - Regasification plant of floating body structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a regasification plant of a floating body structure capable of reducing the power for supplying heating water, and adaptable to the floating structure under various kinds of environments.SOLUTION: The regasification plant of the floating body structure includes a propane loop heat exchanger 21 for preheating LNG with a mixture of paraffin hydrocarbon such as propane heated with sea water (heating water), an open-rack type heat exchanger 23 for heating and gasifying LNG preheated by the propane loop heat exchanger 21, and a sea water supply system 27 for supplying sea water (heating water) to the propane loop heat exchanger 21 and the open-rack type heat exchanger 23.

Description

  The present invention relates to a floating structure regasification plant for heating and gasifying a liquefied gas taken out from a storage tank of a floating structure such as an LNG ship.

As a regasification plant for gasifying liquefied gas installed on land, an open rack type plant is generally used.
An open rack regasification plant uses a liquefied gas to flow inside a box-shaped or pipe-shaped heat exchanger, and liquefies the internal heat by flowing, for example, seawater as an external heat source to the heat transfer surface of the heat exchanger. Gas is vaporized.
The open-rack regasification plant is economical to operate and is simple in structure, so it is easy to operate and maintain, and has high reliability and safety.

A recent liquefied natural gas (LNG) carrier ship (LNG ship) includes, for example, a regasification plant that regasifies LNG using power and a heat source in the ship as disclosed in Patent Document 1 or Patent Document 2. Some are provided.
This is called RV (Regification Vessel). For example, when an LNG receiving base is not provided on land, the LNG ship regasifies LNG on the ship and supplies it directly to the gas piping on land.
In addition, some FSRUs (Floating Storage and Regasification Units) moored at a predetermined place to store LNG and supply it to land include a regasification plant. As a heat source to be gasified, there are those using seawater as shown in Patent Documents 1 and 2, and those using shipboard steam.

  Such an LNG ship does not have an open rack type regasification plant. This is because the heat exchange part of the regasification plant shakes as the LNG ship shakes, so that the seawater is intermittently separated from the heat transfer surface of the heat exchange part, resulting in light and shade between the heat transfer surface and the seawater. . Since there is a temperature difference of about 200 ° C. between seawater and LNG, a portion that is not cooled by the heat transfer surface and a portion that is not cooled by the density of the seawater are generated, and a large thermal stress is generated between them. There is a possibility that the heat exchange part may be damaged by the repetition of the thermal stress. Moreover, since the open rack type regasification plant is large, it has been considered unsuitable for places with limited space such as onboard ships.

For this reason, as a regasification plant installed on an LNG ship, a cascade heating method using a relatively compact propane loop is used.
In the cascade heating method, LNG is heated in two stages. That is, first, LNG is heated by propane heated by seawater. Thereafter, the LNG heated to a certain level is directly heated by seawater in a shell-and-tube heat exchanger, for example.

In addition, various emission regulations have been implemented or are planned for the discharge of various substances from ships, but depending on the sea area, the total amount of seawater, such as cooling water and ballast water, or the total prohibition of seawater access, etc. Water intake restrictions may be imposed. There are differences depending on the location, such as the tendency of regulations to become stricter in developed countries.
Therefore, it is conceivable to regasify in various sea areas if it can move like an LNG ship, so it satisfies the regasification plant that can operate even in the most severely regulated sea areas, and similarly in loosely regulated sea areas. A system that can be operated is required.
The one disclosed in Patent Document 2 proposes a regasification plant that can be regasified without using seawater outside the ship.

Special Table 2002-506960 JP 2010-58772 A

By the way, in the regasification plant using the cascade heating method, the seawater that passes through the heat exchange section needs to have a certain high pressure, so that the pressure loss at the time of supply increases, and the required power for supply increases. There are challenges.
Thereby, when the supply piping of seawater becomes long, it is necessary to set it as high pressure | voltage resistant piping. Moreover, although the heating part by seawater considers corrosion resistance and is normally comprised, for example with a titanium material, there exists a subject that cost increases.

  In view of the above, the present invention is a floating structure that can partially reduce the pressure for supplying heated water, thereby reducing the power for supplying heated water, and can correspond to floating structures placed in various environments. The object is to provide a regasification plant for goods.

In order to solve the above problems, the present invention employs the following means.
That is, the regasification plant for a floating structure according to the present invention includes an intermediate medium type heat exchanger that preheats a liquefied gas with an intermediate medium heated with heated water, and a liquefaction preheated with the intermediate medium heat exchanger. An open rack heat exchanger that heats and liquefies liquefied gas by applying heated water to the gas, and a heated water supply system that supplies the intermediate medium heat exchanger and the open rack heat exchanger with heated water And is provided.

