A purification system and method for carbon tetrafluoride

Abstract

This invention relates to the technical field of gas purification, and particularly to a carbon tetrafluoride purification system and method. The purification system includes a precooling unit, a low-boiling-point column, and a high-boiling-point column. Both the low-boiling-point and high-boiling-point columns have arrayed packing layers inside, with distribution plates between the packing layers. The distribution plates have arrayed telescopic mass transfer sections. The tops of the low-boiling-point and high-boiling-point columns are respectively equipped with low-boiling-point condensers and high-boiling-point condensers. After condensation, the refrigerant from both columns is introduced into the telescopic mass transfer section through an inlet pipe and then discharged through an outlet pipe. A booster fan is installed on the inlet pipe, and a regulating valve is installed on the outlet pipe. This invention uses a flow meter to detect the gas discharge and liquid reflux rates of the distillation column, and calculates the reflux ratio change accordingly. By adjusting the operating power of the booster fan and the opening size of the regulating valve, the amount of refrigerant introduced into the telescopic mass transfer section can be controlled, thereby adjusting the height of the top of the telescopic mass transfer section.

Description

Technical Field

[0001] This invention relates to the technical field of gas purification, and in particular to a carbon tetrafluoride purification system and method. Background Technology

[0002] Carbon tetrafluoride, with the chemical formula CF4, is colorless and non-flammable at room temperature. It is chemically very stable and exhibits strong inertness. Under normal pressure, it needs to be heated to 800°C to begin thermal decomposition.

[0003] Carbon tetrafluoride (CF4) is an important plasma etching gas in the microelectronics industry, primarily used for plasma etching and cleaning processes in various integrated circuits. Currently, the mainstream method for preparing CF4 in the domestic and international chemical industries is the direct synthesis of fluorocarbons. However, the purity of CF4 produced using this method depends mainly on the product yield in the fluorocarbon reaction stage and the effectiveness of impurity removal in the purification stage.

[0004] Chinese patent application CN202223613020.5 discloses a carbon tetrafluoride distillation purification system. The cryogenic distillation system is coupled to a refrigeration cycle system via the top condensers of the heavy distillation column and the light distillation column, and is coupled to a heat exchanger-powered refrigerant circulation heating system via a heat exchanger box. The fluorine production unit is sequentially connected to a fluorocarbon reactor, a pyrolysis unit, a purification unit, a first buffer tank, a process compressor, a first adsorption column, a second adsorption column, a cryogenic filter, a heavy distillation column, a third adsorption column, and a light distillation column. The bottom of the heavy distillation column is connected between the fluorine production unit and the fluorocarbon reactor. The heating medium of the reboiler in the heavy distillation column is connected to the heat exchanger box via a refrigerant circulation pump. The bottom of the light distillation column is also connected to the heat exchanger box via a refrigerant circulation pump. The top pipeline of the light distillation column is connected to two gas separation membranes and then to the first buffer tank. This purification system is energy-saving and environmentally friendly.

[0005] Although the aforementioned patent documents address the issues of high energy consumption and low equipment utilization in existing distillation methods for recovering hexafluoroethane, packed columns are still widely used as the mainstream separation device in practical applications for the distillation purification of carbon tetrafluoride crude gas. However, the purity of the product obtained through packed columns is extremely sensitive to dynamic changes in the gas-liquid reflux ratio. Current technologies primarily rely on two types of operations to control reflux ratio fluctuations: adjusting the amount of product collected from the top of the column or adjusting the operating parameters of the condensation system. It should be noted that these control methods exhibit significant response lag, which makes it difficult for the system to synchronize with transient changes in the reflux ratio, thus hindering the dynamic optimization of the mass transfer state between the gas and liquid phases, i.e., contact time and interface renewal rate. This, in turn, leads to a decrease in the distillation efficiency of the packed column. Summary of the Invention

[0006] The purpose of this invention is to provide a carbon tetrafluoride purification system and purification method to solve the technical problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A carbon tetrafluoride purification system, comprising:

[0009] In the precooling unit, the raw material gas and the refrigerant nitrogen exchange heat to achieve partial liquefaction of the raw material gas;

[0010] Low-boiling column, used to precipitate impurities below the boiling point of carbon tetrafluoride to obtain a primary separation solution;

[0011] High-boiling-point column, used to separate impurities with boiling points higher than those of the original liquid in the primary separation, to obtain high-purity carbon tetrafluoride;

[0012] Both the low-boiling-point tower and the high-boiling-point tower are equipped with arrayed packing layers inside, and distribution disks are provided between the packing layers. The distribution disks are equipped with arrayed telescopic mass transfer sections, and the gas and liquid phases undergo contact mass transfer in the top area of ​​the telescopic mass transfer section.

[0013] The top of the low-boiling tower and the high-boiling tower are respectively equipped with a low-boiling condenser and a high-boiling condenser. After the refrigerant in both towers completes the condensation operation, it is introduced into the expansion mass transfer section through the inlet pipe and then discharged through the outlet pipe.

[0014] The inlet pipe is equipped with a booster fan, and the outlet pipe is equipped with a regulating valve. By adjusting the operating power of the booster fan and the opening size of the regulating valve, the amount of refrigerant entering the telescopic mass transfer section can be controlled, thereby adjusting the height of the top of the telescopic mass transfer section.

[0015] Preferably, the telescopic mass transfer section includes:

[0016] The fixing component is located on the top of the distribution plate and has a pushing chamber inside;

[0017] The air inlet and air outlet are located at the bottom of the fixed part and are connected to the push chamber. The refrigerant enters and exits the push chamber through the air inlet and air outlet.

