Liquefied natural gas vaporizer and vaporizer method

Abstract

The present invention has a first open rack vaporizer and a second open rack vaporizer that each comprise: a heat exchange panel that is formed by aligning a plurality of heat transfer tubes; and a trough that supplies a heat medium such that the heat medium flows down either surface of the heat exchange panel. When liquified natural gas is to be vaporized, the liquified natural gas is supplied in parallel to the heat exchange panel of the first open rack vaporizer and the heat exchange panel of the second open rack vaporizer, and the heat medium is supplied to the trough of the first open rack vaporizer. Then, at least a portion of the heat medium used in the vaporization of the liquified natural gas at the heat exchange panel of the first open rack vaporizer is recovered and supplied to the trough of the second open rack vaporizer.

Description

[Technical field]

[0001] The present invention relates to a technique for vaporizing liquefied natural gas. This application claims priority to PCT / JP2021 / 12786, filed on March 26, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] Natural gas produced at the wellhead of a gas field is cooled and liquefied, and stored in storage tanks as liquefied natural gas (LNG). Therefore, in order to supply gas to consumers, the LNG needs to be re-gasified. As a device for vaporizing LNG discharged from an LNG tank, an LNG vaporizer equipped with an open rack type vaporizer that vaporizes LNG using seawater is known (for example, Patent Document 1). The open rack type vaporizer is configured such that a large number of heat transfer tubes through which LNG passes are arranged in a panel shape, and a heat medium is supplied along the outer surface of the heat exchange panel. The LNG is heated and vaporized by heat exchange between the LNG and the heat medium via the heat exchange panel.

[0003] In such an open rack type vaporizer, a large amount of heat medium is required for heat exchange with the LNG, which may require large-scale facilities such as a seawater supply system, etc. Therefore, the reduction of the initial cost and operating cost of the facility is an issue for the open rack type vaporizer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Application No. 2009-52724 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a method for vaporizing liquefied natural gas by heat exchange with a heat medium, comprising the steps of: Provides a technology for reducing the amount of heat transfer medium used. [Means for solving the problem]

[0006] The liquefied natural gas vaporizer of the present invention comprises: a first open rack type vaporizer and a second open rack type vaporizer each including a heat exchange panel arranged in a radial direction of a plurality of heat transfer tubes to which liquefied natural gas is supplied, the heat exchange panel being arranged so as to extend in a vertical direction, and a trough for supplying a heat medium so as to flow down along both sides of the heat exchange panel in order to vaporize the liquefied natural gas supplied to the heat transfer tube; a liquefied natural gas supply unit that supplies liquefied natural gas to the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer in parallel; a first heat medium supplying unit that supplies the heat medium to a trough of the first open rack-type vaporizer; and a second heat medium supply unit that recovers at least a portion of the heat medium after it has been used in the vaporization of the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer and supplies it to a trough of the second open rack type vaporizer.

[0007] The vaporizer may have the following features: (a) The heat medium is seawater. (b) the heat medium is an antifreeze liquid, and the antifreeze liquid has a freezing point that is lower than the temperature after it is used to vaporize the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer. (c) The first open rack type vaporizer is provided below the heat exchange panel and has a receiving tank section that receives the heat medium that flows down along the heat exchange panel, and the second heat medium supply section supplies the heat medium in the receiving tank section to a trough of the second open rack type vaporizer. (d) a heat exchange panel of the second open rack type vaporizer is arranged below the heat exchange panel of the first open rack type vaporizer, and the second heat medium supply section is composed of a guide plate that guides the heat medium that flows down along the heat exchange panel of the first open rack type vaporizer to a trough of the second open rack type vaporizer. (e) An extraction header section, which is a common piping for extracting vaporized natural gas and is connected to the plurality of heat transfer tubes, is provided at the upper end of the heat exchange panel of the second open rack type vaporizer, and the guide plate is provided so as to cover the extraction header section. (f) the first heat medium supply unit is configured to freely switch the supply destination of the heat medium between a trough of the first open rack type vaporizer and a trough of the second open rack type vaporizer, and the supply of the heat medium from the second heat medium supply unit is stopped during a period in which the heat medium is supplied from the first heat medium supply unit to the trough of the second open rack type vaporizer. (g) The liquefied natural gas supply unit adjusts the supply flow rate of liquefied natural gas to the first open rack type vaporizer so that the supply flow rate of liquefied natural gas to the second open rack type vaporizer is at least twice as high as the supply flow rate of liquefied natural gas to the second open rack type vaporizer. (h) further comprising a branch passage for recovering a portion of the heat medium after it has been used in the vaporization of the liquefied natural gas in the heat exchange panel of the first open rack-type vaporizer. (i) The branch flow path returns at least a portion of the recovered heat medium to the first heat medium supply section.

