Electronic-grade nitric acid preparation device and method for controlling filtering speed based on temperature difference

Abstract

The invention discloses an electronic-grade nitric acid preparation device and method capable of controlling the filtering speed based on temperature difference, and relates to the technical field of nitric acid preparation.The electronic-grade nitric acid preparation device comprises a first-stage rectifying tower and a second-stage rectifying tower, and a first-stage evaporator and a second-stage evaporator are arranged on the outer sides of the bottoms of the first-stage rectifying tower and the second-stage rectifying tower respectively; compared with an existing filtering part, the temperature control assembly is arranged, the temperature control assembly has double functions, on one hand, liquefied nitric acid entering the filter is preheated, and on the other hand, the filtering speed of the filtering assembly on nitric acid is changed according to needs; in addition, a filling disc is accurately rotated through a reversing motor, so that a target material storage cavity is isolated from the rectifying tower main body, and the risk of negative pressure damage or harmful gas leakage in the tower in the traditional dismounting process is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of nitric acid preparation, and in particular to an electronic-grade nitric acid preparation device and method based on temperature difference control of filtration speed. Background Art

[0002] Electronic-grade nitric acid is a high-purity nitric acid, mainly used in the electronics industry as a core chemical for high-end electronic industries such as semiconductor manufacturing and photovoltaic cells. Traditional electronic-grade nitric acid preparation processes usually involve multiple stages of evaporation, rectification, and filtration. The stability of the filtration and evaporation processes directly affects the quality of the final product.

[0003] For example, the patents "CN113353900A An electronic-grade nitric acid preparation device" and "CN116946987A An electronic-grade nitric acid preparation device and its preparation process" respectively disclose a technical solution for the preparation of electronic-grade nitric acid. However, the existing preparation processes still have the following defects in practical applications. First, in the filtration stage, conventional devices lack precise control over the temperature of liquefied nitric acid. When the low-temperature liquefied nitric acid after condensation directly enters the secondary evaporator, it is extremely easy to cause thermal stress shock to the equipment due to excessive temperature difference, which not only shortens the service life of key components but also leads to fluctuations in the evaporation rate. In addition, most existing filters adopt a fixed flow rate design or rely on mechanical speed control devices (such as electric valves). The former cannot meet the requirements of dynamic changes in process parameters, and the latter has a risk of seal failure because the rotating shaft penetrates the container wall, which may cause leakage of nitric acid vapor and pose a safety hazard. Finally, in the process of replacing the packing in the rectification column, the existing technology generally adopts the method of shutting down and disassembling. This process not only destroys the negative pressure environment inside the tower, resulting in the escape of harmful gases, but also consumes a large amount of time due to system restart. Summary of the Invention

[0004] The purpose of the present invention is to provide an electronic-grade nitric acid preparation device and method based on temperature difference control of filtration speed to solve the problems raised in the existing technology.

[0005] To achieve the above purpose, the present invention provides the following technical solution: An electronic-grade nitric acid preparation device based on temperature difference control of filtration speed. The electronic-grade nitric acid preparation device includes a primary rectification column and a secondary rectification column. An evaporator I and an evaporator II are respectively arranged on the outer sides of the bottoms of the primary rectification column and the secondary rectification column. A condenser and a filter are connected between the primary rectification column and the secondary rectification column. An installation seat and a filtering component are arranged inside the filter, and a temperature control component is arranged inside the installation seat. When the present invention works, the nitric acid solution to be purified is pumped out from the raw material tank by a raw material pump and transported into the evaporator I. The evaporator I heats the nitric acid solution to be purified. At this time, the nitric acid solution vaporizes into steam, and the nitric acid steam is transported into the primary rectification column through a pipeline.

[0006] Further, the primary rectification column includes a tower barrel and a base. There are several tower barrels, which are sequentially installed above the base. Inside each tower barrel, there are several groups of packing components. The structure and internal arrangement of the secondary rectification column are the same as those of the primary rectification column. Nitric acid vapor flows upward in the primary rectification column and intercepts impurities such as acid foam and particulate matter in the nitric acid vapor through several groups of packing components. When the nitric acid vapor reaches the top of the primary rectification column, it enters the condenser. The high-boiling-point vapor phase, which is the doped solution, liquefies first in the condenser and then flows back into the primary rectification column. The low-boiling-point vapor phase is the purified nitric acid vapor. After the nitric acid vapor liquefies, it flows into the filter (the functions realized by the condenser belong to conventional technical means in the art, and the specific structure is not described).

