Low-energy-consumption large and medium-sized high-nitrogen device

Abstract

The invention discloses a low-energy-consumption large and medium-sized high-nitrogen device, which belongs to the technical field of high-nitrogen devices and comprises a main heat exchanger, an expansion machine, a pressure tower, a low-pressure tower, a pressure tower condensation evaporator, a low-pressure tower condensation evaporator, a liquid nitrogen pump and a subcooler. Liquid air steam of a pressure tower condensation evaporator is reheated by a main heat exchanger, enters an expansion machine to be expanded and then enters a low-pressure tower, so that the pressure of an inlet and an outlet of the expansion machine is improved, the volume flow of the expansion machine and the pressure of the low-pressure tower are remarkably reduced, and the size of an impeller of the expansion machine is greatly reduced; the tower bottom liquid air of the pressure tower and the tower bottom oxygen-enriched liquid air of the low-pressure tower are supercooled by the heat exchanger, and the tower bottom liquid air of the pressure tower is partially cooled and then fed into the low-pressure tower to continue to participate in rectification, so that the extraction rate of product nitrogen is reduced while the cooling capacity loss of the device is reduced, and the unit energy consumption is reduced; liquid nitrogen in the low-pressure tower is pressurized to the upper part of the pressure tower instead of the top of the pressure tower through a pump, so that an ultra-pure nitrogen product is obtained, and the ultra-pure nitrogen gas is very suitable for downstream enterprise gas sensitive to copper and zinc elements.

Description

Technical Field

[0001] The invention relates to a high nitrogen device, in particular to a large and medium-sized high nitrogen device with low energy consumption, and belongs to the technical field of high nitrogen devices. Background Art

[0002] Certain chemical, electronics, semiconductor, photovoltaic, liquid crystal panel and other industries often require a large amount of nitrogen, with little or no demand for oxygen. Under normal operating conditions, there is also little demand for liquid. Due to high reliability requirements, dual-tower + pump high nitrogen devices are often used.

[0003] However, the large and medium-sized high nitrogen devices in the prior art have low top oxygen-rich oxygen pressure, large volume flow, and poor energy utilization, resulting in energy loss. Therefore, a low-energy consumption large and medium-sized high nitrogen device is designed to solve the above problem. Summary of the invention

[0004] The object of the present invention is to provide a medium-sized and large-scale high-nitrogen device with low energy consumption, which utilizes the pressure difference between the pressure tower condenser evaporator and the low-pressure tower for expansion to provide the cooling capacity of the system. Since the pressure of the pressure tower condenser evaporator is relatively high, the volume flow rate is greatly reduced, the diameter of the expander impeller is significantly reduced, and the stability and efficiency of the expander are improved. At the same time, the operating pressure of the low-pressure tower is reduced, which is more conducive to distillation and improves the extraction rate of the device.

[0005] Secondly, the cold capacity of oxygen-rich air or nitrogen is recovered by supercooling of pressurized liquid air and low-pressure liquid air, which reduces the liquefaction rate of the air entering the tower and brings the cold capacity to the top of the distillation tower. At the same time, part of the supercooled pressurized liquid air enters the low-pressure tower to participate in distillation, reducing the excess cold capacity of the device, improving the nitrogen extraction rate and reducing the unit energy consumption.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A low-energy consumption large and medium-sized high-nitrogen device includes a main heat exchanger, an expander, a pressure tower, a pressure tower condenser evaporator, a low-pressure tower, a low-pressure tower condenser evaporator, a liquid nitrogen pump, and a subcooler. The device includes the following steps:

[0008] S100: The room temperature purified air is cooled by the main heat exchanger to become low temperature purified air and then enters the lower part of the pressure tower to participate in distillation.

[0009] S200: pressure liquid air is obtained at the bottom of the pressure tower, and pressure nitrogen is obtained at the top. The pressure liquid air is supercooled by the main heat exchanger and is divided into two parts: one part of the pressure liquid air enters the pressure tower condenser evaporator as a cold source, and the other part of the pressure liquid air enters the low-pressure tower for distillation. The pressure nitrogen is divided into two parts: one part of the pressure nitrogen enters the pressure tower condenser evaporator as a heat source, and is condensed into liquid nitrogen as the reflux of the pressure tower, and the other part of the pressure nitrogen is reheated by the main heat exchanger and extracted as product nitrogen.

[0010] S300: The oxygen-enriched air obtained on the evaporation side of the condenser evaporator of the pressure tower enters the expansion end of the expander after being reheated by the main heat exchanger. The expanded oxygen-enriched air enters the lower part of the low-pressure tower to participate in distillation.