[0008] The method for vaporizing liquefied natural gas of the present invention includes the steps of: a step of supplying liquefied natural gas in parallel to the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer using a first open rack type vaporizer and a second open rack type vaporizer, each of which includes a heat exchange panel arranged in a radial direction of a plurality of heat transfer tubes arranged so as to extend in a vertical direction and to which liquefied natural gas is supplied, and a trough for supplying a heat medium so as to flow down along both sides of the heat exchange panel in order to vaporize the liquefied natural gas supplied to the heat transfer tube; The method includes the steps of: supplying the heat medium to a trough of the first open rack type vaporizer; recovering at least a portion of the heat medium after it has been used for vaporizing liquefied natural gas in a heat exchange panel of the first open rack type vaporizer; and supplying the recovered heat medium to a trough of the second open rack type vaporizer. Effect of the Invention

[0009] The liquefied natural gas vaporization device of the present invention recovers the heat transfer medium after it has been used to vaporize liquefied natural gas in the first open rack-type vaporizer and supplies it to the trough of the second open rack-type vaporizer, thereby making it possible to reduce the amount of heat transfer medium supplied. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of an open rack vaporizer. [Diagram 2] FIG. 2 is a side view of an open rack vaporizer. [Diagram 3] FIG. 2 is a schematic diagram illustrating vaporization of LNG using an open rack-type vaporizer. [Figure 4] FIG. 1 is a configuration diagram showing a vaporization device according to a first embodiment. [Diagram 5] FIG. 11 is a configuration diagram showing a vaporization device according to a second embodiment. [Figure 6] FIG. 11 is a schematic diagram showing a flow of a heat medium in an evaporation device according to a second embodiment. [Figure 7] FIG. 11 is a configuration diagram showing another example of the vaporizer according to the second embodiment. [Figure 8] FIG. 11 is a configuration diagram showing another example of the vaporizer according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First, the configuration of an open rack type vaporizer according to each embodiment described later will be described. The open rack type vaporizer of this example uses seawater pumped from the ocean as a heat medium, for example, and vaporizes LNG by heat exchange between the seawater and LNG by raising the temperature of the LNG. As shown in Figs. 1 and 2, the open rack type vaporizer 1 is supplied with LNG and includes a heat exchange panel 10 configured by arranging a plurality of heat transfer tubes 11 arranged so as to extend vertically in the tube diameter direction. For convenience of illustration, in Fig. 1, each heat exchange panel 10 is simply represented as a plate, omitting the illustration of each individual heat transfer tube 11.

[0012] The open rack vaporizer 1 is provided with a plurality of heat exchange panels 10. These heat exchange panels 10 are arranged in a line along the thickness direction, with gaps between them. A supply header section 2 for supplying LNG is provided at the lower end of the heat transfer tubes 11 of each heat exchange panel 10. The supply header section 2 is formed of piping provided along the lower end of each heat exchange panel 10, and includes a plurality of branch pipes 12 to which the lower end of each heat transfer tube 11 is connected to the pipe wall, and a common manifold 13 connected to the upstream end of these branch pipes 12. An LNG supply pipe 14 is connected to the manifold 13, and LNG supplied from this LNG supply pipe 14 is distributed to the heat transfer tubes 11 of each heat exchange panel 10 via the manifold 13 and the branch pipes 12.

[0013] An aluminum extraction header 3 for extracting vaporized NG is provided at the upper end of the heat transfer tubes 11 of each heat exchange panel 10. The extraction header 3 is composed of piping provided along the upper end of each heat exchange panel 10, and includes a plurality of branch pipes 15, the upper ends of which are connected to the pipe walls of the extraction header 3, and a common manifold 16 connected to the downstream ends of the branch pipes 15. An LNG extraction pipe 17 is connected to the manifold 16, and the NG flowing out of the heat transfer tubes 11 of each heat exchange panel 10 merges with the LNG extraction pipe 17 via the extraction header 3.

[0014] Further, a trough 18 is provided on the upper side of the heat exchange panel 10 for temporarily storing seawater, which is a heat medium. The trough 18 is open at the top and formed in a gutter shape extending in the arrangement direction of the heat transfer tubes 11. When viewed along the arrangement direction of the multiple heat exchange panels 10, the troughs 18 are arranged alternately with these heat exchange panels 10. That is, when viewed from each heat exchange panel 10, the troughs 18 are provided on both sides of the upper side thereof.

[0015] According to the above-mentioned configuration, the side surface of the heat exchange panel 10 and the side wall surface of the trough 18 are arranged to face each other. A gap is formed between the side surface of the heat exchange panel 10 and the side wall surface of the trough 18 arranged to face each other, allowing seawater flowing out from the trough 18 to flow down. When viewed along the arrangement direction of the heat exchange panels 10, the troughs 18 arranged at both ends have the upper end positions of the side walls that do not face the side surface of the heat exchange panel 10 higher so that seawater does not spill toward the surface on which the heat exchange panel 10 is not arranged.

