An air separation system

Abstract

The present invention discloses an air separation system, comprising: an air filter, a first air compressor, a precooler, a purifier, a main heat exchanger, a first expander, a second expander, a first subcooler, a second air compressor, a fourth expander, a fifth expander, a precooler, a first subcooler, a second subcooler, and a nitrogen storage tank; the upper refrigerant outlet of the main heat exchanger is connected to the first expander, the middle refrigerant outlet of the main heat exchanger is connected to the second expander, and the lower refrigerant outlet of the main heat exchanger is connected to the first subcooler; the inlet and outlet of the precooler are respectively connected to the boosting section of the fourth expander and the boosting section of the fifth expander, and the inlet and outlet of the second subcooler are respectively connected to the expansion section of the fourth expander and the expansion section of the fifth expander. The refrigeration capacity of the gas is greatly increased, thereby achieving the purpose of energy saving and consumption reduction, and reducing power loss.

Description

Technical Field

[0001] The present invention relates to the technical field of air separation equipment, in particular to an air separation system. Background Art

[0002] Air separation systems use air as a raw material, converting it into liquid at low temperatures. The distillation process then separates inert gases such as oxygen, nitrogen, and argon. During the production process, air filtration and cooling, along with cryogenic nitrogen separation, play a crucial role in the overall process. However, current air separation systems consume a lot of energy, underutilize excess heat, and suffer from low efficiency, leading to low product yields. Summary of the Invention

[0003] To address the aforementioned technical issues, the present invention provides an air separation system. To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is provided below. This summary is not intended to be a comprehensive review, identify key or essential components, or delineate the scope of protection for these embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the detailed description that follows.

[0004] The present invention adopts the following technical solutions:

[0005] The present invention provides an air separation system, comprising: an air filter, a first air compressor, a precooler, a purifier, a main heat exchanger, a first expander, a second expander, a first subcooler, a second air compressor, a fourth expander, a fifth expander, a precooler, a first subcooler, a second subcooler, and a nitrogen storage tank;

[0006] The air passes through the air filter to remove impurities and then enters the first air compressor. After being compressed and cooled by the first air compressor, the air enters the precooler. After being cooled and dehydrated, the air enters the purifier. The air from which moisture and carbon dioxide have been removed by the purifier is transported to the first air compressor. A portion of the compressed air after being compressed and cooled enters the main heat exchanger.

[0007] The upper refrigerant outlet of the main heat exchanger is connected to the first expander, the middle refrigerant outlet of the main heat exchanger is connected to the second expander, and the lower refrigerant outlet of the main heat exchanger is connected to the first subcooler;

[0008] The nitrogen output from the top of the distillation tower enters the second air compressor for pressurization, the inlet and outlet of the precooler are respectively connected to the boosting section of the fourth expander and the boosting section of the fifth expander, the boosting section of the fifth expander is connected to the first-stage subcooler, the first-stage subcooler is connected to the expansion section of the fourth expander, the inlet and outlet of the second-stage subcooler are respectively connected to the expansion section of the fourth expander and the expansion section of the fifth expander, and the expansion section of the fifth expander is connected to the nitrogen storage tank.

[0009] Furthermore, the air separation system further includes: a booster compressor and a third expander; another part of the compressed air compressed and cooled by the first air compressor enters the booster compressor and the third expander in sequence, and the compressed air after two pressurizations is transported to the distillation tower cold box.

[0010] Furthermore, a backflow air input port is provided on the first air compressor, and the output port of the purifier and the output port of the fractionation tower cold box are both connected to the backflow air input port of the first air compressor.

[0011] Furthermore, the air separation system also includes: a circulating compressor; the outlet of the first expander is connected to the middle refrigerant inlet of the main heat exchanger, the inlet of the circulating compressor is connected to the middle refrigerant outlet of the main heat exchanger, and the outlet of the circulating compressor is connected to the upper refrigerant inlet of the main heat exchanger.

[0012] Furthermore, the second expander is provided with a first outlet, a second outlet and a third outlet; the first outlet of the second expander is connected to the circulation compressor; the second outlet of the second expander is connected to the first condenser evaporator, and the first condenser evaporator is connected to the upper tower of the distillation tower; the third outlet of the second expander is connected to the lower tower of the distillation tower.