The heated water supply system supplies heated water as a heating source to the intermediate medium heat exchanger and the open rack heat exchanger.
The liquefied gas is first supplied to the intermediate medium heat exchanger. In the intermediate medium heat exchanger, the intermediate medium is heated with the heated water supplied by the heated water supply system, and the liquefied gas is heated by the heated intermediate medium to be heated. In other words, the liquefied gas is preheated by the intermediate medium. When the liquefied gas is heated, the intermediate medium is cooled. The cooled intermediate medium is heated again with heated water. By repeating this, the liquefied gas passing through the intermediate medium heat exchanger is continuously preheated.
As described above, in the intermediate medium heat exchanger, the liquefied gas and the heated water are not in direct contact with each other, so that the heated water can be prevented from freezing even in the initial stage of the liquefied gas heating with a large temperature difference.
As the intermediate medium, a mixture of paraffinic hydrocarbons such as propane is used.

The liquefied gas preheated by the intermediate medium heat exchanger is introduced into the open rack heat exchanger.
In an open rack heat exchanger, for example, a liquefied gas is caused to flow inside a box-shaped or pipe-shaped heat exchanger. The heated water supplied by the heated water supply system is caused to flow from the top to the bottom on the outer surface of the heat exchanging section, and heats and vaporizes the liquefied gas inside.
The heating water supplied to the open rack heat exchanger in this way is only flowed from the top to the bottom on the outer surface of the heat exchange section, so there is no need to increase the supply pressure of the heating water. In the water supply system, the supply pressure of the portion supplied to the open rack heat exchanger can be reduced. Therefore, the portion supplied to the open rack heat exchanger in the heating water supply system does not need to be a high pressure resistant pipe, and is therefore made of a relatively inexpensive material, thereby reducing the cost.

Since the liquefied gas introduced into the open rack heat exchanger is preheated and heated by the intermediate medium heat exchanger, the temperature difference from the heated water is small. Therefore, even if the open rack heat exchanger shakes as the floating structure shakes, and the heated water is intermittently peeled off from the outer surface of the heat exchanger, Since the amount of thermal stress generated between the part that is cooled and the part that is not cooled due to the density of water can be suppressed, the risk of damage to the open rack heat exchanger due to this thermal stress is suppressed. can do.
As described above, since the liquefied gas is subjected to severe initial heating by an intermediate medium heat exchanger, an inexpensive and highly reliable open rack heat exchanger is safely used for subsequent heating. In combination with the cost reduction of the heating water supply system, the regasification plant can be manufactured at low cost. Further, since the open rack heat exchanger is only used for the subsequent heating, it can be made relatively small and can be installed in a limited space of the floating structure.

  Moreover, in the regasification plant for a floating structure according to the present invention, the heating water supply system can select a first inboard storage section or a public water area as the heating water supply source, and the open rack heat exchange An open rack heating water supply system capable of selectively supplying the heating water from the open rack heat exchanger to the outside of the ship and a second inboard storage section as a heating water supply source. Heating water supply for heating an intermediate medium that can select public water areas, circulate and supply heated water to the intermediate medium heat exchanger and selectively discharge the heated water from the intermediate medium heat exchanger to the outside of the ship And a system.

As described above, the heating water supply system includes the open rack heating water supply system that circulates and supplies the heating water to the open rack heat exchanger, and the intermediate medium heating water that circulates and supplies the heating water to the intermediate medium heat exchanger. Divided into supply systems. In other words, since the heating water is supplied to the open rack type heat exchanger and the intermediate medium type heat exchanger independently, the inlet in the open rack heating water supply system or the heating water supply system for heating the intermediate medium The difference in temperature (ΔT) between the heating water temperature at the outlet and the heating water temperature at the outlet is the same at the inlet of the heating water supply system in which the open rack heat exchanger and the intermediate medium heat exchanger are communicated. The temperature difference (ΔT) between the heating water temperature and the heating water temperature at the outlet can be made smaller.
Therefore, liquefied gas can be gasified without increasing the amount of heated water circulating even in a sea area where the heated water temperature is low.

