Compressed air supply device of air separation rectification system

Abstract

The utility model relates to a compressed air supply device of an air separation rectification system, which comprises an air delivery header pipe, a main heat exchanger and a rectification tower, the rectification tower comprises an upper tower, a main condensation evaporator and a lower tower, the air delivery header pipe is communicated with the lower tower, and the upper edge of the main heat exchanger is provided with a first regulating valve and a first air delivery branch pipe; the first air conveying branch pipe is communicated with the lower tower, a second adjusting valve, an air compressor unit, a second air conveying branch pipe, a third adjusting valve, a first turbo expander, a first auxiliary heat exchanger and a first pressure sensor are arranged on the first air conveying branch pipe, and the second air conveying branch pipe is communicated with the first turbo expander; the second air conveying branch pipe is provided with a fourth adjusting valve, the main heat exchanger and the first turbo expander are provided with third air conveying branch pipes, and the third air conveying branch pipes are communicated with the air conveying header pipe. The cooling capacity of liquid air conveyed to the rectifying tower can be reasonably adjusted, and the device is convenient to use and has wide market prospects.

Description

Technical Field

[0001] The utility model relates to the field of compressed air supply equipment for an air separation and distillation system, in particular to a compressed air supply device for an air separation and distillation system. Background Art

[0002] The cryogenic distillation method uses the different boiling points of nitrogen and other components in the air at the same pressure to separate them. Since the operating temperature is between -170℃ and 190℃, it is also called deep freezing method. For the production of nitrogen by cryogenic distillation, the main energy consumption is ultimately reflected in the operating pressure and extraction rate of the air. That is, for the same extraction rate, the higher the operating pressure, the higher the energy consumption per unit product. For the same operating pressure, the higher the extraction rate, the lower the energy consumption per unit product. In the distillation separation process, the extraction rate is related to the process composition and product purity. The specific process of the oxygen-nitrogen distillation system is to allow the expanded air from the expander and the liquid air from the main heat exchanger to enter the upper and lower towers at appropriate positions respectively. In the upper tower, the rising gas is fully in contact with the downstream liquid. After mass transfer and heat transfer, the purity of the nitrogen is higher near the top of the tower. After condensation by the main condenser evaporator, a liquid nitrogen product with qualified purity is obtained. At the same time, part of the liquid nitrogen absorbs the cold through the subcooler and is sent to the top of the upper tower through the throttle valve as reflux liquid, and the rest of the liquid nitrogen returns to the lower tower. The oxygen-rich liquid air produced in the lower tower is supercooled by the subcooler, and after throttling, it enters the upper tower from an appropriate position to continue to participate in distillation, and obtains product oxygen at the bottom of the upper tower. The product gas is heated to room temperature through the main heat exchanger and then sent out of the cold box, and then pressurized to the required pressure by the oxygen compressor and nitrogen compressor and sent to the storage tank. Finally, the product gas that meets the process requirements is obtained through pressure regulation and sent to the main process device.

[0003] The raw gas for nitrogen-oxygen distillation comes from the expanded air after expansion through the booster turbo expander to provide cooling. The booster turbo expander is a high-speed rotating thermal machine widely used in chemical, steel, aviation, energy and other industries. The booster turbo expander consists of a single-stage turbo expander and a single-stage centrifugal compressor located at the other end of the expander shaft as a load. When the gas is adiabatically expanded in the turbo expander, it does work to the outside, causing the temperature of the gas itself to drop; on the other hand, when the high-pressure airflow impacts the expander impeller, the impeller rotates at high speed, and drives the booster impeller at the other end through the main shaft to do work to the outside, so that the gas can achieve a pressurized effect. The principle is to use the speed change of the medium flow to convert energy.