[0007] Further, a diversion channel is provided at the middle position of the mounting seat. The diversion channel is connected to the condenser through a liquid inlet pipe. A liquid outlet pipe is provided at the bottom of the filter, and the liquid outlet pipe is connected to the secondary evaporator. The filtering component includes a chassis, two filter meshes, two fixing frames, a preheating rod, and two movable plates. The two fixing frames and the two filter meshes are connected end to end along the circumference of the chassis to form an annular structure. The two movable plates are oppositely arranged outside the two fixing frames. The temperature control component is connected to the preheating rod and the two movable plates. The liquefied nitric acid flows along the liquid inlet pipe, the diversion channel, and the filtering component when entering the filter, intercepts the remaining impurities and crystals in the liquefied nitric acid through the two filter meshes, and the filtered liquefied nitric acid flows into the secondary evaporator along the liquid outlet pipe.

[0008] Further, the temperature control component includes a movable groove, a gas storage tank, a cover plate and an annular turntable. The movable groove, the gas storage tank and the annular turntable are all arranged at the lower end of the mounting seat. The cover plate is arranged below the mounting seat. The annular turntable is connected to the two movable plates. There are bumps on the outer side of the annular turntable. An arc-shaped spring is arranged in the movable groove. An arc-shaped groove is arranged between the movable groove and the gas storage tank. An arc-shaped rod is arranged in the arc-shaped groove. The bumps on the outer side of the annular turntable are connected to the arc-shaped rod and the arc-shaped spring. A first heating element and a second heating element are arranged inside the gas storage tank. The first heating element is connected to the preheating rod through a heat conduction element. Compressed gas is filled below the second heating element. When liquefied nitric acid is filtered in the filter, the staff can supply heat to the preheating rod through the first heating element and the heat conduction element to achieve the purpose of preheating the liquefied nitric acid. When the staff needs to adjust the filtering speed of the filtering component for nitric acid, the second heating element can be turned on to heat the compressed gas in the gas storage tank through the second heating element. At this time, the compressed gas will expand. Under the action of the compressed gas, the arc-shaped rod will push the annular turntable to rotate, drive the two movable plates to rotate synchronously through the annular turntable, increase the flow resistance of the liquefied nitric acid through the two movable plates, and indirectly change the filtering speed of the filtering component for nitric acid. Compared with the current method of controlling the filtering speed by means of a motor, etc., the present invention changes the gas expansion volume by adjusting the heating power to control the filtering speed, which can effectively reduce the mechanical sealing requirements of the rotating components (for example, the motor shaft often needs to pass through the container wall) and reduce the risk of nitric acid volatilization and leakage.

[0009] Further, a second channel is arranged on one side of each filter screen away from the axis of the chassis. A cleaning pipe is arranged below each second channel. A sealing ball is arranged inside each second channel. Each sealing ball is movably installed in the second channel through a first sealing spring.

[0010] Further, a first channel is provided at the middle position of the chassis. A waste pipe is provided below the first channel. An installation groove is provided at the middle position of the first channel. A sealing plate is arranged in the installation groove. A through hole is provided on the sealing plate. The sealing plate is connected to the installation groove through a second sealing spring. One end of the sealing plate away from the second sealing spring is connected to one of the second channels through a push rod. The elastic coefficient of the second sealing spring is smaller than that of the first sealing spring. When liquefied nitric acid is filtered in the filter, the sealing ball is in close contact with the second channel. There is no overlapping area between the through hole on the sealing plate and the first channel. The first channel and the second channel are sealed by the sealing plate and the sealing ball to prevent liquefied nitric acid from leaking. When the work is over, if the staff needs to clean the filter screen in the filter, only need to connect the cleaning pipe to the external cleaning system, connect the waste pipe to the external waste liquid recovery system, and then turn on the temperature control group to make the two movable plates rotate until the two movable plates are aligned with the two filter screens. The filter assembly is separated from the filter through the two movable plates and the two fixing frames. Then the staff can turn on the external cleaning system. Since the elastic coefficient of the second sealing spring is smaller than that of the first sealing spring, when the cleaning liquid enters the second channel, under the action of hydraulic pressure, the second sealing spring will deform first. At this time, the through hole on the sealing plate will overlap with the first channel. When the external cleaning system continues to transport the cleaning liquid into the second channel, the sealing ball will finally disengage from the second channel. Finally, the second channel is in an open state, and the cleaning liquid will enter the area between the movable plate and the filter screen. The filter screen can be rinsed through the cleaning liquid. Finally, the impurities intercepted by the filter screen will enter the external waste liquid recovery system along with the cleaning liquid along the first channel and the waste pipe, so as to facilitate the reuse of the filter later.

