Air separation nitrogen production system

Abstract

The application discloses an air separation nitrogen production system and relates to the technical field of nitrogen production systems. The air separation nitrogen production system comprises a downcomer fixedly arranged on an upper side tray plate and abutting against a lower side tray plate. An arc-shaped upper liquid outlet and a lower liquid outlet are symmetrically arranged on a first end of the downcomer. The axis positions of the upper liquid outlet and the lower liquid outlet coincide. The horizontal heights of the upper liquid outlet and the lower liquid outlet are lower than the height of an overflow weir of the lower side tray plate. The air separation nitrogen production system provided by the application utilizes the arc-shaped upper liquid outlet and the lower liquid outlet of the downcomer to discharge liquid to the top of the tray plate. The liquid streams sprayed by the upper liquid outlet and the lower liquid outlet can be mixed after being sprayed along the arc. A stratosphere is formed in the liquid layer at the top of the tray plate. The problem that the backflow liquid sprayed by the downcomer easily impacts the upper layer of the liquid layer on the tray plate to generate excessive liquid foam is solved. The amount of liquid foam carried to the upper tray plate by the rising gas flow is reduced, and the fractionation gradient is protected.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of nitrogen production systems, in particular to an air separation nitrogen production system. BACKGROUND

[0002] It is known that in natural gas pretreatment, an air separation nitrogen production system is often needed to produce high-purity nitrogen, and the nitrogen is introduced into a natural gas pipeline or a storage tank to replace air, so that the oxygen content is reduced to <=0.5% to prevent natural gas from exploding with air.

[0003] For example, an invention patent with the application announcement number CN215766047U and the application announcement date of February 8, 2022 and the name of a fractionating tower for quickly extracting nitrogen and oxygen discloses a fractionating tower including a machine body base and an oxygen outlet, the machine body base is fixedly installed with an oxygen production cavity at the middle position of the top surface, and the top surface of the oxygen production cavity is fixedly connected with the fractionating tower.

[0004] The existing technology has the following problems: the tray and the downcomer in the fractionating tower are used to realize the downward flow of the reflux liquid at the top of the tower along the tray and the downcomer layer by layer, and the reflux liquid (oxygen-rich liquid air) and the ascending vapor (containing high-concentration nitrogen) are reversely contacted on the tray. However, the upper end of the downcomer is a flow inlet, and the lower end is a single flow outlet. When the reflux liquid in the downcomer is sprayed out of the flow outlet due to liquid pressure, the reflux liquid is in the form of a bucket due to the internal liquid pressure of the downcomer, and then the reflux liquid sprayed by the downcomer easily impacts the upper layer of the liquid layer on the tray to generate excessive liquid foam. The excessive liquid foam is carried to the upper tray by the ascending gas flow, so that the low-volatility component (oxygen) is mixed into the high-volatility component (nitrogen) region, the fractionation gradient is destroyed, and the purity of the nitrogen product is reduced. SUMMARY

[0005] The application aims to provide an air separation nitrogen production system to solve the problem that the reflux liquid sprayed by the downcomer easily impacts the upper layer of the liquid layer on the tray to generate excessive liquid foam in the prior art.

[0006] To achieve the above-mentioned purpose, the application provides the following technical scheme: an air separation nitrogen production system includes an upper tower body and a plurality of trays fixedly arranged in the upper tower body in a spaced array, the trays are provided with overflow weirs, and the system further includes a downcomer fixedly arranged on the upper side tray to abut against the lower side tray, the downcomer is symmetrically provided with an upper liquid discharge port and a lower liquid discharge port in an arc shape at the first end, and the axes of the upper liquid discharge port and the lower liquid discharge port coincide, and the horizontal heights of the upper liquid discharge port and the lower liquid discharge port are lower than the height of the overflow weir of the lower side tray.

[0007] As a further description of the above technical solution: the inner fixedly provided protruding part in the downcomer is partially cylindrical to be located between the upper liquid outlet and the lower liquid outlet, and the protruding part is in contact with the side walls of the upper liquid outlet and the lower liquid outlet.

[0008] As a further description of the above technical solution: it further comprises a liquid blocking seat movably provided in the downcomer and partially arc-shaped to fit the protruding part, both ends of the liquid blocking seat are provided with through grooves in which demisters are fixedly arranged, the demisters are respectively located in the upper liquid outlet and the lower liquid outlet, and a first end of the liquid blocking seat is fixedly provided with a blocking plate obliquely shielding the outside of the upper liquid outlet.

