Nitric acid absorption tower and purification method

Abstract

The invention relates to the technical field of absorption towers, in particular to a nitric acid absorption tower and a purification method.The nitric acid absorption tower comprises a tower body, a plurality of sieve plates are arranged in the tower body, the tower body is evenly divided into a plurality of absorption layers and a liquid accumulation layer through the sieve plates, the liquid accumulation layer is located below all the absorption layers, and a liquid conveying opening is formed in the surface of the tower body; the liquid conveying opening is communicated with the absorption layer located at the uppermost end, a plurality of first conveying pipes used for being communicated with every two adjacent absorption layers are installed on the surface of the tower body, an opening in the upper end of each first conveying pipe is a liquid inlet, and an opening in the lower end of each first conveying pipe is a liquid outlet; the invention aims to solve the problems that the existing absorption tower cannot crush bubbles in the absorption tower, so that nitrogen dioxide in the bubbles cannot be fully dissolved and reacted, gas discharged from the tower top further contains a large amount of nitrogen oxides, and the nitrogen oxides are not separated completely.

Description

Technical Field

[0001] This invention relates to the field of absorption tower technology, specifically to a nitric acid absorption tower and purification method. Background Technology

[0002] Industrial production generates large amounts of nitrogen oxide waste gas, including nitric oxide and nitrogen dioxide. These nitrogen oxides pose serious hazards to human health and the environment, such as irritating the respiratory tract and causing respiratory diseases. They are also one of the main causes of acid rain and acid fog. Nitric acid absorption towers are mainly used to absorb nitrogen oxides, primarily nitric oxide and nitrogen dioxide, and convert them into nitric acid, separating them from the waste gas. In the absorption tower, water or dilute nitric acid is usually used as the absorbent. Through a series of physical and chemical reactions, nitrogen oxides are continuously absorbed and converted into nitric acid, thus separating the nitrogen oxides from the waste gas. The tower body is usually made of corrosion-resistant materials, such as stainless steel and special alloy steel, to adapt to the highly corrosive environment of the nitric acid production process. Waste gas containing nitrogen oxides enters the absorption tower from the bottom and comes into countercurrent contact with the absorbent sprayed from the top of the tower. During the contact process, the nitrogen oxides react with the absorbent and are absorbed into nitric acid. As the reaction proceeds, the concentration of nitric acid continuously increases and eventually flows out from the bottom of the tower, while the absorbed gas is discharged from the top of the tower.

[0003] In existing absorption towers, during the contact process between gases and absorbents, due to solubility limitations and changes in physicochemical conditions, some gases may not completely dissolve and form bubbles. For example, when gases such as nitrogen oxides enter the absorption tower, although they will dissolve in the absorbent and be converted into nitric acid under certain conditions, if the gas entry rate is too fast, some gases may not have enough time to dissolve and will exist in the form of bubbles. When nitrogen oxides and other gases exist in the form of bubbles, their contact area with the absorbent is relatively small, which hinders the dissolution and reaction process of the gas in the absorption tower and reduces the efficiency of nitrogen oxides to nitric acid. Gases that could have been quickly absorbed through sufficient contact cannot effectively interact with the absorbent due to the encapsulation of bubbles. This results in some nitrogen oxides not being absorbed and converted in time, and the gas discharged from the top of the tower still containing a large amount of nitrogen oxides, making the separation of nitrogen oxides impure. Summary of the Invention

[0004] The purpose of this invention is to provide a nitric acid absorption tower and purification method to solve the problem that existing absorption towers cannot break up the bubbles in the tower, resulting in insufficient dissolution and reaction of nitrogen dioxide in the bubbles, and the gas discharged from the top of the tower still contains a large amount of nitrogen oxides, resulting in impure separation of nitrogen oxides.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A nitric acid absorption tower includes a tower body with multiple sieve plates inside, dividing the tower body into multiple absorption layers and a liquid accumulation layer. The liquid accumulation layer is located below all absorption layers. A liquid inlet is provided on the surface of the tower body, which connects to the uppermost absorption layer. Multiple first conveying pipes for connecting adjacent absorption layers are installed on the surface of the tower body. The upper opening of the first conveying pipe is a liquid inlet, and the lower opening of the first conveying pipe is a liquid outlet. Each absorption layer is provided with a grid plate for breaking up air bubbles.