[0016] A seawater supply header 4 (hereinafter also referred to as a heat medium supply header) for supplying seawater is connected to each trough 18. The seawater supply header 4 includes a plurality of distribution pipes 19, the downstream ends of which are connected to the bottoms of the respective troughs 18, and a common manifold 20 connected to the upstream ends of the distribution pipes 19. A supply pipe 22 is connected to the manifold 20, and seawater supplied from the supply pipe 22 is distributed to each trough 18 via the manifold 20 and the distribution pipe 19. On the other hand, a pool 21, which is a common receiving tank provided along the arrangement direction of the plurality of heat exchange panels 10, is provided below the heat exchange panel 10. A drain pipe 26 for draining seawater accumulated in the pool 21 is connected to the pool 21.

[0017] For the open rack-type vaporizer 1 having the above-mentioned configuration, LNG at, for example, -160°C is supplied from the lower end side of the heat transfer tubes 11 constituting each heat exchange panel 10 through the branch pipes 12 of the supply header section 2 (FIG. 3). The LNG supplied to the heat transfer tubes 11 enters the lower side of the heat transfer tubes 11. On the other hand, seawater at, for example, 20°C is supplied to the trough 18. The seawater supplied to the trough 18 overflows from the open upper surface of the trough 18 and flows into the gap between the trough 18 and the heat exchange panel 10. The seawater that has flowed into the gap flows down along the heat exchange panel 10 and into the pool 21 provided below the heat exchange panel 10. As described above, the troughs 18 are provided on both sides of the upper part of the heat exchange panel 10, so that the seawater flows along both sides of the heat exchange panel 10.

[0018] In this heat exchange panel 10, heat exchange takes place between seawater (20°C) flowing down both sides of the heat exchange panel 10 and LNG (-160°C) supplied to the lower side of the heat exchange panel 10. As a result, the LNG is warmed by the seawater and vaporizes, becoming NG that rises inside each heat transfer tube 11. Meanwhile, the seawater is cooled by the LNG, lowering in temperature, and falls into the pool 21. The vaporized NG is taken out from the upper end side of the heat transfer tube 11 via the extraction header section 3. The seawater, whose temperature has been lowered after heat exchange, is collected in the pool 21 and discharged to the outside.

[0019] Generally, the open rack-type vaporizer 1 consumes a large amount of seawater to vaporize LNG at -160°C using the sensible heat of seawater, which is a heat medium. Therefore, in LNG vaporization equipment using the open rack-type vaporizer 1, the equipment for taking in seawater and supplying it to the open rack-type vaporizer 1 and the auxiliary equipment for sterilizing the seawater tend to be large. This causes problems with the initial cost and operating cost of the equipment, and reducing these costs is an issue.

[0020] On the other hand, since the temperature of seawater after being used as a heat medium is reduced, there may be a lower limit on the temperature when the seawater used in the open rack type vaporizer 1 is discharged back into the sea. For this reason, the flow rate of seawater supplied to the open rack type vaporizer 1 to ensure the amount of heat required for vaporizing LNG becomes larger than when the sensible heat of the seawater is fully utilized and the discharge temperature of the seawater is further lowered. On the other hand, since a large amount of energy is consumed when cooling and liquefying LNG, various methods are being considered, such as using this LNG for various cooling purposes prior to vaporization and effectively utilizing the low-temperature seawater discharged from the vaporizer.

[0021] In consideration of the problems described above, in the LNG vaporizers 100, 101, 102, and 103 according to the embodiments described below, the discharged seawater temperature is lowered than in the past. The lowered temperature seawater may be used in a cold energy utilization facility as described below, or may be temporarily stored in a seawater tank and discharged into the sea after it has reached a temperature similar to that of the environment. As a result, it is possible to fully utilize the sensible heat of the seawater, and the configuration makes it possible to reduce the amount of seawater used. Hereinafter, LNG vaporizers 100, 101, 102, and 103 according to the respective embodiments will be described with reference to FIGS.

[0022] 4 shows a vaporizer 100 according to a first embodiment. This vaporizer 100 includes two open rack-type vaporizers 1 described above. Hereinafter, the two open rack-type vaporizers 1 will be referred to as a first open rack-type vaporizer (first vaporizer) 1A and a second open rack-type vaporizer (second vaporizer) 1B, respectively. In addition, the first vaporizer 1A and the second vaporizer 1B are each given additional identification symbols A and B to distinguish them from one another.

