WO2015002015A1

WO2015002015A1 - Operating method for membrane separation device, and membrane separation system

Info

Publication number: WO2015002015A1
Application number: PCT/JP2014/066630
Authority: WO
Inventors: 育野　望
Original assignee: 栗田工業株式会社
Priority date: 2013-07-03
Filing date: 2014-06-24
Publication date: 2015-01-08
Also published as: JP2015013233A; TW201524587A

Abstract

Provided are an operating method and operating system for a membrane separation device which make it possible to obtain permeated water having favorable water quality from a large-scale membrane separation device having a large-diameter membrane element with a diameter of 20cm or larger. A method for operating a membrane separation device in which a membrane element (2) having a diameter of 20cm or larger is positioned inside a cylindrical vessel (1), the method and system for operating the membrane separation device being characterized in that (a/n)/b equals 0.1-0.2, given that a (m³/h) is the amount of permeated water from the membrane separation device, b (m³/h) is the minimum brine solution amount from the membrane element (2), and n (n is 1 or higher) is the number of membrane elements.

Description

Method of operating membrane separation apparatus and membrane separation system

The present invention relates to an operation method and a membrane separation system of a membrane separation device such as a reverse osmosis membrane separation device and a microfiltration device, and more particularly to an operation method and a membrane separation system of a spiral membrane separation device.

As a method for obtaining seawater desalination, ultrapure water, and water for various production processes, for example, a reverse osmosis membrane (hereinafter sometimes abbreviated as RO membrane) or a nanofiltration membrane (hereinafter abbreviated as NF membrane). There are known methods for separating ionic and low molecular components from raw water using a spiral membrane element having a separation membrane. Spiral membrane elements, for example, form a bag-like membrane by overlaying reverse osmosis membranes on both sides of the permeate spacer and bonding three sides, and attach the opening side of the bag-like membrane to the permeate water collecting pipe Along with the net-like raw water spacer, the outer periphery of the permeate water collecting pipe is wound around in a spiral shape. The raw water is supplied from one end face side of the spiral membrane element, flows along the raw water spacer, and is discharged as concentrated water from the other end face side of the spiral membrane element. In the process of flowing along the raw water spacer, the raw water permeates through the reverse osmosis membrane to become permeated water. This permeated water flows along the permeated water spacer into the permeated water collecting pipe located in the center, It is discharged from the end of the water pipe. A raw water path is formed by raw water spacers arranged between the wound bag-like membranes (Patent Documents 1 to 3).

In reverse osmosis membrane separation, it is recommended to operate so that the flow rate of the concentrated liquid (brine) becomes a predetermined value or more in order to suppress the generation of scale due to concentration polarization on the membrane surface and the decrease in the desalination rate. (Paragraph 0033 of Patent Document 4, paragraph 0011 of Patent Document 5, and paragraphs 0003 to 0004 of Patent Document 6). This predetermined value is referred to as a minimum brine water amount (minimum concentrated water amount). The amount of minimum brine water is indicated according to the model number by the manufacturer of the membrane separator.

Conventionally, the diameter (outer diameter) of the membrane element of the spiral membrane separator has been mainly 8 inches (about 20.32 cm), but in recent years, a large size of 16 inches (about 40.64 cm) has been used. (Paragraph 0007, paragraph 0007). The amount of minimum brine in a reverse osmosis membrane separation device (hereinafter, also referred to as an 8-inch RO device) having a spiral membrane element having an outer diameter of 8 inches is generally 3.6 m ³ / h. A reverse osmosis membrane separation device (hereinafter, sometimes referred to as a 16-inch RO device) having a spiral membrane element having an outer diameter of 16 inches has a membrane area four times that of an 8-inch RO device. 14.4 m ³ / h.

JP2011-167667A JP 2009-220104 A JP 2006-218341 A JP2007-31445A JP-A-8-108048 JP2011-136283A

When the minimum brine water volume was operated at 14.4 m ³ / h in the 16-inch RO device, the desalination rate might be lower than that in the 8-inch RO device under the same membrane type and the same operating conditions. This is because the element diameter of the 16-inch RO device is about twice as large as that of the 8-inch RO device. Therefore, when operating with the minimum brine water amount 4 times the minimum brine water amount of the 8-inch RO device, This is considered to be because the flow velocity distribution becomes large, and a region with a small flow velocity is partially generated, concentration polarization occurs in this region, and the desalination rate decreases.

An object of the present invention is to provide an operation method and an operation system of a membrane separation device capable of obtaining permeated water having a good water quality from a large membrane separation device having a large-diameter membrane element having a diameter of 20 cm or more. .