[0007] Preferably, a connecting block is fixedly connected to the top of each grid plate, and a linkage plate is rotatably connected to the top of the connecting block. A rotating shaft is fixedly connected to the surface of the linkage plate, and the rotating shaft is rotatably connected to the tower wall. The liquid flowing out of the inlet and the outlet of the first delivery pipe can be directed toward the surface of the linkage plate located on the rotating shaft.

[0008] Preferably, a first gear is rotatably connected to the inlet and the outlet of each first delivery pipe. The diameter of the first gear is larger than the opening of the inlet and the outlet of the first delivery pipe. A spray nozzle is provided on the surface of each first gear, through which the liquid flowing out of the outlet enters the tower body. The linkage plate in each absorption layer is located to the side of the first gear, and the size of the linkage plate is larger than the size of the first gear.

[0009] Preferably, a fixing rod is fixedly connected to the inner wall of each absorption layer, a movable block is fixedly connected to the bottom end of each fixing rod, a movable channel for relative movement of the movable block is provided on the surface of each grid plate, and a limit support plate is fixedly connected to the bottom end of each movable block through the surface of the grid plate.

[0010] Preferably, a liquid accumulation plate is provided inside the liquid accumulation layer, which divides the liquid accumulation layer into an upper liquid accumulation layer and a lower liquid accumulation layer. Gas in the lower liquid accumulation layer can pass through the upper liquid accumulation layer. A second conveying pipe for connecting the upper and lower liquid accumulation layers is installed on the surface of the tower body. The upper and lower openings of the second conveying pipe are configured the same as those of the first conveying pipe.

[0011] Preferably, a protective cover is fixedly connected to the bottom wall of the lower liquid accumulation layer, and a rotating cylinder is rotatably connected inside the protective cover. The liquid flowing out of the outlet of the second conveying pipe flows into the rotating cylinder, and an overflow port is provided at the top of the protective cover.

[0012] Preferably, a diffuser is fixedly connected to the top of the protective cover, the diffuser is located directly above the overflow port, and the top surface of the protective cover is configured as a guide surface that slopes downward to the left.

[0013] Preferably, an isolation cover is fixedly connected to the surface of the protective cover, and the isolation cover is fixedly connected to the inner wall of the tower body. The isolation cover is used to isolate the nitric acid solution overflowing from the protective cover. A drain port is provided on the left side of the tower body, and the drain port communicates with the internal space of the isolation cover.

[0014] Preferably, the bottom of the tower body has a disassembly hole for removing the rotating cylinder, and an installation plate is movably installed in the disassembly hole. The installation plate is detachably connected to the tower body.

[0015] A method for purifying nitric acid, using the aforementioned nitric acid absorption tower, comprises the following steps:

[0016] A. Waste gas is introduced from the upper liquid layer, and absorbent is introduced from the inlet. When the liquid in each absorption layer flows to the next absorption layer, it passes through the spray nozzle and is sprayed onto the surface of the linkage plate, which drives the linkage plate to rotate around the rotating shaft. The rotation of the linkage plate pulls one end of the grid plate to move obliquely upward, so that the grid plate moves and breaks the bubbles formed in the solution.

[0017] B. Control the rotation of the first gear to make the spray nozzle on the first gear make circular motion, so that the position of the liquid ejected from the spray nozzle hitting the linkage plate changes continuously, and the amplitude of the linkage plate rotation changes continuously.

[0018] C. The nitric acid solution is formed and flows through the second conveying pipe into the rotating cylinder inside the protective cover. The rotating cylinder is controlled to rotate, causing the liquid inside the rotating cylinder to rotate. This causes small bubbles in the solution to move upwards in the rotating cylinder and be broken by colliding with the top wall of the protective cover, causing gas to emerge from the overflow port and merge with the waste gas introduced from the upper liquid layer.