[0011] Further, a number of groups of refueling ports are provided on each tower barrel. Each group of refueling ports is aligned with a group of packing components. A group of sealing end caps are detachably installed inside each group of refueling ports.

[0012] Further, the packing component includes an installation frame and a packing tray. The packing tray is arranged inside the installation frame. A number of groups of storage cavities are provided inside the packing tray. A group of support nets are provided at the upper and lower ends of each group of storage cavities. Each group of storage cavities is filled with packing.

[0013] Further, a first opening is provided at one end of the mounting frame close to the charging port. Two groups of partitions are provided at one end of the mounting frame close to the first opening inside. The packing tray is located between the two groups of partitions. A second opening is provided at one end of each storage cavity close to the inner wall of the mounting frame. A sealing cover is provided on one of the partitions. A reversing motor is provided inside the sealing cover. The working end of the reversing motor is connected to the packing tray. When nitric acid vapor flows in the primary rectification column, the particulate matter and acid foam in the nitric acid vapor are intercepted by the packing in the storage cavity. When the staff needs to replace the packing in a certain storage cavity, just start the reversing motor. The reversing motor can drive the packing tray to rotate in the mounting frame. When the storage cavity with the packing to be replaced moves between the two groups of partitions, the storage cavity with the packing to be replaced can be separated from the primary rectification column by the two groups of partitions. At this time, the staff can first remove the sealing end cover from the charging port, and then use a suction pump to pump out the residual nitric acid vapor in the storage cavity with the packing to be replaced. Then the staff can directly clean the storage cavity with the packing to be replaced and send new packing into the cleaned storage cavity. Compared with the current packing assembly, the present invention accurately rotates the packing tray through the reversing motor to isolate the target storage cavity from the main body of the rectification column, avoiding the risk of negative pressure damage or harmful gas leakage in the tower during the traditional disassembly process. Each storage cavity adopts a standardized packing module, which on the one hand improves the rate of packing replacement, and on the other hand enables the present invention to replace the packing without shutting down the machine when the packing has problems.

[0014] A preparation method used in an electronic-grade nitric acid preparation device based on temperature difference control of the filtration rate includes the following steps: S1: The nitric acid raw material is transported to the primary evaporator by a raw material pump. The generated vapor-phase nitric acid is transported to the primary rectification column through a pipeline. The particulate matter and other impurities in the vapor-phase nitric acid are intercepted by the packing assembly provided inside the primary rectification column. S2: The rectified nitric acid vapor is cooled and liquefied by a condenser. The liquefied nitric acid passes through a filter for secondary filtration and enters the secondary evaporator. S3: The nitric acid is reheated by the secondary evaporator. After the nitric acid becomes vapor-phase, it enters the secondary rectification column through a pipeline. The particulate matter and other impurities in the vapor-phase nitric acid are intercepted by the packing assembly provided inside the secondary rectification column. S4: The nitric acid vapor after secondary rectification is transported to the subsequent absorption tower treatment process through a pipeline.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. Compared with the current filter component, the present invention is provided with a temperature control component, which has a dual function. On the one hand, it makes the preheating rod generate heat, which can preheat the liquefied nitric acid entering the filter, avoiding the direct entry of the low-temperature liquefied nitric acid after condensation into the secondary evaporator, which may cause thermal shock to the equipment, affect the service life and stability of the equipment, and enable the liquefied nitric acid to quickly reach the evaporation state after entering the secondary evaporator. On the other hand, the temperature control component can also control the rotation of two movable plates, thereby increasing the flow resistance of the liquefied nitric acid as needed, indirectly changing the filtration speed of the filter component for nitric acid, preventing the too-fast flow of the liquefied nitric acid from causing instability in the evaporation process in the secondary evaporator, affecting the evaporation effect of nitric acid, and reducing the purification efficiency and quality of nitric acid; 2. The present invention can achieve the purpose of automatically cleaning the filter component through the mutual cooperation of the temperature control component and the filter component. When the liquefied nitric acid is filtered in the filter, the first channel and the second channel are sealed by the sealing plate and the sealing ball, effectively avoiding the leakage of the liquefied nitric acid. When it is necessary to clean the filter screen inside the filter component after the work is completed, only need to connect the cleaning pipe to the external cleaning system and the waste pipe to the external waste liquid recovery system, and then turn on the temperature control component, then the cleaning liquid transported by the external cleaning system can wash the filter screen, and the impurities intercepted by the filter screen will enter the external waste liquid recovery system along with the cleaning liquid through the first channel and the waste pipe. This operation method can quickly and effectively clean the filter screen, facilitate the reuse of the subsequent filter, reduce the downtime of the equipment, and improve the production efficiency; 3. Compared with the current packing component, the present invention accurately rotates the packing disc through a reversing motor to isolate the target storage cavity from the main body of the rectification tower, avoiding the risk of negative pressure damage or harmful gas leakage in the tower during the traditional disassembly process. In addition, each storage cavity adopts a standardized packing module, which on the one hand improves the rate of replacing the packing, and on the other hand enables the present invention to replace the packing without shutting down the machine when there is a problem with the packing, further improving the production efficiency and ensuring the continuity of production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall structure of the present invention; Figure 2 is a schematic diagram of the internal structure of the filter of the present invention; Figure 3 is a schematic diagram of the structure of the filter component of the present invention; Figure 4 is a schematic diagram of the internal structure of the mounting seat of the present invention; Figure 5 is a schematic diagram of the structure of the temperature control component of the present invention; Figure 6 is a schematic diagram of the internal structure of the chassis of the present invention; Figure 7Schematic diagram of the position of the packing component of the present invention; Figure 8 Schematic diagram of the structure of the packing component of the present invention; Figure 9 Schematic diagram of the structure of the mounting bracket of the present invention; Figure 10 Schematic diagram of the structure of the packing tray of the present invention.

