Cryogenic separation device

Abstract

This cryogenic separation device comprises: a heat exchanger that exchanges heat between air supplied from an air supply source and refrigerant to cool the air; a rectification tower that is configured from a single tower into which the cooled air flows and which separates the air into nitrogen and oxygen; a condenser that condenses nitrogen gas separated in the rectification tower by the cold heat of hydrogen supplied from a liquid hydrogen supply source; and an evaporator that evaporates liquid oxygen separated in the rectification tower. The liquid nitrogen condensed by the condenser and the oxygen gas evaporated by the evaporator are supplied to the rectification tower.

Description

Cryogenic separation equipment

[0001] The present disclosure relates to a cryogenic separation device.

[0002] Patent Document 1 discloses an air separation unit that uses the cold energy of liquid hydrogen. Specifically, the system includes a liquid hydrogen fuel supply system including a liquid hydrogen storage tank, a vaporizer that vaporizes liquid hydrogen discharged from the liquid hydrogen storage tank, a hydrogen fuel cell that generates electricity by receiving the vaporized hydrogen gas, and a cold energy utilization unit that recovers and utilizes the cold energy through heat exchange during the liquid hydrogen vaporization process. The air separation unit is configured to separate air using the cold energy generated in the liquid hydrogen vaporizer.

[0003] KR102427731B1

[0004] An object of the present disclosure is to provide, as an example, a cryogenic separation device that can reduce the compression power required to send air to a rectification column and that can simplify the configuration of the rectification column compared to conventional devices.

[0005] A cryogenic separation apparatus according to one aspect of the present disclosure comprises a heat exchanger that cools air supplied from an air supply source by exchanging heat with a refrigerant, a rectification tower consisting of a single tower into which the cooled air flows and which separates the air into nitrogen and oxygen, a condenser that condenses the nitrogen gas separated in the rectification tower using the cold heat of hydrogen supplied from a liquid hydrogen supply source, and an evaporator that evaporates the liquid oxygen separated in the rectification tower, and the liquid nitrogen condensed in the condenser and the oxygen gas evaporated in the evaporator are supplied to the rectification tower.

[0006] A cryogenic separation apparatus according to one aspect of the present disclosure has the advantages of being able to reduce the compression power required to send air to a rectification column and allowing the rectification column to be configured simply, compared to conventional apparatuses.

[0007] Fig. 1 is a diagram illustrating an example of a cryogenic separation apparatus according to an embodiment, and Fig. 2 is a diagram illustrating an example of a heat exchanger and an evaporator in the cryogenic separation apparatus according to an embodiment.

[0008] In a typical cryogenic separation system, a rectification column requires a condenser for nitrogen, a low-boiling component, and an evaporator for oxygen, a high-boiling component. This system is often equipped with two rectification columns: a high-pressure column and a low-pressure column. The condenser for the high-pressure column and the evaporator for the low-pressure column are combined into a single heat exchanger. This allows nitrogen gas from the high-pressure column to be condensed with liquid oxygen from the low-pressure column, and the nitrogen gas from the high-pressure column to evaporate the liquid oxygen from the low-pressure column. The majority of the power consumed in this cryogenic separation process is the compression power required to send air to the high-pressure column. In other words, to condense nitrogen gas from the high-pressure column with liquid oxygen from the low-pressure column in the cryogenic separation process, the boiling point of the nitrogen in the high-pressure column must be increased by pressurizing the nitrogen in the high-pressure column so that it exceeds the boiling point of the oxygen in the low-pressure column. Separating air into oxygen and nitrogen in the rectification column requires cold energy to cryogenically cool the air supplied to the rectification column. For this reason, in cryogenic separation processes, most of the compressed air pressurized by a booster such as a compressor is supplied to the high-pressure rectification column, and part of the compressed air is supplied to the low-pressure rectification column via an expansion turbine. The expansion turbine can generate cold by expanding the compressed air in a manner similar to adiabatic expansion.

[0009] In such a situation, the present inventors have discovered that the compression power required to send air to the fractionator can be reduced by utilizing the cold energy of liquid hydrogen for cryogenic separation.

