LIQUID HYDROGEN VAPORIZER, AND GENERATION METHOD FOR GENERATING HYDROGEN

Abstract

 A liquid hydrogen vaporizer generates hydrogen in a gaseous state or a supercritical state from liquid hydrogen. The liquid hydrogen vaporizer includes: an auxiliary heat exchanger that heats liquid hydrogen by heat exchange with a heating fluid having a freezing point lower than the freezing point of seawater or industrial water; and an open rack type main heat exchanger including heat transfer tubes that allows hydrogen to flow in and a trough that allows seawater or industrial water to flow down onto the outer surfaces of the heat transfer tubes. The main heat exchanger heats hydrogen flowing out from the auxiliary heat exchanger by heat exchange with seawater or industrial water.

Description

Technical Field

[0001] The present invention relates to a liquid hydrogen vaporizer and a generation method for generating hydrogen.

Background Art

[0002] Conventionally, in thermal power plants and the like that use natural gas as fuel, open rack type gas vaporizers (ORV) are known, which vaporize low-temperature liquefied gases such as liquefied natural gas (LNG) by using seawater as a heating fluid. Patent Literature 1 discloses an open rack type vaporizer for vaporizing a low-temperature liquefied gas by heat exchange with a heating fluid. As shown in FIG. 6, the open rack type vaporizer 600 includes heat exchange panels 612 and 622 in which a large number of heat transfer tubes 614 and 624 are provided and a heat source medium supply unit provided with a trough (not shown) for supplying seawater to the outer surfaces of the heat transfer tubes 614 and 624. The vaporizer vaporizes the liquefied natural gas in the heat transfer tubes 614 and 624 by causing liquefied natural gas flowing in the heat transfer tubes to exchange heat with seawater flowing down the outer surface of the heat transfer tubes 614 and 624.

[0003] At thermal power plants and the like, for the purpose of reducing carbon dioxide emissions, it has been considered to use liquid hydrogen as an alternative fuel for liquefied natural gas. In this case, like liquefied natural gas, liquid hydrogen is heated to room temperature and then supplied to power generation apparatuses. However, the temperature of liquid hydrogen (-253°C) is lower than the temperature of liquefied natural gas (-162°C). Therefore, if liquid hydrogen is vaporized by using the open rack type vaporizer suited for liquefied natural gas, the thermal stress occurring on the heat transfer tubes is likely to increase, and icing of the heating fluid on the outer surfaces of the heat transfer tubes is likely to occur.

Citation List

Patent Literature

[0004] Patent Literature 1: JP 2017-40296 A

Summary of Invention

[0005] An object of the present invention is to suppress icing on the heat transfer tubes while alleviating the thermal stress on the heat transfer tubes of the open rack type heat exchanger in the liquid hydrogen vaporizer.

[0006] A liquid hydrogen vaporizer according to the present disclosure is a liquid hydrogen vaporizer for generating hydrogen in a gaseous state or a supercritical state from liquid hydrogen. The liquid hydrogen vaporizer includes: an auxiliary heat exchanger configured to heat liquid hydrogen by heat exchange with a heating fluid having a freezing point lower than a freezing point of seawater or industrial water; and an open rack type main heat exchanger including heat transfer tubes for allowing hydrogen to flow in and a trough configured to supply seawater or industrial water to outer surfaces of the heat transfer tubes, the main heat exchanger heating the hydrogen flowing out from the auxiliary heat exchanger by heat exchange with seawater or industrial water.

[0007] The liquid hydrogen vaporizer according to the present disclosure is a liquid hydrogen vaporizer for generating hydrogen in a gaseous state or a supercritical state from liquid hydrogen. The liquid hydrogen vaporizer includes: an open rack type main heat exchanger including heat transfer tubes configured to allow the hydrogen to flow in and a trough configured to supply seawater or industrial water to outer surfaces of the heat transfer tubes, the main heat exchanger heating the hydrogen in the heat transfer tubes by heat exchange with seawater or industrial water; a main channel connected to the main heat exchanger; a diversion channel configured to divert the liquid hydrogen supplied from outside, the diversion channel including: a first diversion channel configured to allow a first part of the liquid hydrogen supplied from outside to flow in; and a second diversion channel configured to allow a second part of the liquid hydrogen supplied from outside to flow in; and an auxiliary heat exchanger disposed on the first diversion channel and configured to heat the liquid hydrogen flowing through the first diversion channel by heat exchange with a heating fluid. The diversion channel is connected to the main channel to allow the heated hydrogen flowing through the first diversion channel and the liquid hydrogen flowing through the second diversion channel to merge and flow into the main channel. Magnitude of a heat load of the heating fluid required to heat the liquid hydrogen in the auxiliary heat exchanger is smaller than magnitude of a heat load of seawater or industrial water required to heat the hydrogen in the main heat exchanger.

[0008] A method for generating hydrogen according to the present disclosure is a method for generating hydrogen in a gaseous state or a supercritical state by heating liquid hydrogen. The method includes: a first heating step of heating liquid hydrogen supplied from outside by heat exchange with a heating fluid having a freezing point lower than a freezing point of seawater or industrial water in an auxiliary heat exchanger; and a second heating step of allowing hydrogen flowing out from the auxiliary heat exchanger to flow into heat transfer tubes of a main heat exchanger, and heating the hydrogen in the heat transfer tubes to a predetermined temperature by heat exchange with seawater or industrial water.

