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

Abstract

The utility model 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 condensing evaporator, a low-pressure tower condensing 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] This utility model relates to a high-nitrogen device, and more particularly to a low-energy-consumption large and medium-sized high-nitrogen device, belonging to the technical field of high-nitrogen devices. Background Technology

[0002] Some chemical, electronics, semiconductor, photovoltaic, and LCD panel industries often require large amounts of nitrogen and have little or no demand for oxygen. Under normal operating conditions, they also have very little demand for liquids. Due to high reliability requirements, they often use dual-tower + pump high-nitrogen units.

[0003] However, existing large and medium-sized high-nitrogen devices suffer from energy loss due to low oxygen pressure at the top, large volumetric flow rate, and poor energy utilization. Therefore, a low-energy-consumption large and medium-sized high-nitrogen device is designed to solve the above problems. Utility Model Content

[0004] The purpose of this invention is to provide a low-energy-consumption, large-to-medium-sized high-nitrogen device that utilizes the pressure difference between the pressure tower condenser / evaporator and the low-pressure tower for expansion, providing cooling capacity to the system. Because the pressure of the pressure tower condenser / evaporator is relatively high, the volumetric flow rate is significantly reduced, the expander impeller diameter is significantly reduced, and the stability and efficiency of the expander are improved. Simultaneously, the operating pressure of the low-pressure tower is reduced, which is more conducive to distillation and increases the extraction rate of the device.

[0005] Secondly, by using pressurized liquid air and low-pressure liquid air to subcool and recover the cooling capacity of oxygen-enriched air or nitrogen, the liquefaction rate of the air entering the tower is reduced, and the cooling capacity is carried to the top of the distillation tower. At the same time, a portion of the subcooled pressurized liquid air enters the low-pressure tower to participate in distillation, reducing the excess cooling capacity of the unit, improving the nitrogen extraction rate, and reducing the unit energy consumption.

[0006] The technical solution adopted in this utility model is as follows:

[0007] A low-energy-consumption large and medium-sized high-nitrogen plant includes a main heat exchanger, an expander, a pressure tower, and

[0008] The apparatus includes a pressure tower condenser / evaporator, a low-pressure tower, a low-pressure tower condenser / evaporator, a liquid nitrogen pump, and a subcooler. The steps involved are as follows:

[0009] S100: The ambient temperature purified air is cooled to low temperature purified air by the main heat exchanger and then enters the lower part of the pressure tower to participate in distillation.

[0010] S200: Pressurized liquid air is obtained at the bottom of the pressure column, and pressurized nitrogen is obtained at the top. The pressurized liquid air is subcooled by the main heat exchanger and then divided into two parts: the first part enters the pressure column condenser / evaporator as a cold source, and the second part enters the low-pressure column for rectification. The pressurized nitrogen is divided into two parts: one part enters the pressure column condenser / evaporator as a heat source, condenses into liquid nitrogen, and serves as reflux for the pressure column; the other part is reheated by the main heat exchanger and extracted as product nitrogen.

[0011] S300: The oxygen-enriched air obtained from the evaporation side of the pressure tower condenser evaporator is reheated by the main heat exchanger and then enters the expansion end of the expander. The expanded oxygen-enriched air then enters the lower part of the low-pressure tower to participate in distillation.

[0012] S400: Low-pressure liquid air is obtained at the bottom of the low-pressure tower, and low-pressure nitrogen is obtained at the top. The low-pressure liquid air at the bottom is subcooled by a cooler and then 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, condenses into low-pressure liquid nitrogen, and is divided into two parts: one part of the liquid nitrogen is used as reflux in the low-pressure tower, and the other part of the liquid nitrogen is pressurized by a liquid nitrogen pump to become pressurized liquid nitrogen and enters the upper part of the pressure tower.

[0013] S500: The low-pressure oxygen-enriched air obtained from the evaporation side of the low-pressure tower condenser-evaporator is reheated by the cooler and the main heat exchanger to obtain room temperature oxygen-enriched air.

[0014] In one embodiment of this 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.

[0015] or

[0016] In step S200, the main heat exchanger does not have 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 subcooler.

[0017] In one embodiment of this application, in step S200, the cooled pressurized liquid air is divided into two parts: the first part of the pressurized liquid air enters the pressure tower condenser-evaporator as a cold source, and the second part of the pressurized liquid air enters the low-pressure tower for distillation.