[0010] As described above, Patent Document 1 discloses an air separation unit that utilizes the cold energy of liquid hydrogen. However, since this air separation unit is composed of an upper distillation column and a lower distillation column, there is room for improvement in terms of simplifying the configuration of the device.

[0011] Therefore, the present inventors conducted extensive research into a cryogenic separation device that can reduce the compression power required to send air to a distillation column and that can simplify the configuration of the distillation column, and as a result, they came up with the above-mentioned aspect of the present disclosure.

[0012] Specific examples of the above-described aspects of the present disclosure will be described below with reference to the accompanying drawings. Each of the specific examples described below is an example of the above-described aspects of the present disclosure. Therefore, unless otherwise stated in the claims, the shapes, numerical values, components, arrangement positions and connection forms of the components shown below do not limit the scope of the claims.

[0013] Furthermore, among the components described below, components that are not described in the independent claims that represent the highest concept of the present disclosure are described as optional components. Furthermore, in the drawings, components with the same reference numerals may not be described in detail. The drawings are schematic illustrations of each component for ease of understanding, and the shapes, dimensional ratios, and the like may not be accurately depicted.

[0014] (Embodiment) Fig. 1 is a diagram showing an example of a cryogenic separation device according to an embodiment. In Fig. 1, gravity acts from "top" to "bottom", and "upper" and "lower" are defined as shown in the figure.

[0015] The cryogenic separation device 100 includes a heat exchanger 10, a rectification column 11, a condenser 12, and an evaporator 14.

[0016] The heat exchanger 10 is a device that cools air by exchanging heat between the air supplied from an air supply source and a refrigerant. The heat exchanger 10 may have any configuration as long as it can exchange heat between the air supplied from the air supply source and a refrigerant to cool the air.

[0017] In this example, air at approximately the outside temperature supplied from the air supply source functions as a heating fluid, and a cryogenic refrigerant functions as a heat-receiving fluid in the heat exchanger 10. Specific examples of such refrigerants will be described later.

[0018] The air supply source includes a known device for pre-treating the air to be supplied to the cryogenic separation apparatus 100. For example, the air supply source may include an air filter for removing dust, an air compressor, a cooling tower, an adsorber for removing moisture, etc. In the air compressor, the air that has passed through the air filter is pressurized by an amount equivalent to the pressure loss in the piping that constitutes the air path from the air compressor to the rectification column 11.

[0019] In the cooling tower, air pressurized by an air compressor is cooled to approximately the outside temperature, and then in the adsorber, moisture and carbon dioxide are removed from the air cooled in the cooling tower.

[0020] However, the above-described configuration of the air supply source is merely an example and is not limited to this example. For example, since the air is only pressurized by the air compressor by the amount of pressure loss in the piping that constitutes the air path, the air supply source does not need to be provided with a water cooling system for cooling the air.

[0021] The distillation tower 11 is a single-column apparatus into which air cooled in the heat exchanger 10 flows and separates the air into nitrogen and oxygen. The air that has passed through the heat exchanger 10 flows into the distillation tower 11 in its gaseous state. In the distillation tower 11, the air cooled to a cryogenic temperature in the heat exchanger 10 is separated into nitrogen and oxygen by utilizing the difference in boiling points between oxygen and nitrogen. Specifically, in the distillation tower 11, a gas-liquid equilibrium state is created by gas-liquid contact between a liquid descending from above and an ascending gas. As a result, the nitrogen component with a low boiling point is contained in a large amount in the gas phase, and the oxygen component with a high boiling point is contained in a large amount in the liquid phase. By repeating this process, the distillation tower 11 produces nitrogen gas with a higher nitrogen concentration toward the top, and oxygen with a higher oxygen concentration toward the bottom. Since the distillation process of the distillation tower 11 is well known, a detailed description thereof will be omitted.

[0022] The condenser 12 is a device that condenses the nitrogen gas separated in the rectification column 11 using the cold energy of hydrogen supplied from the liquid hydrogen supply source. The liquid nitrogen condensed in the condenser 12 is supplied to the rectification column 11. The condenser 12 may have any configuration as long as it can condense the nitrogen gas separated in the rectification column 11 using the cold energy of hydrogen. The rectification columns of existing cryogenic separation devices generally include an upper distillation column (low-pressure column) and a lower distillation column (high-pressure column). In contrast, the cryogenic separation device 100 of this embodiment is characterized in that, as described above, it can utilize the cold energy of hydrogen supplied from the liquid hydrogen supply source, thereby eliminating the need for a lower distillation column (high-pressure column). Therefore, in this specification, the rectification column 11 having such a characteristic is referred to as a "single column."

