A dehydration distillation apparatus for tetrafluoroethylene production

Abstract

This utility model relates to a dehydration and distillation apparatus for tetrafluoroethylene (TFE) production, comprising an ultra-low temperature calcium chloride dehydration system and a distillation column system. The ultra-low temperature calcium chloride dehydration system includes a dehydration column and a cooler. The upper and lower ends of the cooler are connected to the upper and lower ends of the dehydration column via pipes. The dehydration column contains an ultra-low temperature calcium chloride solution, which is used to dry the water-containing material. The cooler is used to cool the sprayed calcium chloride solution. The distillation column system includes a distillation column, a reboiler, and a condenser. The middle part of the distillation column is connected to the dehydration column via a pipe. The upper and lower ends of the reboiler are connected to the lower end of the distillation column via pipes. The upper and lower ends of the condenser are connected to the upper end of the distillation column via pipes. The distillation column is used to separate the dried material. The reboiler provides a heat source for the distillation column, and the condenser condenses the high-temperature steam at the top of the distillation column. This apparatus can improve the quality of the finished TFE product, increase the recovery and stability of by-products, and reduce material loss.

Description

Technical Field

[0001] This utility model relates to the field of chemical technology, and in particular to a dehydration distillation apparatus for the production of tetrafluoroethylene. Background Technology

[0002] Tetrafluoroethylene (TFE) and its downstream product hexafluoropropylene are the most important and fundamental fluorinated olefins among more than 10 fluorinated monomers. With the increasing number of TFE downstream products, the quality requirements and economic efficiency of TFE monomers are becoming increasingly stringent. Tetrafluoroethylene (TFE) is the core monomer for synthesizing high-performance fluoropolymers such as PTFE (polytetrafluoroethylene) and FEP (fluorinated ethylene propylene copolymer). Its purity (≥99.99%) and water content (≤100ppm) directly affect the corrosion resistance, insulation, and mechanical strength of downstream products.

[0003] The current dehydration system of the tetrafluoroethylene production plant uses an indirect cooling type of refrigerated dehydrator. After a period of use, the tubes will be blocked by high-boiling substances, requiring equipment to be switched for activation, resulting in material loss. At the same time, due to the limitations of equipment structure and refrigerant, the dehydration temperature is around -5℃, and the refrigeration dehydration effect is not good. The water content of the material entering the downstream system is around 300ppm, which is too high and can easily cause ice blockage in the distillation column.

[0004] The TFE collection in the TFE distillation column adopts a direct flow control mode, which results in a delay in the temperature response of the column bottom and an inability to provide real-time feedback on changes in the composition at the top of the column. Simple PID control cannot reflect changes in the feed and discharge rates of the distillation column and system fluctuations in a timely manner, causing the TFE collection quality to be unstable. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as material loss during equipment switching and weak dehydration capacity, by providing a dehydration distillation apparatus for tetrafluoroethylene (TFE) production. The apparatus provided by this invention can improve the quality of the finished TFE product, increase the recovery and stability of by-products, reduce material loss, and make the apparatus more economical, environmentally friendly, and competitive in the market.

[0006] The objective of this utility model can be achieved through the following technical solutions:

[0007] A dehydration distillation apparatus for tetrafluoroethylene production includes an ultra-low temperature calcium chloride dehydration system and a distillation column system.

[0008] The ultra-low temperature calcium chloride dehydration system includes a dehydration tower and a cooler. The upper and lower ends of the cooler are connected to the upper and lower ends of the dehydration tower via pipes. The dehydration tower contains an ultra-low temperature calcium chloride solution, which is used to dry the water-containing material. The cooler is used to cool the calcium chloride solution after spraying.

[0009] The distillation column system includes a distillation column, a reboiler, and a condenser. The middle part of the distillation column is connected to the dehydration column via a pipeline. The upper and lower ends of the reboiler are connected to the lower end of the distillation column via pipelines. The upper and lower ends of the condenser are connected to the upper end of the distillation column via pipelines. The distillation column is used to separate the dried material. The reboiler is used to provide a heat source for the distillation column. The condenser is used to condense the high-temperature steam at the top of the distillation column.

[0010] Furthermore, a compressor is provided between the dehydration tower and the distillation tower, and the compressor is used to transport the dried material in the dehydration tower to the distillation tower.

[0011] Furthermore, the dehydration tower is provided with a first feed pipe at the lower end and a first discharge pipe at the upper end. The first feed pipe is used to transport the water-containing material into the dehydration tower, and the first discharge pipe is used to transport the dried material into the distillation tower.

[0012] Furthermore, a circulation pump is installed on the pipe connecting the lower end of the dehydration tower and the lower end of the cooler.

