Purification system and purification method of carbon tetrafluoride

Abstract

The invention relates to the technical field of gas purification, in particular to a carbon tetrafluoride purification system and method, and the purification system comprises a precooling unit, a low-boiling tower and a high-boiling tower; packing layers in array distribution are arranged in the low-boiling tower and the high-boiling tower, a distribution disc is arranged between the packing layers, and telescopic mass transfer parts in array distribution are arranged on the distribution disc; a low-boiling condenser and a high-boiling condenser are arranged at the tops of the low-boiling tower and the high-boiling tower respectively, and refrigerants of the low-boiling tower and the high-boiling tower are introduced into the telescopic mass transfer part through an input pipe after condensation operation is completed and then are discharged through an output pipe; the flow meter is used for detecting the gas discharge amount and the liquid backflow amount of the rectifying tower, the backflow ratio change of the rectifying tower is calculated according to the gas discharge amount and the liquid backflow amount of the rectifying tower, and then the amount of refrigerants introduced into the telescopic mass transfer part can be adjusted and controlled by adjusting the operation power of the booster fan and the opening size of the adjusting valve; therefore, the top height of the telescopic mass transfer part is adjusted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas purification, and in particular to a purification system for carbon tetrafluoride and a purification method thereof. BACKGROUND

[0002] Carbon tetrafluoride, whose chemical formula is CF4, is colorless and non-flammable at room temperature, and its chemical properties are quite stable, showing strong inertness. In a normal pressure environment, it needs to be heated to 800℃ to start thermal decomposition reaction.

[0003] Carbon tetrafluoride is an important plasma etching gas in the current microelectronic industry, which is mainly used in the plasma etching and cleaning process of various integrated circuits. At present, the mainstream method for preparing CF4 in the domestic and foreign chemical industry is fluorocarbon direct synthesis method. However, the purity of CF4 produced by this method mainly depends on the product yield of the fluorocarbon reaction stage and the impurity removal effect of the purification and refining stage.

[0004] A carbon tetrafluoride rectification purification system is disclosed in Chinese patent No. CN202223613020.5. The low-temperature rectification system is coupled with the overhead condensers of the heavy-removing rectification tower and the light-removing rectification tower and the refrigeration circulation system through the heat exchange box and the heat carrier circulation heating system powered by the circulating pump. The fluorine production unit is connected in sequence with the fluorocarbon reactor-cracking device-purification unit-first buffer tank-process compressor-first adsorption tower-second adsorption tower-low-temperature filter-heavy-removing rectification tower-third adsorption-light-removing rectification tower. The tower kettle of the heavy-removing rectification tower is connected between the fluorine production unit and the fluorocarbon reactor. The heating medium of the heavy-removing rectification tower kettle reboiler forms a loop with the heat exchange box through the heat carrier circulating pump. The tower kettle of the light-removing rectification tower also forms a loop with the heat exchange box through the heat carrier circulating pump. Two gas separation membranes are connected to the first buffer tank through the overhead pipeline of the light-removing rectification tower. The purification system is energy-saving and environmentally friendly.

[0005] Although the foregoing patent document solves the problems of high energy consumption and low equipment utilization rate of the existing rectification method for recovering hexafluoroethane. However, in the actual application process, the packing tower is widely used as the main separation device when the crude carbon tetrafluoride gas is purified in the prior art. However, when purified by the packing tower, the product purity is extremely sensitive to the dynamic change of the gas-liquid reflux ratio. The current technology mainly relies on two types of operations to control the fluctuation of the reflux ratio: adjusting the product withdrawal amount at the tower top or adjusting the working condition parameters of the condensing system. It should be noted that such control means has significant response lag, which makes it difficult for the system to synchronize with the transient change of the reflux ratio, thereby failing to dynamically optimize the mass transfer state of the gas-liquid two-phase, i.e. the contact time and the interface update rate. Further, it leads to the decline of the rectification efficiency of the packing tower. SUMMARY

[0006] The present application aims to provide a purification system and method of carbon tetrafluoride to solve the technical problems in the background.

[0007] To achieve the above object, the present application provides the following technical solutions. A purification system of carbon tetrafluoride, comprising: A pre-cooling unit, in which raw gas exchanges heat with refrigerant nitrogen to achieve partial liquefaction of the raw gas; A low-boiling tower for separating impurities with a boiling point lower than that of carbon tetrafluoride to obtain a primary separation raw liquid; A high-boiling tower for separating impurities with a boiling point higher than that of the primary separation raw liquid to obtain high-purity carbon tetrafluoride; The low-boiling tower and the high-boiling tower are both internally provided with an array of packing layers, and a distribution plate is arranged between the packing layers, and an array of telescopic mass transfer parts is arranged on the distribution plate, and gas-liquid two-phase contact mass transfer is performed at the top region of the telescopic mass transfer parts; The low-boiling tower and the high-boiling tower are both provided with a low-boiling condenser and a high-boiling condenser at the top, respectively, and the refrigerants of the two condensers are introduced into the telescopic mass transfer parts through an input pipe after completing the condensing operation, and then discharged through an output pipe; The input pipe is provided with a booster fan, and the output pipe is provided with an adjusting valve, and the amount of refrigerant introduced into the telescopic mass transfer parts is adjusted by adjusting the operating power of the booster fan and the opening size of the adjusting valve to adjust the height of the top of the telescopic mass transfer parts.