In the open rack heated water supply system, the first ship storage or public water area can be selected as the heated water supply source, and whether or not the used heated water is discharged to the public water area can be selected. In the heating water supply system for medium heating, since the second ship storage part or the public water area can be selected as the heating water supply source, and whether the used heating water is discharged to the public water area can be selected, for example, In places where strict emission regulations are not applied, efficient regasification can be performed by an open loop system that circulates heated water in public water bodies. Regasification can be performed by a closed loop system that circulates water (does not take or discharge heated water into public water bodies).
In this way, in the open rack heating water supply system and / or the intermediate medium heating water supply system, either one of the so-called closed loop method in which the heating water is not discharged to the outside according to the situation of the place, The loop method can be selected.

  Further, in the regasification plant for a floating structure according to the present invention, in the open rack heating water supply system, the heating water supplied to the open rack heat exchanger is heated using exhaust heat of the engine room. It is characterized by.

  In this way, since the temperature of the heated water supplied to the open rack heat exchanger is raised, stable gasification can be performed even in a cold sea area or the like even if the heated water is at a low temperature.

  Moreover, in the regasification plant for a floating structure according to the present invention, the second inboard storage part of the heating water supply system for heating the intermediate medium is supplied from the open rack heat exchanger in the open rack heating water supply system. The heating water is configured to be selectively received.

If it does in this way, it can be set as the heating water supply system with which the open rack heating water supply system and the heating water supply system for intermediate medium heating were continuous.
For example, when the heated water supplied to the open rack heat exchanger is heated using the exhaust heat of the engine room, this amount of heat can be utilized also in the heated water supply system for heating the intermediate medium.

In the regasification plant according to the present invention, an intermediate medium heat exchanger that heats the liquefied gas with an intermediate medium heated with heated water, and heated water is applied to the liquefied gas heated with the intermediate medium heat exchanger. And an open rack heat exchanger that heats and liquefies the liquefied gas, so that the supply pressure of the heating water supply system that supplies the heated water to the open rack heat exchanger can be reduced. And cost can be reduced.
Since the liquefied gas is subjected to severe initial heating with an intermediate medium heat exchanger, an inexpensive and highly reliable open rack heat exchanger can be safely used for subsequent heating, The regasification plant can be manufactured at low cost in combination with the cost reduction of the heating water supply system. Further, since the open rack heat exchanger is only used for the subsequent heating, it can be made relatively small and can be installed in a limited space of the floating structure.

It is a block diagram which shows schematic structure of the regasification plant concerning one Embodiment of this invention. It is a block diagram which shows the heating water supply state of the heating water supply system concerning one Embodiment of this invention. It is a block diagram which shows another heating water supply state of the heating water supply system concerning one Embodiment of this invention. It is a block diagram which shows another heating water supply state of the heating water supply system concerning one Embodiment of this invention. It is a block diagram which shows another heating water supply state of the heating water supply system concerning one Embodiment of this invention. It is a block diagram which shows another heating water supply state of the heating water supply system concerning one Embodiment of this invention.

Hereinafter, the regasification plant 1 concerning one Embodiment of this invention is demonstrated with reference to FIGS. This regasification plant 1 is installed in an LNG ship (floating structure) 3.
FIG. 1 is a block diagram showing a schematic configuration of a regasification plant 1.
Moreover, the heating water used in the present invention is, for example, seawater, fresh water, river water, groundwater, and the like. Here, the heating water will be described as seawater.
Moreover, the public water area which is a supply source of the heating water used for this invention is a sea, a river, a lake, etc., for example. Here, the public water area is described as a sea area.
The LNG ship 3 is provided with a storage tank (not shown) for storing liquefied natural gas (liquefied gas; hereinafter referred to as LNG).
At the rear of the LNG ship 3, an engine room 7 provided with a steam turbine plant is provided under the deck 5. The steam turbine plant in the engine room 7 includes a boiler (not shown) that generates superheated steam, a main machine (not shown) that is a turbine driven by superheated steam from the boiler, and a steam turbine that is driven by superheated steam from the boiler. (Not shown), a generator (not shown) for generating electric power by the rotational driving force of the steam turbine, a steam condenser 9 for condensing exhaust steam from the main engine and the steam turbine, and the like are provided.

A sea bay (first inboard storage section) 11 for storing seawater is provided at the lower part of the engine room 7. The sea bay 11 has a sealed tank structure, and is formed using, for example, a double bottom portion of the engine room 7.
The double bottom portion of the engine room 7 is connected to the sea bay 11 through a communication line 13 and is connected to a sea chest (not shown), which is a space communicating with the outside of the ship on the ship side, and the sea bay 11 through a communication line 15. And a sea chest (not shown) which is a space communicating with the outside of the ship.
The communication line 13 is opened and closed by an on-off valve 17, and the communication line 15 is opened and closed by an on-off valve 19.