[0013] Furthermore, the air separation system further includes: a second subcooler, a third subcooler and a storage tank; the inlet of the second subcooler is connected to the liquid air outlet at the bottom of the lower tower of the distillation tower, and the outlet of the second subcooler is connected to the upper tower of the distillation tower; the liquid oxygen outlet at the bottom of the upper tower of the distillation tower is connected to the inlet of the third subcooler, and the outlet of the third subcooler is connected to the storage tank.

[0014] Furthermore, the air separation system further includes: an auxiliary heat exchanger and an oxygen pipeline network; the bottom oxygen outlet of the upper tower of the distillation tower is connected to the refrigerant inlet of the auxiliary heat exchanger, and the refrigerant outlet of the auxiliary heat exchanger is connected to the oxygen pipeline network.

[0015] Furthermore, the air separation system further includes: a second condenser-evaporator and a subcooler; the nitrogen output from the top of the lower tower of the distillation tower enters the second condenser-evaporator to be condensed into liquid nitrogen, and the condensed liquid nitrogen is transported to the subcooler for subcooling.

[0016] Furthermore, the subcooler is provided with a first outlet, a second outlet and a third outlet; the first outlet of the subcooler is connected to the inlet of the upper tower of the distillation tower; the second outlet of the subcooler is connected to the product liquid nitrogen storage tank; and the third outlet of the subcooler is connected to the argon system.

[0017] Furthermore, the air separation system further includes: a liquid nitrogen subcooler and a heat exchange device; the contaminated nitrogen gas extracted from the top of the distillation tower is transported to the liquid nitrogen subcooler, the outlet of the liquid nitrogen subcooler is connected to the refrigerant inlet of the heat exchange device, and the refrigerant outlet of the heat exchange device is connected to the inlet of the water cooling tower.

[0018] The beneficial effects brought about by the present invention are: the filtration part and the cooling part are redistributed and performed alternately, and the main heat exchanger is used for heat exchange to provide temperature control conditions for other processes in the air separation system. At the same time, the expander series boosting technology is used to replace the simple chiller cooling, greatly improving the refrigeration capacity of the gas, thereby achieving the purpose of energy saving and consumption reduction and reducing power loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 is a schematic diagram of an air separation system of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the purifier of the present invention. DETAILED DESCRIPTION

[0022] The following describes embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the embodiments described are only some of the embodiments of the present invention, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0023] like Figure 1-2As shown, in some illustrative embodiments, the present invention provides an air separation system, including: an air filter 101, a first air compressor 102, a precooler 103, a purifier 104, a main heat exchanger 105, a first expander 106, a second expander 107, a first subcooler 108, a booster 110, a third expander 111, a circulating compressor 112, a second air compressor 201, a fourth expander 202, a fifth expander 203, a precooler 204, a first subcooler 205, a second subcooler 206, and a nitrogen storage tank 207.

[0024] The outlet of the air filter 101 is connected to the inlet of the first air compressor 102 , the outlet of the first air compressor 102 is connected to the inlet of the precooler 103 , and the outlet of the precooler 103 is connected to the inlet of the purifier 104 .

[0025] The air passes through the air filter 101, removes most of the dust and other mechanical impurities in the air, and is then sucked into the first air compressor 102. After the first stage of the combined first air compressor 102, the secondary compression and secondary cooling, the air pressure is increased to ~0.5MPa.

[0026] The compressed air then enters precooler 103. There, it exchanges heat and mass with low-temperature water from a cooling tower, cooling the air from ~40°C to ~12°C. The air's moisture content also decreases from its saturated moisture content at ~40°C to that at ~12°C. The majority of the condensed moisture in the air is removed in the entrainment filter in precooler 103, significantly improving the operating conditions of the downstream purifier 104 and increasing the molecular sieve's ability to adsorb carbon dioxide.

