A double-tower externally-hung rectification nitrogen production equipment

Abstract

The application discloses a double-tower externally-hung rectification nitrogen production equipment, which comprises an air pretreatment system, an air inlet end is communicated with air, and is used for filtering, cooling and purifying the air to form raw material air; the raw material air is introduced into the bottom of a lower tower after heat exchange of a main heat exchanger; the main heat exchanger is used for heat exchange to reduce the temperature of the raw material air; the lower tower is used for separating the raw material air to form nitrogen gas at the top of the lower tower; a condenser evaporator group is used for circulating heat exchange to form liquid nitrogen through the heat siphon principle; an auxiliary tower is used for rectifying gas to obtain nitrogen gas products at the top of the auxiliary tower; and a nitrogen gas product pipe is used for discharging the nitrogen gas products at the top of the auxiliary tower. In the application, the oxygen-rich liquid air at the bottom of the lower tower and the auxiliary tower is used as a cold source, and high-pressure nitrogen gas at the top of the lower tower is used as a heat source, more nitrogen gas can be liquefied under the same oxygen-rich liquid air volume, the liquid nitrogen return flow is increased, and the nitrogen gas extraction rate is improved.

Description

Technical Field

[0001] This invention relates to the field of nitrogen production technology, specifically to a dual-tower external distillation nitrogen production device. Background Technology

[0002] Nitrogen is an elemental form of nitrogen, with the chemical formula N2. It is a colorless and odorless gas at room temperature and pressure, making up more than 78% of the Earth's atmosphere and is the most abundant component of the atmosphere.

[0003] With the development of technology, high-tech fields such as AI, robotics, and aviation have gradually become the mainstream of research. Nitrogen, due to its stable chemical inertness, plays an important role in the electronics and aerospace fields. As a protective gas and process carrier gas, nitrogen is used in many fields. For example, in wafer fabrication, high-purity nitrogen can replace oxygen and moisture in the reaction chamber, preventing precision components such as silicon wafers and metal circuits from oxidizing or being contaminated by impurities during high-temperature processes, thus ensuring the electrical performance and yield of chips. In CVD, nitrogen is used as a carrier gas to transport precursor gases. After ion implantation, nitrogen is used to remove residual ions. In photolithography and etching, nitrogen purging can quickly remove photoresist residues or reaction byproducts, ensuring the cleanliness of the wafer surface.

[0004] In the existing technology, the dual-tower dual-condenser nitrogen generator consists of a main and auxiliary tower, a main and auxiliary condenser, a main heat exchanger, a subcooler, an expander, and a liquid nitrogen pump. Product nitrogen is obtained at the top of the lower tower, and after being reheated by the main heat exchanger, it is sent out of the cold box. The nitrogen extraction rate of this process is about 70%, and some nitrogen needs to be pumped into the upper tower. After being liquefied in the upper tower to form liquid nitrogen, a portion of the liquid nitrogen in the upper tower is pumped into the top of the lower tower as reflux liquid.

[0005] To ensure the purity of nitrogen in the lower column, nitrogen liquefaction and reflux are required. However, the internal pressure and temperature of the lower column are higher than those in the upper column, making it impossible to form a reflux liquid. Therefore, a portion of the nitrogen at the top of the lower column needs to exchange heat with the cold source in the upper column. The lower-boiling-point "cold source" in the upper column absorbs heat, forcing the gaseous nitrogen at the top of the lower column to condense into liquid for reflux. While this process solves the reflux problem in the lower column, it also means that the amount of nitrogen condensed in the lower column must maintain a thermal balance with the evaporation rate of the cold source in the upper column. In other words, a portion of the liquid nitrogen in the lower column must be extracted to maintain the circulation and evaporation in the upper column. This portion of nitrogen used for heat exchange in the upper column cannot be collected as the final product, directly leading to a decrease in the nitrogen extraction rate.

[0006] Therefore, there is an urgent need for nitrogen generation equipment that can improve nitrogen extraction rate. Summary of the Invention

[0007] The purpose of this invention is to propose a dual-tower external distillation nitrogen generation device to solve the problem of low nitrogen extraction rate in existing nitrogen generation devices in the background art.

[0008] To achieve the above objectives, this invention proposes a dual-tower external distillation nitrogen production device, comprising an air pretreatment system, a main heat exchanger, a lower tower, a condenser-evaporator assembly, an auxiliary tower, and a nitrogen product pipe. The air pretreatment system has an inlet connected to air for cooling, filtering, and purifying the air to form feed air. An inlet pipe at the outlet allows the feed air to pass through the main heat exchanger and then be introduced into the bottom of the lower tower. The main heat exchanger is connected to the air pretreatment system, the lower tower, and the auxiliary tower for heat exchange. The process involves several steps: First, the raw material air temperature is lowered. Second, a lower column separates the raw material air, forming nitrogen at its top. Third, a condenser-evaporator unit connects to the lower and auxiliary columns, using the oxygen-rich liquid air at the bottom of both columns as a liquid cold source and the nitrogen at the top of the lower column as a heat source. This heat exchange is achieved through thermosiphoning to form liquid nitrogen, which serves as the reflux liquid for the lower and auxiliary columns. Fourth, an auxiliary column is used for gas distillation, yielding nitrogen product at its top. Fifth, a nitrogen product pipe connects to the top of the auxiliary column, discharging the nitrogen product from the top of the auxiliary column.