[0009] As a further description of the above technical solution: the demisters are multiple and arranged in a circumferential array in the through grooves, and the liquid blocking seat is driven to slide arcuately so that the demisters move relative to the inner cavities of the upper liquid outlet and the lower liquid outlet.

[0010] As a further description of the above technical solution: the blocking plate is symmetrically provided with arching parts, the liquid blocking seat is driven to slide arcuately so that the arching parts of the blocking plate are in contact with the downcomer, and the blocking plate blocks the upper liquid outlet.

[0011] As a further description of the above technical solution: it further comprises a connecting rod and a floating seat located in the downcomer, both ends of the connecting rod are rotatably connected to the floating seat and the liquid blocking seat respectively, the floating seat is moved upward by buoyancy to pull the liquid blocking seat to slide arcuately, and the blocking plate is moved away from the upper liquid outlet.

[0012] As a further description of the above technical solution: an entering groove is formed in the inner wall of the downcomer, the entering groove has a guide slope, and the floating seat is moved along the guide slope to the entering groove by buoyancy.

[0013] As a further description of the above technical solution: the end face of the first end of the floating seat is arc-shaped corresponding to the arc-shaped inner wall of the downcomer, and the floating seat is in a horizontal state so that an arc-shaped flow passage is formed between the first end of the floating seat and the arc-shaped inner wall of the downcomer.

[0014] As a further description of the above technical solution: the downcomer is fixedly provided with a limiting part, the liquid blocking seat is fixedly provided with a contact part, and the limiting part is fixedly provided with an elastic bag between the limiting part and the contact part, the elastic bag drives the liquid blocking seat to slide and reset so that the blocking plate blocks the upper liquid outlet.

[0015] As a further description of the above technical solution: the surface of the liquid blocking seat is provided with a tungsten carbide coating.

[0016] In the technical scheme, the air separation nitrogen production system provided by the application uses the upper liquid discharge port and the lower liquid discharge port in the arc shape of the downcomer to discharge liquid to the top of the tray, so that the liquid streams discharged by the upper liquid discharge port and the lower liquid discharge port can be mixed after being discharged along the arc shape, and then a stratosphere is formed in the liquid layer at the top of the tray, thereby relieving the problem that the reflux liquid discharged by the downcomer easily impacts the upper layer of the liquid layer on the tray to generate excessive liquid foam, reducing the amount of liquid foam carried to the upper tray by the rising gas flow to protect the fractionation gradient, and improving the purity of the prepared nitrogen product. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0018] Figure 1 The flowchart of the air separation nitrogen production system provided by the embodiment of the present application is shown.

[0019] Figure 2 The overall three-dimensional structure schematic diagram provided by the embodiment of the present application is shown.

[0020] Figure 3 The overall structure cross-sectional view schematic diagram provided by the embodiment of the present application is shown.

[0021] Figure 4 The three-dimensional structure schematic diagram of the tray, the downcomer and the liquid blocking seat provided by the embodiment of the present application is shown.

[0022] Figure 5 The exploded structure schematic diagram of the downcomer, the liquid blocking seat, the connecting rod and the floating seat provided by the embodiment of the present application is shown.

[0023] Figure 6 The three-dimensional structure schematic diagram of the liquid blocking seat, the defoaming net, the connecting rod and the floating seat provided by the embodiment of the present application is shown.

[0024] Figure 7 The three-dimensional structure schematic diagram of the tray provided by the embodiment of the present application is shown.

[0025] Figure 8 The structure cross-sectional view schematic diagram of the tray provided by the embodiment of the present application is shown.

[0026] Figure 9 The three-dimensional structure exploded schematic diagram of the liquid blocking seat, the defoaming net, the connecting rod and the floating seat provided by the embodiment of the present application is shown.

[0027] Figure 10 The three-dimensional structure exploded schematic diagram of the liquid blocking seat, the defoaming net, the connecting rod and the floating seat provided by the embodiment of the present application is shown. Figure 3A local structure at the middle A is shown in an enlarged schematic view;

[0028] Figure 11 The technical scheme provided by the embodiment of the present application Figure 10 A local structure at the middle B is shown in an enlarged schematic view.

[0029] Explanation of reference signs:

[0030] 1, upper tower body; 11, feed inlet; 12, gas inlet; 13, reflux inlet; 14, gas outlet; 2, tower plate; 21, overflow weir; 22, mounting groove; 3, downcomer; 31, liquid inlet; 32, upper liquid outlet; 33, lower liquid outlet; 34, protruding part; 341, limiting part; 35, entering groove; 4, liquid blocking seat; 41, passing groove; 42, blocking plate; 43, abutting part; 5, demister; 6, connecting rod; 7, floating seat; 8, elastic bag. DETAILED DESCRIPTION

[0031] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in conjunction with the drawings.