[0027] After cooling and removing water, the compressed air enters the purifier 104. As it passes through the adsorption cylinder, the remaining water vapor and carbon dioxide in the air are adsorbed by the adsorbents activated alumina and 13X molecular sieve, respectively. A reverse air inlet is provided on the first air compressor 102. The outputs of the purifier 104 and the fractionator cold box 109 are both connected to this reverse air inlet of the first air compressor 102. The air, completely free of water and carbon dioxide, is then fed into the second stage of the modular first air compressor 102 along with the reverse air from the fractionator cold box 109. After four stages of compression and cooling, the pressure is raised to ~2.7 MPa.

[0028] The compressed air compressed and cooled by the first air compressor 102 is divided into two parts. One part of the compressed air directly enters the main heat exchanger 105 , and the other part of the compressed air enters the booster 110 .

[0029] Another part of the compressed air compressed and cooled by the first air compressor 102 enters the booster 110 to boost the compressed air to ~4.4 MPa. The outlet of the booster 110 is connected to the inlet of the third expander 111. After cooling, it enters the third expander 111 to boost the compressed air to ~6.3 MPa. After cooling again, it enters the distillation tower cold box 109.

[0030] The upper refrigerant outlet of the main heat exchanger 105 is connected to the first expander 106 , the middle refrigerant outlet of the main heat exchanger 105 is connected to the second expander 107 , and the lower refrigerant outlet of the main heat exchanger 105 is connected to the first subcooler 108 .

[0031] The output port of the first expander 106 is connected to the middle refrigerant inlet of the main heat exchanger 105. The compressed air compressed and cooled by the first air compressor 102 is divided into two parts. One part of the compressed air enters the main heat exchanger 105 directly, is extracted from the upper part of the main heat exchanger 105, enters the first expander 106 for expansion and cooling, and then enters the middle part of the main heat exchanger 105 to provide cooling capacity to the upper middle part of the main heat exchanger 105.

[0032] The inlet of the circulating compressor 112 is connected to the middle refrigerant outlet of the main heat exchanger 105, and the outlet of the circulating compressor 112 is connected to the upper refrigerant inlet of the main heat exchanger 105. Air drawn from the upper portion of the main heat exchanger 105 enters the first expander 106 for expansion and refrigeration, then enters the middle portion of the main heat exchanger 105 to provide cooling to the upper middle portion of the main heat exchanger 105. After being reheated by the positive air flow, it enters the circulating compressor 112, where it is pressurized to the specified pressure and circulated again.

[0033] A portion of the pressurized air is extracted from the middle of the main heat exchanger 105 and enters the second expander 107 for expansion and refrigeration, providing the required cooling capacity for the device. After expansion, the air is divided into three parts and output from the three outlets of the second expander 107. The second expander 107 has a first outlet, a second outlet, and a third outlet.

[0034] The first outlet of the second expander 107 is connected to the circulation compressor 112. This part of the compressed air enters the main heat exchanger 105 and is reheated by the positive flow air. It then enters the circulation compressor 112 and is pressurized to the specified pressure and circulated again.

[0035] The second outlet of the second expander 107 is connected to the first condenser evaporator 113, and the first condenser evaporator 113 is connected to the upper tower 114 of the distillation tower. The second part of the expanded air is liquefied and throttled through the high-purity oxygen condenser evaporator and then enters the upper tower 114 of the distillation tower to participate in distillation.

[0036] The third outlet of the second expander 107 is connected to the lower column 115 of the rectifying tower. The remaining expanded air after the expansion of the second expander 107 is sent to the lower column 115 of the rectifying tower.

[0037] The lower refrigerant outlet of the main heat exchanger 105 is connected to the first subcooler 108. The remaining pressurized air in the middle of the main heat exchanger 105 is cooled to liquefaction temperature by the reflux gas and then withdrawn from the lower portion of the main heat exchanger 105. After being subcooled in the first subcooler 108, it is throttled and fed to the upper distillation column 114.

[0038] The present invention further includes: a second subcooler 116 , a third subcooler 117 , a storage tank 118 , an auxiliary heat exchanger 119 and an oxygen pipe network 120 .

[0039] The inlet of second subcooler 116 is connected to the liquid air outlet at the bottom of lower distillation tower 115, and the outlet of second subcooler 116 is connected to upper distillation tower 114. The liquid oxygen outlet at the bottom of upper distillation tower 114 is connected to the inlet of third subcooler 117, which is connected to storage tank 118. The oxygen outlet at the bottom of upper distillation tower 114 is connected to the refrigerant inlet of auxiliary heat exchanger 119, and the refrigerant outlet of auxiliary heat exchanger 119 is connected to oxygen pipeline network 120.