[0018] or

[0019] In step S200, the cooled pressurized liquid air is sent to the pressure tower condenser-evaporator as a cold source.

[0020] In one embodiment of this 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 low-pressure tower condenser-evaporator as a cold source.

[0021] or

[0022] In step S400, no subcooler is installed. The main heat exchanger is equipped 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 low-pressure tower condenser-evaporator as a cold source.

[0023] In one embodiment of this application, in step S300, the oxygen-enriched air obtained from the evaporation side of the pressure tower condenser evaporator is reheated by the main heat exchanger and then enters the expansion end of the expander. The expanded oxygen-enriched air then enters the lower part of the low-pressure tower to participate in distillation.

[0024] or

[0025] In step S300, the oxygen-enriched air obtained from the evaporation side of the pressure tower condenser evaporator is reheated by the cooler and the main heat exchanger. 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.

[0026] In one embodiment of this application, step S200 further includes extracting pressurized liquid nitrogen generated from liquefaction in the pressure tower condenser-evaporator as a pressurized liquid nitrogen product.

[0027] and / or

[0028] Step S400 also includes extracting the low-pressure liquid nitrogen generated by liquefaction in the low-pressure tower condenser-evaporator as a low-pressure liquid nitrogen product.

[0029] In one embodiment of this application, step S400 further includes extracting oxygen-rich liquid air, which serves as a cold source, from the low-pressure tower condenser-evaporator for safe discharge.

[0030] In one embodiment of this application, in step S400, a portion of the liquid nitrogen condensed by the low-pressure tower condenser evaporator is pressurized by a liquid nitrogen pump to enter the upper part of the pressure tower as pressurized liquid nitrogen.

[0031] or

[0032] In step S400, a portion of the liquid nitrogen condensed in the low-pressure tower condenser evaporator is pressurized by a liquid nitrogen pump to enter the top of the pressure tower as pressurized liquid nitrogen.

[0033] In one embodiment of this application, in step S500: the oxygen-enriched air obtained from the evaporation side of the low-pressure tower condenser evaporator is reheated by the cooler and the main heat exchanger to obtain room temperature oxygen-enriched air.

[0034] or

[0035] In step S500: the oxygen-enriched air obtained from the evaporation side of the low-pressure tower condenser is directly reheated by the main heat exchanger to obtain room temperature oxygen-enriched air.

[0036] In one embodiment of this application, an expander is further included: the expander's inlet is oxygen-enriched air, its outlet is expanded oxygen-enriched air, and it is connected to the lower part of the low-pressure tower; the expander's output end is a blower, a generator, an oil brake device, and also a pressurization end. When it is the pressurization end, the product nitrogen gas exiting the main heat exchanger is pressurized.

[0037] The beneficial effects of this utility model are:

[0038] This invention provides a low-energy-consumption, large-to-medium-sized high-nitrogen device. It employs a simple method to solve the problems of low pressure and high volumetric flow rate in oxygen-enriched high-nitrogen devices, which are difficult to utilize. It significantly reduces the size of the expander impeller and pipelines. The increased inlet and outlet pressures of the expander improve the stability of the device. Furthermore, it cleverly utilizes the subcooling of liquid air and oxygen-enriched liquid air to absorb the cold energy of various media, further reducing the liquefaction rate of the air entering the pressure tower. The cold energy is carried to the top, which is more conducive to distillation. A portion of the liquid air enters the low-pressure tower to participate in distillation, increasing nitrogen production and improving nitrogen extraction rate. Utilizing the liquid nitrogen from the low-pressure tower to enter the pressure tower for further distillation (also serving as a washing function) avoids contamination or contaminant retention during the pump pressurization process and in the pipelines.

[0039] It can also reduce the impact of low-pressure tower operation instability on purity, thereby meeting the requirements for ultra-high purity nitrogen and avoiding the influence of the pump body's copper-zinc alloy on the product. It is very suitable for parallel arrangement of two towers and facilitates modularization of the cold box. Attached Figure Description

[0040] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. This utility model will be described by way of example and with reference to the accompanying drawings.

[0041] Figure 1 shows a typical low-energy-consumption, high-nitrogen device with a separate subcooler in this embodiment 1.

[0042] Figure 2 shows a low-energy-consumption high-nitrogen device in this embodiment 2 that does not require a separate subcooler.

