JPS60804A - Ultrafiltration apparatus - Google Patents

Abstract

PURPOSE:To remove simply the clogging of the membrane arising in the process of filtration by exerting the pressure to the filtrate side, and changing over alternately the flow of the original liquid to the opposite direction in an ultrafiltration apparatus. CONSTITUTION:An original liquid 11 stored in an original liquid tank 10 is circulated and supplied into an ultrafiltration apparatus 13 at specified pressure by the action of a pump 12 through flow rate control valves 16 and 17 and a direction changeover valve 30. The valve 30, consisting of a four-way valve, has the function to allow the original liquid 11, which is sent from the pump 12 through the flow rate control valve 16, to pass through the ultrafiltration apparatus 13 from the left to the right or conversely from the right to the left, and can be changed over alternately at intervals of a specified time to the opposite direction by the control of a control circuit provided outside or manually. In this way, the clogging while filtering can be prevented only by changing over the flowing direction of the original liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrafilter device, and more particularly to an ultrafilter device that can extremely easily remove clogging of the membrane that occurs during the progress of filtration work.

Ultrafilter is a type of semi-permeable membrane (hereinafter referred to as "membrane") with a pore size of approximately 1μ to 0.001μ, which allows water, ions, and soluble low molecules to pass through, but does not allow high molecular substances or colloidal substances to pass through. has the property of cutting. As shown in FIG. 1, this ultrafilter device pours a stock solution 2 under pressure on one side of the membrane 10 and filters out components that can pass through the pore size on the other side of the membrane 1. In recent years, it has been used in many fields, including as a system for recovering paint taken out in electrodeposition coating lines, as a device for separating and concentrating and recovering components with molecular weights as low as 74%.

The type of ultrafilter device is as shown in Fig. 2, in which a cylindrical membrane IA is equipped in a double-tube structure in a cylindrical container 4, and the stock solution 2 is poured through both ends of one Menzblef, and the membrane is placed on the side of the container 4. A tubular type in which the P liquid 5 is discharged from the part 75, or a follow fiber type in which the membrane is made into a thin tube, or a plurality of membranes IB having a bag structure in the container 6 as shown in FIG. There are various types of pipes, such as the radial type, which are arranged in a spiral shape in the radial direction around the P liquid pipe 8 in which the through hole 7 is bored.

FIG. 4 is a system diagram showing a paint concentration system using the ultrafilter device described above. In the figure, reference numeral 10 is a stock solution tank in which stock solution 11 containing paint is stored. The stock solution 11 in the stock solution tank 10 is circulated and supplied at a predetermined pressure to an ultra filter device 13 by the action of a pump 12, and this ultra filter device 13 filters water and concentrates the paint. Ru. The ultrafilter device 13 is, for example, a tubular type, and has a configuration similar to that shown in FIG. 2. The stock solution 11 passes through the valve 16 and enters the membrane IA through the opening 14 provided at the left end of the container 4.
After the p-liquid 5 is filtered through the membrane lAi, it exits from the opening 15 at the right end (see solid line arrows A-D).

After concentration, the stock solution 11 passes through a valve 17 and is transferred to the stock solution tank 10.
Return to

On the other hand, the lachrymal fluid 5 is discharged from the discharge part 18 provided on the side wall of the container 4.
The filtrate is sent to a filtrate storage tank 20 via a valve 19. This tear reservoir 2
0 is equipped with a liquid level gauge 21, and when the liquid level 91 reaches a predetermined height, a pump 22 is activated to drain the lachrymal fluid 5 to the outside. 23 to 25 are pressure gauges, respectively.

By the way, when the ultrafilter device 13 is used for a long time in the concentration system described above, the polymeric components and colloidal components in the stock solution 11 adhere to the wall of the membrane IA, forming a gel layer 25. This gel layer 25 has the effect of causing the membrane IA to become wrinkled, reducing the filtration rate, deteriorating the concentration efficiency, and shortening the life span of the membrane IA. Therefore, conventionally, for example, in the case of FIG.
In order to remove the looseness, the valve 16.17 was closed, the valve 26.27 was opened, and a chemical solution for dissolving the gel layer 25 was circulated and supplied to the ultra filter device 13 for cleaning. ), the valve 19 was closed, the valve 28 was opened, and the filtrate 5'fr in the filtrate storage tank 20 was made to flow back to the ultrafilter device 13 side through the pump 29 to backwash the gel layer 25.

However, in the above conventional technology, the filtration operation has to be stopped for a long time every time the membrane is cleaned, which makes continuous operation impossible, lowers the operating rate, and complicates the system configuration. There is a drawback, and since there is a pressure difference between the inlet and outlet sides of the ultrafilter device, the gel layer is thicker on the inlet side, which is problematic.For this reason, when backwashing is performed, the cleaning effect on the outlet side is greater, but The cleaning effect on the artificial side is small, and furthermore, with the spiral type, the flow resistance increases toward the outside in the radial direction as shown in Figure 5, and r
The vicinity of the liquid pipe 8 can be backwashed, but the outside part can hardly be backwashed, which is a rare problem.

