| 摘要 |
PROBLEM TO BE SOLVED: To provide a desalination method which is used for desalting salt water to produce freshwater and in which a nanofiltration membrane, a reverse osmosis membrane and a thermal distillation unit are used and salt water is desalted to produce freshwater at a high recovery rate and in excellent energy efficiency while restraining the precipitation of a scale component. SOLUTION: Salt water is filtered by the nanofiltration membrane to decrease the ion content containing the scale component. The obtained nanofiltrate is flow-divided into the upstream-side nanofiltrate having lower salt concentration and the downstream-side nanofiltrate having the salt concentration higher than that of the downstream-side nanofiltrate, which are then withdrawn. The withdrawn upstream-side nanofiltrate is introduced into a semipermeable membrane to obtain freshwater at a higher recovery rate and by a low energy consumption. The downstream-side nanofiltrate is introduced into the thermal distillation unit to obtain freshwater at a higher recovery rate. As a result, desalination can be performed at a high recovery rate and in excellent energy efficiency as the whole system. COPYRIGHT: (C)2008,JPO&INPIT
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