[0040] A certain amount of liquid air is extracted from the bottom of the lower distillation tower 115 and sent to the second subcooler 116 for supercooling. After throttling, it is sent to the upper distillation tower 114. After further distillation in the upper distillation tower 114, liquid oxygen product and oxygen are obtained at the bottom of the upper distillation tower 114. The liquid oxygen is subcooled in the third subcooler 117 and sent to the storage tank 118 as a product. The oxygen is reheated in the auxiliary heat exchanger 119, exits the cold box, and enters the oxygen pipeline network 120 as a product.

[0041] The filtering parts of the air filter 101 and the purifier 104 are redistributed with the cooling parts such as the precooler and the main heat exchanger, and the processes are performed alternately. At the same time, the main heat exchanger is used for heat exchange to provide temperature control conditions for the heat medium output from other processes of the air separation system. The compressed air generated by each process is divided into multiple parts for processing. For example, the main heat exchanger and the second expansion agent are divided into three parts of compressed air for separate processing, thereby reducing the energy consumption of the overall process, improving the processing efficiency and ensuring the initial processing effect.

[0042] Nitrogen is generated at the top of the upper distillation tower 114 and fed into the second air compressor 201 for pressurization, raising the pressure to 1 MPa. The inlet and outlet of the precooler 204 are connected to the pressurization section of the fourth expander 202 and the pressurization section of the fifth expander 203, respectively. The nitrogen pressurized by the second air compressor 201 is boosted to 1.5 MPa by passing through the pressurization section of the fourth expander 202. Before entering the precooler 204, the nitrogen's temperature is approximately -22°C. After cooling in the precooler 204, it drops to approximately -40°C. It then passes through the pressurization section of the fifth expander 203, where it is boosted to 4.5 MPa.

[0043] The boosting section of the fifth expander 203 is connected to the first-stage subcooler 205, which is in turn connected to the expansion section of the fourth expander 202. The inlet and outlet of the second-stage subcooler 206 are connected to the expansion sections of the fourth expander 202 and the fifth expander 203, respectively. The expansion section of the fifth expander 203 is connected to a nitrogen storage tank 207. After being boosted by the boosting section of the fifth expander 203 and raised to 4.5 MPA, the nitrogen is supercooled by the first-stage subcooler 205 and then fed into the expansion section of the fourth expander 202 for expansion, where its temperature drops to approximately -100°C. The nitrogen is then fed into the second-stage subcooler 206, where its temperature drops to approximately -127°C. Finally, the nitrogen is fed into the expansion section of the fifth expander 203 for expansion and cooling, where its temperature drops to -193°C before being fed into the nitrogen storage tank 207.

[0044] By using expanders in series to perform staged pressurization and cooling, the cooling capacity of the gas is greatly increased, thereby achieving the goal of energy saving and consumption reduction, and reducing power loss. The original simple chiller cooling is changed to series pressurization and refrigeration, which greatly reduces power loss and increases liquid nitrogen production.

[0045] The present invention further includes a second condenser evaporator 208 and a subcooler 209. The outlet of the second condenser evaporator 208 is connected to the inlet of the subcooler 209. After air is rectified in the lower column, nitrogen is obtained at the top of the column. The nitrogen output from the top of the lower column 115 of the rectifying column enters the second condenser evaporator 208 and is condensed into liquid nitrogen. The condensed liquid nitrogen is divided into two parts. One part of the liquid nitrogen returns to the lower column as reflux liquid, and the other part is sent to the subcooler 209 for subcooling.

[0046] Subcooler 209 is provided with a first outlet, a second outlet, and a third outlet. The first outlet of subcooler 209 is connected to the inlet of the upper distillation column 114; the second outlet of subcooler 209 is connected to the product liquid nitrogen storage tank 210; and the third outlet of subcooler 209 is connected to the argon system 211. After air is rectified in the lower column, nitrogen is generated at the top of the column. This nitrogen enters the second condenser evaporator 208 and is condensed into liquid nitrogen. A portion of the liquid nitrogen returns to the lower column as reflux, while the remaining liquid nitrogen is sent to subcooler 209 for subcooling. The subcooled liquid nitrogen is then divided into three parts: one part is throttled and sent to the upper column as reflux, one part is withdrawn as product liquid nitrogen, and the remaining part is sent to the argon system 211 to replenish cooling capacity.

