Liquid nitrogen production device and liquid nitrogen production method

Abstract

To provide a production device which can produce liquid nitrogen from a nitrogen gas by using the hot / cold heat of a liquefied natural gas, and a production method.SOLUTION: A liquid nitrogen production device 1 comprises: an LNG heat exchanger E3 for cooling a supply nitrogen gas by using the cold heat of a liquefied natural gas; a booster 11 for decompressing the cooled supply nitrogen gas, and discharging a high-pressure nitrogen gas; a recycle heat exchanger E2 for heat-exchanging the discharged high-pressure nitrogen gas; an expansion turbine 12 into which a first portion gas being a part of the high-pressure nitrogen gas which has passed a part of the recycle heat exchanger E2 is introduced, and which expands the first portion gas, and discharges a low-temperature nitrogen gas; a first expansion valve 13 for decompressing a second portion gas other than the first portion gas in the high-pressure nitrogen gas after passing the recycle heat exchanger E2; and a first separator 14 into which the decompressed second portion gas and the low-temperature nitrogen gas discharged from the expansion turbine 12 are introduced, and which separates a nitrogen gas and liquid nitrogen.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a liquid nitrogen production apparatus and a liquid nitrogen production method, and more particularly to a liquid nitrogen production apparatus and a liquid nitrogen production method that utilize the refrigeration of liquefied natural gas (LNG), for example. [Background technology]

[0002] Patent Document 1 and Patent Document 2 disclose methods for effectively utilizing the coldness of LNG. Patent Document 1 and Patent Document 2 (for example, Figure 2) disclose a method for utilizing the coldness of LNG to liquefy nitrogen gas. In Patent Document 1, in order to efficiently produce liquid gas, the cold energy released when evaporating LNG is used to cool the gas at a liquefied natural gas (LNG) receiving and gasification terminal. In addition, recovery of boil-off gas (BOG) is important in LNG, and Patent Document 3 (for example, Figure 3) discloses a method for re-liquefying BOG.

[0003] When LNG refrigeration is used to reliquefy BOG, the temperature of the LNG may generally fluctuate, for example, from approximately -156°C to -130°C. In the techniques of Patent Documents 1 to 3, when the LNG temperature fluctuates upward, the amount of liquid nitrogen produced decreases significantly, or it becomes necessary to abandon the production of liquid nitrogen depending on the LNG temperature. In addition, when the LNG terminal and the cryogenic air separation unit (ASU) are installed far apart, it is necessary to collect LNG refrigeration at the LNG terminal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4142559 [Patent Document 2] China Utility Model No. 208751137 [Patent Document 3] U.S. Patent No. 9,927,068 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a manufacturing apparatus and a manufacturing method that can manufacture liquid nitrogen from nitrogen gas by utilizing the refrigeration of liquefied natural gas in a manner different from that of conventional techniques. The present invention also provides a manufacturing apparatus and method that can produce high-pressure nitrogen gas from medium-pressure nitrogen gas with lower power consumption than conventional methods. The present invention also provides a manufacturing apparatus and method capable of manufacturing liquid nitrogen that can be used even in the cold of high-temperature liquefied natural gas or in the presence of seasonal temperature fluctuations. The present invention also provides a production apparatus and method that can produce liquid nitrogen from nitrogen gas in conjunction with an air separation unit by utilizing the coldness of liquefied natural gas after reliquefying BOG in an LNG tank. [Means for solving the problem]

[0006] The liquid nitrogen production apparatus (1) of the present invention is an LNG heat exchanger (E3, E30) that cools supply nitrogen gas (FG) at a first pressure (e.g., 2.0 MPa to 3.0 MPa) to a temperature (e.g., a temperature higher than the critical temperature of nitrogen gas (-147°C)) by utilizing the cold energy of liquefied natural gas (LNG) at a predetermined temperature range (e.g., -160°C to -120°C); The supply nitrogen gas (G0) cooled in the LNG heat exchanger (E3) is compressed to a second pressure (for example, 4.0 MPa to 5.0 MPa) higher than the first pressure, and high-pressure nitrogen gas (G1) is discharged. Booster (11) and, The aforementioned Booster (11) a recycle heat exchanger (E2, E12) for exchanging heat (cooling) the high-pressure nitrogen gas (G1) discharged from the The aforementioned Booster (11)an expansion turbine (12) for driving the expansion turbine (12), into which a first partial gas (G11) that is a part of the high-pressure nitrogen gas (G1) that has passed through a part of the recycle heat exchangers (E2, E12) is introduced, the expansion turbine (12) expands the first partial gas (G11) to a third pressure (e.g., 0.5 MPa to 1.0 MPa) that is lower than the first pressure (e.g., 2.0 MPa), and discharges low-temperature nitrogen gas (G111) (partially liquefied or at a temperature near the liquefaction point); a first expansion valve (13) that reduces the pressure of a second portion gas (G12) of the high-pressure nitrogen gas (G1) other than the first portion gas (G11) after the high-pressure nitrogen gas (G1) has passed through the recycle heat exchangers (E2, E12) (to the same or approximately the same pressure as the third pressure (e.g., 0.5 MPa)); a first separator (14) into which the second partial gas (G12) decompressed by the first expansion valve (13) and the low-temperature nitrogen gas (G111) discharged from the expansion turbine (12) are introduced, and which separates the nitrogen gas (N2G) from the liquid nitrogen (LN2); Equipped with.