[0043] Figure 3 shows a low-energy-consumption, high-purity, high-nitrogen device with a supercooler in this embodiment 3.

[0044] Figure 4 shows a low-energy-consumption, high-purity, high-nitrogen device that does not require a separate subcooler, according to Embodiment 4 of this invention.

[0045] Figure 5 shows a low-energy-consumption ultra-high purity high nitrogen device with a supercooler in this embodiment 5.

[0046] Figure 6 shows a low-energy-consumption ultra-high-purity high-nitrogen device with an optimized supercooler according to Embodiment 6 of this invention.

[0047] Figure label:

[0048] 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 - Ambient temperature purified air, 12 - Low temperature purified air, 13 - Pressure liquid air, 14 - Subcooled pressure liquid air, 15 - Liquid air to pressure tower condenser / evaporator, 16 - Liquid air to lower part of low-pressure tower, 17 - Oxygen-enriched air to pressure tower condenser / evaporator, 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 -

[0049] 24 - Oxygen-enriched air from the low-pressure tower condenser evaporator; 25 - Oxygen-enriched air from the subcooler; 26 - Ambient temperature oxygen-enriched air; 27 - Liquid nitrogen from the low-pressure tower product; 28 - Liquid nitrogen at pressure after the liquid nitrogen pump; 29 - Liquid nitrogen from the pressure tower product; 30 - Low-temperature pressure nitrogen; 31 - Ambient temperature nitrogen product. Detailed Implementation

[0050] All features disclosed in this specification, or steps in all methods or processes disclosed, may be combined in any way except for mutually exclusive features and / or steps.

[0051] The following refers to Figure 1 to... Figure 6 The embodiments of this utility model will be described in detail below.

[0052] Example 1

[0053] As shown in Figure 1, this embodiment provides a typical low-energy-consumption high-nitrogen device with a separate subcooler. It includes 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).

[0054] Ambient temperature purified air 11 enters the main heat exchanger E1 and is cooled to near-dew point low-temperature purified air 12. This low-temperature purified air 12 then enters the pressure tower C1 for distillation, obtaining pressurized liquid air at the bottom and pressurized nitrogen at the top. The pressurized liquid air 13, after being subcooled by the main heat exchanger E1, is divided into two parts: the first stream of pressurized liquid air 15 enters the pressure tower condenser-evaporator K1 as a cold source, and the second stream of pressurized liquid air 16 enters the low-pressure tower C2 for distillation. The pressurized nitrogen obtained at the top of the tower is divided into two parts: one part enters the pressure tower condenser-evaporator K1, where it is condensed into liquid nitrogen; a portion of this liquid nitrogen is used as the pressurized product liquid nitrogen 28, and the remainder is returned to the pressure tower C1 as reflux. The remaining pressurized nitrogen 29 is reheated in the main heat exchanger E1 to obtain ambient temperature product nitrogen 30.

[0055] The oxygen-enriched air 17 obtained by evaporation in the pressure tower condenser K1 is reheated by the main heat exchanger E1 to obtain oxygen-enriched air 18 before expansion, and then expanded by the expansion end E of the expander CE1 to obtain expanded oxygen-enriched air 19, which enters the lower part of the low-pressure tower C2 to participate in distillation.

[0056] Low-pressure liquid air is obtained at the bottom of low-pressure tower C2, and low-pressure nitrogen is obtained at the top. After being subcooled by cooler E2, the subcooled 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, condensing...

[0057] After being converted to low-pressure liquid nitrogen, it is divided into three parts: one part can be used as low-pressure product liquid nitrogen 26, another part is used as reflux in low-pressure tower C2, and the remaining liquid nitrogen is pressurized to pressure liquid nitrogen 27 by liquid nitrogen pump NP1 and then merges with the liquid nitrogen condensed by pressure tower condenser evaporator K1 and enters the top of pressure tower C1.

[0058] The low-pressure oxygen-enriched air 23 obtained from the evaporation side of the low-pressure tower condenser-evaporator K2 is reheated by the cooler E2 and the main heat exchanger E1 to obtain room temperature oxygen-enriched air 25.

[0059] This approach is universal.

[0060] Example 2

[0061] As shown in Figure 2, this embodiment provides a low-energy-consumption high-nitrogen device that does not require a separate subcooler.

