关键词: 膜清洗, 卷式纳滤膜, 气液两相流, 通量恢复率, 截留率, 气体流速, 气液比

Abstract:

A novel membrane cleaning apparatus was constructed and used to study the cleaning of 2540elements(2.5inch) spiral NF membrane with gasliquid twophase flow process.The twophase flow was formed by mixing the cleaning liquid with compressed air.The effects of cleaning liquid flow rate, air velocity, ratio of gas to liquid, and cleaning time on the rejection rate and flux recovery ratio(FRR)of NF membrane were investigated systematically.The results showed that high FRR of NF membrane was achieved by relatively low cleaning liquid flow rate about 0.1 L·min-1.NF membranes with different active areas had different critical cleaning flow rates.Above the critical flow rate, FRR of NF membrane increased slowly.FRR of NF membrane increased with air velocity.For polyamide composite NF membrane, the upper limit was 14 m·s-1 and higher air velocity would decrease the rejection rate of membrane.FRR of NF membrane was effectively improved when the gas to liquid ratio was from 1000∶1 to 3000∶1.The ratios lower than 1000∶1 or higher than 4000∶1 would decrease FRR.FRR was higher than 95% for cleaning NF membranes in a short 15 min cycle of the twophase flow process.

Key words: 膜清洗, 卷式纳滤膜, 气液两相流, 通量恢复率, 截留率, 气体流速, 气液比