[0009] Optionally, the dual-tower external distillation nitrogen production equipment also includes an expander and a cold box; the inlet of the expander is connected to the outlet of the condenser-evaporator group, and the outlet is equipped with a waste nitrogen return pipe, which is connected to the air pretreatment system through the main heat exchanger; the lower tower, the condenser-evaporator group and the auxiliary tower are located in the cold box.

[0010] Optionally, the condenser-evaporator assembly includes a first condenser-evaporator and a second condenser-evaporator connected to the top of the lower column, a first liquid-air separator connected to the first condenser-evaporator, and a second liquid-air separator connected to the second condenser-evaporator; the first liquid-air separator is connected to the lower column; and the second liquid-air separator is connected to the auxiliary column.

[0011] Optionally, the inlet ends of the first and second condenser-evaporators are connected to the top of the lower column; the liquid outlet ends of the first and second condenser-evaporators are connected to each other, so that the liquid nitrogen is mixed. Part of the mixed liquid nitrogen flows into the top of the lower column, and the other part of the liquid nitrogen enters the top of the auxiliary column through the main heat exchanger.

[0012] Optionally, the inlet end of the first liquid-air separator is connected to the outlet end of the first condenser-evaporator; the inlet end of the second liquid-air separator is connected to the outlet end of the second condenser-evaporator.

[0013] Optionally, the outlet of the first liquid-air separator is connected to the bottom of the auxiliary tower; the gas discharged from the outlet of the second liquid-air separator enters the expander after passing through the main heat exchanger.

[0014] Optionally, the first liquid-air separator is provided with a first cold source pipe at the liquid inlet end, and the other end of the first cold source pipe is connected to the bottom of the lower tower; the second liquid-air separator is provided with a second cold source pipe at the liquid inlet end, and the other end of the second cold source pipe is connected to the bottom of the auxiliary tower.

[0015] Optionally, the first liquid-air separator has two liquid outlets; the liquid outlet of the second liquid-air separator is connected to the liquid inlet of the second condenser-evaporator; the two liquid outlets of the first liquid-air separator are respectively connected to the liquid inlet of the first condenser-evaporator and the second cold source pipe; the first cold source pipe is connected to a supplementary cold source pipe.

[0016] Optionally, the pressure inside the first liquid-air separator is lower than the pressure of the oxygen-enriched liquid air inside the lower column.

[0017] Optionally, the pressure inside the second liquid-air separator is lower than the pressure of the oxygen-enriched liquid air inside the auxiliary tower.

[0018] Optionally, the pressure of the first condenser-evaporator and the pressure of the second condenser-evaporator are both equal to the pressure at the top of the lower column.

[0019] Optionally, the minimum straight-line distance between the second liquid-air separator and the ground is greater than the maximum straight-line distance between the effective heat exchange section of the second condenser-evaporator and the ground.

[0020] Optionally, the minimum straight-line distance between the first liquid-air separator and the ground is greater than the maximum straight-line distance between the effective heat exchange section of the first condenser-evaporator and the ground.

[0021] Optionally, the cold source in the second liquid-air separator flows into the second condenser-evaporator to exchange heat with nitrogen. At least part of the cold source becomes gas after heat exchange and returns to the second liquid-air separator. The nitrogen entering the second condenser-evaporator becomes liquid nitrogen after heat exchange and is discharged from the second condenser-evaporator.

[0022] Optionally, the cold source in the first liquid-air separator flows into the first condenser-evaporator to exchange heat with nitrogen. At least part of the cold source becomes gas after heat exchange and returns to the first liquid-air separator. The nitrogen entering the first condenser-evaporator becomes liquid nitrogen after heat exchange and is discharged from the first condenser-evaporator.

[0023] Optionally, the connection point between the outlet of the condenser-evaporator and the liquid-air separator is higher than the liquid level inside the liquid-air separator.

[0024] Optionally, the cold source in the liquid-air separator flows into the condenser-evaporator by gravity to exchange heat with nitrogen. At least part of the cold source turns into gas after heat exchange and returns to the liquid-air separator. The nitrogen entering the condenser-evaporator turns into liquid nitrogen after heat exchange and is discharged from the condenser-evaporator.

[0025] Optionally, the air pretreatment system includes an air compressor, an air filter connected to the air compressor inlet, a precooling device connected to the air compressor outlet, and an adsorber connected to the precooling device outlet.

[0026] Optionally, the inlet pipe is connected to the outlet of the adsorber, and the inlet pipe is connected to the bottom of the lower column via the main heat exchanger.

[0027] Optionally, the waste nitrogen return pipe is connected to the output end of the adsorber.

[0028] Optionally, the adsorber has an adsorption state and a regeneration state; there are two adsorbers, and the two adsorbers alternately operate in the adsorption state to adsorb and purify the air discharged from the outlet of the precooling equipment.

[0029] Optionally, a heater is provided on the waste nitrogen return pipe to heat the waste nitrogen in the waste nitrogen return pipe, and the heated waste nitrogen backflushes the adsorber in the regeneration state.

[0030] Optionally, the waste nitrogen return pipe is provided with a return branch pipe connected to the adsorption outlet pipe.

[0031] Optionally, the air inlet end of the adsorber is provided with an adsorption air inlet pipe, and an air inlet connecting pipe that connects the two adsorption air inlet pipes is connected at both ends to the air inlet connecting pipe and the air inlet main pipe at the air outlet end of the precooling equipment, respectively.

[0032] Optionally, the air outlet end of the adsorber is provided with an adsorption air outlet pipe and an air outlet connecting pipe that connects the two adsorption air outlet pipes. The air outlet connecting pipe is connected to the air inlet pipe.