[0017] In the figure: 1, primary evaporator; 2, primary rectification column; 21, tower barrel; 211, refueling port; 212, mounting bracket; 2121, partition board; 213, sealing cover; 214, packing tray; 2141, storage cavity; 2142, support net; 22, base; 3, condenser; 4, filter; 41, liquid inlet pipe; 42, mounting seat; 421, first heating element; 422, second heating element; 423, gas storage tank; 424, cover plate; 425, annular turntable; 426, arc rod; 43, liquid outlet pipe; 44, waste pipe; 45, cleaning pipe; 46, filtering component; 461, chassis; 4611, first channel; 4612, sealing plate; 4613, sealing ball; 4614, second channel; 4615, mounting groove; 462, filter screen; 463, fixing frame; 464, preheating rod; 465, movable plate; 5, secondary evaporator; 6, secondary rectification column. Detailed implementation manners

[0018] Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0019] Embodiment: As Figures 1 - 10 shown, the present invention provides a technical solution, an electronic-grade nitric acid preparation device based on temperature difference control of the filtration rate. The electronic-grade nitric acid preparation device includes a primary rectification column 2 and a secondary rectification column 6. A primary evaporator 1 and a secondary evaporator 5 are respectively arranged on the outer sides of the bottoms of the primary rectification column 2 and the secondary rectification column 6. A condenser 3 and a filter 4 are connected between the primary rectification column 2 and the secondary rectification column 6. A mounting seat 42 and a filtering component 46 are arranged inside the filter 4. A temperature control component is arranged inside the mounting seat 42. When the present invention works, the nitric acid solution to be purified is pumped out from the raw material tank by a raw material pump and conveyed into the primary evaporator 1. The primary evaporator 1 heats the nitric acid solution to be purified. At this time, the nitric acid solution vaporizes into steam, and the nitric acid steam is conveyed into the primary rectification column 2 through a pipeline.

[0020] As Figure 1 、 Figure 7As shown, the primary rectification column 2 includes a column barrel 21 and a base 22. There are several column barrels 21, and the several column barrels 21 are successively installed above the base 22. Inside each column barrel 21, there are several groups of packing components. The structure of the secondary rectification column 6 and its internal settings are the same as those of the primary rectification column 2 and its internal structure.

[0021] The nitric acid vapor flows upward in the primary rectification column 2, and impurities such as acid foam and particulate matter in the nitric acid vapor are intercepted by several groups of packing components. When the nitric acid vapor reaches the top of the primary rectification column 2, it will enter the condenser 3. The high-boiling-point vapor phase is the doped solution, which is first liquefied in the condenser 3 and then refluxed into the primary rectification column 2. The low-boiling-point vapor phase is the purified nitric acid vapor. After the nitric acid vapor is liquefied, it will flow into the filter 4 (the functions realized by the condenser 3 belong to the conventional technical means in the field, and the specific structure will not be described).