[0018] The movable component is located inside the push chamber and is connected to the fixed component through an elastic part. One end of the movable component extending out of the push chamber is provided with a mass transfer groove, where the gas and liquid phases make contact and transfer mass.

[0019] Preferably, the end of the movable component extending out of the pushing chamber is provided with a top cover. When the movable component retracts to its limit, the top cover abuts against the top of the fixed component to achieve the cessation of liquid flow.

[0020] The top cover has an exhaust section inside, and when the top cover comes into contact with the fixing member, the gas phase can enter the upper space of the distribution plate from the exhaust section.

[0021] Preferably, the exhaust section includes:

[0022] The airways are arranged in an array inside the top cover;

[0023] The movable frame is slidably connected to the top cover and has a vent.

[0024] When the movable frame is in the first state, the vent and the airway are misaligned, and the movable frame blocks the air outlet of the airway; when the movable frame is in the second state, the vent and the airway are aligned, and the movable frame releases the blockage of the airway.

[0025] Preferably, the fixing member is further provided with a traction chamber, the top of the traction chamber is provided with a drain hole, the bottom of the traction chamber is provided with a drainage hole, and a drainage part is provided at the drainage hole, the drainage part being used to block the drainage hole.

[0026] Preferably, the drain section includes:

[0027] The sealing element is located inside the traction chamber and is connected to the fixing element through an elastic element;

[0028] The traction component has one end connected to the sealing component and the other end connected to the movable frame;

[0029] When the sealing member is in the first state, the sealing member blocks the drain hole; when the sealing member is in the second state, the sealing member releases the blockage of the drain hole.

[0030] Preferably, the sealing member has a notch, which facilitates the liquid phase to enter the area below the distribution plate through the drain hole.

[0031] Preferably, the moving part includes a first section and a second section, and the mass transfer tank is located in the second section;

[0032] The moving parts on the same distribution plate have the same height in the first section, while the heights of the second section are distributed in a staggered manner.

[0033] Preferably, both the gas phase outlet and the liquid phase reflux outlet of the low-boiling condenser and the high-boiling condenser are equipped with flow meters;

[0034] Each of the distribution plates is equipped with a level gauge in the area above it.

[0035] A purification process for carbon tetrafluoride, the purification process comprising the following steps:

[0036] Step 1: Pre-cooling of raw material gas: Carbon tetrafluoride raw material enters the pre-cooling unit and exchanges heat with nitrogen refrigerant to lower the temperature of the raw material gas to the dew point, thereby achieving partial liquefaction of the raw material gas.

[0037] Step 2, Low-boiling column distillation: The partially liquefied feed gas is distilled in the middle of the low-boiling column. The low-boiling column precipitates impurities with a boiling point lower than that of carbon tetrafluoride, and the primary separated raw liquid is obtained.

[0038] Step 3, High-boiling column distillation: The primary separation liquid is further distilled in the high-boiling column. The high-boiling column separates impurities of carbon tetrafluoride that are higher than the boiling point of the primary separation liquid, and obtains high-purity carbon tetrafluoride.

[0039] Step 4: Reflux ratio monitoring and control: The gas discharge rate and liquid reflux rate of the distillation column are detected by a flow meter, and the change in the reflux ratio of the distillation column is calculated accordingly. The extension of the expansion and contraction mass transfer section is dynamically adjusted according to the change in the reflux ratio to adapt to the operating conditions of the distillation column.

[0040] The technical effects and advantages of this invention are as follows:

[0041] This invention maintains the stability of the gas-liquid mass transfer interface within the distillation column by dynamically adjusting the height of the moving parts, effectively solving the problems of flooding and foam entrainment. When an abnormal reflux ratio causes the liquid level in the distribution plate to deviate from the set range, the amount of refrigerant supplied to the pushing chamber of the telescopic mass transfer section is changed by adjusting the power of the booster fan and the opening of the regulating valve, thereby controlling the raising and lowering of the moving parts to adjust the height of the mass transfer tank. This avoids flooding caused by the liquid phase submerging the mass transfer tank when the liquid level is too high, and foam entrainment in the gas phase when the liquid level is too low. Furthermore, under long-term abnormal operating conditions, the synergistic effect of the moving and fixed parts enables forced liquid phase discharge or gas phase fractional mass transfer, further enhancing the system's adaptability to complex operating conditions. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the main process of Embodiment 1 of the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of the low-boiling tower and the high-boiling tower of the present invention;

[0044] Figure 3 This is a schematic diagram of the main process of Embodiment 2 of the present invention;

[0045] Figure 4 This is a schematic diagram of the distribution disk structure of the present invention;

[0046] Figure 5 This is a schematic diagram of the structure of the telescopic mass transfer section of the present invention;

[0047] Figure 6 This is a schematic diagram of the internal structure of the telescopic mass transfer section of the present invention;

[0048] Figure 7This is a schematic diagram of the cross-sectional structure of the telescopic mass transfer section of the present invention;

[0049] Figure 8 This is a schematic diagram of the structure of the discharge section of the present invention;

[0050] Figure 9 This is a schematic diagram of the exhaust section of the present invention;

[0051] Figure 10 This is a schematic diagram illustrating the height differences of movable components on the same distribution plate of the present invention;

[0052] Figure 11 This is a schematic diagram illustrating the state differences of the moving parts on the same distribution disk as they move downwards according to the present invention.