[0007] The liquefied natural gas in the predetermined temperature range may be liquefied natural gas after being used to reliquefy BOG in an LNG tank. The liquefied natural gas may be liquefied natural gas delivered via a pipe from an LNG terminal, may be liquefied natural gas stored in a container or cylinder, or may be liquefied natural gas delivered from an area that can substantially supply an air separation unit (ASU). The feed nitrogen gas (FG) introduced into the LNG heat exchanger (E3) may be a nitrogen-enriched gas derived from an air separation unit (ASU). The nitrogen-enriched gas is, for example, a high-purity nitrogen gas having a nitrogen concentration of 90% or more, preferably 94% or more, or a so-called pure nitrogen gas of 95% or more.

[0008] The nitrogen gas (FG) supplied to the LNG heat exchanger (E3) may be nitrogen gas that has been subjected to at least one heat exchange treatment and at least one compression treatment. The liquid nitrogen production system (1) or the air separation unit (ASU) may include a heat exchanger (E1) that exchanges heat with (cools) nitrogen gas, a first compressor (21) that compresses the nitrogen gas thereafter, and a second compressor (22) that compresses the nitrogen gas that has been compressed by the first compressor (21) and then heat exchanged with (cooled by) the heat exchanger (E1). The liquid nitrogen production system (1) or the air separation unit (ASU) may include a piping line (L1) for sending the nitrogen gas compressed by the second compressor (22) and heat-exchanged in the heat exchanger (E1) to the LNG heat exchanger (E3), then to the heat exchanger (E1) and / or the heat source (E4), and again to the LNG heat exchanger (E3). The supply nitrogen gas (FG) may be a gas obtained by combining nitrogen gas compressed by the second compressor (22), introduced into the LNG heat exchanger (E3) and cooled, sent to the recycle heat exchanger (E2) and heat-exchanged (warmed), a part of which is heat-exchanged (warmed) in the heat exchanger (E1), and the rest of which is heated by a heat source (E4) (e.g., a brine unit). The recycle heat exchanger (E2) and the heat exchanger (E1) may be physically configured as a single heat exchanger (E12), or may be configured as separate units, and may have piping routes according to the heat exchange ratio. The LNG heat exchanger, the recycle heat exchanger (E2), and the heat exchanger (E1) may be physically configured as a single heat exchanger (E30), or may be configured as separate units, and may have piping routes according to the heat exchange ratio. The liquid nitrogen separated in the first separator (14) may be removed as a liquid nitrogen (LN2) product.

[0009] In the first separator (14), the second part gas (G12) may be cooled by the low-temperature nitrogen gas (G111). The liquid nitrogen production apparatus (1) comprises: The apparatus may include a subcooler (15) for cooling the liquid nitrogen (LN2) discharged from the first separator (14). The liquid nitrogen (LN2) cooled (subcooled) in the subcooler (15) may be extracted as a liquid nitrogen product. The system may include a branch path (L31) for extracting a portion of the liquid nitrogen (LN2) cooled by the subcooler (15), a second expansion valve (151) provided in the branch path (L31) for reducing the pressure (expanding) of the liquid nitrogen (LN2), and a second separator (152) into which the nitrogen in a gas-liquid mixed state reduced in pressure by the second expansion valve (151) is introduced. From the second separator (152), the liquid component may be sent to the subcooler (15) and evaporated in the subcooler (15), and the gas component may be returned to the second separator (152). This evaporation energy is utilized in the subcooler (15). From the second separator (152), the gas component may be sent to the subcooler (15) and function as a refrigerant for the subcooler (15), and then sent to the recycle heat exchanger (E2, E12, E30) and function as a refrigerant (giving up refrigeration) and sent to the first compressor (21). The gas component separated in the first separator (14) may be sent to the recycle heat exchanger (E2, E12, E30) to function as a refrigerant (to release refrigeration), and then sent to the second compressor (22).

[0010] The expansion turbine (12) Booster (11) This allows for the effective generation of high-pressure nitrogen gas (e.g., 4.0 MPa to 5.0 MPa) from medium-pressure nitrogen gas (e.g., 2.0 MPa to 3.0 MPa) in a temperature range of approximately -158°C to -120°C, with less power than conventional methods.

[0011] The liquid nitrogen production apparatus (1) comprises: Passing through the LNG heat exchanger (E3, E30), Booster (11) a first temperature monitoring unit (16) for monitoring the temperature of the medium-pressure nitrogen gas (G0) sent to the The compression ratio control unit (17) controls the temperature (rise or fall) measured by the first temperature monitoring unit (16). Booster (11)and a control unit that controls the compression ratio (supply pressure / discharge pressure) to be constant. The control unit may include a compression ratio control unit (17) for changing (increasing or decreasing) the amount of intake gas or the amount of discharge gas of the first compressor (21) and / or the second compressor (22). The liquid nitrogen production apparatus (1) comprises: a second temperature monitoring unit (161) for monitoring the temperature of the liquefied natural gas (LNG) at the inlet of the heat exchanger (E3, E30) and / or at the outlet of the heat exchanger after using the refrigerant; In response to the temperature (rise or fall) of the inlet and / or outlet measured by the second temperature monitoring unit (161), Booster (11) and a control unit that controls the compression ratio (supply pressure / discharge pressure) to be constant. The control unit may include a compression ratio control unit (17) for changing (increasing or decreasing) the amount of intake gas or the amount of discharge gas of the first compressor (21) and / or the second compressor (22). Both the first and second temperature monitoring units (16, 161) may be provided, and the compression ratio control unit (17) may perform control based on either one of the temperature results or a comprehensive evaluation of both the temperature results. The amount of intake gas or discharge gas may be controlled by controlling a flow rate regulator provided in piping on the inlet or outlet side of the compressor or heat exchanger, or by controlling the intake valve of the compressor. If the temperatures at the inlet and outlet are measured, the temperature difference between the inlet and outlet may be monitored. This means: Booster (11) feedforward control of the intake or discharge volume of the compressor in response to fluctuations in the temperature of the nitrogen gas or the liquefied natural gas (LNG) sent to the Booster (11) By maintaining a constant compression ratio, the amount of liquid nitrogen produced does not fluctuate greatly, making it possible to flexibly respond to continuous production.