  The regasification plant 1 is heated by a plurality of, for example, three propane loop heat exchangers (intermediate medium heat exchangers) 21 for heating the LNG taken out from the storage tank, and the propane loop heat exchanger 21. LNG supply for sequentially supplying LNG to a plurality of, for example, two open rack heat exchangers 23, a propane loop heat exchanger 21 and an open rack heat exchanger 23, for further heating and gasifying the generated LNG A system 25 and a seawater supply system (heating water supply system) 27 that supplies seawater to the propane loop heat exchanger 21 and the open rack heat exchanger 23 are provided.

The propane loop heat exchanger 21 uses a mixture of paraffinic hydrocarbons as an intermediate medium, for example, propane, and exchanges heat between LNG and seawater, and heats LNG with propane that conveys the amount of heat of seawater. Is.
In the propane loop heat exchanger 21, a heat transfer tube 29 through which LNG moves is installed in the upper part of the space in which propane is stored, and a heat transfer tube 31 through which seawater passes is installed in the lower part. Propane is heated and evaporated by seawater passing through the heat transfer tube 31. Since the evaporated propane has a small specific gravity, it moves upward. This propane is heat-exchanged with LNG passing through the heat transfer tube 29 to heat the LNG and to cool and condense itself. Condensed propane falls to the lower part and is heated again by seawater passing through the heat transfer tube 31 to evaporate. By repeating this, the propane loop heat exchanger 21 heats the LNG passing therethrough.

In this way, in the propane loop heat exchanger 21, since LNG is not in direct contact with propane in the middle, seawater is prevented from freezing even in the initial stage of heating LNG with a large temperature difference. be able to.
Propane has a higher specific gravity than air, so if it leaks, it will accumulate on the floor and cannot be installed in a closed space for safety reasons. For this reason, installing on the deck 5 which is the space which is not closed is liked.

  In the propane loop heat exchanger 21 of the present embodiment, a natural circulation method is used in which propane repeats evaporation (heat exchange with seawater) and condensation (heat exchange with LNG) in one space. Further, a forced circulation system in which propane is circulated through a pipe and evaporation and condensation are performed in different spaces may be employed.

The open rack heat exchanger 23 is provided with, for example, a box-shaped or pipe-shaped heat exchange section in which LNG flows. Seawater supplied by the seawater supply system 27 is flowed from the top to the bottom on the outer surface of the heat exchange section, and is heat-exchanged with the internal LNG. That is, LNG is heated by seawater and vaporized.
Since the open rack heat exchanger 23 does not need to have high corrosion resistance, it can be formed of, for example, an aluminum alloy material that is less expensive than titanium.

There is no problem even if the open rack heat exchanger 23 is installed in a closed space. Further, as will be described later, since LNG heated by the propane loop heat exchanger 21 is heated and gasified, the size can be reduced. As a result, the open rack heat exchanger 23 is installed in a space below the deck 5.
Thus, since the propane loop heat exchanger 21 is installed on the deck 5 and the open rack heat exchanger 23 is installed in the space below the deck 5, the propane loop heat exchanger 21 and the open rack heat exchanger 23 are installed. Can be arranged with their positions aligned in the vertical direction. If it does in this way, since the plane area of the regasification plant 1 can be made small, the regasification plant 1 can be effectively installed in the LNG ship of the limited space.

The LNG supply system 25 is formed by a pipe 33 that connects the storage tank, the propane loop heat exchanger 21 and the open rack heat exchanger 23 in this order.
The piping for supplying LNG from the storage tank to the propane loop heat exchanger 21 in the LNG supply system 25 is provided with a plurality of pumps 35 for increasing the pressure of LNG.

The seawater supply system 27 includes an open rack seawater supply system (open rack heating water supply system) 37 that supplies seawater to the open rack heat exchanger 23, and propane heating seawater that supplies seawater to the propane loop heat exchanger 21. A supply system (a heating water supply system for heating the intermediate medium) 39 is provided.
The open rack seawater supply system 37 includes an open rack supply line 41 that supplies seawater from the sea bay 11 to the open rack heat exchanger 23, a water bath 43 that stores seawater flowing down from the open rack heat exchanger 23, and A return pipe 45 that sends the seawater of the water bath 43 downward, and a return duct 47 that sends the seawater from the return pipe 45 to the sea bay 11 via the communication line 49 are provided.