[0062] Compared to Example 1, the difference is that the subcooler E2 is removed, and the low-pressure liquid air 20 obtained from the low-pressure tower C2 is subcooled into subcooled low-pressure liquid air 21 by the main heat exchanger E1 and enters the low-pressure tower condenser-evaporator K2 as a cold source for evaporation. The low-pressure oxygen-enriched air 23 from the low-pressure tower condenser-evaporator K2 is directly reheated into room temperature oxygen-enriched air 25 by the main heat exchanger E1.

[0063] Example 3

[0064] As shown in Figure 3, this embodiment provides a low-energy-consumption, high-purity, high-nitrogen device with a subcooler.

[0065] In this embodiment, the difference from embodiment 1 is that the liquid nitrogen 27, after being pressurized by the liquid nitrogen pump NP1, enters the upper part of the pressure tower C1 (a position slightly lower than the top reflux, and is washed by distillation through a packing layer or sieve plate tower).

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

[0067] Example 4

[0068] like Figure 4 As shown, this embodiment provides a low-energy-consumption, high-purity, high-nitrogen device that does not require a separate subcooler.

[0069] In this embodiment, the difference from embodiment 2 is that the liquid nitrogen 27, after being pressurized by the liquid nitrogen pump NP1, enters the upper part of the pressure tower C1 (a position slightly lower than the top reflux, and is washed by distillation through a packing layer or sieve plate tower).

[0070] This method also yields ultra-high purity nitrogen or avoids the impact of using copper alloys in liquid nitrogen pumps on the nitrogen.

[0071] Example 5

[0072] As shown in Figure 5, this embodiment provides a low-energy-consumption ultra-high-purity high-nitrogen device with a supercooler.

[0073] In this embodiment, the difference from embodiment 3 is that the pipes 13 and 14 of the pressure tower C1 pressure liquid air entering and exiting the main heat exchanger E1 are removed, and the pipes 13 and 14 of the pressure tower C1 pressure liquid air entering and exiting the subcooler E2 are adjusted.

[0074] In this embodiment, since the pressurized liquid air 13 and the bottom 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 impact of incomplete replacement of impure nitrogen during temporary shutdowns on nitrogen purity, thus obtaining ultra-high purity product nitrogen. However, the lack of low-temperature cooling capacity of the product nitrogen absorbed by the main heat exchanger E1 results in a certain liquefaction rate of the low-temperature purified air 12, which leads to a decrease in nitrogen extraction rate.

[0075] Example 6

[0076] As shown in Figure 6, this embodiment provides a low-energy-consumption ultra-high-purity high-nitrogen device with an optimized supercooler.

[0077] In this embodiment, as shown in Figure 6, the difference from embodiment five is that the oxygen-enriched air pipe 17 from the pressure tower condenser-evaporator K1 to the main heat exchanger E1 is removed, and the oxygen-enriched air pipe 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.

[0078] In this embodiment, since the pressurized liquid air 13 and 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 incomplete nitrogen replacement due to temporary shutdowns affecting nitrogen purity.

[0079] The effect was that ultra-high purity product nitrogen was obtained. Because the low-temperature cold energy of the oxygen-enriched air in the pressure tower condenser-evaporator was recovered, the liquefaction rate of the low-temperature purified air 12 was reduced compared to Example 5, resulting in a higher nitrogen extraction rate.