[0009] A method for generating hydrogen according to the present disclosure is a method for generating hydrogen in a gaseous state or a supercritical state by heating liquid hydrogen. The method includes: a diversion step of diverting liquid hydrogen supplied from outside to a first diversion channel and a second diversion channel; a first heating step of heating the liquid hydrogen in the first diversion channel by heat exchange with a heating fluid in an auxiliary heat exchanger provided on the first diversion channel; a merging step of allowing hydrogen from the first diversion channel and the liquid hydrogen from the second diversion channel to merge and flow into a main channel; and a second heating step of allowing the hydrogen in the main channel to flow into heat transfer tubes of a main heat exchanger and heating the hydrogen in the heat transfer tubes to a predetermined temperature by heat exchange with seawater or industrial water. Magnitude of a heat load of a heating fluid for heating the liquid hydrogen in the first heating step is smaller than magnitude of a heat load of seawater or industrial water for heating the hydrogen in the second heating step.

Brief Description of Drawings

[0010] 

FIG. 1 is a schematic diagram of a liquid hydrogen vaporizer according to a first embodiment.

FIG. 2 is a schematic diagram of the liquid hydrogen vaporizer according to a modification of the first embodiment.

FIG. 3 is a schematic diagram of a liquid hydrogen vaporizer according to a second embodiment.

FIG. 4 is a schematic diagram of the liquid hydrogen vaporizer according to a modification of the second embodiment.

FIG. 5 is a schematic diagram of the liquid hydrogen vaporizer according to a modification of the second embodiment.

FIG. 6 is a schematic diagram of a part of a conventional vaporizer for vaporizing liquefied natural gas.

Description of Embodiments

[0011] Embodiments will be described below with reference to the accompanying drawings. Note that the embodiments below are one example embodying the present invention, and are not intended to limit the technical scope of the present invention.

(First embodiment)

[0012] A liquid hydrogen vaporizer 100 according to the first embodiment is an apparatus for heating liquid hydrogen to generate hydrogen in a gaseous state or a supercritical state by using a first heat source fluid and a second heat source fluid. The liquid hydrogen vaporizer 100 is also simply referred to as a "vaporizer 100." The vaporizer 100 includes, as shown in FIG. 1, an auxiliary heat exchanger 110, a main heat exchanger 150 disposed downstream of the auxiliary heat exchanger 110, and a connection channel 140 connecting the auxiliary heat exchanger 110 with the main heat exchanger 150.

[0013] The auxiliary heat exchanger 110 includes an intermediate fluid type heat exchanger configured to heat liquid hydrogen by using an intermediate fluid M1 that mediates heat exchange between the liquid hydrogen and the first heat source fluid. That is, in the first embodiment, the intermediate fluid M1 functions as a heating fluid for heating the liquid hydrogen. For the first heat source fluid, seawater or industrial water is used. For the intermediate fluid M1, a fluid that has a freezing point lower than the freezing point of seawater or industrial water and has a boiling point lower than the temperature of seawater or industrial water (for example, propane) is used.

[0014] The auxiliary heat exchanger 110 includes an intermediate fluid evaporation unit E1 and a hydrogen heating unit E2, the intermediate fluid evaporation unit E1 being for evaporating the liquid intermediate fluid M1 by heat exchange with the first heat source fluid, and the hydrogen heating unit E2 being for vaporizing liquid hydrogen by heat exchange with the gaseous intermediate fluid M1. The intermediate fluid evaporation unit E1 and the hydrogen heating unit E2 share one hollow casing 112. Therefore, within the casing 112, the intermediate fluid M1 goes back and forth between the intermediate fluid evaporation unit E1 and the hydrogen heating unit E2. The casing 112 has a horizontally long shape and includes one pair of side walls 116 and 118 that constitute the casing 112. The liquid intermediate fluid M1 is stored in a lower portion of the casing 112. Note that the intermediate fluid evaporation unit E1 and the hydrogen heating unit E2 do not need to share one casing 112, but may have a configuration in which separate casings (not shown) are included and both of the casings are connected to each other by a tube through which the intermediate fluid M1 flows. In this case, the above configuration is not limited to the configuration in which the hydrogen heating unit E2 is located above the intermediate fluid evaporation unit E1.

[0015] The intermediate fluid evaporation unit E1 includes an inlet chamber 134 adjacent to one side wall 116, an outlet chamber 136 adjacent to the other side wall 118, and a large number of heat transfer tubes 132 bridged between the inlet chamber 134 and the outlet chamber 136. Each heat transfer tube 132 extends in one direction and is arranged below the liquid level of the liquid intermediate fluid M1 in the casing 112. The inlet chamber 134 is connected to an introduction tube equipped with a pump and the like (not shown). The first heat source fluid supplied to the inlet chamber 134 from outside the vaporizer 100 flows to the outlet chamber 136 through the plurality of heat transfer tubes 132. The outlet chamber 136 is connected to a discharge tube (not shown) for discharging the first heat source fluid in the outlet chamber 136 from the vaporizer 100.

[0016] The heat transfer tubes 132 of the intermediate fluid evaporation unit E1 are arranged to pass through the liquid intermediate fluid M1. With this arrangement, heat exchange is performed between the first heat source fluid flowing through the heat transfer tubes 132 and the liquid intermediate fluid M1.