[0023] In the vaporization device 100 according to the first embodiment, for example, LNG stored in an LNG tank is supplied in parallel to the heat exchange panels 10A and 10B of the first vaporizer 1A and the second vaporizer 1B via the LNG supply pipe 14. The LNG supply pipe 14 is provided with a flow rate adjusting unit (not shown) configured to adjust the flow rate of the LNG supplied to the heat exchange panels 10A and 10B. The LNG supply pipe 14 and the supply headers 2A and 2B of the vaporizers 1A and 1B correspond to the liquefied natural gas supply unit in this example.

[0024] Furthermore, the seawater supply header 4A connected to the trough 18A of the first vaporizer 1A is provided with a supply pipe 22A for supplying seawater as a heat medium. In this embodiment, seawater is used as the heat medium. The heat medium is not limited to seawater and other media may be used. For example, seawater is taken from the ocean by a water intake facility (not shown) and sterilized by a seawater sterilization facility. The sterilized seawater is then supplied to the seawater supply header 4A by a pump 23A. The reference symbol 23A in FIG. 4 indicates a pump for supplying the seawater sterilized by the seawater sterilization facility to the height position where the trough 18A of the first vaporizer 1A is disposed.

[0025] On the other hand, in the vaporization device 100 of this example, the trough 18B of the second vaporizer 1B is configured to be supplied with seawater that has been used to vaporize LNG in the first vaporizer 1A, rather than with seawater immediately after it has been taken in by the water intake equipment. That is, the seawater used in the first vaporizer 1A is collected by the pool 21A and sent to the supply pipe 22B on the second vaporizer 1B side through the drain pipe 26A. This supply pipe 22B is connected to the seawater supply header 4B that supplies seawater to the trough 18B of the second vaporizer 1B. Here, the reference numeral 23B indicates a pump for supplying the seawater discharged through the drain pipe 26A to the height position where the trough 18B of the second vaporizer 1B is arranged. The seawater collected in the pool 21B of the second vaporizer 1B is supplied to a cold energy utilization facility that uses the seawater with a reduced temperature through the drain pipe 26B. The supply pipe 22A, the pump 23A, and the seawater supply header 4A correspond to the first heat medium supply unit of this example. The supply pipe 22B, the pump 23B, and the seawater supply header 4B correspond to the second heat medium supply unit of this example.

[0026] An example of heat balance in the vaporization device 100 will be described. For example, when LNG at a temperature of -160°C is vaporized at a flow rate of 40 tons / hour, LNG is supplied to the first vaporizer 1A at a flow rate of 28 tons / hour. In the first vaporizer 1A, the 28 tons / hour of LNG is heated by seawater at 20°C and taken out as NG at, for example, 0°C. The seawater that has undergone heat exchange flows down into the pool 21A after its temperature is lowered to, for example, 8°C.

[0027] Also, LNG is supplied to the second vaporizer 1B at a flow rate of 12 tons / hour. In the second vaporizer 1B, the 12 tons / hour LNG is heated by seawater at 8°C and taken out as NG at, for example, 0°C.

[0028] In this way, when the seawater used to heat LNG in first vaporizer 1A is reused to heat LNG in second vaporizer 1B, the temperature of the seawater flowing down into pool 21B on the second vaporizer 1B side drops to 2° C. Then, the seawater that has undergone heat exchange in second vaporizer 1B is collected in pool 21B and then supplied to a seawater cold energy utilization facility.

[0029] As shown in the calculation results in the embodiment described later, the first vaporizer 1A of this embodiment consumes 480 tons / hour of seawater to vaporize 28 tons / hour of NG (0°C) by using seawater with a supply temperature of 20°C and performing heat exchange so that the discharge temperature is 8°C. Next, the second vaporizer 1B uses seawater with a supply temperature of 8°C and a supply flow rate of 480 tons / hour and performs heat exchange so that the discharge temperature is 2°C, and can vaporize 12 tons / hour of NG (0°C). Therefore, with 480 tons / hour of seawater, the first vaporizer 1A and the second vaporizer 1B can vaporize a total of 40 tons / hour of NG.

[0030] As described above, the second vaporizer 1B uses seawater that has been used to vaporize LNG in the first vaporizer 1A as a heat medium, and therefore has less heat available for vaporizing LNG than the first vaporizer 1A. Therefore, the flow rate of LNG that can be vaporized in the second vaporizer 1B is smaller than the flow rate of LNG that can be vaporized in the first vaporizer 1A.

[0031] Therefore, the supply flow rate is adjusted from LNG supply pipe 14 constituting the liquefied natural gas supply section so that the supply flow rate of LNG to supply header section 2A of first vaporizer 1A is 1.5 times or more, preferably within a range of 2 to 4 times, the supply flow rate of LNG to supply header section 2B of second vaporizer 1B. An example of the adjustment of the supply flow rate can be a case where it is performed using a flow control valve (not shown) provided on the inlet side of each of supply header sections 2A and 2B.

