A kind of method of removing impurity in the tetrafluoroethylene
Technical field
The present invention relates to chemical field, specifically, relate to a kind of method of removing impurity in the tetrafluoroethylene.
Background technology
Difluorochloromethane (CHClF
2, below be referred to as F
22) cracking generates needs in the technology of tetrafluoroethylene through with lower unit: the cracking unit, the Disacidifying and dewatering unit, compressed element, rectification cell obtains the higher tetrafluoroethylene monomer of purity (its process flow sheet is seen accompanying drawing one) at last, in the cracking unit, F
22Thermo-cracking generates tetrafluoroethylene (C
2F
4) monomer, generate a certain amount of impurity simultaneously as carbon monoxide, vinylidene, trifluoro-ethylene, methylene fluoride, trifluoromethane, its reaction equation is as follows:
CHClF
2+ H
2O-→ C
2F
4+ C
2H
2F
2+ C
2HF
3+ CF
2H
2+ CF
3H+CHClF
2+ CO+ other.
In the cracking material, be dissolved with rare gas elementes such as oxygen, nitrogen, remove simultaneously in the acid unit is that water, alkali are removed the acid that reaction generates, owing to all be dissolved with rare gas elementes such as oxygen, nitrogen in the materials such as water, alkali, therefore rare gas element water-soluble, alkali also enters production system in these unit; At compressed element, because the import of compressor may form negative pressure, the micro-air in the environment will enter system.Based on above reason, contain gases such as a certain amount of oxygen nitrogen, carbon monoxide, vinylidene, trifluoro-ethylene, methylene fluoride, trifluoromethane in the whole production system.Because the tetrafluoroethylene activity is stronger, easy and tetrafluoroethylene reaction generation explosive substance when oxygen level reaches finite concentration, have a strong impact on the safety in production of tetrafluoroethylene, and if rare gas element accumulates low in system, then the working pressure of total system also can raise, and whole production system can't be moved continuously; If materials such as fluorine-containing impurity such as vinylidene, trifluoro-ethylene, methylene fluoride, trifluoromethane accumulate, will have a strong impact on the quality product of tetrafluoroethylene in addition in system.Therefore the tetrafluoroethylene production system must efflux rare gas element and fluorine-containing foreign gases such as deoxygenation nitrogen, carbon monoxide continuously to system, with the continuous safe operation of guaranteeing total system and the quality product of tetrafluoroethylene.Because tetrafluoroethylene and rare gas element and foreign gas are not easily separated, so contain a large amount of tetrafluoroethylene gas in institute's exhaust body, it is formed as table 1.
Table 1
The component title |
Tetrafluoroethylene |
Methylene fluoride |
Trifluoromethane |
Carbon monoxide |
Other |
Mass content % |
92.18 |
0.20 |
0.80 |
4.58 |
2.24 |
As can be seen from Table 1: contain a large amount of tetrafluoroethylene in institute's exhaust body, at present, in the tetrafluoroethylene production equipment, the quantity discharged of tetrafluoroethylene is about 1.5% of monomer output in institute's exhaust body, a large amount of tetrafluoroethylene is discharged in the air will cause certain environmental pollution, and therefore reclaiming tetrafluoroethylene has favorable economic benefit and social benefit.
About the report that reclaims tetrafluoroethylene from emission gases seldom, it is to utilize F that a kind of method is arranged at present
113Methyl alcohol, chloroform, the glycol dimethyl ether equal solvent is made extraction agent, the method of utilizing extracting rectifying is fluoro-gas such as tetrafluoroethylene, methylene fluoride, trifluoromethane, vinylidene, trifluoro-ethylene and rare gas element such as carbon monoxide, oxygen, nitrogen separately, the rectifying of fluoro-gas retrieval system gets tetrafluoroethylene, but there is following distinct disadvantage in this method: though 1. this method is isolated system to rare gas element, but this method is not with fluorine-containing foreign gas such as methylene fluoride, trifluoromethane, vinylidene, the trifluoro-ethylene separation system, fluorine-containing foreign gas is in systemic circulation and accumulation, when being accumulated to the quality that will have a strong impact on tetrafluoroethylene monomer when a certain amount of.2.F
113In use can enter in the atmosphere with emptying end gas, and F
113Because of the use that is under an embargo at present of havoc atmospheric ozone layer, with F
113The use that is under an embargo, this technology can not re-use.Solvent boiling point height, operation energy consumption height, corrodibility is strong, toxicity is big, it is high that material is required, therefore for guaranteeing the long period safe operation of tetrafluoroethylene production system, must seek the high novel solvent of Paratetrafluoroethylene selectivity and overcome above-mentioned shortcoming, adopting novel solvent is emphasis of the present invention.
