Variable-load air separation rectification device

Abstract

The utility model relates to a variable-load air separation rectification device which comprises a main rectification tower and a compressed air conveying header pipe, and the main rectification tower comprises an upper tower, a main condensation heat exchanger and a lower tower. A compressed air conveying header pipe is provided with a first compressed air conveying branch pipe, a turbo expander, a machine rear heat exchanger, a second compressed air conveying branch pipe and a third compressed air conveying branch pipe, the second compressed air conveying branch pipe is communicated with an upper tower through the expansion end of the turbo expander, and the first compressed air conveying branch pipe is communicated with a lower tower. The main condensing heat exchanger is communicated with an auxiliary rectifying tower, the auxiliary rectifying tower comprises a packed tower and a tower bottom evaporator, the tower bottom evaporator is communicated with the main condensing heat exchanger through a crude oxygen conveying pipe, a third compressed air conveying branch pipe is communicated with the tower bottom evaporator, and the lower tower is communicated with the packed tower through a waste liquid nitrogen conveying pipe. The finished product oxygen output can be conveniently adjusted. The utility model has the advantages of convenient adjustment and wide market prospect.

Description

Technical Field

[0001] The utility model relates to the field of variable load air separation and distillation equipment, in particular to a variable load air separation and distillation device. Background Art

[0002] Cryogenic distillation is also known as deep cold separation. The principle of deep cold air separation is to use air as raw material, compress, purify, and use heat exchange to liquefy the air into liquid air. Liquid air is mainly a mixture of liquid oxygen and liquid nitrogen. The different boiling points of liquid oxygen and liquid nitrogen are used to separate them through distillation to obtain nitrogen and oxygen. Specifically, the raw air is filtered out of dust and mechanical impurities by a self-cleaning filter, and then enters the main air compressor. The compressed gas is cooled by the air pre-cooling device and sent to the purification device to remove impurities such as water and carbon dioxide to form compressed air after adsorption. The compressed air after adsorption is sent to the distillation tower as raw material for low-temperature distillation after heat exchange with other gas media through the main heat exchanger. The ordinary distillation tower for nitrogen and oxygen separation includes an upper tower, a main condensing heat exchanger and a lower tower from top to bottom. After the raw materials are sent to the distillation tower for distillation, the upper tower produces finished nitrogen and finished oxygen, and the main condensing heat exchanger produces finished liquid oxygen and finished liquid nitrogen. The upper tower uses the oxygen-rich liquid air transported from the lower tower to the upper tower, and uses the oxygen-rich liquid air entering the upper tower to fully exchange heat with the gas evaporated from the main condensing evaporator and the liquid nitrogen refluxed to the upper tower, and then produces finished nitrogen, finished oxygen and finished liquid oxygen. However, for a simplified air separation device that simply realizes nitrogen and oxygen separation without further separating the remaining low-content gases, the upper tower requires more theoretical plates to separate finished oxygen and finished liquid oxygen that meet national standards. The increase in the number of theoretical plates of the upper tower will directly lead to an increase in the tower height of the upper tower. It is difficult to transport the oxygen-enriched liquid air from the lower tower to the upper tower using only the pressure of the lower tower itself. It is usually necessary to add a low-temperature booster pump to the oxygen-enriched liquid air transportation pipeline to provide auxiliary power for the oxygen-enriched liquid air transported to the upper tower, so as to complete the process of transporting the oxygen-enriched liquid air from the lower tower to the upper tower.

[0003] At present, the product demand of steel production enterprises for cryogenic air separation units is that the cryogenic air separation units should be able to produce a large amount of finished nitrogen and a large amount of finished oxygen, while finished liquid nitrogen and finished liquid oxygen are produced as by-products. Since blast furnaces have a demand for oxygen-enriched combustion-supporting gas, one of the major functions of finished oxygen is to be used as the oxygen source for oxygen-enriched combustion-supporting gas. Since the operation of blast furnaces is intermittent, the air separation cryogenic distillation units used in conjunction with steel production enterprises have corresponding requirements for variable loads, so as to meet the needs of continuously providing sufficient oxygen during the operation of the blast furnace to achieve sufficient supply of oxygen-enriched combustion-supporting gas, and to reduce the oxygen supply during the shutdown stage of the blast furnace to avoid the waste of produced oxygen. However, it is difficult to provide a higher load change rate in order to meet the normal operation of the cryogenic distillation unit by only using a cryogenic distillation unit including an upper tower, a main condenser evaporator and a lower tower. In the current process, although the company's demand for oxygen can be met by vaporizing the finished liquid oxygen and merging the vaporized oxygen into the finished oxygen delivery pipe, the process of vaporizing the finished oxygen is usually maintained outside the cold box, and the vaporization process also requires additional heat energy to be realized, resulting in excessive energy consumption. Therefore, it is a technical problem worthy of improvement to facilitate the adjustment of the output of the finished oxygen without affecting the main process of nitrogen and oxygen separation, so as to make it more convenient for steel production enterprises to use the cryogenic air separation unit to supply oxygen, thereby facilitating the improvement of the market competitiveness of the cryogenic distillation unit. Summary of the invention

