Nitrogen-making device for low-temperature rectification
By adding a second distillation column and a top condenser to the cryogenic distillation unit, and using oxygen-enriched air pressure to drive a turbine expander for energy recovery, the problem of high energy consumption in the single-tower nitrogen production process is solved, achieving efficient nitrogen production and low-cost operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2026-03-27
AI Technical Summary
The existing single-tower nitrogen production process consumes a lot of energy when producing nitrogen, and the emitted waste nitrogen carries high pressure and needs to be depressurized, which increases operating costs and makes it difficult to meet the needs of steel production enterprises.
A cryogenic distillation unit is adopted, with the addition of a second distillation column and a second top condenser. The pressure of the oxygen-enriched air discharged from the second top condenser drives the turbine expander, and energy is recovered through a subcooler and a main heat exchanger. The process is optimized by combining a liquid level sensor to improve the nitrogen extraction rate and reduce energy consumption.
It improves nitrogen extraction rate, reduces energy consumption, simplifies installation process, and lowers operating costs, making it suitable for the needs of steel production enterprises.
Smart Images
Figure CN224050802U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the field of nitrogen making equipment of low temperature rectification, specifically relates to a nitrogen making device of low temperature rectification. BACKGROUND
[0002] Steel production enterprises have a large demand for oxygen-enriched air and nitrogen. Among them, the pulverized coal is sprayed into the blast furnace by using oxygen-enriched air as carrier gas, participates in the reduction reaction with iron ore and air, provides fuel and heat for the blast furnace, and at the same time affects the balance of carbon, oxygen and other elements. Oxygen-enriched air regulates the oxygen supply in the blast furnace, which has a significant impact on the rate of reduction reaction and the temperature distribution in the furnace. At the same time, steel production enterprises also have a demand for nitrogen, mainly for the driving gas source required by the actuator of pneumatic valve, instrument gas source, pipeline replacement gas source, pipeline purging gas source, gas source required by top and bottom combined blowing of converter, and gas source required by hot metal desulfurization.
[0003] Therefore, the single-column nitrogen making equipment designed by using the low-temperature rectification method becomes one of the alternative solutions for gas source equipment of steel production enterprises because it can provide oxygen-enriched air and pure nitrogen as products. In addition, since the single-column nitrogen making equipment has a lower tower height and is easier to install than the traditional upper and lower tower rectification oxygen-nitrogen separation equipment, the single-column nitrogen making process is an optimal solution for steel production enterprises, which has low installation difficulty and can reasonably utilize oxygen-enriched air and nitrogen. However, due to the process of single-column nitrogen making, the waste nitrogen gas as oxygen-enriched air gas source still carries a high pressure during discharge, which needs to be decompressed before use in the subsequent process. According to the law of conservation of energy, the gaseous discharge carrying high energy means that more energy cost is consumed to produce a unit volume of nitrogen.
[0004] Although the single-column nitrogen making process is more convenient to install and has relatively small investment, the high operating cost will also bring a large operating cost to steel production enterprises. Therefore, there is room for improvement in the prior art to reduce the energy cost consumed in the production of nitrogen and at the same time to provide oxygen-enriched air to the target user as participating in the operation of the blast furnace, and the rectification equipment for oxygen-nitrogen separation with a lower height than the upper and lower tower rectification equipment is easy to install to meet the market demand and promote the product. SUMMARY
[0005] In view of the deficiencies of the prior art, the utility model provides a low-temperature rectification nitrogen making device capable of providing nitrogen and oxygen-enriched air to the target user while fully utilizing the energy carried by the product gas to reduce energy consumption, for overcoming the defects in the prior art.
[0006] The utility model discloses a technical scheme for a low-temperature rectification nitrogen production device, which comprises a main heat exchanger and a first rectification tower.
[0007] Preferably, the first rectification tower, the second rectification tower, the first overhead condenser and the second overhead condenser are each provided with a liquid level sensor, and the first liquid air conveying pipe and the second liquid air conveying pipe are each provided with a first regulating valve.
[0008] Preferably, the first overhead condenser, the second overhead condenser and the main heat exchanger are provided with a finished nitrogen conveying pipe, the finished nitrogen conveying pipe between the main heat exchanger and the outlet end of the finished nitrogen conveying pipe is provided with a second regulating valve, the first rectification tower and the finished nitrogen conveying pipe, and the second rectification tower and the finished nitrogen conveying pipe are provided with a first nitrogen conveying branch pipe, each first nitrogen conveying branch pipe is provided with a first check valve, the second overhead condenser and the finished nitrogen conveying pipe, and the finished nitrogen conveying pipe and the first overhead condenser are each provided with a second nitrogen conveying branch pipe, and each second nitrogen conveying branch pipe is provided with a third regulating valve.