[0080] The above are merely preferred embodiments of this utility model, but the scope of protection of this utility model is not limited thereto. Any variations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in this utility model without creative effort should be included within the scope of protection of this utility model. Therefore, the scope of protection of this utility model should be determined by the 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). Its features are, The main heat exchanger (E1) is connected to the pressure tower (C1) to cool the ambient temperature purified air (11) into low temperature purified air (12) after passing through the main heat exchanger (E1) and then enter the lower part of the pressure tower (C1) to participate in distillation; the bottom of the pressure tower (C1) obtains bottom pressurized liquid air (13) and the top obtains pressurized nitrogen. The main heat exchanger (E1) is connected to the pressure tower condenser-evaporator (K1) so that the pressure liquid air (13) at the bottom is divided into two parts after being subcooled by the main heat exchanger (E1): the first line of pressure liquid air (15) enters the pressure tower condenser-evaporator (K1) as a cold source, and the second line of pressure liquid air (16) enters the low-pressure tower (C2) for distillation. The pressure nitrogen is divided into two parts: one part of the pressure nitrogen enters the pressure tower condenser-evaporator (K1) as a heat source, and after condensing into liquid nitrogen, it is used as the reflux of the pressure tower (C1); the other part of the pressure nitrogen (29) is reheated by the main heat exchanger (E1) and extracted as product nitrogen (30). The main heat exchanger (E1) is connected to the expander (CE1) to allow the oxygen-enriched air (17) obtained from the evaporation side of the pressure tower condenser evaporator (K1) to be reheated by the main heat exchanger (E1) and then the reheated oxygen-enriched air (18) enters the expansion end (E) of the expander (CE1). The expanded oxygen-enriched air (19) then enters the lower part of the low-pressure tower (C2) to participate in distillation. The low-pressure tower (C2) is connected to the subcooler (E2) to obtain low-pressure liquid air (20) at the bottom of the low-pressure tower (C2) and low-pressure nitrogen at the top. After the low-pressure liquid air (20) at the bottom is subcooled by the subcooler (E2), the subcooled 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. After condensing into low-pressure liquid nitrogen, it is divided into two parts: one part of liquid nitrogen is used as reflux of the low-pressure tower (C2), and the other part of liquid nitrogen is pressurized into pressurized liquid nitrogen (27) by the liquid nitrogen pump (NP1) and enters the upper part of the pressure tower (C1). The subcooler (E2) and the main heat exchanger (E1) are both connected to the low-pressure tower condenser-evaporator (K2) to reheat the low-pressure oxygen-enriched air (23) obtained from the evaporation side of the low-pressure tower condenser-evaporator (K2) through the subcooler (E2) and the main heat exchanger (E1) to obtain room temperature oxygen-enriched air (25).

2. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 1, characterized in that, The main heat exchanger (E1) is equipped with a pressure liquid air subcooling section. 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). Alternatively, the main heat exchanger (E1) is not equipped with a pressure liquid air subcooling section. 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. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 2, characterized in that, After cooling, the pressurized liquid air (14) is divided into two parts: the first stream of pressurized liquid air (15) enters the pressure tower condenser-evaporator (K1) as a cold source, and the second stream of pressurized liquid air (16) enters the low-pressure tower (C2) for distillation, or all the pressurized liquid air (14) after cooling goes to the pressure tower condenser-evaporator (K1) as a cold source.

4. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 3, characterized in that, A subcooler (E2) is provided. 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, a subcooler (E2) is not provided. 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. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 4, characterized in that, 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. Alternatively, the oxygen-enriched air (17) obtained from the evaporation side of the pressure tower condenser-evaporator (K1) is reheated by the cooler (E2) and the main heat exchanger (E1) respectively. The reheated oxygen-enriched air (18) enters the expansion end (E) of the expander (CE1) and then enters the lower part of the low-pressure tower (C2) to participate in distillation.

6. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 5, characterized in that, It also includes extracting pressurized liquid nitrogen generated from liquefaction in the pressure tower condenser-evaporator (K1) as pressurized liquid nitrogen product (28), and / or extracting low-pressure liquid nitrogen generated from liquefaction in the low-pressure tower condenser-evaporator (K2) as low-pressure liquid nitrogen product (26).

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

8. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 7, characterized in that, Part of the liquid nitrogen condensed by the low-pressure tower condenser evaporator (K2) is pressurized into pressurized liquid nitrogen (27) by the liquid nitrogen pump (NP1) and enters the upper part of the pressure tower (C1), or part of the liquid nitrogen condensed by the low-pressure tower condenser evaporator (K2) is pressurized into pressurized liquid nitrogen (27) by the liquid nitrogen pump (NP1) 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 low-pressure oxygen-enriched air (23) obtained from the evaporation side of the low-pressure tower condenser evaporator (K2) is reheated by the cooler (E2) and the main heat exchanger (E1) to obtain room temperature oxygen-enriched air (25), or the low-pressure oxygen-enriched air (23) obtained from the evaporation side of the low-pressure tower condenser evaporator (K2) is directly reheated by the main heat exchanger (E1) to obtain room temperature oxygen-enriched air (25).

10. The low-energy-consumption large and medium-sized high-nitrogen device according to claim 9, characterized in that, It also includes an expander (CE1): the expander's expansion end (E) has an inlet of oxygen-enriched air (18) and an outlet of expanded 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 booster end. When it is the booster end, it boosts the nitrogen gas (30) that is the product gas exiting the main heat exchanger.

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