The engine room 7 side of the open rack supply line 41 has a function of supplying seawater as cooling water to a steam condenser 9 that condenses exhaust steam from the main engine and the steam turbine.
On the sea bay 11 side of the open rack supply line 41, a supply pump 51 for sucking and feeding seawater in the sea bay 11 is provided.
On the downstream side of the steam condenser 9 of the open rack supply line 41, the open / close valve 53 opens and closes, and the open / close valve 57 opens and closes a communication line 55 connected to a sea chest (not shown) that is a space communicating with the outside of the ship. The branch line 59 connected to the sea bay 11 is branched.

An open / close valve 61 for opening and closing the open rack supply line 41 is provided on the upstream side of the open rack heat exchanger 23 of the open rack supply line 41.
The water bath 43 is provided with a communication line 65 that is opened and closed by an on-off valve 63 and connected to a sea chest (not shown) that is a space communicating with the outside of the ship.
The return pipe 45 is provided with an open / close valve 67 that opens and closes the return pipe 45.
The communication line 49 is provided with an open / close valve 69 that opens and closes the communication line 49.

  The propane heating seawater supply system 39 includes a tank (second inboard storage section) 71 for storing seawater, a propane heating supply line 73 for supplying seawater from the tank 71 to the propane loop heat exchanger 21, and propane loop heat. A gas vent tank 75 that stores seawater discharged from the exchanger 21 and a communication line 77 that sends the seawater in the gas vent tank 75 to the return duct 47 are provided.

A supply pump 79 is provided on the tank 71 side of the propane heating supply line 73 for sucking and feeding the seawater in the tank 71.
The gas vent tank 75 separates the gas component in the seawater and sends only the seawater to the downstream side. The gas vent tank 75 is provided with a communication line 83 that is opened and closed by an on-off valve 81 and connected to a sea chest (not shown) that is a space communicating with the outside of the ship.
The communication line 77 is provided with an open / close valve 85 that opens and closes the communication line 77.

The tank 71 is provided with a communication line 89 that is opened and closed by an on-off valve 87 and connected to a sea chest (not shown) that is a space communicating with the outside of the ship.
Further, the tank 71 is provided with a connection line 91 connected to the water bath 43. The connection line 91 is provided with an on-off valve 93 that opens and closes the connection line 91. When the on-off valve 93 is opened, the water bath 43 is installed above the tank 71, so that the sea water in the water bath 43 flows into the tank 71.

  A connection line 95 that connects the tank 71 to a position between the on-off valve 61 and the open rack heat exchanger 23 in the open rack supply line 41 is provided. On the tank 71 side of the connection line 95, a supply pump 97 for sucking and feeding the seawater in the tank 71 is provided.

Operation | movement of the regasification plant 1 concerning this embodiment demonstrated above is demonstrated.
First, the case where the LNG ship 3 unloads in a sea area where strict discharge regulations such as complete prohibition of seawater entry / exit are implemented will be described with reference to FIGS. 1 and 2. FIG. 2 is a block diagram showing the seawater supply state of the seawater supply system 27 at this time.
In FIG. 1, a line through which seawater flows is indicated by a thick line, a line that does not normally flow is indicated by a thin line, a line through which LNG flows is indicated by a two-dot broken line, and a line through which seawater that may contain gas is indicated by a one-dot broken line (thick line) ). Moreover, in FIG. 2, the line through which seawater flows is indicated by a solid line, and the line that does not flow is indicated by a broken line.

In this case, the on-off valves 17, 19, 63, 81, 87 are closed, the communication lines 13, 15, 65, 83, 89 are closed, and the communication between the inside of the ship and the outside of the ship is cut off. This makes it impossible to take in seawater from the outside of the ship and discharge seawater from the inside of the ship.
The on-off valve 61 is opened and the open rack supply line 41 is opened. The on-off valve 93 is opened, the connection line 91 is opened, and seawater flows from the water bath 43 to the tank 71.
A natural gas (NG) outlet (not shown) of the open rack heat exchanger 23 is connected to a city gas supply line (not shown) on the land side.

First, the operation of the seawater supply system 27 will be described.
Seawater stored in the sea bay 11 is pumped out by the supply pump 51 and is sent to the open rack heat exchanger 23 through the open rack supply line 41.
At this time, the seawater passing through the open rack supply line 41 passes through the steam condenser 9 and performs heat exchange with the exhaust heat of the exhaust steam from the main engine and the steam turbine, thereby cooling and condensing the exhaust steam. The temperature is raised by steam. Thus, since the temperature of the seawater supplied to the open rack type heat exchanger 23 is raised, the heating efficiency of LNG in the open rack type heat exchanger 23 can be improved. Further, even if the seawater in the sea bay 11 is cold in a cold sea area or the like, stable gasification can be performed by the open rack heat exchanger 23.