[0017] The hydrogen heating unit E2 includes an inlet chamber 124, an outlet chamber 126, and a large number of heat transfer tubes 122 that communicate between the inlet chamber 124 and the outlet chamber 126. The inlet chamber 124 is connected to a supply tube (not shown) that allows liquid hydrogen to flow in from outside. The inlet chamber 124 is located above the outlet chamber 136 of the intermediate fluid evaporation unit E1, but its placement is not limited to this position. Each heat transfer tube 122 is formed into a substantially U-shape, and the outlet chamber 126 is adjacent to the upper side of the inlet chamber 124. Note that the heat transfer tube 122 does not need to be formed in a U-shape, and may include a straight tube, for example. In this case, the inlet chamber 124 and the outlet chamber 126 are not vertically adjacent, but are disposed such that one chamber is adjacent to one of the opposing side walls 116 and 118, and the other chamber is adjacent to the other of the opposing side walls 116 and 118. Each heat transfer tube 122 is arranged above the liquid level of the liquid intermediate fluid M1 stored in the casing 112. That is, each heat transfer tube 122 is located above the heat transfer tubes 132.

[0018] The outlet chamber 126 is connected to the connection channel 140 for allowing hydrogen flowing out from the auxiliary heat exchanger 110 to flow into the main heat exchanger 150.

[0019] Heat exchange is performed between the liquid hydrogen in the heat transfer tubes 122 and the gaseous intermediate fluid M1. The hydrogen vaporized by heat exchange with the gaseous intermediate fluid M1 flows into the connection channel 140 through the outlet chamber 126. The intermediate fluid M1 liquefied by heat exchange with the liquid hydrogen flows down to the intermediate fluid evaporation unit E1 side in the casing 112.

[0020] In the hydrogen heating unit E2, the liquid hydrogen in the heat transfer tubes 122 is heated to a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure by heat exchange with the gaseous intermediate fluid M1. Note that the hydrogen heating unit E2 may be configured to heat the liquid hydrogen in the heat transfer tubes 122 to a predetermined temperature equal to or lower than the boiling point of the liquefied natural gas under normal pressure. The hydrogen in a gaseous state or a supercritical state heated in the auxiliary heat exchanger 110 flows into the main heat exchanger 150 through the connection channel 140.

[0021] The main heat exchanger 150 is an open rack type heat exchanger configured to heat hydrogen by using seawater or industrial water as the second heat source fluid. The main heat exchanger 150 includes a plurality of heat transfer tube panels 160 and a heat source fluid supply unit 170 for supplying the second heat source fluid to each heat transfer tube panel 160.

[0022] Each heat transfer tube panel 160 includes a large number of heat transfer tubes 166 for distributing hydrogen (indicated by the dashed arrows in FIG. 1), lower headers 162 connected to the lower end of each heat transfer tube 166, and upper headers 164 connected to the upper end of each heat transfer tube 166. These heat transfer tubes 166 extend in the vertical direction and are arranged in alignment on a vertical plane. For a material of each heat transfer tube 166, for example, a metal material having high thermal conductivity is used, such as aluminum or aluminum alloy.

[0023] Hydrogen flowing into each lower header 162 is distributed to the large number of heat transfer tubes 166 each connected to the lower header 162. That is, in each heat transfer tube 166, hydrogen in a gaseous state or a supercritical state flows from below upward. In each upper header 164, hydrogen from each heat transfer tube 166 is merged.

[0024] The heat source fluid supply unit 170 includes troughs 171 disposed near the upper end of the plurality of heat transfer tube panels 160. The troughs 171 are provided for each heat transfer tube panel 160 so as to be adjacent to each heat transfer tube panel 160. Each trough 171 has a long shape in the direction in which the heat transfer tubes 166 are arrange and is shaped like a container with an open upper surface. A header 172 for allowing the second heat source fluid to flow in from outside is connected to each trough 171. The heat source fluid that has flowed into the troughs 171 through the header 172 overflows to the outside of the troughs 171 from an opening on the upper surface of the troughs 171.

[0025] In the main heat exchanger 150, the second heat source fluid overflowing from each trough 171 flows down along the outer surface of the large number of heat transfer tubes 166 of each heat transfer tube panel 160. With this configuration, heat exchange is performed between the hydrogen inside the heat transfer tubes 166 and the second heat source fluid outside the heat transfer tubes 166. In the main heat exchanger 150, the hydrogen is heated to a room temperature or a predetermined temperature by heat exchange with the second heat source fluid. The hydrogen is derived from the main heat exchanger 150 through the upper headers 164 and supplied to external hydrogen gas demand destinations. The second heat source fluid that has flowed down along the outer surface of the heat transfer tubes 166 is discharged outside the main heat exchanger 150 through a drainage channel or the like (not shown).

(Operational action)

[0026] In the auxiliary heat exchanger 110 of the liquid hydrogen vaporizer 100, liquid hydrogen is supplied to the inlet chamber 124 from an external liquid hydrogen supply source, and the first heat source fluid (seawater or industrial water) is supplied to the inlet chamber 134 of the intermediate fluid evaporation unit E1 from an external first heat source fluid supply source. Meanwhile, in the main heat exchanger 150, the second heat source fluid (seawater or industrial water) is supplied from an external second heat source fluid supply source to the troughs 171 of the heat source fluid supply unit 170.

[0027] The first heat source fluid supplied to the inlet chamber 134 of the intermediate fluid evaporation unit E1 flows to the outlet chamber 136 through the heat transfer tubes 132, and then is discharged to outside. At this time, the first heat source fluid heats the liquid intermediate fluid M1 stored in the casing 112 while flowing through the heat transfer tubes 132. This evaporates at least a portion of the liquid intermediate fluid M1.