[0032] On the other hand, as shown in the calculation results in the comparative example described later, when one open rack type vaporizer is used, 720 tons / hour of seawater is required to vaporize 40 tons / hour of NG (0°C). Thus, compared to the case where one open rack type vaporizer is used, the vaporization device 100 according to this embodiment can significantly reduce the amount of seawater consumed and obtain low-temperature seawater.

[0033] Furthermore, by reducing the amount of seawater used, it is possible to downsize equipment such as the seawater intake equipment, the seawater sterilization equipment, the main bodies of the pumps 23A and 23B, the power supply and distribution equipment that supplies their power, the meters for managing and monitoring the water supply, the piping and valves for supplying and discharging water, and to reduce the operating costs.

[0034] Moreover, the vaporizer 100 according to the present invention supplies cold seawater, the temperature of which has been reduced by use in vaporizing LNG, to a cold energy utilization facility. Examples of cold energy utilization include cooling the driving fluid of a turbine in temperature difference power generation, cooling steam in seawater desalination using the flash method, district cooling, cooling the air and soil in a plant factory, and cooling fish and shellfish culture water. For example, the lower the temperature of the cold energy source used in a temperature difference power generation facility, the better. In this regard, the vaporizer 100 according to the present embodiment is effective because it can obtain seawater with a lower temperature than before.

[0035] In addition, the heat medium used to vaporize LNG is not limited to seawater. For example, industrial water may be supplied as the heat medium to the first vaporizer 1A and the second vaporizer 1B.

[0036] Furthermore, in the vaporizer 100 according to the first embodiment, the equipment may be installed so that the height position where the first vaporizer 1A is arranged is higher than the height position where the second vaporizer 1B is arranged. With this configuration, the height difference between the pool 21A on the first vaporizer 1A side and the second trough 18B on the second vaporizer 1B side becomes small, and the load on the pump 23B can be reduced.

[0037] Furthermore, the equipment may be installed so that the pool 21A of the first vaporizer 1A is located at a higher position than the trough 18B of the second vaporizer 1B. By configuring in this way, the seawater in the pool 21A of the first vaporizer 1A can be supplied to the trough 18B of the second vaporizer 1B by gravity. In this case, the installation of the pump 23B between the pool 21A of the first vaporizer 1A and the trough 18B of the second vaporizer 1B can be omitted.

[0038] [Second embodiment] Next, a second embodiment will be described. In the vaporizer 101 according to the second embodiment, a heat exchange panel 10B of a second vaporizer 1B is disposed below a heat exchange panel 10A of a first vaporizer 1A as shown in Figs. 5 and 6.

[0039] The seawater as a heat medium supplied to the first vaporizer 1A and flowing down along both sides of the heat exchange panel 10A flows down below the heat exchange panel 10A and then flows into the trough 18B of the second vaporizer 1B. In this embodiment, seawater is used as the heat medium. The heat medium is not limited to seawater and other heat media may be used. Furthermore, in this example, a guide plate 25 is provided to guide the seawater toward the trough 18B. This guide plate 25 may have a function to prevent the seawater flowing down from the heat exchange panel 10A from contacting the take-out header section 3. In this case, the guide plate 25 is provided for each heat exchange panel 10B, is configured in a roof shape extending along the branch pipe 12B, and is provided so as to cover the branch pipe 12B of the take-out header section 3. The seawater that has flowed through the heat exchange panel 10A flows through the guide plate 25 and into the trough 18B of the second vaporizer 1B. Therefore, in the second embodiment, the guide plate 25 corresponds to a second heat medium supply section.

[0040] In the vaporizer 101 having the above-mentioned configuration, the seawater that flows along the heat exchange panel 10A of the first vaporizer 1A flows into the trough 18 of the second vaporizer 1B. Therefore, compared with the vaporizer 100 according to the first embodiment described with reference to FIG. 4, the supply pipe 22B, the seawater supply header 4B, and the pump 23B that supply the seawater in the pool 21A that receives the seawater that has flowed down the heat exchange panel 10A of the first vaporizer 1A to the trough 18B of the second vaporizer 1B can be omitted. Furthermore, by providing the guide plate 25 in the second embodiment, the seawater that has flowed down the heat exchange panel 10A can be prevented from falling on the take-out header 3B, and deterioration of the take-out header 3B can be suppressed.