[0033] Optionally, a pressure equalization tube connects the two adsorption outlet tubes.

[0034] Optionally, both adsorption inlet pipes are equipped with reflux discharge pipes, and the two reflux discharge pipes converge into a reflux convergence pipe.

[0035] Compared with the prior art, the present invention provides a dual-tower external distillation nitrogen production device, which has the following beneficial effects: This dual-tower external distillation nitrogen generator uses oxygen-enriched liquid air at the bottom of the lower and auxiliary towers as a cold source, and high-pressure nitrogen at the top of the lower tower as a heat source. Because the liquid oxygen in the upper tower is low and the evaporation temperature is relatively low, the high-pressure nitrogen condensation releases heat and the low-pressure oxygen-enriched liquid air absorbs heat for evaporation. Under the same volume of oxygen-enriched liquid air, more nitrogen can be liquefied, increasing the liquid nitrogen reflux flow rate and thus improving the nitrogen extraction rate.

[0036] In addition, oxygen-enriched liquid air is exchanged with nitrogen gas through the thermosiphon principle. Utilizing gravity and gas pressure, the oxygen-enriched liquid air exchanges heat with the heat source nitrogen gas under the gravitational action of the height difference. The oxygen-enriched liquid air is heated and vaporized, returning to the storage cavity to stabilize the pressure inside the liquid-air separator, preventing flash evaporation of the cold source inside the liquid-air separator, and ensuring that the liquid-air separator and the condenser-evaporator form a self-circulating heat exchange system. No external power is required, reducing equipment energy consumption. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0038] The diagram shows the following labels: 100, Air pretreatment system; 110, Air compressor; 120, Air filter; 130, Precooling equipment; 140, Adsorber; 141, Adsorber inlet pipe; 142, Inlet connecting pipe; 143, Main inlet pipe; 144, Adsorber outlet pipe; 145, Outlet connecting pipe; 146, Pressure equalization pipe; 147, Return discharge pipe; 148, Return converging pipe; 150, Inlet pipe; 200, Main heat exchanger; 300. 1. Lower tower; 400. Condenser-evaporator group; 410. First condenser-evaporator; 420. Second condenser-evaporator; 430. First liquid-air separator; 431. First cold source pipe; 432. Supplementary cold source pipe; 440. Second liquid-air separator; 441. Second cold source pipe; 500. Auxiliary tower; 600. Nitrogen product pipe; 700. Expander; 710. Nitrogen reflux pipe; 711. Heater; 712. Reflux branch pipe; 800. Cold box. Detailed Implementation

[0039] The invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0040] The dual-tower external distillation nitrogen generator of this application can be applied to nitrogen production in the air separation field, and can also be used in other similar applications. The following is a detailed description of the dual-tower external distillation nitrogen generator.

[0041] See appendix Figure 1The diagram shown is a structural schematic of a preferred embodiment of a dual-tower external distillation nitrogen production device according to this application. This dual-tower external distillation nitrogen production equipment includes an air pretreatment system 100 with its inlet connected to the atmosphere to form the feed air; a main heat exchanger 200 for cooling the feed air; a lower tower 300 for separating the feed air to obtain nitrogen; a condenser-evaporator assembly 400 connected to the lower tower 300 and auxiliary tower 500 for exchanging heat with the nitrogen to form liquid nitrogen and providing reflux liquid to the lower tower 300 and auxiliary tower 500; an auxiliary tower 500 for distilling the gas to obtain nitrogen product; a nitrogen product pipe 600 connected to the top of the auxiliary tower 500 for discharging the nitrogen product; an expander for generating cooling capacity and connected to the main heat exchanger 200; and a cold box 800 for providing cooling space. The main heat exchanger 200, lower tower 300, condenser-evaporator assembly 400, and auxiliary tower 500 are all located within the cold box 800.

[0042] This application utilizes an air pretreatment system 100 to filter, cool, and purify air, obtaining raw material air for air separation. The air pretreatment system 100 has an inlet pipe 150 at its outlet, which guides the raw material air into the main heat exchanger 200 for cooling. The cooled raw material air is then input to the bottom of the lower tower 300 as an upward airflow within the lower tower 300. The main heat exchanger 200 provides heat exchange space, allowing the raw material air temperature to drop to its liquefaction temperature. The lower tower 300 separates the raw material air entering through the inlet pipe 150, obtaining nitrogen at the top and oxygen-rich liquid air at the bottom. A condenser-evaporator group 400 exchanges heat between the nitrogen at the top of the lower tower 300 and a cold source, liquefying the nitrogen to form liquid nitrogen, providing sufficient reflux liquid for the lower tower 300 and the auxiliary tower 500. The auxiliary tower 500 is used to further process the nitrogen. The gas inside the auxiliary tower 500 undergoes distillation, yielding nitrogen product at the top and oxygen-enriched liquid air at the bottom. The nitrogen product pipe 600 is connected to the top of the auxiliary tower 500 to collect the nitrogen at the top. The cold box 800 in this application is a vacuum cold box. By replacing the traditional thick insulation layer with a vacuum jacket, the insulation performance of the cold box is improved, the system cold loss is reduced, and the risk of frost formation on the outer wall is effectively avoided. Furthermore, the reduction in the thickness of the insulation layer makes the device structure more compact and significantly improves the space utilization rate. In addition, the significant reduction in ambient heat loss reduces the amount of cooling required to maintain the operating conditions. The cooling compensation mechanism is thus changed from "expander mechanical work to generate cooling" to "liquid nitrogen back injection phase change heat absorption to supplement cooling," thereby eliminating the rigid dependence on the expander. This not only enriches the adjustment methods but also completely eliminates the hidden danger of unplanned shutdowns caused by expander failure or maintenance, ultimately ensuring the long-term continuous and stable production of the device. The cold box 800 in this application is an existing cold box, which has been disclosed in patent number 201710457584.9, entitled "A Novel Vacuum Cold Box" and application number CN201310047845.1, entitled "An Air Separation Cold Box". Therefore, it will not be described in detail here.