[0011] S400: low-pressure liquid air is obtained at the bottom of the low-pressure tower, and low-pressure nitrogen is obtained at the top. After the low-pressure liquid air is supercooled by the cooler, the supercooled low-pressure liquid air enters the low-pressure tower condenser evaporator as a cold source. The low-pressure nitrogen enters the low-pressure tower condenser evaporator as a heat source, and is condensed into low-pressure liquid nitrogen and is divided into two parts: one part of the liquid nitrogen is used as the reflux of the low-pressure tower, and the other part of the liquid nitrogen is pressurized by the liquid nitrogen pump into the upper part of the pressure tower.

[0012] S500: The oxygen-enriched air obtained on the evaporation side of the low-pressure tower condenser evaporator is reheated through a cooler and a main heat exchanger to obtain oxygen-enriched air at room temperature.

[0013] In one embodiment of the present application, in step S200, the main heat exchanger is provided with a pressure liquid-air subcooling section, and the pressure liquid air at the bottom of the pressure tower is connected to the liquid-air heat release channel of the main heat exchanger.

[0014] or

[0015] In step S200, the main heat exchanger is not provided with a pressure liquid-to-air subcooling section, and the pressure liquid air at the bottom of the pressure tower is connected to the liquid-to-air heat release channel of the subcooler.

[0016] In one embodiment of the present application, in step S200, the cooled pressurized liquid air is divided into two parts: one part of the pressurized liquid air enters the pressure tower condenser evaporator as a cold source, and the other part of the pressurized liquid air enters the low-pressure tower for distillation.

[0017] or

[0018] In step S200, all the cooled pressurized liquid air is sent to the condenser evaporator of the pressure tower as a cold source.

[0019] In one embodiment of the present application, in step S400, a subcooler is provided, and the low-pressure liquid air at the bottom of the low-pressure tower is connected to the low-pressure liquid air heat release channel of the subcooler. After subcooling, the low-pressure liquid air enters the condenser evaporator of the low-pressure tower as a cold source.

[0020] or

[0021] In step S400, no subcooler is provided, and the main heat exchanger is provided with a low-pressure liquid air subcooling section. The low-pressure liquid air at the bottom of the low-pressure tower is connected to the low-pressure liquid air heat release channel of the main heat exchanger. After subcooling, the low-pressure liquid air enters the condenser evaporator of the low-pressure tower as a cold source.

[0022] In one embodiment of the present application, in step S300, the oxygen-enriched air obtained on the evaporation side of the pressure tower condenser evaporator is reheated by the main heat exchanger and enters the expansion end of the expander, and the expanded oxygen-enriched air enters the lower part of the low-pressure tower to participate in distillation.

[0023] or

[0024] In step S300, the oxygen-enriched air obtained on the evaporation side of the condenser evaporator of the pressure tower is reheated through the cooler and the main heat exchanger respectively, and the reheated oxygen-enriched air enters the expansion end of the expander, and the expanded oxygen-enriched air enters the lower part of the low-pressure tower to participate in distillation.

[0025] In one embodiment of the present application, step S200 further includes extracting pressurized liquid nitrogen produced by liquefaction in the pressure tower condenser evaporator as a liquid nitrogen product.

[0026] and / or

[0027] Step S400 also includes extracting low-pressure liquid nitrogen produced by liquefaction in the condenser evaporator of the low-pressure tower as a liquid nitrogen product.

[0028] In one embodiment of the present application, step S400 further includes extracting oxygen-rich liquid air as a cold source in the condenser evaporator of the low-pressure tower for safe discharge.

[0029] In one embodiment of the present application, in step S400, part of the liquid nitrogen condensed by the condensation evaporator of the low-pressure tower is pressurized into pressurized liquid nitrogen by a liquid nitrogen pump and enters the upper part of the pressure tower.

[0030] or

[0031] In step S400, part of the liquid nitrogen condensed by the condenser evaporator of the low-pressure tower is pressurized by a liquid nitrogen pump into pressurized liquid nitrogen and enters the top of the pressure tower.

[0032] In one embodiment of the present application, in step S500: the oxygen-enriched air obtained on the evaporation side of the low-pressure tower condenser evaporator is reheated through a cooler and a main heat exchanger to obtain oxygen-enriched air at room temperature.

[0033] or

[0034] In step S500: the oxygen-enriched air obtained on the evaporation side of the low-pressure tower condenser evaporator is directly reheated through the main heat exchanger to obtain oxygen-enriched air at room temperature.