[0008] Preferably, the telescopic mass transfer part comprises: A fixed part arranged at the top of the distribution plate, and provided with a pushing chamber inside; An air inlet and an air outlet, both located at the bottom of the fixed part and communicating with the pushing chamber, and the refrigerant enters and exits the pushing chamber through the air inlet and the air outlet; A movable part arranged inside the pushing chamber and connected with the fixed part through an elastic part, and provided with a mass transfer groove at one end of the movable part extending out of the pushing chamber, and the gas-liquid two-phase contact mass transfer is performed at the mass transfer groove.

[0009] Preferably, the one end of the movable part extending out of the pushing chamber is provided with a top cover, and when the movable part is retracted to the limit value, the top cover abuts against the top of the fixed part to achieve liquid flow stop; The inside of the top cover is provided with an exhaust part, and when the top cover abuts against the fixed part, the gas phase enters the upper space of the distribution plate from the exhaust part.

[0010] Preferably, the exhaust part comprises: An air duct arrayed inside the top cover; A movable frame slidingly connected with the top cover, and provided with an air inlet on the movable frame; When the movable frame is in the first state, the venting port is misaligned with the airway, and the movable frame blocks the air outlet of the airway; when the movable frame is in the second state, the venting port is aligned with the airway, and the movable frame unblocks the airway.

[0011] Preferably, the inside of the fixing member is further provided with a pulling chamber, the top of the pulling chamber is provided with a drainage hole, the bottom of the pulling chamber is provided with a drainage hole, and the drainage hole is provided with a drainage part for blocking the drainage hole.

[0012] Preferably, the drainage part comprises: a blocking member arranged in the inside of the pulling chamber and connected with the fixing member through an elastic member; a pulling member connected with the blocking member at one end and connected with the movable frame at the other end; When the blocking member is in the first state, the blocking member blocks the drainage hole; when the blocking member is in the second state, the blocking member unblocks the drainage hole.

[0013] Preferably, the blocking member is provided with a notch, and the notch facilitates the liquid phase to enter the lower area of the distribution disc through the drainage hole.

[0014] Preferably, the movable member comprises a first interval and a second interval, and the mass transfer tank is located in the second interval. The movable members on the same distribution disc have the same height of the first interval and the height of the second interval is distributed in a staggered manner.

[0015] Preferably, the gas phase discharge port and the liquid phase reflux port of the low-boiling condenser and the high-boiling condenser are each provided with a flow meter. The upper area of the distribution disc is provided with a liquid level meter.

[0016] A purification process of carbon tetrafluoride, the purification process comprising the following steps: Step one, raw material gas pre-cooling: the raw material carbon tetrafluoride enters the pre-cooling unit and exchanges heat with the refrigerant nitrogen, so that the temperature of the raw material gas is reduced to the dew point, realizing the partial liquefaction of the raw material gas; Step two, low-boiling tower rectification: the partially liquefied raw material gas is rectified in the middle part of the low-boiling tower, and the low-boiling tower precipitates impurities lower than the boiling point of carbon tetrafluoride to obtain a primary separation raw liquid; Step three, high-boiling tower rectification: the primary separation raw liquid is further rectified in the high-boiling tower, and the high-boiling tower separates the impurities of carbon tetrafluoride higher than the boiling point of the primary separation raw liquid to obtain high-purity carbon tetrafluoride; Step four, reflux ratio monitoring and regulation: the flow meters detect the gas discharge amount and the liquid discharge amount of the rectification tower, and calculate the change of the reflux ratio of the rectification tower according to the above, and dynamically adjust the extension amount of the telescopic mass transfer part according to the change of the reflux ratio, so as to adapt to the operating conditions of the rectification tower.

