Multi-stage seawater desalination apparatus and operation control method of multi-stage seawater desalination apparatus

Abstract

A high-pressure pump P 1 that increases the pressure of raw water, a high-pressure reverse osmosis device including a high-pressure reverse osmosis membrane for concentrating a salt content in high-pressure feed water, a first drain valve mounted on a permeated water line for supplying the permeated water downstream and temporarily draining permeated water of an initial start-up from a discharge line, a low-pressure pump that is mounted on a permeated water line provided downstream of the first drain valve and reduces the pressure of the permeated water, a low-pressure reverse osmosis device including a low-pressure reverse osmosis membrane for concentrating a salt content in low-pressure feed water, and a second drain valve mounted on a discharge line at the concentrated water side of the low-pressure reverse osmosis device that temporarily discharges the low-pressure feed water of the initial start-up supplied to the low-pressure reverse osmosis device.

1 . A multi-stage seawater desalination apparatus comprising:
 a high-pressure pump that is mounted on a raw water line through which raw water is supplied, and increases pressure of the raw water to a predetermined high pressure;   a high-pressure reverse osmosis device that includes a high-pressure reverse osmosis membrane for concentrating a salt content in high-pressure feed water whose pressure is increased by the high-pressure pump;   a first drain valve that is mounted on a permeated water line through which permeated water that has passed through the high-pressure reverse osmosis device is supplied downstream, and temporarily drains the permeated water of an initial start-up;   a low-pressure pump that is mounted on the permeated water line provided downstream of the first drain valve, and reduces pressure of the permeated water to a predetermined low pressure;   a low-pressure reverse osmosis device that includes a low-pressure reverse osmosis membrane for concentrating a salt content in low-pressure feed water whose pressure is reduced by the low-pressure pump; and   a second drain valve that is mounted on a discharge line on a concentrated water side of the low-pressure reverse osmosis device, and temporarily discharges the low-pressure feed water of the initial start-up supplied to the low-pressure reverse osmosis device.   
     
     
         2 . The multi-stage seawater desalination apparatus according to  claim 1 , further comprising
 a plurality of the low-pressure reverse osmosis devices, wherein   the second drain valve is mounted on the discharge line at the concentrated water side of each of the low-pressure reverse osmosis devices, and temporarily discharges the low-pressure feed water of the initial start-up supplied to the low-pressure reverse osmosis devices.   
     
     
         3 . The multi-stage seawater desalination apparatus according to  claim 1 , further comprising a returned concentrated water line that returns the concentrated water from the low-pressure reverse osmosis device upstream. 
     
     
         4 . The multi-stage seawater desalination apparatus according to  claim 1 , wherein the high-pressure reverse osmosis device is a membrane with chlorine-resistance.