[0019] D. When excess nitric acid solution overflows from the overflow port in the rotating drum, it flows along the surface of the guide surface into the isolation hood, and then is discharged from the drain port.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. By moving the grid plate, the grid of the grid plate cuts and breaks the air bubbles during the movement, which helps to prevent the nitrogen dioxide in the air bubbles from not being fully dissolved and reacted, so that the nitrogen oxides in the incoming waste gas are fully separated, which helps to improve the purity of nitrogen oxide separation.

[0022] 2. By setting the infusion port and the outlet of the first delivery pipe to spray the liquid out onto the upper end of the linkage plate, the linkage plate is pushed to rotate around the rotating shaft, so that the upper end of the linkage plate rotates to the lower left and the lower end rotates to the upper right. The rotation of the linkage plate drives the connecting block to pull the grid plate, so that the grid plate moves. This is beneficial to use the power of the liquid flow to move the grid plate, which helps to reduce the difficulty of realizing the grid plate movement.

[0023] 3. The rotation of the first gear causes the spray nozzle on the first gear to make a circular motion, which makes the position of the liquid flowing out of the spray nozzle constantly change, thus the position of the liquid hitting the linkage plate constantly changes, which changes the force point of the linkage plate, and thus the amplitude of the linkage plate rotation constantly changes, so that the grid plate moves continuously to break the bubbles.

[0024] 4. By setting up a second delivery pipe, the reacted liquid flows into the rotating cylinder. The rotation of the rotating cylinder drives the liquid inside to rotate. Since the small bubbles in the solution have a density much smaller than that of nitric acid solution, they will move to the upper part of the rotating cylinder under the action of centrifugal force. Then the bubbles collide with the top wall of the protective cover and break, and the gas comes out from the overflow port. The gas continues to pass through the absorption layer to separate nitrogen oxides, which helps to improve the purity of nitrogen oxide separation. Attached Figure Description

[0025] Figure 1 This is a front sectional view of the present invention;

[0026] Figure 2 For the present invention Figure 1 Enlarged view of point A in the middle;

[0027] Figure 3 For the present invention Figure 1 Enlarged view of point B in the middle;

[0028] Figure 4 This is a schematic diagram of a partial vertical section of the tower body of the present invention;

[0029] Figure 5 For the present invention Figure 4 Enlarged view of point C in the middle;

[0030] Figure 6 For the present invention Figure 4 Enlarged view of point D in the middle;

[0031] Figure 7 This is a schematic diagram of the structure of the fixing rod of the present invention;

[0032] Figure 8 This is a schematic diagram of the linkage plate of the present invention;

[0033] Figure 9 This is a schematic diagram of the structure of the first gear of the present invention;

[0034] Figure 10 This is a schematic diagram of the vertical section of the protective cover of the present invention;

[0035] Figure 11 This is a schematic diagram of the vertical section of the rotating cylinder of the present invention.

[0036] In the diagram: 1. Tower body; 2. Inlet; 3. First gear; 4. Spray nozzle; 5. Second gear; 6. First motor; 7. Grid plate; 8. Connecting block; 9. Linkage plate; 10. Rotating shaft; 11. Fixed rod; 12. Movable block; 13. Movable channel; 14. Limiting support plate; 15. First conveying pipe; 16. Sieve plate; 17. Connecting pipe; 18. Connecting hole; 19. Protective cover; 20. Overflow port; 21. Guide surface; 22. Diffuser horn; 23. Isolation cover; 24. Rotating cylinder; 25. Rotating shaft; 26. Mounting plate; 27. Embedded groove; 28. Sliding groove; 29. ​​Fixed insert; 30. Second motor; 31. Disassembly hole; 32. Gas inlet; 33. Drain port; 34. Second conveying pipe; 35. Liquid collection plate. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figures 1 to 11 The present invention provides a technical solution:

[0039] A nitric acid absorption tower includes a tower body 1, with an outlet at the top of the tower body 1. The interior of the tower body 1 is provided with multiple sieve plates 16, which divide the tower body 1 into multiple absorption layers and a liquid accumulation layer. The liquid accumulation layer is located below all the absorption layers. The surface of the tower body 1 is provided with a liquid inlet 2, which is connected to the uppermost absorption layer.