[0004] In view of the deficiencies in the prior art, the utility model provides a variable load air fractionation and distillation device which is convenient for adjusting the output of finished oxygen, so as to overcome the defects in the prior art.

[0005] The technical solution adopted by the utility model is: a variable load air separation distillation device, including a main distillation tower and a compressed air delivery main pipe, the main distillation tower includes an upper tower, a main condensing heat exchanger and a lower tower from top to bottom, the compressed air delivery main pipe is sequentially provided with an inlet end of a first compressed air delivery branch pipe, a booster end of a turbine expander, a post-machine heat exchanger, an inlet end of a second compressed air delivery branch pipe and an inlet end of a third compressed air delivery branch pipe along the direction from the inlet end of the compressed air delivery main pipe to the outlet end of the compressed air delivery main pipe, the inlet end of the second compressed air delivery branch pipe and the inlet end of the third compressed air delivery branch pipe, the inlet end of the second compressed air delivery branch pipe and the inlet end of the third compressed air delivery branch pipe. The outlet end is connected to the expansion end inlet of the turbine expander, the expansion end outlet of the turbine expander is connected to the upper tower, the outlet end of the first compressed air delivery branch pipe is connected to the lower tower, the cold source channel of the main condensing heat exchanger is connected to the auxiliary distillation tower, the auxiliary distillation tower includes a packed tower and a bottom evaporator arranged on the bottom end of the packed tower, the cold source channel of the bottom evaporator and the cold source channel of the main condensing heat exchanger are connected through a crude oxygen delivery pipe, the outlet end of the third compressed air delivery branch pipe is connected to the heat source channel of the bottom evaporator, and the lower tower and the packed tower are connected through a dirty liquid nitrogen delivery pipe.

[0006] Preferably, the first compressed air delivery branch pipe, the second compressed air delivery branch pipe and the third compressed air delivery branch pipe are respectively provided with a first regulating valve and a first gas flow sensor.

[0007] Preferably, a liquid nitrogen delivery main pipe is provided at the outlet of the heat source channel of the main condensing heat exchanger, and the liquid nitrogen delivery main pipe is provided with an inlet end of a first liquid nitrogen reflux pipe, an inlet end of a second liquid nitrogen reflux pipe and a second regulating valve in sequence along a direction from close to the main condensing heat exchanger to far away from the main condensing heat exchanger, and a third regulating valve is provided on the first liquid nitrogen reflux pipe and the second liquid nitrogen reflux pipe, respectively. The top of the lower tower is connected to the inlet of the heat source channel of the main condensing heat exchanger, the outlet end of the first liquid nitrogen reflux pipe is connected to the top of the lower tower, the outlet end of the second liquid nitrogen reflux pipe is connected to the top of the upper tower, and oxygen-enriched liquid air delivery pipes are provided on the lower tower and the upper tower, and a fourth regulating valve is provided on the oxygen-enriched liquid air delivery pipe.

[0008] Preferably, the inlet end of the dirty liquid nitrogen delivery pipe is located between the outlet end of the first compressed air delivery branch pipe and the outlet end of the first liquid nitrogen reflux pipe, a fifth regulating valve is provided on the dirty liquid nitrogen delivery pipe, an inlet end of the liquefied air delivery pipe is provided on the outlet of the heat source channel of the tower bottom evaporator, the lower tower between the inlet end of the dirty liquid nitrogen delivery pipe and the outlet end of the first compressed air delivery branch pipe is connected to the outlet end of the liquefied air delivery pipe, and a sixth regulating valve is provided on the liquefied air delivery pipe.