[0035] In one embodiment of the present application, an expander is also included: the expansion end inlet of the expander is oxygen-enriched air, the outlet is low-temperature oxygen-enriched air, and the expander is connected to the lower part of the low-pressure tower; the output end of the expander is a blower, a generator, an oil brake device, and a booster end. When it is a booster end, the nitrogen product exiting the main heat exchanger is pressurized.

[0036] Beneficial effects of the present invention:

[0037] The low-energy consumption large and medium-sized high-nitrogen device provided by the present invention adopts a simple method to solve the problem that the oxygen-rich gas pressure in large and medium-sized high-nitrogen devices is low and the volume flow is large, which is difficult to use. The impeller and pipeline size of the expander are greatly reduced. Due to the increase in the inlet and outlet pressure of the expander, the stability of the device is improved; and the liquid air and oxygen-rich liquid air are cleverly used to absorb the cold of various media by supercooling, further reducing the liquefaction rate of the air entering the pressure tower, and the cold is brought to the top, which is more conducive to distillation. A part of the liquid air enters the low-pressure tower to participate in distillation, increasing the nitrogen production and improving the nitrogen extraction rate. The low-pressure tower liquid nitrogen is used to enter the pressure tower for further distillation (also for washing) to avoid pollution or contaminant retention in the pump pressurization process and pipelines, and can also reduce the influence of unstable operation of the low-pressure tower on purity, thereby meeting ultra-high purity nitrogen and avoiding the influence of the copper-zinc alloy of the pump body on the product. It is very suitable for the parallel arrangement of two towers, which is convenient for the modularization of cold boxes. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. The present invention will be explained by way of examples and with reference to the drawings.

[0039] Figure 1 This is a typical low-energy consumption, high-nitrogen device in Example 1 in which a subcooler is separately provided.

[0040] Figure 2 This is a low energy consumption, high nitrogen device in Embodiment 2 which does not have a separate subcooler.

[0041] Figure 3 This is a low energy consumption, high purity, high nitrogen device with a subcooler according to Example 3.

[0042] Figure 4 This is a low-energy consumption, high-purity, high-nitrogen device in Example 4 that does not have a separate subcooler.

[0043] Figure 5 This is a low energy consumption, ultra-high purity, high nitrogen device equipped with a subcooler in Example 5.

[0044] Figure 6 This is a low-energy consumption ultra-high purity high nitrogen device with an optimized subcooler in Example 6.

[0045] Reference numerals:

[0046] E1-main heat exchanger, CE1-expander, C1-pressure tower, C2-low-pressure tower, K1-pressure tower condenser evaporator, K2-low-pressure tower condenser evaporator, E2-subcooler, NP1-liquid nitrogen pump, 11-normal temperature purified air, 12-low temperature purified air, 13-pressure liquid air, 14-subcooled pressure liquid air, 15-to pressure tower condenser evaporator liquid air, 16-to low-pressure tower lower liquid air, 17-pressure tower condenser evaporator rich air Oxygen air, 18-oxygen-enriched air before expansion, 19-oxygen-enriched air after expansion, 20-low-pressure liquid air, 21-subcooled low-pressure liquid air, 22 safe discharge of oxygen-enriched liquid air, 23-oxygen-enriched air from the condenser evaporator of the low-pressure tower, 24 oxygen-enriched air from the subcooler, 25-oxygen-enriched air at room temperature, 26-product liquid nitrogen from the low-pressure tower, 27-pressure liquid nitrogen after the liquid nitrogen pump, 28-product liquid nitrogen from the pressure tower, 29-low-temperature pressure nitrogen, 30-product nitrogen at room temperature. DETAILED DESCRIPTION

[0047] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0048] Combine the following Figures 1 to 6 The embodiments of the present invention are described in detail.

[0049] Example 1

[0050] like Figure 1 As shown, this embodiment provides a typical low-energy consumption high-nitrogen device with a separate subcooler, including a main heat exchanger (E1), an expander (CE1), a pressure tower (C1), a pressure tower condenser evaporator (K1), a low-pressure tower (C2), a low-pressure tower condenser evaporator (K2), a liquid nitrogen pump (NP1), and a subcooler (E2).