[0022] As Figures 2 - 6 As shown, a diversion channel is provided at the middle position of the mounting seat 42. The diversion channel is connected to the condenser 3 through a liquid inlet pipe 41. The bottom of the filter 4 is provided with a liquid outlet pipe 43, and the liquid outlet pipe 43 is connected to the secondary evaporator 5. The filter assembly 46 includes a chassis 461, two filter meshes 462, two fixing frames 463, a preheating rod 464, and two movable plates 465. The two fixing frames 463 and the two filter meshes 462 are connected end to end along the circumference of the chassis 461 to form an annular structure. The two movable plates 465 are relatively arranged outside the two fixing frames 463. The temperature control assembly is connected to the preheating rod 464 and the two movable plates 465.

[0023] When the liquefied nitric acid enters the filter 4, it flows along the liquid inlet pipe 41, the diversion channel, and the filter assembly 46. The residual impurities and crystals in the liquefied nitric acid are intercepted by the two filter meshes 462. The filtered liquefied nitric acid flows along the liquid outlet pipe 43 into the secondary evaporator 5. Compared with the current filtering components, the present invention is provided with a temperature control assembly. On the one hand, the temperature control assembly makes the preheating rod 464 generate heat, thereby preheating the liquefied nitric acid so that the liquefied nitric acid can quickly reach the evaporation state after entering the secondary evaporator 5, avoiding the thermal shock to the equipment caused by the direct entry of low-temperature nitric acid into the secondary evaporator 5. On the other hand, the temperature control assembly can also control the rotation of the two movable plates 465. By the two movable plates 465, the flow resistance of the liquefied nitric acid can be increased, thereby indirectly changing the filtering speed of the filter assembly 46 for nitric acid, ensuring that the condensed nitric acid can smoothly enter the secondary evaporation stage and avoiding too fast filtering speed, which affects the evaporation effect of the condensed nitric acid by the subsequent secondary evaporator 5.

[0024] As Figures 2 - 6As shown in the figure, the temperature control component includes a movable groove, a gas storage tank 423, a cover plate 424, and an annular turntable 425. The movable groove, the gas storage tank 423, and the annular turntable 425 are all arranged at the lower end of the mounting seat 42. The cover plate 424 is arranged below the mounting seat 42. The annular turntable 425 is connected to two movable plates 465. There are bumps on the outer side of the annular turntable 425. An arc-shaped spring is arranged in the movable groove. An arc-shaped groove is arranged between the movable groove and the gas storage tank 423. An arc-shaped rod 426 is arranged in the arc-shaped groove. The bumps on the outer side of the annular turntable 425 are connected to the arc-shaped rod 426 and the arc-shaped spring. A first heating element 421 and a second heating element 422 are arranged inside the gas storage tank 423. The first heating element 421 is connected to the preheating rod 464 through a heat conducting element. Compressed gas is filled below the second heating element 422.

[0025] When the liquefied nitric acid is filtered in the filter 4, the staff can supply heat to the preheating rod 464 through the first heating element 421 and the heat conducting element, so as to achieve the purpose of preheating the liquefied nitric acid. When the staff needs to adjust the filtering speed of the filtering component 46 for nitric acid, the second heating element 422 can be turned on to heat the compressed gas in the gas storage tank 423 through the second heating element 422. At this time, the compressed gas will expand. Under the action of the compressed gas, the arc-shaped rod 426 will push the annular turntable 425 to rotate, drive the two movable plates 465 to rotate synchronously through the annular turntable 425, increase the flow resistance of the liquefied nitric acid through the two movable plates 465, and then indirectly change the filtering speed of the filtering component 46 for nitric acid. Compared with the current method of controlling the filtering speed by means of a motor, etc., the present invention controls the filtering speed by adjusting the heating power to change the expansion volume of the gas, which can effectively reduce the mechanical sealing requirements of the rotating parts (for example, the motor shaft often needs to pass through the container wall), and reduce the risk of nitric acid volatilization and leakage.

[0026] As Figure 6 shown in the figure, a second channel 4614 is arranged on one side of each filter screen 462 away from the axis of the chassis 461. A cleaning pipe 45 is arranged below each second channel 4614. A sealing ball 4613 is arranged inside each second channel 4614. Each sealing ball 4613 is movably installed in the second channel 4614 through a first sealing spring.

[0027] As Figure 6As shown, a first channel 4611 is provided at the middle position of the chassis 461, a waste pipe 44 is provided below the first channel 4611, a mounting groove 4615 is provided at the middle position of the first channel 4611, a sealing plate 4612 is provided in the mounting groove 4615, a through hole is provided on the sealing plate 4612, the sealing plate 4612 and the mounting groove 4615 are connected by a second sealing spring, one end of the sealing plate 4612 away from the second sealing spring is connected to one of the second channels 4614 through a push rod, and the elastic coefficient of the second sealing spring is smaller than that of the first sealing spring.