[0004] During the start-up of the air-conditioning, the process is first continued until the lower tower can have a sufficient liquid level, and then further process adjustments are made to enable the distillation equipment to normally produce nitrogen and oxygen products. In the existing process, multiple booster turbine expanders work together to make the compressed air delivered to the distillation contain some liquid air, so that the liquid air enters the distillation tower in the start-up state, and the vaporization heat of the liquid air and its own liquid properties can be used to enable the lower tower to quickly reach the corresponding liquid level, and the oxygen-rich liquid air produced by the lower tower is delivered to the upper tower to realize the process of starting up and debugging the upper tower, thereby completing the start-up and debugging of the entire distillation tower. Theoretically, this process can shorten the start-up process, but it also has some disadvantages, that is, in the start-up process, in addition to gaseous compressed air, liquid compressed air is also delivered to the lower tower. During normal operation, if the delivery volume of the liquid compressed air delivered to the lower tower is not well controlled, it is easy to cause liquid flooding in the lower tower, that is, the liquid at the bottom of the lower tower exceeds the preset range, and the descending liquid flow does not complete the entire countercurrent heat exchange process, so that the purity of the oxygen-rich liquid air delivered from the lower tower to the upper tower does not meet the preset standard, affecting the output of nitrogen and oxygen products. Therefore, there is room for improvement in the prior art, so that the time for the bottom of the lower tower to reach the preset liquid level can be shortened during the start-up phase and the situation of liquid flooding in the lower tower caused by excessive liquid air delivery can be reduced during the normal production phase. Summary of the invention

[0005] In view of the deficiencies in the prior art, the utility model provides a compressed air supply device for an air fractionation and distillation system capable of reasonably adjusting the amount of cold air delivered to a distillation tower liquid, so as to overcome the defects in the prior art.

[0006] The technical solution adopted by the utility model is: a compressed air supply device for an air separation and distillation system, comprising an air delivery main pipe, a main heat exchanger and a distillation tower, wherein the distillation tower comprises an upper tower, a main condenser evaporator and a lower tower in sequence from top to bottom, the air delivery main pipe is connected with the lower tower, the air delivery main pipe on the side of the main heat exchanger away from the lower tower is provided with a first regulating valve and an inlet end of a first air delivery branch pipe in sequence along a direction from close to the main heat exchanger to far away from the main heat exchanger, the outlet end of the first air delivery branch pipe is connected with the lower tower, and the first air delivery branch pipe is provided with a second regulating valve, an air compressor in sequence along a direction from the air delivery main pipe to the lower tower group, the inlet end of the second air delivery branch, the third regulating valve, the boost end of the first turbine expander, the first auxiliary heat exchanger and the first pressure sensor, the part of the first air delivery branch between the first pressure sensor and the first auxiliary heat exchanger is installed on the main heat exchanger, the outlet end of the second air delivery branch is connected with the expansion end inlet of the first turbine expander, the part of the second air delivery branch is located on the main heat exchanger, the fourth regulating valve is arranged on the second air delivery branch, the main heat exchanger and the expansion end outlet of the first turbine expander are provided with a third air delivery branch, and the outlet end of the third air delivery branch is connected with the air delivery main pipe in the main heat exchanger.

[0007] Preferably, a liquid flow sensor, a fifth regulating valve, a liquid air booster pump, a gas-liquid separation tank, a first one-way valve, a second pressure sensor and a throttle valve are sequentially arranged on the air delivery main pipe on the side of the main heat exchanger close to the lower tower along the direction close to the lower tower to away from the lower tower. The gas phase outlet end of the gas-liquid separation tank and the upper tower are connected through a fourth air delivery branch pipe, and the fourth air delivery branch pipe is sequentially arranged with a sixth throttle valve and a third pressure sensor along the direction from the gas-liquid separation tank to the upper tower.

[0008] Preferably, liquid level sensors are respectively provided on the lower tower and the gas-liquid separation tank.