[0032] Please refer to Figures 1-11 The embodiment of the present application provides a technical scheme: an air separation nitrogen production system, comprising an upper tower body 1 and a tower plate 2 fixedly arranged in the upper tower body 1 in a spaced array, the tower plate 2 is provided with an overflow weir 21, further comprising a downcomer 3 fixedly arranged on the upper side tower plate 2 to abut on the lower side tower plate 2, the first end of the downcomer 3 is symmetrically provided with an arc-shaped upper liquid outlet 32 and a lower liquid outlet 33, and the axis positions of the upper liquid outlet 32 and the lower liquid outlet 33 coincide, and the horizontal heights of the upper liquid outlet 32 and the lower liquid outlet 33 are lower than the height of the overflow weir 21 of the lower side tower plate 2.

[0033] Preferably, the upper tower body 1 is provided with a feed inlet 11, an air inlet 12, a reflux inlet 13 and an air outlet 14 communicated to the inside of the upper tower body 1, the feed inlet 11 is communicated to the middle part of the upper tower body 1, the air inlet 12 is communicated to the bottom part of the upper tower body 1, the reflux inlet 13 is communicated to the upper part of the upper tower body 1, and the air outlet 14 is communicated to the top of the upper tower body 1, and the tower plate 2 is further provided with a through hole for air flow. The air separation and nitrogen production system further comprises a filter, a centrifugal compressor, an air cooling tower, a molecular sieve adsorber, an adsorption tower, a heat exchanger, a turbine expander and a crude distillation lower tower. First, air is used as raw material, the air passes through the filter to remove dust and mechanical impurities, then the centrifugal compressor pressurizes the air to 0.6-1.0 MPa, the compressed air is pre-cooled to 10-20℃ in the air cooling tower, and then the water, CO2 and hydrocarbons are removed by the molecular sieve adsorber, the adsorption tower and the molecular sieve adsorber are alternately operated to further improve the removal rate of water, CO2 and hydrocarbons, then the purified air enters the main heat exchanger and is cooled to below-168℃ by the reflux gas, then the air is cooled to-183℃ by the heat exchanger and the expander to supplement the cold quantity and liquefied to form liquid air, the liquid air is introduced into the crude distillation lower tower to separate the oxygen-rich liquid air and the crude nitrogen gas by using the boiling point difference between oxygen and nitrogen, the oxygen-rich liquid air is introduced into the middle part of the upper tower body 1 of the rectification upper tower, and the crude nitrogen gas is introduced into the bottom of the upper tower body 1, and after multiple evaporation and condensation, the air outlet 14 of the upper tower body 1 outputs 99.999% high-purity nitrogen gas, part of the nitrogen gas is liquefied and re-enters the upper tower body 1 through the reflux inlet 13 to maintain the temperature gradient in the tower and ensure the gas-liquid balance, and another part of the high-purity nitrogen gas is reheated to room temperature by another heat exchanger and output, and the production of nitrogen gas is completed.

[0034] As shown in Figure 2 Each tower plate 2 is fixedly provided with a downcomer 3, the downcomer 3 can be welded to the installation groove 22 of the tower plate 2, and the lower part of the downcomer 3 is in contact with the tower plate 2 on the lower side, and as shown in Figure 10As shown, the lower end of the downcomer 3 is the first end, and the upper end is the second end, and the liquid inlet 31 is arranged at the upper end of the downcomer 3, and the horizontal height of the liquid inlet 31 is higher than the height of the overflow weir 21, and the upper liquid outlet 32 and the lower liquid outlet 33 of the downcomer 3 are both lower than the height of the overflow weir 21 of the lower side tower plate 2, so that when the liquid on the upper side tower plate 2 is too much, it can overflow into the downcomer 3 through the liquid inlet 31, and the downcomer 3 can be drained to the lower side tower plate 2 through the upper liquid outlet 32 and the lower liquid outlet 33, so that the lower side tower plate 2 can also form a liquid layer through the overflow weir 21. The downcomer 3 utilizes the symmetric arc-shaped upper liquid outlet 32 and lower liquid outlet 33 to drain the liquid to the top of the tower plate 2, so that the liquid flow sprayed by the upper liquid outlet 32 and the lower liquid outlet 33 can be mixed after being sprayed along the arc, and then a laminar layer is formed in the liquid layer at the top of the tower plate 2, thereby alleviating the problem that the backflow liquid sprayed by the downcomer 3 easily impacts the upper layer of the liquid layer on the tower plate 2 to generate excessive liquid foam, reducing the amount of liquid foam carried to the upper tower plate 2 by the rising gas flow, and protecting the fractionation gradient, thereby improving the purity of the prepared nitrogen product.