[0017] Technical effects and advantages of the present application: The present application can maintain the stability of the gas-liquid mass transfer interface in the rectifying column by dynamically adjusting the height of the movable part, effectively solving the problems of flooding and foam entrainment. When the liquid level of the distribution plate deviates from the set range due to abnormal reflux ratio, the power of the booster fan and the opening degree of the regulating valve are adjusted to change the amount of coolant entering the telescopic mass transfer part push chamber, and then the height of the mass transfer groove is adjusted by controlling the lifting of the movable part. Avoid flooding caused by liquid phase flooding the mass transfer groove when the liquid level is too high, and gas phase entraining foam when the liquid level is too low; at the same time, under long-term abnormal working conditions, the cooperative action of the movable part and the fixed part realizes forced drainage of the liquid phase or mass transfer of the gas phase, further enhancing the adaptability of the system to complex working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The main flowchart of the embodiment one of the present application is shown in the figure. Figure 2 The structure diagram of the low-boiling tower and the high-boiling tower of the present application is shown in the figure. Figure 3 The main flowchart of the embodiment two of the present application is shown in the figure. Figure 4 The structure diagram of the distribution plate of the present application is shown in the figure. Figure 5 The structure diagram of the telescopic mass transfer part of the present application is shown in the figure. Figure 6 The internal structure diagram of the telescopic mass transfer part of the present application is shown in the figure. Figure 7 The cross-sectional structure diagram of the telescopic mass transfer part of the present application is shown in the figure. Figure 8 The structure diagram of the drainage part of the present application is shown in the figure. Figure 9 The structure diagram of the exhaust part of the present application is shown in the figure. Figure 10 The height difference diagram of the movable part on the same distribution plate of the present application is shown in the figure. Figure 11 The state difference diagram when the movable part on the same distribution plate of the present application is lowered is shown in the figure.

[0019] In the figure: 100, pre-cooling unit; 200, receiving tank; 300, low-boiling reboiler; 400, low-boiling tower; 500, low-boiling condenser; 600, high-boiling reboiler; 700, high-boiling tower; 800, high-boiling condenser; 900, cold box; 1, distribution plate; 2, telescopic mass transfer part; 201, fixed part; 202, movable part; 203, mass transfer groove; 204, pushing chamber; 205, elastic part; 3, top cover; 4, exhaust part; 401, air duct; 402, movable frame; 403, air vent; 5, pulling chamber; 6, flow hole; 7, drain hole; 8, flow part; 801, blocking part; 802, notch; 803, traction part; 804, elastic part; 9, booster fan; 10, regulating valve; 11, air inlet; 12, air outlet. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] Embodiment one Referring to Figures 1 to 2 The present application provides a purification system of carbon tetrafluoride, comprising: A pre-cooling unit 100, in which raw gas exchanges heat with refrigerant nitrogen to achieve partial liquefaction of the raw gas.

[0022] A low-boiling tower 400, which is used to separate impurities with a boiling point lower than that of carbon tetrafluoride to obtain a primary separation raw liquid.

[0023] A high-boiling tower 700, which is used to separate impurities with a boiling point higher than that of the primary separation raw liquid to obtain high-purity carbon tetrafluoride.

[0024] The low-boiling tower 400 and the high-boiling tower 700 are both internally provided with an array of packing layers, and a distribution plate 1 is arranged between the packing layers, and the distribution plate 1 is provided with an array of telescopic mass transfer parts 2, and gas-liquid two-phase contact mass transfer is performed in the top region of the telescopic mass transfer parts 2.

[0025] The top of the low-boiling tower 400 and the high-boiling tower 700 is respectively provided with a low-boiling condenser 500 and a high-boiling condenser 800; and the top of the low-boiling tower 400 and the high-boiling tower 700 is respectively provided with a low-boiling reboiler 300 and a high-boiling reboiler 600.

[0026] During use, the raw material carbon tetrafluoride (impure CF4) first enters the pre-cooling unit 100. In the pre-cooling unit 100, the raw material gas exchanges heat with the refrigerant nitrogen gas, so that the temperature of the raw material gas is reduced to the dew point of -65°C, and the raw material gas is partially liquefied. Subsequently, the partially liquefied raw material gas is sent into the cold box 900.

[0027] After the partially liquefied raw material gas enters the cold box 900, it first enters the raw material pre-cooling receiving tank 200, and then is transported to the middle of the low-boiling tower 400 for rectification. The liquid raw material is collected in the low-boiling reboiler 300, and the gaseous raw material rises along the low-boiling tower 400 to the top. In the low-boiling reboiler 300, the liquefied raw material liquid exchanges heat with the heat medium Freon, and the light components (N2, O2) in the raw material liquid are largely evaporated and rise to the top along the low-boiling tower 400. At this time, the gas at the top of the low-boiling tower 400 is introduced into the low-boiling condenser 500 and exchanges heat with the refrigerant liquid nitrogen. The gas with a higher boiling point (CF4) is converted from the gaseous state to the liquid state and flows back into the low-boiling tower 400; while the impurities (N2, O2) with a lower boiling point remain in the gaseous state and are discharged out of the tower. In the low-boiling tower 400, the rising gaseous state and the backflowing liquid state exchange mass and heat, and are fully contacted. After multiple condensation and evaporation processes, the low-boiling point impurities are discharged out of the tower, and the higher boiling point substance (CF4) is collected in the low-boiling reboiler 300.

