Hexafluoropropylene pyrolysis gas refining device and method
By using a plate chucking tower and a silicone adsorber in the hexafluoropropylene cracking gas purification device, combining alkali chucking liquid and sulfuric acid desiccant, the ash and acid residues of the inner wall of the chucking tower during tetrafluoroethylene cracking process was solved. Problem, extending the operating cycle, reducing consumption and risks, and improving distillation effect.
Patent Information
- Application Number
- CN202411253824.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2024-12-24
AI Technical Summary
During the production of hexafluoropropylene with tetrafluoroethylene cracking, the inner walls of the cooling and acid removal process containers are prone to ash, resulting in poor cooling effect, short operating cycle, and failure to completely remove acidic substances, resulting in blockage of the tetrafluoroethylene recovery tower, increasing Raw material consumption and energy consumption, and there are safety risks.
The hexafluoropropylene cracking gas purification device combined with a plate chiller tower and a silicone adsorber is used to cool down through contact with the cracking gas through the chiller solution (5wt% sodium hydroxide solution), and water and acid mist are removed in the silicone adsorber. Using 98% sulfuric acid as the desiccant, the iccant liquid and desiccant are recycled to reduce the ash and acidic residues on the inner wall of the iccant tower.
It effectively extends the operating cycle, improves the cooling effect, reduces raw material and electricity consumption, avoids self-aggregation of tetrafluoroethylene, reduces operational risks, and improves the distillation effect of tetrafluoroethylene recovery tower.
Smart Images
Figure CN119174990A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of hexafluoropropylene production, and in particular relates to a hexafluoropropylene cracking gas refining device and method. Background Art
[0002] Hexafluoropropylene is one of the basic raw materials of organic fluorine industry, a comonomer of many fluorine-containing copolymers, and an intermediate of many fluorine-containing compounds. Hexafluoropropylene is widely produced by thermal cracking of tetrafluoroethylene, which has the advantages of simple process and high product purity. Hexafluoropropylene is produced by thermal cracking of tetrafluoroethylene: tetrafluoroethylene and octafluorocyclobutane are cracked and converted to produce hexafluoropropylene.
[0003] In the process of tetrafluoroethylene cracking to produce hexafluoropropylene, the process gas after cracking needs to be quickly quenched to end the cracking and remove the acid from the cracking gas. At present, the quenching method in the industry is mainly water quenching, that is, the process gas from the cracking reactor enters the shell-and-tube heat exchanger, which is immersed in a water tank (the water is flowing). The acid gas is mainly removed by alumina adsorption. After a period of operation, this method will cause ash to form on the inner wall of the heat exchange tube bundle of the shell-and-tube heat exchanger (ash: mainly produced by tetrafluoroethylene self-polymerization during the cracking process), and the heat exchange effect will deteriorate. The cracking reaction must be stopped regularly for replacement and maintenance, and the general operation cycle is about 30 days; the effect of alumina adsorption and acid removal is not ideal, resulting in the acidic substances produced by cracking. It cannot be completely removed, which will cause the tetrafluoroethylene recovery tower to self-polymerize due to the presence of acidic medium, causing the filler to be blocked and resulting in poor distillation effect of the tower, and the tower needs to be regularly inverted and cleaned. Frequent start and stop will increase the consumption of raw materials and energy consumption, and also increase the safety risk of operation.
[0004] Patent CN110818528A discloses a new method for removing acid in the production of hexafluoropropylene, in which tetrafluoroethylene is thermally cracked to produce hexafluoropropylene, and in the production process, the crude cracked gas of hexafluoropropylene is compressed and pre-condensed, and then enters the solid alkali deacidifier combination in the liquid phase, so that the acid formed by trace hydrogen fluoride and trace water in the crude cracked gas is completely removed before entering the distillation tower. However, this method still requires pre-condensation before deacidification, and the ash formation phenomenon during the condensation process is unavoidable. In addition, the solid alkali deacidifier combination has a complex structure, and the filling materials of solid alkali potassium hydroxide and inert porcelain balls need to be replaced regularly, and the processing steps are complicated. Summary of the invention In view of the problem that the inner wall of the quenching and acid removal process container is easy to be dusted and the acid removal effect is poor in the process of producing hexafluoropropylene by cracking tetrafluoroethylene in the prior art, the present invention provides a hexafluoropropylene cracking gas refining device and method, which solves the problem that the shell-and-tube quencher has a short operating cycle due to the poor cooling effect caused by the dust on the inner wall of the shell and tube, and the problem that the tetrafluoroethylene self-polymerization of the tetrafluoroethylene recovery tower blocks the filler due to the presence of acidic substances.