[0012] The liquid nitrogen production apparatus (1) comprises: From the LNG heat exchanger (E3, E30) Booster (11)It may further comprise a preheat exchanger (E5) for cooling the nitrogen gas sent to The preliminary heat exchanger (E5) Booster (11) The medium pressure nitrogen gas (G0) sent to the reactor may be cooled to a temperature higher than the critical temperature of nitrogen gas (-147°C).

[0013] Another invention of the liquid nitrogen production device (1) is as follows: LNG piping (L0) for transporting LNG, An LNG heat exchanger (E30) that uses the LNG sent through the LNG pipe (L0) as cold energy, A first pipe (L1) that sends low-pressure nitrogen gas (LPN2Gas) to the LNG heat exchanger (E30); a first compressor (21) that compresses nitrogen gas that has passed through at least a part of the LNG heat exchanger (E30); a second compressor (22) that further compresses the nitrogen gas compressed by the first compressor (21) after the nitrogen gas has passed through at least a part of the LNG heat exchanger (E30); The nitrogen gas (G1) compressed by the second compressor (22) at a first pressure (for example, 2.0 MPa to 3.0 MPa) passes through an LNG heat exchanger (E30) (for example, cooled to a temperature higher than the critical temperature of nitrogen gas (-147°C)), and is then compressed to a second pressure (for example, 4.0 MPa to 5.0 MPa) higher than the first pressure, and the high-pressure nitrogen gas (G1) is discharged. Booster (11) and, The aforementioned Booster (11) The high-pressure nitrogen gas (G1) discharged from the LNG heat exchanger (E30) is sent to an LNG heat exchanger (E30), and a first partial gas (G11) which is a part of the high-pressure nitrogen gas (G1) that has passed through the LNG heat exchanger (E30) is introduced into an expansion turbine (12) which expands the first partial gas (G11) to a third pressure (e.g., 0.5 MPa to 1.0 MPa) which is lower than the first pressure (e.g., 2.0 MPa), and discharges low-temperature nitrogen gas (G111) (partially liquefied or at a temperature near the liquefaction point), and the expansion turbine (12) Booster (11) Drives a first expansion valve (13) that reduces the pressure of a second portion gas (G12) other than the first portion gas (G11) of the high-pressure nitrogen gas (G1) after passing through at least a portion of the LNG heat exchanger (E30) (to the same or approximately the same as a third pressure (e.g., 0.5 MPa)); a first separator (14) into which the second partial gas (G12) decompressed by the first expansion valve (13) and the low-temperature nitrogen gas (G111) discharged from the expansion turbine (12) are introduced, and which separates the nitrogen gas (N2G) from the liquid nitrogen (LN2); a subcooler (15) for cooling the liquid nitrogen (LN2) extracted from the first separator (14); The system includes a branch path (L31) for extracting a portion of liquid nitrogen from the liquid nitrogen (LN2) cooled by the subcooler (15), a second expansion valve (151) provided in the branch path (L31) for reducing the pressure (expanding) of the liquid nitrogen (LN2), and a second separator (152) into which the nitrogen in a gas-liquid mixed state reduced in pressure by the second expansion valve (151) is introduced. The liquid component may be sent from the second separator (152) to the subcooler (15) and evaporated in the subcooler (15), and the gas component may be returned to the second separator (152). This evaporation energy is utilized in the subcooler (15). The gas component may be sent from the second separator (152) to the subcooler (15) and function as a refrigerant for the subcooler (15), and then sent to the LNG heat exchanger (E30) and function as a refrigerant (giving up refrigeration) and sent to the first compressor (21). The gas component separated in the first separator (14) may be sent to an LNG heat exchanger (E30) to function as a refrigerant (to give off refrigeration), and then sent to the second compressor (22). The liquid nitrogen production apparatus (1) comprises: Passing through the LNG heat exchanger (E30), Booster (11) a first temperature monitoring unit (16) for monitoring the temperature of the medium-pressure nitrogen gas (G0) sent to the The compression ratio control unit (17) controls the temperature (rise or fall) measured by the first temperature monitoring unit (16). Booster (11) and a control unit that controls the compression ratio (supply pressure / discharge pressure) to be constant. The control unit may include a compression ratio control unit (17) for changing (increasing or decreasing) the amount of intake gas or the amount of discharge gas of the first compressor (21) and / or the second compressor (22).