[0009] Preferably, a dirty nitrogen gas delivery main pipe is provided on the upper tower, a subcooler is provided on the liquid nitrogen delivery main pipe between the inlet end of the first liquid nitrogen reflux pipe and the second liquid nitrogen reflux pipe, the oxygen-enriched liquid air delivery pipe and the dirty nitrogen gas delivery main pipe, an inlet end of the dirty nitrogen gas delivery branch pipe is provided on the top of the packed tower, and the subcooler is connected to the outlet end of the dirty nitrogen gas delivery main pipe and the dirty nitrogen gas delivery branch pipe between the upper tower.

[0010] Preferably, an oxygen delivery main pipe is provided at the bottom of the packed tower, and an online chromatograph, an oxygen delivery branch pipe, a seventh regulating valve and a second gas flow sensor are sequentially provided on the oxygen delivery main pipe along the direction from close to the packed tower to far away from the packed tower, an eighth regulating valve and a third gas flow sensor are provided on the oxygen delivery branch pipe, and a liquid oxygen delivery pipe is provided at the bottom of the cold source channel of the evaporator at the bottom of the tower, and a ninth regulating valve is provided on the liquid oxygen delivery pipe.

[0011] Preferably, the cold source channel of the tower bottom evaporator, the cold source channel of the main condensing heat exchanger and the bottom of the lower tower are respectively provided with liquid level sensors, and the dirty liquid nitrogen delivery pipe is provided with a liquid flow sensor.

[0012] The utility model has the following beneficial effects: first, although the utility model adds a secondary distillation tower including a packing tower and a bottom evaporator, it is convenient to adjust the flow rate of the third compressed air delivered to the heat source channel of the bottom evaporator through the second heat source channel of the main heat exchanger through the third compressed air delivery branch pipe, so as to facilitate the adjustment of the flow rate of oxygen delivered through the oxygen delivery main pipe. Compared with the prior art, the heat produced by oxygen comes from the pressurized nitrogen entering the heat source channel of the main condensing heat exchanger, and the lower tower needs to be maintained in a suitable pressure range to maintain the normal distillation process of the tower at a continuous temperature. The oxygen flow rate of this product has a larger variable adjustment amount, so as to meet the changes in oxygen demand of steel production enterprises during different production periods, and further, the product does not deliver liquid oxygen products but liquid oxygen containing some nitrogen components through the cold source channel of the main condensing heat exchanger. Relatively speaking, the height of the upper tower is reduced, so that it is convenient to use the pressure of the lower tower itself to deliver oxygen-rich liquid air to the upper tower to participate in the distillation process of the upper tower.

[0013] Secondly, the oxygen delivery main pipe of the utility model is provided with an online chromatograph, an oxygen delivery branch pipe, a seventh regulating valve and a second gas flow sensor in sequence along the direction from close to the packed tower to far away from the packed tower. The online chromatograph is installed to facilitate the feedback of relevant component parameters, and the second gas flow sensor is installed to facilitate the feedback of relevant flow parameters.

[0014] Finally, the first compressed air delivery branch, the second compressed air delivery branch and the third compressed air delivery branch described in the utility model are respectively provided with a first regulating valve and a first gas flow sensor, so as to facilitate the adjustment of the flow rate of compressed air delivered through the first compressed air delivery branch, the second compressed air delivery branch and the third compressed air delivery branch respectively.

[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.

[0017] Figure 2 for Figure 1 A partial enlarged schematic diagram of detail A. DETAILED DESCRIPTION

[0018] like Figure 1 and Figure 2As shown, a variable load air separation and distillation device comprises a main distillation tower and a compressed air delivery main pipe 1, wherein the main distillation tower comprises an upper tower 2, a main condensing heat exchanger 3 and a lower tower 4 from top to bottom, wherein the compressed air delivery main pipe 1 is provided with an inlet end of a first compressed air delivery branch pipe 5, a booster end of a turbine expander 6, a post-machine heat exchanger 7, an inlet end of a second compressed air delivery branch pipe 8 and an inlet end of a third compressed air delivery branch pipe 9 in a direction from an inlet end of the compressed air delivery main pipe 1 to an outlet end of the compressed air delivery main pipe 1, wherein the outlet end of the second compressed air delivery branch pipe 8 is connected to an expansion end inlet of the turbine expander 6, and the turbine expander 6 is connected to a compressor end of the turbine expander 6. The expansion end outlet of the machine 6 is connected to the upper tower 2, the outlet end of the first compressed air delivery branch pipe 5 is connected to the lower tower 4, the cold source channel of the main condensing heat exchanger 3 is connected to the auxiliary distillation tower, the auxiliary distillation tower includes a packed tower 10 and a bottom evaporator 11 arranged at the bottom of the packed tower 10, the cold source channel of the bottom evaporator 11 is connected to the inner cavity of the packed tower 10, the cold source channel of the bottom evaporator 11 is connected to the cold source channel of the main condensing heat exchanger 3 through a crude oxygen delivery pipe 12, the outlet end of the third compressed air delivery branch pipe 9 is connected to the heat source channel of the bottom evaporator 11, and the lower tower 4 is connected to the packed tower 10 through a dirty liquid nitrogen delivery pipe 13. The first compressed air delivery branch pipe 5, the second compressed air delivery branch pipe 8 and the third compressed air delivery branch pipe 9 are respectively provided with a first regulating valve 14 and a first gas flow sensor 15.