[0028] The liquid hydrogen supplied to the inlet chamber 124 of the hydrogen heating unit E2 flows into the heat transfer tubes 122. At this time, the gaseous intermediate fluid M1 in the casing 112 heats the liquid hydrogen in the heat transfer tubes 122 to a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure (first heating step). Note that the gaseous intermediate fluid M1 in the hydrogen heating unit E2 may heat the liquid hydrogen in the heat transfer tubes 122 to a predetermined temperature equal to or lower than the boiling point of the liquefied natural gas under normal pressure. The heated hydrogen in a gaseous state or a supercritical state flows from the outlet chamber 126 into the connection channel 140. Meanwhile, the gaseous intermediate fluid M1 cooled by the liquid hydrogen in the heat transfer tubes 122 condenses and liquefies, flows down in the interior space within the casing 112, and returns to the intermediate fluid evaporation unit E1.

[0029] The hydrogen in a gaseous state or a supercritical state that has flowed into the connection channel 140 is supplied into the heat transfer tubes 166 through the lower headers 162 of the main heat exchanger 150. The hydrogen in the heat transfer tubes 166 is heated by the second heat source fluid supplied from the troughs 171 and flowing down along the outer surface of the heat transfer tubes 166, whereby the hydrogen in the heat transfer tubes 166 is heated to a room temperature or a predetermined temperature (second heating step). The hydrogen in a gaseous state or a supercritical state heated to a room temperature or a predetermined temperature is derived to an external hydrogen gas demand destination through the upper headers 164.

[0030] In the vaporizer 100 configured in this way, the auxiliary heat exchanger 110 is provided to preheat the liquid hydrogen as a preceding stage of the main heat exchanger 150, allowing the temperature of the hydrogen flowing into the main heat exchanger 150 to be higher than the temperature of the liquid hydrogen. Therefore, the main heat exchanger 150 can suppress icing on the outer surface of the heat transfer tubes 166 while alleviating the thermal stress applied to the heat transfer tubes 166. Furthermore, by using a fluid having a freezing point lower than the freezing point of seawater or industrial water for the intermediate fluid M1 of the auxiliary heat exchanger 110, icing on the outer surface of the heat transfer tubes 122 of the auxiliary heat exchanger 110 can also be suppressed.

[0031] In the present embodiment, the liquid hydrogen from outside is heated in the auxiliary heat exchanger 110, allowing hydrogen having a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure to be introduced into the main heat exchanger 150. Therefore, the existing open rack type vaporizer for vaporizing liquefied natural gas can also be used as the main heat exchanger 150 of the vaporizer 100. In this case, the introduction cost of the vaporizer 100 can be reduced. The vaporizer 100 includes the auxiliary heat exchanger 110 and the main heat exchanger 150 as separate devices, making it possible to perform maintenance of each device more easily.

(Modification of first embodiment)

[0032] A modification of the first embodiment will be described with reference to FIG. 2. The vaporizer 100 of the first embodiment may be configured such that the auxiliary heat exchanger is a microchannel type heat exchanger in which a large number of fine channels are formed, instead of the intermediate fluid type heat exchanger. The microchannel type heat exchanger is a heat exchanger including a laminate in which a plurality of first plates and a plurality of second plates are stacked, and is a heat exchanger configured to exchange heat between a high-temperature fluid flowing through a high-temperature channel formed in the first plates and a low-temperature fluid flowing through a low-temperature channel formed in the second plates.

[0033] In an auxiliary heat exchanger 210 including the microchannel type heat exchanger, the first heat source fluid, which is a higher-temperature fluid, and the liquid hydrogen, which is a lower-temperature fluid, exchange heat. The first heat source fluid is a heating fluid for heating the liquid hydrogen. For the first heat source fluid, a fluid having a freezing point lower than the freezing point of seawater or industrial water and having a boiling point lower than the temperature of seawater or industrial water (for example, propane) is used.

[0034] The auxiliary heat exchanger 210 includes a laminate 212, an inlet header 216 and an outlet header 218 provided on side surfaces of the laminate 212, and an inlet header 226 provided on the lower surface of the laminate 212 and an outlet header 228 provided on the upper surface of the laminate 212. In the high-temperature plates, a high-temperature channel 214 is formed to meander from the inlet header 216 to the outlet header 218 (shown by solid arrows in FIG. 2). The first heat source fluid supplied from outside flows through the high-temperature channel 214 from the inlet header 216 to the outlet header 218. In the low-temperature plates, a plurality of low-temperature channels 224 extending in one direction from the inlet header 226 to the outlet header 228 is formed (shown by dashed arrows in FIG. 2). The liquid hydrogen supplied from an external liquid hydrogen supply source flows through the plurality of low-temperature channels 224 from the inlet header 226 to the outlet header 228. At this time, heat exchange is performed between the first heat source fluid in the high-temperature channel 214 and the liquid hydrogen in the low-temperature channel 224. As a result, the liquid hydrogen in the low-temperature channel 224 is heated to a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure, becomes a gaseous state or a supercritical state, and flows out to a connection channel 240 from the outlet header 228. The first heat source fluid in the low-temperature channel 224 cooled by the liquid hydrogen is discharged from the outlet header 218 to outside. Note that the liquid hydrogen in the low-temperature channel 224 may be heated to a predetermined temperature equal to or lower than the boiling point of the liquefied natural gas under normal pressure. In the illustrated example, the high-temperature channel 214 is formed to meander, and the low-temperature channel 224 is formed to extend in one direction, but the configuration is not limited to this example. Both the high-temperature channel 214 and the low-temperature channel 224 may meander, or both may be formed in a straight line.