[0014] Another invention of the liquid nitrogen production method is an LNG cooling process in which the supply nitrogen gas (FG) at a first pressure is cooled using the cold energy of liquefied natural gas (LNG) at a predetermined temperature range; The supply nitrogen gas (G0) cooled in the LNG cooling step is cooled to a second pressure higher than the first pressure, Booster (11) a high-pressure nitrogen gas generation process in which high-pressure nitrogen gas (G1) is generated by compressing the nitrogen gas; a first cooling step of cooling the high-pressure nitrogen gas (G1) generated in the high-pressure nitrogen gas generation step; A part (G11) of the high-pressure nitrogen gas (G1) cooled in the first cooling step is Booster (11) a first expansion step in which the gas is expanded by an expansion turbine (12) that drives the a second cooling step of further cooling the remaining gas (G12) other than the partial gas (G11) of the high-pressure nitrogen gas (G1) cooled in the first cooling step; a first depressurization step of depressurizing the remaining gas (G12) cooled in the second cooling step; and a gas-liquid separation step in which the remaining gas (G12) decompressed in the first decompression step and the partial gas (G111) expanded in the first expansion step are introduced into a first separator (14) to perform gas-liquid separation.

[0015] The liquid nitrogen production method includes: The method may further include a pre-cooling step of further cooling the nitrogen gas supply after the LNG cooling step, and the high-pressure nitrogen gas generating step may compress the nitrogen gas supply cooled in the pre-cooling step.

[0016] The liquid nitrogen production method includes: The method may include a product removal step of removing the liquid nitrogen separated in the gas-liquid separation step as a product. The liquid nitrogen production method includes: a subcooling step of cooling the liquid nitrogen separated in the gas-liquid separation step; The method may include a product removal step of removing the liquid nitrogen cooled in the subcooling step as a product. The liquid nitrogen production method includes: a second depressurization step of removing a portion of the liquid nitrogen cooled in the subcooling step and depressurizing the liquid nitrogen; The method may further include a refrigerant supply step in which evaporation energy obtained by evaporating the liquid component of the nitrogen in a gas-liquid mixed state decompressed in the second decompression step is utilized as a refrigerant for the subcooling step.

[0017] The liquid nitrogen production method includes: a first pretreatment step in which the nitrogen gas sent from the air separation unit is subjected to a first cooling treatment and a first compression treatment; a second pretreatment step in which a second cooling treatment and a second compression treatment are performed after the first pretreatment step, The first compression treatment of the first pretreatment step may compress both the gas component used as the refrigerant in the refrigerant supply step and the nitrogen gas cooled in the first cooling treatment, and / or The second compression treatment of the second pretreatment step may compress both the gas component separated in the gas-liquid separation step and the gas component cooled in the second cooling treatment.

[0018] The liquid nitrogen production method includes: In the high-pressure nitrogen gas generating step, Booster (11) a temperature monitoring step of monitoring the temperature of the nitrogen gas (G0) introduced into the In response to the temperature (increase or decrease) measured in the temperature monitoring step, Booster (11) and a control step of controlling the compression ratio (supply pressure / discharge pressure) to be constant. The liquid nitrogen production method includes: a first pretreatment step in which the nitrogen gas sent from the air separation unit is subjected to a first cooling treatment and a first compression treatment; a second pretreatment step in which a second cooling treatment and a second compression treatment are performed after the first pretreatment step, The control process may include a compression ratio control process of changing (increasing or decreasing) the amount of nitrogen gas compressed (the intake amount introduced into the compressor, the discharge amount discharged from the compressor) in the first compression process and / or the second compression process. [Brief explanation of the drawings]

[0019] [Figure 1A] 1 is a diagram showing a liquid nitrogen production apparatus according to a first embodiment. [Figure 1B] FIG. 10 is a diagram showing a liquid nitrogen production apparatus according to a second embodiment. [Figure 1C] FIG. 10 is a diagram showing a liquid nitrogen production apparatus according to a third embodiment. [Figure 2] FIG. 10 is a diagram showing a liquid nitrogen production apparatus according to a fourth embodiment. [Figure 3] FIG. 10 is a diagram showing a liquid nitrogen production apparatus according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Several embodiments of the present invention will be described below. The embodiments described below are merely examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0021] (Embodiment 1) A liquid nitrogen production apparatus 1 according to the first embodiment will be described with reference to FIG. 1A. The liquid nitrogen production apparatus 1 includes a heat exchanger E1, a first compressor 21, a second compressor 22, a recycle heat exchanger E2, an LNG heat exchanger E3, a brine unit E4, Booster 11 , an expansion turbine 12, a first separator 14, and a subcooler 15.

[0022] Low-pressure nitrogen gas (LPN2G) with a high nitrogen concentration is sent via pipe L1 from a general air separation unit, tank, supply pipe, etc. to this device 1. The low-pressure nitrogen gas (LPN2G) is, for example, at 40°C and 1.15 barA. The low-pressure nitrogen gas (LPN2G) is sent to a heat exchanger E1 to be cooled, and then sent to a first compressor 21 to be compressed to, for example, 5 barA. It is then sent to a heat exchanger E1 to be cooled, and then sent to a second compressor 22 to be compressed to, for example, 20 barA, to become medium-pressure nitrogen gas (MPN2G). The medium-pressure nitrogen gas (MPN2G) is adjusted to a first pressure (for example, 2.0 to 3.0 MPa).

[0023] The medium pressure nitrogen gas (MPN2G) is sent to the LNG heat exchanger E3, whose refrigerant is, for example, liquefied natural gas (LNG) at a temperature of about -158°C to -120°C. The medium-pressure nitrogen gas (MPN2G) is cooled in the LNG heat exchanger E3, passes through part of the recycle heat exchanger E2, and part of it is sent to the main heat exchanger E1 via pipe L1b to release cold, and the rest is sent to the brine unit E4 via pipe L1a to be heated, and then these two parts are combined and sent back to the LNG heat exchanger E3 to be cooled.