[0028] When the liquefied nitric acid is filtered in the filter 4, the sealing ball 4613 is in close contact with the second channel 4614, and there is no overlapping area between the through hole on the sealing plate 4612 and the first channel 4611. The first channel 4611 and the second channel 4614 are sealed by the sealing plate 4612 and the sealing ball 4613 to prevent leakage of the liquefied nitric acid. When the work is completed, if the staff needs to clean the filter screen 462 in the filter 4, they only need to connect the cleaning pipe 45 to the external cleaning system, connect the waste pipe 44 to the external waste liquid recovery system, and then turn on the temperature control group to rotate the two movable plates 465 until the two movable plates 465 are aligned with the two filter screens 462, and separate the filter assembly 46 from the filter 4 through the two movable plates 465 and the two fixed frames 463. Then the staff The staff can turn on the external cleaning system. Since the elastic coefficient of the second sealing spring is smaller than that of the first sealing spring, when the cleaning liquid enters the second channel 4614, the second sealing spring will be deformed first under the action of hydraulic pressure. At this time, the through hole on the sealing plate 4612 will overlap with the first channel 4611. When the external cleaning system continues to transport cleaning liquid into the second channel 4614, the sealing ball 4613 will eventually detach from the second channel 4614. Finally, the second channel 4614 is in an open state, and the cleaning liquid will enter the area between the movable plate 465 and the filter screen 462. The filter screen 462 can be rinsed with the cleaning liquid. Finally, the impurities retained by the filter screen 462 will enter the external waste liquid recovery system along the first channel 4611 and the waste pipe 44 with the cleaning liquid, so as to facilitate the subsequent reuse of the filter 4.

[0029] like Figure 1 , Figure 7 As shown, each tower 21 is provided with a plurality of groups of material changing ports 211 , each group of material changing ports 211 is aligned with a group of packing components, and a group of sealing end covers are detachably installed inside each group of material changing ports 211 .

[0030] like Figure 1 , Figures 7 - 10As shown in the figure, the packing assembly includes a mounting frame 212 and a packing tray 214. The packing tray 214 is arranged inside the mounting frame 212. A number of groups of material storage cavities 2141 are arranged inside the packing tray 214. A group of support meshes 2142 are arranged at both the upper and lower ends of each group of material storage cavities 2141. Each group of material storage cavities 2141 is filled with packing material.

[0031] As Figure 1 , Figures 7 - 10 shown in the figure, one end of the mounting frame 212 close to the material changing port 211 is provided with a first opening. Two groups of partition plates 2121 are arranged at one end inside the mounting frame 212 close to the first opening. The packing tray 214 is located between the two groups of partition plates 2121. A group of second openings are arranged at one end of each group of material storage cavities 2141 close to the inner wall of the mounting frame 212. A sealing cover 213 is arranged on one of the partition plates 2121. A reversing motor is arranged inside the sealing cover 213. The working end of the reversing motor is connected to the packing tray 214.

[0032] When nitric acid vapor flows in the primary distillation column 2, particulate matter and acid foam in the nitric acid vapor are intercepted by the packing material in the material storage cavity 2141. When the staff needs to replace the packing material in a certain group of material storage cavities 2141, only need to start the reversing motor. The reversing motor can drive the packing tray 214 to rotate in the mounting frame 212. When the material storage cavity 2141 with the packing material to be replaced moves between the two groups of partition plates 2121, the two groups of partition plates 2121 can separate the material storage cavity 2141 with the packing material to be replaced from the primary distillation column 2. At this time, the staff can first remove the sealing end cover from the material changing port 211, and then use a suction pump to pump away the residual nitric acid vapor inside the material storage cavity 2141 with the packing material to be replaced. Then the staff can directly clean the material storage cavity 2141 with the packing material to be replaced and send new packing material into the cleaned material storage cavity 2141. Compared with the current packing assembly, in the present invention, the reversing motor precisely rotates the packing tray 214 to isolate the target material storage cavity 2141 from the main body of the distillation column, avoiding the risk of negative pressure damage or harmful gas leakage in the tower during the traditional disassembly process. Each material storage cavity 2141 adopts a standardized packing module, which improves the rate of replacing the packing material on the one hand, and enables the present invention to replace the packing material without stopping the machine when problems are found with the packing material on the other hand.