[0035] Among them, the filter, centrifugal compressor, air cooling tower, molecular sieve adsorber, adsorption tower, heat exchanger, turbine expander and crude distillation lower tower all belong to the common technical knowledge of those skilled in the art, and will not be repeated here.

[0036] In the above technical solution, the arc-shaped upper liquid outlet 32 and lower liquid outlet 33 of the downcomer 3 are used to drain the liquid to the top of the tower plate 2, so that the liquid flow sprayed by the upper liquid outlet 32 and the lower liquid outlet 33 can be mixed after being sprayed along the arc, and then a laminar layer is formed in the liquid layer at the top of the tower plate 2, thereby alleviating the problem that the backflow liquid sprayed by the downcomer 3 easily impacts the upper layer of the liquid layer on the tower plate 2 to generate excessive liquid foam, reducing the amount of liquid foam carried to the upper tower plate 2 by the rising gas flow, and protecting the fractionation gradient, thereby improving the purity of the prepared nitrogen product.

[0037] In still another embodiment of the present application, a protruding portion 34 in a partial cylindrical shape is fixedly arranged in the downcomer 3 between the upper liquid outlet 32 and the lower liquid outlet 33, and the protruding portion 34 is connected with the side walls of the upper liquid outlet 32 and the lower liquid outlet 33.

[0038] Preferably, as Figure 8As shown, the protruding portion 34 is integral with the downcomer 3, and the protruding portion 34 is partially cylindrical and protrudes between the upper liquid outlet 32 and the lower liquid outlet 33. Since the liquid in the downcomer 3 flows to the upper liquid outlet 32 and the lower liquid outlet 33 under the influence of gravity, when the liquid in the liquid inlet 31 flows vertically downward, it first impacts the protruding portion 34 and then flows along the surface of the protruding portion 34 to the upper liquid outlet 32 and the lower liquid outlet 33 for discharge. This reduces the vortex formed by the vertical impact of the liquid in the downcomer 3 on the inner side of the upper liquid outlet 32 and the lower liquid outlet 33, thereby further improving the flow stability of the liquid sprayed by the upper liquid outlet 32 and the lower liquid outlet 33 to the top of the tray 2, and reducing the generation of liquid foam on the liquid layer on the top of the tray 2.

[0039] In another embodiment of the present application, a liquid blocking seat 4 is movably arranged in the downcomer 3 and is partially arc-shaped to fit the protruding portion 34. The liquid blocking seat 4 is provided with a through slot 41 at each end, and the through slot 41 is internally fixedly provided with a demister 5. The demister 5 is located in the upper liquid outlet 32 and the lower liquid outlet 33, respectively. The first end of the liquid blocking seat 4 is fixedly provided with a baffle plate 42 that is inclined to block the outside of the upper liquid outlet 32.

[0040] Preferably, as shown in the drawings, Figure 10 The liquid blocking seat 4 is partially arc-shaped so that it can slide along the protruding portion 34 in an arc shape. The two ends of the liquid blocking seat 4 are each provided with a through slot 41. The ends of the liquid blocking seat 4 extend into the upper liquid outlet 32 and the lower liquid outlet 33, respectively, so that the demisters 5 are located in the upper liquid outlet 32 and the lower liquid outlet 33.

[0041] When the liquid in the downcomer 3 is discharged from the upper liquid outlet 32 and the lower liquid outlet 33 to the top of the tray 2, the liquid in the downcomer 3 enters the upper liquid outlet 32 and the lower liquid outlet 33 through the through slots 41, respectively. The liquid needs to pass through the demisters 5 before being sprayed from the upper liquid outlet 32 and the lower liquid outlet 33, thereby further reducing the generation of liquid foam on the liquid layer on the tray 2 by using the demisters 5.