Summary of the invention
The method that the purpose of this invention is to provide impurity in a kind of removal tetrafluoroethylene that is suitable for industrial applications.
In order to have realized purpose of the present invention, the invention provides a kind of method of removing impurity in the tetrafluoroethylene, comprise the steps: impure tetrafluoroethylene gas by after the degassing tower fore-running, enter extractive distillation column rectifying, extraction agent is one or more in alcohols, ketone, chloroform or the Perfluorocyclobutane oligopolymer, the rare gas element of extracting rectifying column overhead directly goes burning disposal, the component of extracting rectifying Tata still gained is directly returned the tetrafluoroethylene production system after by the desorption tower desorb, and rectifying gets tetrafluoroethylene monomer again.
The production process of tetrafluoroethylene comprises cracking unit, compressed element, the whole process of rectification cell in the prior art, the foreign gas that discharging contains tetrafluoroethylene is the three wastes gas in the tetrafluoroethylene production process, owing to contain a large amount of tetrafluoroethylene in this gas, therefore along with the discharging of foreign gas, the tetrafluoroethylene loss is bigger, the purpose of this patent is exactly to reclaim the tetrafluoroethylene of loss, but the tetrafluoroethylene that reclaims can not also need further refining directly as the product use.Owing in the tetrafluoroethylene production process rectification cell is arranged, there is no need to establish again the tetrafluoroethylene that the independent rectifying of a cover rectifier unit is reclaimed, the present invention be the tetrafluoroethylene that will reclaim directly return tetrafluoroethylene that the rectification cell in the tetrafluoroethylene production process produces with cracking together rectifying obtain tetrafluoroethylene.This is a working cycle, will produce impure gas during rectifying continuously and simultaneously also obtain the tetrafluoroethylene product continuously, and the tetrafluoroethylene that reclaims in the foreign gas returns distillation system rectifying again continuously.
Wherein, containing after the foreign gas fore-running of tetrafluoroethylene preferably, the flow with 50~150kg/h enters extractive distillation column rectifying.
Wherein, described extraction agent alcohols is preferably C
1~C
4Lower alcohol, ketone is preferably C
1~C
4Lower ketones.
Wherein, the filler of extractive distillation column is preferably the special network of metal English and restrains this filler, metal Pall ring granular filler or metal structured packing.
Wherein, liquid-gas ratio is preferably 10~0.5: 1, and liquid-gas ratio is an extraction agent and the volume ratio of the identical dimensional unit of the gas that enters extractive distillation column, for example rise/liter.
Wherein, the specific liquid rate of extractive distillation column is preferably 10~50m
3/ (m
2.h), the spray temperature is preferably-20~20 ℃.
Wherein, the pressure of extractive distillation column is preferably 0.1~1.0Mpa.
Wherein, the pressure of Analytic Tower is preferably 0.01~0.8Mpa.The tower top temperature of Analytic Tower is preferably-20~20 ℃, and tower still temperature is preferably 20~100 ℃.
The present invention is because of increasing the second-stage treatment system newly and selecting for use with the double solvents of alcohols, ketone, chloroform, Perfluorocyclobutane oligopolymer equal solvent and make extraction agent, effectively removed other fluorine-containing impurity, reached the purpose that not only can reclaim tetrafluoroethylene but also can remove fluorine-containing impurity, avoid fluorine-containing impurity in system, to circulate, guaranteed the stable of tetrafluoroethylene quality product.Present method turndown ratio is big, and technical process is short, and the extraction agent boiling point is relatively low, low toxicity, low-corrosiveness, low price, less demanding to material, and running cost is low, invest little, so suitable suitability for industrialized production of present method.
Description of drawings
Remove the schema of impurity in Fig. 1 tetrafluoroethylene tail gas.
Embodiment
Following examples are used to illustrate the present invention, but are not used for limiting the scope of the invention.