[0043] See appendix Figure 1 As shown, in this application, the air pretreatment system 100 includes an air compressor 110, an air filter 120 connected to the air inlet of the air compressor 110, a precooling device 130 connected to the air outlet of the air compressor 110, and an adsorber 140 connected to the air outlet of the precooling device 130; wherein, the air inlet pipe 150 is connected to the air outlet of the adsorber 140, and the air inlet pipe 150 is connected to the bottom end of the lower tower 300 through the main heat exchanger 200.

[0044] This application utilizes an air compressor 110 to provide the power for airflow, drawing in external air and directing it into the air pretreatment system 100; an air filter 120 to filter the air entering the air pretreatment system 100, removing particulate impurities; a precooling device 130 to precool the air, lowering its temperature and reducing the heat exchange pressure of the subsequent main heat exchanger 200; and an adsorber 140 to adsorb and purify moisture, carbon dioxide, and hydrocarbons in the air, reducing the working pressure and difficulty of nitrogen separation in the subsequent lower tower 300 and auxiliary tower 500.

[0045] See appendix Figure 1 As shown in this application, the adsorber 140 has an adsorption state and a regeneration state; there are two adsorbers 140, and the two adsorbers 140 alternately adsorb and purify the air discharged from the outlet of the precooling device 130.

[0046] This application sets up two adsorbers 140, with each adsorber 140 in an adsorption state and a regeneration state respectively. This ensures continuous adsorption and purification of air, continuous air flow, and a stable adsorption effect while providing sufficient air to the lower tower 300. When the adsorption time of one adsorber 140 reaches a specified time and the adsorption effect begins to weaken, the other adsorber 140 can start working to adsorb, and the adsorber 140 can be backwashed and regenerated.

[0047] See appendix Figure 1 As shown in this application, the air inlet end of the adsorber 140 is provided with an adsorption air inlet pipe 141, and an air inlet connecting pipe 142 connecting the two adsorption air inlet pipes 141, with both ends connected to the air inlet connecting pipe 142 and the air inlet main pipe 143 at the air outlet end of the precooling equipment 130, respectively; wherein, the air outlet end of the adsorber 140 is provided with an adsorption air outlet pipe 144, and an air outlet connecting pipe 145 connecting the two adsorption air outlet pipes 144, the air outlet connecting pipe 145 being connected to the air inlet pipe 150; a pressure equalization pipe 146 for two oil barrels is provided between the two adsorption air outlet pipes 144; a return discharge pipe 147 is provided on each of the two adsorption air inlet pipes 141, and the two return discharge pipes 147 converge in the return convergence pipe 148.

[0048] This application, through the arrangement of adsorption inlet pipes 141 and the corresponding number of adsorbers 140, allows two adsorbers 140 to alternately intake air. Each of the two adsorption inlet pipes 141 is equipped with a control valve to control the connection and closure of the corresponding adsorption inlet pipe 141. An inlet connecting pipe 142 connects the ends of the two adsorption inlet pipes 141, allowing air after passing through the pre-cooling device 130 to enter either adsorber 140, ensuring that both adsorbers 140 can adsorb and purify the air. An inlet main pipe 143 guides the air after passing through the pre-cooling device 130 into the inlet connecting pipe 142. The adsorption outlet pipe 144 is used to discharge the adsorbed air. Together with the outlet connecting pipe 145, it ensures that the raw material air discharged after adsorption by either adsorber 140 is collected and uniformly transported to the lower tower 300 at the back end, saving pipeline materials and reducing equipment costs. The pressure equalization pipe 146 connects the two adsorption outlet pipes 144, balancing the gas pressure of the two adsorbers 140 before the state transition, avoiding the strong airflow impact caused by the instantaneous rush of high-pressure gas into the low-pressure adsorber, eliminating the violent fluctuations in flow and pressure at the moment of switching, ensuring stable operation of the device, preventing damage to the internal structure of the adsorber 140 due to impact, and thus extending the service life of the equipment.

[0049] See appendix Figure 1 As shown in this application, the main heat exchanger 200 is used to provide heat exchange conditions to cool down the raw material air in the inlet pipe 150 to form a gas-liquid mixture; the main heat exchanger 200 is also connected to the expander 700, and the expansion end of the expander 700 is connected to the main heat exchanger 200 to provide a heat exchange cold source.

[0050] See appendix Figure 1 As shown in this application, the lower tower 300 is used to separate the gas-liquid mixture that enters through the inlet pipe 150. The gas in the gas-liquid mixture that enters from the bottom of the lower tower 300, as well as the gas formed by the evaporation of the liquid, moves to the top of the lower tower 300. At the same time, the liquid nitrogen reflux liquid at the top of the lower tower 300 exchanges heat with this part of the gas, and the gas other than nitrogen is liquefied, so that nitrogen is generated at the top of the inner cavity of the lower tower 300 and oxygen-rich liquid air is formed at the bottom of the lower tower 300.