The present invention relates to a method for operating a membrane separation apparatus in which n (n is 1 or more) membrane elements having a diameter of 20 cm or more are installed in a cylindrical vessel. In the present invention, when the permeated water amount of the membrane separation device is a (m ³ / h) and the minimum brine water amount of the membrane element is b (m ³ / h), (a / n) / b is 0.1 to Water is passed through the membrane separation device so as to be 0.2.

The membrane separation system of the present invention comprises a membrane separation device in which n membrane elements (n is 1 or more) are installed in a cylindrical vessel, a flow rate adjusting means for raw water supplied to the membrane separation device, and the membrane The flow rate adjusting means for the brine flowing out from the separator, the flow rate detecting means for the permeated water taken out from the membrane separator, and the amount of permeated water detected by the flow rate detecting means a (m ³ / h), the minimum of the membrane element When the amount of brine water is b (m ³ / h), the raw water flow rate adjusting means and the control means for controlling the brine flow rate adjusting means so that (a / n) / b is 0.1 to 0.2 Have.

In the present invention, the membrane element preferably has a diameter of 20 to 50.8 cm.

The membrane element is preferably a reverse osmosis membrane element.

The membrane element is a spiral type membrane element having a water collecting pipe in the axial center, a plurality of membrane elements are coaxially arranged in the vessel, and the water collecting pipes of adjacent membrane elements are connected by a joint. Is preferred.

In the present invention, water is passed through the membrane separation apparatus so that the ratio (a / n) / b of the permeated water amount (a / n) per membrane element to the minimum brine water amount b is 0.1 to 0.2. By doing so, the removal rate of a membrane element becomes high. In general, when the water to be treated flows along the membrane of the membrane element, if the flow velocity along the membrane surface decreases, concentration polarization occurs and the quality of the permeated water deteriorates. When the flow velocity along the membrane surface is increased, concentration polarization is eliminated, but the water sampling rate (permeated water amount / raw water amount) is lowered. Therefore, if the membrane surface flow velocity is reduced within a range where concentration polarization does not occur, a large amount of permeated water having good water quality can be collected.

In the case of an 8-inch RO device, by passing water so that the amount of brine water is equal to or greater than the minimum brine water amount (usually about 3.6 m ³ / h), the permeated water with good water quality can be obtained. It can be obtained at a high recovery rate (water sampling rate).

In the case of a 16-inch RO device, the concentration of the brine water is about 4 times the minimum brine water amount of the 8-inch RO device 3.6 × 4 = 14.4 m ³ / h or slightly higher than that. Polarization occurs and the permeated water quality is likely to deteriorate. This is because the distribution of the flow velocity along the membrane surface occurs because the diameter of the membrane element increases. In addition, concentration polarization on the membrane surface is affected not only by the flow velocity along the membrane surface but also by the membrane permeation flux. Therefore, if operation is performed based only on the amount of minimum brine water, concentration polarization occurs and the quality of the permeate water deteriorates. There is also a fear.

In the present invention, the permeated water having a good water quality can be collected at a high recovery rate by passing water in consideration of both the permeated water amount and the minimum brine water amount.

It is a perspective view of a membrane separator. FIG. 2 is a perspective view of a part of FIG. 1. It is a flowchart of the membrane separation system which concerns on embodiment. It is a flowchart of the membrane separation system in an Example.

Hereinafter, embodiments will be described with reference to FIGS.

As shown in FIG. 1, a plurality of (three in this embodiment) membrane elements 2 are coaxially installed in a cylindrical vessel 1. The membrane element 2 is a spiral membrane element having a water collecting pipe 3 made of a perforated pipe at the axial center, and a bag-like separation membrane wound around the outer circumference of the water collecting pipe 3 via a raw water flow path spacer. In this embodiment, the outer diameter of each membrane element 2 is 20 cm or more, preferably 20 to 50.8 cm. The axial length of the membrane winding part of each membrane element 2 is preferably 15 to 50 times the outer diameter. The membrane of the membrane element 2 may be either a reverse osmosis membrane or a microfiltration membrane, but a reverse osmosis membrane is preferred.

The water collecting pipes 3 of the adjacent membrane elements 2 are connected by a joint 4. The number n of membrane elements is preferably 3 to 6, particularly about 4 to 6.

As shown in FIG. 3, raw water is introduced from the pipe 8 to one end side of the vessel 1 through the pump 5 and the flow rate control valve 6 and flows along the membrane surface of each membrane element 2. In the middle of this, water permeates the membrane, flows into the water collecting pipe 3, and is taken out as permeated water through a pipe 10 having a flow meter 9. The concentrated water (brine) that has not passed through the membrane flows out through the pipe 11 connected to the other end of the vessel 1. The pipe 11 is provided with a flow meter 12 and a flow control valve 13.