[0042] Secondly, the end of the liquid blocking seat 4 close to the upper liquid outlet 32 is the first end. The first end of the liquid blocking seat 4 is provided with a baffle plate 42. When the backflow liquid in the downcomer 3 is discharged from the upper liquid outlet 32 to the top of the tray 2, the liquid first impacts the baffle plate 42 and then flows over the baffle plate 42 to the liquid layer on the tray 2, thereby further reducing the generation of liquid foam by the liquid discharged from the upper liquid outlet 32 by using the baffle plate 42. Secondly, it can also make the flow speed of the upper layer of the liquid layer on the tray 2 smaller than that of the lower layer, so that the upper layer of the liquid layer on the tray 2 flows close to the lower layer of the liquid layer on the tray 2 due to the flow speed difference, thereby further improving the resistance of the liquid layer on the tray 2 to the upward gas flow and increasing the gas-liquid contact time to improve the separation efficiency of nitrogen.

[0043] In another embodiment of the present invention, a plurality of demisters 5 are arranged in a circumferential array within the channel 41, and the liquid baffle 4 is driven to slide in an arc shape so that a plurality of demisters 5 move relative to the inner cavity of the upper drain port 32 and the lower drain port 33.

[0044] Preferred, such as Figure 11 As shown, multiple demisters 5 are installed in the channel 41. Since the horizontal height of the upper drain port 32 is higher than that of the lower drain port 33, when the return liquid in the downcomer 3 has a certain liquid level, the liquid ejection velocity of the lower drain port 33 is greater than that of the upper drain port 32 due to the influence of liquid pressure. However, if the difference in liquid ejection velocity between the upper drain port 32 and the lower drain port 33 is too large, it may also cause eddies in the upper and lower layers of the liquid layer on the tray 2, which may lead to the appearance of additional liquid foam. Therefore, the baffle seat 4 can be driven to slide in an arc shape to control the number of demisters 5 in the upper drain port 32 and the lower drain port 33, thereby controlling the flow resistance in the upper drain port 32 and the lower drain port 33. This enables control of the flow velocity difference between the liquid flow velocity at the lower drain port 33 and the lower drain port 33, thus avoiding the problem of excessive flow velocity difference between the liquid flow at the upper drain port 32 and the lower drain port 33, which would generate additional liquid foam. This achieves flow velocity regulation of the upper drain port 32 and the lower drain port 33.

[0045] In the downcomer 3, a controller can be used in conjunction with a piston cylinder to drive the baffle seat 4 to slide, or a drive motor can be used in conjunction with gears to drive the baffle seat 4 to slide. Alternatively, other driving methods known to those skilled in the art can be used as alternatives.

[0046] In another embodiment of the present invention, the baffle plate 42 is symmetrically provided with arched portions, and the liquid blocking seat 4 is driven to slide in an arc shape so that the arched portions of the baffle plate 42 abut against the downcomer 3, and the baffle plate 42 abuts against and blocks the upper drain port 32.

[0047] Preferred, such as Figure 11As shown, arched sections are symmetrically arranged on the baffle plate 42, and contact grooves are respectively opened on both sides of the upper drain port 32 of the downcomer 3. In the actual nitrogen production process, the liquid phase load and gas phase load in the upper column 1 are constantly fluctuating. However, when the liquid phase load is too low, that is, when the amount of reflux liquid is small, when the liquid level in the downcomer 3 drops below the horizontal height of the upper drain port 32, the gas in the upper column 1 will enter the downcomer 3 through the upper drain port 32 and flow to the upper column plate 2 from the liquid inlet 31. That is, the gas in the upper column 1 penetrates the liquid seal layer in the downcomer 3 to form a short-circuit channel, which leads to insufficient gas-liquid contact and a decrease in nitrogen fractionation efficiency. By utilizing the presence of the baffle plate 42 on the liquid baffle seat 4, when the liquid load is too low, the liquid baffle seat 4 can be driven to slide in an arc shape, causing the baffle plate 42 to move closer to the downcomer 3 until the arched part of the baffle plate 42 abuts against the abutting groove of the downcomer 3. At this time, the baffle plate 42 can block the upper drain port 32, so that under low liquid load, the liquid layer in the downcomer 3 can still maintain the blockage of the gas in the upper tower 1, avoiding the problem of reduced fractionation efficiency caused by the formation of a gas short circuit channel at the downcomer 3 under low liquid load, and improving the stability of nitrogen fractionation operation.

[0048] In another embodiment of the present invention, a connecting rod 6 and a float seat 7 are located inside the downcomer 3. The two ends of the connecting rod 6 are rotatably connected to the float seat 7 and the liquid-blocking seat 4, respectively. The float seat 7 is lifted by buoyancy to pull the liquid-blocking seat 4 to slide in an arc shape, and causes the blocking plate 42 to move away from the upper drain port 32.