[0051] See appendix Figure 1 As shown in the present application, the condenser-evaporator group 400 includes a first condenser-evaporator 410 and a second condenser-evaporator 420 connected to the top of the lower tower 300, a first liquid-air separator 430 connected to the first condenser-evaporator 410 via a pipe, and a second liquid-air separator 440 connected to the second condenser-evaporator 420 via a pipe; wherein, the first liquid-air separator 430 is connected to the bottom of the lower tower 300; and the second liquid-air separator 440 is connected to the auxiliary tower 500.

[0052] This application utilizes a first condenser-evaporator 410 and a second condenser-evaporator 420 to exchange heat between the oxygen-enriched liquid air at the bottom of the lower tower 300 and the bottom of the auxiliary tower 500 and the nitrogen gas at the top of the lower tower 300. The nitrogen gas is liquefied to form liquid nitrogen, which serves as the reflux liquid for the lower tower 300 and the auxiliary tower 500, exchanging heat with the rising gas within these towers. Furthermore, by connecting a first liquid-air separator 430 to the bottom of the lower tower 300, the oxygen-enriched liquid air at the bottom of the lower tower 300 can enter the first liquid-air separator 430 and flow into the first condenser-evaporator 410 for heat exchange. Similarly, by connecting a second liquid-air separator 440 to the bottom of the auxiliary tower 500, the nutrient-enriched liquid air at the bottom of the auxiliary tower 500 can enter the second liquid-air separator 440 and flow into the second condenser-evaporator 420 for heat exchange. It should be noted that the first condenser-evaporator 410, the second condenser-evaporator 420, the first liquid-air separator 430 and the second liquid-air separator 440 are all mounted on the inner wall of the cold box 800 or the outer wall of the lower tower 300 by bolts and other connecting parts, which reduces the height of the entire equipment, reduces the space occupied by the equipment, and lowers the manufacturing cost.

[0053] See appendix Figure 1 As shown in this application, the gas inlet ends of the first condenser-evaporator 410 and the second condenser-evaporator 420 are both connected to the top of the lower column 300, ensuring that the nitrogen separated at the top of the lower column 300 can enter the first condenser-evaporator 410 and the second condenser-evaporator 420 through pipelines; the liquid outlet end of the first condenser-evaporator 410 is connected to the liquid outlet end of the second condenser-evaporator 420, mixing the liquid nitrogen at the liquid outlet ends of the first condenser-evaporator 410 and the second condenser-evaporator 420, which facilitates unified distribution and processing. It is also convenient to transport part of the liquid nitrogen to the top of the lower column 300 as reflux liquid to distill the rising gas in the lower column 300, and to transport the remaining liquid nitrogen to the auxiliary column 500 as reflux liquid after being subcooled by the main heat exchanger 200 to distill the rising gas in the auxiliary column 500.

[0054] See appendix Figure 1As shown in this application, the inlet of the first liquid-air separator 430 is connected to the outlet of the first condenser-evaporator 410, and the inlet of the second liquid-air separator 440 is connected to the inlet of the second condenser-evaporator 420. This allows the oxygen-rich liquid air cold source in the condenser-evaporator to exchange heat with the nitrogen heat source. The gas formed by the vaporization of the oxygen-rich liquid air flows back to the liquid-air separator connected to the condenser-evaporator, stabilizing the pressure inside the liquid-air separator. The outlet of the first liquid-air separator 430 is connected to the bottom of the auxiliary tower 500, allowing the gas from the vaporization of the oxygen-rich liquid air in the first liquid-air separator 430 after heat exchange to enter the auxiliary tower 500. The nitrogen product is further refined in column 500 to obtain a higher purity nitrogen product, thereby improving the nitrogen extraction rate. The gas discharged from the outlet of the second liquid-air separator 440 enters the expander 700 after passing through the main heat exchanger 200. Since the oxygen-enriched liquid air in the second liquid-air separator 440 has a low nitrogen content, it is vaporized after heat exchange and then transported to the expander 700 for expansion and cooling, providing a heat source for the main heat exchanger 200. The inlet of the first liquid-air separator 430 is equipped with a first cold source pipe 431 connected to the bottom of the lower column 300, ensuring that the oxygen-enriched liquid air at the bottom of the lower column 300 can be cooled. The oxygen-enriched liquid air flows into the first liquid-air separator 430 through the first cold source pipe 431; the inlet end of the second liquid-air separator 440 is provided with a second cold source pipe 441 connected to the bottom of the auxiliary tower 500, ensuring that the oxygen-enriched liquid air at the bottom of the auxiliary tower 500 can enter the second liquid-air separator 440; it should be noted that the first liquid-air separator 430 has two outlet ends, which are respectively connected to the first condenser-evaporator 410 and the second cold source pipe 441, so that the oxygen-enriched liquid air in the first liquid-air separator 430 can flow into the first condenser-evaporator 410 as a cold source, and the excess oxygen-enriched liquid air in the first liquid-air separator 430 can be... The system replenishes the second condenser-evaporator 420 to ensure its normal heat exchange. The outlet of the second liquid-air separator 440 is connected to the second condenser-evaporator 420, allowing the oxygen-rich liquid air in the second liquid-air separator 440 to flow into the second condenser-evaporator 420. The first cold source pipe 431 is connected to a supplementary cold source pipe 432, which is connected to an external liquid nitrogen storage tank. This supplementary cold source pipe 432 is used to draw liquid nitrogen from the liquid nitrogen storage tank into the first liquid-air separator 430 during equipment startup as an initial or supplementary cold source. The storage tank pipeline can be shut off after the equipment is running normally.