The present invention has been developed in view of the drawbacks of the prior art, and an object of the present invention is to provide an ultrafilter device that can easily remove clogging of the membrane while continuing filtration work. The present invention seeks to achieve this objective by alternately switching the flow direction of the stock solution to the ultrafilter device in opposite directions.

An embodiment of the present invention will be described below with reference to FIGS. 6 to 15. Here, the same components as in Figure WJ4 are given the same reference numerals.

FIG. 6 is a system diagram showing a paint concentration system according to the present invention. In the figure, 11 undiluted solutions stored in the undiluted solution tank 1o are circulated and supplied to the ultra filter device 13 at a predetermined pressure via the flow control valves 16, 17 and the directional control valve 30 by the action of the pump 12. ing. Said directional switching valve 3o
consists of a four-way valve, which connects the pump 12 via a flow control valve 16.
It has a function of switching the stock solution 11 sent from the ultra filter device 13 from left to right or from right to left, and is controlled by an external control circuit (not shown) or by manual operation for a predetermined period of time. It is designed so that it can be switched alternately in the opposite direction each time it elapses.

The stock solution 11 concentrated while passing through the ultrafilter device 13 is returned to the stock solution tank 10 again via the flow rate control valve 17. On the other hand, the lachrymal fluid 5 filtered by the ultrafilter device 13 is discharged into the filtrate storage tank 20 via a flow control valve 19 and a flow meter 31. 23 to 25 are pressure gauges, respectively.

Next, the overall operation of the above embodiment will be explained. still,
The raw liquid pressure in the ultra filter device 13 is expressed by V, and the liquid pressure by F is expressed by H.

In addition, the raw solution pressure on the inlet side P and outlet side Pz of the ultra filter device 13 during operation is expressed as gauge pressure Vu,
ML (where VH) Vi, , > O), and the flow control valve 19 is assumed to have orifice type characteristics for simplicity.

First, apply 1 part of the stock solution to membrane IA without clogging.
1 is flowing from the left to the right of the ultrafilter device 13 and the tear fluid pressure when the discharge part 18 is closed is Pc
= (VH+VL)/2, and as shown in FIG. 7, the pressure difference between the inside and outside of the membrane IA becomes symmetrical, with the neutral point PCf in the middle serving as the boundary, with filtration on the left and backwashing on the right. The filtration and backwashing effects in the membrane IA are proportional to the pressure difference between the inside and outside, and increase toward the ends of the ultrafilter device 13.

The filtration flow rate indicated by the area of the diagonal line ■ and the backwash flow rate indicated by the area of the diagonal line H are equal, the external flow rate Q of the filtrate 5 is O, and it moves between the container 4 and the membrane I from left to right. Separately, when the discharge part 18 is opened to atmospheric pressure and the fear is -0,
As shown in FIG. 8, the pressure differences inside and outside the membrane IA are all positive, resulting in a filtration state. At this time, the area of the diagonal line I becomes the external flow t Q = Qmax of the tear fluid 5. When the liquid pressure changes between 0 and 'vC, the external flow rate Q changes from 0 to
It changes linearly between Qnax. This state is shown as α0 in FIG. 14 as a static characteristic of the ultra filter device 13.

Now, when the flow control valve 19 is opened to the opening degree with the membrane IA in a good condition, the pressure on the inlet side of the flow control valve 19, that is, p
The fluid pressure υ and the flow rate from the valve.

That is, it is proportional to the external flow rate Q of the P liquid. This situation can be seen in the 14th
When added to the diagram, the intersection of the β reference number with α0 becomes the yarn operating point 'I's (9s + Qs), and the pressure distribution and flow distribution of the ultrafilter device 13 are
It will look like the figure. The neutral point 13s is located slightly to the right of Pc, and the filtrate 5 flows out to the outside by the area of the white square.

If the operation is continued for a period of time in the state shown in FIG. 9, a gel layer 40 will be formed on the membrane IA near the left opening 14 of the ultrafilter device 13, causing clogging (see FIG. 10). The gel layer 40 is thickest at the left end where the pressure difference between the inside and outside of the membrane IA is large. Due to clogging, the ultra fill device 13 has a distance of 1 ['ff, but the inlet side is not short, as shown in Fig. 10, the intermediate point Pc41, (VH+VL)/2
．． 1) Since the flow rate at o=0 becomes Qmax, the static characteristics of the ultrafilter device 13 change to α1 in FIG. 14, and therefore the operating point of the system moves to TS. That is, both the external flow rate and the F liquid pressure decrease. The pressure distribution and flow distribution of the ultrafilter device 13 are as shown in FIG. The neutral point P's moves to the right from P8, and the flow rate at the clogged area becomes smaller than the pressure difference because the resistance increases (see FIG. 10). As the clogging of the membrane IA progresses, the ultrafilter device 1 shown in FIG.
The static characteristic of 3 gradually approaches the origin from αO.

Next, when the state shown in FIG. 10 is reached, the directional control valve 30 is switched to allow the stock solution 11 to pass through the ultrafilter device 13 from right to left.