[0009] Preferably, the outlet end of the first overhead condenser and the outlet end of the second overhead condenser are provided with a liquid nitrogen conveying main pipe, the liquid nitrogen conveying main pipe and the outlet end of the first overhead condenser, and the liquid nitrogen conveying main pipe and the outlet end of the second overhead condenser are each connected through a liquid nitrogen conveying branch pipe, each liquid nitrogen conveying branch pipe is provided with a second check valve, the liquid nitrogen conveying main pipe is provided with a fourth regulating valve, the liquid nitrogen conveying main pipe and the first rectification tower, and the liquid nitrogen conveying main pipe and the second rectification tower are each connected through a liquid nitrogen reflux pipe, and each liquid nitrogen reflux pipe is provided with a fifth regulating valve.
[0010] Preferably, the first rectifying tower is provided with a first packing layer, a raw material air conveying main pipe is arranged above the first rectifying tower and the main heat exchanger, the second rectifying tower is sequentially provided with a second packing layer and a third packing layer from bottom to top, and the second rectifying tower below the second packing layer is connected with the top of the first overhead condenser cold source channel through a third waste nitrogen conveying pipe.
[0011] Preferably, the raw material air conveying main pipe is provided with an inlet end of a raw material air conveying branch pipe between the inlet end and the main heat exchanger, the raw material air conveying main pipe is provided with a sixth regulating valve between the raw material air conveying branch pipe and the main heat exchanger, the second rectifying tower between the second packing layer and the third packing layer is connected with the outlet end of the raw material air conveying branch pipe, the raw material air conveying branch pipe is sequentially provided with an expansion end of a second turbine expander, an after-turbine heat exchanger, a pressurization end of the second turbine expander, a pressurization unit and a seventh regulating valve along the direction from the second rectifying tower to the second rectifying tower, and the raw material air conveying branch pipe between the expansion end of the second turbine expander and the after-turbine heat exchanger is arranged on the main heat exchanger.
[0012] The utility model has the advantages that: first, the utility model further rectifies the gas discharged from the first overhead condenser by adding the second rectifying tower and the second overhead condenser, thereby improving the extraction rate of nitrogen; the pressure of the second oxygen-rich air discharged from the second overhead condenser is used as power to drive the first turbine expander to expand and cool again, and the second oxygen-rich air is sent to the subcooler and the main heat exchanger as the cold source of the subcooler and the cold source of the main heat exchanger, thereby fully utilizing the cold energy and pressure of the second oxygen-rich air discharged from the second overhead condenser to refrigerate, and reducing energy consumption.
[0013] Secondly, the bottom of the first rectifying tower, the bottom of the second rectifying tower, the cold source channel of the first overhead condenser and the cold source channel of the second overhead condenser are respectively provided with liquid level sensors, and the liquid level sensors are installed to facilitate feedback of pressure parameters.
[0014] The utility model has the advantages of simple structure, convenient operation, ingenious design, greatly improved work efficiency, good social and economic benefits, and easy popularization and use. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 The utility model discloses a structure schematic view. DETAILED DESCRIPTION
[0016] As Figure 1The low-temperature rectification nitrogen production device shown in the figure comprises a main heat exchanger 1 and a first rectification tower 2, characterized in that: the first rectification tower 2 is provided with a first overhead condenser 3, the inlet end of the heat source channel of the first overhead condenser 3 is connected with the top of the first rectification tower 2, the cold source channel of the first overhead condenser 3 is connected with the bottom of the first rectification tower 2 through a first liquid air conveying pipe 4, the cold source channel of the first overhead condenser 3 is connected with a second rectification tower 5, the second rectification tower 5 is provided with a second overhead condenser 6, the cold source channel of the second overhead condenser 6 is connected with the bottom of the second rectification tower 5 through a second liquid air conveying pipe 7, the cold source channel of the second overhead condenser 6 is provided with a first dirty nitrogen conveying pipe 8 on the main heat exchanger 1, the outlet end of the first dirty nitrogen conveying pipe 8 is provided with a first turbine expander 9, the first dirty nitrogen conveying pipe 8, the second liquid air conveying pipe 7 and the first liquid air conveying pipe 4 are provided with a subcooler 10, the first turbine expander 9, the subcooler 10 and the main heat exchanger 1 are provided with a second dirty nitrogen conveying pipe 11. The bottom of the first rectification tower 2, the bottom of the second rectification tower 5, the cold source channel of the first overhead condenser 3 and the cold source channel of the second overhead condenser 6 are respectively provided with a liquid level sensor 12, and the first liquid air conveying pipe 4 and the second liquid air conveying pipe 7 are respectively provided with a first regulating valve 13.