[0055] See appendix Figure 1 As shown, in this application, the pressure inside the first liquid-air separator 430 is lower than the pressure of the oxygen-enriched liquid air inside the lower tower 300, the pressure inside the second liquid-air separator 440 is lower than the pressure of the oxygen-enriched liquid air inside the auxiliary tower 500, and the pressures of the first condenser-evaporator 410 and the second condenser-evaporator 420 are both equal to the pressure at the top of the lower tower 300.

[0056] By setting the pressure inside the first liquid-air separator 430 to be lower than the oxygen-enriched liquid-air pressure at the bottom of the lower tower 300, an effective pressure difference is created between the two to drive the fluid flow. This pressure difference is ensured to be large enough to overcome the gravitational resistance generated by the oxygen-enriched liquid-air in the flow path. As a result, the oxygen-enriched liquid-air at the bottom of the lower tower 300 can overcome gravity under the continuous drive of this pressure difference, flow upward in a direction away from the ground, and smoothly enter the first liquid-air separator 430. Similarly, by setting the pressure inside the second liquid-air separator 440 to be lower than the oxygen-enriched liquid-air pressure in the auxiliary tower 500, an effective pressure difference is created between the two to drive the fluid flow, allowing the oxygen-enriched liquid-air in the oxygen-enriched tower 500 to enter the second liquid-air separator 500.

[0057] See appendix Figure 1 As shown in this application, the minimum straight-line distance between the liquid surface in the liquid-air separator and the ground is greater than the maximum straight-line distance perpendicular to the ground of the effective heat exchange section of the condenser-evaporator connected to the liquid-air separator. The minimum distance between the liquid surface and the ground is A, which is the minimum straight-line distance from the liquid surface to the reference point, with the nitrogen generator and the horizontal ground as the reference. The effective heat exchange section is the heat exchange part between the oxygen-rich liquid air and the nitrogen heat source. The maximum vertical distance from a point on the effective heat exchange section to the reference surface must be less than A, thereby ensuring that the cold source in the liquid-air separator can flow into the condenser-evaporator by gravity generated by the liquid level difference.

[0058] See appendix Figure 1 As shown in this application, the connection position of the liquid-air separator connected to the outlet of the condenser-evaporator is higher than the liquid level in the liquid-air separator. This ensures that the cold source in the liquid-air separator can be vaporized into gas after exchanging heat with the nitrogen heat source in the condenser-evaporator and can flow back into the liquid-air separator smoothly. It also prevents the cold source in the liquid-air separator from flowing back into the condenser-evaporator.

[0059] See appendix Figure 1 As shown in this application, the inlet end of the expander 700 is connected to the outlet end of the second condenser evaporator 420. The outlet end of the expander 700 is provided with a waste nitrogen return pipe 710. The waste nitrogen return pipe 710 exchanges heat through the main heat exchanger 200, and a heater 711 is installed on the part of the waste nitrogen return pipe 710 after passing through the main heat exchanger 200 to heat the waste nitrogen in the waste nitrogen return pipe 710. The end of the waste nitrogen return pipe 710 is provided with a return branch pipe 712 connected to the adsorption outlet pipe 144.

[0060] This application utilizes a nitrogen return pipe 710 to use nitrogen as a backflushing gas to backflush the adsorber 140; a heater 711 is used to heat the nitrogen in the nitrogen return pipe 710, increasing its temperature and providing a large amount of heat energy to the adsorbent in the adsorber 140, weakening the binding force between impurity molecules and the adsorbent, forcing them to detach from the micropores of the adsorbent, thus completing the regeneration of the adsorbent; and a return branch pipe 712 is used to guide the heated nitrogen into the adsorber 140 where the adsorbent needs to be regenerated.

