Heat exchanger and heat exchanging system

Abstract

A heat exchanger (2) has: a low-temperature flow path (21) into which a low-temperature liquefied gas is introduced; and a liquefaction target flow path (22) into which gaseous carbon dioxide is introduced. The low-temperature flow path (21) has: a low-temperature fluid inlet (21a) at a location corresponding to an intermediate position between a CO2 inlet (22a) and a CO2 outlet (22b) in the liquefaction target flow path (22); and a low-temperature fluid outlet (21b) at a location corresponding to the CO2 inlet (22a) of the liquefaction target flow path 22. In the low-temperature flow path (21): the low-temperature liquefied gas received through the low-temperature fluid inlet (21a) is heated to be a vaporized gas by exchanging heat with carbon dioxide flowing in a first prescribed region of the liquefaction target flow path (22); and, via a CO2-outlet opening (21c) provided at a position corresponding to the CO2 outlet (22b) of the liquefaction target flow path (22), said heated vaporized gas is caused to exchange heat with carbon dioxide flowing in a second prescribed region of the liquefaction target flow path (22).

Description

Heat exchangers and heat exchange systems

[0001] The present invention relates to a heat exchanger and a heat exchange system.

[0002] Conventionally, a heat exchange system including a heat exchanger that liquefies a gas to be liquefied by utilizing the cold energy of a low-temperature liquefied gas such as liquefied natural gas (hereinafter referred to as LNG) or liquefied hydrogen is known (see, for example, Patent Document 1). The heat exchanger includes a low-temperature flow path through which LNG (an example of a low-temperature liquefied gas) flows and a gas to be liquefied flow path through which nitrogen, the gas to be liquefied, flows. The LNG is heated and vaporized by heat exchange with the nitrogen in the heat exchanger. Meanwhile, the nitrogen, the gas to be liquefied, is cooled and liquefied by heat exchange with the LNG in the heat exchanger.

[0003] It is conceivable to use carbon dioxide instead of nitrogen as the gas to be liquefied in the heat exchanger and heat exchange system shown in Patent Document 1. Carbon dioxide liquefaction technology has become increasingly important in recent years as it is used for liquefying and capturing carbon dioxide amid growing demand for carbon neutrality.

[0004] However, the temperature of the low-temperature liquefied gas used to cool carbon dioxide in the heat exchanger is, for example, -150°C to -160°C, which is significantly lower than the solidification temperature (approximately -56°C) of carbon dioxide at typical pressures (0.52 MPa to 3 MPa) during storage and transportation. Therefore, there is a risk that the carbon dioxide flowing through the gas flow path to be liquefied in the heat exchanger will solidify due to the cold heat of the low-temperature liquefied gas, causing blockage of the flow path.

[0005] Japanese Patent Application Laid-Open No. 2019-168207

[0006] The present invention aims to suppress solidification of carbon dioxide due to the cold energy of low-temperature liquefied gas in a heat exchanger and heat exchange system that liquefies carbon dioxide using the cold energy of low-temperature liquefied gas.

[0007] The heat exchanger according to the present invention is a heat exchanger that liquefies gaseous carbon dioxide by utilizing the cold energy of a low-temperature liquefied gas, and includes a low-temperature flow path having a low-temperature fluid inlet into which the low-temperature liquefied gas is introduced and a low-temperature fluid outlet from which vaporized gas obtained after the low-temperature liquefied gas is vaporized; ２ Inlet and outlet CO2 after liquefaction ２ and a flow path to be liquefied having an outlet, and the low-temperature flow path is configured to ２ Entrance and CO ２ The low-temperature fluid inlet is located at a position corresponding to an intermediate position between the low-temperature fluid inlet and the CO ２ The low-temperature liquefied gas received from the low-temperature fluid inlet is heated and vaporized by circulating the gas while exchanging heat with carbon dioxide flowing through a first predetermined region of the flow path to be liquefied, and the heated vaporized gas is refrigerated by evaporating the CO ２ CO corresponding to the exit ２ The low-temperature fluid is configured to be discharged from the low-temperature fluid outlet after heat exchange with the carbon dioxide flowing through the second predetermined region of the liquefaction target flow path via the outlet-corresponding position.

[0008] FIG. 1 is a system diagram schematically illustrating the configuration of a heat exchange system including a heat exchanger according to a first embodiment. FIG. 2 is a diagram showing a schematic cross section of a heat exchanger body. FIG. 3 is a TQ diagram showing temperature changes of a working fluid of a heat exchange system, with heat quantity (enthalpy) on the horizontal axis and temperature on the vertical axis. FIG. 4 is a diagram corresponding to FIG. 1, illustrating a modification of the first embodiment. FIG. 5 is a system diagram schematically illustrating the configuration of a heat exchange system including a heat exchanger according to a second embodiment. FIG. 6 is a diagram corresponding to FIG. 5, illustrating a modification of the second embodiment. FIG. 7 is a system diagram schematically illustrating the configuration of a heat exchange system including a heat exchanger according to a third embodiment. FIG. 8 is a diagram corresponding to FIG. 3, illustrating the third embodiment. FIG. 9 is a diagram corresponding to FIG. 7, illustrating a modification of the third embodiment. FIG. 10 is a diagram corresponding to FIG. 3, illustrating another embodiment. FIG. 11 is a diagram corresponding to FIG. 3, illustrating another embodiment.

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0010] 1 is a system diagram that schematically illustrates the configuration of a heat exchange system 1 including a heat exchanger 2 according to Embodiment 1. The heat exchange system 1 is a system that liquefies gaseous carbon dioxide by utilizing the cold energy of liquefied natural gas (hereinafter referred to as LNG), which is an example of a low-temperature liquefied gas, and vaporizes the LNG to produce natural gas (an example of a vaporized gas, hereinafter referred to as NG).

[0011] Specifically, the heat exchange system 1 includes a heat exchanger 2 that performs heat exchange between LNG and carbon dioxide, an LNG supply flow path 3 that guides LNG supplied from an LNG supply source provided outside the heat exchange system 1 to the heat exchanger 2, an NG discharge flow path 4 that discharges NG vaporized in the heat exchanger 2 to the outside of the heat exchange system 1, a liquefaction target supply flow path 5 that supplies gaseous carbon dioxide to be liquefied to the heat exchanger 2, and a CO 2 discharge flow path 6 that discharges the carbon dioxide liquefied in the heat exchanger 2. ２ The LNG supply system includes a discharge flow path 6, a bypass flow path 7 branching off from the LNG supply flow path 3, a bypass valve 8 provided in the bypass flow path 7, a temperature sensor 9 as a temperature detection unit, and a controller 100 as a control unit.

[0012] [Configuration of Heat Exchanger] The heat exchanger 2 has a liquefaction target flow path 22 through which carbon dioxide to be liquefied is introduced and flows, a low-temperature flow path 21 through which LNG is introduced and flows, and a heat exchanger main body 20 that has therein a part of the low-temperature flow path 21 and the entire liquefaction target flow path 22. The low-temperature flow path 21 is formed so that a part of it is exposed to the outside of the heat exchanger main body 20. The liquefaction target flow path 22 is formed entirely inside the heat exchanger main body 20. The heat exchanger 2 is configured to perform heat exchange between the carbon dioxide flowing through the liquefaction target flow path 22 and the LNG introduced into the low-temperature flow path 21.

[0013] 1, the heat exchange areas in this heat exchanger 2 are roughly divided into an upper heat exchange area A1 located in the upper section of the heat exchanger body 20, a middle heat exchange area A2 located in the middle section, and a lower heat exchange area A3 located in the lower section. In the following description, unless otherwise specified, the terms "upper section," "middle section," and "lower section" refer to the sections corresponding to the upper heat exchange area A1, the middle heat exchange area A2, and the lower heat exchange area A3, respectively.

[0014] The heat exchanger body 20 is configured as a stacked heat exchanger, as will be described later. The heat exchanger body 20 is disposed vertically so that the carbon dioxide flowing through the liquefaction target flow path 22 flows from the top to the bottom.

[0015] The liquefaction target flow path 22 is a CO ２ inlet 22a and a CO ２ and an outlet 22b. ２ The inlet 22a is connected to the liquefaction object supply flow path 5, and CO ２ The CO ２ An exhaust flow path 6 is connected. ２ The inlet 22a receives gaseous carbon dioxide supplied from the liquefaction target supply flow path 5. ２ The outlet 22b is for discharging the carbon dioxide liquefied in the liquefaction target flow path 22 into the CO ２ It is discharged toward the discharge flow path 6. ２ The inlet 22a opens to the outer surface of the upper end of the heat exchanger body 20, and ２ The outlet 22b opens to the outer surface of the lower end of the heat exchanger body 20.

[0016] In this example, the liquefaction target flow path 22 extends linearly in the vertical direction. The liquefaction target flow path 22 has an upper flow path section 22c, a middle flow path section 22d, and a lower flow path section 22e, which correspond to the upper, middle, and lower stages of the heat exchanger 2, respectively. Note that the liquefaction target flow path 22 does not necessarily have to be linear, and may be formed in a spiral or zigzag shape, for example.