[0017] The cold source channel of the first overhead condenser 3, the cold source channel of the second overhead condenser 6 and the main heat exchanger 1 are provided with a finished nitrogen conveying pipe 14, the finished nitrogen conveying pipe 14 between the main heat exchanger 1 and the outlet end of the finished nitrogen conveying pipe 14 is provided with a second regulating valve 15, the top of the first rectification tower 2 and the finished nitrogen conveying pipe 14 and the top of the second rectification tower 5 and the finished nitrogen conveying pipe 14 are provided with a first nitrogen conveying branch pipe 16, each first nitrogen conveying branch pipe 16 is respectively provided with a first check valve 17, the cold source channel of the second overhead condenser 6 and the finished nitrogen conveying pipe 14 and the finished nitrogen conveying pipe 14 and the cold source channel of the first overhead condenser 3 are respectively provided with a second nitrogen conveying branch pipe 18, and each second nitrogen conveying branch pipe 18 is respectively provided with a third regulating valve 19.
[0018] A liquid nitrogen delivery main pipe 20 is provided at the outlet end of the heat source channel of the first top condenser 3 and the outlet end of the heat source channel of the second top condenser 6. The liquid nitrogen delivery main pipe 20 and the outlet end of the heat source channel of the first top condenser 3, as well as the outlet ends of the liquid nitrogen delivery main pipe 20 and the heat source channel of the second top condenser 6, are respectively connected by liquid nitrogen delivery branch pipes 21. Each liquid nitrogen delivery branch pipe 21 is provided with a second one-way valve 22. A fourth regulating valve 23 is provided on the liquid nitrogen delivery main pipe 20. The liquid nitrogen delivery main pipe 20 and the top of the first distillation column 2, as well as the top of the liquid nitrogen delivery main pipe 20 and the second distillation column 5, are respectively connected by liquid nitrogen reflux pipes 24. Each liquid nitrogen reflux pipe 24 is provided with a fifth regulating valve 25.
[0019] The first distillation column 2 is provided with a first packing layer 27. The first distillation column 2 and the main heat exchanger 1 below the first packing layer 27 are provided with a raw material air conveying main pipe 26. The second distillation column 5 is provided with a second packing layer 28 and a third packing layer 29 from bottom to top. The top of the cold source channel of the second distillation column 5 below the second packing layer 28 and the first column top condenser 3 are connected by a third waste nitrogen conveying pipe 30. The inlet end of the raw material air conveying main pipe 26 between the inlet end of the raw material air conveying main pipe 26 and the main heat exchanger 1 is provided on the raw material air conveying main pipe 26. The raw material air conveying branch pipe 31 between the raw material air conveying branch pipe 31 and the main heat exchanger 1 is provided on the raw material air conveying main pipe 26. The outlet end of the second distillation column 5 between the second packing layer 28 and the third packing layer 29 is connected to the raw material air conveying branch pipe 31. The raw material air conveying branch pipe 31 is provided with the expansion end of the second turbine expander 33, the downstream heat exchanger 34, the booster end of the second turbine expander 33, the booster unit 35 and the seventh regulating valve 36 in sequence along the direction from near the second distillation column 5 to far away from the second distillation column 5. The raw material air conveying branch pipe 31 between the expansion end of the second turbine expander 33 and the downstream heat exchanger 34 is installed on the main heat exchanger 1.