In the open rack heat exchanger 23, seawater supplied by the open rack supply line 41 is flowed from the top to the bottom on the outer surface of the heat exchange part, and is heat-exchanged with LNG passing through the inside of the heat exchange part. . That is, LNG is heated by seawater and vaporized. The gasified natural gas is supplied to a city gas pipe (not shown) on the land side.
Thus, since the seawater supplied to the open rack heat exchanger 23 is only flowed from the top to the bottom on the outer surface of the heat exchange section, it is in a substantially atmospheric pressure state. Therefore, the seawater passing through the open rack supply line 41 does not need to have a high supply pressure, and therefore does not need to be a high pressure resistant pipe. For this reason, since the piping of the open rack supply line 41 can be comprised with a comparatively cheap material, manufacturing cost can be reduced.

Seawater flowing down from the open rack heat exchanger 23 is stored in the water bath 43. The seawater stored in the water bath 43 is sent to the tank 71 through the connection line 91 and taken over by the propane heating seawater supply system 39.
The seawater stored in the tank 71 is pumped out by the supply pump 79 and sent to the propane loop heat exchanger 21 through the propane heating supply line 73.
Seawater introduced into the propane loop heat exchanger 21 passes through the heat transfer tube 31 to heat and evaporate propane. The evaporated propane rises and heats the LNG passing through the heat transfer tube 29.

Seawater cooled by propane in the propane loop heat exchanger 21 is collected in the gas vent tank 75. The seawater from which the gas component has been separated in the gas vent tank 75 is returned to the sea bay 11 via the communication line 77, the return duct 47 and the communication line 49.
Thus, since the seawater used in the open rack supply line 41 is continuously used in the propane heating seawater supply system 39, the amount of heat recovered by the steam condenser 9 can be utilized in the propane heating seawater supply system 39. .

  In the seawater supply system 27, seawater is continuously supplied to the open rack heat exchanger 23 and the propane loop heat exchanger 21, but the seawater is once returned to substantially atmospheric pressure by the open rack heat exchanger 23. The propane heating seawater supply system 39 for supplying seawater to the propane loop heat exchanger 21 only needs to supply, for example, an amount of seawater that covers about half of the heating amount for gasifying LNG. The supply pressure of 73 can be reduced. Accordingly, the power of the supply pump 79 can be reduced, so that the supply pump 79 can be reduced in size and fuel for driving can be saved.

On the other hand, in the LNG supply system 25, a plurality of pumps 35 are driven. When the pump 35 is driven, the LNG in the storage tank is taken out and boosted to a high pressure state of about 10 MPa (100 bar), for example.
The boosted LNG is supplied to the propane loop heat exchanger 21 through the pipe 33, preheated, and then sent to the open rack heat exchanger 23 through the pipe 33.
The LNG sent to the open rack heat exchanger 23 is heated and gasified by the seawater supplied from the open rack supply line 41 while passing through the heat exchange section of the open rack heat exchanger 23. The gasified natural gas (NG) is supplied from a natural gas (NG) outlet (not shown) of the open rack heat exchanger 23 to a city gas supply line (not shown) on the land side.

At this time, since the LNG introduced into the open rack heat exchanger 23 is preheated and heated by the propane loop heat exchanger 21, the temperature difference from seawater is small.
Therefore, even if the open rack heat exchanger 23 is shaken with the LNG ship 3 swaying and the seawater is intermittently separated from the outer surface of the heat exchanging portion, Since the magnitude of the thermal stress generated between the part that is cooled and the part that is not cooled due to the amount of light and shade can be suppressed, the open rack heat exchanger 23 may be damaged by this thermal stress. Can be suppressed.

  In this way, since LNG performs initial heating with severe conditions in the propane loop heat exchanger 21, it is possible to safely use an open rack heat exchanger 23 that is inexpensive and highly reliable for subsequent heating. In combination with the cost reduction of the seawater supply system 27, the regasification plant 1 can be manufactured at low cost. Further, since the open rack heat exchanger 23 is only used for the subsequent heating, it can be made relatively small and can be installed in a limited space of the LNG ship.