[0019] Furthermore, a liquid nitrogen delivery main pipe 16 is provided at the outlet of the heat source channel of the main condensing heat exchanger 3. The liquid nitrogen delivery main pipe 16 is provided with an inlet end of a first liquid nitrogen reflux pipe 17, an inlet end of a second liquid nitrogen reflux pipe 18 and a second regulating valve 19 in sequence along the direction from close to the main condensing heat exchanger 3 to far away from the main condensing heat exchanger 3. The first liquid nitrogen reflux pipe 17 and the second liquid nitrogen reflux pipe 18 are respectively provided with a third regulating valve 20. The top of the lower tower 4 is connected to the inlet of the heat source channel of the main condensing heat exchanger 3, the outlet end of the first liquid nitrogen reflux pipe 17 is connected to the top of the lower tower 4, the outlet end of the second liquid nitrogen reflux pipe 18 is connected to the top of the upper tower 2, and oxygen-enriched liquid air delivery pipes 21 are provided on the lower tower 4 and the upper tower 2, and the oxygen-enriched liquid air delivery pipe 21 is provided with a fourth regulating valve 22. The inlet end of the dirty liquid nitrogen delivery pipe 13 is located between the outlet end of the first compressed air delivery branch pipe 5 and the outlet end of the first liquid nitrogen reflux pipe 17, and a fifth regulating valve 23 is provided on the dirty liquid nitrogen delivery pipe 13. The inlet end of the liquefied air delivery pipe 24 is provided at the outlet of the heat source channel of the tower bottom evaporator 11. The lower tower 4 between the inlet end of the dirty liquid nitrogen delivery pipe 13 and the outlet end of the first compressed air delivery branch pipe 5 and the outlet end of the liquefied air delivery pipe 24 are connected, and a sixth regulating valve 25 is provided on the liquefied air delivery pipe 24. The upper tower 2 is provided with a dirty nitrogen gas delivery main pipe 26, and a subcooler 27 is provided on the liquid nitrogen delivery main pipe 16 between the inlet end of the first liquid nitrogen reflux pipe 17 and the second liquid nitrogen reflux pipe 18, the oxygen-enriched liquid air delivery pipe 21 and the dirty nitrogen gas delivery main pipe 26. The top of the packed tower 10 is provided with an inlet end of a dirty nitrogen gas delivery branch pipe 28, and the subcooler 27 is connected to the outlet end of the dirty nitrogen gas delivery main pipe 26 and the dirty nitrogen gas delivery branch pipe 28 between the upper tower 2.

[0020] Furthermore, an oxygen delivery main pipe 29 is provided at the bottom of the packed tower 10, and an online chromatograph 30, an oxygen delivery branch pipe 31, a seventh regulating valve 32 and a second gas flow sensor 33 are sequentially provided on the oxygen delivery main pipe 29 along the direction from close to the packed tower 10 to away from the packed tower 10, an eighth regulating valve 34 and a third gas flow sensor 35 are provided on the oxygen delivery branch pipe 31, and a liquid oxygen delivery pipe 36 is provided at the bottom of the cold source channel of the tower bottom evaporator 11, and a ninth regulating valve 37 is provided on the liquid oxygen delivery pipe 36.

[0021] The cold source channel of the tower bottom evaporator 11, the cold source channel of the main condensing heat exchanger 3 and the bottom of the lower tower 4 are respectively provided with liquid level sensors 38, so as to facilitate the feedback of liquid level parameters; the dirty liquid nitrogen delivery pipe 13 is provided with a liquid flow sensor 39, and the crude oxygen delivery pipe 12 is provided with a tenth regulating valve 42. The first compressed air delivery branch pipe 5, the second compressed air delivery branch pipe 8, the third compressed air delivery branch pipe 9, the dirty nitrogen delivery main pipe 26 on the side of the subcooler 27 away from the upper tower 2, and the nitrogen delivery pipe 40 are provided with a main heat exchanger 41.