[0040] The surface of the tower body 1 is equipped with multiple first conveying pipes 15 for connecting two adjacent absorption layers. The upper opening of the first conveying pipe 15 is the liquid inlet, and the lower opening of the first conveying pipe 15 is the liquid outlet.

[0041] Each absorption layer is equipped with a grid plate 7 for breaking bubbles. By moving the grid plate 7, the grid of the grid plate 7 cuts and breaks the bubbles during the movement, causing the bubbles to break. Furthermore, each grid has a pointed cone on its inner ring, making the bubbles easier to break. This helps to prevent the nitrogen dioxide in the bubbles from not being fully dissolved and reacted, so that the nitrogen oxides in the introduced waste gas are fully separated, which helps to improve the purity of nitrogen oxide separation.

[0042] Each grid plate 7 has a connecting block 8 fixedly connected to its top. A linkage plate 9 is rotatably connected to the top of the connecting block 8. A rotating shaft 10 is fixedly connected to the surface of the linkage plate 9. The rotating shaft 10 is rotatably connected to the wall of the tower body 1. Liquid flowing from the inlet 2 and the outlet of the first delivery pipe 15 can be sprayed onto the surface of the linkage plate 9 located on the upper part of the rotating shaft 10. According to the lever principle, the liquid flowing from the inlet 2 and the outlet of the first delivery pipe 15 sprays onto the upper end of the linkage plate 9, thus pushing the linkage plate 9 to rotate around the rotating shaft 10. Please refer to [reference needed]. Figure 6 The outflowing liquid hits the upper end of the linkage plate 9. The upper end of the linkage plate 9 rotates to the lower left, and the lower end of the linkage plate 9 rotates to the upper right. The rotation of the linkage plate 9 drives the connecting block 8 to pull the grid plate 7, making the grid plate 7 move. This is beneficial to utilizing the power of the liquid flow to make the grid plate 7 move, which helps to reduce the difficulty of making the grid plate 7 move.

[0043] Each inlet 2 is rotatably connected to a first gear 3 at the outlet of each first delivery pipe 15. The diameter of each first gear 3 is larger than the opening of the inlet 2 and the outlet of the first delivery pipe 15, ensuring that the first gear 3 can cover the opening of the inlet 2 and the outlet of the first delivery pipe 15. Each first gear 3 has a spray nozzle 4 on its surface, through which the liquid flowing from the outlet enters the tower body 1. Each linkage plate 9 in each absorption layer is located to the side of the first gear 3. The size of the linkage plate 9 is larger than the size of the first gear 3, ensuring that the liquid flowing from the spray nozzle 4 can hit the surface of the linkage plate 9. When the liquid flowing from the spray nozzle 4 hits the surface of the linkage plate 9, it will... The linkage plate 9 rotates around the rotating shaft 10. Simultaneously, the linkage plate 9 rotates with the connecting block 8, causing the connecting block 8 to move diagonally upwards. This movement of the connecting block 8 pulls the grid plate 7 diagonally upwards, making the grid plate 7 movable. The movement of the grid plate 7 breaks the bubbles rising from below. Through the rotation of the first gear 3, the spray nozzle 4 on the first gear 3 makes a circular motion, thus constantly changing the position of the liquid flowing from the spray nozzle 4. This causes the position of the liquid hitting the linkage plate 9 to continuously change, altering the force point on the linkage plate 9 and thus constantly changing the amplitude of the rotation of the linkage plate 9. This, in turn, causes the grid plate 7 to continuously move and break the bubbles.

[0044] A first motor 6 is fixedly installed on the surface of the tower body 1. A second gear 5 is coaxially fixedly connected to the output end of the first motor 6. The second gear 5 and the first gear 3 are meshed. By starting the first motor 6, the second gear 5 is driven to rotate. The rotation of the second gear 5 drives the first gear 3 to rotate, thereby controlling the rotation of the first gear 3. The rotational connection of the first gear 3 can adopt conventional techniques known to those skilled in the art, and conventional selections can be made therein. For example, a T-shaped ring is coaxially fixedly connected to the right side of the first gear 3. A T-shaped ring groove for the rotation of the T-shaped ring is opened on the inner wall of the tower body 1.