[0028] Next, the raw material liquid collected in the low-boiling reboiler 300 is introduced into the high-boiling tower 700 for further rectification. The rectification principle in the high-boiling tower 700 is similar to that in the low-boiling tower 400: the raw material 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 along the high-boiling tower 700. Then, these gases are introduced into the high-boiling condenser 800 and exchange heat with the liquid nitrogen. The impurities with a higher boiling point are re-condensed into the liquid state and flow back into the high-boiling tower 700, where they exchange mass and heat with the rising gas and are fully contacted. In the high-boiling tower 700, after multiple condensation and evaporation processes, the CF4 with a lower boiling point is separated and supplied to the user; while the impurities with a higher boiling point return to the high-boiling reboiler 600 and are finally discharged out of the tower.

[0029] Example Two Although the above-mentioned examples can achieve the purification of carbon tetrafluoride, in actual application, the rectification tower mainly realizes the separation of mixtures through the countercurrent contact of gas and liquid phases, and the core mechanism lies in the use of the boiling point difference of each component to form light components and heavy components that are gradually concentrated in the tower. The reflux ratio is a key parameter for adjusting the separation efficiency. When the reflux ratio abnormally changes, it may cause the imbalance of gas and liquid two-phase flow in the tower, and then cause operation failures such as liquid flooding and foam entrainment, which seriously affects the product quality and the safety of the device. In view of this, technical improvements are made on the basis of Example One, and the improved technical scheme is as follows: Referring to Figures 1 to 9 As shown in the drawings, the present application provides a purification system for carbon tetrafluoride, wherein the low-boiling tower 400 and the high-boiling tower 700 are both internally provided with arrayed packing layers, and a distribution plate 1 is arranged between the packing layers, and the distribution plate 1 is provided with arrayed telescopic mass transfer parts 2, and the gas-liquid two-phase is contacted and mass transferred at the top region of the telescopic mass transfer parts 2.

[0030] The low-boiling tower 400 and the high-boiling tower 700 are respectively provided with a low-boiling condenser 500 and a high-boiling condenser 800, and the refrigerants of the two are input into the telescopic mass transfer parts 2 after completing the condensing operation, and then are discharged through the output pipes.

[0031] The input pipe is provided with a booster fan 9, and the output pipe is provided with an adjusting valve 10, and the refrigerant amount input into the telescopic mass transfer parts 2 is controlled by adjusting the operating power of the booster fan 9 and the opening size of the adjusting valve 10, so as to realize the adjustment of the top height of the telescopic mass transfer parts 2.

[0032] Specifically, the telescopic mass transfer part 2 comprises a fixed part 201 arranged at the top of the distribution plate 1, the fixed part 201 is internally provided with a pushing chamber 204, the pushing chamber 204 is internally provided with a movable part 202, the movable part 202 is connected with the fixed part 201 through an elastic part 205, one end of the movable part 202 extending out of the pushing chamber 204 is provided with a mass transfer groove 203, and the gas-liquid two-phase is contacted and mass transferred at the mass transfer groove 203. The fixed part 201 and the movable part 202 are both annular, and the gas phase moves to the top of the tower through the annular space.

[0033] The liquid phase flows downward from the top of the tower and gradually accumulates on the distribution plate 1. When the liquid level of the liquid phase in the distribution plate 1 rises to the position of the mass transfer groove 203, the liquid phase will flow into the annular space formed by the fixed part 201 and the movable part 202 through the mass transfer groove 203, and is contacted and mass transferred with the gas phase.

[0034] The fixed part 201 is provided with an air inlet 11 and an air outlet 12, the air inlet 11 and the air outlet 12 are communicated with the pushing chamber 204, and the refrigerant enters and exits the pushing chamber 204 through the air inlet 11 and the air outlet 12.

[0035] One end of the movable part 202 extending out of the pushing chamber 204 is provided with a top cover 3, and the top cover 3 is conical.

[0036] The gas phase discharge outlet and the liquid phase reflux port of the low-boiling condenser 500 and the high-boiling condenser 800 are both provided with flow meters; the flow meter arranged at the gas phase discharge outlet is used for detecting the discharge amount of the gas; and the flow meter arranged at the liquid phase reflux port is used for detecting the reflux amount of the liquid.

[0037] The reflux ratio change of the low-boiling condenser 500 and the high-boiling condenser 800 can be calculated through the reflux formula, and the reflux formula is as follows: Wherein, L is the amount of liquid reflux; D is the amount of gas discharge.

[0038] In use, by calculating the reflux ratio of the low-boiling condenser 500 and the high-boiling condenser 800, the extension amount of the telescopic mass transfer part 2 is dynamically adjusted, thereby avoiding the technical problems of liquid flooding or foam entrainment.

[0039] Specifically: When the gas phase is introduced into the condenser, the gas phase exchanges heat with the refrigerant (liquid nitrogen) in the condenser, the gas phase with a higher boiling point is re-converted from gas to liquid, and re-returns to the rectifying column through the liquid phase reflux port; while the impurities with a lower boiling point remain in the gaseous state and are discharged from the gas phase discharge port to the outside of the column; in this process, the flow meter arranged at the gas phase discharge port detects the gas discharge amount per unit time; the flow meter arranged at the liquid phase reflux port detects the liquid reflux amount per unit time, and the reflux ratio change of the low-boiling condenser 500 and the high-boiling condenser 800 is calculated through the reflux formula.