[0041] Moreover, vaporizer 102 shown in Fig. 7 shows another configuration example of vaporizer 101 according to the second embodiment described with reference to Figs. 5 and 6. In this vaporizer 102, a seawater supply header 4C is provided for supplying seawater to each trough 18B of second vaporizer 1B, and supply piping 22A for supplying seawater is branched and connected to seawater supply header 4C. Moreover, the supply destination of seawater from supply piping 22A can be freely switched between seawater supply header 4A on the first vaporizer 1A side and seawater supply header 4C on the second vaporizer 1B side by an opening / closing valve (not shown).

[0042] According to the vaporizer 102 having the above-mentioned configuration, the supply destination of seawater can be switched between the trough 18A of the first vaporizer 1A and the trough 18B of the second vaporizer 1B as necessary. According to this configuration, under normal circumstances, seawater is supplied to the trough 18A of the first vaporizer 1A, and LNG is vaporized using the two vaporizers 1A and 1B in the same manner as in the example described with reference to Figs. 5 and 6. On the other hand, when the supply flow rate of LNG is low, the supply of LNG to the first vaporizer 1A on the upper stage side is stopped, and seawater is supplied to the trough 18B on the second vaporizer 1B side, and LNG is vaporized using only the second vaporizer 1B on the lower stage.

[0043] The configuration in which the supply destination of seawater from the supply pipe 22A can be freely switched between the first vaporizer 1A and the second vaporizer 1B is not limited to the case of application to the vaporizer 102 in which the vaporizers 1A and 1B are arranged vertically as shown in FIG. 7. The vaporizer 100 shown in FIG. 4 may also be configured to be capable of freely switching the supply destination of seawater from the supply pipe 22A between the seawater supply header 4A of the first vaporizer 1A and the seawater supply header 4B of the second vaporizer 1B. In this case, the supply of LNG to the first vaporizer 1A is stopped, and seawater is supplied to the trough 18B on the second vaporizer 1B side, and LNG can be vaporized using only the lower second vaporizer 1B.

[0044] As described above, in the vaporizers 101 and 102 of the embodiments described with reference to Figs. 5 to 7, similarly to the vaporizer 100 according to the first embodiment described with reference to Fig. 4, it is possible to reduce the amount of seawater used, to miniaturize additional equipment such as seawater intake equipment, and to reduce operating costs. In addition, since it is possible to obtain seawater at a lower temperature than in a conventional LNG vaporizer, it is also advantageous in supplying cold energy to various cold energy utilization facilities. In addition, similarly to the vaporizer 100 according to the first embodiment, it is also possible to vaporize LNG using industrial water instead of seawater.

[0045] In order to verify the effect of the vaporizer according to the embodiment of the present invention, a simulation was performed to determine the required seawater supply flow rate and the temperature of the seawater discharged as wastewater when vaporizing LNG using vaporizer 100 shown in Fig. 4. In addition, an example in which LNG was vaporized using only first vaporizer 1A was used as a comparative example, and the amount of seawater required when vaporizing was performed in the same manner and the temperature of the seawater discharged as wastewater were also determined by simulation.

[0046] In the examples and comparative examples, LNG was treated at -160°C with a supply flow rate of 40 tons / hour to obtain NG at 0°C. In the examples, 28 tons / hour of LNG was treated in the first vaporizer 1A and 12 tons / hour in the second vaporizer 1B. The seawater before heat exchange was at 20°C.

[0047] According to the simulation results of the example, when the temperature of the discharged seawater is 2°C, the seawater consumption for vaporizing LNG is about 480 tons / hour. On the other hand, according to the simulation results of the comparative example, about 720 tons / hour of seawater is required to vaporize LNG at the above-mentioned supply flow rate. Therefore, according to the vaporization device 100 of this embodiment, it is possible to suppress the consumption of seawater required for liquefying LNG and obtain low-temperature seawater suitable for supply to cold energy utilization equipment.

[0048] The heat medium may be not only seawater but also an antifreeze liquid. The antifreeze liquid may be, for example, an aqueous solution of propylene glycol, ethylene glycol, diethylene glycol, methyl alcohol, isopropanol, or the like. For example, in the case of propylene glycol, the concentration of the antifreeze liquid is adjusted to a range of about 30% to 90%. The freezing point of propylene glycol is -7°C to -50°C in this concentration range, which is lower than the freezing point of seawater (-1.8°C). Therefore, when an antifreeze liquid having a lower freezing point than seawater is used as the heat medium, the temperature of the antifreeze liquid after being circulated through the first vaporizer 1A and the second vaporizer 1B can be set to a lower temperature than seawater. Therefore, when an antifreeze liquid is used as the heat medium, the amount of antifreeze liquid required for vaporizing LNG can be reduced compared to when seawater is used as the heat medium, and cold energy can be supplied to a cold energy utilization facility at a lower temperature compared to when seawater is used as the heat medium.

