Purification device for recycling modified polytetrafluoroethylene kettle gas

Abstract

The utility model discloses a purification device for recycling modified polytetrafluoroethylene kettle gas, which is characterized in that a polymerization tail gas inlet (7) is arranged at a top inlet of an alkaline washing tank (1), a top outlet of the alkaline washing tank (1) is communicated with a bottom inlet of a cooler (2), and a top outlet of the cooler (2) is communicated with a side surface inlet of a gas-liquid separator (3); a top outlet of the gas-liquid separator (3) is communicated with an inlet of the compression buffer tank (4) through an adsorption device, an outlet of the compression buffer tank (4) is communicated with a side inlet of the rectifying tower (6) through the membrane press (5), a top outlet of the rectifying tower (6) is a gas outlet (8), a coiled impurity discharge pipe (15) is arranged at the bottom of the rectifying tower (6), one end of the impurity discharge pipe (15) is communicated with the inside of the rectifying tower, and the other end of the impurity discharge pipe (15) is communicated with the inside of the membrane press (5). And the other end of the impurity discharge pipe (15) is an impurity outlet (9). According to the utility model, the high-concentration tetrafluoroethylene / perfluoromethyl vinyl ether replenishment mixed gas is prepared.

Description

Technical Field

[0001] The utility model relates to a purification device for recovering modified polytetrafluoroethylene kettle gas. Background Art

[0002] Modified polytetrafluoroethylene is generally obtained by copolymerizing tetrafluoroethylene with other modified olefin monomers. The modified monomers include vinylidene fluoride, hexafluoropropylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, chlorotrifluoroethylene, etc., to obtain modified resins with different performance requirements. This time we are targeting polytetrafluoroethylene modified with perfluoromethyl vinyl ether (PMVE).

[0003] Modified polytetrafluoroethylene is generally reacted by initially and supplementing the TFE / PMVE mixture. After the reaction is completed, the unreacted kettle gas is treated with a series of processes to remove residual initiators and moisture, and then enters the supplement tank for recycling and continued use. These processes cannot effectively remove the by-product impurities produced in the reaction, such as octafluorocyclobutane (C318). After repeated recycling, the impurity content in the supplement tank will become higher and higher, seriously affecting the polymerization quality. Therefore, when the impurity content in the recovered gas is close to a certain amount, it needs to be purified. The current common method is to return the recovered gas to the TFE monomer device for distillation, but the amount of recovered gas is not large, of which the TFE composition content is about 25%. The remaining more than ten kilograms of PMVE are not worth recycling compared to its negligible output in the large TFE production device. PMVE is expensive and wasteful. Therefore, a separate device is needed to distill and purify it, and it can also purify the tail gas of other polymerization devices using polytetrafluoroethylene (PTFE), polyperfluoropropylene (FEP), polyvinylidene fluoride (PVDF) or fluororubber (FKM). Utility Model Content

[0004] The utility model provides a purification device for recovering modified polytetrafluoroethylene kettle gas, which can prepare high-concentration tetrafluoroethylene / perfluoromethyl vinyl ether supplementary mixed gas.

[0005] The utility model adopts the following technical scheme: a purification device for recovering modified polytetrafluoroethylene kettle gas, which mainly comprises an alkali washing tank, a cooler, a gas-liquid separator, an adsorption device, a compression buffer tank, a membrane press and a distillation tower, wherein the top inlet of the alkali washing tank is arranged as a polymerization tail gas inlet, the top outlet of the alkali washing tank is connected with the bottom inlet of the cooler, the top outlet of the cooler is connected with the side inlet of the gas-liquid separator, the top outlet of the gas-liquid separator is connected with the inlet of the compression buffer tank through the adsorption device, the outlet of the compression buffer tank is connected with the side inlet of the distillation tower through the membrane press, the top outlet of the distillation tower is a gas outlet, and a coiled impurity discharge pipe is arranged at the bottom of the distillation tower, one end of the impurity discharge pipe is connected with the inside of the distillation tower, and the other end of the impurity discharge pipe is an impurity outlet.