(Second embodiment)

[0035] As shown in FIG. 3, a vaporizer 300 according to the second embodiment is provided with a diversion channel 330 configured to divert liquid hydrogen at a preceding stage of a main heat exchanger 150, and differs from the vaporizer of the first embodiment in that part of the liquid hydrogen supplied from outside is preheated by an auxiliary heat exchanger 310.

[0036] The vaporizer 300 includes a supply channel 320 that allows liquid hydrogen supplied from outside to flow, the diversion channel 330 for diverting the liquid hydrogen flowing through the supply channel 320, and a main channel 340 connected to the diversion channel 330 and the main heat exchanger 150. The diversion channel 330 includes a first diversion channel 332 connected to the supply channel 320 and a second diversion channel 334 connected to the supply channel 320 and formed to be diverted from the first diversion channel 332. Part of the liquid hydrogen flowing through the supply channel 320 is diverted to the first diversion channel 332, and the other part of the liquid hydrogen flowing through the supply channel 320 is diverted to the second diversion channel 334 (diversion step).

[0037] The second diversion channel 334 is provided with a regulating valve 333 that can control the flow rate of the liquid hydrogen flowing through the second diversion channel 334.

[0038] The first diversion channel 332 is provided with the auxiliary heat exchanger 310 configured to heat the liquid hydrogen flowing through the first diversion channel 332 by heat exchange with a first heat source fluid supplied from outside. The auxiliary heat exchanger 310 is of an open rack type heat exchanger including a large number of heat transfer tubes 312 that allow the liquid hydrogen from the first diversion channel 332 to flow in (indicated by dashed arrows in FIG. 3) and a trough 314 that allows the first heat source fluid to flow down on the outer peripheral surface of the large number of heat transfer tubes 312. In the auxiliary heat exchanger 310, seawater or industrial water is used for the first heat source fluid, as in the main heat exchanger 150. The auxiliary heat exchanger 310 heats the liquid hydrogen in the first diversion channel 332 to a predetermined temperature (first heating step).

[0039] The vaporizer 300 is configured such that the magnitude of the heat load applied to the first heat source fluid from the liquid hydrogen for processing the liquid hydrogen of a unit flow rate in the auxiliary heat exchanger 310 is smaller than the magnitude of the heat load applied to the second heat source fluid from the liquid hydrogen for processing the liquid hydrogen of a unit flow rate in the main heat exchanger 150. That is, the vaporizer 300 is configured such that, when hydrogen of the same heat quantity is supplied to each of the auxiliary heat exchanger 310 and the main heat exchanger 150, the supply flow rate of the first heat source fluid to the auxiliary heat exchanger 310 is greater than the supply flow rate of the second heat source fluid to the main heat exchanger 150. For example, a pump (not shown) for allowing the first heat source fluid to flow into the auxiliary heat exchanger 310 is provided on the inlet side of the first heat source fluid in the auxiliary heat exchanger 310. Since the pump allows the first heat source fluid of a larger flow rate to be supplied to the auxiliary heat exchanger 310, the heat load applied to the first heat source fluid from the liquid hydrogen for processing hydrogen of a unit flow rate is smaller in the auxiliary heat exchanger 310. That is, the pump can send out the first heat source fluid at a flow rate larger than the pump (not shown) that allows the second heat source fluid to flow into the main heat exchanger 150. Note that the vaporizer 300 may be configured such that the flow rate of the first heat source fluid supplied to the auxiliary heat exchanger 310 is greater than or equivalent to the flow rate of the second heat source fluid supplied to the main heat exchanger 150.

[0040] The hydrogen flowing into the first diversion channel 332 and heated by the auxiliary heat exchanger 310 and the liquid hydrogen flowing into the second diversion channel 334 flow into the main channel 340 and merge (merging step).

[0041] In the vaporizer 300, the hydrogen from the first diversion channel 332 and the liquid hydrogen from the second diversion channel 334 merge, thereby generating hydrogen having a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure in the main channel 340. This allows hydrogen in a gaseous state or a supercritical state having a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure to be introduced from the main channel 340 to the main heat exchanger 150. Note that hydrogen having a temperature equal to or lower than the boiling point of the liquefied natural gas under normal pressure may be generated by the hydrogen from the first diversion channel 332 and the liquid hydrogen from the second diversion channel 334 merging.

[0042] The hydrogen supplied to the main heat exchanger 150 is heated to a predetermined temperature by heat exchange with the second heat source fluid as in the first embodiment (second heating step). The hydrogen heated to a predetermined temperature is derived toward external hydrogen gas demand destinations.

[0043] In the vaporizer 300 configured in this way, the hydrogen flowing into the first diversion channel 332 and heated by the auxiliary heat exchanger 310 merges with the liquid hydrogen in the second diversion channel 334 and flows into the main channel 340. This allows the hydrogen higher than the liquid hydrogen in temperature to flow into the main heat exchanger 150. This allows the main heat exchanger 150 to suppress icing on the outer surface of the heat transfer tubes 166 while alleviating the thermal stress applied to the heat transfer tubes 166.