  In this way, the seawater supply system 27 uses seawater stored in the sea bay 11 and is a so-called closed loop in which seawater is neither discharged out of the ship nor taken in from the outboard, so strict discharge regulations are implemented. Regasification using seawater can be carried out even at the place where it is located.

Next, the case where the LNG ship 3 unloads in a sea area where strict seawater discharge regulations are not implemented will be described with reference to FIGS.
3 to 6 are block diagrams illustrating an example of an open loop system that circulates seawater in an outboard sea area, and illustrating a seawater supply state of the seawater supply system 27.
3 to 6, as in FIG. 2, a line through which seawater flows is indicated by a solid line, and a line that does not flow is indicated by a broken line.

In FIG. 3, an open rack seawater supply system 37 and a propane heating seawater supply system 39 are separated, the open rack seawater supply system 37 is a closed loop system, and the propane heating seawater supply system 39 is an open loop system. Is.
In this state, the open / close valves 81 and 87 are opened to open the communication lines 83 and 89 from the state shown in FIG. As a result, seawater in the sea area outside the ship is taken into the tank 71 through the communication line 89 and the seawater in the gas vent tank 75 is discharged out of the ship through the communication line 83.
Moreover, the on-off valve 93 is closed and the connection line 91 is closed. As a result, the seawater in the water bath 43 is not supplied to the tank 71. The seawater in the water bath 43 opens the on-off valve 67, opens the return pipe 45, and supplies seawater from the water bath 43 to the return duct 47.

In the propane heating seawater supply system 39, seawater outside the ship is introduced into the tank 71 from the communication line 89, and the seawater supplied to the propane loop heat exchanger 21 through the propane heating supply line 73 is supplied with an on-off valve. Since 85 is closed and the communication line 77 is closed, it is not supplied to the return duct 47 and discharged from the gas vent tank 75 through the communication line 83 to the outside of the ship.
On the other hand, in the open rack seawater supply system 37, the seawater supplied from the sea bay 11 through the open rack supply line 41 to the open rack heat exchanger 23 passes from the water bath 43 through the return pipe 45 and the return duct 47 to the sea bay. 11 is returned.
That is, the propane heating seawater supply system 39 is an open loop system, and the open rack seawater supply system 37 is a closed loop system.

Since the propane loop heat exchanger 21 does not cause a problem even when the seawater is cold, it can be used even in a cold sea area.
As described above, the operation in the open loop method can be performed even in a cold sea area, but the operation range of the efficient open loop method can be expanded, and the fuel efficiency can be improved accordingly.

In FIG. 4, the open rack seawater supply system 37 and the propane heating seawater supply system 39 are separated, and the open rack seawater supply system 37 and the propane heating seawater supply system 39 are in an open loop system.
In this state, the open / close valves 17, 19, 63 are opened to open the communication lines 13, 15, 65 from the state shown in FIG. Thereby, seawater in the sea area outside the ship is taken into the sea bay 11 through the communication lines 13 and 15, and seawater in the water bath 43 is discharged out of the ship through the communication line 65.
The on-off valves 67 and 69 are closed, and the return pipe 45 and the return duct 47 are closed. Thereby, the seawater of the water bath 43 is not supplied to the sea bay 11.

In this manner, the propane heating seawater supply system 39 operates in the same manner as that in FIG. 3, while the open rack seawater supply system 37 introduces seawater outside the ship from the communication lines 13 and 15 to the sea bay 11. After it circulates through the open rack supply line 41, the seawater is discharged from the water bath 43 through the communication line 65 to the outside of the ship.
That is, the propane heating seawater supply system 39 and the open rack seawater supply system 37 are both open loop.
This can expand the operating range of the efficient open loop method when the seawater temperature is higher than in the case of FIG. 3, and improve the fuel efficiency accordingly.

In FIG. 5, the open rack seawater supply system 37 and the propane heating seawater supply system 39 are separated, and the open rack seawater supply system 37 and the propane heating seawater supply system 39 are in an open loop system. The supply source of seawater supplied to the open rack heat exchanger 23 by the seawater supply system 37 is changed from the sea bay 11 to the outboard sea area.
In this state, from the state shown in FIG. 4, the on-off valve 53 is opened to open the communication line 55, and the on-off valve 61 is closed. Thereby, the seawater supplied from the sea bay 11 is not sent to the open rack heat exchanger 23 but is discharged out of the ship through the communication line 55.
Further, the supply pump 97 is operated so that the seawater in the tank 71 is supplied to the open rack heat exchanger 23 through the connection line 95.