[0020] The usage instructions for this product are as follows: Figure 1 As shown, it includes the following steps:
[0021] S1, the upstream pre-cooled and purified compressed air is delivered to the raw material air delivery main pipe 26 and is divided into two parts, i.e. the first part of compressed air and the second part of compressed air. The first part of compressed air exchanges heat with the heat source channel of the main heat exchanger 1 and the cold source medium continuously delivered to the main heat exchanger 1, and is then delivered to the first rectification tower 2 to participate in the rectification of the first rectification tower 2. The second part of compressed air is delivered to the raw material air delivery branch pipe 31, and then is first pressurized by the booster set 35, and then is second pressurized by the pressurizing end of the second turbo expander 33. After that, the second part of compressed air exchanges heat with the heat source channel of the post-heat exchanger 34 and the circulating water continuously delivered to the cold source channel of the post-heat exchanger 34, and then is delivered to the second heat source channel of the main heat exchanger 1 and exchanges heat with the cold source medium continuously delivered to the main heat exchanger 1. After that, the second part of compressed air is expanded and cooled by the expansion end of the second turbo expander 33, and then is delivered to the second rectification tower 5 between the second packing layer 28 and the third packing layer 29 to participate in the rectification of the second rectification tower 5.
[0022] S2, the compressed air entering the first rectification tower 2 flows upwards towards the top of the first rectification tower 2 to form a first upward gas flow. The first upward gas flow exchanges heat with the first reflux condensate delivered from the top of the first rectification tower 2 in a countercurrent manner. The oxygen component in the first upward gas flow is liquefied and flows downwards together with the first reflux condensate to the bottom of the first rectification tower 2. The nitrogen component in the first reflux condensate is largely vaporized and combined into the first upward gas flow. Finally, a first nitrogen-rich zone is formed at the top of the first rectification tower 2, and a first oxygen-rich liquid air-rich zone is formed at the bottom of the first rectification tower 2.
[0023] The nitrogen in the first nitrogen-rich zone is divided into two parts, i.e. the first part of nitrogen and the second part of nitrogen. The first part of nitrogen is delivered to the product nitrogen delivery pipe 14, exchanges heat with the first cold source channel of the main heat exchanger 1 and the heat source continuously delivered to the main heat exchanger 1, and is then delivered to the nitrogen user. The second part of nitrogen exchanges heat with the heat source channel of the first overhead condenser 3 and the medium of the cold source channel of the first overhead condenser 3, and is then liquefied to form the first liquid nitrogen product. The first liquid nitrogen product is delivered to the liquid nitrogen delivery main pipe 20, and is then divided into two parts, i.e. the first part of liquid nitrogen and the second part of liquid nitrogen. The first part of liquid nitrogen is delivered to the liquid nitrogen storage tank as a liquid nitrogen product through the outlet end of the liquid nitrogen delivery main pipe 20. The second part of liquid nitrogen is sent back to the top of the first rectification tower 2 through the corresponding liquid nitrogen reflux pipe 24 as the first reflux condensate of the first rectification tower 2.
[0024] The first oxygen-enriched liquid air enrichment zone continuously sends the first oxygen-enriched liquid air to the cold source channel of the first overhead condenser 3 through the first liquid air delivery pipe 4, and exchanges heat with the first heat source channel of the subcooler 10 and the cold source continuously sent to the subcooler 10. The first oxygen-enriched liquid air entering the cold source channel of the first overhead condenser 3 exchanges heat with the medium in the heat source channel of the first overhead condenser 3, is vaporized to form the first oxygen-enriched air, and is sent to the second rectifying column 5 between the second packing layer 28 and the third packing layer 29 through the third waste nitrogen gas delivery pipe 30 to participate in the rectification of the second rectifying column 5.
[0025] S3, the first oxygen-enriched air entering the second packing layer 28 countercurrently exchanges heat with the second reflux condensate delivered from the third packing layer 29, the nitrogen component in the second reflux condensate is vaporized and merged into the second upward gas flow, and the oxygen component in the second upward gas flow is liquefied and continuously downwardly delivered with the second reflux condensate towards the bottom of the second rectifying column 5.
[0026] The second upward gas flow rises into the second rectifying column 5 between the second packing layer 28 and the third packing layer 29, and combines with the second part of the compressed air delivered to the second rectifying column 5 through the raw material air delivery branch pipe 31 to form a third upward gas flow and continuously rises towards the top of the second rectifying column 5, exchanges heat with the second reflux condensate delivered from the top of the second rectifying column 5 to the third packing layer 29 when in the third packing layer 29, the nitrogen component in the second reflux condensate is vaporized and merged into the third upward gas flow, the oxygen component in the third upward gas flow is liquefied and continuously upwardly delivered with the third upward gas flow towards the top of the second rectifying column 5, and the nitrogen component in the second reflux condensate in the third packing layer 29 is vaporized and merged into the third upward gas flow, and the third upward gas flow is continuously upwardly delivered with the third upward gas flow towards the top of the second rectifying column 5, and finally forms a second nitrogen enrichment zone at the top of the second rectifying column 5 and a second oxygen-enriched liquid air enrichment zone at the bottom of the second rectifying column 5.