[0040] The liquid nitrogen in the condenser is converted into nitrogen gas after completing heat exchange, the nitrogen gas is introduced into the push chamber 204 of each fixed part 201 through the input pipe, by controlling the amount of nitrogen gas introduced into the push chamber 204, a pushing force is generated on the movable part 202 in the push chamber 204, so as to adjust the telescopic amount of the telescopic mass transfer part 2.

[0041] Taking the low-boiling column 400 as an example, the telescopic amount adjustment steps of the telescopic mass transfer part 2 are as follows: When the control system detects that the current reflux ratio of the low-boiling column 400 is greater than the set value, it indicates that the purity of the carbon tetrafluoride crude gas introduced into the low-boiling column 400 is high (there are fewer impurities with a lower boiling point). This leads to a decrease in the amount of gas discharge per unit time detected by the flow meter at the gas phase discharge port, and an increase in the amount of liquid reflux per unit time detected by the flow meter at the liquid phase reflux port, ultimately resulting in the current reflux ratio of the low-boiling column 400 being greater than the set value.

[0042] When the liquid reflux amount increases, the liquid level of the distribution plate 1 will also rise synchronously. At this time, when the gas-liquid two phases are in contact mass transfer, the risk of liquid flooding is likely to occur. Therefore, when the control system detects that the reflux ratio of the low-boiling column 400 is greater than the set value, the difference between the current reflux ratio of the low-boiling column 400 and the set value, the opening of the regulating valve 10 of the control output pipe is reduced, the power of the booster fan 9 on the input pipe is increased, the amount of nitrogen gas introduced into the push chamber 204 is increased, the pushing force of the nitrogen gas on the movable part 202 is increased, and the movable part 202 is further moved upward, so as to increase the height of the mass transfer groove 203. On the basis of ensuring gas-liquid mass transfer, after the liquid phase submerges the telescopic mass transfer part 2, the gas needs to overcome the additional hydrostatic pressure to pass through, resulting in a sharp increase in the total pressure drop of the system.

[0043] When the control system detects that the current low-boiling tower 400 reflux ratio is lower than the set value, it indicates that the content of impurities (especially lower boiling point impurities) in the carbon tetrafluoride crude gas entering the low-boiling tower 400 is relatively high. This leads to an increase in the amount of gas discharged per unit of time measured by the flow meter at the gas phase discharge outlet, and a decrease in the amount of liquid reflux per unit of time measured by the flow meter at the liquid phase reflux outlet, ultimately resulting in the current low-boiling tower 400 reflux ratio being lower than the set value.

[0044] When the liquid reflux amount decreases, the liquid level of the distribution plate 1 will also decrease simultaneously. At this time, when the gas-liquid two-phase is in contact mass transfer, the risk of foam entrainment is high. Therefore, when the control system detects that the low-boiling tower 400 reflux ratio is lower than the set value, the difference between the current low-boiling tower 400 reflux ratio and the set value controls the opening of the regulating valve 10 of the output pipe to increase, the power of the booster fan 9 on the input pipe to decrease, the amount of nitrogen gas entering the push chamber 204 to decrease, and the pushing force of nitrogen gas on the movable part 202 to decrease. At this time, under the elastic recovery ability of the elastic part 804, the elastic part 804 drives the movable part 202 to move downward, so that the height of the mass transfer groove 203 decreases, that is, the liquid level on the distribution plate 1 does not need to rise to the set height to perform contact mass transfer with the gas phase.

[0045] Embodiment Three Although the above embodiments can slow down the phenomenon of liquid flooding and foam entrainment in the rectifying tower to a certain extent, in actual application, if the reflux ratio changes and remains in this state for a long time, simply lifting or lowering the height of the mass transfer groove 203 can only slow down the phenomenon, and cannot make the mass transfer state of the gas-liquid two-phase at the distribution plate 1 always in the set state. Therefore, based on Embodiment Two, technical improvements are made, and the improved technical scheme is as follows: Referring to Figures 1 to 11 The present application provides a carbon tetrafluoride purification system, one end of the movable part 202 extending out of the push chamber 204 is provided with a top cover 3, when the movable part 202 is retracted to the limit value, the top cover 3 abuts against the top of the fixed part 201 to achieve liquid flow stop.

[0046] The inside of the top cover 3 is provided with an exhaust part 4, when the top cover 3 abuts against the fixed part 201, the gas phase can enter the upper space of the distribution plate 1 from the exhaust part 4.

[0047] Specifically, the exhaust part 4 includes a gas channel 401 opened in the inside of the top cover 3, and the gas channel 401 is arrayed in the inside of the top cover 3. The gas channel 401 is preferably a straight channel or a curved channel.