[0033] A preparation method used in an electronic-grade nitric acid preparation device based on temperature difference control of the filtration rate includes the following steps: S1: The nitric acid raw material is transported to the primary evaporator 1 by a raw material pump. The generated vapor-phase nitric acid is transported to the primary distillation column 2 through a pipeline. Particulate matter and other impurities in the vapor-phase nitric acid are intercepted by the packing assembly arranged inside the primary distillation column 2. S2: The distilled nitric acid vapor is cooled and liquefied by the condenser 3. The liquefied nitric acid is secondarily filtered by the filter 4 and enters the secondary evaporator 5. S3: The nitric acid is reheated by the secondary evaporator 5. After the nitric acid becomes vapor, it enters the secondary rectifying column 6 through a pipeline. The particulate matters and other impurities in the vapor-phase nitric acid are intercepted by the packing assembly arranged inside the secondary rectifying column 6. S4: The nitric acid vapor after secondary rectification is transported through a pipeline to the subsequent absorption tower treatment process.

[0034] The working principle of the present invention: The nitric acid solution to be purified is pumped out from the raw material tank by the raw material pump and transported into the primary evaporator 1. The primary evaporator 1 heats the nitric acid solution to be purified. At this time, the nitric acid solution vaporizes into steam. The nitric acid steam is transported to the primary rectifying column 2 through a pipeline. When the nitric acid steam flows inside the primary rectifying column 2, the particulate matters and acid foam in the nitric acid steam are intercepted by the packing in the storage cavity 2141. When the staff needs to replace the packing in a certain storage cavity 2141 inside the packing assembly, the reversing motor can be started to isolate the target storage cavity 2141 from the main body of the primary rectifying column 2. Then the staff can first remove the sealing end cover from the material replacement port 211, and use the air extraction pump to extract the residual nitric acid steam inside the target storage cavity 2141. Then directly clean the storage cavity 2141 where the packing to be replaced is located, and send the new packing into the cleaned storage cavity 2141. When the nitric acid steam reaches the top of the primary rectifying column 2, it will enter the condenser 3. The high-boiling-point vapor-phase doped solution is first liquefied in the condenser 3 and flows back to the primary rectifying column 2. The low-boiling-point vapor-phase is the purified nitric acid steam. After the nitric acid steam is liquefied, it will flow into the filter 4 and flow along the liquid inlet pipe 41, the diversion channel, and the filter assembly 46. The residual impurities and crystallized substances in the liquefied nitric acid are intercepted by the filter assembly 46. The temperature control assembly controls the filtering speed of the filter assembly 46 for nitric acid to ensure that the condensed nitric acid can smoothly enter the secondary evaporation stage and avoid a too fast filtering speed, which may affect the evaporation effect of the condensed nitric acid by the subsequent secondary evaporator 5. When the filtered liquefied nitric acid is reheated in the secondary evaporator 5, the nitric acid steam will enter the secondary rectifying column 6 through a pipeline. The particulate matters and other impurities in the vapor-phase nitric acid are intercepted by the packing assembly arranged inside the secondary rectifying column 6. The nitric acid steam after secondary rectification is transported through a pipeline to the subsequent absorption tower treatment process.

[0035] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electronic grade nitric acid preparation device based on temperature difference control filtration speed, characterized in that: The electronic grade nitric acid preparation device comprises a primary distillation tower (2) and a secondary distillation tower (6), wherein a primary evaporator (1) and a secondary evaporator (5) are respectively arranged on the outer sides of the bottoms of the primary distillation tower (2) and the secondary distillation tower (6), wherein a condenser (3) and a filter (4) are connected between the primary distillation tower (2) and the secondary distillation tower (6), wherein a mounting seat (42) and a filter assembly (46) are arranged inside the filter (4), and a temperature control assembly is arranged inside the mounting seat (42), wherein the condensed nitric acid is preheated by the temperature control assembly and the filtering speed of the filter assembly (46) is controlled.

2. A device for preparing electronic-grade nitric acid based on temperature difference control of filtration speed according to claim 1, characterized in that: The primary distillation tower (2) comprises a tower barrel (21) and a base (22), wherein a plurality of tower barrels (21) are provided, and the plurality of tower barrels (21) are sequentially installed above the base (22), and a plurality of groups of packing components are provided inside each tower barrel (21). The structure and internal arrangement of the secondary distillation tower (6) are the same as those of the primary distillation tower (2).

3. A device for preparing electronic-grade nitric acid based on temperature difference control of filtration speed according to claim 1, characterized in that: The filter assembly (46) comprises a chassis (461), two filter screens (462), two fixed frames (463), a preheating rod (464) and two movable plates (465); the two fixed frames (463) and the two filter screens (462) are connected end to end along the circumference of the chassis (461) to form an annular structure; the two movable plates (465) are arranged on the outside of the two fixed frames (463) relative to each other; and the temperature control assembly is connected to the preheating rod (464) and the two movable plates (465).