[0023] In this example, the condenser 12 is provided near the top of the distillation column 11. This allows nitrogen gas extracted from the top surface of the distillation column 11 to be easily supplied to the condenser 12. The liquid nitrogen condensed in the condenser 12 is stored in a liquid nitrogen storage tank 13 adjacent to the condenser 12, and the liquid nitrogen in the liquid nitrogen storage tank 13 is supplied to the top of the distillation column 11.

[0024] The liquid nitrogen in the liquid nitrogen storage tank 13 may be taken out as high-purity nitrogen to the outside. This eliminates the need for a dedicated heat exchanger for liquefying the nitrogen gas from the distillation column 11 when taking out liquid nitrogen from the cryogenic separation device 100.

[0025] However, the above is merely an example and is not limiting. For example, the nitrogen gas before flowing into the condenser 12 may be extracted to the outside as high-purity nitrogen.

[0026] The liquid hydrogen supply source may include a liquid hydrogen storage tank and a pump for supplying liquid hydrogen in the liquid hydrogen storage tank to the cryogenic separation device 100 .

[0027] However, the above-described configuration of the liquid hydrogen supply source is merely an example and is not limited to this example. For example, when hydrogen recovered from cryogenic heat in the cryogenic separation device 100 is used in a hydrogen gas turbine or the like, it is necessary to pressurize the hydrogen to a high pressure above the critical pressure. Therefore, as in this example, it is better to pressurize the hydrogen to a high pressure using a pump before the cryogenic heat recovery. This reduces the pump power compared to when the hydrogen is pressurized to a high pressure after the cryogenic heat recovery. On the other hand, when the hydrogen recovered from cryogenic heat in the cryogenic separation device 100 is used as a raw material for a chemical reaction, for example, and there is no need to pressurize the hydrogen, the timing of pressurizing the hydrogen using the pump may be either before or after the cryogenic heat recovery.

[0028] The hydrogen that has passed through the condenser 12 is supplied to an appropriate hydrogen utilization facility. Examples of such hydrogen utilization facilities include, but are not limited to, a hydrogen gas turbine.

[0029] The evaporator 14 is a device that evaporates the liquid oxygen separated in the rectification column 11. The oxygen gas evaporated in the evaporator 14 is supplied to the rectification column 11. The evaporator 14 may have any configuration as long as it can evaporate the liquid oxygen separated in the rectification column 11.

[0030] In this example, the evaporator 14 is provided near the bottom of the distillation column 11, and liquid oxygen taken out from the bottom of the distillation column 11 is supplied to the evaporator 14, and the evaporator 14 recovers heat from an appropriate heat medium, thereby evaporating the liquid oxygen in the evaporator 14. Specific examples of such heat medium will be described later.

[0031] The liquid oxygen in the evaporator 14 may be taken out as high-purity oxygen from the bottom surface of the evaporator 14 to the outside, but is not limited to this. For example, oxygen gas in the distillation column 11 may be taken out as high-purity oxygen to the outside.

[0032] A control device may control the operation of each component of the cryogenic separation apparatus 100. The control device may include, for example, an arithmetic circuit and a memory circuit that stores a control program. Examples of the arithmetic circuit include an MPU or a CPU. Examples of the memory circuit include a memory. The control device may be configured with a single controller that performs centralized control, or may be configured with multiple controllers that cooperate with each other to perform distributed control. The functions of the elements disclosed herein may be performed using circuits or processing circuits including general-purpose processors, dedicated processors, integrated circuits, application-specific integrated circuits (ASICs), conventional circuits, or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this specification, a circuit, unit, or means is hardware that performs the enumerated functions or hardware that is programmed to perform the enumerated functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the enumerated functions. Where hardware is a processor that can be considered a type of circuit, the circuit, unit, or means is a combination of hardware and software, and the software is used to configure the hardware or processor.