[0049] Preferred, such as Figure 11 As shown, the float seat 7 is connected to the downcomer 3 via the connecting rod 6. When there is a certain liquid level in the downcomer 3, the float seat 7 floats on top of the liquid layer in the downcomer 3. Therefore, when the liquid load in the upper tower 1 gradually decreases to a dangerous value, the height of the float seat 7 decreases along with the liquid level, causing the baffle seat 4 to slide in an arc shape under the force of gravity, which in turn causes the baffle plate 42 to move closer to the upper drain port 32 and block the upper drain port 32. This prevents the formation of a gas short-circuit channel in the downcomer 3 when the liquid load is too low. Furthermore, by using the float seat 7 and the connecting rod 6, the baffle seat 4 can be adjusted according to the liquid load to block the upper drain port 32, thus achieving automatic blocking of the upper drain port 32 under low liquid load to avoid the problem of gas short circuit.

[0050] The flow velocity at the upper drain port 32 and the lower drain port 33 has a non-linear relationship with the pressure in the downcomer 3. The velocity difference between the upper drain port 32 and the lower drain port 33 decreases as the liquid level in the downcomer 3 increases. When there is a high liquid level in the downcomer 3, both the upper drain port 32 and the lower drain port 33 can discharge liquid under high pressure. However, when the liquid level in the downcomer 3 is low, the liquid pressure on both the upper drain port 32 and the lower drain port 33 decreases, which leads to an increase in the velocity difference between the upper drain port 32 and the lower drain port 33.

[0051] When the height of the liquid layer in the float seat 7 and the downcomer 3 moves, the baffle seat 4 slides along with it due to the gravity of the float seat 7 and the connecting rod 6. This allows the baffle seat 4 to dynamically adjust the number of demisters 5 in the upper drain port 32 and the lower drain port 33 according to the change of liquid phase load. This further enables automatic control of the flow rate difference between the upper drain port 32 and the lower drain port 33 according to the change of liquid phase load, thereby reducing the liquid foam generated due to the flow rate difference.

[0052] In another embodiment of the present invention, an inlet groove 35 is provided on the inner wall of the downcomer 3. The inlet groove 35 has a guide ramp so that the float seat 7 moves upward under buoyancy and moves along the guide ramp to the inlet groove 35.

[0053] Preferred, such as Figure 5 As shown, the downcomer 3 is arc-shaped so that its internal flow cross-section is also arc-shaped. The inlet trough 35 is located on the plane of the inner wall of the downcomer 3. When the liquid load is at a normal level, the float 7 moves upward under buoyancy, and its end moves along the guide slope to the inlet trough 35, thus maintaining a large flow cross-sectional area within the downcomer 3. Furthermore, when liquid flows into the downcomer 3 from the inlet 31, the float 7 can catch the downstream liquid to reduce the impact force of the liquid on the liquid layer inside the downcomer 3, thereby further reducing the generation of liquid droplets. When the liquid load in the upper tower 1 is too high, the liquid level in the downcomer 3 gradually rises. The float seat 7 is pulled to its highest position by the connecting rod 6. When the liquid level in the downcomer 3 rises above the highest position of the float seat 7, the float seat 7 is pushed by the inlet trough 35 at one end, causing it to flip due to the buoyancy of the liquid layer in the downcomer 3. This makes the float seat 7 perpendicular to the horizontal plane, instantly increasing the cross-sectional area of ​​the flow in the downcomer 3. This avoids the problem of the liquid layer in the downcomer 3 overflowing onto the upper tower plate 2 when the liquid load is too high, thus improving the downcomer efficiency of the downcomer 3.

[0054] In another embodiment of the present invention, the end face of the first end of the float seat 7 is arc-shaped corresponding to the arc-shaped inner wall of the downcomer 3, and the float seat 7 is in a horizontal state so that an arc-shaped flow gap is formed between the first end of the float seat 7 and the arc-shaped inner wall of the downcomer 3.

[0055] Preferred, such asFigure 11 As shown, the left end of the float seat 7 is the first end. When the liquid load in the upper column 1 decreases, the liquid level in the downcomer 3 decreases so that the float seat 7 moves down accordingly. At this time, the float seat 7 moves down so that its end leaves the inlet trough 35 and touches the inner wall of the downcomer 3. The first end of the float seat 7 faces the arc-shaped inner wall of the downcomer 3, thus forming an arc-shaped flow gap between the first end of the float seat 7 and the arc-shaped inner wall of the downcomer 3. The liquid flowing into the inlet 31 first impacts the float seat 7 to form a certain liquid layer and continues to overflow downward along the flow gap. Then, the float seat 7 is used to form a secondary liquid seal layer in the downcomer 3, further avoiding the problem of reduced fractionation efficiency caused by the formation of a gas short-circuit channel at the downcomer 3.

