PROCESS FOR CONCENTRATING AND RECOVERING SURFACTANT AQUEOUS SOLUTION
A process for concentrating and recovering a surfactant aqueous solution, by evaporating and concentrating a surfactant aqueous solution containing a gasifiable surfactant and an aqueous solvent to increase the concentration of the surfactant, which comprises storing the surfactant aqueous solution in an evaporator 12 ; adjusting the temperature of the surfactant aqueous solution in the evaporator 12 to be lower than the boiling point of the aqueous solvent under the pressure in the evaporator 12 ; withdrawing a part of the surfactant aqueous solution from the evaporator 12 , superheating it by a superheater 14 under conditions that all the surfactant and the aqueous solvent are formed into an annular flow or an annular mist flow, and spraying it from a nozzle 32 having a shape such that the outlet side first narrows and then widens outward, into the evaporator 12 ; and evaporating and removing the aqueous solvent.
1 . A process for concentrating and recovering a surfactant aqueous solution, by evaporating and concentrating a surfactant aqueous solution containing a gasifiable surfactant and an aqueous solvent to increase the concentration of the surfactant, which comprises:
storing the surfactant aqueous solution in an evaporator;
adjusting the temperature of the surfactant aqueous solution in the evaporator to be lower than the boiling point of the aqueous solvent under the pressure in the evaporator;
withdrawing a part of the surfactant aqueous solution from the evaporator, superheating it under conditions that all the surfactant and the aqueous solvent are formed into an annular flow or an annular mist flow, once pressure-condensing the surfactant aqueous solution in a nozzle and spraying it into the evaporator by the nozzle having a shape such that the outlet side first narrows and then widens outward; and
evaporating and removing the aqueous solvent.
2 . The process for concentrating and recovering a surfactant aqueous solution according to claim 1 , wherein the surfactant is a C 4-10 fluorinated surfactant.
3 . The process for concentrating and recovering a surfactant aqueous solution according to claim 1 , wherein the content of the surfactant in the surfactant aqueous solution is from 1 to 30 mass %.
4 . The process for concentrating and recovering a surfactant aqueous solution according to claim 1 , wherein the pressure in the evaporator is at most 101 kPa.
5 . The process for concentrating and recovering a surfactant aqueous solution according to claim 1 , wherein the temperature of the surfactant aqueous solution in the evaporator is at most 99° C.
6 . The process for concentrating and recovering a surfactant aqueous solution according to claim 1 , wherein the nozzle has a pressurizing portion where the inner diameter of the flow path gradually decreases, an open portion where the inner diameter of the flow path gradually increases, and a connecting portion having a constant inner diameter of the flow path, connecting the pressurizing portion and the open portion.
7 . The process for concentrating and recovering a surfactant aqueous solution according to claim 6 , wherein the angle at which the inner wall opens at the open portion of the nozzle is from 90 to 150°.
8 . The process for concentrating and recovering a surfactant aqueous solution according to claim 2 , wherein the fluorinated surfactant is at least one fluorinated surfactant selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2):
R F1 O(CF 2 CF 2 O) a CF 2 COOX 1 (1)
CF 3 (CF 2 ) b COOX 2 (2)
wherein R F1 is a C 1-4 perfluoroalkyl group, X 1 is a hydrogen atom, an alkali metal or NH 4 , and a is an integer of from 1 to 3; and X 2 is a hydrogen atom, an alkali metal or NH 4 , and b is an integer of from 3 to 7.
9 . The process for concentrating and recovering a surfactant aqueous solution according to claim 8 , wherein the fluorinated surfactant represented by the formula (1) is ammonium salt of C 2 F 5 OCF 2 CF 2 OCF 2 COOH.
10 . The process for concentrating and recovering a surfactant aqueous solution according to claim 8 , wherein the fluorinated surfactant represented by the formula (2) is ammonium perfluorooctanoate or ammonium perfluorononanoate.
11 . The process for concentrating and recovering a surfactant aqueous solution according to claim 1 , wherein the surfactant aqueous solution is at least one aqueous solution selected from the group consisting of an aqueous solution obtained by separating, from an aqueous dispersion of a fluorinated polymer obtained by emulsion polymerization or suspension polymerization of at least one fluorinated monomer in the presence of the surfactant, the fluorinated polymer, an aqueous solution having exhaust gas discharged at the time of drying or heat treatment of the fluorinated polymer, absorbed, and an aqueous solution used for cleaning the fluorinated polymer.