[0022] The usage of this product is as follows: Figure 1 and Figure 2 As shown, the following steps are included:

[0023] S1, the compressed air delivery main pipe 1 receives the purified compressed air delivered by the upstream purification system and is first divided into two parts, namely the first part of compressed air and the second part of compressed air. The first part of compressed air is delivered to the first compressed air delivery branch pipe 5 and then delivered to the first heat source channel of the main heat exchanger 41 and continuously delivered to the cold source of the main heat exchanger 41, and then delivered to the lower tower 4 as one of the distillation raw materials of the lower tower 4; the second part of compressed air continues to move forward along the compressed air delivery main pipe 1, first passes through the boosting end of the turbine expander 6 for re-pressurization, and then passes through the heat source channel of the post-machine heat exchanger 7 After countercurrent heat exchange with the cold source medium continuously delivered to the cold source channel of the post-machine heat exchanger 7, the compressed air is divided into two parts again, namely the third part of compressed air and the fourth part of compressed air. The third part of compressed air is delivered to the third compressed air delivery branch pipe 9 and then enters the second heat source channel of the main heat exchanger 41 and continuously delivered to the cold source of the main heat exchanger 41 for heat exchange, and finally delivered to the heat source channel of the bottom evaporator 11 and the medium continuously delivered to the cold source channel of the bottom evaporator 11 for heat exchange to form liquid air. Finally, it is delivered to the lower tower 4 through the liquefied air delivery pipe 24 as one of the distillation raw materials of the lower tower 4. The fourth part of compressed air is delivered to the second compressed air delivery branch pipe 8 and then delivered to the third heat source channel of the main heat exchanger 41 and continuously delivered to the cold source of the main heat exchanger 41 for heat exchange, and finally discharged from the high temperature area of ​​the main heat exchanger 41 and delivered to the expansion end of the turbine expander 6 for expansion and cooling, and then delivered to the upper tower 2 as one of the distillation raw materials of the upper tower 2.

[0024] S2, the first part of the compressed air is delivered to the lower tower 4 through the first compressed air delivery branch pipe 5 to form an ascending airflow of the lower tower 4, and the ascending airflow of the lower tower 4 is countercurrently heat exchanged with the liquid air delivered to the lower tower 4 through the liquefied air delivery pipe 24 and the reflux condensate of the lower tower 4 in turn during the continuous upward movement along the inner cavity of the lower tower 4. During the countercurrent heat exchange process between the liquid air delivered to the lower tower 4 through the liquefied air delivery pipe 24 and the reflux condensate of the lower tower 4 and the ascending airflow of the lower tower 4, the nitrogen component in the liquid air delivered to the lower tower 4 through the liquefied air delivery pipe 24 and the nitrogen component in part of the reflux condensate of the lower tower 4 are both vaporized and merged in the ascending airflow, and the oxygen component in the first part of the compressed air entering the lower tower 4 and the oxygen component in the first part of the compressed air delivered to the lower tower 4 through the liquefied air delivery pipe 24 are both vaporized and merged in the ascending airflow. The oxygen component in the liquid air of the lower tower 4 and the unvaporized part in the reflux condensate of the lower tower 4 together form the descending liquid flow of the lower tower 4. In the process of the descending liquid flow of the lower tower 4 descending along the inner cavity of the lower tower 4, the oxygen component in the descending liquid flow of the lower tower 4 continues to increase, and finally a first nitrogen enrichment zone is formed at the top of the lower tower 4 and an oxygen-rich liquid air enrichment zone is formed at the bottom of the lower tower 4, so that the nitrogen in the first nitrogen enrichment zone enters the heat source channel of the main condensing heat exchanger 3 through the top of the lower tower 4 as a heat source continuously transported to the main condensing heat exchanger 3, and the oxygen-rich liquid air in the oxygen-rich liquid air enrichment zone passes through the oxygen-rich liquid air transport pipe 21 and then passes through the first heat source channel of the subcooler 27 and the cold source continuously transported to the subcooler 27 for heat exchange and is transported to the upper tower 2 as one of the distillation raw materials of the upper tower 2. The dirty liquid nitrogen containing a small amount of oxygen component between the outlet end of the first compressed air delivery branch pipe 5 and the outlet end of the first liquid nitrogen reflux pipe 17 is delivered to the packed tower 10 through the dirty liquid nitrogen delivery pipe 13 as the reflux condensate of the packed tower 10.