[0017] The low-temperature flow path 21 has an LNG inlet 21a (corresponding to a low-temperature fluid inlet) located at its upstream end in the flow direction of the LNG, and an NG outlet 21b (corresponding to a low-temperature fluid outlet) located at its downstream end. ２ an upper heat exchange area A1 including an inlet 22a; ２ The LNG inlet 21a is connected to the LNG supply passage 3. The CO outlet 21b is connected to the CO ２ The low-temperature flow path 21 is provided in the upper heat exchange area A1 including the inlet 22a. The NG outlet 21b is connected to the NG discharge flow path 4. The LNG inlet 21a receives LNG supplied from the LNG supply flow path 3. The NG outlet 21b discharges NG vaporized in the low-temperature flow path 21 toward the NG discharge flow path 4.

[0018] The LNG inlet 21a opens to the outer surface of the heat exchanger body 20 at the middle part in the vertical direction. ２ The inlets 22a are arranged at intervals from each other on the same surface (the upper end surface in this example) of the upper end of the heat exchanger body 20.

[0019] Furthermore, at the lower end of the heat exchanger body 20, ２ An outlet-corresponding opening 21c is formed. ２ The outlet-corresponding opening 21c is located midway along the low-temperature flow path 21 and ２ CO corresponding to outlet 22b ２ It is located at the exit. ２ The outlet-corresponding opening 21c is arranged so that the NG vaporized by passing through the middle flow path section 21e of the low-temperature flow path 21, which will be described later, passes through it. ２ The outlet corresponding opening 21c and CO ２ The outlet 22b is arranged on the same surface (the lower end surface in this example) of the lower end of the heat exchanger body 20 with a gap therebetween.

[0020] The low-temperature flow path 21 includes a middle-stage flow path section 21e (corresponding to the first flow path section) located in the middle stage of the heat exchanger body 20, a lower-stage flow path section 21g (corresponding to the second flow path section) located in the lower stage section, an upper-stage flow path section 21i (corresponding to the third flow path section) located in the upper stage section, an internal supply flow path 21d connecting the LNG inlet 21a and the upstream end of the middle-stage flow path section 21e, a first connecting flow path section 21f connecting the downstream end of the middle-stage flow path section 21e and the upstream end of the lower-stage flow path section 21g, and a second connecting flow path section 21h connecting the downstream end of the lower-stage flow path section 21g and the upstream end of the upper-stage flow path section 21i. The middle-stage flow path section 21e, the lower-stage flow path section 21g, and the upper-stage flow path section 21i all extend in the vertical direction parallel to the liquefaction target flow path 22 and are configured to allow NG to flow from the bottom to the top.

[0021] More specifically, the middle flow path section 21e heats and vaporizes the LNG received from the LNG inlet 21a by performing countercurrent heat exchange between the LNG and carbon dioxide flowing through the middle flow path section 22d (corresponding to the intermediate region of the liquefaction target flow path) of the liquefaction target flow path 22, and discharges it as NG.

[0022] The first connecting flow path portion 21f guides the NG that has reached the downstream end of the middle flow path portion 21e to the outside from the side surface of the heat exchanger body 20, and then guides the NG to the CO ２ It is supplied to the outlet corresponding opening 21c.

[0023] The lower flow path portion 21g receives CO from the first connecting flow path portion 21f. ２ Outlet corresponding opening 21c (CO ２ The NG supplied to the outlet (position corresponding to the outlet) is received, and heat exchange is carried out in a countercurrent manner between the received NG and carbon dioxide flowing in the lower flow path section 22e of the flow path 22 to be liquefied (corresponding to the downstream region downstream of the intermediate region in the flow path to be liquefied).

[0024] The second connection flow path section 21h first guides the NG that has reached the downstream end of the lower flow path section 21g to the outside of the heat exchanger main body 20 (to the right in the example of Figure 1), and then supplies it to the upper flow path section 21i.

[0025] The upper flow path section 21i receives the NG supplied from the second connection flow path section 21h, performs countercurrent heat exchange with the carbon dioxide flowing in the upper flow path section 22c (corresponding to the upstream region upstream of the intermediate region in the liquefaction target flow path) of the liquefaction target flow path 22, and then discharges it from the NG outlet 21b into the NG discharge flow path 4.

[0026] 2 is a schematic cross-sectional view of the heat exchanger body 20. As shown in this figure, the heat exchanger body 20 is configured as a microchannel type laminated heat exchanger, for example. That is, the heat exchanger body 20 is configured by alternately laminating a number of first metal layers 201 and a number of second metal layers 202. The first metal layer 201 has a number of NG flow path portions 201a recessed therein through which NG flows. These NG flow path portions 201a constitute a part of the low-temperature flow path 21. The second metal layer 202 has a number of CO ２ The flow path portion 202a is recessed. ２ The flow path portion 202a constitutes a part of the liquefaction target flow path 22. The first metal layer 201 and the second metal layer 202 are each made of a metal plate with excellent heat transfer characteristics. NG flowing through each NG flow path portion 201a formed in the first metal layer 201 and each CO flow path portion 201a formed in the second metal layer 202 are ２ Heat exchange occurs between the NG and the carbon dioxide flowing through the flow path 202a, whereby the NG is heated and the carbon dioxide is cooled. The carbon dioxide is liquefied by being cooled and is discharged to the outside of the heat exchanger main body 20.

[0027] 2 shows an example of a stacking pattern in which one first metal layer 201 and one second metal layer 202 are alternately stacked. However, this is not limiting. For example, two first metal layers 201 and one second metal layer 202 may be alternately stacked, three first metal layers 201 and one second metal layer 202 may be alternately stacked, or three first metal layers 201 and two second metal layers 202 may be alternately stacked. That is, the stacking pattern of the first metal layers 201 and the second metal layers 202 may be any pattern. Furthermore, in the example of FIG. 2, the heat exchanger body 20 is shown as a microchannel-type stacked heat exchanger. However, this is not limiting. For example, the heat exchanger body 20 may be configured as a plate-fin-type stacked heat exchanger.

[0028] However, if the heating capacity of the LNG in the middle-stage flow path section 21e is too high, the temperature of the NG discharged from the middle-stage flow path section 21e becomes excessively high. As a result, the NG, which is a low-temperature fluid, flowing through the lower-stage flow path section 21g and the upper-stage flow path section 21i, which are located downstream of the middle-stage flow path section 21e, cannot sufficiently cool the carbon dioxide, which is a high-temperature fluid, resulting in a problem of a decrease in the cooling capacity (i.e., liquefaction capacity) of the carbon dioxide in the heat exchanger 2.

[0029] To avoid this problem, in this embodiment, bypass valve control is executed by the controller 100. Details of the bypass valve control will be described below along with the configurations of the bypass flow path 7 and the bypass valve 8.

[0030] The bypass flow path 7 branches off from the LNG supply flow path 3 and bypasses the middle-stage flow path section 21e to be connected to the first connecting flow path section 21f. In other words, the bypass flow path 7 has an upstream end connected to the LNG supply flow path 3 and a downstream end connected to the first connecting flow path section 21f. By employing such a bypass structure, the heated NG that has passed through the middle-stage flow path section 21e and the LNG that has passed through the bypass flow path 7 are mixed at a connection site P1 (a predetermined site) of the first connecting flow path section 21f with the bypass flow path 7, and this mixed fluid (hereinafter referred to as mixed NG) is CO ２ The gas flows into the lower flow path portion 21g via the outlet-corresponding opening 21c.

[0031] The bypass valve 8 is disposed in the bypass flow path 7. The bypass valve 8 is configured to be able to adjust the flow rate of LNG flowing through the bypass flow path 7 by changing the opening degree thereof. The bypass valve 8 is controlled by a controller 100.

[0032] The connection portion P1 of the low-temperature flow path 21 (specifically, the first connection flow path portion 21f) with the downstream end of the bypass flow path 7 and the CO ２ The temperature sensor 9 (an example of a temperature detection unit) is connected to the portion between the outlet-corresponding opening 21c. ２ The temperature of the mixed NG is detected between the outlet-corresponding opening 21c and the controller 100, and the detected temperature information is transmitted to the controller 100. The temperature sensor 9 may be a sensor that detects a temperature correlated with the temperature of the mixed NG (for example, the temperature of the pipe wall through which the mixed NG flows).

[0033] The controller 100 is configured by a computer having a CPU, ROM, and RAM, and is connected to the temperature sensor 9 and the bypass valve 8 via signal lines.

[0034] The controller 100 acquires the temperature detected by the temperature sensor 9 and controls the opening of the bypass valve 8 so that the acquired detected temperature becomes a predetermined target temperature.