[0061] See appendix Figure 1 As shown, the nitrogen production process of this application is as follows: The air pretreatment system 100 begins pretreatment of the air, i.e., the air compressor 110 starts working, drawing in external air, which then passes through the controlled air filter 120 before entering the air compressor 110 and being pressurized. The air then flows to the precooling device 130, and after precooling, it flows into the main intake pipe 143. Through the intake connecting pipe 142, it flows into the adsorption intake pipe 141, which is opened by the electrically controlled valve. After passing through the adsorber 140 connected to the adsorption intake pipe 141, it forms raw material air. This raw material air passes through the throttle valve on the intake pipe 150 and exchanges heat with the main heat exchanger 200 to form a gas-liquid mixture, which is then fed into the lower tower 300. The gas-liquid mixture in the lower tower 300... In column 00, vaporization forms rising gas that exchanges heat with the reflux liquid in column 300 for distillation. Nitrogen gas is formed at the top of column 300. Although column 300 is connected to the first condenser-evaporator 410 and the second condenser-evaporator 420 via pipes, making the inlet pressure of the first condenser-evaporator 410 and the second condenser-evaporator 420 the same as the outlet pressure of column 300, the high-pressure nitrogen gas at the top of column 300 enters the first condenser-evaporator 410 and the second condenser-evaporator 420, exchanges heat with the heat exchange cold source, and undergoes a condensation phase change, transforming from a gaseous state to a liquid state. This phase change process causes a rapid contraction of the fluid volume, thereby creating a suction effect inside the first condenser-evaporator 410 and the second condenser-evaporator 420. A pressure gradient is formed, causing the gaseous nitrogen at the top of the lower column to continuously flow into the first condenser-evaporator 410 and the second condenser-evaporator 420 under the continuous pressure difference, thus maintaining a continuous and efficient condensation heat exchange process. The oxygen-rich liquid air at the bottom of the lower column 300 flows into the first liquid-air separator 430 through the first cold source pipe 431 and / or the liquid nitrogen cold source through the supplementary cold source pipe 432 and both through throttling valves. The cold source in the first liquid-air separator 430 flows into the first condenser-evaporator 410 through the liquid level difference to exchange heat with the nitrogen, forming liquid nitrogen. The gas formed by the vaporization of the cold source enters the bottom of the auxiliary column 500. The oxygen-rich liquid air cold source at the bottom of the auxiliary column 500 flows into the second liquid-air separator 440 through the liquid level difference. Inside, the cold source in the second liquid-air separator 440 flows into the second condenser-evaporator 420 through the liquid level difference to exchange heat with nitrogen, forming liquid nitrogen. The cold source vaporizes to form gas, which then enters the expander 700 after passing through the main heat exchanger 200. After heat exchange in the first condenser-evaporator 410 and the second condenser-evaporator 420, the liquid nitrogen formed by the liquefaction of nitrogen is mixed, and part of the liquid nitrogen flows back to the top of the lower column 300 as the reflux liquid of the lower column. The remaining liquid nitrogen is subcooled by the main heat exchanger 200 and flows into the top of the auxiliary column 500 as the reflux liquid. It then exchanges heat with the rising gas in the auxiliary column 500 for distillation, and nitrogen product is obtained at the top of the auxiliary column 500. The obtained nitrogen product is discharged and collected through the nitrogen product pipe 600.

[0062] It should be noted that both the inlet end of the inlet pipe 150 and the inlet end of the expander 700 are equipped with shut-off valves to control the air intake of the entire nitrogen generator. In case of emergencies such as leaks, operators can control the switching valves to close the corresponding pipelines and quickly cut off the fluid flow to prevent accidents by responding to signals from the PLC controller or an external alarm device electrically connected to the PLC controller. The inlet pipe 150, the first cold source pipe 431, the supplementary cold source pipe 432, the second cold source pipe 441, the first liquid-air separator 430, and the second cold source pipe... Each of the connecting pipes of 441 is equipped with a throttling valve electrically connected to the PLC controller to regulate the flow rate in the pipe; the adsorption inlet pipe 141, adsorption outlet pipe 144, return branch pipe 712, and return discharge pipe 147 are all equipped with automatic switching valves electrically connected to the PLC controller, and the equalizing pipe 146 and the pressure relief pipe are all equipped with automatic regulating valves electrically connected to the PLC controller; wherein, the two ends of the pressure relief pipe are respectively connected to the waste nitrogen return pipe 710 and the return convergence pipe 148, and the PLC controller controls each valve to operate according to the set control logic.

[0063] The above embodiments are illustrative of this application and are not intended to limit this application. Any simple modifications to this application are within the protection scope of this application.

Claims

1. A dual-tower external distillation nitrogen production device, characterized in that, It includes an air pretreatment system (100), a main heat exchanger (200), a lower tower (300), a condenser-evaporator group (400), an auxiliary tower (500), and a nitrogen product pipe (600). An air pretreatment system (100) has an air inlet connected to the air and is used to filter, reduce and purify the air to form raw material air. An air outlet is provided with an air inlet pipe (150), which is used to pass the raw material air through the main heat exchanger (200) for heat exchange and then into the bottom of the lower tower (300). The main heat exchanger (200) is connected to the air pretreatment system (100), the lower tower (300) and the auxiliary tower (500) for heat exchange to reduce the temperature of the raw material air; The lower column (300) is used to separate the raw material air and form nitrogen at the top of the lower column (300); The condenser-evaporator group (400) is connected to the lower tower (300) and the auxiliary tower (500). The oxygen-rich liquid air at the bottom of the lower tower (300) and the bottom of the auxiliary tower (500) is used as a liquid cold source, and the nitrogen at the top of the lower tower (300) is used as a heat source gas. The liquid nitrogen is formed by circulating heat exchange through the thermosiphon principle. The liquid nitrogen is used as the reflux liquid of the lower tower (300) and the auxiliary tower (500). Auxiliary column (500) is used for gas distillation, with nitrogen product obtained at its top; The nitrogen product pipe (600) is connected to the top of the auxiliary tower (500) and is used to discharge the nitrogen product from the top of the auxiliary tower (500).

2. The dual-tower external distillation nitrogen generator according to claim 1, characterized in that, It also includes an expander (700) and a cold box (800); The inlet of the expander (700) is connected to the outlet of the condenser-evaporator group (400), and the outlet is provided with a waste nitrogen return pipe (710), which is connected to the air pretreatment system (100) through the main heat exchanger (200). The lower tower (300), the condenser-evaporator group (400), and the auxiliary tower (500) are located inside the cold box (800).

3. The dual-tower external distillation nitrogen generator according to claim 1 or 2, characterized in that, The condenser-evaporator assembly (400) includes a first condenser-evaporator (410) and a second condenser-evaporator (420) connected to the top of the lower tower (300), a first liquid-air separator (430) connected to the first condenser-evaporator (410), and a second liquid-air separator (440) connected to the second condenser-evaporator (420). The first liquid-air separator (430) is connected to the lower column (300); The second liquid-air separator (440) is connected to the auxiliary tower (500).