[0025] S3, the fourth part of the compressed air sent to the upper tower 2 after expansion and cooling at the expansion end of the turbine expander 6 enters the upper tower 2 to form an ascending airflow of the upper tower 2. During the continuous upward process in the upper tower 2, the ascending airflow of the upper tower 2 successively countercurrently exchanges heat with the oxygen-rich liquid air entering the upper tower 2 through the oxygen-rich liquid air delivery pipe 21 and the reflux condensate delivered to the upper tower 2 through the second liquid nitrogen reflux pipe 18. The oxygen component in the fourth part of the compressed air entering the upper tower 2, the oxygen component in the oxygen-rich liquid air entering the upper tower 2 through the oxygen-rich liquid air delivery pipe 21 and the unvaporized part of the reflux condensate delivered to the upper tower 2 through the second liquid nitrogen reflux pipe 18 together constitute the descending liquid flow of the upper tower 2, and the nitrogen component in the fourth part of the compressed air entering the upper tower 2, the nitrogen component in the oxygen-rich liquid air entering the upper tower 2 through the oxygen-rich liquid air delivery pipe 21 and the vaporized part of the reflux condensate delivered to the upper tower 2 through the second liquid nitrogen reflux pipe 18 together constitute The rising airflow of the upper tower 2 finally reaches the second nitrogen enrichment zone at the top row of the upper tower 2, wherein part of the nitrogen containing impurities forms the first contaminated nitrogen and passes through the contaminated nitrogen delivery main pipe 26 and is delivered to the contaminated nitrogen delivery main pipe 26, and the remaining part of the nitrogen forms the finished nitrogen and is delivered to the nitrogen delivery pipe 40, and is delivered to the first cold source channel of the main heat exchanger 41 and the heat source continuously delivered to the main heat exchanger 41 through the nitrogen delivery pipe 40 for heat exchange, and finally is delivered to the user through the outlet end of the nitrogen delivery pipe 40, while the descending liquid flow of the upper tower 2 continues to descend and is finally continuously delivered to the cold source channel of the main condensing heat exchanger 3 and the heat source continuously delivered to the main condensing heat exchanger 3. After heat exchange, the nitrogen component in the descending liquid flow is further evaporated, and the gas is formed again and merged into the rising airflow of the upper tower 2, and finally liquid oxygen containing part of the nitrogen component is formed in the cold source channel of the main condensing heat exchanger 3, and the liquid oxygen is delivered to the cold source channel of the tower bottom evaporator 11 through the crude oxygen delivery pipe 12.

[0026] S4, the nitrogen in the first nitrogen enrichment zone enters the heat source channel of the main condensing heat exchanger 3 through the top of the lower tower 4 and is continuously transported to the cold source of the cold source channel of the main condensing heat exchanger 3 for heat exchange, and then the nitrogen transported to the heat source channel of the main condensing heat exchanger 3 is liquefied and transported outwardly through the liquid nitrogen transport main pipe 16 and divided into two parts, namely, the first part of liquid nitrogen and the second part of liquid nitrogen. The first part of liquid nitrogen is returned to the lower tower 4 through the first liquid nitrogen reflux pipe 17 as the reflux condensate of the lower tower 4, and the second part of liquid nitrogen enters the second heat source channel of the subcooler 27 and is continuously transported to the cold source of the subcooler 27 for heat exchange to form subcooled liquid nitrogen. The subcooled liquid nitrogen is again divided into two parts, namely, the third part of liquid nitrogen and the fourth part of liquid nitrogen. The third part of liquid nitrogen is returned to the upper tower 2 through the second liquid nitrogen reflux pipe 18 as the reflux condensate of the upper tower 2; the fourth part of liquid nitrogen is transported outwardly to the finished liquid nitrogen storage device through the liquid nitrogen transport main pipe 16 and transported outwardly as a liquid nitrogen product.