[0056] The liquid-blocking seat 4 is provided with an elastic element for driving the connecting rod 6 to rotate so that the float seat 7 always abuts against the inner wall of the downcomer 3. The elastic element can be replaced by other elastic objects known to those skilled in the art, such as airbags, elastic plates or worm springs.

[0057] In another embodiment of the present invention, the downcomer 3 is fixedly provided with a limiting part 341, the liquid baffle 4 is fixedly provided with an abutting part 43, and the limiting part 341 is fixedly provided with an elastic bladder 8 located between the limiting part 341 and the abutting part 43. The elastic bladder 8 drives the liquid baffle 4 to slide back to the blocking plate 42 to block the upper drain port 32.

[0058] Preferred, such as Figure 8 As shown, the limiting part 341 and the downcomer 3 are integrated, as... Figure 9 As shown, the contact part 43 and the liquid-blocking seat 4 are integrated, while the elastic bladder 8 is fixedly connected to the limiting part 341 and the contact part 43. When the liquid load in the upper tower body 1 is under normal conditions, the floating seat 7 pulls the liquid-blocking seat 4 to rotate through the connecting rod 6 until the contact part 43 contacts the limiting part 341, at which time the elastic bladder 8 is compressed by the contact part 43 and the limiting part 341. When the liquid load in the upper tower body 1 is too low, the horizontal height of the floating seat 7 decreases, and the elastic bladder 8 deforms and resets to push the contact part 43 away from the limiting part 341. The liquid-blocking seat 4 slides to the baffle plate 42 to block the upper drain port 32, thereby ensuring the stable blocking of the upper drain port 32 by the liquid-blocking seat 4 under low liquid load conditions.

[0059] In another embodiment of the present invention, the surface of the liquid baffle 4 is provided with a tungsten carbide coating.

[0060] Preferably, the surface of the liquid baffle 4 is provided with a tungsten carbide coating to improve the corrosion resistance and impact resistance of the liquid baffle 4 and increase its service life.

[0061] Working principle:

[0062] Firstly, air is used as raw material, and the air is filtered to remove dust and mechanical impurities, and then a centrifugal compressor pressurizes the air to 0.6-1.0 MPa, the compressed air is pre-cooled to 10-20℃ in an air cooling tower, and then removed water, CO2 and hydrocarbons through a molecular sieve adsorber, and then the purified air enters the main heat exchanger and is cooled to below-168℃ by the return gas, and then the air is cooled to-183℃ by the heat exchanger and the expander to supplement the cold and liquefy to form liquid air, the liquid air is introduced into the rectification tower to separate the oxygen-rich liquid air and crude nitrogen gas by using the boiling point difference between oxygen and nitrogen, the oxygen-rich liquid air is introduced into the middle of the upper tower body 1 of the rectification upper tower, and the crude nitrogen gas is introduced into the bottom of the upper tower body 1, and after multiple evaporation and condensation, 99.999% high-purity nitrogen gas is produced from the gas outlet 14 of the upper tower body 1, part of the nitrogen gas is liquefied and re-enters the upper tower body 1 through the return port 13 to maintain the temperature gradient in the tower and ensure the gas-liquid balance, and the other part of the high-purity nitrogen gas is reheated to normal temperature through another heat exchanger and output, completing the production of nitrogen gas;

[0063] When the liquid phase load is at a normal level, the floating seat 7 is moved upward by the buoyancy and the end is moved along the guide slope to enter the groove 35, so that the liquid level in the downcomer 3 can still maintain a larger flow cross-sectional area, and secondly when the liquid in the liquid inlet 31 flows into the downcomer 3, the floating seat 7 can receive the flowing liquid to reduce the impact force of the liquid on the liquid layer in the downcomer 3;

[0064] When the liquid phase load in the upper tower body 1 is too large, the liquid level height in the downcomer 3 gradually rises, and the floating seat 7 has the highest position due to the pulling of the connecting rod 6, when the liquid level height of the downcomer 3 rises to exceed the highest position of the floating seat 7, the floating seat 7 is flipped due to the resistance of the entering groove 35 at one end, so that the floating seat 7 is perpendicular to the horizontal plane to instantaneously increase the flow cross-sectional area of the downcomer 3;