[0035] This predetermined target temperature is ２ The temperature of the liquefied carbon dioxide discharged from the outlet 22b is set to a predetermined required temperature, and the CO ２ The temperature is preset to a value that will prevent the carbon dioxide from solidifying on the inner surface of the outlet 22b. ２The temperature of the mixed NG, which is the low-temperature fluid flowing into the heat exchanger 2 from the outlet-corresponding opening 21c, also increases, reducing the cooling capacity of the mixed NG for carbon dioxide, resulting in problems such as a partial or complete liquefaction of the carbon dioxide or a temperature of the carbon dioxide after liquefaction that is higher than the predetermined required temperature. On the other hand, if this target temperature is too low, the temperature of the mixed NG, which is the low-temperature fluid flowing into the heat exchanger 2, also decreases, increasing the cooling capacity of the mixed NG for carbon dioxide, resulting in problems such as a temperature of the carbon dioxide after liquefaction that is lower than the predetermined required temperature. In addition, if this target temperature is too low, the cold energy of the mixed NG will cause the CO2 in the liquefaction target flow path 22 to be cooled. ２ The temperature inside the outlet 22b becomes lower than the solidification temperature of carbon dioxide (-56°C in this example), and CO ２ Therefore, in this example, the predetermined target temperature is set so that the temperature of the liquefied carbon dioxide reaches a predetermined required temperature and the CO ２ The target temperature is set in advance to a temperature at which the carbon dioxide does not solidify at the outlet 22b. ２ The reason why the temperature at the outlet 22b is set so that carbon dioxide does not solidify is that in the heat exchange system 1 of this example, ２ This is because the temperature of the carbon dioxide becomes the lowest at the outlet 22b, making it easier for solidification to occur. In this embodiment, the target temperature is set to -56°C as an example, but is not limited to this and may be, for example, -50°C to -60°C. In other words, the target temperature is a temperature at which all of the carbon dioxide can be liquefied, and which is set so that the temperature of the liquefied carbon dioxide reaches a predetermined required temperature and the CO ２ Any temperature may be used as long as the carbon dioxide does not solidify on the inner surface of the outlet 22b.

[0036] [Explanation of TQ curve] Next, the basic operation of the heat exchanger 2 will be described with reference to Figures 1 and 3. Figure 3 is a TQ diagram showing the temperature change of each working fluid (LNG and carbon dioxide) of the heat exchanger 2, with the heat exchange amount on the horizontal axis and temperature on the vertical axis. The arrows on the temperature lines in this TQ diagram are shown to allow intuitive understanding of the flow direction of the working fluid. The dashed line in the figure indicates the direction of flow of the CO ２3 shows the temperature change of the LNG, and the thick solid line shows the temperature change of the LNG. The thin two-dot chain line in the figure shows the temperature change of the LNG in the conventional example. In addition, in FIG. 3, for the sake of simplicity, the explanation will be given assuming that the bypass flow rate of the LNG flowing through the bypass flow path 7 is 0. Furthermore, the temperature values ​​explained below are merely examples and are not limited to these.

[0037] 3, in the heat exchanger 2 of this embodiment, LNG is supplied from an LNG supply source provided outside the system 1 via the LNG supply passage 3 and the internal supply passage 21d to the middle flow passage 21e of the middle heat exchange area A2 at −150° C. Then, the LNG supplied to the middle flow passage 21e is heated to −50° C. (see FIG. 3) and vaporized to become NG by heat exchange with carbon dioxide flowing through the middle flow passage 22d of the liquefaction target passage 22.

[0038] The NG vaporized in the intermediate flow path portion 21e passes through the first connecting flow path portion 21f (see FIG. 1) and then is converted into CO ２ The carbon dioxide flows from the outlet-corresponding opening 21c into the lower flow path section 21g at −50° C. Then, in the lower flow path section 21g, heat exchange occurs with the carbon dioxide flowing in the lower flow path section 22e of the flow path 22 to be liquefied, increasing the amount of heat and warming the carbon dioxide to −30° C. (see FIG. 3).

[0039] The heated NG passes through the second connecting flow path portion 21h (see FIG. 1) and then flows into the upper flow path portion 21i of the low-temperature flow path 21. Then, in the upper flow path portion 21i, heat is exchanged with the carbon dioxide flowing in the upper flow path portion 22c of the liquefaction target flow path 22, thereby increasing the amount of heat and heating the NG to 5°C (an example of a predetermined required temperature), and the NG is discharged from the NG outlet 21b to the NG discharge flow path 4.

[0040] On the other hand, the carbon dioxide to be liquefied is liquefied in a CO ２The carbon dioxide gas is supplied from the supply source to the liquefaction-targeted flow path 22 as a gas at 30°C. The carbon dioxide gas supplied to the liquefaction-targeted flow path 22 gradually loses heat through heat exchange with the NG flowing through the upper flow path section 21i of the low-temperature flow path 21. As a result, the temperature of the carbon dioxide gradually decreases from 30°C until it reaches the liquefaction temperature of -17.2°C (under 2.1 MPa in this example). Upon reaching the liquefaction temperature, the carbon dioxide begins to condense from gas to liquid. During this condensation period, the carbon dioxide coexists as a gas and a liquid, and its temperature remains constant regardless of the decrease in heat content. When the heat content of the carbon dioxide further decreases and the condensation period ends, all of the carbon dioxide is liquefied. Thereafter, the temperature decreases as the heat content decreases, and the carbon dioxide is finally discharged from the liquefaction-targeted flow path 22 as liquid carbon dioxide at -42°C (an example of a predetermined required temperature). The predetermined required temperature can be set arbitrarily by the user and may be, for example, -42°C or lower.

[0041] (Operation and Effect) As described above, in this embodiment, the low-temperature flow path 21 has the LNG inlet 21 a at a position corresponding to the middle stage (an example of an intermediate position) of the liquefaction target flow path 22, and ２ The low-temperature flow path 21 heats the LNG received from the LNG inlet 21a by circulating it while exchanging heat with the carbon dioxide flowing through the middle flow path section 22d (an example of a first predetermined region) of the liquefaction target flow path 22, thereby converting it into NG. ２ CO at a position corresponding to the outlet 22b ２ It is configured to exchange heat with carbon dioxide flowing through the lower flow path section 22e and the upper flow path section 22c (an example of a second specified region) of the liquefaction target flow path 22 via the outlet corresponding opening 21c, and then discharge it from the NG outlet 21b.

[0042] According to this configuration, it is possible to suppress the solidification of carbon dioxide due to the cold heat of LNG. That is, according to the configuration, the LNG inlet 21a where the LNG has the lowest temperature is located at a position corresponding to the middle stage (an example of the intermediate position) of the liquefaction target flow path 22, so that the LNG inlet 21a is ２The CO ２ The temperature drop of the inner surface of the outlet 22b can be suppressed as much as possible, and as a result, the solidification of carbon dioxide can be suppressed. On the other hand, the middle stage portion (an example of the intermediate position) of the liquefaction target flow path 22 is cooled by the coldest LNG flowing into the LNG inlet 21a, but the carbon dioxide is not solidified by the CO ２ The gas state is near the inlet 22a, the condensed state is in the center, and CO ２ Since the CO 2 becomes liquid near the outlet 22b, the heat transfer coefficient of the condensed state at the intermediate position of the liquefaction target flow path 22 is usually ２ The heat transfer coefficient of the CO 2 in the liquid state near the outlet 22b is higher than that in the liquid state near the outlet 22b. ２ Therefore, as in the above configuration, it is preferable to dispose the LNG inlet 21a at the middle position of the liquefaction target flow path 22 in order to reduce the CO ２ This can suppress the solidification of carbon dioxide compared to when it is disposed near the outlet 22b.

[0043] In this embodiment, the upper flow path section 21i, the middle flow path section 21e, and the lower flow path section 21g of the low-temperature flow path 21 are configured to perform heat exchange by a counterflow method between the LNG introduced into the low-temperature flow path 21 and the carbon dioxide introduced into the liquefaction target flow path 22. Therefore, the temperature of the NG discharged from the heat exchanger 2 can be made higher than when a parallel flow method is adopted. Therefore, it is possible to widely accommodate the temperature range of the NG after evaporation desired by the user.

[0044] (Modification of First Embodiment) Figure 4 is a view corresponding to Figure 1, showing a modification of the first embodiment. This modification differs from the first embodiment in that the heat exchange method in the middle flow path section 21e of the low-temperature flow path 21 is a cross-flow type. In Figure 4, the same components as those in Figure 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0045] That is, in this modification, the middle flow path section 21e of the low-temperature flow path 21 is disposed so as to horizontally cross the heat exchanger body 20 from the LNG inlet 21a and to be perpendicular to the liquefaction target flow path 22 when viewed from the side. The LNG that flows into the middle flow path section 21e of the low-temperature flow path 21 from the LNG inlet 21a is heated and becomes NG by cross-flow heat exchange with the carbon dioxide flowing in the liquefaction target supply flow path 5. The heat exchange process after the LNG becomes NG is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0046] The heat exchanger 2 according to this modification has the same configuration as that of the first embodiment, except that the heat exchange method in the middle flow path section 21e of the low-temperature flow path 21 is a cross-flow method. Therefore, the same effects as those of the first embodiment can be obtained.