[0047] The present invention further includes a liquid nitrogen subcooler 212, a heat exchanger 213, and a purifier 104. Contaminated nitrogen gas extracted from the top of the upper distillation tower 114 is transported to the liquid nitrogen subcooler 212. The outlet of the liquid nitrogen subcooler 212 is connected to the refrigerant inlet of the heat exchanger 213, and the refrigerant outlet of the heat exchanger 213 is connected to the inlet of the water-cooling tower 214. Contaminated nitrogen gas extracted from the upper portion of the upper distillation tower 114 is reheated to room temperature through the liquid nitrogen subcooler 212 and the heat exchanger 213. After being sent out of the cold box, a portion enters the water-cooling tower 214, where it undergoes heat and mass exchange with water discharged from the top of the water-cooling tower 214, cooling the water in the water-cooling tower 214. The remaining portion of the contaminated nitrogen gas enters the purifier 104 as purifier regeneration gas.

[0048] The purifier 104 includes: a heat exchanger 1, a plate heat exchanger 2, a regeneration pipeline, a purifier air compressor 3, a purifier booster 4, an electric heater 5, a first adsorption cylinder 6, a second adsorption cylinder 7, a purifier precooler 8 and a water cooler 9.

[0049] The first adsorption cylinder 6 and the second adsorption cylinder 7 are filled with activated alumina and 13X molecular sieve, which utilize the selective adsorption characteristics of 13X molecular sieve and adsorb harmful components such as water vapor, iron oxide, acetylene, etc. in the air according to the temperature and pressure swing adsorption principle.

[0050] The moist saturated air first flows from bottom to top through the first adsorption cylinder 6. Under pressurized conditions, the moisture, carbon dioxide, acetylene, etc. in the air are adsorbed by the molecular sieve. Since the amount of molecular sieve used is fixed, the adsorption capacity of the molecular sieve will reach saturation within a certain period of time, that is, the adsorption bed is penetrated and the molecular sieve has no further adsorption capacity. At this time, by automatically switching the opening and closing sequence of the valve, the air enters the second adsorption cylinder 7 for continued adsorption. At the same time, the first adsorption cylinder 6, which is saturated with adsorption, begins to regenerate. After the pressure is released to the atmosphere to normal pressure, the heated polluted nitrogen gas from the electric heater 5 is introduced to heat the adsorber bed with a gas flow direction opposite to the adsorption working condition. When the second adsorption cylinder 7 is saturated with adsorption, it is depressurized to the atmosphere when regeneration is required. After the pressure is released, the heated polluted nitrogen gas from the electric heater 5 is introduced.

[0051] During operation, purifier 104 must maintain a low gas temperature to reduce moisture in the air. However, during desorption, the contaminated nitrogen gas must be kept at a high temperature, necessitating the use of electric heater 5 to heat the contaminated nitrogen. However, prolonged operation of electric heater 5 would compromise stability and increase energy consumption. Therefore, the addition of heat exchanger 1 and plate heat exchanger 2 effectively reduces the heater's temperature, preventing it from continuously being heated.

[0052] A contaminated nitrogen gas receiving device is provided at the refrigerant inlet of heat exchanger 1. This device is used to receive contaminated nitrogen gas from heat exchanger 213. Specifically, a flange-to-pipe connection method can be used. The contaminated nitrogen gas delivery pipeline, located at the refrigerant outlet of heat exchanger 213, is flanged to the refrigerant inlet of heat exchanger 1 to receive the contaminated nitrogen gas. The refrigerant outlet of heat exchanger 1 is connected to the refrigerant inlet of plate heat exchanger 2. The heat medium inlet of heat exchanger 2 is connected to the air outlet of purifier air compressor 3, which in turn is connected to water cooler 9. The hot air at the outlet of purifier air compressor 3 exchanges heat with the contaminated nitrogen gas through heat exchanger 1, reducing the temperature of the hot air from purifier air compressor 3 before entering water cooler 9 for further cooling. After heat exchange with heat exchanger 1, the contaminated nitrogen gas is heated and then enters plate heat exchanger 2 for further heat exchange and heating.