[0044] Furthermore, in the auxiliary heat exchanger 310, by increasing the supply amount of the first heat source fluid, the magnitude of the heat load applied to the first heat source fluid from the liquid hydrogen for processing the liquid hydrogen will be smaller than the main heat exchanger 150. Therefore, the auxiliary heat exchanger 310 can also suppress icing on the outer surface of the heat transfer tubes while alleviating the thermal stress applied to the heat transfer tubes 312. As in the first embodiment, the hydrogen having a temperature equal to or higher than the boiling point of the liquefied natural gas under normal pressure can be introduced into the main heat exchanger 150, allowing the existing open rack type vaporizer for vaporizing the liquefied natural gas to be used as the main heat exchanger 150. Note that the temperature of the hydrogen introduced into the main heat exchanger 150 may be equal to or lower than the boiling point of the liquefied natural gas under normal pressure.

(Modification of second embodiment)

[0045] As shown in FIG. 4, in the vaporizer 300, an auxiliary heat exchanger 410 provided on a first diversion channel 432 may include an intermediate fluid type heat exchanger instead of the open rack type heat exchanger.

[0046] The auxiliary heat exchanger 410 provided on the first diversion channel 432 of a diversion channel 430 is configured in almost the same way as the auxiliary heat exchanger 110 in the first embodiment. The auxiliary heat exchanger 410 includes an intermediate fluid evaporation unit E1 configured to evaporate an intermediate fluid M 1 housed in the casing by heat exchange with the first heat source fluid, and a hydrogen heating unit E2 configured to heat the liquid hydrogen in the first diversion channel 432 by heat exchange with the evaporated intermediate fluid M1 in a gaseous state. The hydrogen in the first diversion channel 432 heated by the auxiliary heat exchanger 410 flows into a main channel 440, merges with the liquid hydrogen from a second diversion channel 434, and then flows into the main heat exchanger 150.

[0047] In this case as well, as in the second embodiment, it is possible to allow the hydrogen higher than the liquid hydrogen in temperature to flow into the main heat exchanger 150, making it possible to suppress icing on the outer surface of the heat transfer tubes 166 while alleviating the thermal stress applied to the heat transfer tubes 166 in the main heat exchanger 150.

[0048] Note that the auxiliary heat exchanger 410 on the first diversion channel 432 may include a microchannel type heat exchanger in a similar manner to the auxiliary heat exchanger 210 described in the modification of the first embodiment, instead of the intermediate fluid type heat exchanger. In this case, as shown in FIG. 5, an auxiliary heat exchanger 510, which is a microchannel type heat exchanger, is provided on a first diversion channel 532 of a diversion channel 530. The liquid hydrogen flowing into the diversion channel 530 is heated by heat exchange with the first heat source fluid in the auxiliary heat exchanger 510.

[0049] It should be understood that the embodiments disclosed this time are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the scope of claims instead of the above description, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

[0050] Here, the embodiments will be outlined.

(1) A liquid hydrogen vaporizer according to the present disclosure is a liquid hydrogen vaporizer for generating hydrogen in a gaseous state or a supercritical state from liquid hydrogen. The liquid hydrogen vaporizer includes: an auxiliary heat exchanger configured to heat liquid hydrogen by heat exchange with a heating fluid having a freezing point lower than a freezing point of seawater or industrial water; and an open rack type main heat exchanger including heat transfer tubes for allowing hydrogen to flow and a trough configured to supply seawater or industrial water to outer surfaces of the heat transfer tubes, the main heat exchanger heating the hydrogen flowing out from the auxiliary heat exchanger by heat exchange with seawater or industrial water.
The liquid hydrogen vaporizer configured in this way includes the auxiliary heat exchanger for preheating the liquid hydrogen as a preceding stage of the main heat exchanger, allowing hydrogen at a temperature higher than the temperature of the liquid hydrogen to flow into the main heat exchanger. This allows the main heat exchanger to suppress icing on the outer surfaces of the heat transfer tubes while alleviating the thermal stress applied to the heat transfer tubes. Furthermore, as the heating fluid of the auxiliary heat exchanger, a fluid having a freezing point lower than the freezing point of water is used, making the heating fluid less likely to freeze and allowing icing to be suppressed in the auxiliary heat exchanger.

(2) The auxiliary heat exchanger may include an intermediate fluid type heat exchanger using an intermediate fluid as the heating fluid, and is configured to perform heat exchange via the intermediate fluid between the liquid hydrogen and a heat source fluid supplied from outside. In this case, the intermediate fluid type heat exchanger may include: an intermediate fluid evaporation unit configured to vaporize at least part of the intermediate fluid by heat exchange with the heat source fluid; and a hydrogen heating unit provided with heat transfer tubes for allowing the liquid hydrogen to flow in and configured to heat the liquid hydrogen in the heat transfer tubes by heat exchange with the vaporized intermediate fluid.
In this aspect, as the auxiliary heat exchanger at the preceding stage of the main heat exchanger, the intermediate fluid type heat exchanger using the heating medium as the intermediate fluid is used. In this case, it is possible to use seawater or industrial water as a heat source fluid to heat and evaporate the intermediate fluid.

(3) The liquid hydrogen vaporizer may further include: a main channel connected to the main heat exchanger; and a diversion channel configured to divert the liquid hydrogen supplied from outside, the diversion channel including: a first diversion channel configured to allow a first part of the liquid hydrogen supplied from outside to flow in; and a second diversion channel configured to allow a second part of the liquid hydrogen supplied from outside to flow in. In this case, the auxiliary heat exchanger may be provided on the first diversion channel. The diversion channel may be connected to the main channel to allow the hydrogen flowing into the first diversion channel and heated by the auxiliary heat exchanger and the liquid hydrogen flowing into the second diversion channel to merge and flow into the main channel.
In this aspect, by allowing the hydrogen diverted to the first diversion channel and heated by the auxiliary heat exchanger and the liquid hydrogen diverted to the second diversion channel to merge and flow into the main channel, it is possible to allow the hydrogen higher than the liquid hydrogen in temperature to flow into the main heat exchanger. This allows the main heat exchanger to suppress icing on the outer surfaces of the heat transfer tubes while alleviating the thermal stress applied to the heat transfer tubes.

