JP-7855196-B2 - Method and apparatus for film treatment of liquid to be treated

JP7855196B2JP 7855196 B2JP7855196 B2JP 7855196B2JP-7855196-B2

Inventors

早水基頼

Assignees

株式会社ササクラ

Dates

Publication Date: 20260508
Application Date: 20220531

Claims (6)

A first NF membrane treatment step involves passing the liquid to be treated through a first NF membrane to generate a first NF membrane permeate that has permeated through the first NF membrane, A dilution step is performed by bringing the first NF film concentrate, which has been concentrated in the first NF film processing step without permeating the first NF film, into contact with a diluent via a semipermeable membrane, thereby diluting the first NF film concentrate. The process includes a second NF membrane treatment step, in which the first NF membrane concentrate diluted in the dilution step is passed through a second NF membrane to generate a second NF membrane permeate that has permeated through the second NF membrane , The system further comprises an RO membrane processing step of passing the first NF membrane permeate and the second NF membrane permeate through an RO membrane to generate an RO membrane permeate that has permeated through the RO membrane, The aforementioned dilution step is a membrane treatment method for a liquid to be treated, in which a portion of the generated RO membrane permeate is used as the diluent .
The membrane treatment method for a liquid to be treated according to claim 1 , further comprising the RO membrane treatment step of concentrating the first NF membrane permeate and the second NF membrane permeate in multiple stages using a plurality of RO membrane units equipped with the RO membrane.
The method for membrane treatment of a liquid to be treated according to claim 2 , wherein the dilution step uses the RO membrane permeate of at least the foremost RO membrane unit as the dilution solution.
The RO membrane processing step includes a step of increasing the pressure of the RO membrane concentrate concentrated in the preceding RO membrane unit by recovering energy from the RO membrane concentrate concentrated in the subsequent RO membrane unit. The method for membrane treatment of a liquid to be treated according to claim 2 or 3 , wherein the dilution step uses the RO membrane permeate generated by the RO membrane unit in the subsequent stage as the dilution solution.
The method for treating a liquid with a membrane, according to claim 1, wherein the liquid to be treated is seawater.
A first NF membrane processing apparatus that passes a liquid to be processed through a first NF membrane to generate a first NF membrane permeate that has permeated through the first NF membrane, A dilution device for diluting the first NF membrane concentrate, which has been concentrated in the first NF membrane processing apparatus without permeating the first NF membrane, by bringing it into contact with a dilution solution via a semipermeable membrane, The apparatus comprises a second NF membrane apparatus which passes the first NF membrane concentrate, diluted in the dilution apparatus, through a second NF membrane to generate a second NF membrane permeate that has permeated through the second NF membrane , The RO membrane processing apparatus further comprises passing the first NF membrane permeate and the second NF membrane permeate through an RO membrane to generate an RO membrane permeate that has permeated through the RO membrane, The dilution apparatus is a membrane treatment apparatus for a liquid to be treated, which uses a portion of the generated RO membrane permeate as the dilution solution .

Description

This invention relates to a method and apparatus for membrane treatment of a liquid to be treated, and more specifically, to a method and apparatus for membrane treatment of a liquid to be treated using an NF membrane. The membrane treatment of liquids to be treated using NF membranes (nanofiltration membranes) has been conventionally used as a pretreatment for processes such as seawater desalination, salt production, and concentration using RO membranes (reverse osmosis membranes). Specifically, when seawater is supplied directly to an RO membrane, there is a risk of scale deposition and accumulation on the RO membrane due to scale-forming ions such as calcium carbonate and calcium sulfate present in the seawater. Therefore, by reducing the scale-forming ions through NF membrane treatment before RO membrane treatment, the risk of scaling is suppressed. However, conventional membrane treatment methods using NF membranes are problematic because, as the treated liquid becomes more concentrated, scale tends to precipitate on the concentrated side of the NF membrane. Furthermore, the need for high-pressure membrane treatment increases energy costs, making it difficult to increase the water flow rate through the NF membrane and thus improve salt recovery rates. Therefore, Patent Document 1 discloses a method in which water to be treated with the same osmotic pressure is supplied to both sides of a semipermeable membrane, and pressure is applied to one side of the semipermeable membrane to enrich the water supplied to the other side of the semipermeable membrane with monovalent ions. This treated water is then filtered through an NF membrane and used as treated water in salt production and desalination processes. Japanese Patent Publication No. 2020-89867 This is a schematic diagram of a membrane treatment device for a liquid to be treated according to one embodiment of the present invention.This is a schematic diagram of a membrane treatment apparatus for a liquid to be treated according to another embodiment of the present invention.This is a schematic diagram of a membrane treatment apparatus for a liquid to be treated according to yet another embodiment of the present invention.This is a schematic diagram of a membrane treatment apparatus for a liquid to be treated according to yet another embodiment of the present invention.This is a schematic diagram of a membrane treatment apparatus for a liquid to be treated according to yet another embodiment of the present invention.This is a schematic diagram of a membrane treatment apparatus for a liquid to be treated according to yet another embodiment of the present invention.This is a schematic diagram of a membrane treatment apparatus for a liquid to be treated according to yet another embodiment of the present invention.This figure shows a modified example of the main part of Figure 1.This figure shows another modified example of the main part of Figure 1.This figure shows yet another modified example of the main part of Figure 1.This figure shows yet another modified example of the main part of Figure 1. The embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a basic configuration diagram of a membrane processing apparatus for a liquid to be processed (hereinafter simply referred to as "membrane processing apparatus") according to one embodiment of the present invention. As shown in Figure 1, the membrane processing apparatus 1-1 comprises a first NF membrane processing apparatus 10, a dilution apparatus 20, and a second NF membrane processing apparatus 30. The first NF membrane processing apparatus 10 consists of an NF membrane module equipped with a first NF membrane (nanofiltration membrane) 12 within a casing. By passing the liquid to be processed through the first NF membrane 12, a first NF membrane permeate (the liquid that has permeated through the first NF membrane 12) and a first NF membrane concentrate (the liquid that has been concentrated without permeating through the first NF membrane 12) are produced. Examples of the shape of the first NF membrane 12 include flat membranes and hollow fiber membranes. The dilution device 20 has a casing partitioned by a semipermeable membrane 22, forming a first chamber 24 and a second chamber 26. A diluent is introduced into the first chamber 24, while the first NF membrane concentrate produced by the first NF membrane processing device 10 is introduced into the second chamber 26. The diluent and the first NF membrane concentrate introduced into the first chamber 24 and the second chamber 26, respectively, come into contact via the semipermeable membrane 22 and are then discharged to the outside. During this process, water moves from the first chamber 24 to the second chamber 26 via the semipermeable membrane 22, thereby diluting the first NF membrane concentrate with the diluent. The semipermeable membrane 22 can be appropriately selected consideri