[0065] When the liquid phase load in the upper tower body 1 decreases, the liquid level height in the downcomer 3 decreases, so that the floating seat 7 follows and moves downward, at this time the floating seat 7 moves downward to abut against the inner wall of the downcomer 3 after the end part leaves the entering groove 35, and the first end of the floating seat 7 faces the arc-shaped inner wall of the downcomer 3, thereby forming an arc-shaped flow gap between the first end of the floating seat 7 and the arc-shaped inner wall of the downcomer 3, the liquid in the liquid inlet 31 first impacts on the floating seat 7 to form a certain liquid layer and continues to overflow downward along the flow gap, thereby forming a secondary liquid sealing layer in the downcomer 3 by using the floating seat 7, and the elastic bag 8 deforms and resets to push the abutting part 43 away from the limiting part 341, and the liquid blocking seat 4 slides to block the upper liquid outlet 32 by the blocking plate 42.

[0066] The foregoing merely illustrates some exemplary embodiments of the application, and it will be appreciated that those skilled in the art will be able to devise various modifications without departing from the spirit and scope of the application. The appended drawings and description are illustrative only, and are not intended to be limiting.

Claims

1. An air separation nitrogen production system comprising an upper column body and column trays fixedly disposed in a spaced apart array within the upper column body, the column trays having weir overflow dams disposed thereon, characterized in that, It also includes a downcomer fixedly installed on the upper side plate to abut against the lower side plate. The first end of the downcomer is symmetrically provided with an arc-shaped upper drain port and a lower drain port, and the axial positions of the upper drain port and the lower drain port coincide. The horizontal height of the upper drain port and the lower drain port is lower than the overflow weir height of the lower side plate. The upper tower body is provided with a feed inlet, an air inlet, a reflux inlet and an air outlet that connect to its interior. The feed inlet connects to the middle of the upper tower body, the air inlet connects to the bottom of the tower, the reflux inlet connects to the upper part of the upper tower body, and the air outlet connects to the top of the upper tower body. The tower plate is also provided with through holes for airflow. The upper end of the downcomer has an inlet, and the horizontal height of the inlet is higher than the height of the overflow weir.

2. An air separation nitrogen production system as claimed in claim 1, wherein, The downcomer is fixedly provided with a partially cylindrical protrusion, which is located between the upper and lower drain ports and is connected to the sidewalls of the upper and lower drain ports.

3. An air separation nitrogen production system as claimed in claim 2, wherein, It also includes a liquid baffle seat that is movably installed inside the downcomer and is partially arc-shaped to fit the protrusion. Both ends of the liquid baffle seat are provided with through grooves containing demisters. The demisters are located inside the upper and lower drain ports, respectively. The first end of the liquid baffle seat is fixedly provided with an inclined baffle plate that blocks the outside of the upper drain port.

4. An air separation nitrogen production system as claimed in claim 3, wherein, The demisters are arranged in a circular array within the passageway, and the liquid baffle is driven to slide in an arc shape so that the demisters move relative to the inner cavities of the upper and lower drain ports.

5. An air separation nitrogen production system as claimed in claim 4, wherein, The baffle plate is symmetrically provided with arched parts, and the liquid-blocking seat is driven to slide in an arc shape so that the arched parts of the baffle plate abut against the downcomer pipe, and the baffle plate abuts against and blocks the upper drain port.

6. An air separation nitrogen production system as claimed in claim 5, wherein, It also includes a connecting rod and a float seat located inside the downcomer. The two ends of the connecting rod are rotatably connected to the float seat and the liquid-blocking seat, respectively. The float seat moves upward under buoyancy to pull the liquid-blocking seat to slide in an arc shape, and causes the blocking plate to move away from the upper drain port.

7. An air separation nitrogen production system as claimed in claim 6, wherein, An inlet groove is provided on the inner wall of the downcomer, and the inlet groove has a guide ramp so that the float seat moves upward under buoyancy and moves along the guide ramp to the inlet groove.

8. An air separation nitrogen production system as claimed in claim 7, wherein, The end face of the first end of the float seat is arc-shaped, corresponding to the arc-shaped inner wall of the downcomer, and the float seat is in a horizontal state so that an arc-shaped flow gap is formed between the first end of the float seat and the arc-shaped inner wall of the downcomer.

9. An air separation nitrogen production system as claimed in claim 6 wherein, The downcomer is fixedly provided with a limiting part, the liquid baffle is fixedly provided with an abutting part, and the limiting part is fixedly provided with an elastic bladder located between the limiting part and the abutting part. The elastic bladder drives the liquid baffle to slide back to the baffle plate to block the upper drain port.

10. The air separation nitrogen production system of claim 3, wherein, The surface of the liquid baffle is coated with tungsten carbide.

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