[0005] The present invention is achieved through the following technical solutions: A hexafluoropropylene cracking gas refining device, characterized in that it comprises a cracking reactor, a quenching tower, a quenching circulation tank, a quenching liquid circulation pump, a quenching liquid cooler, a cracking gas drying tower and a silica gel adsorber; The cracking reactor is connected in sequence to a quenching tower, a quenching circulation tank, a cracking gas drying tower and a silica gel adsorber; The quenching circulation tank is connected to the quenching liquid circulation pump, the quenching liquid circulation pump is connected to the quenching liquid cooler, and the quenching liquid cooler is connected to the quenching tower.
[0006] Furthermore, the quenching tower is a plate tower structure; and the cracking gas drying tower is a packed tower.
[0007] Furthermore, the plate tower is made of graphite.
[0008] Furthermore, the quenching tower and the quenching liquid cooler are provided with cooling water jackets for cooling.
[0009] Furthermore, the gas outlet at the upper end of the quenching circulation tank is connected to the cracking gas drying tower, and the liquid outlet at the lower end is connected to the quenching liquid circulation pump.
[0010] Furthermore, the cracked gas drying tower is connected to a drying tower circulation pump so that the desiccant can be circulated.
[0011] In the present invention, the method for refining hexafluoropropylene cracking gas by the device comprises the following steps: 1) Tetrafluoropropylene undergoes cracking reaction in the cracking reactor to produce cracking gas. The cracking gas enters the quenching tower and contacts with the quenching liquid in the quenching tower for adiabatic evaporation and rapid cooling. At the same time, the quenching liquid absorbs the acidic substances in the cracking gas, making the cracking gas neutral; 2) The neutral cracking gas and quenching liquid in step 1) enter the quenching circulation tank, and the gas in the quenching circulation tank enters the cracking gas drying tower, and after being dehydrated by the desiccant, enters the silica gel adsorber to further remove water and acid mist; 3) The liquid quenching liquid in the quenching circulation tank in step 2) enters the quenching liquid circulation pump, then enters the quenching liquid cooler, and enters the quenching tower after being cooled by cooling water.
[0012] Furthermore, the quenching liquid in step 1) is an alkaline solution with a mass percentage concentration of 1-10%.
[0013] Furthermore, the quenching liquid in step 1) is a sodium hydroxide solution with a mass percent concentration of 5%.
[0014] Furthermore, the desiccant in step 2) is 98% sulfuric acid.
[0015] Beneficial Effects In the present invention, the cracked gas coming out of the cracking reactor contacts with the quenching liquid in the quenching tower to be adiabatically evaporated and rapidly cooled, so that the high-temperature cracked gas is rapidly cooled from 760°C to below 100°C, and at the same time, the quenching liquid absorbs the acidic substances in the cracked gas to make the cracked gas neutral, and then passes through the drying tower and the silica gel adsorber to discharge water and remove acid before entering the next process; the problem of the shell-and-tube quencher having a poor cooling effect and a short operating cycle due to the ash deposition on the inner wall of the shell-and-tube quencher and the problem of the tetrafluoroethylene self-polymerization and plugging of the filler in the tetrafluoroethylene recovery tower due to the presence of acidic substances are solved. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a schematic diagram of a hexafluoropropylene cracking gas refining device according to the present invention; 1. Cracking reactor, 2. Quenching tower, 3. Quenching circulation tank, 4. Quenching liquid circulation pump, 5. Quenching liquid cooler, 6. Cracking gas drying tower, 7. Drying tower circulation pump, 8. Silica gel adsorber. DETAILED DESCRIPTION
[0017] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.
[0018] The schematic diagram of the hexafluoropropylene cracking gas refining device in the present invention is as follows Figure 1 As shown by Figure 1 It can be seen that the hexafluoropropylene cracking gas refining device comprises a cracking reactor 1, a quenching tower 2 (plate tower structure, the plate tower is made of graphite), a quenching circulation tank 3, a quenching liquid circulation pump 4, a quenching liquid cooler 5, a cracking gas drying tower 6 (packing tower) and a silica gel adsorber 8; the quenching tower (2) and the quenching liquid cooler (5) are provided with a cooling water jacket for cooling; the cracking reactor is connected to the quenching tower 2, the quenching circulation tank 3, the cracking gas drying tower 6 and the silica gel adsorber 8 in sequence; the quenching circulation tank 3 is connected to the quenching liquid circulation pump 4, the quenching liquid circulation pump 4 is connected to the quenching liquid cooler 5, and the quenching liquid cooler 5 is connected to the quenching tower 2.
[0019] The gas outlet at the upper end of the quenching circulation tank 3 is connected to the cracking gas drying tower 6, and the liquid outlet at the lower end is connected to the quenching liquid circulation pump 4; the cracking gas drying tower 6 is connected to the drying tower circulation pump to circulate the desiccant.