[0051] After the room temperature purified air 11 enters the main heat exchanger E1 and is cooled to low temperature purified air close to the dew point, the low temperature purified air 12 enters the pressure tower C1 for distillation, and pressure liquid air is obtained at the bottom of the pressure tower C1, and pressure nitrogen is obtained at the top. The pressure liquid air 13 is supercooled by the main heat exchanger E1 and is divided into two parts: one part of the pressure liquid air 15 enters the pressure tower condenser evaporator K1 as a cold source, and the other part of the pressure liquid air 16 enters the low pressure tower C2 for distillation. The pressure nitrogen obtained at the top of the tower is divided into two parts: one part enters the pressure tower condenser evaporator K1, and after being condensed into liquid nitrogen, one part can be used as pressure product liquid nitrogen 28, and the rest enters the pressure tower C1 as reflux liquid; the remaining pressure nitrogen 29 goes to the main heat exchanger E1 for reheating to obtain room temperature product nitrogen 30.

[0052] The oxygen-enriched air 17 obtained by evaporation in the pressure tower condenser evaporator K1 is reheated by the main heat exchanger E1 to obtain the oxygen-enriched air 18 before expansion, and then expanded by the expansion end E of the expander CE1 to obtain the expanded oxygen-enriched air 19 which enters the lower part of the low-pressure tower C2 to participate in distillation.

[0053] Low-pressure liquid air is obtained at the bottom of the low-pressure tower C2, and low-pressure nitrogen is obtained at the top. After the low-pressure liquid air 20 is supercooled by the cooler E2, the supercooled low-pressure liquid air 21 enters the low-pressure tower condenser evaporator K2 as a cold source. The low-pressure nitrogen enters the low-pressure tower condenser evaporator K2 as a heat source, and is condensed into low-pressure liquid nitrogen and is divided into three parts: one part can be used as low-pressure product liquid nitrogen 26, one part of the liquid nitrogen is used as the reflux of the low-pressure tower C2, and the remaining liquid nitrogen is pressurized by the liquid nitrogen pump NP1 to become pressure liquid nitrogen 27, and then merges with the liquid nitrogen condensed by the pressure tower condenser evaporator K1 and enters the top of the pressure tower C1.

[0054] The oxygen-enriched air 23 obtained on the evaporation side of the low-pressure tower condenser evaporator K2 is reheated through the cooler E2 and the main heat exchanger E1 to obtain oxygen-enriched air 25 at room temperature.

[0055] This approach is universal.

[0056] Example 2

[0057] like Figure 2 As shown, this embodiment provides a low energy consumption, high nitrogen device without a separate subcooler.

[0058] Compared with Example 1, the difference is that the subcooler E2 is removed, and the low-pressure liquid air 20 obtained by the low-pressure tower C2 is subcooled by the main heat exchanger E1 to become subcooled low-pressure liquid air 21 and enters the low-pressure tower condenser evaporator K2 as a cold source for evaporation, and the oxygen-rich air 23 of the low-pressure tower condenser evaporator K2 is directly reheated by the main heat exchanger E1 to become room-temperature oxygen-rich air 25.

[0059] Example 3

[0060] like Figure 3 As shown, this embodiment provides a low-energy consumption, high-purity, high-nitrogen device with a subcooler.

[0061] In this embodiment, compared with Embodiment 1, the difference is that the liquid nitrogen 27 pressurized by the liquid nitrogen pump NP1 enters the upper part of the pressure tower C1 (a position lower than the top reflux, and is distilled and washed through a packing layer or a sieve plate tower).

[0062] This method can obtain ultra-high purity nitrogen or avoid the influence of copper alloy on nitrogen in liquid nitrogen pump.

[0063] Example 4

[0064] like Figure 4 As shown, this embodiment provides a low-energy consumption, high-purity, high-nitrogen device that does not have a separate subcooler.

[0065] In this embodiment, compared with Embodiment 2, the difference is that the liquid nitrogen 27 pressurized by the liquid nitrogen pump NP1 enters the upper part of the pressure tower C1 (a position lower than the top reflux, and is washed by a packing layer or a sieve plate tower distillation).

[0066] This method can also obtain ultra-high purity nitrogen or avoid the influence of copper alloy on nitrogen in liquid nitrogen pump.

[0067] Example 5

[0068] like Figure 5 As shown, this embodiment provides a low energy consumption ultra-high purity high nitrogen device equipped with a subcooler.

[0069] In this embodiment, compared with Embodiment 3, the difference is that the pipes 13 and 14 for the pressure tower C1 pressure liquid air to enter and exit the main heat exchanger E1 are removed, and the pipes 13 and 14 for the pressure tower C1 pressure liquid air to enter and exit the subcooler E2 are adjusted.