[0049] [Third embodiment] 8, the vaporizer 103 may circulate a heat medium so that heat generated when vaporizing LNG can be utilized in a cold energy utilization facility. The vaporizer 103 includes a branch flow path 27 branched off from a flow path (drain pipe 26A) that connects the downstream side of the flow path of the heat medium of the first open rack type vaporizer (first vaporizer 1A) and the upstream side of the flow path of the heat medium of the second open rack type vaporizer (second vaporizer 1B). The heat medium is, for example, an antifreeze liquid having a lower freezing point than seawater. The antifreeze liquid has a freezing point equal to or lower than the temperature after being used for vaporizing LNG in the heat exchange panels of the first open rack type vaporizer and the second open rack type vaporizer. The flow rate of the heat medium is adjusted according to the flow rate of LNG flowing through the first vaporizer 1A and the second vaporizer 1B so as not to freeze on the surfaces of the first vaporizer 1A and the second vaporizer 1B. This allows the temperature of the heat medium after heat exchange in the first vaporizer 1A and the second vaporizer 1B to be lower than when seawater is used as the heat medium, and the flow rate of the heat medium flowing through the first vaporizer 1A and the second vaporizer 1B to be smaller than when seawater is used as the heat medium.

[0050] The branch flow path 27 recovers, for example, a heat medium Q obtained by dividing at least a part of the heat medium recovered in the pool 21A. The branch flow path 27 may be connected to, for example, a cold storage tank (not shown) that cools the ice slurry as a cold energy utilization facility as described later.

[0051] The branch flow path 27 may return the heat medium Q, which is at least a part of the heat medium recovered in the pool 21A, to the first heat medium supply section (the supply pipe 22A, the pump 23A, and the heat medium supply header section 4A). In this case, for example, a heat exchanger (not shown) for heating the heat medium may be provided between the branch flow path 27 and the first heat medium supply section. The heat exchanger may utilize heat discharged from a heat source such as a generator or an air conditioner. The heat medium heated by the heat exchanger is returned to the first heat medium supply section and used again for vaporizing LNG. In this case, a cold storage tank may be provided between the branch flow path 27 and the heat exchanger.

[0052] The drain pipe 26B may be connected to, for example, the above-mentioned cold storage tank (not shown) and may exchange heat with the heat medium P recovered in the pool 21B to cool the ice slurry. The drain pipe 26B may also return the heat medium P to the first heat medium supply unit (supply piping 22A, pump 23A, heat medium supply header unit 4A). In this case, the above-mentioned cold storage tank may be provided between the drain pipe 26B and the second heat medium supply unit.

[0053] According to the vaporizer 103 of the third embodiment, by using an antifreeze liquid as the heat medium, the temperature of the antifreeze liquid after vaporizing LNG can be set lower than when seawater is used as the heat medium, and the flow rate of the heat medium circulated through the first vaporizer 1A and the second vaporizer 1B can be reduced compared to when seawater is used as the heat medium. According to the vaporizer 103, cold energy can be supplied to the cold energy utilization facility at a lower temperature than when seawater is used as the heat medium. According to the vaporizer 103, the heat medium Q recovered through the branch flow path 27 from the drain pipe 26A connected to the pool 21A and the heat medium P recovered in the pool 21B can be used to exchange heat with the cold energy storage tank in which the ice slurry is stored, thereby cooling the ice slurry.

[0054] Although the present invention has been described above using the embodiments, the present invention is not limited to these embodiments, and various modifications and substitutions can be made without departing from the scope of the present invention. For example, in the first vaporizer 1A and the second vaporizer 1B, the LNG supply pipe 14, the manifold 13, and the branch pipe 12 may be installed in the upper part of the heat exchange panel 10, and the extraction header 3, the manifold 16, and the LNG extraction pipe 17 may be arranged in the lower part, so that LNG is supplied to flow down inside the heat exchange panel 10. [Explanation of symbols]

[0055] 1A, 1B First and second vaporizers 2 Supply Header Section 4 Seawater supply header (heat medium supply header) 10 Heat exchange panel 11 Heat transfer tube 18 Trough 27 Branching Channel 100, 101, 102, 103 Vaporizer

Claims

1. A liquefied natural gas vaporizer comprising: a first open rack type vaporizer and a second open rack type vaporizer each including a heat exchange panel arranged in a radial direction of a plurality of heat transfer tubes to which liquefied natural gas is supplied, the heat exchange panel being arranged so as to extend in a vertical direction, and a trough for supplying a heat medium so as to flow down along both sides of the heat exchange panel in order to vaporize the liquefied natural gas supplied to the heat transfer tube; a liquefied natural gas supply unit that supplies liquefied natural gas to the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer in parallel; a first heat medium supply unit that supplies the heat medium to a trough of the first open rack-type vaporizer; a second heat medium supply unit that recovers at least a portion of the heat medium after it has been used in the vaporization of the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer and supplies it to a trough of the second open rack type vaporizer.