[0053] In the picture:

[0054] 100. Precooling unit;

[0055] 200. Receiving tank;

[0056] 300, Low-boiling reboiler; 400, Low-boiling tower; 500, Low-boiling condenser;

[0057] 600, High-boiling-point reboiler; 700, High-boiling-point tower; 800, High-boiling-point condenser;

[0058] 900. Cold box;

[0059] 1. Distribution disk;

[0060] 2. Telescopic mass transfer section; 201. Fixed component; 202. Moving component; 203. Mass transfer groove; 204. Pushing chamber; 205. Elastic part;

[0061] 3. Top cover;

[0062] 4. Exhaust section; 401. Air passage; 402. Movable frame; 403. Vent;

[0063] 5. Traction chamber;

[0064] 6. Drainage hole;

[0065] 7. Drainage hole;

[0066] 8. Drainage section; 801. Sealing component; 802. Notch; 803. Traction component; 804. Elastic component;

[0067] 9. Booster fan;

[0068] 10. Control valve;

[0069] 11. Air intake;

[0070] 12. Air vent. Detailed Implementation

[0071] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0072] Example 1

[0073] Reference Figures 1 to 2 As shown, the present invention provides a carbon tetrafluoride purification system, comprising:

[0074] In the precooling unit 100, the raw material gas and the refrigerant nitrogen gas exchange heat to achieve partial liquefaction of the raw material gas.

[0075] The low-boiling column 400 is used to precipitate impurities below the boiling point of carbon tetrafluoride to obtain a primary separation solution.

[0076] The high-boiling column 700 is used to separate impurities with boiling points higher than those of the original liquid in the primary separation process, to obtain high-purity carbon tetrafluoride.

[0077] Both the low-boiling tower 400 and the high-boiling tower 700 are equipped with arrayed packing layers inside, and distribution disks 1 are provided between the packing layers. Arrayed telescopic mass transfer sections 2 are provided on the distribution disks 1, and the gas and liquid phases undergo contact mass transfer in the top area of ​​the telescopic mass transfer section 2.

[0078] The top of the low-boiling tower 400 and the high-boiling tower 700 are respectively equipped with a low-boiling condenser 500 and a high-boiling condenser 800; the top of the low-boiling tower 400 and the high-boiling tower 700 are respectively equipped with a low-boiling reboiler 300 and a high-boiling reboiler 600.

[0079] During operation, the raw material, carbon tetrafluoride (impure CF4), first enters the precooling unit 100. In the precooling unit 100, the raw material gas exchanges heat with the refrigerant nitrogen, lowering its temperature to the dew point of -65°C, thus partially liquefying the raw material gas. Subsequently, the partially liquefied raw material gas is sent into the cold box 900.

[0080] After partially liquefied feed gas enters the cold box 900, it first enters the feed precooling receiving tank 200, and then is transported to the middle of the low-boiling column 400 for rectification. The liquid feed gas accumulates in the low-boiling reboiler 300, while the gaseous feed gas rises along the column body of the low-boiling column 400 to the top. In the low-boiling reboiler 300, the liquefied feed liquid exchanges heat with the heat transfer medium Freon, causing a large amount of light components (N2, O2) in the feed liquid to evaporate and rise along the column body of the low-boiling column 400 to the top. At this time, the gas at the top of the low-boiling column 400 is passed into the low-boiling condenser 500, where it exchanges heat with the refrigerant liquid nitrogen. The higher-boiling-point gas (CF4) reverts from a gaseous state to a liquid state and flows back into the low-boiling column 400; while the lower-boiling-point impurities (N2, O2) remain in a gaseous state and are discharged from the column. In the low-boiling column 400, the rising gaseous phase and the returning liquid phase undergo mass and heat transfer, achieving sufficient contact. After multiple condensation and evaporation processes, low-boiling-point impurities are discharged from the tower, while substances with higher boiling points (CF4) accumulate in the low-boiling reboiler 300.

[0081] Next, the feed liquid accumulated in the low-boiling reboiler 300 is fed into the high-boiling column 700 for further distillation. The distillation principle in the high-boiling column 700 is similar to that in the low-boiling column 400: the feed liquid in the high-boiling reboiler 600 exchanges heat with the heat medium, and most of the light components (CF4) are evaporated and rise to the top of the high-boiling column 700. Then, these gases are fed into the high-boiling condenser 800 for heat exchange with liquid nitrogen. The higher-boiling-point impurities are recondensed into liquid and returned to the high-boiling column 700, where they undergo mass and heat transfer with the rising gaseous phase, ensuring full contact. In the high-boiling column 700, after multiple condensation and evaporation processes, the lower-boiling-point CF4 is separated and supplied to the user; while the higher-boiling-point impurities return to the high-boiling reboiler 600 and are eventually discharged from the column.

[0082] Example 2

[0083] While the above embodiments can achieve carbon tetrafluoride purification, in practical applications, distillation columns primarily achieve mixture separation through countercurrent gas-liquid contact. The core mechanism relies on the boiling point differences of the components to form progressively concentrated light and heavy components within the column. The reflux ratio is a key parameter for adjusting separation efficiency. Abnormal changes in the reflux ratio can lead to imbalances in the gas-liquid flow within the column, resulting in operational malfunctions such as flooding and foam entrainment, severely impacting product quality and equipment safety. Therefore, based on Embodiment 1, a technical improvement is made, as shown below:

[0084] Reference Figures 1 to 9As shown, the present invention provides a carbon tetrafluoride purification system. Both the low-boiling tower 400 and the high-boiling tower 700 are provided with arrayed packing layers. A distribution disk 1 is provided between the packing layers. An array of telescoping mass transfer sections 2 are provided on the distribution disk 1. The gas and liquid phases are in contact and mass transfer in the top region of the telescoping mass transfer section 2.

[0085] The top of the low-boiling tower 400 and the high-boiling tower 700 are respectively equipped with a low-boiling condenser 500 and a high-boiling condenser 800. After the refrigerant of the two towers completes the condensation operation, it is introduced into the telescopic mass transfer section 2 through the input pipe and then discharged through the output pipe.