[0045] Each absorption layer has a fixed rod 11 fixedly connected to its inner wall, and a movable block 12 fixedly connected to the bottom end of each fixed rod 11. Each grid plate 7 has a movable channel 13 for relative movement of the movable block 12. The bottom end of each movable block 12 passes through the surface of the grid plate 7 and is fixedly connected to a limiting support plate 14. By setting the fixed rod 11, movable block 12, and limiting support plate 14, the grid plate 7 can be supported at a certain height, preventing one end of the grid plate 7 from tilting and falling onto the screen plate 16, which would affect the effect of the linkage plate 9 driving the grid plate 7. The movable channel 13 allows the grid plate 7 and the movable block 12 to move relative to each other, so that the setting of the fixed rod 11, movable block 12, and limiting support plate 14 does not affect the movement of the grid plate 7.

[0046] A liquid accumulation plate 35 is installed within the liquid accumulation layer, dividing it into an upper liquid accumulation layer and a lower liquid accumulation layer. Gas from the lower liquid accumulation layer can pass through to the upper liquid accumulation layer. A gas inlet 32 ​​is provided on the surface of the tower body 1, installed at the height of the upper liquid accumulation layer and connected to it. The lower liquid accumulation layer is connected to the gas inlet 32 ​​via an upward pipe. A second conveying pipe 34 is installed on the surface of the tower body 1 to connect the upper and lower liquid accumulation layers. The second conveying pipe 34 is open at both ends. The outlet is configured the same as the first conveying pipe 15. Through the first conveying pipe 15 and the second conveying pipe 34, liquid from the upper layer to the lower layer is conveyed between two adjacent layers. A protective cover 19 is fixedly connected to the bottom wall of the lower liquid accumulation layer. A rotating cylinder 24 is rotatably connected inside the protective cover 19. Liquid flowing from the outlet of the second conveying pipe 34 flows into the rotating cylinder 24. An overflow port 20 is provided at the top of the protective cover 19. The reaction liquid flows into the rotating cylinder 24 through the second conveying pipe 34. The rotating cylinder 24 rotates, causing the liquid inside to rotate. When nitrogen oxides react with the absorbent to form a nitric acid solution, there may still be unreacted nitrogen oxides in the solution. These gases usually exist in the form of small bubbles in the nitric acid solution. When the rotating cylinder 24 rotates, the small bubbles in the solution, because their density is much smaller than that of the nitric acid solution, will move upwards in the rotating cylinder 24 under the action of centrifugal force. Then, the bubbles collide with the top wall of the protective cover 19 and break, and the gas escapes from the overflow port 20, allowing the gas to continue to pass through the absorption layer to separate nitrogen oxides, which helps to improve the purity of nitrogen oxide separation. Furthermore, the top wall of the protective cover 19 is provided with a pointed cone, making it easier for the bubbles in contact with it to be broken. The protective cover 19 is fixedly connected to the connecting pipe 17. The upper surface of the protective cover 19 has a connecting hole 18, which is interconnected with the connecting pipe 17. The wall of the lower liquid accumulation layer is fixedly connected to the connecting pipe 17, which is interconnected with the liquid outlet of the second conveying pipe 34.

[0047] A diffuser horn 22 is fixedly connected to the top of the protective cover 19. The diffuser horn 22 is located directly above the overflow port 20. The top surface of the protective cover 19 is set as a guide surface 21 that slopes downward to the left. Please refer to the rotating shaft 10 in the figure. By setting the guide surface 21, there is a left-facing gap between the diffuser horn 22 and the protective cover 19, so that the nitric acid solution overflowing from the protective cover 19 flows to the left along the surface of the guide surface 21. An isolation cover 23 is fixedly connected to the surface of the protective cover 19. The isolation cover 23 is fixedly connected to the inner wall of the tower body 1, so that the interior of the isolation cover 23 forms an isolation space except for the gap between the diffuser horn 22 and the protective cover 19. The isolation cover 23 is used to isolate the nitric acid solution overflowing from the protective cover 19. A drain port 33 is provided on the left side of the tower body 1. The drain port 33 is connected to the internal space of the isolation cover 23, which helps to prevent the nitric acid solution from contacting the input waste gas and from carrying away some waste gas when the nitric acid solution is discharged.