[0024] The cooled medium pressure nitrogen gas G0 is delivered via pipe L2. Booster 11 is sent to and compressed. Booster 11 The medium pressure nitrogen gas becomes high pressure nitrogen gas G1 of, for example, 50 barA. The high pressure nitrogen gas G1 is adjusted to a second pressure (for example, 4.0 MPa to 5.0 MPa) higher than the first pressure. The high-pressure nitrogen gas G1 is sent to the recycle heat exchanger E2 via a pipe L2. Part of the high-pressure nitrogen gas G1 is extracted midway through the recycle heat exchanger E2 via a branch pipe L21, and this extracted first portion gas G11 is sent to the expansion turbine 12. The expansion turbine 12 is Booster 11 is mechanically coupled to Booster 11 Provides driving force to

[0025] The first partial gas G11 is expanded in the expansion turbine 12 and decompressed to, for example, 5 barA, to become a partially liquefied or near-liquefying low-temperature nitrogen gas G111, which is sent to the first separator 14 via the pipe L21. On the other hand, the remaining second portion of the gas G12 other than the first portion of the gas G11 is sent to the first expansion valve 13 via the pipe L22 and is depressurized to, for example, 5 barA. The depressurized second portion of the gas G12 is sent to the first separator 14, where it comes into contact with low-pressure liquid nitrogen G111 and is partially liquefied.

[0026] The gas component (N2G) in the gas phase of the first separator 14 is sent to the recycle heat exchanger E2 via pipe L41 to release the cold, and then sent to the second compressor 22, where it is compressed together with the nitrogen gas that was compressed in the first compressor 21 and passed through the heat exchanger E1.

[0027] The liquid nitrogen (LN2) accumulated in the liquid phase of the first separator 14 is sent to the subcooler 15 via the pipe L3, where it is cooled, and then extracted as a product. The pipe L3 may be provided with a gate valve or a flow control valve V3. A branch pipe L31 branching off from the pipe L3 is provided with a second expansion valve 151. A portion of the liquid nitrogen (LN2) is sent through this branch pipe L31, decompressed by the second expansion valve 151, and sent to a second separator 152 in a gas-liquid mixed state.

[0028] A first portion of the lower part of the second separator 152 and a first portion of the lower part of the subcooler 15 are connected by a pipe L33, and the liquid component is fed thereto. The liquid component evaporates in the subcooler 15, and the gas component returns to the second separator 152 via a pipe L34. This evaporation energy is utilized in the subcooler 15. From the second separator 152, the gas component is sent to the subcooler 15 via a pipe L32 to function as a refrigerant for the subcooler 15, then sent to the recycle heat exchanger E2 via a pipe L42 to function as a refrigerant (discharges refrigeration), and then sent to the first compressor 21 to be compressed together with the nitrogen gas that has passed through the heat exchanger E1. The second separator 152 may be provided with a mechanism for gasifying the liquid component.

[0029] The first temperature monitoring unit 16 monitors the LNG passing through the LNG heat exchanger E3, Booster 11 The first temperature monitoring unit 16 monitors the temperature of the medium-pressure nitrogen gas G0 sent to the compression ratio control unit 17. The first temperature monitoring unit 16 may have a temperature sensor that measures the temperature, a memory that stores the measurement results, and a transmission unit (which may be wireless communication means or wired communication means) that transmits the measurement results to the compression ratio control unit 17. The compression ratio control unit 17, in response to the temperature measured by the first temperature monitoring unit 16 rising or falling by more than a threshold value based on a set value or a moving average temperature per unit time, Booster 11 The amount of intake gas of the second compressor 22 is increased or decreased so as to maintain a constant compression ratio (supply pressure / discharge pressure) of the second compressor 22. For example, the intake valve on the inlet side of the second compressor 22 is controlled so as to increase the amount of intake gas in response to an increase in temperature, and the intake valve on the inlet side of the second compressor 22 is controlled so as to decrease the amount of intake gas in response to a decrease in temperature. Booster 11 The compression ratio (supply pressure / discharge pressure) is controlled to maintain the second pressure (for example, 4.0 MPa to 5.0 MPa).

[0030] (Embodiment 2) The liquid nitrogen production apparatus 1 of the second embodiment will be described with reference to FIG. 1B. The following mainly describes components different from those of the first embodiment, and the description of the same components as those of the first embodiment will be omitted. In the second embodiment, the heat exchanger E1 and the recycle heat exchanger E2 are configured as a single heat exchanger E12. In addition, the first temperature monitoring unit 16 is Booster 11 The layout and piping of each component are the same.

