JPS6329563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating a liquid using a hollow fiber membrane, and more particularly to a method for supplying a stock solution in internal pressure circulation treatment of a hollow fiber membrane.

The so-called internal pressure circulation treatment of hollow fiber membranes uses a module that bundles a large number of hollow fibers to circulate and over-process the stock solution to be treated inside the hollow fiber membrane.
It is widely used especially as a solution treatment in the industrial field. However, one of the problems in the internal pressure circulation treatment of the hollow fiber membrane is clogging of the hollow fiber openings. That is, in the internal pressure circulation process using hollow fiber membranes, a large number of hollow fibers are housed in a housing, both ends of which are fixed with an adhesive, and sealed with the housing. Furthermore, the adhesive end is cut to provide an opening at the hollow fiber end. One opening is used as the stock solution supply port, and the part connected to a suitable liquid supply mechanism is used as the supply header. A similar part at the other end is a liquid drain header. Using such a device, the stock solution is circulated under pressure on the inner surface of the hollow fiber, and separation treatment is performed on the membrane surface. The present inventors have found that when performing internal pressure circulation treatment on hollow fiber membranes using various stock solutions, the openings at the ends of the hollow fibers often become clogged.
This clogging is particularly noticeable when processing stock solutions containing a large amount of solids. Therefore, the inventors of the present invention expected that the problem would be solved by first passing the stock solution through a filter to remove coarse solids and excessive solids, and then subjecting it to internal pressure circulation treatment. However, although some improvement was actually observed, the above-mentioned prefilter did not provide a fundamental solution. Based on this fact, the present inventors conducted intensive research and found that the object could be achieved by drastically changing the method of supplying the stock solution to the stock solution header, thereby completing the present invention. That is, the present invention provides a method for treating a fluid in which a stock solution is supplied to the inner surface of a hollow fiber membrane, in which a stock solution supply header is provided with one or more stock solution supply ports and one or more stock solution discharge ports, and the stock solution supply side and the stock solution discharge port are connected to each other. This is an improved method for supplying a stock solution, characterized in that the stock solution is supplied to a supply header while a portion of the stock solution is continuously or intermittently circulated through the connection circuit.

The present inventors investigated in detail the clogging of the hollow fiber end openings described above and found the following points.
First, on the header surface where the hollow fiber membranes are bundled and fixed with adhesive, the opening area of the hollow fibers is approximately 40% of the entire header surface.
% or less, and the adhesive and hollow fiber membrane thickness account for a very large portion. Therefore, when the solid content passes through the header surface, it is very easy for the solid content to accumulate in the area where the linear velocity of the liquid is the slowest and to form a large solid substance. In the present invention, this large solid substance is hereinafter referred to as scale. Even if a prefilter is used, this cannot be completely prevented since some particles pass through the mesh of the prefilter. The generated scale usually has poor fluidity and naturally disintegrates or peels off during backwashing, flows to the hollow fiber end opening, and causes blockage. Therefore, it is thought that the fundamental solution to this problem is to prevent scale formation on the header surface as much as possible. As a result of various studies for this purpose, the inventors of the present invention found that the liquid flow in the stock solution supply header tends to generate scale in a direction perpendicular to the header surface, and in order to prevent this, By applying a liquid flow component parallel to the header surface, scale formation can be prevented, and
It has been observed that even if scale is generated, the scale peels off before it becomes large enough to block the hollow fibers and smoothly flows through the inside of the hollow fibers, and the above-mentioned problem is greatly improved. Ta.

In the present invention, this problem is solved by providing a stock solution supply header with one or more stock solution supply ports and one or more stock solution discharge ports, forming a circulation circuit connecting these ports, and circulating a part of the stock solution to be supplied. did. That is, since a stock solution outlet is provided in the supply header and a part of the stock solution is discharged from the header, a flow is generated to the discharge port, and this flow provides a liquid flow component parallel to the header surface to prevent scale formation. It can be prevented. Circulating the stock solution flowing into the stock solution outlet to the stock solution supply side is necessary from an economical point of view and is not required from a technical point of view. The stock solution discharged from the stock solution outlet passes through the circulation circuit and returns to the stock solution supply port.
The circulation circuit can be installed by piping the stock solution outlet to the stock solution tank or the suction side of the stock solution delivery pump.