[0086] The input pipe is equipped with a booster fan 9, and the output pipe is equipped with a regulating valve 10. By adjusting the operating power of the booster fan 9 and the opening size of the regulating valve 10, the amount of refrigerant entering the telescopic mass transfer section 2 can be controlled, thereby adjusting the top height of the telescopic mass transfer section 2.

[0087] Specifically, the telescopic mass transfer unit 2 includes a fixed member 201 disposed on the top of the distribution plate 1. The fixed member 201 has a pushing chamber 204 inside, and a movable member 202 is disposed inside the pushing chamber 204. The movable member 202 is connected to the fixed member 201 via an elastic part 205. A mass transfer groove 203 is provided at one end of the movable member 202 extending out of the pushing chamber 204, where the gas and liquid phases undergo mass transfer. Both the fixed member 201 and the movable member 202 are annular, and the gas phase moves towards the top of the tower through the annular space.

[0088] The liquid phase flows downward from the top of the tower and gradually accumulates on the distribution plate 1. When the liquid level in the distribution plate 1 rises to the position of the mass transfer tank 203, the liquid phase will flow through the mass transfer tank 203 into the annular space formed by the fixed component 201 and the moving component 202, where it will come into contact with the gas phase for mass transfer.

[0089] The bottom of the fixing component 201 is provided with an air inlet 11 and an air outlet 12. The air inlet 11 and the air outlet 12 are connected to the push chamber 204. The refrigerant enters and exits the push chamber 204 through the air inlet 11 and the air outlet 12.

[0090] The movable part 202 extends out of the pushing chamber 204 and is provided with a top cover 3, which is conical.

[0091] Both the low-boiling condenser 500 and the high-boiling condenser 800 are equipped with flow meters at their gas phase outlet and liquid phase reflux outlet. The flow meter at the gas phase outlet is used to detect the amount of gas discharged, and the flow meter at the liquid phase reflux outlet is used to detect the amount of liquid returned.

[0092] The reflux ratio change between the low-boiling condenser 500 and the high-boiling condenser 800 can be calculated using the reflux formula:

[0093]

[0094] Where L is the liquid return flow rate; D is the gas discharge rate.

[0095] In use, the elongation of the telescoping mass transfer section 2 is dynamically adjusted by calculating the reflux ratio between the low-boiling condenser 500 and the high-boiling condenser 800, thereby avoiding technical problems such as flooding or foam entrainment.

[0096] Specifically:

[0097] When the gas phase is introduced into the condenser, it exchanges heat with the refrigerant (liquid nitrogen) in the condenser. The gas phase with a higher boiling point changes from a gaseous state back to a liquid state and flows back into the distillation column through the liquid phase reflux port. Meanwhile, the impurities with a lower boiling point remain in a gaseous state and are discharged from the column through the gas phase outlet. During this process, the flow meter installed at the gas phase outlet detects the amount of gas discharged per unit time. The flow meter installed at the liquid phase reflux port detects the amount of liquid reflux per unit time, and the change in the reflux ratio between the low-boiling condenser 500 and the high-boiling condenser 800 is calculated using the reflux formula.

[0098] After heat exchange, the liquid nitrogen in the condenser is converted into nitrogen gas. The nitrogen gas is introduced into the pushing chamber 204 of each fixed component 201 through the input pipe. By controlling the amount of nitrogen gas introduced into the pushing chamber 204, a thrust can be generated on the moving component 202 in the pushing chamber 204, thereby adjusting the extension and retraction of the telescopic mass transfer section 2.

[0099] Taking the low-boiling tower 400 as an example, the specific steps for adjusting the expansion and contraction of the expansion and contraction of the expansion and contraction mass transfer section 2 are as follows:

[0100] When the control system detects that the reflux ratio of the current low-boiling tower 400 is greater than the set value, it indicates that the carbon tetrafluoride crude gas introduced into the low-boiling tower 400 has high purity (few impurities with low boiling points). This causes the flow meter at the gas phase outlet to measure a decrease in the gas discharge rate per unit time, while the flow meter at the liquid phase reflux outlet measures an increase in the liquid reflux rate per unit time, ultimately making the reflux ratio of the current low-boiling tower 400 greater than the set value.

[0101] When the liquid reflux rate increases, the liquid level in the distribution plate 1 will rise synchronously. At this time, when the gas and liquid phases are in contact for mass transfer, there is a risk of flooding. When the control system detects that the reflux ratio of the low-boiling tower 400 is greater than the set value, the difference between the current reflux ratio of the low-boiling tower 400 and the set value will cause the opening of the regulating valve 10 on the control output pipe to decrease, and the power of the booster fan 9 on the input pipe to increase. This will increase the amount of nitrogen gas entering the pushing chamber 204, thereby increasing the thrust of the nitrogen gas on the moving part 202. The nitrogen gas will push the moving part 202 to move further upward, thereby raising the height of the mass transfer tank 203. While ensuring gas-liquid mass transfer, the gas needs to overcome the hydrostatic pressure of the liquid column to pass through after the liquid phase floods the telescopic mass transfer section 2, resulting in a surge in the total pressure drop of the system.

[0102] When the control system detects that the reflux ratio of the current low-boiling tower 400 is lower than the set value, it indicates that the carbon tetrafluoride crude gas introduced into the low-boiling tower 400 contains a high content of impurities (especially impurities with low boiling points). This causes the flow meter at the gas phase outlet to measure an increase in the gas discharge rate per unit time, while the flow meter at the liquid phase reflux outlet measures a decrease in the liquid reflux rate per unit time, ultimately resulting in the current reflux ratio of the low-boiling tower 400 being lower than the set value.