[0031] (Embodiment 3) The liquid nitrogen production apparatus 1 of the third embodiment will be described with reference to FIG. 1C. The following mainly describes components that are different from those of the first embodiment, and the description of the same components as those of the first embodiment will be omitted. In the third embodiment, a second temperature monitoring unit 161 is provided instead of the first temperature monitoring unit 16. The second temperature monitoring unit 161 monitors the temperature of the liquefied natural gas (LNG) at the heat exchanger inlet that is introduced into the LNG heat exchanger E3. The second temperature monitoring unit 161 may include a temperature sensor that measures the temperature, a memory that stores the measurement results, and a transmitter (which may be wireless communication means or wired communication means) that transmits the measurement results to the compression ratio control unit 17. The compression ratio control unit 17, in response to the temperature measured by the second temperature monitoring unit 161 rising or falling by more than a threshold value based on a set value or a moving average temperature per unit time, Booster 11 The amount of intake gas of the second compressor 22 is increased or decreased so as to maintain a constant compression ratio (supply pressure / discharge pressure) of the second compressor 22. For example, the intake valve on the inlet side of the second compressor 22 is controlled so as to increase the amount of intake gas in response to an increase in temperature, and the intake valve on the inlet side of the second compressor 22 is controlled so as to decrease the amount of intake gas in response to a decrease in temperature. Booster 11 The compression ratio (supply pressure / discharge pressure) is controlled to maintain the second pressure (for example, 4.0 MPa to 5.0 MPa). In the third embodiment, the heat exchanger E1 and the recycle heat exchanger E2 may be configured as a single heat exchanger E12.

[0032] (Embodiment 4) The liquid nitrogen production apparatus 1 of the fourth embodiment will be described with reference to Fig. 2. The description will focus on components different from those of the second embodiment, and the description of the same components as those of the second embodiment will be omitted. The spare heat exchanger E5 is connected to the LNG heat exchanger E3. Booster 11 The spare heat exchanger E5 is located in the piping line L2 between the Booster 11 The medium-pressure nitrogen gas G0 sent to the reactor is cooled to a temperature higher than the critical temperature of nitrogen gas (-147°C).

[0033] The drive of the auxiliary heat exchanger E5 may be turned on / off depending on the temperature measured by the first temperature monitoring unit 16 or the second temperature monitoring unit 161 (not shown). Alternatively, the air may be passed through a bypass path without passing through the auxiliary heat exchanger E5. Booster 11 The information may be configured to be sent to The first temperature monitoring unit 16 may be disposed downstream of the preliminary heat exchanger E5. In the fourth embodiment, the single heat exchanger E12 may be configured as separate units consisting of the heat exchanger E1 and the recycle heat exchanger E2, as in the first embodiment.

[0034] (Embodiment 5) A liquid nitrogen production apparatus 1 of embodiment 5 will be described with reference to Fig. 3. In embodiment 5, the LNG heat exchanger, heat exchanger, and recycle heat exchanger are configured as a single LNG heat exchanger E30. The following description will focus on components that are different from embodiment 2, and descriptions of components that are the same as embodiment 2 will be omitted or will be briefly described.

[0035] The LNG is sent to the LNG heat exchanger E30 via the LNG pipe L0, and a portion of the LNG leaves the LNG heat exchanger E30 and is sent to the brine unit E4 where it is warmed. The remaining LNG leaves the LNG heat exchanger E30 via the pipe L0b, where it is combined with the LNG that has been warmed in the brine unit E4 and is discharged as natural gas.

[0036] The low-pressure nitrogen gas (LPN2Gas) sent from the air separation unit is sent to the LNG heat exchanger E30 via the first pipe L1. The low-pressure nitrogen gas passes through at least a portion of the LNG heat exchanger E30 and is sent to the first compressor 21 where it is compressed. The nitrogen gas compressed by the first compressor 21 is then sent to the LNG heat exchanger E30, passes through at least a portion of it, and is then sent to the second compressor 22 where it is compressed. The nitrogen gas (G1) compressed by the second compressor 22 at a first pressure (for example, 2.0 MPa to 3.0 MPa) passes through the LNG heat exchanger E30 (for example, is cooled to a temperature higher than the critical temperature of the nitrogen gas (-147°C)), and then flows through the pipe L2. Booster 11 will be sent to.

[0037] Booster 11 The pump 100 compresses and discharges high-pressure nitrogen gas (G1) to a second pressure (for example, 4.0 MPa to 5.0 MPa) higher than the first pressure. Booster 11The high-pressure nitrogen gas (G1) discharged from the LNG heat exchanger E30 is sent to the LNG heat exchanger E30. A first partial gas (G11), which is a part of the high-pressure nitrogen gas (G1) that has passed through a part of the LNG heat exchanger E30, is sent to the expansion turbine 12. The expansion turbine 12 expands the first partial gas (G11) to a third pressure (e.g., 0.5 MPa to 1.0 MPa) that is lower than the first pressure (e.g., 2.0 MPa), and discharges low-temperature nitrogen gas (G111) (partially liquefied or at a temperature near the liquefaction point). The expansion turbine 12 Booster 11 Drives.

[0038] A second portion gas (G12) other than the first portion gas (G11) of the high-pressure nitrogen gas (G1) passes through at least a part of the LNG heat exchanger E30, and then is sent to the first expansion valve 13 via a pipe L22. In the first expansion valve 13, the second portion gas (G12) is decompressed to a pressure equal to or approximately equal to a third pressure (e.g., 0.5 MPa). The second portion gas (G12) decompressed by the first expansion valve 13 and the low-temperature nitrogen gas (G111) discharged from the expansion turbine 12 are sent to the first separator 14. In the first separator 14, they are separated into nitrogen gas (N2G) and liquid nitrogen (LN2).