[0048] The bottom of the tower body 1 has a disassembly hole 31 for removing the rotating cylinder 24. An installation plate 26 is movably installed in the disassembly hole 31. The installation plate 26 is detachably connected to the tower body 1. By setting the installation plate 26 and the disassembly hole 31, when the installation plate 26 is detached from the tower body 1, the rotating cylinder 24 can be removed from the disassembly hole 31. Due to the centrifugal effect of the rotating cylinder 24, the nitric acid solution moves out from the overflow port 20. Impurities will settle at the bottom of the rotating cylinder 24, and the rotating cylinder 24 can be removed for easy cleaning of impurities.

[0049] A rotating shaft 25 is coaxially fixedly connected to the bottom end of the rotating cylinder 24. The rotating shaft 25 moves through the surface of the mounting plate 26. A second motor 30 is fixedly installed at the bottom end of the mounting plate 26. The output end of the second motor 30 is coaxially fixedly connected to the rotating shaft 25. By starting the second motor 30, the rotating shaft 25 is driven to rotate, and the rotation of the rotating shaft 25 drives the rotating cylinder 24 to rotate.

[0050] The surface of the tower body 1 is provided with a sliding groove 28, and a fixed insert 29 is movably inserted into the sliding groove 28. The surface of the mounting plate 26 is provided with an embedding groove 27 for the fixed insert 29 to be embedded, so that the mounting plate 26 can be detachably connected.

[0051] Specifically, the solution is as follows: waste gas is introduced from the gas inlet 32 ​​and absorbent is introduced from the liquid inlet 2. During the contact process, the nitrogen oxides in the waste gas react with the absorbent, are absorbed and converted into nitric acid, and flow downward. During the contact process, the liquid in each absorption layer enters the adjacent absorption layer below through the first delivery pipe 15. When the liquid flowing out from the liquid outlet of the first delivery pipe 15 is sprayed onto the surface of the linkage plate 9 through the liquid spray nozzle 4, it drives the linkage plate 9 to rotate around the rotating shaft 10. The rotation of the linkage plate 9 will also cause it to rotate with the connecting block 8, and cause the connecting block 8 to move obliquely upward. The movement of the connecting block 8 pulls the grid plate 7 to move obliquely upward, so that the grid plate 7 moves. The movement of the grid plate 7 will break the bubbles formed by the gas rising from below and entering the solution.

[0052] At the same time, by starting the first motor 6, the second gear 5 is driven to rotate, and the rotation of the second gear 5 drives the first gear 3 to rotate, so that the spray nozzle 4 on the first gear 3 makes a circular motion, thereby making the position of the liquid ejected from the spray nozzle 4 constantly change, so that the position of the liquid hitting the linkage plate 9 is constantly changing, which changes the force point of the linkage plate 9, and thus the rotation amplitude of the linkage plate 9 is constantly changing, so that the grid plate 7 is constantly moving to break the bubbles.

[0053] Finally, after the liquid reacts with the gas in each absorption layer, nitric acid is formed and accumulates on the liquid accumulation plate 35. Then, it flows through the second delivery pipe 34, through the connecting pipe 17, and from the connecting hole 18 into the rotating cylinder 24 inside the protective cover 19. The second motor 30 is started to drive the rotating shaft 25 to rotate, which in turn drives the rotating cylinder 24 to rotate, causing the liquid inside the rotating cylinder 24 to rotate. Then, the small bubbles in the solution, because their density is much smaller than that of the nitric acid solution, will move to the upper part of the rotating cylinder 24 under the action of centrifugal force. Then, the bubbles collide with the top wall of the protective cover 19 and break. The gas comes out from the overflow port 20, passes through the diffuser 22 and floats to the lower liquid accumulation layer. Then, it flows through the upward pipe and merges with the waste gas input from the gas inlet 32. When the excess nitric acid solution in the rotating cylinder 24 overflows from the overflow port 20, it flows from the gap between the protective cover 19 and the diffuser 22 along the surface of the guide surface 21 into the isolation cover 23, and then is discharged from the drain port 33.