[0048] The outer side of the top cover 3 is slidably connected with a movable frame 402, and the movable frame 402 is provided with a ventilation opening 403; when the movable frame 402 is in a first state, the ventilation opening 403 is in a dislocation state with the air duct 401, and the movable frame 402 blocks the air outlet end of the air duct 401; when the movable frame 402 is in a second state, the ventilation opening 403 is in a coincidence state with the air duct 401, and the movable frame 402 unblocks the air duct 401.

[0049] The movable frame 402 includes a ring plate arranged above the top cover 3 and a pressing ring arranged below the top cover 3, and the ring plate and the pressing ring are directly provided with an array of sliding plates, the sliding plates are slidably connected with the top cover 3, and the ventilation opening 403 is located on the sliding plates.

[0050] Specifically, the inside of the fixed part 201 is further provided with a pulling chamber 5, the top of the pulling chamber 5 is provided with a flow hole 6, the bottom of the pulling chamber 5 is provided with a drainage hole 7, the drainage hole 7 is provided with a flow part 8, and the flow part 8 is used for blocking the drainage hole 7.

[0051] Specifically, the flow part 8 includes a blocking part 801 arranged in the pulling chamber 5, and the blocking part 801 is connected with the fixed part 201 through an elastic part 804.

[0052] When the blocking part 801 is in a first state, the blocking part 801 blocks the drainage hole 7; when the blocking part 801 is in a second state, the blocking part 801 unblocks the drainage hole 7. The blocking part 801 includes a ring block arranged in the pulling chamber 5, and the ring block is provided with a blocking block corresponding to the drainage hole 7.

[0053] The blocking part 801 and the movable frame 402 are provided with a traction part 803, and the traction part 803 includes a traction rope or a telescopic rod, and the main purpose is to realize the pulling of the blocking part 801.

[0054] Specifically, the blocking part 801 is provided with a notch 802, and the notch 802 facilitates the liquid phase to enter the lower area of the distribution disc 1 through the drainage hole 7. The notch 802 is located on the ring block.

[0055] Specifically, the movable part 202 includes a first interval and a second interval, and the mass transfer groove 203 is located in the second interval.

[0056] The heights of the first intervals of the movable parts 202 on the same distribution disc 1 are the same, and the heights of the second intervals of the movable parts 202 are staggered.

[0057] In order to ensure the mass transfer effect of the gas-liquid two-phase, the liquid phase flowing out of the mass transfer tank 203 needs to be in a stable effect, and when the reflux ratio is greater than the set value and is in this state for a long time, simply increasing the height of the mass transfer tank 203 can only play a buffering role; the amount of liquid phase falling on the distribution plate 1 is still greater than the discharge amount of the mass transfer tank 203, and when the mass transfer tank 203 rises to the highest point, if the liquid level of the distribution plate 1 is still in a state of continuous rise, without corresponding technical means, the liquid phase will eventually flood the mass transfer tank 203, and then the problem of flooding occurs. Therefore, this embodiment proposes a technical solution based on embodiment two. The specific scheme is as follows: When the reflux ratio is greater than the set value and is in this state for a long time, it indicates that the liquid level on the distribution plate 1 is gradually rising, at this time, 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 on the basis of embodiment two, so that the amount of nitrogen gas entering the push chamber 204 increases, and the pushing force of the nitrogen gas on the movable part 202 increases, the nitrogen gas pushes the movable part 202 to move upwards, so that the height of the mass transfer tank 203 increases, at this time, when the movable part 202 moves upwards, 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 plugging state of the drain hole 7, at this time, part of the liquid phase on the distribution plate 1 enters the pull chamber 5 through the flow hole 6, and directly flows to the lower area of the distribution plate 1 through the gap 802 and the drain hole 7, so that the liquid phase on the distribution plate 1 decreases, avoiding the problem of flooding caused by the continuous rise of the liquid level on the distribution plate 1 when the reflux ratio is greater than the set value for a long time.

[0058] When the reflux ratio is less than the set value and is in this state for a long time, simply reducing the height of the mass transfer tank 203 can only play a buffering role. The amount of liquid phase falling on the distribution plate 1 is still less than the discharge amount of the mass transfer tank 203, but when the mass transfer tank 203 drops to the highest point, if the liquid level of the distribution plate 1 is still in a state of continuous decline, without corresponding technical means, the problem of foam entrainment will eventually occur. Therefore, this embodiment proposes a technical solution based on embodiment two. The specific scheme is as follows: When the reflux ratio is less than the set value and is in this state for a long time, it indicates that the liquid level on the distribution plate 1 is continuously declining, at this time, 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 on the basis of embodiment two, so that the amount of nitrogen gas entering the push chamber 204 decreases, and the pushing force of the nitrogen gas on the movable part 202 decreases, at this time, under the elastic recovery ability of the elastic part 804, the elastic part 804 drives the movable part 202 to move downwards, so that the height of the mass transfer tank 203 decreases.

