JPH04190834A - Cross-flow type filter - Google Patents

Abstract

PURPOSE:To separate only an object continuously and selectively utilizing the selectivity of a membrane by providing a supporting body for a filter membrane on the side where an original fluid flows to constitute a cross-flow type filter. CONSTITUTION:When an original fluid containing suspended matters is fed to a filter membrane 4 in cross-flow relationship therewith and filtered so that the fluid is separated into a fluid and suspended matters, a supporting body 7 for the membrane is provided on the original fluid side of the membrane 4 and further a diffusion plate 6 for uniformly feeding the fluid over the membrane is provided to constitute a cross-flow type filter. By providing such supporting body, even when back washing is performed intermittently to eliminate or reduce forces acting perpendicularly on the surface of the membrane 4 and hence pressure fluctuation occurs, the membrane is not deformed and cake layers or deposition layers can be removed easily and as a result a flux of high membrane permeation can be obtained. The plate 7 reduces fluid resistance from an inlet port 1 for the fluid to the membrane surface to uniformize the flow of the fluid over the membrane and also forms a passage of relatively large resistance uniformly with respect to the membrane at a point just before the fluid contacts the membrane surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cross-flow filtration method, and particularly to a cross-flow filtration method that maintains a large membrane permeation flux.

The cross-flow filtration method of the present invention is applied to the separation, purification, recovery, concentration, etc. of fluids containing or suspending various polymers, microorganisms, yeast, and fine particles. It can be applied in any case where it is necessary to separate fine particles from a fluid containing them, such as in various suspensions containing fine particles, fermentation liquids or culture liquids, as well as suspensions of pigments, etc. It is also applied in the case of separation, and purifies the gas by separating and removing fine particles from suspended gas containing fine particles.For example, sterilizing nitrogen gas to be filled into pharmaceutical ampoules, positive pressure gas for ultrapure water production equipment. dust-free, sterile gas or IC to fill as
! ! It is also applied to the production of air-conditioned, dust-free, and sterile air in production lines.

(Prior Art) Conventionally, techniques for separating suspended solids from a raw fluid containing suspended solids using a membrane include, for example, reverse osmosis, ultrafiltration, microfiltration, which uses pressure as a driving force. There are electrodialysis methods that use a potential difference as a driving force, and diffusion dialysis methods that use a concentration difference as a driving force. These methods can be operated continuously, can separate, purify, or concentrate without significantly changing temperature or pH conditions during the separation operation, and can separate a wide range of particles, molecules, ions, etc. It is economical because it can maintain a large processing capacity in a small plant, requires little energy for separation operations, and can process low-concentration raw fluids that are difficult to use with other separation methods, so it has been widely implemented. There is. The membranes used in these separation techniques include polymer membranes mainly made of organic polymers such as cellulose acetate, cellulose nitrate, regenerated cellulose, polysulfone, polyacrylonitrile, polyamide, and polyimide, as well as those with heat resistance, chemical resistance, etc. There are porous ceramics, membranes, etc. that have excellent durability.Ultra tL filtration membranes are used mainly for colloid filtration, and precision III filtration membranes are used for fine particle filtration. Microfiltration membranes with suitable micropores are used.

By the way, in recent years, with the progress of biotechnology, high purity, high performance, and high tI? 'E is now required, and precision filtration or ultra-filtration! The field of application of advanced technology is expanding. However, when separating fine particles using a membrane in precision filtration or ultrafiltration, a cake layer forms due to the influence of concentration polarization, creating resistance to the flow of the permeate fluid, and resistance due to membrane clogging. growing bigger and membrane i
! There is a problem in that the i-filtration flux decreases rapidly and significantly, and this has been the biggest cause of hindering the practical application of fine air filtration or ultrafiltration. Furthermore, the membrane used therein is easily contaminated, and measures to prevent this are required. As a filtration method, there is a so-called Punto End filtration method in which all the fluid to be filtered passes through a filter medium (filter cloth, membrane, etc.) and a cake layer to separate fine particles contained in the fluid.

In this dead-end filtration system, in order for the fluid to pass through and the suspended solids to be separated, pressure must be applied to overcome the resistance of the filter medium and cake layer that impedes the flow of the fluid, and for this reason, microfiltration or ultrafiltration is required. In filtration, if such dead-end filtration is performed, the membrane permeation flux becomes small. For this reason, a cross-flow type filtration method was considered. This cross-flow filtration method
The raw fluid to be filtered is passed parallel to the membrane surface of the filtration membrane, and the fluid permeates through the filtration membrane to the opposite side. It is so called because the flow of the raw fluid and the permeated fluid are perpendicular to each other. There is.

In this cross-flow type filtration method, the cake layer formed on the membrane surface is stripped off by the flow of the raw fluid parallel to the membrane, so the WJ and permeation flux are larger than in the conventional dead-end type filtration method. , it is possible to directly and continuously separate, purify, and concentrate a large amount of raw fluid, and there is no need for floc generation to improve filtration, so it is collected! l! It has the characteristics of not being contaminated with turbid substances, and by controlling the interaction between the membrane's micropore size and the target substance, an extremely pure filtration fluid can be obtained.

(Problem to be solved by the invention) As mentioned above, the cross-flow filtration system is an advanced separation technology in principle, but the biggest problem, the membrane permeation flux, is due to the dead-end filtration system. Although this is relatively large, there is a problem in that even if this cross-flow method is adopted as a precision filtration method, a sufficiently high membrane permeation flux cannot be obtained.