[0047] (Embodiment 2) Figure 5 is a system diagram showing a schematic configuration of a heat exchange system 1 including a heat exchanger 2 in embodiment 2. This embodiment differs from embodiment 1 in that the low-temperature flow path 21 includes a middle-stage flow path section 21q and a full-stage flow path section 21s arranged in parallel to each other. In Figure 5, the same components as those in embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0048] That is, in this embodiment, the heat exchanger 2 has a middle-stage flow path section 21q (corresponding to the first flow path section) extending parallel to the liquefaction-target flow path 22 in the middle section in the vertical direction of the heat exchanger main body 20, an all-stage circulation flow path section 21s (corresponding to the second flow path section) arranged throughout the entire vertical direction of the heat exchanger main body 20 and extending parallel to the liquefaction-target flow path 22, an internal supply flow path section 21p connecting the upstream end of the middle-stage flow path section 21q to the LNG inlet 21a, and a connection flow path section 21r connecting the downstream end of the middle-stage flow path section 21q to the upstream end of the all-stage circulation flow path section 21s.

[0049] The internal supply passage section 21p supplies LNG received from the LNG inlet 21a to the intermediate passage section 21q.

[0050] The middle flow path section 21q heats and vaporizes the LNG supplied from the internal supply flow path section 21p by performing countercurrent heat exchange between the LNG and carbon dioxide flowing through the middle flow path section 22d (corresponding to the intermediate region) of the liquefaction target flow path 22, and discharges it as NG.

[0051] The connecting flow path section 21r guides the NG that has reached the downstream end of the intermediate flow path section 21q to the outside from the side surface of the heat exchanger body 20, and then guides the NG to the CO 2 formed at the lower end of the heat exchanger body 20. ２ It is supplied to the outlet corresponding opening 21c.

[0052] The all-stage flow passage section 21s flows CO 2 through the connection flow passage section 21r. ２ Outlet corresponding opening 21c (CO ２ The NG supplied to the liquefaction target flow path 22 is received at the NG outlet 21b (position corresponding to the outlet), and heat exchange is carried out in a counterflow manner over the entire vertical area between the received NG and the carbon dioxide flowing through the liquefaction target flow path 22, and then the NG is discharged from the NG outlet 21b into the NG discharge flow path 4.

[0053] According to the heat exchanger 2 and heat exchange system 1 configured as described above, the all-stage flow passage section 21s of the low-temperature flow passage 21 is configured to exchange heat with the carbon dioxide flowing through the liquefaction target flow passage 22 over the entire region in the flow path length direction of the liquefaction target flow passage 22. Therefore, since there is no need to extend the all-stage flow passage section 21s to the outside of the heat exchanger 2 along the way, the flow passages for heat exchange can be concentrated as much as possible within the heat exchanger 2, and the number of connecting pipes can be reduced.

[0054] (Modification of Embodiment 2) Figure 6 is a view corresponding to Figure 5, showing a modification of Embodiment 2. This modification differs from Embodiment 2 in that the heat exchange method in the middle flow path section 21q of the low-temperature flow path 21 is a cross-flow type. In Figure 6, the same components as those in Figure 5 are assigned the same reference numerals, and detailed description thereof will be omitted.

[0055] That is, in this modification, the middle flow path section 21q of the low-temperature flow path 21 is disposed so as to horizontally cross the heat exchanger body 20 from the LNG inlet 21a and to be perpendicular to the liquefaction target flow path 22 when viewed from the side. The LNG that flows into the middle flow path section 21q of the low-temperature flow path 21 from the LNG inlet 21a is heated and becomes NG by cross-flow heat exchange with the carbon dioxide flowing in the liquefaction target supply flow path 5. The heat exchange process after the LNG becomes NG is the same as in the second embodiment, and therefore a description thereof will be omitted.

[0056] The heat exchanger 2 of this modified example has the same configuration as that of the second embodiment, except that the heat exchange method in the middle flow path section 21q of the low-temperature flow path 21 is a cross-flow method. Therefore, the same effects as those of the second embodiment can be obtained.

[0057] (Embodiment 3) Fig. 7 is a system diagram that schematically illustrates the configuration of a heat exchange system 1 including a heat exchanger 2 according to embodiment 3, and Fig. 8 is a diagram corresponding to Fig. 3 that illustrates embodiment 3. This embodiment differs from embodiment 1 in that the low-temperature flow path 21 includes a lower flow path section 21u that is a heat exchange flow path section that uses a parallel flow system. In Fig. 7, the same components as those in embodiment 1 are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0058] Specifically, in this embodiment, the heat exchange area of ​​the heat exchanger 2 is broadly divided into an upper heat exchange area B1 and a lower heat exchange area B2, and the upper heat exchange area B1 performs counterflow heat exchange, while the lower heat exchange area B2 performs parallel flow heat exchange.

[0059] The liquefaction target flow path 22 is a linear flow path that extends over the entire heat exchanger 2 in the vertical direction.

[0060] The low-temperature flow path 21 has a lower-stage flow path section 21u (corresponding to the first flow path section) located in the lower stage section of the heat exchanger main body 20, an upper-stage flow path section 21w (corresponding to the second flow path section) located in the upper stage section, an internal supply flow path section 21t connecting the LNG inlet 21a and the upstream end of the lower-stage flow path section 21u, and a connection flow path section 21v connecting the downstream end of the lower-stage flow path section 21u and the upstream end of the upper-stage flow path section 21w.

[0061] The lower flow path section 21u and the upper flow path section 21w both extend in the vertical direction parallel to the liquefaction target flow path 22. The lower flow path section 21u is configured to allow NG to flow from the upper side to the lower side, while the upper flow path section 21w is configured to allow NG to flow from the lower side to the upper side.

[0062] The lower flow path 21u heats and vaporizes the LNG received from the LNG inlet 21a through the internal supply flow path 21t by performing heat exchange between the LNG and the carbon dioxide flowing through the lower flow path 22g of the liquefaction target flow path 22 in a parallel flow manner. ２ The liquid is discharged from the outlet-corresponding opening 21c to the connecting flow path portion 21v.

[0063] The connecting flow path section 21v first guides the NG that has reached the downstream end of the lower flow path section 21u to the outside from the lower end of the heat exchanger main body 20, and then supplies it into the upper flow path section 21w from the lower end of the upper flow path section 21w.

[0064] The upper flow path section 21w receives the NG supplied from the connecting flow path section 21v and heats the NG to a predetermined required temperature by countercurrent heat exchange between the received NG and the carbon dioxide flowing in the upper flow path section 22f of the liquefaction target flow path 22. The upper flow path section 21w discharges the heated NG from the NG outlet 21b to the NG discharge flow path 4.

[0065] Furthermore, the heat exchanger 2 of this embodiment has a bypass flow path 7 and a bypass valve 8, similar to the first embodiment. The bypass flow path 7 branches off from the LNG supply flow path 3, bypasses the lower flow path portion 21u, and is connected to the connection flow path portion 21v. In other words, the bypass flow path 7 has an upstream end connected to the LNG supply flow path 3 and a downstream end connected to the connection flow path portion 21v.

[0066] By employing such a bypass structure, the heated NG that has passed through the lower flow path section 21u and the LNG that has passed through the bypass flow path 7 are mixed at a connection site P1 of the connecting flow path section 21v with the bypass flow path 7, and this mixed NG flows into the upper flow path section 21w through the connecting flow path section 21v. While flowing through the upper flow path section 21w, the mixed NG is heated by the carbon dioxide flowing through the upper flow path section 22f of the liquefaction target flow path 22, and becomes NG, which is discharged from the NG outlet 21b to the NG discharge flow path 4.

[0067] The temperature sensor 9 is connected to the CO ２ The temperature sensor 9 detects the temperature of the vaporized gas NG after being vaporized in the lower flow path portion 21u and before being combined with the LNG that has passed through the bypass flow path 7. The temperature sensor 9 may be a sensor that detects a temperature correlated with the temperature (for example, the temperature of the pipe wall through which the NG flows). The controller 100 controls the opening of the bypass valve 8 provided in the bypass flow path 7 so that the temperature detected by the temperature sensor 9 becomes a predetermined target temperature. This target temperature is determined by the temperature sensor 9. ２ The temperature of the carbon dioxide discharged from the outlet 22b is set to a predetermined required temperature and the CO ２ The temperature is preset at a level that will prevent carbon dioxide from solidifying at the outlet 22b.

[0068] [Explanation of TQ Curve] Next, the basic operation of the heat exchanger 2 in the third embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 8 is a diagram corresponding to Fig. 3 and shows the third embodiment. The dashed line in the figure indicates the CO ２ 8 shows the temperature change of the LNG, and the thick solid line shows the temperature change of the LNG. The thin two-dot chain line in the figure shows the temperature change of the LNG in the conventional example. In addition, in FIG. 8, for the sake of simplicity, the explanation will be given assuming that the bypass flow rate of the LNG flowing through the bypass flow path 7 is 0. Furthermore, the temperature values ​​explained below are merely examples and are not limited to these.