[0027] S5, after the liquid oxygen containing part of the nitrogen component transported to the cold source channel of the tower bottom evaporator 11 through the crude oxygen delivery pipe 12 and the heat source continuously delivered to the heat source channel of the tower bottom evaporator 11 are heat exchanged, the nitrogen component in the liquid oxygen containing part of the nitrogen component and part of the oxygen component form the rising airflow of the packed tower 10 and the reflux condensate of the packed tower 10 transported through the dirty liquid nitrogen delivery pipe 13 to form a countercurrent heat exchange. In this process, the nitrogen component in the reflux condensate of the packed tower 10 is vaporized, and the nitrogen component in the rising airflow is vaporized along with the heat source continuously delivered to the heat source channel of the tower bottom evaporator 11. Part of the impurity gas is combined into the ascending gas flow, while the oxygen component in the reflux condensate of the packed tower 10 remains in liquid form to form the descending liquid flow of the packed tower 10. In the process of the descending liquid flow of the packed tower 10 continuing to descend along the packed tower 10, the nitrogen component gradually decreases and the oxygen component gradually increases, and finally an oxygen enrichment zone is formed at the bottom of the packed tower 10, and a liquid oxygen enrichment zone is formed in the cold source channel of the tower bottom evaporator 11. The liquid oxygen in the liquid oxygen enrichment zone is transported to the finished liquid oxygen storage device through the liquid oxygen delivery pipe 36 as finished liquid oxygen for external transportation. The oxygen in the oxygen enrichment zone of the packed tower 10 is transported to the oxygen delivery main pipe 29 and is divided into two parts, namely the first part of oxygen and the second part of oxygen. The first part of oxygen is transported to the target user outside as finished oxygen through the outlet end of the oxygen delivery main pipe 29, and the second part of oxygen is transported to the outside through the oxygen delivery branch pipe 31 as the oxygen source of the oxygen-enriched combustion gas. As the rising airflow of the packed tower 10 continues to ascend, a nitrogen-enriched area containing impurities is formed at the top of the packed tower 10, and a second contaminated nitrogen is transported outward through the contaminated nitrogen transport branch pipe 28. The second contaminated nitrogen is transported to the contaminated nitrogen transport main pipe 26 and merged with the first contaminated nitrogen to form a third contaminated nitrogen. The third contaminated nitrogen continues to move along the contaminated nitrogen transport main pipe 26, passes through the cold source channel of the cooler 27 and the heat source continuously transported to the subcooler 27 for heat exchange, passes through the second cold source channel of the main heat exchanger 41 and the heat source continuously transported to the main heat exchanger 41 for heat exchange, and is then delivered to the contaminated nitrogen user.

[0028] Through this embodiment, although the product adds a secondary distillation tower including a packing tower 10 and a bottom evaporator 11, it is convenient to adjust the flow rate of the third compressed air delivered to the heat source channel of the bottom evaporator 11 through the third compressed air delivery branch pipe 9 through the second heat source channel of the main heat exchanger 41, so as to facilitate the adjustment of the flow rate of oxygen delivered through the oxygen delivery main pipe 29. Compared with the prior art, the heat produced by oxygen comes from the pressurized nitrogen entering the heat source channel of the main condensing heat exchanger 3, and the lower tower 4 needs to be maintained in a suitable pressure range to maintain the normal distillation process of the tower 4 at a continuous temperature. The oxygen flow rate of the product has a larger variable adjustment amount, so as to meet the changes in the oxygen demand of the steel production enterprise during different production periods, and further, the product delivers not liquid oxygen products but liquid oxygen containing some nitrogen components through the cold source channel of the main condensing heat exchanger 3, which relatively reduces the height of the upper tower 2, so as to facilitate the use of the pressure of the lower tower 4 itself to deliver oxygen-rich liquid air to the upper tower 2 to participate in the distillation process of the upper tower 2.

[0029] 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 variable load air separation and distillation device, comprising a main distillation tower and a compressed air delivery main pipe (1), wherein the main distillation tower comprises, from top to bottom, an upper tower (2), a main condensing heat exchanger (3) and a lower tower (4), characterized in that: The compressed air delivery main pipe (1) is provided with an inlet end of a first compressed air delivery branch pipe (5), a booster end of a turbine expander (6), a post-machine heat exchanger (7), an inlet end of a second compressed air delivery branch pipe (8), and an inlet end of a third compressed air delivery branch pipe (9) in sequence along the direction from the inlet end of the compressed air delivery main pipe (1) to the outlet end of the compressed air delivery main pipe (1). The outlet end of the second compressed air delivery branch pipe (8) is connected to the inlet end of the expansion end of the turbine expander (6), the outlet end of the expansion end of the turbine expander (6) is connected to the upper tower (2), and the first compressed air delivery branch pipe (5) is connected to the upper tower (2). The outlet end of the air delivery branch pipe (5) is connected to the lower tower (4); the cold source channel of the main condensing heat exchanger (3) is connected to the auxiliary distillation tower, the auxiliary distillation tower comprises a packing tower (10) and a bottom evaporator (11) arranged at the bottom end of the packing tower (10); the cold source channel of the bottom evaporator (11) and the cold source channel of the main condensing heat exchanger (3) are connected through a crude oxygen delivery pipe (12); the outlet end of the third compressed air delivery branch pipe (9) is connected to the heat source channel of the bottom evaporator (11); and the lower tower (4) and the packing tower (10) are connected through a dirty liquid nitrogen delivery pipe (13).