[0059] Due to the same distribution plate 1 in the embodiment, the height of the first interval of the movable part 202 is the same, the height of the second interval is staggered, and the mass transfer groove 203 is located in the second interval. When the elastic part 804 drives the movable part 202 to move downward, part of the movable part 202 will be in contact with the top of the fixed part 201 during the downward movement. In this process, the top of the fixed part 201 extrudes the movable frame 402, driving the movable frame 402 to move upward. Even if the movable frame 402 is in the second state, the air vent 403 is in the overlapping state with the air duct 401, and the movable frame 402 unblocks the air duct 401. As shown in Figure 11

[0060] At this time, the top cover 3 of part of the movable part 202 is in contact with the fixed part 201, which is equivalent to blocking part of the mass transfer groove 203, so that the liquid phase cannot enter the lower area of the distribution plate 1 through the mass transfer groove 203 of part of the movable part 202, that is, the water output of the distribution plate 1 is reduced, thereby solving the problem of continuous decrease of liquid level on the distribution plate 1. At the same time, since the movable frame 402 unblocks the air duct 401 at this time, the gas phase can enter the upper space of the distribution plate 1 through the air duct 401, and the air outlet 12 of the air duct 401 is located on the side 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 that the gas phase can be discharged from the air outlet 12 of the air duct 401. When the gas phase is discharged from the air outlet 12 of the air duct 401, it can still be in contact with the liquid phase for mass transfer.

[0061] It should be noted that in the embodiment, a bend can be provided at the air outlet 12 of the air duct 401, the outlet of the bend is below the liquid level of the liquid phase, and the bending point of the bend is above the liquid level of the liquid phase, so that the gas phase can be in contact with the deep liquid phase for mass transfer, and the liquid phase cannot enter the air duct 401.

[0062] It should be noted that: in the embodiment, the heights of the mass transfer grooves 203 of the movable parts 202 on the same distribution plate 1 are not the same, but the bottom heights of the mass transfer grooves 203 are on the same horizontal line.

[0063] Embodiment four Although the above embodiment can avoid the problems of liquid flooding and foam entrainment caused by long-term non-set state of the reflux ratio, in actual application, the working state in the rectifying tower is complex. Simply adjusting the working parameters of the booster fan 9 and the regulating valve 10 to solve the problems of liquid flooding and foam entrainment is too arbitrary, and it is impossible to correct the actual required working parameters according to the feedback information before and after the adjustment. In view of this, the technical improvement is made on the basis of embodiment three, and the improved technical scheme is as follows: ​The present application provides a purification system for carbon tetrafluoride, wherein the gas phase discharge outlet and the liquid phase reflux port of the low-boiling condenser 500 and the high-boiling condenser 800 are provided with flow meters. The upper area of the distribution plate 1 is provided with a liquid level meter.

[0064] By arranging flow meters at the gas phase discharge outlet and the liquid phase reflux port of the low-boiling condenser 500 and the high-boiling condenser 800, the reflux ratio of the rectification tower is obtained according to the ratio of the two flow meters, and the working parameters of the booster fan 9 and the regulating valve 10 are dynamically adjusted according to the reflux ratio, thereby avoiding technical problems such as liquid flooding and foam entrainment in the rectification tower.

[0065] The upper area of the distribution plate 1 is provided with a liquid level meter for real-time monitoring of the liquid level change on the distribution plate 1. The data information collected by the liquid level meter in real time is used as feedback information to adjust the actual required working parameters of the booster fan 9 and the regulating valve 10.

[0066] 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 detects the liquid level information on the current distribution plate 1 through the liquid level meter, predicts the subsequent liquid level change amount through a prediction model, and then adjusts the height of the movable part 202 through the regulating valve 10 and the booster fan 9, so as to avoid technical problems such as liquid flooding or foam entrainment.

[0067] The purpose of constructing the prediction model is to real-time monitor the reflux ratio change trend, and predict the future liquid level state in combination with the distribution plate 1 liquid level change. According to the prediction result, the refrigerant input amount is dynamically adjusted to realize the height control of the telescopic mass transfer part 2, so as to maintain the stability of the gas-liquid mass transfer interface, prevent liquid flooding and foam entrainment, and ensure the operation efficiency and product purity of the rectification tower. The prediction model includes the following steps: Step one: data acquisition: real-time acquisition of liquid reflux amount and gas discharge amount through the flow meter, and calculation of the current reflux ratio according to the same; at the same time, real-time acquisition of the distribution plate 1 liquid level height through the liquid level meter.

[0068] Step two: reflux ratio change prediction: through a time series prediction model, the future short-term (for example, 5 minutes) reflux ratio change trend is predicted based on historical reflux ratio data (for example, past 10 minutes sequence). By identifying the autoregressive and moving average rules, and combining the error correction term, it is predicted whether the current reflux ratio deviates from the set value.

[0069] Step three: liquid level change prediction: by establishing a liquid level change equation, the future liquid level change trend is predicted in combination with the real-time liquid level sensor feedback data and the flow meter data.