[0006] Furthermore, the adsorption device comprises a plurality of adsorption columns which are connected in series and each of which is provided with adsorption material.

[0007] Furthermore, the adsorption material is silica gel, molecular sieve, solid alkali or concentrated sulfur acid.

[0008] Furthermore, the distillation tower is configured as a plate tower, and a plurality of plates are distributed from top to bottom inside the distillation tower, and through holes are distributed on each plate. The plates divide the distillation tower into a plurality of compartments, and the compartments are connected through the through holes, and a distillation filler is provided in each compartment.

[0009] Furthermore, the distillation packing is metal Dixon packing, metal Ball ring packing or metal structured packing.

[0010] The utility model has the following beneficial effects: after adopting the above technical scheme, the utility model recovers the kettle gas generated by the modified polytetrafluoroethylene, and the adopted purification device can realize the refining and polymerization of the recovered kettle gas. The whole purification device includes an alkali washing tank, a cooler, a gas-liquid separator, an adsorption device, a compression buffer tank, a membrane press and a distillation tower, so that the initiator can be removed by alkali washing, freezing, adsorption and dehydration, and then pressurized into the distillation tower to remove impurities, so as to obtain a supplementary mixed gas of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) with a concentration of> 99.99%. In addition, the purification device equipment adopted by the utility model has a relatively simple structure and is relatively easy to install. Since the adopted parts are not large in size, the space occupied is relatively small. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the utility model patent or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model patent. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 It is a structural schematic diagram of the utility model. DETAILED DESCRIPTION

[0013] The preferred embodiments of the present utility model patent are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present utility model patent can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present utility model patent.

[0014] exist Figure 1The utility model provides a purification device for recovering modified polytetrafluoroethylene kettle gas, which mainly includes an alkali washing tank 1, a cooler 2, a gas-liquid separator 3, an adsorption device, a compression buffer tank 4, a membrane press 5 and a distillation tower 6. The top inlet of the alkali washing tank 1 is set as a polymerization tail gas inlet 7, the top outlet of the alkali washing tank 1 is connected to the bottom inlet of the cooler 2, the top outlet of the cooler 2 is connected to the side inlet of the gas-liquid separator 3, the top outlet of the gas-liquid separator 3 is connected to the inlet of the compression buffer tank 4 through the adsorption device, the outlet of the compression buffer tank 4 is connected to the side inlet of the distillation tower 6 through the membrane press 5, the top outlet of the distillation tower 6 is a gas outlet 8, and the bottom of the distillation tower 6 is provided with a coiled impurity discharge pipe 15, one end of the impurity discharge pipe 15 is connected to the inside of the distillation tower, and the other end of the impurity discharge pipe 15 is an impurity outlet 9. The adsorption device includes a plurality of adsorption columns 10. This embodiment adopts The adsorption device used includes three adsorption columns 10, which are connected in series with each other. An adsorption material 11 is arranged in each adsorption column 10. The adsorption material 11 is silica gel, molecular sieve, solid alkali or concentrated sulfur acid. The adsorption material 11 of this embodiment is molecular sieve. The distillation tower 6 is configured as a plate tower. A plurality of plates 12 are distributed from top to bottom in the distillation tower 6. Ninety-two plates 12 are distributed from top to bottom in the distillation tower 6 of this embodiment. Through holes are distributed on each plate 12. The plates 12 divide the distillation tower into a plurality of partitions 13. The plates 12 of this embodiment divide the distillation tower into ninety-three partitions 13. The partitions 13 are connected through through holes. A distillation filler 14 is arranged in each partition 13. The distillation filler 14 is a metal Dixon filler, a metal ball ring filler or a metal structured filler. The distillation filler 14 of this embodiment is a metal ball ring filler.