Embodiment 1
A kind of method of removing impurity in the tetrafluoroethylene, with impure tetrafluoroethylene gas by after the degassing tower fore-running, flow with 50kg/h enters extractive distillation column rectifying, extraction agent is a methyl alcohol, the fluorine-containing foreign gas of extracting rectifying column overhead is directly gone burning disposal, the component of extracting rectifying Tata still gained is directly returned the tetrafluoroethylene production system after by the desorption tower desorb, obtains tetrafluoroethylene monomer after the rectifying.The filler of described extractive distillation column is that the special network of metal English restrains this filler.During described extracting rectifying, liquid-gas ratio is 10: 1.During described extracting rectifying, the specific liquid rate of extractive distillation column is 10m
3/ (m
2.h), the spray temperature is-20 ℃.During described extracting rectifying, the pressure of extractive distillation column is 0.1Mpa.The tower top temperature of extractive distillation column is-20 ℃, and tower still temperature is 20 ℃.During described desorb rectifying, the pressure of Analytic Tower is 0.01Mpa, and the tower top temperature of Analytic Tower is-20 ℃, and tower still temperature is 20 ℃.
Embodiment 2
A kind of method of removing impurity in the tetrafluoroethylene, with impure tetrafluoroethylene gas by after the degassing tower fore-running, flow with 100kg/h enters extractive distillation column rectifying, extraction agent is an acetone, the fluorine-containing foreign gas of extracting rectifying column overhead is directly gone burning disposal, the component of extracting rectifying Tata still gained is directly returned the tetrafluoroethylene production system after by the desorption tower desorb, obtains tetrafluoroethylene monomer after the rectifying.The filler of described extractive distillation column is a metal Pall ring granular filler.During described extracting rectifying, liquid-gas ratio is 5: 1.During described extracting rectifying, the specific liquid rate of extractive distillation column is 30m
3/ (m
2.h), the spray temperature is 0 ℃.During described extracting rectifying, the pressure of extractive distillation column is 0.5Mpa.The tower top temperature of extractive distillation column is 0 ℃, and tower still temperature is 60 ℃.During described desorb rectifying, the pressure of Analytic Tower is 0.1Mpa, and the tower top temperature of Analytic Tower is 0 ℃, and tower still temperature is 60 ℃.
Embodiment 3
A kind of method of removing impurity in the tetrafluoroethylene, with impure tetrafluoroethylene gas by after the degassing tower fore-running, flow with 150kg/h enters extractive distillation column rectifying, extraction agent is a chloroform, the fluorine-containing foreign gas of extracting rectifying column overhead is directly gone burning disposal, the component of extracting rectifying Tata still gained is directly returned the tetrafluoroethylene production system after by the desorption tower desorb, obtains tetrafluoroethylene monomer after the rectifying.The filler of described extractive distillation column is a metal structured packing.When described extracting rectifying, liquid-gas ratio is 0.5: 1.During described extracting rectifying, the specific liquid rate of extractive distillation column is 50m
3/ (m
2.h), the spray temperature is 20 ℃.During described extracting rectifying, the pressure of extractive distillation column is 1.0Mpa.The tower top temperature of extractive distillation column is 20 ℃, and tower still temperature is 100 ℃.During described desorb rectifying, the pressure of Analytic Tower is 0.8Mpa, and the tower top temperature of Analytic Tower is 20 ℃, and tower still temperature is 100 ℃.
Embodiment 4
A kind of method of removing impurity in the tetrafluoroethylene, with impure tetrafluoroethylene gas by after the degassing tower fore-running, flow with 100kg/h enters extractive distillation column rectifying, extraction agent is a Perfluorocyclobutane, the fluorine-containing foreign gas of extracting rectifying column overhead is directly gone burning disposal, the component of extracting rectifying Tata still gained is directly returned the tetrafluoroethylene production system after by the desorption tower desorb, obtains tetrafluoroethylene monomer after the rectifying.The filler of described extractive distillation column is a metal Pall ring granular filler.During described extracting rectifying, liquid-gas ratio is 2: 1.During described extracting rectifying, the specific liquid rate of extractive distillation column is 30m
3/ (m
2.h), the spray temperature is 10 ℃.During described extracting rectifying, the pressure of extractive distillation column is 0.5Mpa.The tower top temperature of extractive distillation column is-5 ℃, and tower still temperature is 50 ℃.During described desorb rectifying, the pressure of Analytic Tower is 0.1Mpa, and the tower top temperature of Analytic Tower is 0 ℃, and tower still temperature is 60 ℃.