4. A device for preparing electronic-grade nitric acid based on temperature difference control of filtration speed according to claim 3, characterized in that: The temperature control assembly comprises a movable groove, an air storage groove (423), a cover plate (424) and an annular turntable (425); the movable groove, the air storage groove (423) and the annular turntable (425) are all arranged at the lower end of the mounting seat (42); the cover plate (424) is arranged below the mounting seat (42); the annular turntable (425) is connected to two movable plates (465); a protrusion is arranged on the outer side of the annular turntable (425); an arc spring is arranged in the movable groove; An arc groove is provided between the groove and the gas storage groove (423), an arc rod (426) is provided in the arc groove, a convex block on the outer side of the annular turntable (425) is connected to the arc rod (426) and the arc spring, a first heating element (421) and a second heating element (422) are provided inside the gas storage groove (423), the first heating element (421) is connected to the preheating rod (464) via a heat conducting element, and the lower part of the second heating element (422) is filled with compressed gas.

5. The electronic grade nitric acid preparation device based on temperature difference control filtration speed according to claim 3, characterized in that: A second channel (4614) is provided on a side of each filter screen (462) away from the axis of the chassis (461), a cleaning pipe (45) is provided below each second channel (4614), a sealing ball (4613) is provided inside each second channel (4614), and each sealing ball (4613) is movably installed in the second channel (4614) via a first sealing spring.

6. The electronic grade nitric acid preparation device based on temperature difference control filtration speed according to claim 5, characterized in that: A first channel (4611) is provided at a middle position of the chassis (461), a waste pipe (44) is provided below the first channel (4611), a mounting groove (4615) is provided at a middle position of the first channel (4611), a sealing plate (4612) is provided in the mounting groove (4615), a through hole is provided on the sealing plate (4612), the sealing plate (4612) and the mounting groove (4615) are connected via a second sealing spring, and one end of the sealing plate (4612) away from the second sealing spring is connected to one of the second channels (4614) via a push rod.

7. The electronic grade nitric acid preparation device based on temperature difference control filtration speed according to claim 2, characterized in that: Each tower barrel (21) is provided with a plurality of groups of material exchange ports (211), each group of material exchange ports (211) is aligned with a group of filler components, and a group of sealing end covers are detachably installed inside each group of material exchange ports (211).

8. The electronic grade nitric acid preparation device based on temperature difference control filtration speed according to claim 7, characterized in that: The filler assembly comprises a mounting frame (212) and a filler plate (214); the filler plate (214) is arranged inside the mounting frame (212); a plurality of groups of material storage cavities (2141) are arranged inside the filler plate (214); and a group of support nets (2142) are arranged at the upper and lower ends of each group of material storage cavities (2141).

9. The electronic grade nitric acid preparation device based on temperature difference control filtration speed according to claim 8, characterized in that: A first opening is provided at one end of the mounting frame (212) close to the material exchange port (211); two groups of partition plates (2121) are provided at one end of the mounting frame (212) close to the first opening; the filling plate (214) is located between the two groups of partition plates (2121); a group of second openings is provided at one end of each group of material storage cavities (2141) close to the inner wall of the mounting frame (212); a sealing cover (213) is provided on one group of partition plates (2121); a reversing motor is provided in the sealing cover (213); and a working end of the reversing motor is connected to the filling plate (214).

10. A method for preparing electronic-grade nitric acid using a device for preparing electronic-grade nitric acid based on temperature difference-controlled filtration speed according to claim 2, characterized in that: The steps include: S1: The nitric acid raw material is transported to the primary evaporator (1) by a raw material pump, and the generated vapor phase nitric acid is transported to the primary distillation tower (2) via a pipeline, and impurities such as particulate matter in the vapor phase nitric acid are intercepted by a packing component arranged inside the primary distillation tower (2); S2: The nitric acid vapor after distillation is cooled and liquefied through a condenser (3), and the liquefied nitric acid is filtered twice through a filter (4) and enters a secondary evaporator (5); S3: reheating the nitric acid through the secondary evaporator (5), and the nitric acid vapor phase enters the secondary distillation tower (6) through the pipeline, and the impurities such as particulate matter in the vapor phase nitric acid are intercepted by the packing component arranged inside the secondary distillation tower (6); S4: The nitric acid vapor from the secondary distillation is transported through pipelines to the subsequent absorption tower treatment process.

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