[0069] In the heat exchanger 2 of this embodiment, LNG is supplied from an LNG supply source provided outside the system 1 via the internal supply passage 21t to the upper end of the lower passage 21u at a temperature of −150° C. Then, while flowing from top to bottom within the lower passage 21u, the LNG supplied to the upper end of the lower passage 21u is heated to −50° C. (see FIG. 8 ) by heat exchange with carbon dioxide flowing within the lower passage 22g of the liquefaction-target passage 22. The lower passage 22g of the liquefaction-target passage 22 corresponds to the outlet region.

[0070] The heated NG flows into the CO ２ After passing through the outlet-corresponding opening 21c, the NG is supplied to the lower end of the upper-stage flow path section 21w via the connecting flow path section 21v. As the NG flows from the bottom to the top of the upper-stage flow path section 21w, it exchanges heat with the carbon dioxide in the upper-stage flow path section 22f of the liquefaction-target flow path 22, whereby it is heated to 5°C (an example of the predetermined required temperature), and is finally discharged from the NG outlet 21b. The upper-stage flow path section 22f of the liquefaction-target flow path 22 corresponds to the inlet-side region.

[0071] On the other hand, the carbon dioxide to be liquefied is liquefied in a CO ２ The gas is supplied from the supply source to the flow path 22 to be liquefied as a gas at 30°C, cooled to the liquefaction temperature of -17.2°C while flowing through the upper flow path section 22f, and then cooled to -42°C (an example of a predetermined required temperature) while flowing through the lower flow path section 22g, and is then supplied to the flow path 22 as liquid carbon dioxide. ２ The water is discharged from the outlet 22b. The predetermined required temperature can be set arbitrarily by the user, and may be, for example, −42° C. or lower.

[0072] As described above, in the third embodiment, the heat exchange method between the LNG introduced into the low-temperature flow path 21 and the carbon dioxide introduced into the liquefaction target flow path 22 can be realized by combining the parallel flow method and the counter flow method. Therefore, the temperature of the NG discharged from the heat exchanger 2 can be made higher than when the parallel flow method is adopted over the entire flow path. Therefore, it is possible to widely accommodate the temperature range of the NG desired by the user. Furthermore, by adopting the parallel flow method for the lower flow path section 21u, the CO ２ The flow path configuration leading to the outlet corresponding opening 21c can be simplified, and therefore the problems of increased costs and increased assembly steps due to a complicated flow path configuration can be avoided.

[0073] In addition, the heat exchange system 1 of this embodiment has a CO ２ The bypass flow passage 7 is connected to a connection site P1 (predetermined site) downstream of the outlet-corresponding opening 21c, and a bypass valve 8 is provided in the bypass flow passage 7.

[0074] According to this configuration, the bypass flow path 7 branches off from the LNG supply flow path 3, bypasses the first flow path portion, and then ２ Therefore, by adjusting the opening of the bypass valve 8 and adjusting the flow rate of the LNG flowing into the lower flow path section 21u, the CO ２ The temperature of the NG at the outlet corresponding opening 21c can be easily adjusted. In turn, the temperature of the liquefied carbon dioxide discharged from the heat exchanger 2 can be easily controlled. The opening of this bypass valve 8 is controlled by the controller 100 so that the temperature detected by the temperature sensor 9 becomes a predetermined target temperature, so that adjustment can be made more easily than when the bypass valve 8 is controlled manually. In addition, the predetermined target temperature is set by the controller 100 so that the temperature detected by the temperature sensor 9 becomes a predetermined target temperature. ２ The temperature of the carbon dioxide discharged from the outlet 22b is set to a predetermined required temperature and the CO ２The temperature is preset to a value that will prevent the carbon dioxide from solidifying at the outlet 22b, thereby preventing the carbon dioxide from solidifying due to the cold heat of the LNG.

[0075] (Modification of Embodiment 3) Fig. 9 is a view corresponding to Fig. 7 showing a modification of Embodiment 3. This modification differs from Embodiment 3 in that the low-temperature flow path 21 includes an all-stage flow path section 21y in addition to a lower-stage flow path section 21u. Note that in Fig. 9, the same components as those in Fig. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0076] That is, in this modified example, the low-temperature flow path 21 has a lower-stage flow path section 21u (corresponding to the first flow path section) extending parallel to the liquefaction-target flow path 22 in the lower stage section of the heat exchanger main body 20, an all-stage circulation flow path section 21y (corresponding to the second flow path section) arranged throughout the entire vertical direction of the heat exchanger main body 20 and extending parallel to the liquefaction-target flow path 22, an internal supply flow path section 21t connecting the upstream end of the lower-stage flow path section 21u to the LNG inlet 21a, and a connection flow path section 21x connecting the downstream end of the lower-stage flow path section 21u to the upstream end of the all-stage circulation flow path section 21s.

[0077] The internal supply passage section 21t supplies LNG received from the LNG inlet 21a to the lower passage section 21u.

[0078] The lower flow path section 21u circulates the LNG supplied from the internal supply flow path section 21t from the top to the bottom, thereby performing parallel flow heat exchange with the carbon dioxide flowing in the lower flow path section 22g of the liquefaction target flow path 22. The lower flow path section 21u then heats and vaporizes the LNG through heat exchange with the carbon dioxide, and discharges it as NG to the connection flow path section 21x.

[0079] The connecting flow path section 21x guides the NG that has reached the downstream end of the lower flow path section 21u from the lower end of the heat exchanger body 20 to the outside, and then guides the NG to the CO 2 formed at the lower end of the heat exchanger body 20. ２ It is supplied to the outlet corresponding opening 21c.

[0080] The all-stage flow passage section 21y receives CO from the connection flow passage section 21x. ２The NG supplied to the outlet-corresponding opening 21c is circulated from the bottom to the top, thereby performing counterflow heat exchange across all vertical stages between the LNG and the carbon dioxide flowing through the liquefaction target flow path 22. The all-stage flow path section 21y heats the LNG to a predetermined required temperature through heat exchange with the carbon dioxide, and discharges the LNG from the NG outlet 21b to the NG discharge flow path 4.

[0081] Next, the bypass flow path structure in this modification will be described. The bypass flow path 7 branches off from the LNG supply flow path 3, bypasses the lower flow path section 21u, and is connected to the connection flow path section 21x. In other words, the bypass flow path 7 has an upstream end connected to the LNG supply flow path 3 and a downstream end connected to the connection flow path section 21x.

[0082] According to this bypass structure, the heated NG that has passed through the lower-stage flow path section 21u and the LNG that has passed through the bypass flow path 7 are mixed at the connection site P1 of the connecting flow path section 21x with the bypass flow path 7, and this mixed NG flows into the all-stage flow path section 21y through the connecting flow path section 21v. As the mixed NG flows through the all-stage flow path section 21y, it exchanges heat with the carbon dioxide in the liquefaction target flow path 22 and is heated to a predetermined required temperature. The heated NG is discharged from the NG outlet 21b.

[0083] The temperature sensor 9 is connected to the connection portion P1 of the connection flow path portion 21x. ２ The controller 100 controls the opening of the bypass valve 8 provided in the bypass flow path 7 so that the temperature detected by the temperature sensor 9 becomes a predetermined target temperature. ２ The temperature of the carbon dioxide discharged from the outlet 22b is set to a predetermined required temperature and the CO ２ The temperature is preset at a level that will prevent carbon dioxide from solidifying at the outlet 22b.

[0084] As described above, in this modification, heat exchange is performed by a parallel flow method in the lower flow path section 21u of the low-temperature flow path 21, thereby achieving the same effects as those of the third embodiment. Moreover, in this modification, the all-stage flow path section 21y is configured to perform heat exchange with the carbon dioxide flowing through the entire region in the flow path length direction of the liquefaction target flow path 22, so it is necessary to extend the all-stage flow path section 21y to the outside of the heat exchanger 2 from a certain point. Therefore, the flow paths for heat exchange can be concentrated as much as possible within the heat exchanger 2, thereby reducing the number of connecting pipes.

[0085] Other Embodiments Although the heat exchanger 2 and the heat exchange system 1 according to the embodiment of the present invention have been described above, the present invention is not limited to this.

[0086] (1) In each of the above-described embodiments and modified examples, the liquefaction target flow path 22 of the heat exchanger 2 and the low-temperature flow path 21 excluding the middle flow path section 21 e in FIG. 4 and the middle flow path section 21 q in FIG. 6 are extended in the vertical direction, but this is not limited to this and they may be arranged, for example, in a zigzag pattern or a serpentine pattern.

[0087] (2) In the above-described embodiments and modifications, the heat exchanger 2 is configured as a single unit. However, the present invention is not limited to this. For example, the heat exchanger 2 may be divided into two or three parts.

[0088] (3) In each of the above embodiments and modifications, the CO ２ The inlet 22a and the NG outlet 21b are disposed on the upper surface of the upper end of the heat exchanger 2. ２ Outlet 22b and CO ２ The outlet-corresponding opening 21c is disposed on the lower surface of the lower end of the heat exchanger 2, but is not limited thereto. For example, ２ Either or both of the inlet 22a and the NG outlet 21b may be disposed on the side surface of the upper end. ２ Outlet 22b and CO ２ Either or both of the outlet-corresponding openings 21c may be disposed on the side surface of the lower end portion.