In this way, the propane heating seawater supply system 39 operates in the same manner as in FIG. 3, while in the open rack seawater supply system 37, the open rack heat exchanger 23 is heated by the steam condenser 9. The seawater in the outboard sea area introduced into the tank 71 is supplied without being supplied.
That is, the propane heating seawater supply system 39 and the open rack seawater supply system 37 are both open loop systems, and seawater in the outboard sea area is directly supplied to the open rack heat exchanger 23.
This can be effectively utilized when the seawater temperature is higher than in the case of FIG.

In FIG. 6, the open rack seawater supply system 37 and the propane heating seawater supply system 39 are separated, the open rack seawater supply system 37 is an open loop system, and the propane heating seawater supply system 39 is a closed loop system. It is a thing.
In this state, from the state shown in FIG. 4, the on-off valves 93, 85, 69 are opened to open the communication lines 91, 77, 49. Thereby, a part of the seawater flows from the water bath 43 to the tank 71 through the communication line 91, and the rest of the sea water is discharged from the water bath 43 to the outside of the ship through the communication line 65. Further, the seawater in the gas vent tank 75 is returned to the sea bay 11 through the seawater return duct 47 and the communication line 49 through the communication line 77.
Moreover, the on-off valves 87 and 81 are closed, and the connection lines 89 and 83 are closed. Thereby, the communication between the tank 71 and the outside of the ship is cut off, and the communication between the gas vent tank 75 and the outside of the ship is cut off. As a result, seawater from outside the ship cannot be taken into the tank 71, and seawater in the gas vent tank 75 cannot be discharged out of the ship.

In this manner, the propane heating seawater supply system 39 operates in the same manner as that of FIG. 2, and in the open rack seawater supply system 37, a part of the seawater supplied from the water bath 43 is supplied to the tank 71. Seawater in the gas vent tank 75 is returned to the sea bay 11 via the seawater return duct 47 and the communication line 49, which circulates through the open rack supply line 41, and the remaining seawater is discharged from the communication line 65 to the outside of the ship. 4 is different from that of FIG. 4 in other respects, and the other operations are the same as those in FIG.
That is, the open rack seawater supply system 37 is an open loop system, and the propane heating seawater supply system 39 is a closed loop system.
This can be effectively utilized when the temperature of the seawater is higher than in the case of FIG. 3, and has the same effect as in the case of FIG.

  As described above, it is possible to select a so-called closed loop method and an efficient open loop method in which seawater is not discharged to the outside according to the situation of the place. As for the open loop system, an optimum one can be selected according to the temperature of seawater.

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, although this embodiment is applied to the regasification plant 1 mounted on the LNG ship 3, it may be installed in a floating or fixed offshore structure.

1 Regasification plant 3 LNG ship 7 Engine room 11 Sea bay (first inboard storage part)
21 Propane loop heat exchanger (intermediate medium type heat exchanger)
23 Open rack heat exchanger 27 Seawater supply system (heating water supply system)
37 Open rack seawater supply system (open rack heating water supply system)
39 Seawater supply system for propane heating (heating water supply system for intermediate medium heating)
71 Tank (Second inboard storage)

Claims (4)

An intermediate medium heat exchanger for preheating the liquefied gas with an intermediate medium heated with heated water;
An open rack heat exchanger that heats and gasifies the liquefied gas by applying heated water to the liquefied gas preheated by the intermediate medium heat exchanger;
A regasification plant for a floating structure characterized by comprising a heating water supply system for supplying heating water to the intermediate medium heat exchanger and the open rack heat exchanger. In the heating water supply system, a first ship storage section or a public water area can be selected as the heating water supply source, and heating water is circulated and supplied to the open rack heat exchanger and the open rack heat exchanger. An open rack heating water supply system capable of selectively discharging the heating water from the outside of the ship,
A second ship storage or public water area can be selected as a heating water supply source. The heating water is circulated and supplied to the intermediate medium heat exchanger and the heating water from the intermediate medium heat exchanger is selectively supplied. The regasification plant for a floating structure according to claim 1, further comprising a heating water supply system for heating an intermediate medium that can be discharged out of the ship.   The floating structure according to claim 2, wherein in the open rack heating water supply system, the heating water supplied to the open rack heat exchanger is heated by using exhaust heat of an engine room. Regasification plant for things. The second ship storage part of the heating water supply system for heating the intermediate medium is configured to selectively receive the heating water from the open rack heat exchanger in the open rack heating water supply system. The regasification plant for a floating structure according to claim 2 or 3, characterized by the above-mentioned.

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