| 摘要 |
PROBLEM TO BE SOLVED: To provide a system that can purify NMP while suppressing the deterioration during pervaporation separation (PV).SOLUTION: Ion exchange means 16 removes the impurities contained in NMP aqueous solution. Regarding the NMP aqueous solution whose impurities are removed by the ion exchange means 16, pervaporation separation means 18 selectively separates moisture via a separation membrane, to yield dewatered NMP. Meanwhile, the conductivity of the impurity free NMP aqueous solution supplied to the pervaporation means 18 is measured by conductivity measurement means 34a, 34b. |