2. The variable load air fractionation and distillation device according to claim 1, characterized in that: The first compressed air delivery branch pipe (5), the second compressed air delivery branch pipe (8) and the third compressed air delivery branch pipe (9) are each provided with a first regulating valve (14) and a first gas flow sensor (15).

3. The variable load air fractionation and distillation device according to claim 1, characterized in that: A liquid nitrogen delivery pipe (16) is arranged at the outlet of the heat source channel of the main condensing heat exchanger (3); the liquid nitrogen delivery pipe (16) is provided with an inlet end of a first liquid nitrogen reflux pipe (17), an inlet end of a second liquid nitrogen reflux pipe (18), and a second regulating valve (19) in sequence along a direction from close to the main condensing heat exchanger (3) to far away from the main condensing heat exchanger (3); a third regulating valve (20) is arranged on the first liquid nitrogen reflux pipe (17) and the second liquid nitrogen reflux pipe (18); the top of the lower tower (4) is connected to the inlet of the heat source channel of the main condensing heat exchanger (3); the outlet end of the first liquid nitrogen reflux pipe (17) is connected to the top of the lower tower (4); the outlet end of the second liquid nitrogen reflux pipe (18) is connected to the top of the upper tower (2); oxygen-enriched liquid air delivery pipes (21) are arranged on the lower tower (4) and the upper tower (2); and a fourth regulating valve (22) is arranged on the oxygen-enriched liquid air delivery pipe (21).

4. The variable load air fractionation and distillation device according to claim 3, characterized in that: The inlet end of the dirty liquid nitrogen delivery pipe (13) is located between the outlet end of the first compressed air delivery branch pipe (5) and the outlet end of the first liquid nitrogen reflux pipe (17); a fifth regulating valve (23) is provided on the dirty liquid nitrogen delivery pipe (13); an inlet end of a liquefied air delivery pipe (24) is provided at the outlet of the heat source channel of the tower bottom evaporator (11); the lower tower (4) and the outlet end of the liquefied air delivery pipe (24) are connected between the inlet end of the dirty liquid nitrogen delivery pipe (13) and the outlet end of the first compressed air delivery branch pipe (5); and a sixth regulating valve (25) is provided on the liquefied air delivery pipe (24).

5. The variable load air fractionation and distillation device according to claim 3, characterized in that: The upper tower (2) is provided with a dirty nitrogen gas delivery main pipe (26); a subcooler (27) is provided on the liquid nitrogen delivery main pipe (16) between the inlet end of the first liquid nitrogen reflux pipe (17) and the second liquid nitrogen reflux pipe (18), the oxygen-enriched liquid air delivery pipe (21) and the dirty nitrogen gas delivery main pipe (26); an inlet end of a dirty nitrogen gas delivery branch pipe (28) is provided on the top of the packed tower (10); the subcooler (27) is connected to the outlet ends of the dirty nitrogen gas delivery main pipe (26) and the dirty nitrogen gas delivery branch pipe (28) between the upper tower (2).

6. The variable load air fractionation and distillation device according to claim 1, characterized in that: An oxygen delivery main pipe (29) is arranged at the bottom of the packed tower (10), and an online chromatograph (30), an oxygen delivery branch pipe (31), a seventh regulating valve (32) and a second gas flow sensor (33) are arranged in sequence on the oxygen delivery main pipe (29) in a direction from close to the packed tower (10) to far away from the packed tower (10); an eighth regulating valve (34) and a third gas flow sensor (35) are arranged on the oxygen delivery branch pipe (31); a liquid oxygen delivery pipe (36) is arranged at the bottom of the cold source channel of the tower bottom evaporator (11), and a ninth regulating valve (37) is arranged on the liquid oxygen delivery pipe (36).

7. The variable load air fractionation and distillation device according to claim 1, characterized in that: Liquid level sensors (38) are respectively provided on the cold source channel of the tower bottom evaporator (11), the cold source channel of the main condensing heat exchanger (3) and the bottom of the lower tower (4), and a liquid flow sensor (39) is provided on the dirty liquid nitrogen delivery pipe (13).

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