[0033] As described above, the cryogenic separation apparatus 100 of this embodiment can reduce the compression power for sending air to the distillation column 11 and can simplify the configuration of the distillation column 11 compared to conventional apparatuses.

[0034] Specifically, the nitrogen gas separated in the rectification column 11 is condensed by the condenser 12 using the cold heat of hydrogen supplied from the liquid hydrogen supply source, so there is no need to pressurize the nitrogen gas present in the high-pressure rectification column as in conventional cryogenic separation apparatuses. In other words, the cryogenic separation apparatus 100 of this embodiment does not require the rectification column 11 to be configured as multiple columns, divided into a high-pressure column and a low-pressure column, and can be configured as a low-pressure single column.

[0035] Therefore, the cryogenic separation apparatus 100 of this embodiment can reduce the compression power required to send air to the rectification column 11 compared to conventional cryogenic separation apparatuses.

[0036] Furthermore, in the cryogenic separation apparatus 100 of this embodiment, the rectification column 11 can be configured more simply than in the invention disclosed in Patent Document 1.

[0037] Furthermore, the cryogenic separation device 100 of this embodiment can eliminate the need for a conventional expansion turbine by using the cryogenic heat of hydrogen to provide the cryogenic heat required for cryogenic separation.

[0038] <Specific example of heat exchanger and evaporator> Figure 2 is a diagram showing an example of a heat exchanger and evaporator in a cryogenic separation device of an embodiment. In Figure 2, gravity acts from "top" to "bottom", and "upper" and "lower" are taken as shown in the figure.

[0039] The cryogenic separation apparatus 100 includes a heat exchanger 10A, a heat exchanger 10B, a rectification column 11, a condenser 12, and an evaporator 14. Here, the rectification column 11 and the condenser 12 are the same as those described above, and therefore, a description thereof will be omitted.

[0040] Heat exchanger 10A is a device that pre-cools air using the cold energy of hydrogen as a refrigerant. Heat exchanger 10B is a device that further cools the air pre-cooled in heat exchanger 10A using the cold energy of hydrogen as a refrigerant. Evaporator 14 is a device that evaporates the liquid oxygen separated in rectification column 11 by recovering the heat of the air pre-cooled in heat exchanger 10A.

[0041] Here, the cryogenic separation device 100 includes a hydrogen path 21 through which hydrogen supplied from a liquid hydrogen supply source flows, and the hydrogen path 21 passes through the condenser 12, the heat exchanger 10B, and the heat exchanger 10A in this order. The hydrogen that has passed through the hydrogen path 21 is supplied to an appropriate hydrogen utilization facility in the same manner as described above.

[0042] The cryogenic separation apparatus 100 also includes an air path 20 through which air supplied from an air supply source flows, and the air path 20 passes through the heat exchanger 10A, the evaporator 14, and the heat exchanger 10B in this order. The tip of the air path 20 is connected to the distillation column 11.

[0043] That is, in heat exchanger 10A, air at approximately ambient temperature supplied from the air supply source functions as a heating fluid, and cryogenic hydrogen that has passed through heat exchanger 10B functions as a heat-receiving fluid. As a result, the air at approximately ambient temperature is pre-cooled, for example, to around minus several tens of degrees Celsius, through heat exchange with the hydrogen.

[0044] The evaporator 14 includes an evaporation tank 14A that stores liquid oxygen, and a heat exchanger 14B that is disposed in the liquid oxygen in the evaporation tank 14A. In the heat exchanger 14B, the air that has passed through the heat exchanger 10A functions as a heating fluid, and the liquid oxygen in the evaporation tank 14A functions as a heat-receiving fluid. As a result, the liquid oxygen in the evaporation tank 14A is evaporated by recovering heat from the air pre-cooled in the heat exchanger 10A, and the air pre-cooled in the heat exchanger 10A imparts heat of evaporation to the liquid oxygen, thereby further cooling the air.

[0045] In the heat exchanger 10B, the air that has passed through the evaporator 14 functions as a heating fluid, and the cryogenic hydrogen that has passed through the condenser 12 functions as a heat-receiving fluid. As a result, the air pre-cooled in the heat exchanger 10A and the evaporator 14 is cooled to, for example, about the temperature of liquid air by heat exchange with the hydrogen. The air that has passed through the heat exchanger 10B is then supplied to the rectification column 11.