2. 2. The liquefied natural gas vaporizer according to claim 1, wherein the heat medium is seawater.

3. The heat transfer medium is an antifreeze liquid, The liquefied natural gas vaporization device described in claim 1, characterized in that the antifreeze has a freezing point lower than the temperature after being used to vaporize the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer.

4. The liquefied natural gas vaporization device described in claim 1, characterized in that the first open rack type vaporizer is provided below the heat exchange panel and has a receiving tank section that receives the heat medium that flows down along the heat exchange panel, and the second heat medium supply section supplies the heat medium in the receiving tank section to a trough of the second open rack type vaporizer.

5. The liquefied natural gas vaporization device described in claim 1, characterized in that a heat exchange panel of the second open rack type vaporizer is arranged below the heat exchange panel of the first open rack type vaporizer, and the second heat medium supply section is composed of a guide plate that guides the heat medium that flows down along the heat exchange panel of the first open rack type vaporizer to the trough of the second open rack type vaporizer.

6. The liquefied natural gas vaporization device described in claim 5, characterized in that an extraction header section, which is a common piping for extracting vaporized natural gas and is connected to the multiple heat transfer tubes, is provided at the upper end of the heat exchange panel of the second open rack type vaporizer, and the guide plate is provided so as to cover the extraction header section.

7. The liquefied natural gas vaporization device according to claim 1, characterized in that the first heat medium supply unit is configured to freely switch the supply destination of the heat medium between the trough of the first open rack type vaporizer and the trough of the second open rack type vaporizer, and the supply of the heat medium from the second heat medium supply unit is stopped during a period in which the heat medium is supplied from the first heat medium supply unit to the trough of the second open rack type vaporizer.

8. The liquefied natural gas vaporization device described in claim 1, characterized in that the liquefied natural gas supply unit adjusts the supply flow rate of liquefied natural gas to the first open rack type vaporizer so that the supply flow rate of liquefied natural gas to the first open rack type vaporizer is at least twice the supply flow rate of liquefied natural gas to the second open rack type vaporizer.

9. The liquefied natural gas vaporization device according to claim 1, further comprising a branch passage for recovering a portion of the heat medium after it has been used in the vaporization of the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer.

10. The liquefied natural gas vaporizer according to claim 9 , wherein the branch passage returns at least a portion of the recovered heat medium to the first heat medium supply section.

11. 1. A method for vaporizing liquefied natural gas, comprising the steps of: a step of supplying liquefied natural gas in parallel to the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer using a first open rack type vaporizer and a second open rack type vaporizer, each of which includes a heat exchange panel arranged in a radial direction of a plurality of heat transfer tubes arranged so as to extend in a vertical direction and to which liquefied natural gas is supplied, and a trough for supplying a heat medium so as to flow down along both sides of the heat exchange panel in order to vaporize the liquefied natural gas supplied to the heat transfer tube; supplying the heat transfer medium to a trough of the first open rack-type vaporizer; recovering at least a portion of the heat medium after it has been used in the vaporization of the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer, and supplying the recovered heat medium to a trough of the second open rack type vaporizer.

12. 12. The method for vaporizing liquefied natural gas according to claim 11, wherein the heat medium is seawater.

13. The heat transfer medium is an antifreeze liquid, the antifreeze has a freezing point equal to or lower than a temperature after the antifreeze has been used to vaporize the liquefied natural gas in the heat exchange panel of the first open rack type vaporizer and the heat exchange panel of the second open rack type vaporizer; The method for vaporizing liquefied natural gas according to claim 11.

14. The liquefied natural gas vaporization method according to claim 11, characterized in that the recovery of the heat medium in the process of supplying the recovered heat medium to the second open rack type vaporizer is performed using a receiving tank section that is provided below the heat exchange panel of the first open rack type vaporizer and receives the heat medium that flows down along the heat exchange panel.

15. The method for vaporizing liquefied natural gas described in claim 11, characterized in that, when a heat exchange panel of the second open rack type vaporizer is installed below the heat exchange panel of the first open rack type vaporizer, the process of supplying the recovered heat medium to the second open rack type vaporizer is performed by guiding the heat medium that has flowed down along the heat exchange panel of the first open rack type vaporizer to a trough of the second open rack type vaporizer.

16. The method for vaporizing liquefied natural gas according to claim 11, characterized in that, in the process of supplying the liquefied natural gas, the supply flow rate of the liquefied natural gas to the first open rack type vaporizer is adjusted to be at least twice the supply flow rate of the liquefied natural gas to the second open rack type vaporizer.

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