[0103] When the liquid reflux rate decreases, the liquid level in the distribution plate 1 will decrease synchronously. At this time, when the gas and liquid phases are in contact mass transfer, there is a risk of foam entrainment. Therefore, when the control system detects that the reflux ratio of the low-boiling tower 400 is lower than the set value, the difference between the current reflux ratio of the low-boiling tower 400 and the set value will cause the opening of the regulating valve 10 of the control output pipe to increase, and the power of the booster fan 9 on the input pipe to decrease. This reduces the amount of nitrogen gas entering the pushing chamber 204, and the thrust of the nitrogen gas on the moving part 202 decreases. At this time, under the elastic recovery capability of the elastic element 804, the elastic element 804 drives the moving part 202 to move down, so that the height of the mass transfer tank 203 decreases. That is, the liquid level on the distribution plate 1 does not need to rise to the set height to be in contact mass transfer with the gas phase.

[0104] Example 3

[0105] While the above embodiments can mitigate flooding and foam entrainment in the distillation column to some extent, in practical applications, if the reflux ratio changes and remains in this state for a long period, simply raising or lowering the height of the mass transfer tank 203 can only mitigate the problem and cannot ensure that the mass transfer state of the gas and liquid phases at the distribution plate 1 remains at the set state. Therefore, based on Embodiment 2, a technical improvement is made, and the improved technical solution is as follows:

[0106] Reference Figures 1 to 11 As shown, the present invention provides a carbon tetrafluoride purification system. The movable part 202 extends out of the pushing chamber 204 and is provided with a top cover 3. When the movable part 202 retracts to its limit value, the top cover 3 abuts against the top of the fixed part 201 to achieve the stop flow of the liquid phase.

[0107] The top cover 3 has an exhaust section 4 inside. When the top cover 3 comes into contact with the fixing member 201, the gas phase can enter the upper space of the distribution plate 1 from the exhaust section 4.

[0108] Specifically, the exhaust section 4 includes an air passage 401 formed inside the top cover 3, and the air passages 401 are arranged in an array inside the top cover 3. The air passages 401 are preferably straight or curved.

[0109] A movable frame 402 is slidably connected to the outer side of the top cover 3. The movable frame 402 is provided with a vent 403. When the movable frame 402 is in the first state, the vent 403 and the air passage 401 are misaligned, and the movable frame 402 blocks the air outlet of the air passage 401. When the movable frame 402 is in the second state, the vent 403 and the air passage 401 are aligned, and the movable frame 402 releases the blockage of the air passage 401.

[0110] The movable frame 402 includes an annular plate disposed above the top cover 3 and a pressure ring disposed below the top cover 3. The annular plate and the pressure ring are directly provided with an array of sliding plates. The sliding plates are slidably connected to the top cover 3, and the vent 403 is located on the sliding plate.

[0111] Specifically, the fastener 201 is also provided with a traction chamber 5 inside, a drain hole 6 is provided at the top of the traction chamber 5, a drain hole 7 is provided at the bottom of the traction chamber 5, and a drain part 8 is provided at the drain hole 7, which is used to block the drain hole 7.

[0112] Specifically, the discharge section 8 includes a sealing member 801 disposed inside the traction chamber 5, and the sealing member 801 is connected to the fixing member 201 through an elastic member 804.

[0113] When the sealing member 801 is in the first state, the sealing member 801 blocks the drain hole 7; when the sealing member 801 is in the second state, the sealing member 801 releases the blockage of the drain hole 7. The sealing member 801 includes an annular block disposed inside the traction chamber 5, and the annular block is provided with a blocking block corresponding to the drain hole 7.

[0114] A traction component 803 is provided between the sealing component 801 and the movable frame 402. The traction component 803 includes a traction rope or a telescopic rod, and its main purpose is to pull the sealing component 801.

[0115] Specifically, the sealing component 801 has a notch 802, which allows the liquid phase to enter the area below the distribution plate 1 through the drain hole 7. The notch 802 is located on the ring block.

[0116] Specifically, the moving part 202 includes a first section and a second section, and the mass transfer tank 203 is located in the second section.

[0117] The movable parts 202 on the same distribution plate 1 have the same height in the first section, and the height of the second section is distributed in a staggered manner.

[0118] To ensure effective mass transfer between the gas and liquid phases, the liquid phase flowing out of the mass transfer tank 203 needs to be stable. However, when the reflux ratio exceeds a set value and remains in this state for an extended period, simply increasing the height of the mass transfer tank 203 only provides a buffering effect. The amount of liquid phase falling onto the distribution plate 1 is still greater than the discharge from the mass transfer tank 203. When the mass transfer tank 203 reaches its highest point, if the liquid level on the distribution plate 1 continues to rise, without corresponding technical measures, the liquid phase will eventually flood the mass transfer tank 203, leading to flooding. Therefore, this embodiment proposes a technical solution based on Embodiment 2. The specific solution is as follows:

[0119] When the reflux ratio is greater than the set value and remains in this state for a long time, it indicates that the liquid level on the distribution plate 1 is gradually rising. At this time, based on the second embodiment, the control system further controls the opening of the regulating valve 10 of the output pipe to decrease and the power of the booster fan 9 on the input pipe to increase the amount of nitrogen gas entering the pushing chamber 204, thereby increasing the thrust of the nitrogen gas on the moving part 202. The nitrogen gas pushes the moving part 202 upward, thereby raising the height of the mass transfer tank 203. At this time, when the moving part 202 moves upward, the top cover 3 pulls the sealing part 801 through the movable frame 402 and the traction part 803, so that the sealing part 801 gradually releases the blocking state of the drain hole 7. At this time, part of the liquid phase on the distribution plate 1 enters the pulling chamber 5 through the drain hole 6 and flows directly to the lower area of ​​the distribution plate 1 through the notch 802 and the drain hole 7, thereby reducing the liquid phase on the distribution plate 1 and avoiding the problem of continuous rise in the liquid level on the distribution plate 1 due to the reflux ratio being greater than the set value for a long time, which could lead to flooding.