[0027] The nitrogen in the second nitrogen enrichment zone is divided into two parts, i.e. the third part of nitrogen and the fourth part of nitrogen, the third part of nitrogen is delivered to the product nitrogen delivery pipe 14, and the first part of nitrogen is delivered to the heat source channel of the main heat exchanger 1 and the heat source of the main heat exchanger 1 after heat exchange, and then delivered to the nitrogen user. The fourth part of nitrogen is delivered to the heat source channel of the second overhead condenser 6 and the medium of the cold source channel of the second overhead condenser 6 after heat exchange, and is liquefied to form the second product liquid nitrogen. The second product liquid nitrogen and the first part of liquid nitrogen are combined to form the third product liquid nitrogen, which is divided into two parts, i.e. the third part of liquid nitrogen and the fourth part of liquid nitrogen. The third part of liquid nitrogen is delivered to the liquid nitrogen storage tank as a liquid nitrogen product through the outlet end of the liquid nitrogen delivery main pipe 20. The fourth part of liquid nitrogen is sent back to the top of the second rectifying tower 5 as the second reflux condensate of the second rectifying tower 5 through the corresponding liquid nitrogen return pipe 24.
[0028] The second oxygen-rich liquid air enrichment zone delivers the second oxygen-rich liquid air to the cold source channel of the second overhead condenser 6 through the second liquid air delivery pipe 7, during which heat exchange is performed through the second heat source channel of the subcooler 10 and the cold source continuously delivered to the subcooler 10. After heat exchange between the second oxygen-rich liquid air entering the cold source channel of the second overhead condenser 6 and the medium of the heat source channel of the first overhead condenser 3, the second oxygen-rich liquid air is vaporized to form the second oxygen-rich air and delivered to the first dirty nitrogen delivery pipe 8.
[0029] S4, the first dirty nitrogen delivery pipe 8 enters the second oxygen-rich air first, and then exchanges heat through the first cold source channel of the subcooler 10 and the heat source continuously delivered to the subcooler 10, and then is delivered to the second cold source channel of the main heat exchanger 1 and the heat source of the main heat exchanger 1 after heat exchange. After being discharged from the medium temperature zone of the main heat exchanger 1, the expanded and cooled nitrogen is delivered to the second dirty nitrogen delivery pipe 11, and then is delivered to the second cold source channel of the subcooler 10 and the heat source of the subcooler 10 after heat exchange, and then is delivered to the third cold source channel of the main heat exchanger 1 and the heat source of the main heat exchanger 1 after heat exchange, and finally is delivered to the user of the oxygen-rich air.
[0030] Through this embodiment, the product further rectifies the gas discharged from the first overhead condenser 3 by adding the second rectifying tower 5 and the second overhead condenser 6, thereby improving the extraction rate of nitrogen. The pressure of the second oxygen-rich air discharged from the second overhead condenser 6 is used as power to perform expansion and cooling again by the first turbine expander 9, and is sent to the subcooler 10 and the main heat exchanger 1 as the cold source of the subcooler 10 and the cold source of the main heat exchanger 1. The cold energy and pressure carried by the second oxygen-rich air discharged from the second overhead condenser 6 are fully utilized for refrigeration, thereby reducing energy consumption.
[0031] The above-described embodiments are only preferred embodiments of the present application, and are not intended to limit the scope of the present application, so that equivalent changes or modifications made in the structure, features and principles described in the patent range of the present application should be included in the patent range of the present application.
Claims
1. A nitrogen production apparatus for cryogenic distillation, comprising a main heat exchanger (1) and a first distillation column (2), characterized in that: The first distillation column (2) is equipped with a first top condenser (3) at its top. The inlet end of the heat source channel of the first top condenser (3) is connected to the top of the first distillation column (2). The cold source channel of the first top condenser (3) is connected to the bottom of the first distillation column (2) through a first liquid air delivery pipe (4). A second distillation column (5) is connected to the cold source channel of the first top condenser (3). A second top condenser (6) is equipped at the top of the second distillation column (5). The cold source channel of the second top condenser (6) is connected to the second distillation column (5). The bottom of the tower (5) is connected by the second liquid air delivery pipe (7). The cold source channel of the second tower top condenser (6) and the main heat exchanger (1) are provided with the first waste nitrogen delivery pipe (8). The outlet end of the first waste nitrogen delivery pipe (8) is provided with the first turbine expander (9). The first waste nitrogen delivery pipe (8), the second liquid air delivery pipe (7) and the first liquid air delivery pipe (4) are provided with the supercooler (10). The first turbine expander (9), the supercooler (10) and the main heat exchanger (1) are provided with the second waste nitrogen delivery pipe (11).