[0039] The liquid nitrogen (LN2) extracted from the first separator 14 is sent to the subcooler 15 and cooled. A portion of the liquid nitrogen (LN2) cooled in the subcooler 15 is sent to the second expansion valve 151 via the branch path L31 and reduced in pressure. The reduced-pressure liquid nitrogen (LN2) is sent to the second separator 152. The liquid component is sent from the second separator 152 to the subcooler 15 and evaporated in the subcooler 15, and the gas component is returned to the second separator 152. The gas component is sent from the second separator 152 to the subcooler 15, and then sent to the LNG heat exchanger E30 and to the first compressor 21. The gas component separated in the first separator 14 is sent to the LNG heat exchanger E30 and to the second compressor 22.

[0040] The first temperature monitoring unit 16 passes through the LNG heat exchanger E30, Booster 11The compression ratio control unit 17 monitors the temperature of the medium-pressure nitrogen gas (GO) sent to the first temperature monitoring unit 16. The compression ratio control unit 17 controls the temperature (rise or fall) measured by the first temperature monitoring unit 16. Booster 11 The amount of intake gas of the second compressor 22 is changed (increased or decreased) so as to keep the compression ratio (supply pressure / discharge pressure) constant.

[0041] (Modifications of Embodiments 1 to 5) Although the brine unit E4 is provided in the first to fifth embodiments, the brine unit E4 may be omitted. The brine unit E4 may use brine supplied from a brine device used in an air separation plant. Each piping line may be provided with a valve (such as a gate valve, a flow control valve, or a pressure control valve) as needed. Also, each piping line may be provided with a pressure regulator, a flow control device, or the like, to regulate the pressure or flow rate.

[0042] (Liquid nitrogen production method) The liquid nitrogen production method can be appropriately adopted in the production apparatuses of the above-mentioned embodiments 1 to 5, and includes the following steps. an LNG cooling process in which the supply nitrogen gas (FG) at a first pressure is cooled using the cold energy of liquefied natural gas (LNG) at a predetermined temperature range; The supply nitrogen gas (G0) cooled in the LNG cooling step is cooled to a second pressure higher than the first pressure, Booster (11) a high-pressure nitrogen gas generation process in which high-pressure nitrogen gas (G1) is generated by compressing the nitrogen gas; a first cooling step of cooling the high-pressure nitrogen gas (G1) generated in the high-pressure nitrogen gas generation step; A part (G11) of the high-pressure nitrogen gas (G1) cooled in the first cooling step is Booster (11) a first expansion step in which the gas is expanded by an expansion turbine (12) that drives the a second cooling step of further cooling the remaining gas (G12) other than the partial gas (G11) of the high-pressure nitrogen gas (G1) cooled in the first cooling step; a first depressurization step of depressurizing the remaining gas (G12) cooled in the second cooling step; a gas-liquid separation step in which the remaining gas (G12) decompressed in the first decompression step and the partial gas (G111) expanded in the first expansion step are introduced into a first separator (14) to perform gas-liquid separation; a subcooling step of cooling the liquid nitrogen separated in the gas-liquid separation step; a product removal step of removing the liquid nitrogen cooled in the subcooling step as a product; a second depressurization step of removing a portion of the liquid nitrogen cooled in the subcooling step and depressurizing the liquid nitrogen; and a refrigerant supplying step in which evaporation energy obtained by evaporating the liquid component of the nitrogen in a gas-liquid mixed state decompressed in the second decompression step is utilized as a refrigerant for the subcooling step.

[0043] In addition, the liquid nitrogen production method is a first pretreatment step in which the nitrogen gas sent from the air separation unit is subjected to a first cooling treatment and a first compression treatment; a second pretreatment step in which a second cooling treatment and a second compression treatment are performed after the first pretreatment step, The first compression treatment of the first pretreatment step may compress both the gas component used as the refrigerant in the refrigerant supply step and the nitrogen gas cooled in the first cooling treatment, and / or The second compression treatment of the second pretreatment step may compress both the gas component separated in the gas-liquid separation step and the gas component cooled in the second cooling treatment.

[0044] (Example) An example of a simulation performed using the configuration of embodiment 2 (FIG. 1B) is shown. The temperature of the LNG sent to the LNG heat exchanger E3 was set to -150°C. Low-pressure nitrogen gas from the air separation unit was supplied at 1.15 barA, 40°C, and 44,500 Nm 3 / h. The low-pressure nitrogen gas was introduced into a single heat exchanger E12 and cooled to -88.3°C. It was then combined with nitrogen gas sent from subcooler 15 and warmed in the single heat exchanger E12, and the combined gas was compressed to 5 barA in a first compressor 21. It was then cooled again in the single heat exchanger E12 and combined with nitrogen gas sent from separator 14 and warmed in the single heat exchanger E12. The combined gas was compressed to 21 barA in a second compressor 22. The compressed nitrogen gas was cooled to -107°C by heat exchange with LNG in LNG heat exchanger E3. A portion of the cooled nitrogen gas was heated to 40°C in the single heat exchanger E12, and the remainder was heated in a brine unit E4. These were combined, and the combined nitrogen gas was again cooled to -140°C in the LNG heat exchanger E3. The cooled nitrogen gas is Booster 11 The nitrogen gas was compressed to 50 barA in a single heat exchanger E12. After that, it was cooled to -110°C in a single heat exchanger E12, and a part of it was expanded to 5 barA in an expansion turbine 12. The remaining nitrogen gas that was not sent to the expansion turbine 12 was further cooled in the single heat exchanger E12, and after being decompressed to 5 barA by a first expansion valve 13, it was introduced into a separator 14 and separated into gas and liquid. The liquid nitrogen in the separator 14 was subcooled in a subcooler 15 and then expanded to 44,500 Nm 3 / h was discharged as a product, and the remaining liquid nitrogen was decompressed by the second expansion valve 152 and then supplied as a refrigerant to the subcooler 15 via the second separator 152. As mentioned above, the gaseous nitrogen gas from the subcooler 15 was further sent to the single heat exchanger E12 where it released refrigeration before being introduced into the first compressor 21. [Explanation of symbols]