[0089] (4) In each of the above embodiments and variants, the heat exchange system 1 has a bypass flow path 7 and a bypass valve 8, but this is not limited to this, and the heat exchange system 1 may be configured without the bypass flow path 7 and the bypass valve 8.

[0090] (5) In each of the above embodiments and modifications, the heat exchanger 2 is configured as a stacked heat exchanger, but this is not limited to this and may be, for example, an aluminum plate fin heat exchanger or the like.

[0091] (6) In the above-described embodiments and modifications, LNG (liquefied natural gas) is used as an example of liquefied gas. However, the present invention is not limited to this. For example, LH ２ 10 shows an example in which LNG is used in the heat exchanger 2 of the first embodiment. ２ 11 shows a TQ curve when LH is used instead of LNG in the heat exchanger 2 of the third embodiment. ２ 10 and 11 show the TQ curves when the LH ２ The temperature is approximately the same as in the first and third embodiments except that it is −250° C., so a detailed description thereof will be omitted.

[0092] (7) In each of the above embodiments and modifications, the gaseous carbon dioxide supplied to the liquefaction target flow path 22 does not need to be 100% carbon dioxide, and for example, the gaseous carbon dioxide may contain components with low melting points, such as nitrogen, as impurities. In other words, the fluid supplied to the liquefaction target flow path 22 may be any fluid that contains carbon dioxide.

[0093] (8) In each of the above embodiments and modifications, CO ２ The temperature of NG at the outlet opening 21c is set to -50°C, but is not limited to this and may be, for example, -50°C to -60°C. That is, the solidification temperature of carbon dioxide is -56°C under the pressure (0.52 MPa to 3 MPa) during general storage and transportation. ２If the temperature of the NG at the outlet opening 21c is higher than −56° C., the problem of solidification of carbon dioxide will not occur. ２ The temperature of the NG at the outlet opening 21c is set to −50° C., which is higher than −56° C., but it does not necessarily have to be higher than −56° C. ２ The temperature of the NG at the outlet corresponding opening 21c may be about −60° C. ２ The temperature of the NG at the outlet opening 21c is ２ Any temperature may be used as long as the temperature of the carbon dioxide discharged from the outlet 22b is the predetermined required temperature and the carbon dioxide does not solidify.

[0094] The above-described specific embodiments mainly include inventions having the following configurations.

[0095] A heat exchanger according to a first aspect of the present invention is a heat exchanger that liquefies gaseous carbon dioxide by utilizing the cold energy of a low-temperature liquefied gas, and includes a low-temperature flow path having a low-temperature fluid inlet into which the low-temperature liquefied gas is introduced and a low-temperature fluid outlet from which vaporized gas obtained after the low-temperature liquefied gas is vaporized; ２ Inlet and outlet CO2 after liquefaction ２ and a flow path to be liquefied having an outlet, and the low-temperature flow path is configured to ２ Entrance and CO ２ The low-temperature fluid inlet is located at a position corresponding to an intermediate position between the low-temperature fluid inlet and the CO ２ The low-temperature liquefied gas received from the low-temperature fluid inlet is heated and vaporized by circulating the gas while exchanging heat with carbon dioxide flowing through a first predetermined region of the flow path to be liquefied, and the heated vaporized gas is refrigerated by evaporating the CO ２ CO corresponding to the exit ２ The low-temperature fluid is configured to be discharged from the low-temperature fluid outlet after heat exchange with the carbon dioxide flowing through the second predetermined region of the liquefaction target flow path via the outlet-corresponding position.

[0096] According to this configuration, the low-temperature fluid inlet is connected to the CO ２ Entrance and CO ２ The low-temperature liquefied gas flowing in from the low-temperature fluid inlet is heated and then cooled to a temperature corresponding to the midpoint between the low-temperature liquefied gas flowing in from the low-temperature fluid inlet and the CO ２ CO corresponding to the exit ２ By passing through the outlet-corresponding position, it is possible to suppress the solidification of carbon dioxide due to the cold heat of the low-temperature liquefied gas. That is, the point in the low-temperature flow path where the temperature of the low-temperature liquefied gas is lowest is the low-temperature fluid inlet. ２ When placed at a position corresponding to the outlet, ２ The inner surface of the outlet is cooled by the coldest liquefied gas. ２ The wall temperature around the outlet may fall below the solidification temperature of carbon dioxide. ２ When the temperature of the carbon dioxide discharged from the outlet is high, ２ Even if the temperature of the inner surface of the outlet falls below the solidification temperature, the carbon dioxide will not solidify. However, if the temperature of the carbon dioxide being discharged is low (for example, between -40°C and -50°C), the carbon dioxide will solidify. ２ There is a problem with solidification on the inside surface of the outlet.

[0097] This problem is ２ This can be avoided by setting the temperature of the carbon dioxide discharged from the outlet, i.e., the temperature of the liquefied carbon dioxide required by the user, higher, but this limits the temperature range of the liquefied carbon dioxide obtained through the heat exchanger, reducing the utility value of the heat exchanger. ２ By using a high-temperature refrigerant other than the low-temperature liquefied gas only near the outlet, ２ It is possible to control the inner surface temperature of the outlet to a temperature that does not cause solidification of carbon dioxide (for example, a temperature higher than -56°C, but this is not limited to this), but in this case, additional equipment is required to store and circulate the high-temperature refrigerant, which increases costs.

[0098] In contrast, according to the above-described configuration, first, the low-temperature fluid inlet where the low-temperature liquefied gas is at its lowest is connected to the CO ２Entrance and CO ２ By positioning the low-temperature fluid inlet at a position corresponding to the midpoint between the CO ２ Keep away from the exit ２ The temperature drop on the inner surface of the outlet can be minimized, which in turn can prevent the carbon dioxide from solidifying. On the other hand, at the intermediate position of the liquefaction target flow path, the carbon dioxide is cooled by the lowest temperature liquefied gas flowing into the low-temperature fluid inlet. ２ Gas state near the inlet, condensed state in the center, CO ２ Since the gas becomes liquid near the outlet, the heat transfer coefficient of the condensed state at the intermediate position of the liquefaction target flow path is usually ２ The heat transfer coefficient is higher than that of the liquid state near the outlet. Therefore, at the intermediate position of this liquefaction target flow path, ２ The cooling effect of the low-temperature liquefied gas on the wall surface of the flow path is lower than that near the outlet. Therefore, as in the above configuration, locating the low-temperature fluid inlet at the middle position of the flow path to be liquefied is preferable because it reduces the CO ２ This can prevent carbon dioxide from solidifying compared to when it is placed near the outlet.

[0099] The low-temperature liquefied gas flowing in from the low-temperature fluid inlet is heated by passing through the first predetermined area to become a vaporized gas, and the heated vaporized gas is mixed with the CO ２ CO corresponding to the exit ２ By passing through the exit corresponding position, ２ Therefore, the temperature drop of the inner surface of the outlet can be reliably suppressed. ２ This makes it possible to minimize the solidification of carbon dioxide on the inner surface of the outlet.

[0100] In a second aspect of the present invention, in the first aspect, the low-temperature flow path includes a first flow path section that heats the low-temperature liquefied gas received from the low-temperature fluid inlet by performing heat exchange between the low-temperature liquefied gas and carbon dioxide flowing in an intermediate region of the flow path in the flow direction of the liquefaction target flow path in a counterflow or crossflow manner, thereby heating the low-temperature liquefied gas and discharging it as a vaporized gas, and a second flow path section that converts the heated vaporized gas discharged from the first flow path section into the CO ２The flow passage includes a second flow path section that receives vaporized gas from an outlet corresponding position and performs countercurrent heat exchange between the received vaporized gas and carbon dioxide flowing in a downstream region downstream of the intermediate region in the flow path to be liquefied, a third flow path section that receives the vaporized gas after passing through the second flow path section and performs countercurrent heat exchange between the vaporized gas and carbon dioxide flowing in an upstream region upstream of the intermediate region in the flow path to be liquefied, a first connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, and a second connecting flow path section that connects the downstream end of the second flow path section and the upstream end of the third flow path section, and it is preferable that the first specified region is the intermediate region of the flow path to be liquefied and the second specified region is composed of the downstream region and the upstream region of the flow path to be liquefied.

[0101] According to this configuration, the vaporized gas heated in the first flow path is ２ CO corresponding to the exit ２ The low-temperature liquefied gas can be introduced into the second flow path section via the outlet-corresponding position. Therefore, the same effects as those of the first invention can be obtained. Furthermore, with this configuration, the heat exchange between the low-temperature liquefied gas introduced into the low-temperature flow path and the carbon dioxide introduced into the liquefaction target flow path can be achieved by a counterflow method or a combination of a counterflow method and a crossflow method. Therefore, the temperature of the evaporated low-temperature liquefied gas discharged from the heat exchanger can be made higher than when a parallel flow method is used. Therefore, a wide temperature range of the evaporated low-temperature liquefied gas desired by users can be accommodated.