2. The nitrogen generation apparatus for low-temperature distillation according to claim 1, characterized in that: Liquid level sensors (12) are respectively installed at the bottom of the first distillation column (2), the bottom of the second distillation column (5), the cold source channel of the first top condenser (3), and the cold source channel of the second top condenser (6). A first regulating valve (13) is respectively installed on the first liquid air delivery pipe (4) and the second liquid air delivery pipe (7).
3. The nitrogen production apparatus for low-temperature distillation according to claim 1, characterized in that: The heat source channels of the first top condenser (3), the second top condenser (6), and the main heat exchanger (1) are provided with a finished nitrogen delivery pipe (14). A second regulating valve (15) is provided on the finished nitrogen delivery pipe (14) between the outlet end of the main heat exchanger (1) and the finished nitrogen delivery pipe (14). A first nitrogen delivery branch pipe (16) is provided between the top of the first distillation column (2) and the finished nitrogen delivery pipe (14) and between the top of the second distillation column (5) and the finished nitrogen delivery pipe (14). A first check valve (17) is provided on each first nitrogen delivery branch pipe (16). A second nitrogen delivery branch pipe (18) is provided between the heat source channel of the second top condenser (6) and the finished nitrogen delivery pipe (14) and between the finished nitrogen delivery pipe (14) and the heat source channel of the first top condenser (3). A third regulating valve (19) is provided on each second nitrogen delivery branch pipe (18).
4. The nitrogen generation apparatus for low-temperature distillation according to claim 1, characterized in that: A liquid nitrogen delivery main pipe (20) is provided at the outlet end of the heat source channel of the first top condenser (3) and the outlet end of the heat source channel of the second top condenser (6). The liquid nitrogen delivery main pipe (20) and the outlet end of the heat source channel of the first top condenser (3) are connected by liquid nitrogen delivery branch pipes (21). A second check valve (22) is provided on each liquid nitrogen delivery branch pipe (21). A fourth regulating valve (23) is provided on the liquid nitrogen delivery main pipe (20). The liquid nitrogen delivery main pipe (20) and the top of the first distillation column (2) are connected by liquid nitrogen reflux pipes (24). A fifth regulating valve (25) is provided on each liquid nitrogen reflux pipe (24).
5. The nitrogen production apparatus for low-temperature distillation according to claim 1, characterized in that: The first distillation column (2) is provided with a first packing layer (27). The first distillation column (2) below the first packing layer (27) and the main heat exchanger (1) are provided with a raw material air conveying main pipe (26). The second distillation column (5) is provided with a second packing layer (28) and a third packing layer (29) from bottom to top. The top of the cold source channel of the second distillation column (5) below the second packing layer (28) and the first column top condenser (3) are connected by a third waste nitrogen conveying pipe (30).
6. The nitrogen production apparatus for low-temperature distillation according to claim 5, characterized in that: The inlet end of the raw material air conveying main pipe (26) between the inlet end of the raw material air conveying main pipe (26) and the main heat exchanger (1) is provided with the inlet end of the raw material air conveying branch pipe (31). The raw material air conveying branch pipe (31) between the raw material air conveying main pipe (26) and the main heat exchanger (1) is provided with a sixth regulating valve (32). The outlet end of the second distillation column (5) between the second packing layer (28) and the third packing layer (29) and the raw material air conveying branch pipe (31) are connected. The feed air delivery branch pipe (31) is connected and arranged in sequence along the direction from near the second distillation column (5) to away from the second distillation column (5). It includes the expansion end of the second turbine expander (33), the heat exchanger (34) after the machine, the booster end of the second turbine expander (33), the booster unit (35) and the seventh regulating valve (36). The feed air delivery branch pipe (31) between the expansion end of the second turbine expander (33) and the heat exchanger (34) after the machine is installed on the main heat exchanger (1).