[0070] In this embodiment, since the pressure liquid air 13 and the low-pressure liquid air 20 do not pass through the main heat exchanger E1 where the product nitrogen is located, there is no need to worry about the influence of temporary parking on the purity of the nitrogen due to incomplete replacement of impure nitrogen, and ultra-high purity nitrogen products are obtained. However, the main heat exchanger E1 does not have the low-temperature cooling capacity of the liquid air to absorb the product nitrogen, resulting in a certain liquefaction rate of the low-temperature purified air 12, thereby reducing the nitrogen extraction rate.

[0071] Example 6

[0072] like Figure 6 As shown, this embodiment provides a low energy consumption ultra-high purity high nitrogen device with an optimized subcooler.

[0073] In this embodiment, if Figure 6 As shown, compared with the fifth embodiment, the difference is that the oxygen-enriched air pipeline 17 from the pressure tower condenser evaporator K1 to the main heat exchanger E1 is removed, and the oxygen-enriched air pipeline 17 from the pressure tower condenser evaporator K1 is adjusted to first pass through the subcooler E2 and then enter the main heat exchanger E1.

[0074] In this embodiment, since the pressure liquid air 13 and the low-pressure liquid air 20 do not pass through the main heat exchanger E1 where the product nitrogen is located, there is no need to worry about the influence of temporary parking on the purity of the nitrogen due to incomplete replacement of impure nitrogen, and ultra-high purity nitrogen products are obtained. Since the low-temperature cooling capacity of the oxygen-enriched air in the pressure tower condenser evaporator is recovered, the low-temperature purified air 12 has a lower liquefaction rate than Example 5, and the nitrogen extraction rate is improved.

[0075] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of by a person skilled in the art within the technical scope disclosed by the present invention without creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. A low-energy consumption large and medium-sized high-nitrogen device, comprising a main heat exchanger (E1), an expander (CE1), a pressure tower (C1), a pressure tower condenser evaporator (K1), a low-pressure tower (C2), a low-pressure tower condenser evaporator (K2), a liquid nitrogen pump (NP1), and a subcooler (E2); It is characterized in that Normal temperature purified air (11) is cooled by the main heat exchanger (E1) to become low temperature purified air (12) and then enters the lower part of the pressure tower (C1) to participate in distillation; At the bottom of the pressure tower (C1), pressurized liquid air is obtained, and at the top, pressurized nitrogen is obtained. The pressurized liquid air (13) is supercooled by the main heat exchanger (E1) and is divided into two parts: one part of the pressurized liquid air (15) enters the pressure tower condenser evaporator (K1) as a cold source, and the other part of the pressurized liquid air (16) enters the low-pressure tower (C2) for rectification. The pressurized nitrogen is divided into two parts: one part of the pressurized nitrogen enters the pressure tower condenser evaporator (K1) as a heat source, and is condensed into liquid nitrogen as the reflux of the pressure tower (C1), and the other part of the pressurized nitrogen (29) is reheated by the main heat exchanger (E1) and extracted as product nitrogen (30); The oxygen-enriched air (17) obtained from the evaporation side of the pressure tower condenser evaporator (K1) is reheated by the main heat exchanger (E1) and then enters the expansion end (E) of the expander (CE1). The expanded oxygen-enriched air (19) enters the lower part of the low-pressure tower (C2) to participate in distillation. Low-pressure liquid air is obtained at the bottom of the low-pressure tower (C2), and low-pressure nitrogen is obtained at the top. After the low-pressure liquid air (20) is supercooled by the cooler (E2), the supercooled low-pressure liquid air (21) enters the low-pressure tower condenser evaporator (K2) as a cold source, and the low-pressure nitrogen enters the low-pressure tower condenser evaporator (K2) as a heat source, and is condensed into low-pressure liquid nitrogen and divided into two parts: one part of the liquid nitrogen is used as the reflux of the low-pressure tower (C2), and the other part of the liquid nitrogen is pressurized by the liquid nitrogen pump (NP1) to become pressure liquid nitrogen (27) and enters the upper part of the pressure tower (C1); The oxygen-enriched air (23) obtained on the evaporation side of the low-pressure tower condenser evaporator (K2) is reheated through the cooler (E2) and the main heat exchanger (E1) to obtain oxygen-enriched air (25) at room temperature.