4. The dual-tower external distillation nitrogen generator according to claim 3, characterized in that, The inlet ends of the first condenser-evaporator (410) and the second condenser-evaporator (420) are connected to the top of the lower tower (300); The liquid outlet of the first condenser-evaporator (410) is connected to the liquid outlet of the second condenser-evaporator (420) to mix the liquid nitrogen. Part of the mixed liquid nitrogen flows into the top of the lower tower (300), while the other part of the nitrogen enters the top of the auxiliary tower (500) through the main heat exchanger (200).

5. The dual-tower external distillation nitrogen production equipment according to claim 3, characterized in that, The inlet end of the first liquid-air separator (430) is connected to the outlet end of the first condenser-evaporator (410); The inlet of the second liquid-air separator (440) is connected to the outlet of the second condenser-evaporator (420); The outlet of the first liquid-air separator (430) is connected to the bottom of the auxiliary tower (500); The gas discharged from the outlet of the second liquid-air separator (440) enters the expander (700) after passing through the main heat exchanger (200); The first liquid-air separator (430) is provided with a first cold source pipe (431) at the liquid inlet end, and the other end of the first cold source pipe (431) is connected to the bottom of the lower tower (300). The liquid inlet of the second liquid-air separator (440) is provided with a second cold source pipe (441), and the other end of the second cold source pipe (441) is connected to the bottom of the auxiliary tower (500). The first liquid-air separator (430) has two liquid outlets; The liquid outlet of the second liquid-air separator (440) is connected to the liquid inlet of the second condenser-evaporator (420); The two liquid outlets of the first liquid-air separator (430) are respectively connected to the liquid inlet of the first condenser-evaporator (410) and the second cold source pipe (441). The first cold source pipe (431) is connected to the supplementary cold source pipe (432).

6. The dual-tower external distillation nitrogen production equipment according to claim 3, characterized in that, The pressure inside the first liquid-air separator (430) is lower than the pressure of the oxygen-enriched liquid air inside the lower column (300); The pressure inside the second liquid-air separator (440) is lower than the pressure of the oxygen-enriched liquid air inside the auxiliary tower (500); The pressure of the first condenser-evaporator (410) and the pressure of the second condenser-evaporator (420) are both equal to the pressure at the top of the lower column (300).

7. The dual-tower external distillation nitrogen production equipment according to claim 3, characterized in that, The minimum straight-line distance between the second liquid-air separator (440) and the ground is greater than the maximum straight-line distance between the effective heat exchange section of the second condenser-evaporator (420) and the ground; The minimum straight-line distance between the first liquid-air separator (430) and the ground is greater than the maximum straight-line distance between the effective heat exchange section of the first condenser-evaporator (410) and the ground. The cold source in the second liquid-air separator (440) flows into the second condenser-evaporator (420) to exchange heat with nitrogen. At least part of the cold source becomes gas after heat exchange and returns to the second liquid-air separator (440). The nitrogen entering the second condenser-evaporator (420) becomes liquid nitrogen after heat exchange and is discharged from the second condenser-evaporator (420). The cold source in the first liquid-air separator (430) flows into the first condenser-evaporator (410) to exchange heat with nitrogen. At least part of the cold source becomes gas after heat exchange and returns to the first liquid-air separator (430). The nitrogen entering the first condenser-evaporator (410) becomes liquid nitrogen after heat exchange and is discharged from the first condenser-evaporator (410).

8. The dual-tower external distillation nitrogen generator according to claim 2, characterized in that, The air pretreatment system (100) includes an air compressor (110), an air filter (120) connected to the air inlet of the air compressor (110), a precooling device (130) connected to the air outlet of the air compressor (110), and an adsorber (140) connected to the air outlet of the precooling device (130). The inlet pipe (150) is connected to the outlet end of the adsorber (140), and the inlet pipe (150) is connected to the bottom end of the lower tower (300) through the main heat exchanger (200); The waste nitrogen return pipe (710) is connected to the output end of the adsorber (140).

9. The dual-tower full-immersion distillation nitrogen production equipment according to claim 8, characterized in that, The adsorber (140) exists in an adsorption state and a regeneration state; There are two adsorbers (140), and the two adsorbers (140) alternately adsorb and purify the air discharged from the outlet of the precooling device (130); A heater (711) is provided on the waste nitrogen return pipe (710) to heat the waste nitrogen in the waste nitrogen return pipe (710), and the heated waste nitrogen backflushes the adsorber (140) in the regeneration state.

10. The dual-tower full-immersion distillation nitrogen production equipment according to claim 9, characterized in that, The air inlet of the adsorber (140) is provided with an adsorption air inlet pipe (141) and an air inlet connecting pipe (142) that connects the two adsorption air inlet pipes (141). The two ends are respectively connected to the air inlet connecting pipe (142) and the air inlet main pipe (143) at the air outlet of the precooling device (130). The air outlet of the adsorber (140) is provided with an adsorption air outlet pipe (144) and an air outlet connecting pipe (145) connecting the two adsorption air outlet pipes (144). The air outlet connecting pipe (145) is connected to the air inlet pipe (150). A pressure equalization tube (146) is connected between the two adsorption outlet tubes (144). The waste nitrogen return pipe (710) is provided with a return branch pipe (712) connected to the adsorption outlet pipe (144). Both adsorption inlet pipes (141) are equipped with reflux discharge pipes (147), and the two reflux discharge pipes (147) converge into the reflux convergence pipe (148).

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