[0009] Preferably, the boost end of the second turbine expander and the second auxiliary heat exchanger are sequentially arranged on the first air delivery branch between the main heat exchanger and the first pressure sensor along the direction from the first auxiliary heat exchanger to the first pressure sensor, the outlet end of the third air delivery branch is connected with the air delivery main pipe between the low-temperature end of the main heat exchanger and the expansion end inlet of the second turbine expander through the fifth air delivery branch, the fifth air delivery branch is provided with a seventh regulating valve, the fifth air delivery branch between the seventh regulating valve and the second turbine expander and the first air delivery branch in the main heat exchanger are connected through the sixth air delivery branch, the sixth air delivery branch is provided with an eighth regulating valve, the air delivery main pipe between the main heat exchanger and the lower tower is connected with the expansion end outlet of the second turbine expander through the seventh air delivery branch, and the seventh air delivery branch is provided with a second one-way valve.

[0010] Preferably, a fourth pressure sensor is provided on the fifth air delivery branch between the sixth air delivery branch and the second turbine expander, and a fifth pressure sensor is provided on the seventh air delivery branch between the second one-way valve and the second turbine expander.

[0011] Preferably, a temperature sensor is provided on the sixth air delivery branch pipe and the fifth air delivery branch pipe between the second turbo expander.

[0012] The beneficial effects of the utility model are as follows: firstly, the utility model, through the present embodiment, utilizes a part of the compressed air pressurized by the air compressor unit to be delivered to the main heat exchanger and continuously delivered to the cold source of the main heat exchanger for heat exchange, and then delivered to the expansion end of the first turbine expander for expansion to perform work to form low-temperature compressed air, and finally delivered to the air delivery main pipe in the main heat exchanger, so that the temperature of the compressed air in the air delivery main pipe is greatly reduced, thereby reducing the final temperature of the compressed air delivered to the main heat exchanger for heat exchange through the air delivery main pipe, thereby facilitating the generation of more liquid compressed air after throttling by the throttle valve, so as to facilitate the delivery of more liquid compressed air to the lower tower.

[0013] Secondly, on the air delivery main pipe of the main heat exchanger close to the lower tower described in the utility model, a liquid flow sensor, a fifth regulating valve, a liquid air booster pump, a gas-liquid separation tank, a first one-way valve, a second pressure sensor and a throttle valve are sequentially arranged along the direction from close to the lower tower to away from the lower tower; the installation of the liquid flow sensor facilitates the feedback of the flow parameters of the liquid compressed air delivered to the lower tower.

[0014] Thirdly, the lower tower and the gas-liquid separation tank described in the utility model are respectively provided with liquid level sensors; the installation of the liquid level sensors facilitates the feedback of liquid level parameters.

[0015] The utility model has the advantages of simple structure, convenient operation, ingenious design, greatly improved working efficiency, good social and economic benefits, and is a product that is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the utility model. DETAILED DESCRIPTION

[0017] like Figure 1As shown, a compressed air supply device for an air separation and distillation system comprises an air delivery main pipe 1, a main heat exchanger 2 and a distillation tower, wherein the distillation tower comprises an upper tower 3, a main condenser evaporator 4 and a lower tower 5 from top to bottom, the air delivery main pipe 1 and the lower tower 5 are connected, and the air delivery main pipe 1 on the side of the main heat exchanger 2 away from the lower tower 5 is provided with a first regulating valve 6 and an inlet end of a first air delivery branch pipe 7 in sequence along a direction from close to the main heat exchanger 2 to away from the main heat exchanger 2, the outlet end of the first air delivery branch pipe 7 is connected to the lower tower 5, and the first air delivery branch pipe 7 is provided with a second regulating valve 8, an air compressor unit 9, and a second air delivery branch pipe 10 in sequence along a direction from the air delivery main pipe 1 to the lower tower 5. The inlet end, the third regulating valve 11, the boost end of the first turbine expander 12, the first auxiliary heat exchanger 13 and the first pressure sensor 14, the part of the first air delivery branch 7 between the first pressure sensor 14 and the first auxiliary heat exchanger 13 is installed on the main heat exchanger 2, the outlet end of the second air delivery branch 10 is connected to the expansion end inlet of the first turbine expander 12, the part of the second air delivery branch 10 is located on the main heat exchanger 2, the second air delivery branch 10 is provided with a fourth regulating valve 15, the main heat exchanger 2 and the expansion end outlet of the first turbine expander 12 are provided with a third air delivery branch 16, the outlet end of the third air delivery branch 16 is connected to the air delivery main pipe 1 in the main heat exchanger 2.