The stock solution supply header may have at least one stock solution supply port and one or more stock solution discharge ports, and their mounting positions may be such that the liquid flow from the stock solution supply port to the stock solution discharge port is parallel to the header surface. For example, it is preferable to provide them at the farthest distance so that they are both parallel to the header surface.

Discharging from the stock solution discharge port does not need to be carried out all the time, and may be carried out intermittently. In other words, if there are a lot of suspended solids or if scale formation is likely to occur, it is preferable to constantly discharge from the outlet, but if there are few suspended solids or scale formation is small, it is not necessarily necessary to constantly discharge. A sufficient effect can be obtained by intermittently discharging from the discharge port. When discharging the stock solution continuously from the stock solution discharge port, the amount of stock solution supplied to the stock solution supply port is 0.001 to 99%.
%, more preferably 1 to 50%. 0.001
% or less, the desired effect cannot be obtained. If it exceeds 99%, the amount of liquid actually treated by the hollow fiber membrane will decrease, making it uneconomical. When discharging intermittently, the amount of stock solution supplied to the stock solution supply port may be 100% or less. Furthermore, when backwashing other hollow fiber membranes with the stock solution supply solution, backwashing liquid is added and circulated.
Circulation volume can be 100% or more.

It will be easily understood that in the present invention, there are no particular limitations on the material and dimensions of the hollow fiber membrane, the structure of other parts of the fluid treatment device, etc.

Figures 1 and 2 are diagrams schematically showing the stock liquid header of the conventional device and the liquid flow within the header.
The figure is a similar schematic diagram illustrating one embodiment of carrying out the method of the invention. In Figs. 1 and 2, the supply header 1 is provided with a stock solution supply port 2, and the stock solution is sent from the stock solution tank 8 to the stock solution supply header by a liquid feed pump 9, and is approximately on the header surface 3 as shown in the streamlines. It flows vertically into the hollow fibers 4, 4'. On the other hand, in FIG. 3, a liquid flow is generated from the stock solution supply port 2 toward the stock solution discharge port 5, and a liquid flow component parallel to the header surface 3 is generated. The stock solution discharged from the stock solution outlet 5 passes through the circulation circuit 10 and returns to the stock solution supply side. Note that the present invention may be used in combination with backwashing of hollow fiber membranes. In FIGS. 1, 2, and 3, 6 is a stock solution discharge header, and 7 is a permeate outlet.

Furthermore, when using a large number of modules, it is a feature of the present invention to connect the stock solution outlet of one module to the stock solution supply port of the next module, and to connect the stock solution supply headers of several or dozens of modules. This is an effective way to bring out your characteristics. That is, the header surface of one module is washed away by the stock solution supplied to the next module and subsequent modules, thereby suppressing scale formation. Furthermore, the discharge amount from one or several stock solution discharge headers can be supplied to the stock solution supply port of the next module.

Processing liquids to which the present invention can be effectively applied are those containing a relatively large amount of suspended matter, such as emulsions, latexes, paints, soy sauces, sake, various fermented liquids, and suspensions of pigments and the like.

The present invention will be described in detail below with reference to Examples, but the present invention is not limited to the Examples.

Example 1 Inner diameter 1 mm, outer diameter to cut 50% of 450 Å particles
1.8mm polyvinyl alcohol hollow fiber membrane 1300
We bundled books and glued both ends with resin to create a module with a hollow membrane element with a total length of 1050 mm, a resin part length of 75 mm, and an effective membrane part length of 900 mm, which was housed in a case with an inner diameter of 90 mm. A header lid with a distance of 10 mm from the header surface was attached to one end of the module as shown in Figure 3. Inner diameter 40mm on the header in a direction almost perpendicular to the fiber direction of the hollow fiber and in a nearly symmetrical position.
Two pipes were installed. One is a stock solution supply port and one is a stock solution discharge port. A liquid drain header was attached to the other end of the module. The stock solution is sent from the stock solution tank to the stock solution supply port by a liquid sending pump, and is returned to the stock solution tank from the stock solution outlet and the stock solution discharge header.