(4) The liquid hydrogen vaporizer according to the present disclosure is a liquid hydrogen vaporizer for generating hydrogen in a gaseous state or a supercritical state from liquid hydrogen. The liquid hydrogen vaporizer includes: an open rack type main heat exchanger including heat transfer tubes configured to allowing the hydrogen to flow in and a trough configured to supply seawater or industrial water to outer surfaces of the heat transfer tubes, the main heat exchanger heating the hydrogen in the heat transfer tubes by heat exchange with seawater or industrial water; a main channel connected to the main heat exchanger; a diversion channel configured to divert the liquid hydrogen supplied from outside, the diversion channel including: a first diversion channel configured to allow a first part of the liquid hydrogen supplied from outside to flow in; and a second diversion channel configured to allow a second part of the liquid hydrogen supplied from outside to flow in; and an auxiliary heat exchanger disposed on the first diversion channel and configured to heat the liquid hydrogen flowing through the first diversion channel by heat exchange with a heating fluid. The diversion channel is connected to the main channel to allow the heated hydrogen flowing through the first diversion channel and the liquid hydrogen flowing through the second diversion channel to merge and flow into the main channel. Magnitude of a heat load of the heating fluid required to heat the liquid hydrogen in the auxiliary heat exchanger is smaller than magnitude of a heat load of seawater or industrial water required to heat the hydrogen in the main heat exchanger.
The liquid hydrogen vaporizer configured in this way allows the hydrogen diverted to the first diversion channel and heated by the auxiliary heat exchanger and the liquid hydrogen diverted to the second diversion channel to merge and flow into the main channel. This allows the hydrogen higher than the liquid hydrogen in temperature to flow into the main heat exchanger. This allows the main heat exchanger to suppress icing on the outer surfaces of the heat transfer tubes while alleviating the thermal stress applied to the heat transfer tubes. Furthermore, since the heat load of the heating fluid in the auxiliary heat exchanger is smaller than the heat load of seawater or industrial water in the main heat exchanger, the auxiliary heat exchanger into which the liquid hydrogen is introduced can also suppress icing while alleviating thermal stress.

(5) The liquid hydrogen vaporizer may be configured to generate hydrogen having a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure by heating liquid hydrogen in the auxiliary heat exchanger. (6) The liquid hydrogen vaporizer may be configured to generate hydrogen having a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure by merging of the hydrogen from the first diversion channel and the liquid hydrogen from the second diversion channel.
In these aspects, the liquid hydrogen is heated by the auxiliary heat exchanger, and the hydrogen having a temperature equal to or higher than the boiling point of liquefied natural gas under normal pressure is introduced to the main heat exchanger. Therefore, the open rack type vaporizer for vaporizing liquefied natural gas can also be used as the main heat exchanger. In this case, the introduction cost of the liquid hydrogen vaporizer can be reduced.

(7) A method for generating hydrogen according to the present disclosure is a method for generating hydrogen in a gaseous state or a supercritical state by heating liquid hydrogen. The method includes: a first heating step of heating liquid hydrogen supplied from outside by heat exchange with a heating fluid having a freezing point lower than a freezing point of seawater or industrial water in an auxiliary heat exchanger; and a second heating step of allowing hydrogen flowing out from the auxiliary heat exchanger to flow into heat transfer tubes of a main heat exchanger, and heating the hydrogen in the heat transfer tubes to a predetermined temperature by heat exchange with seawater or industrial water.

(8) The first heating step may include generating hydrogen having a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure.

(9) A method for generating hydrogen according to the present disclosure is a method for generating hydrogen in a gaseous state or a supercritical state by heating liquid hydrogen. The method includes: a diversion step of diverting liquid hydrogen supplied from outside to a first diversion channel and a second diversion channel; a first heating step of heating the liquid hydrogen in the first diversion channel by heat exchange with a heating fluid in an auxiliary heat exchanger provided on the first diversion channel; a merging step of allowing hydrogen from the first diversion channel and the liquid hydrogen from the second diversion channel to merge and flow into a main channel; and a second heating step of allowing the hydrogen in the main channel to flow into heat transfer tubes of a main heat exchanger and heating the hydrogen in the heat transfer tubes to a predetermined temperature by heat exchange with seawater or industrial water. Magnitude of a heat load of the heating fluid for heating the liquid hydrogen in the first heating step is smaller than magnitude of a heat load of seawater or industrial water for heating the hydrogen in the second heating step.

(10) In the merging step, a fluid obtained by merging the hydrogen and the liquid hydrogen may have a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure.

[0051] According to the present disclosure, it is possible to suppress icing on the heat transfer tubes while alleviating thermal stress in the heat transfer tubes of the open rack type heat exchanger in the liquid hydrogen vaporizer.