[0053] The refrigerant outlet of plate heat exchanger 2 is connected to the air inlet of electric heater 5, the heat medium inlet of plate heat exchanger 2 is connected to the air outlet of purifier booster 4, and the heat medium outlet of plate heat exchanger 2 is connected to purifier pre-cooler 8. After heat exchange in heat exchanger 1, the contaminated nitrogen gas is heated and then enters plate heat exchanger 2 for another heat exchange with the outlet gas of purifier booster 4. After the temperature is further increased, it enters electric heater 5. The hot gas from purifier booster 4 exchanges heat with the contaminated nitrogen gas and cools it down before entering purifier pre-cooler 8 for a cooling cycle. This does not change the original process flow. Technical improvements based on the existing equipment require only minor modifications and process optimization to achieve the goal of increasing production and reducing consumption, effectively controlling the cost of the renovation.

[0054] The hot air from the outlet of the purifier air compressor 3 and the purifier booster 4 undergoes a stepwise heat exchange with the contaminated nitrogen, raising the temperature of the contaminated nitrogen. This, in turn, raises the temperature of the gas entering the electric heater 5, reducing the life of the electric heater 5. Simultaneously, this controls the amount of impurities entering the purifier, extending the service life of the molecular sieve and alumina, reducing the hydrocarbon content in the product gas, and minimizing production safety hazards.

[0055] The air outlet of the electric heater 5 is connected to the regeneration pipeline, and the regeneration air inlets of the first adsorption cylinder 6 and the second adsorption cylinder 7 are connected to the electric heater 5 through the regeneration pipeline. The regeneration pipeline includes: an output pipeline 301, a first input pipeline 302 and a second input pipeline 303.

[0056] One end of the output pipeline 301 is connected to the air outlet of the electric heater 5, and the other end is connected to the first input pipeline 302 and the second input pipeline 303 respectively. The first input pipeline 302 is connected to the air inlet of the first adsorption cylinder 6, and the second input pipeline 303 is connected to the air inlet of the second adsorption cylinder 7.

[0057] When the first adsorption tube 6 is saturated, the contaminated nitrogen gas heated by the electric heater 5 heats the bed of the first adsorption tube 6 in a gas flow direction opposite to that of the adsorption process. The adsorbent previously adsorbed within the molecular sieve particles is desorbed due to the increased temperature. Driven by the hot gas flow, the desorbed water vapor, carbon dioxide, acetylene, and other substances are driven out of the adsorption bed. Because the adsorbent bed temperature is very high at this point and unsuitable for the next adsorption cycle, unheated air or contaminated nitrogen gas must be introduced to cool the adsorption bed after the heating period is complete, lowering the adsorption bed temperature to a level close to that during adsorption. At this point, the adsorber's regeneration process is complete, and it is ready for the next adsorption cycle. When the second adsorption tube 7 is saturated, the contaminated nitrogen gas heated by the electric heater 5 enters the second adsorption tube 7 for desorption. The two adsorbers thus alternate between adsorption and regeneration, achieving continuous air purification.