[0045] 1. Liquid nitrogen production equipment 11 booster 12 Expansion turbine 13 First expansion valve 14 First separator 15 Subcooler 151 Second expansion valve 152 Second separator 21 First compressor 22 Second compressor E1 heat exchanger E2 Recycling Heat Exchanger E3 LNG heat exchanger E4 Brine Unit E5 spare heat exchanger E12 Single Heat Exchanger E30 LNG heat exchanger

Claims

1. an LNG heat exchanger that cools the supply nitrogen gas at a first pressure by utilizing cold energy from liquefied natural gas within a predetermined temperature range; a booster that compresses the supply nitrogen gas cooled by the LNG heat exchanger to a second pressure higher than the first pressure and discharges high-pressure nitrogen gas; a recycle heat exchanger that cools the high-pressure nitrogen gas discharged from the booster by heat exchange; an expansion turbine that drives the booster, into which a first partial gas that is a part of the high-pressure nitrogen gas that has passed through a part of the recycle heat exchanger is introduced, and which expands and cools the first partial gas to a third pressure that is lower than the first pressure, and discharges low-temperature nitrogen gas; a first expansion valve for reducing the pressure of a second portion gas other than the first portion gas in the high-pressure nitrogen gas after passing through the recycle heat exchanger; a first separator into which the second partial gas decompressed by the first expansion valve and the low-temperature nitrogen gas discharged from the expansion turbine are introduced, and which separates the nitrogen gas from the liquid nitrogen; A liquid nitrogen production device comprising:

2. a heat exchanger that cools the nitrogen gas by heat exchange; a first compressor that compresses the nitrogen gas cooled by the heat exchanger; a second compressor that compresses the nitrogen gas compressed by the first compressor and then sent to the heat exchanger and cooled to a first pressure; a piping line for sending the nitrogen gas at the first pressure compressed by the second compressor to the LNG heat exchanger, then to the heat exchanger and / or a heat source, and again to the LNG heat exchanger as feed nitrogen gas; The liquid nitrogen production apparatus according to claim 1 , comprising:

3. a subcooler that cools the liquid nitrogen extracted from the first separator; a branch path for extracting a portion of the liquid nitrogen from the liquid nitrogen cooled by the subcooler; a second expansion valve provided in the branch path to reduce the pressure of the portion of the liquid nitrogen; a second separator into which the liquid nitrogen in a gas-liquid mixed state that has been decompressed by the second expansion valve is introduced; The liquid component of the part of the liquid nitrogen introduced into the second separator is sent to the subcooler. The liquid nitrogen production apparatus according to any one of claims 1 and 2.

4. a first temperature monitoring unit that monitors the temperature of the nitrogen gas supply that passes through the LNG heat exchanger and is sent to the booster; and / or a second temperature monitoring unit that monitors the temperature of the liquefied natural gas at an inlet of the heat exchanger supplied to the LNG heat exchanger and / or at an outlet of the heat exchanger after use as a refrigerant; a control unit that controls the compression ratio of the booster to be constant in accordance with the temperature measured by the first or second temperature monitoring unit; The liquid nitrogen production apparatus according to claim 1 , further comprising:

5. 5. The liquid nitrogen production apparatus according to claim 1, further comprising a preheat exchanger that cools the nitrogen gas supplied from the LNG heat exchanger to the booster.

6. A liquid nitrogen manufacturing apparatus described in any one of claims 1 to 5, wherein the recycling heat exchanger and the heat exchanger are composed of a single heat exchanger.

7. A liquid nitrogen production apparatus as described in any one of claims 1 to 5, wherein the LNG heat exchanger, the recycle heat exchanger, and the heat exchanger are composed of a single heat exchanger.

8. an LNG cooling step of cooling the supply nitrogen gas at a first pressure using cold energy from liquefied natural gas at a predetermined temperature range; a high-pressure nitrogen gas generating step of compressing the supply nitrogen gas cooled in the LNG cooling step by a booster to a second pressure higher than the first pressure to generate high-pressure nitrogen gas; a first cooling step of cooling the high-pressure nitrogen gas generated in the high-pressure nitrogen gas generating step; a first expansion step in which a portion of the high-pressure nitrogen gas cooled in the first cooling step is expanded in an expansion turbine that drives the booster; a second cooling step of further cooling the remaining gas other than the partial gas of the high-pressure nitrogen gas cooled in the first cooling step; a first depressurization step of depressurizing the remaining gas cooled in the second cooling step; a gas-liquid separation step of separating the remaining gas decompressed in the first decompression step and the low-temperature nitrogen gas expanded in the first expansion step into gas-liquid separation and separating the gas into nitrogen gas and liquid nitrogen; A method for producing liquid nitrogen, comprising:

9. a temperature monitoring step of monitoring the temperature of the nitrogen gas supply introduced into the booster; a control step of controlling the compression ratio of the booster to be constant in accordance with the temperature measured in the temperature monitoring step; 9. The method for producing liquid nitrogen according to claim 8, comprising:

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