One batch was 500 ml of dark soy sauce lees containing an average of 8000 ppm of suspended solids, and the above-mentioned operation was repeated to obtain 400 ml of liquid and 100 ml of concentrated lees per batch. The prefilter was installed between the liquid pump and the stock solution supply port, and an 80-mesh wire mesh was used.

The operating conditions are a constant pressure of 1.2 Kg/cm ² at the stock solution supply port, and a circulation flow rate of 3.5 m ² /
Adjusted to Hr. Furthermore, every 20 minutes of the filtration operation, so-called permeate backwashing was performed for 5 seconds in which a liquid was flowed from the outside to the inside of the hollow fiber membrane at a pressure of 2 kg/cm ² .

When the operation was performed with the discharge rate from the stock solution outlet 5 adjusted to 640/Hr (corresponding to 13% of the stock solution supply amount), no clogging of the hollow fiber end opening was observed even after 20 batches of operation. Yes, average overspeed is 70
/Hr and was able to operate stably. No clogging of the hollow fiber end openings was observed even after 10 batches of operation, indicating that stable operation could be achieved over a long period of time.

Comparative Example 1 The same soy sauce lees concentration test was repeated using the same apparatus as in Example 1 and the same operations except that the amount discharged from the stock solution outlet was set to zero. As a result, at the end of the two-batch operation, 60% of the hollow fiber end openings were blocked and it was impossible to continue the operation any further. The average overspeed is also 65/Hr for the first batch, 2
The number of splits got worse at 30/Hr.

Example 2 Using the same equipment as in Example 1, we prepared dark soy sauce containing an average of 8000 ppm of suspended solids in the same manner as in Example 1.
One batch was 500, and the operation operation was repeated to obtain 400 of liquid and 100 of concentrated sediment per batch.
As in Example 1, the permeate was backwashed for 5 seconds every 20 minutes of over-operation.

Discharge from the stock solution outlet 5 attached to the stock solution supply header was performed intermittently. In other words, overoperation 2
The stock solution outlet 5 was opened for 2 seconds every minute to discharge the stock solution. This stock solution discharge amount is 80% of the stock solution supply amount.
%.

As a result, no clogging of the hollow fiber end openings was observed after 10 batch operations, and no clogging of the hollow fiber end openings was observed even after 10 subsequent batch operations.

Example 3 Using the apparatus shown in Example 1, ethylene-vinyl acetate emulsion (manufactured by Kuraray Co., Ltd.) was added per batch.
Liquid 2000 containing 1% of OM emulsion #4000)
The operation was repeated to obtain 1900 ml of permeate and 100 ml of concentrated emulsion.

The operating conditions were to repeat over-operation and backwashing operations, and for over-operation, the pressure at the stock solution supply port was set to a constant pressure of 1.2 Kg/ ^cm2 , and the circulating flow from the stock solution discharge header was set to a liquid containing 1% emulsion. Adjusted to 4m ³ /Hr. The permeate was backwashed for 5 seconds at a pressure of 2 Kg/cm ² after every 30 minutes of over-operation.

When the discharge rate from the stock solution outlet was adjusted to 360/hr, the operation was successful, and no blockage of the hollow fiber end opening was observed even after 10 batches of operation, and the same was true after 10 batches of operation. It was hot.

Comparative Example 2 The same emulsion concentration test was repeated using the same equipment as in Example 3, using the same operations, except that the amount discharged from the stock solution outlet was eliminated. As a result, after 5 batches of operation, 10% of the hollow fiber end openings were found to be clogged, and after 5 batches of operation,
50% occlusion of the hollow fiber end opening was observed.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams showing the conventional method,
FIG. 3 is a schematic diagram showing one embodiment of the present invention.

Claims (1)

[Claims] 1. In a method of treating a fluid by supplying a stock solution to the inner surface of a hollow fiber membrane, a stock solution supply header is provided with one or more stock solution supply ports and one or more stock solution discharge ports, and the stock solution supply side and the stock solution discharge port are connected, An improved method for supplying a stock solution, characterized in that the stock solution is supplied to a supply header while a portion of the stock solution is continuously or intermittently circulated through the connection circuit.