In this embodiment, as shown in FIG. 2, a guide 15 is extended along the inner peripheral surface on the one end side of the vessel 1, and the raw water flowing in from the pipe 8 is circumferentially introduced into the vessel 1 by the guide 15. It is comprised so that it may flow in while circulating around. This is because the raw water is uniformly supplied to the upstream end face of the membrane element 2.

The detection signals of the

flow meters

9 and 12 are input to the controller 17, and the control signal from the controller 17 is given to the pump 5 and the flow

rate adjusting valves

6 and 13.

The controller 17 sets the permeated water amount detected by the flow meter 9 to a (m ³ / h), the minimum brine water amount of the membrane element to b (m ³ / h), and the number of membrane elements 2 to n (n is 1 or more). ), The flow

rate regulating valves

6 and 13 are controlled so that (a / n) / b is 0.1 to 0.2. In order to operate so that (a / n) / b is less than 0.1, it is necessary to increase the number of films, which is not practical. When (a / n) / b exceeds 0.2, the water quality such as the electric conductivity of the permeated water deteriorates, which is not preferable.

Three reverse osmosis membrane elements 2 (n = 3) having an outer diameter of 16 inches (about 40.64 cm) and a membrane winding portion having an axial length of 100 cm are installed in the vessel 1, and the reverse osmosis shown in FIG. A membrane separator was constructed. Water was passed through the reverse osmosis membrane separation apparatus using a raw water tank 20 as shown in FIG. In the flow of FIG. 4, industrial filtered membrane water is introduced into the raw water tank 20 as raw water, and the raw water in the raw water tank 20 is reverse osmosis through the pump 5, the flow control valve 6 and the pipe 8 as in FIG. 3. Supply to membrane separator. A part of the brine flowing out from the pipe 11 is returned to the raw water tank 20 through the pipe 22 and the flow rate control valve 23. The remaining portion of the brine that has flowed out of the pipe 11 is taken out of the system through the pipe 21 and the flow rate control valve 13. Automatic control by the controller 17 was not performed, and the opening degree control of the flow control valve 13 was performed manually. Other configurations in FIG. 4 are the same as those in FIG. 3, and the same reference numerals denote the same parts.

Industrial reverse water membrane filtered water is supplied from the raw water tank 20 to the reverse osmosis membrane separation device at 12.25 m ³ / h, and the opening of the flow rate control valve 13 is adjusted so that the brine flow rate becomes each value shown in Table 1. Adjusted. As described above, automatic control by the controller 17 was not performed, and the opening degree control of the flow rate control valve 13 was manually performed.

Table 1 shows the quality of the permeated water and the water recovery rate.

As shown in Table 1, No. was passed through so that (a / n) / b was 0.1 to 0.2. 4 to No. In the case of 7, the quality of the permeated water is good.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2013-139846 filed on July 3, 2013, which is incorporated by reference in its entirety.

Claims

A method of operating a membrane separation apparatus in which n (n is 1 or more) membrane elements having a diameter of 20 cm or more are installed in a cylindrical vessel,
When the permeated water amount of the membrane separation device is a (m 3 / h) and the minimum brine water amount of the membrane element is b (m 3 / h), (a / n) / b is 0.1 to 0.2. A method for operating a membrane separation device, characterized in that the water is passed as described above.
The method for operating a membrane separation device according to claim 1, wherein the membrane element has a diameter of 20 to 50.8 cm.
The method of operating a membrane separation device according to claim 1, wherein the membrane element is a reverse osmosis membrane element.
The membrane element according to any one of claims 1 to 3, wherein the membrane element is a spiral membrane element having a water collecting pipe at an axial center portion, and a plurality of membrane elements are coaxially arranged in the vessel. A method for operating a membrane separation device, wherein the water collecting pipes of the elements are connected by a joint.
A membrane separator in which n membrane elements (n is 1 or more) are installed in a cylindrical vessel;
A flow rate adjusting means for raw water supplied to the membrane separator;
A flow rate adjusting means for brine flowing out of the membrane separator;
A flow rate detecting means for permeated water taken out from the membrane separator;
When the permeated water amount detected by the flow rate detection means is a (m 3 / h) and the minimum brine water amount of the membrane element is b (m 3 / h), (a / n) / b is 0.1-0. A membrane separation system comprising control means for controlling the raw water flow rate adjusting means and the brine flow rate adjusting means so as to be 2.
6. The membrane separation system according to claim 5, wherein the membrane element has a diameter of 20 to 50.8 cm.
6. The membrane separation system according to claim 5, wherein the membrane element is a reverse osmosis membrane element.
8. The membrane element according to claim 5, wherein the membrane element is a spiral membrane element having a water collecting pipe at an axial center, and a plurality of membrane elements are coaxially arranged in the vessel. A membrane separation system, wherein the water collecting pipes of the elements are connected by a joint.