[0013] Furthermore, the ultra-low temperature calcium chloride dehydration system also includes an evaporator, the lower end of which is connected to a cooler via a pipe, and the upper end of which is connected to the lower end of a dehydration tower via a pipe. The evaporator is used to absorb water from the calcium chloride solution.

[0014] Furthermore, the evaporator is equipped with a steam heating jacket.

[0015] Furthermore, the evaporator is externally connected to a vacuum pump at its top, which is used to create negative pressure in the evaporator.

[0016] Furthermore, the distillation column is provided with a second feed pipe at the lower end and a second discharge pipe at the upper end. The second feed pipe is used to transport the dried material into the distillation column, and the second discharge pipe is used to collect the separated tetrafluoroethylene product.

[0017] Furthermore, the distillation column is also equipped with a sensitive plate, which is connected to the second feed pipe, the second discharge pipe, the reboiler, and the condenser.

[0018] Furthermore, the sensitive plate is equipped with a temperature sensor, which is used to measure the temperature inside the distillation column.

[0019] There is a certain difference between the feed pipe temperature and the feed temperature inside the distillation column. Changes in the feed rate will affect the feed temperature. An increase in the collection rate will cause the heavy components in the column bottom to rise, thereby causing the temperature of the sensitive plate to rise. The heavy components rising to the upper section of the distillation column will cause changes in the composition at the collection port at the top of the column.

[0020] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0021] 1. This utility model allows the low-temperature calcium chloride solution to directly contact the material and absorb moisture, which can improve the water absorption effect and water absorption capacity by about 35%. Continuous operation of the equipment without switching can reduce material loss by about 400 Nm. 3 .

[0022] 2. Existing control schemes for TFE collection in TFE distillation columns are single-loop control systems using pneumatic valves to control the collection flow rate. The composition in the distillation column bottom is relatively stable and insensitive to temperature changes, making it unsuitable as an optimal reference value for the top collection component and quantity. This invention adds a sensitive plate temperature point in the lower part of the distillation column to the existing collection system. The temperature of this sensitive plate changes with any of the following parameters: feed rate, feed temperature, collection quantity, collected component, and bottom component. This provides immediate feedback on the overall operation of the distillation column. Based on the temperature change of the sensitive plate caused by changes in the feed rate, this invention cascades the bottom heating and top reflux flow rate to maintain the temperature change within a controlled range. The top collection quantity is then adjusted based on the temperature change to ensure stable distillation performance and high-quality TFE collection. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the dehydration distillation apparatus used in the production of tetrafluoroethylene in this utility model.

[0024] Figure 2 This is a schematic diagram of the ultra-low temperature calcium chloride dehydration system of this utility model.

[0025] Figure 3 This is a schematic diagram of the distillation column system in this utility model.

[0026] Explanation of the attached diagram numbers: 1. First feed pipe, 2. First discharge pipe, 3. Dehydration tower, 4. Cooler, 5. Circulating pump, 6. Evaporator, 7. Vacuum pump, 8. Steam heating jacket, 9. Distillation column, 10. Sensitive plate, 11. Second feed pipe, 12. Second discharge pipe, 13. Reboiler, 14. Condenser, 15. Compressor. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. This embodiment is based on the technical solution of the present invention and provides detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] In the description of this utility model, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this utility model. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0031] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] Example 1

[0033] See Figure 2 This embodiment provides a continuously operating, automatic water absorption / dehydration system for ultra-low temperature calcium chloride. The ultra-low temperature calcium chloride dehydration system includes a dehydration tower 3 and a cooler 4. The upper and lower ends of the cooler 4 are connected to the upper and lower ends of the dehydration tower 3 through pipes. The dehydration tower 3 contains an ultra-low temperature calcium chloride solution, which is used to dry water-containing materials. The cooler 4 is used to cool the calcium chloride solution after spraying.

[0034] The first feed pipe 1 is used to transport the water-containing material into the dehydration tower 3, the ultra-low temperature calcium chloride solution is used to dry the water-containing material, and the first discharge pipe 2 is used to transport the dried material to;

[0035] The upper and lower ends of the cooler 4 are respectively connected to the upper and lower ends of the dehydration tower 3 through pipes. The cooler 4 is used to cool the calcium chloride solution after spraying.

[0036] Furthermore, a compressor 15 is provided between the dehydration tower 3 and the distillation tower 9, and the compressor 15 is used to transport the dried material in the dehydration tower 3 to the distillation tower 9.

[0037] Furthermore, the dehydration tower 3 is provided with a first feed pipe 1 at its lower end and a first discharge pipe 2 at its upper end. The first feed pipe 1 is used to transport the water-containing material into the dehydration tower 3, and the first discharge pipe 2 is used to transport the dried material into the distillation tower 9.