[0102] In a third aspect of the present invention, in the first aspect, the low-temperature flow path includes a first flow path portion configured to heat the low-temperature liquefied gas received from the low-temperature fluid inlet by performing heat exchange between the low-temperature liquefied gas received from the low-temperature fluid inlet and carbon dioxide flowing in an intermediate region of the flow path in the flow direction of the liquefaction target flow path in a counterflow or crossflow manner to form a vaporized gas, and a second flow path portion configured to heat the vaporized gas by performing heat exchange between the low-temperature liquefied gas received from the low-temperature fluid inlet and carbon dioxide flowing in an intermediate region of the flow path in the flow direction of the liquefaction target flow path in a counterflow or crossflow manner to form a vaporized gas. ２The gas passage has a second flow path section that receives vaporized gas from an outlet corresponding position and performs countercurrent heat exchange between the received vaporized gas and carbon dioxide flowing throughout the entire area of ​​the flow path length of the flow path to be liquefied, and a connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, and it is preferable that the first specified area consists of the intermediate area of ​​the flow path to be liquefied and the second specified area consists of the entire area of ​​the flow path to be liquefied.

[0103] According to this configuration, the vaporized gas heated in the first flow path is ２ The second flow path section can be configured to allow the low-temperature liquefied gas introduced into the low-temperature flow path and the carbon dioxide introduced into the liquefaction-target flow path to flow into the second flow path section. This achieves the same advantageous effects as the first aspect of the present invention. Furthermore, with this configuration, the heat exchange between the low-temperature liquefied gas introduced into the low-temperature flow path and the carbon dioxide introduced into the liquefaction-target flow path can be achieved using a counterflow method or a combination of a counterflow method and a crossflow method. This allows the temperature of the evaporated low-temperature liquefied gas discharged from the heat exchanger to be higher than when a parallel flow method is used. This allows a wider temperature range of the evaporated low-temperature liquefied gas desired by users to be accommodated. Furthermore, with this configuration, heat exchange occurs between the evaporated gas flowing through the second flow path section and the carbon dioxide flowing throughout the entire length of the liquefaction-target flow path, eliminating the need to extend the second flow path section to the outside of the heat exchanger midway. This allows the heat exchange flow paths to be concentrated within the heat exchanger as much as possible, reducing the number of connecting pipes.

[0104] In a fourth aspect of the present invention, in the first aspect, the low-temperature liquefied gas received from the low-temperature fluid inlet is liquefied from the intermediate position in the liquefaction target flow path to the CO ２The liquefaction target flow path has a first flow path section that heats the vaporized gas by performing parallel flow heat exchange with carbon dioxide flowing through an outlet side region leading to the outlet, and then discharges the vaporized gas as the vaporized gas; a second flow path section that receives the vaporized gas discharged from the first flow path section and performs counter flow heat exchange with carbon dioxide flowing through an inlet side region upstream of the outlet side region in the liquefaction target flow path; and a connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, and it is preferable that the first specified region consists of the outlet side region of the liquefaction target flow path and the second specified region consists of the inlet side region of the liquefaction target flow path.

[0105] According to this configuration, the vaporized gas heated in the first flow path is ２ CO corresponding to the exit ２ The low-temperature liquefied gas can be introduced into the second flow path section via the outlet-corresponding position. Therefore, the same effects as those of the first invention can be obtained. Furthermore, with the above configuration, the heat exchange method between the low-temperature liquefied gas introduced into the low-temperature flow path and the carbon dioxide introduced into the flow path to be liquefied can be realized by combining the parallel flow method and the counter flow method. Therefore, the temperature of the low-temperature liquefied gas after evaporation discharged from the heat exchanger can be made higher than when the parallel flow method is adopted over the entire flow path. Therefore, it is possible to widely accommodate the temperature range of the low-temperature liquefied gas after evaporation that is desired by the user. Furthermore, by adopting the parallel flow method for the first flow path section, the CO ２ The flow path configuration leading to the outlet corresponding position can be simplified, thereby avoiding the problems of increased costs and increased assembly steps due to a complicated flow path configuration.

[0106] In a fifth aspect of the present invention, in the first aspect, the low-temperature flow path is configured to liquefy the low-temperature liquefied gas received from the low-temperature fluid inlet from the intermediate position of the flow path to be liquefied. ２ The first flow path section discharges the vaporized gas, and the second flow path section receives the vaporized gas discharged from the first flow path section and exchanges heat between the vaporized gas and the carbon dioxide flowing through the outlet side region leading to the outlet in a parallel flow manner. ２ Exit CO ２The liquefaction target flow path preferably has a second flow path section that performs countercurrent heat exchange with carbon dioxide flowing through the entire area up to the inlet and then discharges the carbon dioxide, and a connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, and the first predetermined area preferably consists of the outlet side area of ​​the liquefaction target flow path, and the second predetermined area preferably consists of the entire area of ​​the liquefaction target flow path.

[0107] According to this configuration, the vaporized gas heated in the first flow path is ２ CO corresponding to the exit ２ The low-temperature liquefied gas can be introduced into the second flow path section via the outlet-corresponding position. Therefore, the same effects as those of the first invention can be obtained. Furthermore, with the above configuration, the heat exchange method between the low-temperature liquefied gas introduced into the low-temperature flow path and the carbon dioxide introduced into the flow path to be liquefied can be realized by combining the parallel flow method and the counter flow method. Therefore, the temperature of the low-temperature liquefied gas after evaporation discharged from the heat exchanger can be made higher than when the parallel flow method is adopted over the entire flow path. Therefore, it is possible to widely accommodate the temperature range of the low-temperature liquefied gas after evaporation that is desired by the user. Furthermore, by adopting the parallel flow method for the first flow path section, the CO ２ The flow path configuration leading to the outlet corresponding position can be simplified.

[0108] Furthermore, with this configuration, heat exchange occurs between the heated vaporized gas that has flowed into the second flow path section and the carbon dioxide that flows through the entire length of the flow path to be liquefied, so there is no need to extend the second flow path section to the outside of the heat exchanger along the way. This makes it possible to concentrate the heat exchange flow paths within the heat exchanger as much as possible and reduce the number of connecting pipes.

[0109] A sixth aspect of the present invention is a heat exchange system including the heat exchanger according to the second, third or fifth aspect of the present invention, further comprising: a supply flow path connected to the low-temperature fluid inlet and guiding a low-temperature liquefied gas supplied from an outside to the low-temperature fluid inlet; ２It is preferable that the device further comprises a bypass flow path connected to a predetermined location upstream of the outlet corresponding position, and a bypass valve provided in the bypass flow path.

[0110] According to this configuration, the low-temperature liquefied gas that has passed through the bypass flow path and the vaporized gas discharged from the first flow path unit are joined together, and CO is released at a temperature lower than that of the vaporized gas discharged from the first flow path unit. ２ Here, since the bypass flow path is provided with a bypass valve, the flow rate ratio of the low-temperature liquefied gas passing through the bypass flow path and the vaporized gas discharged from the first flow path portion can be adjusted by controlling the opening degree of the bypass valve, thereby reducing CO ２ The temperature of the mixed fluid (low-temperature fluid that cools the carbon dioxide) supplied to the liquefaction position can be easily controlled, and as a result, the temperature of the liquefied carbon dioxide discharged from the heat exchanger can be easily controlled.

[0111] A seventh invention is the sixth invention, which further comprises a temperature detection unit that detects the temperature of a mixed fluid of the vaporized gas vaporized in the first flow path section and the low-temperature liquefied gas that has passed through the bypass flow path, or a temperature correlated to that temperature, and a control unit that controls the bypass valve based on the temperature detected by the temperature detection unit, and the control unit is preferably configured to perform bypass valve control that controls the bypass valve so that the temperature detected by the temperature detection unit becomes a predetermined target temperature.

[0112] According to this configuration, the bypass valve is automatically controlled by the control unit, so that the temperature of the mixed fluid can be more easily controlled than when the bypass valve is opened and closed manually.

[0113] The eighth invention is, in the seventh invention, preferably, the predetermined target temperature is a temperature that is set in advance so that the temperature of the liquefied carbon dioxide discharged from the heat exchanger becomes a predetermined required temperature and so that the carbon dioxide does not solidify on the inner surface of the liquefaction target flow path.

[0114] According to this configuration, the temperature of the liquefied carbon dioxide discharged from the liquefaction target flow path can be controlled to a predetermined required temperature, while solidification of the carbon dioxide within the liquefaction target flow path can be reliably prevented.

[0115] A ninth aspect of the present invention is a heat exchange system including the heat exchanger according to the fourth aspect of the present invention, the heat exchange system including: a supply flow path connected to the low-temperature fluid inlet and guiding a low-temperature liquefied gas supplied from an outside to the low-temperature fluid inlet; ２ It is preferable that the device further comprises a bypass flow path connected to a predetermined location downstream of the outlet corresponding position, and a bypass valve provided in the bypass flow path.