At this time, the right end of the device is the highest pressure vH1, the left end is the lowest pressure VL
becomes. However, since the membrane IA on the left end is already clogged, the ultra filter unit N1
3 is equivalent to shortening the exit side by the distance l in Fig. 11, and the virtual exit Pz (7) Pressure 'VL II
For C, midpoint Pcti (VH+VL)/2.0o
Since the flow rate at is Qrnax, the static characteristic of the ultrafilter device 13 changes to α2 in FIG. 14, and the operating point of the system becomes T'S. That is, both the external flow rate and the P liquid pressure increase. The pressure distribution and flow distribution are as shown in FIG.

Since the flow direction of the stock solution 11 has changed, the left side of the neutral point PS is backwashed, and the right side is in an offshore state, and a large differential pressure is applied at the left end where the degree of clogging is particularly severe, so the backwashing effect is extremely large. becomes. In the clogged area, the backwash flow rate becomes smaller than the pressure difference because the gel layer 40 provides resistance (11th
(See M in the figure). As the operation continues, the gel layer 40 that has undergone backwashing gradually separates from the membrane IA and becomes smaller. Correspondingly, the equivalent distance l' becomes smaller and the static characteristic of the ultrafilter device 13 approaches α2 from α0. When the gel layer 4o is completely removed, the operating point of the system returns to the aforementioned Ts. The pressure distribution and flow distribution at this time are shown in FIG.

As the operation continued for a while, the membrane I at the right end of the device, which was in a filtration state symmetrically to the case in Figure 10, was removed.
A gel layer 4o is formed at A.

Therefore, the operating point of the system is 6 as mentioned above. The pressure distribution and flow distribution at this time are shown in FIG. When the state shown in FIG. 13 is reached, by switching the directional control valve 30 again and passing the undiluted solution 11 from the left to the right of the ultra filter device 13, backwashing of the clog can be performed in the same manner as described above. .

Therefore, for example, within the range where the operating point is T's -'rs -T, membrane clogging can always occur without interrupting the filtration operation by simply switching the directional control valve 30 in the opposite direction at predetermined intervals. This makes it possible to prevent

Note that by changing the opening degree of the flow rate control valve 19, the valve pressure and
The flow rate characteristics become as indicated by the dotted line in FIG. 14, and the tear flow rate changes to be determined by the intersection with α.

Figure 15 shows the results of a concentration experiment using a spiral type ultra filter device V (membrane surface 1.8 m) to concentrate a stock solution consisting of a water-based paint with a solid content of 15 cm and 5 to 20 micron powder resin dispersed therein. show. In the figure, X indicates the lachrymal fluid flow rate (30Q cc/min), which is approximately 1/2 of the initial open value, and several F flow control valves are closed so that the flow direction of the stock solution is reversed once every hour. The passage of time and the change in the flow rate of tear fluid are shown when the cap is stirred, and Y indicates a comparative example in which the stock solution continues to flow in one direction in an open state.

In the above embodiment ((), the case where the opening degree of several flow control valves is set to 1 even when switching the direction of the undiluted solution was explained, For a short period of time, close the P several flow control valves using timer control, etc., and set T (P=Ga IQ=O) in the M3 diagram as the operating point to apply a large backwash differential pressure to the gel layer. The valve may be opened to a predetermined opening degree after a predetermined period of time so that clogs can be removed quickly.Experiments have shown that the valve can be closed for a few minutes, which has little effect on filtration work. It was found that the confusion was almost eliminated.Also,
Although the above embodiment has been described with reference to the case where it is applied to a paint concentration system, the present invention is not limited to this in any way, and can also be applied to a system for recovering paint taken out from an electro-dip coating line. Needless to say.

As explained above, according to the present invention, the membrane can be prevented from clogging while the filtration work continues by simply changing the flow direction of the stock solution, so the filtration work can be stabilized for a long period of time without putting a burden on the system configuration. It is possible to obtain an ultra-filter device that has a high operating rate and is excellent in economic efficiency.

[Brief explanation of the drawing]

Figure 1 is the principle diagram of the ultra filter, Figures 2 to 3
The figures are schematic diagrams showing examples of how the Ultra Filter device is used, Figure 4 is a system diagram showing a system for recovering paint taken out in an electrodeposition coating line using a conventional Ultra Filter device, and Figure 5 is a system diagram showing how the paint is recovered during backwashing. 3 is an explanatory diagram showing the action of FIG. 6, and FIG. 6 is a system diagram that does not show a system for recovering paint taken out according to an embodiment of the present invention, and FIGS.
FIG. 14 is a diagram showing the operation of FIG. 6, and FIG. 15 is a diagram showing the experimental results together with a comparative example. 1, IA, 113... membrane, 2.11.
...Natural solution, 5...P liquid, 13...Ultra filter device, 30...Directional switching valve. Special Wf Applicant Co., Ltd. Polytex Figure 74 Figure 15

Claims (1)

[Claims] (1) In an ultrafilter device that flows a stock solution under pressure on one side of the membrane and filters low-molecular components in the stock solution on the other side of the membrane, pressure is applied to several F and the flow direction of the stock solution is An ultra filter device characterized in that the filters are alternately switched in opposite directions.