[0120] When the reflux ratio is less than the set value and remains in this state for a long time, simply lowering the height of the mass transfer tank 203 can only serve as a buffer. The amount of liquid phase falling onto the distribution plate 1 is still less than the discharge rate of the mass transfer tank 203. However, when the mass transfer tank 203 drops to its highest point, if the liquid level on the distribution plate 1 continues to decrease, without corresponding technical measures, the technical problem of foam entrainment will eventually occur. Therefore, this embodiment proposes a technical solution based on Embodiment 2. The specific solution is as follows:

[0121] When the reflux ratio is less than the set value and remains in this state for a long time, it indicates that the liquid level on the distribution plate 1 is continuously decreasing. At this time, based on the second embodiment, the control system further controls the opening of the regulating valve 10 of the output pipe to increase and the power of the booster fan 9 on the input pipe to decrease, so that the amount of nitrogen gas introduced into the push chamber 204 decreases and the thrust of nitrogen gas on the moving part 202 decreases. At this time, under the elastic recovery capability of the elastic part 804, the elastic part 804 drives the moving part 202 to move down, so that the height of the mass transfer tank 203 decreases.

[0122] In this embodiment, the movable parts 202 on the same distribution plate 1 have the same height in the first section, while the heights of their second sections are staggered. The mass transfer groove 203 is located in the second section. That is, when the elastic element 804 moves the movable part 202 downwards, some of the movable parts 202 will have their top cover 3 abut against the top of the fixed element 201 during the downward movement. During this process, the top of the fixed element 201 presses against the movable frame 402, causing it to move upwards. Even when the movable frame 402 is in the second state, the vent 403 and the air passage 401 are aligned, and the movable frame 402 releases the blockage of the air passage 401. Specifically, as shown... Figure 11 As shown.

[0123] At this time, because the top cover 3 on part of the moving part 202 abuts against the fixed part 201, it effectively blocks part of the mass transfer tank 203, preventing the liquid phase from entering the lower area of ​​the distribution plate 1 through the mass transfer tank 203 of this part of the moving part 202. This reduces the water output of the distribution plate 1, thus alleviating the problem of the continuous drop in liquid level on the distribution plate 1. At the same time, because the moving frame 402 releases the blockage of the air passage 401, the gas phase can enter the upper space of the distribution plate 1 through the air passage 401. The air outlet 12 of the air passage 401 is located on the periphery of the top cover 3, that is, in the upper area of ​​the liquid phase. The pressure of the liquid phase does not exceed the pressure of the gas phase, so the gas phase can be discharged from the air outlet 12 of the air passage 401. When the gas phase discharged from the air outlet 12 of the air passage 401 is discharged, it can still undergo contact mass transfer with the liquid phase.

[0124] It should be noted that in this embodiment, a bend can be provided at the air outlet 12 of the air passage 401. The outlet of the bend is located below the liquid level of the liquid phase, and the bending point of the bend is located above the liquid level of the liquid phase, so that the gas phase can contact and transfer mass with the deep liquid phase, and the liquid phase will not enter the air passage 401.

[0125] It should be noted that in this embodiment, the heights of the mass transfer channels 203 of the moving parts 202 on the same distribution disk 1 are not the same, but the bottom heights of the mass transfer channels 203 are at the same horizontal line.

[0126] Example 4

[0127] While the above embodiments can avoid flooding and foam entrainment caused by the reflux ratio being in an unset state for a long time, the internal working state of the distillation column is quite complex in actual applications. Simply adjusting the operating parameters of the booster fan 9 and the regulating valve 10 to solve the problems of flooding and foam entrainment is too arbitrary, and it is impossible to correct the actual required operating parameters based on feedback information before and after the adjustment. Therefore, a technical improvement is made based on Embodiment 3, and the improved technical solution is as follows:

[0128] This invention provides a carbon tetrafluoride purification system, wherein flow meters are installed at both the gas phase outlet and the liquid phase reflux outlet of the low-boiling condenser 500 and the high-boiling condenser 800. A level gauge is installed in the area above the distribution plate 1.

[0129] By installing flow meters at the gas phase outlet and liquid phase reflux outlet of the low-boiling condenser 500 and the high-boiling condenser 800, the reflux ratio of the distillation column can be obtained based on the ratio of the two flow meters. The operating parameters of the booster fan 9 and the regulating valve 10 can be dynamically adjusted based on the reflux ratio to avoid technical problems such as flooding and foam entrainment in the distillation column.

[0130] A level gauge is installed in the area above the distribution plate 1 to monitor the changes in the liquid level on the distribution plate 1 in real time. The data collected in real time by the level gauge is used as feedback information to adjust the working parameters of the booster fan 9 and the regulating valve 10 as required.

[0131] When the control system detects that the current reflux ratio of the low-boiling tower 400 is greater than or less than the set value, the control system, after detecting the liquid level information on the current distribution plate 1 by the liquid level gauge, predicts the subsequent liquid level change through the model, and then adjusts the height of the moving part 202 through the regulating valve 10 and the booster fan 9 to avoid technical problems such as flooding or foam entrainment.