[0116] According to this configuration, the bypass flow path branches off from the supply flow path, bypasses the first flow path portion, and then ２ Therefore, for example, by increasing the flow rate of the low-temperature liquefied gas flowing through the bypass flow path, the flow rate of the low-temperature liquefied gas flowing from the supply flow path to the first flow path portion will decrease, thereby reducing the CO ２ The temperature of the vaporized gas at the outlet-corresponding position (the downstream end position of the first flow path section) can be increased. Conversely, for example, by reducing the flow rate of the low-temperature liquefied gas flowing through the bypass flow path, the flow rate of the low-temperature liquefied gas flowing from the supply flow path to the first flow path section increases, thereby reducing the CO ２ The temperature of the vaporized gas at the outlet-corresponding position (the downstream end position of the first flow path portion) can be reduced. ２ The temperature of the vaporized gas at the outlet position can be easily controlled, and as a result, the temperature of the liquefied carbon dioxide discharged from the heat exchanger can be easily controlled.

[0117] The tenth invention is the ninth invention, further comprising a temperature detection unit that detects the temperature of the vaporized gas after being vaporized in the first flow path section and before it merges with the low-temperature liquefied gas that has passed through the bypass flow path, or a temperature correlated to that temperature, and a control unit that controls the bypass valve based on the temperature detected by the temperature detection unit, and it is preferable that the control unit is configured to perform bypass valve control that controls the bypass valve so that the temperature detected by the temperature detection unit becomes a predetermined target temperature.

[0118] According to this configuration, the bypass valve is automatically controlled by the control unit, so that the temperature of the mixed fluid can be more easily controlled than when the bypass valve is opened and closed manually.

[0119] In the 11th invention, in the invention of claim 10, it is preferable that the predetermined target temperature is a temperature that is set in advance so that the temperature of the liquefied carbon dioxide discharged from the heat exchanger becomes a predetermined required temperature and so that the carbon dioxide does not solidify on the inner surface of the liquefaction target flow path.

[0120] According to this configuration, the temperature of the liquefied carbon dioxide discharged from the liquefaction target flow path can be controlled to a predetermined required temperature, while solidification of the carbon dioxide within the liquefaction target flow path can be reliably prevented.

Claims

1. A heat exchanger that liquefies gaseous carbon dioxide using the cold energy of a low-temperature liquefied gas, comprising: a low-temperature flow path having a low-temperature fluid inlet into which the low-temperature liquefied gas is introduced and a low-temperature fluid outlet from which the vaporized gas after the low-temperature liquefied gas is vaporized is discharged; ２ Inlet and outlet CO2 after liquefaction ２ and a flow path to be liquefied having an outlet, and the low-temperature flow path is ２ Inlet and CO ２ The low-temperature fluid inlet is located at a position corresponding to an intermediate position between the low-temperature fluid inlet and the CO ２ the low-temperature liquefied gas received from the low-temperature fluid inlet is circulated while exchanging heat with carbon dioxide flowing through a first predetermined region of the flow path to be liquefied, thereby heating the low-temperature liquefied gas to form a vaporized gas, and the heated vaporized gas is circulated through the CO ２ CO corresponding to the exit ２ a heat exchanger configured to exchange heat with carbon dioxide flowing through a second predetermined region of the liquefaction target flow path via an outlet corresponding position, and then discharge the low-temperature fluid from the low-temperature fluid outlet.

2. A heat exchanger according to claim 1, wherein the low-temperature flow path comprises a first flow path section that heats the low-temperature liquefied gas received from the low-temperature fluid inlet by performing heat exchange in a counterflow or crossflow manner with carbon dioxide flowing through an intermediate region in the flow path length direction of the flow path to be liquefied, thereby heating the low-temperature liquefied gas and discharging it as a vaporized gas; ２ a second flow path section that receives vaporized gas from an outlet corresponding position and performs countercurrent heat exchange between the received vaporized gas and carbon dioxide flowing in a downstream region downstream of the intermediate region in the flow path to be liquefied; a third flow path section that receives the vaporized gas after passing through the second flow path section and performs countercurrent heat exchange between the vaporized gas and carbon dioxide flowing in an upstream region upstream of the intermediate region in the flow path to be liquefied; a first connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section; and a second connecting flow path section that connects the downstream end of the second flow path section and the upstream end of the third flow path section, wherein the first predetermined region is the intermediate region of the flow path to be liquefied, and the second predetermined region is constituted by the downstream region and the upstream region of the flow path to be liquefied.

3. A heat exchanger according to claim 1, wherein the low-temperature flow path comprises a first flow path portion configured to heat the low-temperature liquefied gas received from the low-temperature fluid inlet by performing heat exchange in a counterflow or crossflow manner with carbon dioxide flowing in an intermediate region in the flow path length direction of the flow path to be liquefied, thereby to form a vaporized gas; ２ a second flow path section that receives vaporized gas from an outlet corresponding position and performs countercurrent heat exchange between the received vaporized gas and carbon dioxide flowing through the flow path to be liquefied over the entire area in the flow path length direction of the flow path to be liquefied; and a connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, wherein the first predetermined area consists of the intermediate area of ​​the flow path to be liquefied, and the second predetermined area consists of the entire area of ​​the flow path to be liquefied.

4. A heat exchanger according to claim 1, wherein the low-temperature flow path is configured to transfer the low-temperature liquefied gas received from the low-temperature fluid inlet from the intermediate position in the flow path to the CO ２ a first flow path section that performs heat exchange in a parallel flow manner with carbon dioxide flowing through an outlet side region leading to an outlet, thereby heating the vaporized gas and discharging it as the vaporized gas; a second flow path section that receives the vaporized gas discharged from the first flow path section and performs heat exchange in a counter flow manner with carbon dioxide flowing through an inlet side region upstream of the outlet side region in the flow path to be liquefied; and a connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, wherein the first predetermined region consists of the outlet side region of the flow path to be liquefied, and the second predetermined region consists of the inlet side region of the flow path to be liquefied.

5. A heat exchanger according to claim 1, wherein the low-temperature flow path refrigerates the low-temperature liquefied gas received from the low-temperature fluid inlet from the intermediate position of the flow path to be liquefied to CO ２ a first flow path section that receives the vaporized gas discharged from the first flow path section and discharges the vaporized gas into the CO liquefaction target flow path by performing heat exchange in a parallel flow manner with the carbon dioxide flowing through the outlet side region leading to the outlet; ２ The CO ２ a second flow path section that performs countercurrent heat exchange with carbon dioxide flowing through the entire area up to the inlet and then discharges the carbon dioxide; and a connecting flow path section that connects the downstream end of the first flow path section and the upstream end of the second flow path section, wherein the first predetermined area consists of the outlet side area of ​​the flow path to be liquefied, and the second predetermined area consists of the entire area of ​​the flow path to be liquefied.

6. A heat exchange system equipped with the heat exchanger according to claim 2, 3 or 5, comprising: a supply flow path connected to the low-temperature fluid inlet and guiding a low-temperature liquefied gas supplied from an external source to the low-temperature fluid inlet; and a flow path branching from the supply flow path and bypassing the first flow path portion of the low-temperature flow path to reduce the CO ２ A heat exchange system comprising: a bypass flow path connected to a predetermined portion upstream of an outlet corresponding position; and a bypass valve provided in the bypass flow path.

7. A heat exchange system according to claim 6, further comprising a temperature detection unit that detects the temperature of a mixed fluid of the vaporized gas vaporized in the first flow path section and the low-temperature liquefied gas that has passed through the bypass flow path, or a temperature correlated to that temperature, and a control unit that controls the bypass valve based on the temperature detected by the temperature detection unit, wherein the control unit is configured to execute bypass valve control that controls the bypass valve so that the temperature detected by the temperature detection unit becomes a predetermined target temperature.

8. A heat exchange system as described in claim 7, wherein the predetermined target temperature is a temperature that is set in advance so that the temperature of the liquefied carbon dioxide discharged from the heat exchanger becomes a predetermined required temperature and so that the carbon dioxide does not solidify on the inner surface of the flow path to be liquefied.

9. A heat exchange system equipped with the heat exchanger according to claim 4, comprising: a supply flow path connected to the low-temperature fluid inlet and guiding a low-temperature liquefied gas supplied from an external source to the low-temperature fluid inlet; and a flow path branching from the supply flow path and bypassing the first flow path portion of the low-temperature flow path to reduce the CO ２ A heat exchange system comprising: a bypass flow path connected to a predetermined portion downstream of an outlet corresponding position; and a bypass valve provided in the bypass flow path.

10. A heat exchange system as claimed in claim 9, further comprising a temperature detection unit that detects the temperature of the vaporized gas after being vaporized in the first flow path section and before it merges with the low-temperature liquefied gas that has passed through the bypass flow path, or a temperature correlated to that temperature, and a control unit that controls the bypass valve based on the temperature detected by the temperature detection unit, wherein the control unit is configured to execute bypass valve control that controls the bypass valve so that the temperature detected by the temperature detection unit becomes a predetermined target temperature.

11. A heat exchange system according to claim 10, wherein the predetermined target temperature is a temperature that is set in advance so that the temperature of the liquefied carbon dioxide discharged from the heat exchanger reaches a predetermined required temperature and so that the carbon dioxide does not solidify on the inner surface of the flow path to be liquefied.

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