Claims

1. A liquid hydrogen vaporizer for generating hydrogen in a gaseous state or a supercritical state from liquid hydrogen, the liquid hydrogen vaporizer comprising:

an auxiliary heat exchanger configured to heat liquid hydrogen by heat exchange with a heating fluid having a freezing point lower than a freezing point of seawater or industrial water; and

an open rack type main heat exchanger including heat transfer tubes for allowing hydrogen to flow in and a trough configured to supply seawater or industrial water to outer surfaces of the heat transfer tubes, the main heat exchanger heating the hydrogen flowing out from the auxiliary heat exchanger by heat exchange with seawater or industrial water.

2. The liquid hydrogen vaporizer according to claim 1, wherein

the auxiliary heat exchanger includes an intermediate fluid type heat exchanger using an intermediate fluid as the heating fluid, and is configured to perform heat exchange via the intermediate fluid between the liquid hydrogen and a heat source fluid supplied from outside,

the intermediate fluid type heat exchanger includes:

an intermediate fluid evaporation unit configured to vaporize at least part of the intermediate fluid by heat exchange with the heat source fluid; and

a hydrogen heating unit provided with heat transfer tubes for allowing the liquid hydrogen to flow in and configured to heat the liquid hydrogen in the heat transfer tubes by heat exchange with the vaporized intermediate fluid.

3. The liquid hydrogen vaporizer according to claim 2, further comprising:

a main channel connected to the main heat exchanger; and

a diversion channel configured to divert the liquid hydrogen supplied from outside, the diversion channel including: a first diversion channel configured to allow a first part of the liquid hydrogen supplied from outside to flow in; and a second diversion channel configured to allow a second part of the liquid hydrogen supplied from outside to flow in,

wherein the auxiliary heat exchanger is provided on the first diversion channel, and

the diversion channel is connected to the main channel to allow the hydrogen flowing into the first diversion channel and heated by the auxiliary heat exchanger and the liquid hydrogen flowing into the second diversion channel to merge and flow into the main channel.

4. A liquid hydrogen vaporizer for generating hydrogen in a gaseous state or a supercritical state from liquid hydrogen, the liquid hydrogen vaporizer comprising:

an open rack type main heat exchanger including heat transfer tubes configured to allow the hydrogen to flow in and a trough configured to supply seawater or industrial water to outer surfaces of the heat transfer tubes, the main heat exchanger heating the hydrogen in the heat transfer tubes by heat exchange with seawater or industrial water;

a main channel connected to the main heat exchanger;

a diversion channel configured to divert the liquid hydrogen supplied from outside, the diversion channel including: a first diversion channel configured to allow a first part of the liquid hydrogen supplied from outside to flow in; and a second diversion channel configured to allow a second part of the liquid hydrogen supplied from outside to flow in; and

an auxiliary heat exchanger disposed on the first diversion channel and configured to heat the liquid hydrogen flowing through the first diversion channel by heat exchange with a heating fluid,

wherein the diversion channel is connected to the main channel to allow the heated hydrogen flowing through the first diversion channel and the liquid hydrogen flowing through the second diversion channel to merge and flow into the main channel, and

magnitude of a heat load of the heating fluid required to heat the liquid hydrogen in the auxiliary heat exchanger is smaller than magnitude of a heat load of seawater or industrial water required to heat the hydrogen in the main heat exchanger.

5. The liquid hydrogen vaporizer according to claim 1 or 2, wherein the liquid hydrogen vaporizer is configured to generate hydrogen having a temperature equal to or higher than a boiling point of a liquefied natural gas under normal pressure by heating liquid hydrogen in the auxiliary heat exchanger.

6. The liquid hydrogen vaporizer according to claim 3 or 4, wherein the liquid hydrogen vaporizer is configured to generate hydrogen having a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure by merging of the hydrogen from the first diversion channel and the liquid hydrogen from the second diversion channel.

7. A generation method for generating hydrogen in a gaseous state or a supercritical state by heating liquid hydrogen, the generation method comprising:

a first heating step of heating liquid hydrogen supplied from outside by heat exchange with a heating fluid having a freezing point lower than a freezing point of seawater or industrial water in an auxiliary heat exchanger; and

a second heating step of allowing hydrogen flowing out from the auxiliary heat exchanger to flow into heat transfer tubes of a main heat exchanger, and heating the hydrogen in the heat transfer tubes to a predetermined temperature by heat exchange with seawater or industrial water.

8. The generation method for generating hydrogen in a gaseous state or a supercritical state according to claim 7, wherein the first heating step includes generating hydrogen having a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure.

9. A generation method for generating hydrogen in a gaseous state or a supercritical state by heating liquid hydrogen, the generation method comprising:

a diversion step of diverting liquid hydrogen supplied from outside to a first diversion channel and a second diversion channel;

a first heating step of heating the liquid hydrogen in the first diversion channel by heat exchange with a heating fluid in an auxiliary heat exchanger provided on the first diversion channel;

a merging step of allowing hydrogen from the first diversion channel and the liquid hydrogen from the second diversion channel to merge and flow into a main channel; and

a second heating step of allowing the hydrogen in the main channel to flow into heat transfer tubes of a main heat exchanger and heating the hydrogen in the heat transfer tubes to a predetermined temperature by heat exchange with seawater or industrial water,

wherein magnitude of a heat load of the heating fluid for heating the liquid hydrogen in the first heating step is smaller than magnitude of a heat load of seawater or industrial water for heating the hydrogen in the second heating step.

10. The generation method for generating hydrogen in a gaseous state or a supercritical state according to claim 9, wherein in the merging step, a fluid obtained by merging the hydrogen and the liquid hydrogen has a temperature equal to or higher than a boiling point of liquefied natural gas under normal pressure.

Drawing