[0038] Furthermore, a circulation pump 5 is installed on the pipe connecting the lower end of the dehydration tower 3 and the lower end of the cooler 4.

[0039] Furthermore, the ultra-low temperature calcium chloride dehydration system also includes an evaporator 6, the lower end of which is connected to the cooler 4 via a pipe, and the upper end of which is connected to the lower end of the dehydration tower 3 via a pipe. The evaporator 6 is used to absorb water from the calcium chloride solution.

[0040] Furthermore, the evaporator 6 is provided with a steam heating jacket 8.

[0041] Furthermore, the evaporator 6 is externally connected to a vacuum pump 7, which is used to draw negative pressure into the evaporator 6.

[0042] Comparative Example 1

[0043] This comparative example provides an indirect cooling freeze dehydrator, model number 17V393R, with dimensions of Ф1000×4500. The operating conditions of the freeze dehydrator are: wet material flows through the tube side, calcium chloride brine at approximately -10℃ flows through the shell side, and the material temperature at the equipment outlet is maintained at -5℃.

[0044] The performance of the ultra-low temperature calcium chloride dehydration system provided in Example 1 and the indirect cooling cryogenic dehydrator provided in Comparative Example 1 were tested, and the specific details are shown in Tables 1 and 2.

[0045] Table 1. Comparison of Process Parameters

[0046]

[0047] Table 2 Performance Test Comparison Table

[0048]

[0049] The cryogenic calcium chloride dehydration system provided in Example 1 has a dehydration efficiency that is 95-70 / 70 = 35% higher than that of the indirect-cooled cryogenic dehydrator provided in Comparative Example 1. The indirect-cooled cryogenic dehydrator provided in Comparative Example 1 loses 2 Nm³ of material per switching operation. 3The dehydrator needs to be switched every 1.5 days. Assuming a capacity of 300 units per year, this requires 200 switches, totaling 2 * 200 = 400 Nm. 3 .

[0050] Therefore, the ultra-low temperature calcium chloride dehydration system provided by this utility model uses ultra-low temperature calcium chloride solution to directly spray and cool high moisture materials, reducing the control temperature of the dehydration system from -5℃ to -20℃, reducing the process control temperature and improving the dehydration capacity of the dehydration system, so that the moisture content of the material decreases from 300ppm to about 50ppm.

[0051] Meanwhile, the ultra-low temperature calcium chloride dehydration system provided by this utility model is also equipped with a high-temperature, negative-pressure evaporation component. A portion of the calcium chloride solution that has absorbed water is transported to the evaporator. By controlling the temperature and negative pressure, all the water absorbed by the dehydration tower solution per unit time is evaporated. The remaining calcium chloride solution in the evaporator is returned to the dehydration tower for continued circulation, realizing automatic treatment of the water absorbed by the dehydration system, maintaining a stable concentration of calcium chloride solution in the entire system, ensuring continuous operation of the equipment, eliminating the need to switch to standby equipment, and reducing material loss.

[0052] Example 2

[0053] See Figure 3 This embodiment provides a distillation column system, which includes a distillation column 9, a reboiler 13, and a condenser 14. The middle part of the distillation column 9 is connected to the dehydration column 3 through a pipe. The upper and lower ends of the reboiler 13 are connected to the lower end of the distillation column 9 through pipes. The upper and lower ends of the condenser 14 are connected to the upper end of the distillation column 9 through pipes. The distillation column 9 is used to separate the dried material. The reboiler 13 is used to provide a heat source for the distillation column 9. The condenser 14 is used to condense the high-temperature steam at the top of the distillation column 9.

[0054] Furthermore, the distillation column 9 is provided with a second feed pipe 11 at the lower end and a second discharge pipe 12 at the upper end. The second feed pipe 11 is used to transport the dried material into the distillation column 9, and the second discharge pipe 12 is used to collect the separated tetrafluoroethylene product.

[0055] Furthermore, the distillation column 9 is also equipped with a sensitive plate 10, which is connected to the second feed pipe 11, the second discharge pipe 12, the reboiler 13, and the condenser 14.

[0056] Furthermore, the sensitive plate 10 is equipped with a temperature sensor, which is used to measure the temperature inside the distillation column 9.

[0057] Comparative Example 2

[0058] This comparative example provides a TFE distillation column, which is a single-loop control system for controlling the collection flow rate with a pneumatic valve. The TFE distillation column is model S2019-33, and its specifications are Ф800×40317. The operating conditions of the TFE distillation column are: pressure 0.98 MPaG, temperature 18℃; the design conditions are: pressure 2 MPaG, temperature 100℃.