[0132] The purpose of constructing the predictive model is to monitor the reflux ratio change trend in real time and, in conjunction with the liquid level change in distribution plate 1, predict the future liquid level state; based on the prediction results, dynamically adjust the refrigerant flow rate to achieve height control of the expansion mass transfer section 2, thereby maintaining the stability of the gas-liquid mass transfer interface, preventing flooding and foam entrainment, and ensuring the operating efficiency and product purity of the distillation column. The predictive model includes the following steps:

[0133] Step 1: Data Acquisition: Real-time collection of liquid return flow and gas discharge flow using a flow meter, and calculation of the current return ratio based on this; simultaneously, real-time collection of liquid level height on distribution plate 1 using a level gauge.

[0134] Step Two: Reflux Ratio Change Prediction: Using a time series forecasting model, predict the future short-term (e.g., 5-minute) reflux ratio change trend based on historical reflux ratio data (e.g., the past 10-minute series). By identifying autoregressive and moving average patterns and combining them with an error correction term, determine whether the current reflux ratio deviates from the set value.

[0135] Step 3: Liquid level change prediction: By establishing a liquid level change equation and combining real-time liquid level sensor feedback data and flow meter data, the future liquid level change trend is predicted.

[0136] The equation for liquid level change is:

[0137]

[0138] in: The liquid level height of distribution plate 1; This refers to the liquid phase discharge rate from distribution plate 1; This refers to the amount of gas phase entering the system. , This is an empirical coefficient, which can be determined by calibration using historical data.

[0139] By combining real-time liquid level sensor feedback data and flow meter data with the aforementioned differential equation model, the future trend of liquid level change can be predicted.

[0140] It should be noted that the liquid phase discharge rate and gas phase inflow rate of distribution plate 1 can be directly obtained by installing sensors. This method is existing technology and will not be elaborated further here.

[0141] Step 4: Adjustment of the telescopic mass transfer section 2: Based on the reflux ratio and the trend of liquid level changes, control the operating power of the booster fan 9 and the opening of the regulating valve 10 to adjust the height of the movable part 202, thereby changing the height of the mass transfer tank 203. The adjustment method of the movable part 202 includes the following parts, specifically:

[0142] When the reflux ratio and liquid level are in the set state, the moving part 202 maintains the current working state.

[0143] When the reflux ratio is greater than the set value, the liquid level will gradually rise. At this time, by reducing the opening of the regulating valve 10 and increasing the operating power of the booster fan 9, the height of the mass transfer tank 203 is raised, reducing the possibility of flooding.

[0144] When the reflux ratio is less than the set value, the liquid level will gradually drop. At this time, by increasing the opening of the regulating valve 10 and reducing the operating power of the booster fan 9, the height of the mass transfer tank 203 will be lowered, reducing the possibility of foam entrainment.

[0145] When the reflux ratio is greater than the set value and remains in this state for a long time, the liquid level will continue to rise. At this time, by reducing the opening of the regulating valve 10, the operating power of the booster fan 9 is increased, so that the movable frame 402 drives the sealing part 801 to release the blockage of the drain hole 7, and open the forced discharge to avoid the possibility of flooding.

[0146] When the reflux ratio is less than the set value and remains in this state for a long time, the liquid level will continue to drop. At this time, by increasing the opening of the regulating valve 10, the operating power of the booster fan 9 is reduced so that the movable frame 402 can release the blockage of the air passage 401, thereby increasing the residence time of the liquid phase on the distribution plate 1 (i.e., water storage). At the same time, the gas phase contacts the liquid phase for mass transfer through the air passage 401 on part of the top cover 3.

[0147] It should be noted that when the reflux ratio is greater than the set value, but the liquid level does not change significantly or even drops, it indicates that the packing layer above the distribution plate 1 is blocked, preventing the liquid phase from passing smoothly through the packing layer and falling onto the distribution plate 1. In this case, the control system will send this situation to the background monitoring department through the data network, and the monitoring personnel will determine whether it is necessary to shut down the system for cleaning.

[0148] Example 5

[0149] This invention provides a purification process for a carbon tetrafluoride purification system, the purification process comprising the following steps:

[0150] Step 1: Pre-cooling of raw material gas: Carbon tetrafluoride raw material enters the pre-cooling unit 100 and exchanges heat with nitrogen refrigerant to lower the temperature of the raw material gas to the dew point, thereby achieving partial liquefaction of the raw material gas.

[0151] Step 2, Low-boiling column 400 distillation: The partially liquefied feed gas is distilled in the middle of the low-boiling column 400. The low-boiling column 400 precipitates impurities with a boiling point lower than that of carbon tetrafluoride, and the primary separated raw liquid is obtained.

[0152] Step 3, High-boiling column 700 distillation: The original liquid from the first separation is further distilled in the high-boiling column 700. The high-boiling column 700 separates impurities of carbon tetrafluoride that are higher than the boiling point of the original liquid from the first separation, and obtains high-purity carbon tetrafluoride.

[0153] Step 4: Reflux ratio monitoring and control: The gas discharge rate and liquid reflux rate of the distillation column are detected by a flow meter, and the change in the reflux ratio of the distillation column is calculated accordingly. The extension of the telescopic mass transfer section 2 is dynamically adjusted according to the change in the reflux ratio to adapt to the operating conditions of the distillation column.