[0054] As needed, the fixing block 29 can be pulled outward to remove it from the embedding groove 27. At this time, the mounting plate 26 can be moved downward to move the rotating cylinder 24 downward, so that the rotating cylinder 24 can be moved out of the tower body 1 from the disassembly hole 31, making it convenient to clean the impurities deposited in the rotating cylinder 24.

[0055] As needed, column 1 can also be used as follows: industrial-grade nitric acid is delivered from the mixing tank through a metering pump, passes through a preheater to an evaporator, and is heated to 110-120°C by 0.6MPa low-pressure saturated steam. After the nitric acid vaporizes, it undergoes gas-liquid phase heat and mass transfer on the surface of the distillation column packing. Various heavy components such as anions and cations are enriched in the evaporator. Various impurities in the liquid nitric acid enriched at the bottom of the evaporator are discharged to the residual liquid tank after being cooled by the preheater through a quantitative discharge method. The distillation column is at atmospheric pressure and the top temperature is about 120°C. The distilled high-purity nitric acid vapor enters column 1 through a pipeline.

[0056] High-purity nitric acid vapor enters from the bottom of tower 1, where the nitric acid is converted from a gaseous state to a liquid state at a temperature of 55-75℃, and finally enters the circulation tank.

[0057] Unliquefied gas in tower 1 is discharged from the top of the tower and enters the tail gas absorption tower through the pipeline. When the liquid level in the circulating tank is 80%, the proportional valve is opened to output nitric acid to the decolorization tower with an output flow rate of 500-2500 kg / h.

[0058] A small amount of nitrogen dioxide in the nitric acid solution is carried away by the air and discharged from the top of the decolorization tower. It then enters the tail gas absorption tower through a pipeline. The colorless and transparent nitric acid solution after decolorization in the decolorization tower flows out from the bottom of the decolorization tower and enters the finished product receiving tank. The nitric acid in the finished product receiving tank is sampled and sent for testing. After passing the test, the nitric acid in the receiving tank is pumped and indirectly cooled by a cooler, so that the nitric acid enters the intermediate finished product tank at 5-30℃.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nitric acid absorption tower, comprising a tower body (1), wherein a plurality of sieve plates (16) are disposed inside the tower body (1), the sieve plates (16) dividing the tower body (1) into a plurality of absorption layers and a liquid accumulation layer, the liquid accumulation layer being located below all absorption layers, and a liquid inlet (2) is disposed on the surface of the tower body (1), the liquid inlet (2) being connected to the uppermost absorption layer, characterized in that: The surface of the tower body (1) is equipped with a plurality of first conveying pipes (15) for connecting two adjacent absorption layers. The upper end opening of the first conveying pipe (15) is the liquid inlet, and the lower end opening of the first conveying pipe (15) is the liquid outlet. Each absorption layer is provided with a grid plate (7) for breaking bubbles.

2. The nitric acid absorption tower according to claim 1, characterized in that, Each of the grid plates (7) is fixedly connected to a connecting block (8) at its top end. The connecting block (8) is rotatably connected to a linkage plate (9). A rotating shaft (10) is fixedly connected to the surface of the linkage plate (9). The rotating shaft (10) is rotatably connected to the wall of the tower body (1). The liquid flowing out of the inlet (2) and the outlet of the first delivery pipe (15) can be directed toward the surface of the linkage plate (9) located on the rotating shaft (10).

3. A nitric acid absorption tower according to claim 2, characterized in that, The infusion port (2) and the outlet of each first delivery pipe (15) are rotatably connected to a first gear (3). The diameter of the first gear (3) is larger than the opening of the infusion port (2) and the outlet of the first delivery pipe (15). Each first gear (3) has a spray nozzle (4) on its surface. The spray nozzle (4) allows the liquid flowing out of the outlet to enter the tower body (1). Each linkage plate (9) in the absorption layer is located on the side of the first gear (3). The size of the linkage plate (9) is larger than the size of the first gear (3).