[0058] The electric heater 5 accounts for a significant portion of the low-voltage electricity consumption in the entire air separation plant. The outlet temperature of the contaminated nitrogen directly affects the molecular sieve's desorption performance. The molecular sieve's cooling peak temperature is a key parameter for measuring desorption effectiveness and is preferably controlled at around 160°C. Typically, the contaminated nitrogen flow rate is pre-set to a fixed value throughout the molecular sieve desorption process, leaving the flow rate essentially unchanged. However, the first half of the cooling phase of the molecular sieve can be considered a continuation of the heating process. Therefore, appropriately controlling the contaminated nitrogen flow rate during the heating and cooling phases can achieve better results, increasing the cooling peak temperature while saving energy.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An air separation system, characterized in that: include: Air filter, first air compressor, precooler, purifier, main heat exchanger, first expander, second expander, first subcooler, second air compressor, fourth expander, fifth expander, precooler, first subcooler, second subcooler and nitrogen storage tank; The air passes through the air filter to remove impurities and then enters the first air compressor. After being compressed and cooled by the first air compressor, the air enters the precooler. After being cooled and dehydrated, the air enters the purifier. The air from which moisture and carbon dioxide have been removed by the purifier is transported to the first air compressor. A portion of the compressed air after being compressed and cooled enters the main heat exchanger. The upper refrigerant outlet of the main heat exchanger is connected to the first expander, the middle refrigerant outlet of the main heat exchanger is connected to the second expander, and the lower refrigerant outlet of the main heat exchanger is connected to the first subcooler; The nitrogen output from the top of the upper tower of the distillation tower enters the second air compressor for pressurization. The inlet and outlet of the precooler are respectively connected to the pressurization section of the fourth expander and the pressurization section of the fifth expander. The pressurization section of the fifth expander is connected to the first-stage subcooler. The first-stage subcooler is connected to the expansion section of the fourth expander. The inlet and outlet of the second-stage subcooler are respectively connected to the expansion section of the fourth expander and the expansion section of the fifth expander. The expansion section of the fifth expander is connected to the nitrogen storage tank. Also includes: a circulating compressor; the outlet of the first expander is connected to the middle refrigerant inlet of the main heat exchanger, the inlet of the circulating compressor is connected to the middle refrigerant outlet of the main heat exchanger, and the outlet of the circulating compressor is connected to the upper refrigerant inlet of the main heat exchanger; The second expander is provided with a first outlet, a second outlet and a third outlet; The first outlet of the second expander is connected to the circulation compressor; The second outlet of the second expander is connected to the first condenser evaporator, and the first condenser evaporator is connected to the upper tower of the distillation tower; The third outlet of the second expander is connected to the lower tower of the distillation tower.

2. An air separation system according to claim 1, characterized in that: Also includes: The other part of the compressed air after being compressed and cooled by the first air compressor enters the booster and the third expander in sequence, and the compressed air after being boosted twice is transported to the distillation tower cold box.

3. An air separation system according to claim 2, characterized in that: A backflow air input port is provided on the first air compressor, and the output port of the purifier and the output port of the fractionation tower cold box are both connected to the backflow air input port of the first air compressor.

4. An air separation system according to claim 3, characterized in that: Also includes: a second subcooler, a third subcooler and a storage tank; the inlet of the second subcooler is connected to the liquid air outlet at the bottom of the lower tower of the distillation tower, and the outlet of the second subcooler is connected to the upper tower of the distillation tower; the liquid oxygen outlet at the bottom of the upper tower of the distillation tower is connected to the inlet of the third subcooler, and the outlet of the third subcooler is connected to the storage tank.

5. An air separation system according to claim 4, characterized in that: Also includes: Auxiliary heat exchanger and oxygen pipe network; the bottom oxygen outlet of the upper tower of the distillation tower is connected to the refrigerant inlet of the auxiliary heat exchanger, and the refrigerant outlet of the auxiliary heat exchanger is connected to the oxygen pipe network.

6. An air separation system according to claim 5, characterized in that: Also includes: A second condenser evaporator and a subcooler; the nitrogen output from the top of the lower tower of the distillation tower enters the second condenser evaporator to condense into liquid nitrogen, and the condensed liquid nitrogen is transported to the subcooler for subcooling.

7. An air separation system according to claim 6, characterized in that: The subcooler is provided with a first outlet, a second outlet and a third outlet; The first outlet of the subcooler is connected to the inlet of the upper tower of the distillation tower; The second outlet of the subcooler is connected to the product liquid nitrogen storage tank; The third outlet of the subcooler is connected to an argon system.

8. An air separation system according to claim 7, characterized in that: Also includes: Liquid nitrogen subcooler and heat exchange equipment; the dirty nitrogen gas extracted from the top of the distillation tower is transported to the liquid nitrogen subcooler, the outlet of the liquid nitrogen subcooler is connected to the refrigerant inlet of the heat exchange equipment, and the refrigerant outlet of the heat exchange equipment is connected to the inlet of the water cooling tower.

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