[0018] On the air delivery main pipe 1 of the main heat exchanger 2 near the lower tower 5, a liquid flow sensor 40, a fifth regulating valve 17, a liquid air booster pump 18, a gas-liquid separation tank 19, a first non-return valve 20, a second pressure sensor 21 and a throttle valve 22 are sequentially arranged in the direction from the lower tower 5 to the direction away from the lower tower 5. The gas phase outlet end of the gas-liquid separation tank 19 and the upper tower 3 are connected through the fourth air delivery branch pipe 23. The fourth air delivery branch pipe 23 is sequentially arranged with a sixth throttle valve 24 and a third pressure sensor 25 along the direction from the gas-liquid separation tank 19 to the upper tower 3. Liquid level sensors 26 are respectively arranged on the lower tower 5 and the gas-liquid separation tank 19.

[0019] The first air delivery branch pipe 7 between the main heat exchanger 2 and the first pressure sensor 14 is provided with the boost end of the second turbine expander 27 and the second auxiliary heat exchanger 28 in sequence along the direction from the first auxiliary heat exchanger 13 to the first pressure sensor 14. The outlet end of the third air delivery branch pipe 16 is connected with the air delivery main pipe 1 between the low-temperature end of the main heat exchanger 2 and the expansion end inlet of the second turbine expander 27 through the fifth air delivery branch pipe 29. The fifth air delivery branch pipe 29 is provided with a seventh regulating valve 30. The seventh regulating valve 30 is connected with the fifth air delivery branch pipe 29 between the second turbine expander 27 and the first air delivery branch pipe 7 in the main heat exchanger 2 through a sixth air delivery branch pipe 31. The sixth air delivery branch pipe 31 is provided with an eighth regulating valve 32. The air delivery main pipe 1 between the main heat exchanger 2 and the lower tower 5 is connected with the expansion end outlet of the second turbine expander 27 through a seventh air delivery branch pipe 33. The seventh air delivery branch pipe 33 is provided with a second check valve 34. A fourth pressure sensor 35 is provided on the sixth air delivery branch 31 and the fifth air delivery branch 29 between the second turbo expander 27, and a fifth pressure sensor 36 is provided on the second check valve 34 and the seventh air delivery branch 33 between the second turbo expander 27. A sixth pressure sensor 38 is provided on the second air delivery branch 10 between the first turbo expander 12 and the main heat exchanger 2, and a seventh pressure sensor 39 is provided on the third air delivery branch 16. A temperature sensor 37 is provided on the sixth air delivery branch 31 and the fifth air delivery branch 29 between the second turbo expander 27.

[0020] The usage of this product is as follows: Figure 1 As shown, the following steps are included:

[0021] S1, the air delivery main pipe 1 receives the purified compressed air 1 continuously delivered by the upstream purification system and divides it into two parts. The first part of the compressed air 1 continues to move along the air delivery main pipe 1 to the first heat source channel of the main heat exchanger 2; the second part of the compressed air 1 is delivered to the first air delivery branch pipe 7.

[0022] S2, the second part of compressed air 1 entering the first air delivery branch pipe 7 is converted into compressed air 2 after being pressurized by the air compressor unit 9 and then divided into two parts again, namely the first part of compressed air 2 and the second part of compressed air 2. The first part of compressed air 2 continues to move along the first air delivery branch pipe 7 and passes through the boosting end of the first turbine expander 12, the first auxiliary heat exchanger 13, the boosting end of the second turbine expander 27 and the second auxiliary heat exchanger 28 in sequence to complete two-stage boosting and then is sent to the second heat source channel of the main heat exchanger 2 and the cold source continuously delivered to the main heat exchanger 2 for heat exchange; the second part of compressed air 2 enters the second air delivery branch pipe 10 and passes through the third heat source channel of the main heat exchanger 2 and the cold source continuously delivered to the main heat exchanger 2 to complete heat exchange, and then is sent to the expansion end of the first turbine expander 12 for expansion and cooling, and then is sent to the air delivery main pipe 1 in the main heat exchanger 2 through the third air delivery branch pipe 16 to mix with the first part of compressed air 1, completing direct cooling of the first part of compressed air 1. Then compressed air is formed.