4. A nitric acid absorption tower according to claim 3, characterized in that, Each of the absorption layers has a fixed rod (11) fixedly connected to its inner wall, and a movable block (12) fixedly connected to the bottom end of each fixed rod (11). Each of the grid plates (7) has a movable channel (13) for relative movement of the movable block (12) and a limit support plate (14) fixedly connected to the bottom end of each movable block (12) through the surface of the grid plate (7).

5. A nitric acid absorption tower according to claim 1, characterized in that, A liquid accumulation plate (35) is provided inside the liquid accumulation layer. The liquid accumulation plate (35) divides the liquid accumulation layer into an upper liquid accumulation layer and a lower liquid accumulation layer. Gas in the lower liquid accumulation layer can pass through the upper liquid accumulation layer. A second conveying pipe (34) for connecting the upper liquid accumulation layer and the lower liquid accumulation layer is installed on the surface of the tower body (1). The upper and lower openings of the second conveying pipe (34) are the same as those of the first conveying pipe (15).

6. A nitric acid absorption tower according to claim 5, characterized in that, A protective cover (19) is fixedly connected to the bottom wall of the lower liquid layer. A rotating cylinder (24) is rotatably connected inside the protective cover (19). The liquid flowing out of the outlet of the second conveying pipe (34) flows into the rotating cylinder (24). An overflow port (20) is opened at the top of the protective cover (19).

7. A nitric acid absorption tower according to claim 6, characterized in that, The top of the protective cover (19) is fixedly connected to a diffuser (22), which is located directly above the overflow port (20). The top surface of the protective cover (19) is configured as a guide surface (21) that slopes downward to the left.

8. A nitric acid absorption tower according to claim 7, characterized in that, An isolation cover (23) is fixedly connected to the surface of the protective cover (19). The isolation cover (23) is fixedly connected to the inner wall of the tower body (1). The isolation cover (23) is used to isolate the nitric acid solution overflowing from the protective cover (19). A drain port (33) is provided on the left side of the tower body (1). The drain port (33) is connected to the internal space of the isolation cover (23).

9. A nitric acid absorption tower according to claim 6, characterized in that, The bottom of the tower body (1) has a disassembly hole (31) for the rotating cylinder (24) to be removed. An installation plate (26) is movably installed in the disassembly hole (31). The installation plate (26) is detachably connected to the tower body (1).

10. A method for purifying nitric acid, characterized in that, The nitric acid absorption tower described in claim 8 is used, and the specific steps are as follows: A. Waste gas is introduced from the upper liquid layer, and absorbent is introduced from the inlet (2). When the liquid in each absorption layer flows to the next absorption layer, it passes through the spray nozzle (4) and is sprayed onto the surface of the linkage plate (9). This causes the linkage plate (9) to rotate around the rotating shaft (10). The rotation of the linkage plate (9) pulls one end of the grid plate (7) to move obliquely upward, so that the grid plate (7) moves and breaks the bubbles formed in the solution. B. Control the first gear (3) to rotate, so that the spray nozzle (4) on the first gear (3) makes circular motion, so that the position of the liquid ejected from the spray nozzle (4) hitting the linkage plate (9) changes continuously, so that the rotation amplitude of the linkage plate (9) changes continuously. C. The nitric acid solution is formed and flows through the second delivery pipe (34) into the rotating cylinder (24) inside the protective cover (19). The rotating cylinder (24) is controlled to rotate, so that the liquid inside the rotating cylinder (24) rotates, causing small bubbles in the solution to move to the upper part of the rotating cylinder (24) and be broken by colliding with the top wall of the protective cover (19), so that the gas comes out from the overflow port (20) and merges with the waste gas introduced from the upper liquid layer; D. When the excess nitric acid solution in the rotating cylinder (24) overflows from the overflow port (20), it flows along the surface of the guide surface (21) into the isolation cover (23), and then is discharged from the drain port (33).

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