[0070] The liquid level change equation is: Wherein: is the distribution plate 1 liquid level height; Liquid phase discharge of distribution tray 1; Gas phase inlet of distribution tray 1; , is an empirical coefficient, which can be calibrated by historical data.

[0071] Through real-time liquid level sensor feedback data and flowmeter data, combined with the above differential equation model, the future liquid level change trend is predicted.

[0072] It should be noted that the liquid phase discharge of distribution tray 1 and the gas phase inlet can be directly obtained by installing sensors. This method belongs to the prior art and will not be described in detail here.

[0073] Step four: telescopic mass transfer part 2 regulation: according to the reflux ratio and the change trend of liquid level, the operating power of booster fan 9 and the opening of regulating valve 10 are controlled to adjust the lifting of movable part 202 and change the height of mass transfer tank 203. The adjustment mode of movable part 202 includes the following parts, which are as follows: When the reflux ratio and the liquid level are in the set state, the movable part 202 maintains the current working state.

[0074] When the reflux ratio is greater than the set value, the liquid level will gradually rise, at this time, by reducing the opening of regulating valve 10 and increasing the operating power of booster fan 9, the height of mass transfer tank 203 is lifted to reduce the possibility of liquid overflow.

[0075] When the reflux ratio is less than the set value, the liquid level will gradually decrease, at this time, by increasing the opening of regulating valve 10 and reducing the operating power of booster fan 9, the height of mass transfer tank 203 is lowered to reduce the possibility of foam entrainment.

[0076] When the reflux ratio is greater than the set value and is in this state for a long time, the liquid level will continue to rise, at this time, by reducing the opening of regulating valve 10 and increasing the operating power of booster fan 9, the movable frame 402 drives the blocking part 801 to unblock the drain hole 7, opens the forced drainage to avoid the possibility of liquid overflow.

[0077] When the reflux ratio is less than the set value and is in this state for a long time, the liquid level will continue to decrease, at this time, by increasing the opening of regulating valve 10 and reducing the operating power of booster fan 9, the movable frame 402 unblocks the air duct 401 to increase the residence time of liquid phase on the distribution tray 1 (i.e. water storage), while the gas phase contacts the liquid phase through the air duct 401 on part of the top cover 3 for mass transfer.

[0078] It should be noted that when the reflux ratio is greater than the set value, but the liquid level change is not obvious or even appears to drop, indicating that the packing layer above the distribution plate 1 is blocked, causing the liquid phase to fail to fall through the packing layer to the distribution plate 1, at this time the control system sends such cases to the background supervision through the data network, and the supervisor judges whether it needs to be stopped for cleaning.

[0079] Example five The present application provides a kind of purification process of carbon tetrafluoride purification system, the purification process includes the following steps: Step one, raw material gas precooling: raw material carbon tetrafluoride enters precooling unit 100, and exchanges heat with refrigerant nitrogen, so that the temperature of raw material gas is reduced to dew point, realizes the partial liquefaction of raw material gas.

[0080] Step two, low boiling tower 400 rectification: the partially liquefied raw material gas is rectified in the middle of low boiling tower 400, and low boiling tower 400 is separated from the impurities lower than the boiling point of carbon tetrafluoride, to obtain primary separation raw liquid.

[0081] Step three, high boiling tower 700 rectification: the primary separation raw liquid is continuously rectified in high boiling tower 700, and high boiling tower 700 separates the impurities higher than the boiling point of primary separation raw liquid, to obtain high-purity carbon tetrafluoride.

[0082] Step four, reflux ratio monitoring and control: the gas discharge and liquid return of rectification tower are detected by flow meter, and the reflux ratio change of rectification tower is calculated accordingly, and the extension amount of telescopic mass transfer part 2 is dynamically adjusted according to the reflux ratio change, to adapt to the operating condition of rectification tower.

[0083] Finally, it should be noted that the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

[0084] Although the embodiments of the present application have been shown and described, for those skilled in the art, various changes, modifications, replacements and deformations can be made to these embodiments without departing from the principles and spirits of the present application, the scope of the present application 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).

2. The carbon tetrafluoride purification system according to claim 1, characterized in that, 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.

3. The carbon tetrafluoride purification system according to claim 2, characterized in that, 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).

4. The carbon tetrafluoride purification system according to claim 3, 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).

5. The carbon tetrafluoride purification system according to claim 4, 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).

6. The carbon tetrafluoride purification system according to claim 5, 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).

7. The carbon tetrafluoride purification system according to claim 6, 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).

8. The carbon tetrafluoride purification system according to claim 2, 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.

9. 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.

10. A purification process for purifying carbon tetrafluoride using the carbon tetrafluoride purification system according to any one of claims 1-9, 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 tower (700) distillation: The original liquid from the first separation is further distilled in the high boiling tower (700). The high boiling tower (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 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 reflux ratio to adapt to the operating conditions of the distillation column.

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