[0023] S3, the second part of compressed air 2 entering the third heat source channel of the main heat exchanger 2 is divided into two parts again, namely the first part of compressed air 3 and the second part of compressed air 3, the first part of compressed air 3 is transported to the fifth air transport branch 29 by the sixth air delivery branch 31, and the second part of compressed air 3 continues to move forward along the first air delivery branch 7 and is transported to the lower tower 5 as the gaseous distillation raw material of the lower tower 5; the first part of compressed air 1 and the second part of compressed air 2 are mixed to form compressed air 4, and are divided into two parts, namely the first part of compressed air 4 and the second part of compressed air 4, the first part of compressed air 4 is transported to the fifth air delivery branch 29 and is completely mixed with the first part of compressed air 3 The compressed air five is mixed to form compressed air five and then sent to the expansion end of the second turbine expander 27 for expansion and cooling. The compressed air five is expanded and cooled to form partially liquefied compressed air; the second part of compressed air four continues to pass along the air delivery main pipe 1 through the first heat source channel of the main heat exchanger 2 and then passes through the throttle valve 22 to form partially liquid compressed air, and then is mixed with the compressed air five after expansion and cooling and sent to the gas-liquid separation tank 19 for gas-liquid separation to form a gas phase part and a liquid phase part. The liquid phase part is pressurized by the liquid air booster pump 18 and sent to the lower tower 5 as the liquid distillation raw material of the lower tower 5, and the gas phase part is sent to the upper tower 3 through the fourth air delivery branch pipe 23 as the distillation raw material of the upper tower 3.

[0024] It should be noted that the ratio of the gaseous distillation raw material and the liquid distillation raw material entering the lower tower 5 can be adjusted according to the start-up process and based on the feedback parameters of the liquid level sensor 26 of the lower tower 5. Compared with the prior art, this product can provide corresponding liquid compressed air according to the actual working conditions during the start-up stage, thereby increasing the cooling capacity carried by the distillation raw material entering the lower tower 5, shortening the time required for the lower tower 5 to reach the preset liquid level height, and preparing for adjusting the product purity in the next stage.

[0025] Through this embodiment, a part of the compressed air pressurized by the air compressor unit 9 is delivered to the main heat exchanger 2 and continuously delivered to the cold source of the main heat exchanger 2 for heat exchange, and then delivered to the expansion end of the first turbine expander 12 for expansion and work to form low-temperature compressed air, and finally delivered to the air delivery main pipe 1 in the main heat exchanger 2, so that the temperature of the compressed air in the air delivery main pipe 1 is greatly reduced, thereby reducing the final temperature of the compressed air delivered to the main heat exchanger 2 for heat exchange through the air delivery main pipe 1, thereby facilitating the generation of more liquid compressed air after throttling by the throttle valve 22, so as to facilitate the delivery of more liquid compressed air to the lower tower 5.

[0026] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made based on the structures, features and principles described in the patent scope of the present invention should be included in the patent application scope of the present invention.

