A high osmotic pressure online reverse cleaning method and device for nanofiltration and reverse osmosis membranes

Abstract

The invention discloses a high-osmotic-pressure on-line reverse cleaning method and a device of nanofiltration reverse osmosis membrane. According to the high-osmotic-pressure on-line reverse cleaning method, commonly used nanofiltration membrane and reverse osmosis membrane systems are taken as the basics, strong brine obtained in reverse osmosis production process or strong brine obtained via adding of electrolyte is taken as a raw water, and is injected into nanofiltration membrane or reverse osmosis membrane to generate high osmotic pressure; yield water is absorbed back into the membrane systems under the action of concentrated water osmotic pressure via controlling on strong brine osmotic pressure and membrane flux, and then is discharged out from the membrane systems, so that reverse cleaning is realized. The invention also discloses a reverse cleaning method. According to the reverse cleaning method, strong brine generated in reverse osmosis is used, drug-adding-free operation and drug-adding-free cleaning of nanofiltration and reverse osmosis membrane are realized, shutting of a high pressure pump is not needed in cleaning process, washing time is short, no artificial intervention is needed, the structure safety of nanofiltration membrane and reverse osmosis membrane is ensured, membrane operation cost is reduced, drug cost is avoided, and membrane service life is prolonged.

Description

technical field [0001] The invention belongs to the technical field of membranes, and in particular relates to a high osmotic pressure online reverse cleaning method and device for nanofiltration and reverse osmosis membranes. Background technique [0002] A membrane that is selective to the substance that passes through is called a semi-permeable membrane. When the same volume of dilute solution (such as fresh water) and concentrated solution (such as salt water) are placed on both sides of the semi-permeable membrane, the solvent in the dilute solution Spontaneous flow to the concentrated solution side through a semipermeable membrane is called osmosis. When the osmosis reaches equilibrium, the liquid level on the concentrated solution side will be higher than the liquid level of the dilute solution by a certain height, which forms a pressure difference, which is the osmotic pressure. The size of the osmotic pressure depends on the inherent properties of the solution, tha...

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Problems solved by technology

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the object of the present invention is to provide a high osmotic pressure online reverse cleaning method and device for nanofiltration and reverse osmosis membranes, aiming at serious membrane pollution and traditional chemical cleaning in the application of membrane separation technology There are problems such as secondary pollution and frequent cleaning. According to the principle of osmosis, when the membrane system is running, by changing the osmotic pressure of the raw water and the operating pressure of the membrane, the produced water (permeate) is reversed under the action of the osmotic pressure of the concentrated water. "Suck back" to the membrane system, and discharge the membrane system together with concentrated brine to realize reverse cleaning of the membrane

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