[0154] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0155] Although embodiments of the invention have been shown and described, those skilled in the art will recognize that various changes, modifications, substitutions and variations 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 carbon tetrafluoride purification system, characterized in that, include: In the precooling unit (100), the raw material gas and the refrigerant nitrogen gas exchange heat to achieve partial liquefaction of the raw material gas; A low-boiling column (400) is used to precipitate impurities below the boiling point of carbon tetrafluoride to obtain a primary separation solution; The high-boiling column (700) is used to separate impurities with boiling points higher than those of the original liquid in the primary separation process, in order to obtain high-purity carbon tetrafluoride. Both the low-boiling tower (400) and the high-boiling tower (700) are equipped with arrayed packing layers, and distribution disks (1) are provided between the packing layers. The distribution disks (1) are equipped with arrayed telescopic mass transfer sections (2), and the gas and liquid phases are in contact and mass transfer in the top area of ​​the telescopic mass transfer section (2). The top of the low-boiling tower (400) and the high-boiling tower (700) are respectively equipped with a low-boiling condenser (500) and a high-boiling condenser (800). After the refrigerant of the two towers completes the condensation operation, it is introduced into the telescopic mass transfer section (2) through the input pipe and then discharged through the output pipe. The input pipe is equipped with a booster fan (9), and the output pipe is equipped with a regulating valve (10). By adjusting the operating power of the booster fan (9) and the opening size of the regulating valve (10), the amount of refrigerant entering the telescopic mass transfer section (2) can be controlled, so as to adjust the top height of the telescopic mass transfer section (2). The telescopic mass transfer unit (2) includes: The fastener (201) is located on the top of the distribution plate (1) and has a push chamber (204) inside. The air inlet (11) and the air outlet (12) are located at the bottom of the fixing part (201) and are connected to the push chamber (204). The refrigerant enters and exits the push chamber (204) through the air inlet (11) and the air outlet (12). The movable part (202) is located inside the push chamber (204) and is connected to the fixed part (201) through the elastic part (205). One end of the movable part (202) extending out of the push chamber (204) is provided with a mass transfer groove (203) where the gas and liquid phases are in contact and transfer mass. The movable part (202) has a top cover (3) at one end extending out of the push chamber (204). When the movable part (202) retracts to its limit, the top cover (3) abuts against the top of the fixed part (201) to stop the flow of liquid phase. The top cover (3) is provided with an exhaust section (4). When the top cover (3) comes into contact with the fixing member (201), the gas phase can enter the upper space of the distribution plate (1) from the exhaust section (4).

2. The carbon tetrafluoride purification system according to claim 1, characterized in that, The exhaust section (4) includes: Air passages (401) are arrayed inside the top cover (3); The movable frame (402) is slidably connected to the top cover (3) and has a vent (403) on it. When the movable frame (402) is in the first state, the vent (403) and the air passage (401) are misaligned, and the movable frame (402) blocks the air outlet of the air passage (401); when the movable frame (402) is in the second state, the vent (403) and the air passage (401) are aligned, and the movable frame (402) releases the blockage of the air passage (401).

3. The carbon tetrafluoride purification system according to claim 2, characterized in that, The fixing member (201) is also provided with a traction chamber (5), the top of the traction chamber (5) is provided with a drain hole (6), the bottom of the traction chamber (5) is provided with a drain hole (7), and a drain part (8) is provided at the drain hole (7), the drain part (8) is used to block the drain hole (7).

4. The carbon tetrafluoride purification system according to claim 3, characterized in that, The discharge section (8) includes: The sealing member (801) is disposed inside the traction chamber (5) and is connected to the fixing member (201) through the elastic member (804); The traction component (803) has one end connected to the sealing component (801) and the other end connected to the movable frame (402); When the sealing member (801) is in the first state, the sealing member (801) blocks the drain hole (7); when the sealing member (801) is in the second state, the sealing member (801) releases the blockage of the drain hole (7).

5. The carbon tetrafluoride purification system according to claim 4, characterized in that, The sealing member (801) is provided with a notch (802), which facilitates the liquid phase to enter the area below the distribution plate (1) through the drain hole (7).

6. The carbon tetrafluoride purification system according to claim 5, characterized in that, The movable component (202) includes a first section and a second section, and the mass transfer tank (203) is located in the second section; The movable parts (202) on the same distribution plate (1) have the same height in the first section, and the height of the second section is distributed in a staggered manner.

7. The carbon tetrafluoride purification system according to claim 1, characterized in that, Both the low-boiling condenser (500) and the high-boiling condenser (800) are equipped with flow meters at their gas phase outlets and liquid phase reflux outlets; The upper area of ​​the distribution plate (1) is equipped with a level gauge.

8. A purification process for purifying carbon tetrafluoride using the carbon tetrafluoride purification system according to any one of claims 1-7, characterized in that, The purification process includes the following steps: Step 1: Pre-cooling of raw material gas: Carbon tetrafluoride raw material enters the pre-cooling unit (100) and exchanges heat with nitrogen refrigerant to lower the temperature of raw material gas to the dew point, thereby achieving partial liquefaction of raw material gas; Step 2, Low-boiling tower (400) distillation: The partially liquefied feed gas is distilled in the middle of the low-boiling tower (400). The low-boiling tower (400) precipitates impurities below the boiling point of carbon tetrafluoride to obtain the primary separation liquid. Step 3, High-boiling column (700) distillation: The original liquid from the first separation continues to be distilled in the high-boiling column (700). The high-boiling column (700) separates the impurities of carbon tetrafluoride that are higher than the boiling point of the original liquid from the first separation, and obtains high-purity carbon tetrafluoride. Step 4, reflux ratio monitoring and control: The gas discharge and liquid reflux flow of the distillation column are detected by the flow meter, and the change of the reflux ratio of the distillation column is calculated accordingly. The extension of the expansion and contraction mass transfer section (2) is dynamically adjusted according to the change of the reflux ratio to adapt to the operating conditions of the distillation column.

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