[0020] The method for refining hexafluoropropylene cracking gas is now described in conjunction with specific embodiments and drawings: Example 1 1) Tetrafluoropropylene undergoes cracking reaction in cracking reactor 1 to generate cracking gas, which enters quenching tower 2 and contacts with quenching liquid (5wt% sodium hydroxide solution) in quenching tower 2 to undergo adiabatic evaporation and rapid cooling, and at the same time, the quenching liquid absorbs the acidic substances in the cracking gas to make the cracking gas neutral; 2) The neutral cracking gas and quenching liquid in step 1) enter the quenching circulation tank 3, and the gas in the quenching circulation tank 3 enters the cracking gas drying tower 6, and after being dehydrated by the desiccant (98% sulfuric acid), enters the silica gel adsorber 8 to further remove water and acid mist; 3) The liquid quenching liquid in the quenching circulation tank 3 in step 2) enters the quenching liquid circulation pump 4, and then enters the quenching liquid cooler 5, and after being cooled by cooling water, enters the quenching tower 2 for circulation.
[0021] The hexafluoropropylene cracking gas refining device of the present invention is used to purify the hexafluoropropylene cracking gas, and the raw material consumption, the operation cycle of the tetrafluoroethylene recovery tower, and the power consumption are compared with the traditional quenching process as shown in Table 1 below: Table 1 As can be seen from Table 1, the operation cycle of refining hexafluoropropylene cracking gas by using the hexafluoropropylene cracking gas refining device of the present invention is significantly longer than the operation cycle of the traditional shell-and-tube chiller quenching method, and the raw material consumption and electric energy consumption of the device and method of the present invention are significantly lower than those of the shell-and-tube chiller quenching method.
[0022] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A hexafluoropropylene cracking gas refining device, characterized in that: It comprises a cracking reactor (1), a quenching tower (2), a quenching circulation tank (3), a quenching liquid circulation pump (4), a quenching liquid cooler (5), a cracking gas drying tower (6) and a silica gel adsorber (8); The cracking reactor is connected in sequence to a quenching tower (2), a quenching circulation tank (3), a cracking gas drying tower (6) and a silica gel adsorber (8); The quenching circulation tank (3) is connected to the quenching liquid circulation pump (4), the quenching liquid circulation pump (4) is connected to the quenching liquid cooler (5), and the quenching liquid cooler (5) is connected to the quenching tower (2).
2. The hexafluoropropylene cracking gas refining device according to claim 1, characterized in that: The quenching tower (2) is a plate tower structure; and the cracking gas drying tower (6) is a packed tower.
3. The hexafluoropropylene cracking gas refining device according to claim 1, characterized in that: The plate tower is made of graphite.
4. The hexafluoropropylene cracking gas refining device according to claim 1, characterized in that: The quenching tower (2) and the quenching liquid cooler (5) are provided with cooling water jackets for cooling.
5. The hexafluoropropylene cracking gas purification device according to claim 1, characterized in that: The gas outlet at the upper end of the quenching circulation tank (3) is connected to the cracking gas drying tower (6), and the liquid outlet at the lower end is connected to the quenching liquid circulation pump (4).
6. The hexafluoropropylene cracking gas purification device according to claim 1, characterized in that: The cracked gas drying tower (6) is connected to a drying tower circulation pump so that the desiccant can be circulated.
7. A method for refining hexafluoropropylene cracking gas using the device according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) Tetrafluoropropylene undergoes a cracking reaction in a cracking reactor (1) to generate cracking gas, and the cracking gas enters a quenching tower (2) and contacts with a quenching liquid in the quenching tower (2) to undergo adiabatic evaporation and rapid cooling, and at the same time, the quenching liquid absorbs acidic substances in the cracking gas, thereby making the cracking gas neutral; 2) The neutral cracking gas and quenching liquid in step 1) enter the quenching circulation tank (3), and the gas in the quenching circulation tank (3) enters the cracking gas drying tower (6), and after being dehydrated by the desiccant, enters the silica gel adsorber (8) to further remove water and acid mist; 3) The liquid quenching liquid in the quenching circulation tank (3) in step 2) enters the quenching liquid circulation pump (4), then enters the quenching liquid cooler (5), and enters the quenching tower (2) after being cooled by cooling water.
8. The method for refining hexafluoropropylene cracking gas according to claim 7, characterized in that: The quenching liquid in step 1) is an alkaline solution with a mass percentage concentration of 1-10%.
9. The method for refining hexafluoropropylene cracking gas according to claim 8, characterized in that: The quenching liquid in step 1) is a sodium hydroxide solution with a mass percentage concentration of 5%.
10. The method for refining hexafluoropropylene cracking gas according to claim 7, characterized in that: The desiccant in step 2) is 98% sulfuric acid.