[0015] The use process of the utility model is as follows: firstly, the polymerization tail gas of modified polytetrafluoroethylene is collected, and the polymerization tail gas of modified polytetrafluoroethylene is discharged into an alkali washing tank 1, and the initiator in the tail gas is removed after alkali washing by the alkali solution in the alkali washing tank 1, and the alkali solution in step 1 is a 10% potassium hydroxide or sodium hydroxide solution; then the tail gas after alkali washing enters a cooler 2 for freeze dehydration; the tail gas after freeze dehydration is passed through a gas-liquid separator 3 again to separate gas and liquid, and the separated tail gas and liquid pass through a plurality of adsorption columns 10, and after the adsorption column 10 adsorbs the liquid, the tail gas is discharged into a compression buffer tank 4 for compression at a pressure of 0.15MPa Then, after being compressed by the membrane press 5, it enters the distillation tower 6 and is filtered and separated by the tower plate 12 and the distillation filler 14, and the added mixed gas of tetrafluoroethylene and perfluoromethyl vinyl ether is discharged through the gas outlet 8 at the top of the distillation tower 6. The added mixed gas of tetrafluoroethylene and perfluoromethyl vinyl ether is >99.99%, which meets the requirements for the use of FEP polymerization. Tetrafluoroethylene or perfluoromethyl vinyl ether and the trace impurities pentafluoroethane or octafluorocyclobutane generated during the polymerization are discharged from the impurity outlet 9 at the bottom of the distillation tower 6. The top temperature of the distillation tower 6 is 25°C, the reflux ratio is 4, the bottom temperature is 64°C, and the pressure in the distillation tower 6 is 1.3MPa.

[0016] Without limitation to this, any changes or substitutions that are not conceived through creative work should be included in the protection scope of this utility model patent. Therefore, the protection scope of this utility model patent should be based on the protection scope defined in the claims.

Claims

1. A purification device for recovering the kettle gas of modified polytetrafluoroethylene, characterized in that It mainly comprises an alkali washing tank (1), a cooler (2), a gas-liquid separator (3), an adsorption device, a compression buffer tank (4), a membrane press (5) and a distillation tower (6). The top inlet of the alkali washing tank (1) is arranged as a polymerization tail gas inlet (7). The top outlet of the alkali washing tank (1) is connected to the bottom inlet of the cooler (2). The top outlet of the cooler (2) is connected to the side inlet of the gas-liquid separator (3). The top outlet of the gas-liquid separator (3) is connected to the inlet of the compression buffer tank (4) through the adsorption device. The outlet of the compression buffer tank (4) is connected to the side inlet of the distillation tower (6) through the membrane press (5). The top outlet of the distillation tower (6) is a gas outlet (8). A coiled impurity discharge pipe (15) is arranged at the bottom of the distillation tower (6). One end of the impurity discharge pipe (15) is connected to the inside of the distillation tower. The other end of the impurity discharge pipe (15) is an impurity outlet (9).

2. The purification device for recovering the modified polytetrafluoroethylene kettle gas according to claim 1, characterized in that The adsorption device comprises a plurality of adsorption columns (10), wherein the plurality of adsorption columns (10) are connected in series and combined with each other, and an adsorption material (11) is provided in each adsorption column (10).

3. The purification device for recovering the modified polytetrafluoroethylene kettle gas according to claim 2, characterized in that The adsorption material (11) is silica gel, molecular sieve, solid alkali or concentrated sulfur acid.

4. The purification device for recovering the modified polytetrafluoroethylene kettle gas according to claim 1, characterized in that The distillation tower (6) is configured as a plate tower, wherein a plurality of tower plates (12) are distributed from top to bottom inside the distillation tower (6), each tower plate (12) is provided with through holes, the tower plates (12) divide the inside of the distillation tower into a plurality of partitions (13), the partitions (13) are connected via the through holes, and a distillation filler (14) is provided in each partition (13).

5. The purification device for recovering the modified polytetrafluoroethylene kettle gas according to claim 4, characterized in that The distillation packing (14) is a metal Dixon packing, a metal Ball ring packing or a metal structured packing.

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