[0046] In this way, the cryogenic separation apparatus 100 of this embodiment can utilize air as a heat source for evaporating liquid oxygen in the evaporator 14, and can utilize the sensible heat of hydrogen and the heat of evaporation of liquid oxygen as cold energy for cooling the air supplied to the distillation column 11 to the liquefaction temperature.

[0047] The reason why the air pre-cooled by the heat exchanger 10A is supplied to the evaporator 14 is as follows.

[0048] If air is supplied to the evaporator without being pre-cooled by the heat exchanger 10A, the temperature difference between the air and the liquid oxygen is large, which may damage the flow path components that make up the evaporator.

[0049] However, the cryogenic separation device 100 of this embodiment supplies air that has been pre-cooled by the heat exchanger 10A to the evaporator 14, thereby reducing the possibility of damage to the flow path components that make up the evaporator 14 compared to when air is supplied to the evaporator without being pre-cooled by the heat exchanger 10A.

[0050] Furthermore, if hydrogen at an appropriate temperature is to be supplied to the evaporator, it is necessary to properly maintain the flow path members in the evaporator so that hydrogen does not leak into the liquid oxygen from welds, joints, etc. of the flow path members.

[0051] However, the cryogenic separation device 100 of this embodiment supplies air pre-cooled in the heat exchanger 10A to the evaporator 14 via the air path 20, thereby reducing the maintenance burden on the flow path components that make up the evaporator 14 compared to when hydrogen is supplied to the evaporator.

[0052] From the above description, many modifications and other embodiments of the present disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art how to carry out the present disclosure. Substantial changes can be made in the structure and function of the present disclosure without departing from the spirit of the present disclosure.

[0053] (Regarding Each Aspect of the Present Disclosure) From the above description, the following each aspect of the present disclosure can be devised.

[0054] The cryogenic separation apparatus of the first aspect of the present disclosure comprises a heat exchanger that cools the air by exchanging heat between air supplied from an air supply source and a refrigerant, a rectification tower consisting of a single tower into which the cooled air flows and separates the air into nitrogen and oxygen, a condenser that condenses the nitrogen gas separated in the rectification tower using the cold heat of hydrogen supplied from a liquid hydrogen supply source, and an evaporator that evaporates the liquid oxygen separated in the rectification tower, and the liquid nitrogen condensed in the condenser and the oxygen gas evaporated in the evaporator are supplied to the rectification tower.

[0055] With this configuration, the cryogenic separation apparatus of this embodiment can reduce the compression power required to send air to the rectification column, and can simplify the configuration of the rectification column, compared to conventional devices.

[0056] Specifically, since the nitrogen gas separated in the rectification column is condensed by the condenser using the cold heat of hydrogen supplied from the liquid hydrogen supply source, there is no need to pressurize the nitrogen gas present in the high-pressure rectification column as in conventional cryogenic separation apparatuses. In other words, the cryogenic separation apparatus of this embodiment does not need to be configured with multiple rectification columns divided into a high-pressure column and a low-pressure column, but can be configured with a single low-pressure column.

[0057] Therefore, the cryogenic separation apparatus of this embodiment can reduce the compression power required to send air to the rectification column compared to conventional cryogenic separation apparatuses.

[0058] Furthermore, the cryogenic separation apparatus of this embodiment allows the rectification column to be configured more simply than the invention disclosed in Patent Document 1.

[0059] Furthermore, the cryogenic separation device of this embodiment can eliminate the need for a conventional expansion turbine by using the cryogenic heat of hydrogen to provide the cryogenic heat required for cryogenic separation.

[0060] Here, a second aspect of the present disclosure is a cryogenic separation apparatus according to the first aspect, wherein the heat exchangers include a first heat exchanger that precools air with the cryogenic heat of hydrogen as the refrigerant, and a second heat exchanger that further cools the air precooled in the first heat exchanger with the cryogenic heat of hydrogen as the refrigerant, and the evaporator may evaporate the liquid oxygen separated in the rectification column by recovering heat from the air precooled in the first heat exchanger. Furthermore, a third aspect of the present disclosure is a cryogenic separation apparatus according to the second aspect, wherein the cryogenic separation apparatus includes an air path through which air supplied from an air supply source flows, the air path passing through the first heat exchanger, the evaporator, and the second heat exchanger in this order. Furthermore, a fourth aspect of the present disclosure is a cryogenic separation apparatus according to the second or third aspect, wherein the hydrogen path through which hydrogen supplied from a liquid hydrogen supply source flows passes through the condenser, the second heat exchanger, and the first heat exchanger in this order.