2. A low energy consumption large and medium-sized high nitrogen device according to claim 1, characterized in that: The main heat exchanger (E1) is provided with a pressure liquid-air subcooling section, and the pressure liquid air (13) at the bottom of the pressure tower (C1) is connected to the liquid-air heat release channel of the main heat exchanger (E1), or the main heat exchanger (E1) is not provided with a pressure liquid-air subcooling section, and the pressure liquid air (13) at the bottom of the pressure tower (C1) is connected to the liquid-air heat release channel of the subcooler (E2).

3. A low energy consumption large and medium-sized high nitrogen device according to claim 2, characterized in that: The cooled pressure liquid air (14) is divided into two parts: one part of the pressure liquid air (15) enters the pressure tower condenser evaporator (K1) as a cold source, and the other part of the pressure liquid air (16) enters the low-pressure tower (C2) for distillation, or all of the cooled pressure liquid air (14) goes to the pressure tower condenser evaporator (K1) as a cold source.

4. A low energy consumption large and medium-sized high nitrogen device according to claim 3, characterized in that: A subcooler (E2) is provided, and the low-pressure liquid air (20) at the bottom of the low-pressure tower (C2) is connected to the low-pressure liquid air heat release channel of the subcooler (E2). After subcooling, the low-pressure liquid air (21) enters the low-pressure tower condenser evaporator (K2) as a cold source. Alternatively, no subcooler (E2) is provided, and the main heat exchanger (E1) is provided with a low-pressure liquid air subcooling section. The low-pressure liquid air (20) at the bottom of the low-pressure tower (C2) is connected to the low-pressure liquid air heat release channel of the main heat exchanger (E1). After subcooling, the low-pressure liquid air (21) enters the low-pressure tower condenser evaporator (K2) as a cold source.

5. A low energy consumption large and medium-sized high nitrogen device according to claim 4, characterized in that: The oxygen-enriched air (17) obtained on the evaporation side of the pressure tower condenser evaporator (K1) is reheated by the main heat exchanger (E1) and then enters the expansion end (E) of the expander (CE1). The expanded oxygen-enriched air (19) enters the lower part of the low-pressure tower (C2) to participate in distillation. Alternatively, the oxygen-enriched air (17) obtained on the evaporation side of the pressure tower condenser evaporator (K1) is reheated by the cooler (E2) and the main heat exchanger (E1) respectively, and then the reheated oxygen-enriched air (18) enters the expansion end (E) of the expander (CE1). The expanded oxygen-enriched air (19) enters the lower part of the low-pressure tower (C2) to participate in distillation.

6. A low energy consumption large and medium-sized high nitrogen device according to claim 5, characterized in that: The method further comprises extracting the pressurized liquid nitrogen produced by liquefaction in the pressure tower condenser evaporator (K1) as a liquid nitrogen product (28), and / or further comprises extracting the low-pressure liquid nitrogen produced by liquefaction in the low-pressure tower condenser evaporator (K2) as a liquid nitrogen product (26).

7. A low energy consumption large and medium-sized high nitrogen device according to claim 6, characterized in that: The method also includes extracting oxygen-rich liquid air from the condenser evaporator (K2) of the low-pressure tower as a cold source for safe discharge (22).

8. A low energy consumption medium to large high nitrogen device according to claim 7, characterized in that: Part of the liquid nitrogen condensed in the low-pressure tower condenser evaporator (K1) is pressurized by a liquid nitrogen pump (NP1) to become pressure liquid nitrogen (27) and enters the upper part of the pressure tower (C1), or part of the liquid nitrogen condensed in the low-pressure tower condenser evaporator (K1) is pressurized by a liquid nitrogen pump (NP1) to become pressure liquid nitrogen (27) and enters the top of the pressure tower (C1).

9. The low energy consumption large and medium-sized high nitrogen device according to claim 8, characterized in that: The oxygen-enriched air (23) obtained on the evaporation side of the low-pressure tower condenser evaporator (K2) is reheated through the cooler (E2) and the main heat exchanger (E1) to obtain oxygen-enriched air 25 at room temperature, or the oxygen-enriched air (23) obtained on the evaporation side of the low-pressure tower condenser evaporator (K2) is directly reheated through the main heat exchanger (E1) to obtain oxygen-enriched air (25) at room temperature.

10. The low energy consumption medium to large high nitrogen device according to claim 9, characterized in that: It also includes an expander (CE1): the expansion end (E) of the expander has an inlet of oxygen-enriched air (18) and an outlet of low-temperature oxygen-enriched air (19), which is connected to the lower part of the low-pressure tower (C2); The output end of the expander is a blower, a generator, an oil brake device, and a boosting end. When it is a boosting end, the nitrogen product (30) exiting the main heat exchanger is pressurized.

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