Claims

1. A compressed air supply device for an air separation and distillation system, comprising an air delivery main pipe (1), a main heat exchanger (2) and a distillation tower, wherein the distillation tower comprises, from top to bottom, an upper tower (3), a main condenser evaporator (4) and a lower tower (5), the air delivery main pipe (1) and the lower tower (5) being connected, characterized in that: On the air delivery main pipe (1) on the side of the main heat exchanger (2) away from the lower tower (5), a first regulating valve (6) and an inlet end of a first air delivery branch pipe (7) are sequentially arranged along a direction from close to the main heat exchanger (2) to away from the main heat exchanger (2); an outlet end of the first air delivery branch pipe (7) is connected to the lower tower (5); and the first air delivery branch pipe (7) is sequentially arranged along a direction from the air delivery main pipe (1) to the lower tower (5) with a second regulating valve (8), an air compressor unit (9), an inlet end of a second air delivery branch pipe (10), a third regulating valve (11), a boost end of a first turbine expander (12), a first auxiliary heat exchanger (13) and a first pressure sensor. (14), a portion of the first air delivery branch pipe (7) between the first pressure sensor (14) and the first auxiliary heat exchanger (13) is installed on the main heat exchanger (2), an outlet end of the second air delivery branch pipe (10) is connected to an expansion end inlet of the first turbine expander (12), a portion of the second air delivery branch pipe (10) is located on the main heat exchanger (2), a fourth regulating valve (15) is provided on the second air delivery branch pipe (10), a third air delivery branch pipe (16) is provided at the expansion end outlets of the main heat exchanger (2) and the first turbine expander (12), and an outlet end of the third air delivery branch pipe (16) is connected to an air delivery main pipe (1) in the main heat exchanger (2).

2. The compressed air supply device for the air fractionation and distillation system according to claim 1, characterized in that: On the main air delivery pipe (1) on the side of the main heat exchanger (2) close to the lower tower (5), a liquid flow sensor (40), a fifth regulating valve (17), a liquid air booster pump (18), a gas-liquid separation tank (19), a first non-return valve (20), a second pressure sensor (21) and a throttle valve (22) are sequentially arranged in a direction from close to the lower tower (5) to far from the lower tower (5); the gas phase outlet end of the gas-liquid separation tank (19) and the upper tower (3) are connected via a fourth air delivery branch pipe (23); and the fourth air delivery branch pipe (23) is sequentially arranged with a sixth throttle valve (24) and a third pressure sensor (25) in a direction from the gas-liquid separation tank (19) to the upper tower (3).

3. The compressed air supply device for the air fractionation and distillation system according to claim 2, characterized in that: The lower tower (5) and the gas-liquid separation tank (19) are each provided with a liquid level sensor (26).

4. The compressed air supply device for the air fractionation and distillation system according to claim 1, characterized in that: The first air delivery branch pipe (7) between the main heat exchanger (2) and the first pressure sensor (14) is provided with a boost end of a second turbine expander (27) and a second auxiliary heat exchanger (28) in sequence along the direction from the first auxiliary heat exchanger (13) to the first pressure sensor (14); the outlet end of the third air delivery branch pipe (16) is connected to the air delivery main pipe (1) between the low-temperature end of the main heat exchanger (2) and the expansion end inlet of the second turbine expander (27) via a fifth air delivery branch pipe (29); and the fifth air delivery branch pipe (29) is provided with a seventh regulating The seventh regulating valve (30) is connected to the fifth air delivery branch pipe (29) between the seventh regulating valve (30) and the second turbine expander (27) and the first air delivery branch pipe (7) in the main heat exchanger (2) through a sixth air delivery branch pipe (31), and an eighth regulating valve (32) is provided on the sixth air delivery branch pipe (31). The air delivery main pipe (1) between the main heat exchanger (2) and the lower tower (5) and the expansion end outlet of the second turbine expander (27) are connected through a seventh air delivery branch pipe (33), and a second check valve (34) is provided on the seventh air delivery branch pipe (33).

5. The compressed air supply device for the air fractionation and distillation system according to claim 4, characterized in that: A fourth pressure sensor (35) is provided on the fifth air delivery branch pipe (29) between the sixth air delivery branch pipe (31) and the second turbine expander (27), and a fifth pressure sensor (36) is provided on the seventh air delivery branch pipe (33) between the second one-way valve (34) and the second turbine expander (27).

6. The compressed air supply device for the air fractionation and distillation system according to claim 4, characterized in that: A temperature sensor (37) is provided on the fifth air delivery branch pipe (29) between the sixth air delivery branch pipe (31) and the second turbo expander (27).

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