[0061] According to the above configuration, the cryogenic separation apparatus of this embodiment can use air as a heat source for evaporating liquid oxygen in the evaporator, and can use the sensible heat of hydrogen and the heat of evaporation of liquid oxygen as cold energy for cooling the air supplied to the distillation column to the liquefaction temperature.

[0062] The reason why the air pre-cooled by the first heat exchanger is supplied to the evaporator is as follows.

[0063] If air is supplied to the evaporator without being pre-cooled by the first heat exchanger, the temperature difference between the air and the liquid oxygen is large, which may damage the flow path members that make up the evaporator.

[0064] However, in the cryogenic separation device of this embodiment, by supplying air that has been pre-cooled in the first heat exchanger to the evaporator, the possibility of damage to the flow path components that make up the evaporator can be reduced compared to when air is supplied to the evaporator without being pre-cooled in the first heat exchanger.

[0065] Furthermore, if hydrogen at an appropriate temperature is to be supplied to the evaporator, it is necessary to properly maintain the flow path members in the evaporator so that hydrogen does not leak into the liquid oxygen from welds, joints, etc. of the flow path members.

[0066] However, the cryogenic separation device of this embodiment supplies air pre-cooled in the first heat exchanger to the evaporator via an air path, thereby reducing the maintenance burden on the flow path components that make up the evaporator compared to when hydrogen is supplied to the evaporator.

[0067] A cryogenic separation apparatus according to a fifth aspect of the present disclosure may be configured such that, in the cryogenic separation apparatus according to the first aspect, the liquid nitrogen condensed in the condenser is taken out to the outside.

[0068] With this configuration, the cryogenic separation apparatus of this embodiment does not require a dedicated heat exchanger for liquefying nitrogen gas from the rectification column when liquid nitrogen is taken out from the cryogenic separation apparatus.

[0069] 10: Heat exchanger 10A: Heat exchanger 10B: Heat exchanger 11: Rectification column 12: Condenser 13: Liquid nitrogen storage tank 14: Evaporator 14A: Evaporation tank 14B: Heat exchanger 20: Air path 21: Hydrogen path 100: Cryogenic separation device

Claims

1. A cryogenic separation apparatus comprising: a heat exchanger that cools air supplied from an air supply source by exchanging heat with a refrigerant; a rectification column consisting of a single column into which the cooled air flows and which separates the air into nitrogen and oxygen; a condenser that condenses the nitrogen gas separated in the rectification column using the cold heat of hydrogen supplied from a liquid hydrogen supply source; and an evaporator that evaporates the liquid oxygen separated in the rectification column, wherein the liquid nitrogen condensed in the condenser and the oxygen gas evaporated in the evaporator are supplied to the rectification column.

2. The cryogenic separation apparatus according to claim 1, wherein the heat exchanger comprises a first heat exchanger that pre-cools the air with the cryogenic heat of the hydrogen as the refrigerant, and a second heat exchanger that further cools the pre-cooled air with the cryogenic heat of the hydrogen as the refrigerant, and the evaporator evaporates the liquid oxygen separated in the rectification column by recovering the heat of the air pre-cooled in the first heat exchanger.

3. The cryogenic separation device according to claim 2, further comprising an air path through which air supplied from the air supply source flows, the air path passing through the first heat exchanger, the evaporator and the second heat exchanger in this order.

4. A cryogenic separation device according to claim 2 or 3, further comprising a hydrogen path through which hydrogen supplied from the liquid hydrogen supply source flows, the hydrogen path passing through the condenser, the second heat exchanger and the first heat exchanger in this order.

5. A cryogenic separation apparatus according to claim 1, wherein the liquid nitrogen condensed in the condenser is taken out to the outside.

Images