[0059] The performance of the distillation column system provided in Example 2 and the TFE distillation column provided in Comparative Example 2 were tested, and the specific details are shown in Table 3.

[0060] Table 3 Performance Test Comparison Table

[0061]

[0062]

[0063] The results are shown in Table 3. After optimizing the control scheme, the purity of TFE was ensured to be above 99.99%, while the unit consumption decreased from 1.847 to 1.845.

[0064] This invention adds a sensitive plate temperature point in the lower part of the distillation column to the existing distillation column collection system. The temperature of the sensitive plate changes with any one of the following parameters: feed rate, feed temperature, collection rate, collected components, and reboiler components. This provides immediate feedback on the overall operation of the distillation column. Based on the temperature change of the sensitive plate caused by changes in the feed rate, this invention uses cascade control of the reboiler heating and top reflux flow rate to maintain the temperature change within a controlled range. Furthermore, it adjusts the top collection rate based on the temperature changes to ensure stable distillation performance and high TFE collection quality.

[0065] The above description of the embodiments is provided to enable those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present utility model is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present utility model without departing from its scope should be within the protection scope of the present utility model.

Claims

1. A dehydration distillation apparatus for the production of tetrafluoroethylene, characterized in that, Including a cryogenic calcium chloride dehydration system and a distillation column system, The ultra-low temperature calcium chloride dehydration system includes a dehydration tower (3) and a cooler (4). The upper and lower ends of the cooler (4) are connected to the upper and lower ends of the dehydration tower (3) through pipes. The dehydration tower (3) contains an ultra-low temperature calcium chloride solution, which is used to dry materials containing water. The cooler (4) is used to cool the calcium chloride solution after spraying. The distillation column system includes a distillation column (9), a reboiler (13), and a condenser (14). The middle part of the distillation column (9) is connected to the dehydration column (3) through a pipe. The upper and lower ends of the reboiler (13) are connected to the lower end of the distillation column (9) through pipes. The upper and lower ends of the condenser (14) are connected to the upper end of the distillation column (9) through pipes. The distillation column (9) is used to separate the dried material. The reboiler (13) is used to provide a heat source for the distillation column (9). The condenser (14) is used to condense the high-temperature steam at the top of the distillation column (9).

2. The dehydration distillation apparatus for tetrafluoroethylene production according to claim 1, characterized in that, A compressor (15) is provided between the dehydration tower (3) and the distillation tower (9), and the compressor (15) is used to transport the dried material in the dehydration tower (3) to the distillation tower (9).

3. The dehydration distillation apparatus for tetrafluoroethylene production according to claim 1, characterized in that, The dehydration tower (3) is provided with a first feed pipe (1) at the lower end and a first discharge pipe (2) at the upper end. The first feed pipe (1) is used to transport the water-containing material into the dehydration tower (3) and the first discharge pipe (2) is used to transport the dried material into the distillation tower (9).

4. The dehydration distillation apparatus for tetrafluoroethylene production according to claim 1, characterized in that, A circulation pump (5) is installed on the pipe connecting the lower end of the dehydration tower (3) and the lower end of the cooler (4).

5. A dehydration distillation apparatus for tetrafluoroethylene production according to claim 1, characterized in that, The ultra-low temperature calcium chloride dehydration system also includes an evaporator (6), the lower end of which is connected to a cooler (4) via a pipe, and the upper end of which is connected to the lower end of a dehydration tower (3) via a pipe. The evaporator (6) is used to absorb water from the calcium chloride solution.

6. A dehydration distillation apparatus for tetrafluoroethylene production according to claim 5, characterized in that, The evaporator (6) is equipped with a steam heating jacket (8).

7. A dehydration distillation apparatus for tetrafluoroethylene production according to claim 6, characterized in that, The top of the evaporator (6) is connected to a vacuum pump (7), which is used to draw negative pressure into the evaporator (6).

8. A dehydration distillation apparatus for tetrafluoroethylene production according to claim 1, characterized in that, The distillation column (9) is provided with a second feed pipe (11) at the lower end and a second discharge pipe (12) at the upper end. The second feed pipe (11) is used to transport the dried material into the distillation column (9) and the second discharge pipe (12) is used to collect the separated tetrafluoroethylene product.

9. A dehydration distillation apparatus for tetrafluoroethylene production according to claim 7, characterized in that, The distillation column (9) is also equipped with a sensitive plate (10), which is connected to the second feed pipe (11), the second discharge pipe (12), the reboiler (13) and the condenser (14).

10. A dehydration distillation apparatus for tetrafluoroethylene production according to claim 9, characterized in that, The sensitive plate (10) is equipped with a temperature sensor, which is used to measure the temperature inside the distillation column (9).

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