Method and device for recovering perfluoro caprylic acid from tail gas produced in fluoropolymer production

Abstract

Perfluoro caprylic acid is generally used in the production process of fluoropolymers produced through an emulsion polymerization method, the fluoropolymers are dried after a polymerization reaction is completed, and as the perfluoro caprylic acid is absorbed by the fluoropolymers, a large number of tail gas containing perfluoro caprylic acid steam is produced in the drying process. The tail gas containing the perfluoro caprylic acid steam is absorbed with absorption liquid in an absorption tower, perfluoro capylic acid salt in the absorption liquid after absorbing the perfluoro caprylic acid is concentrated through adopting a nanofilteration membrane or a reverse osmosis membrane, the absorption liquid penetrating through the membrane returns to the absorption process to be repeatedly used, perfluoro caprylic acid salt concentrated solution obtained through concentration by the membrane is subjected to subsequent acidizing and rectifying, the perfluoro caprylic acid is recovered, and the concentrated solution can be used in other processes directly. Through the process, the perfluoro caprylic acid in the tail gas in an oven can be completely absorbed, the tail gas meets the discharge standard, other wastewater and waste gas are not produced while the perfluoro caprylic acid in the tail gas is recovered, and the process is easily amplified, and suitable for industrial production.

Description

technical field [0001] The invention relates to a method for recovering perfluorooctanoic acid from tail gas produced from the production of fluorine-containing polymers, and belongs to the field of chemical waste gas treatment. Background technique [0002] Perfluorooctanoic acid is a fluorine-containing organic compound that does not occur naturally in nature and is a synthetic product. Its invention and use have a history of more than 60 years. Due to the stability of the carbon-fluorine bond, perfluorooctanoic acid is not easily degraded by nature and belongs to persistent organic pollutants. Due to the good water solubility of PFOA, the PFOA discharged into nature is very easy to migrate in water bodies, causing water pollution. PFOA emitted in the form of exhaust gas is also easily attached to dust particles in the air for migration, and finally transferred to water bodies with rainfall. Due to its good chemical stability and water solubility, PFOA is not degraded by...

AI Technical Summary

Problems solved by technology

This process uses an absorption tank to absorb PFOA in the mixed gas by bubbling, but when the concentration of PFOA in the absorption lye is high, the absorption efficiency will decrease, and a large number of bubbles will be generated when the tail gas is passed into the absorption tank, which will affect the absorption and post-treatment process

In the absorption process, the absorption liquid uses high-concentration lye, which consumes a lot of alkali, requires high anti-corrosion equipment, and has high industrialization costs.

Patent CN 102643189A uses a spray tower to absorb the tail gas after heat exchange and cooling. This process is likely to cause incomplete absorption due to the concentration of perfluorooctanoic acid in the final absorption liquid as high as 20-30%.

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