In addition, looking at specific examples of conventional methods for separating Qi from animal fluids, for example, when separating bacterial cells from fermentation liquid, conventional centrifugation methods, cake filtration methods, diatomaceous earth filtration methods, etc. Primary filtration and secondary filtration such as microfiltration are used together, but it is difficult to make the process continuous when separating bacterial cells, etc., and products such as enzymes are strongly adsorbed to the filter aid, making it difficult to recover them. When bacterial cells are collected by microfiltration, which is secondary filtration, the membrane permeation flux decreases as the filtration time passes due to a cake layer or clogging that forms on the membrane surface, and further centrifugation. There was a problem that the isolation method resulted in loss of bacterial activity.

In order to solve these problems, conventional methods have been used to intermittently stop the flow of raw fluid into the filtration membrane, or to close the valve on the permeate side of the filtration membrane. By intermittently removing or reducing the pressure, or by applying pressure from the permeate side of the filtration membrane to flow the fluid from the permeate side to the raw fluid side, the membrane surface on the raw fluid side of the filtration membrane is deposited. Attempts have been made to remove the cake layer and adhesion layer intermittently called "backwashing". However, when these backwashings are performed, the pressure difference between the raw fluid side and the permeate side of the filtration membrane changes , the filtration membrane stretches and the membrane surface on the raw fluid side comes into contact with the filter, causing problems such as not being able to remove the cake layer or adhesion layer sufficiently, and reducing the blocking performance of the filtration membrane.Furthermore, the strength of the filtration membrane decreases. If it was weak, there was a risk that the filtration membrane would break and the substance would pass through to the permeate side.

On the other hand, since the flow path resistance from the raw fluid inlet to the membrane surface of the filter and from the membrane surface to the outlet are not necessarily equal, the flow becomes uneven on the membrane surface and the effective membrane area is reduced. This caused the problem that an economical permeation flux could not be obtained.

(Means for Solving the Problems) The present invention has been made to solve the problems of the prior art described above, and is a novel loss-flow type that has a practical and high membrane permeation flux. The purpose is to provide a filter.

That is, the present invention provides a cross-flow type filtration method in which a raw fluid consisting of a fluid containing suspended matter is supplied to a filtration membrane in a cross-flow manner and filtered to separate the fluid and suspended matter. This is a cross-flow type filter characterized in that a support body for a filtration membrane is provided on the raw fluid side, and a diffusion plate is provided for uniformly supplying the raw fluid onto the membrane surface.

The present invention will be explained in detail below.

The present invention is an improvement on the prior art cross-flow type filter, and the basic steps have already been explained in detail in the "Prior Art" section.

A feature of the present invention is that in the cross-flow filtration system, a support for the filtration membrane is provided on the raw fluid side of the filtration membrane of the cross-flow filtration device. The support provided on the source fluid side is preferably one that does not obstruct the flow of the source fluid, and protrusions are provided at positions in contact with or close to the membrane in a direction parallel to the flow of the source fluid.

The shape of the protrusions should not significantly obstruct the flow of the raw fluid, but linear or dot-like shapes are preferable, and the protrusions should be placed 5m from the membrane surface.
It is preferable to exist at a position of m or less. Further, the support may be a mesh body or a nonwoven fabric as long as it does not significantly impede the flow of the raw fluid.

By providing a filtration membrane support on the raw fluid side in this way, even if pressure fluctuations occur during "backwashing", which intermittently eliminates or reduces the pressure applied perpendicular to the membrane surface of the filtration membrane, , cake layers and adhesion layers that cause membrane deformation can be easily removed, resulting in a high membrane permeation flux.

In addition, in the diffusion plate of the present invention, since the raw fluid flows uniformly on the membrane surface, the flow path resistance from the raw fluid inlet to the membrane surface is reduced, and the raw fluid has a relatively high resistance just before it comes into contact with the membrane surface. It is characterized by forming a large flow path uniformly over the membrane surface. In order to increase the flow resistance just before the raw fluid contacts the membrane surface, the shape of the diffusion plate is determined by either providing a plurality of conductive holes uniformly across the membrane surface, or by providing a network of conductive holes with a lower opening rate than the inlet opening. A body or non-woven fabric may also be used.

Next, the cross-flow filter of the present invention will be explained based on the drawings. FIG. 1 shows the flow of raw fluid on the membrane surface of a normal cross-flow filter, and FIG. 2 shows the A cross section of cycle 1, which shows the deformation of the membrane when backwashing is performed. In this manner, it can be seen that in conventional cross-flow filters, the flow of raw fluid on the membrane surface is non-uniform, and deposits cannot be removed due to deformation of the membrane during backwashing. Figure 3 shows the flow of raw fluid on the membrane surface of the cross-flow filter of the present invention, and Figure 4 shows the cross-section A in Figure 3 in a backwashed state, and the flow is uniform and during backwashing. Deposits can be easily removed.

Furthermore, the present invention will be specifically explained. Circle 5 is a block diagram of the cross-flow type filter of the present invention, which is composed of an upper plate, a diffusion plate, a lower plate, and an i3 filtrate side membrane support. FIG. 6 is a view of the upper plate of the cross-flow filter of the present invention viewed from the side where the raw fluid flows, and a filtration membrane support is provided in a direction parallel to the flow direction of the raw fluid. FIG. 7.8 shows cross sections A and B in FIG. 6, and the filtration membrane support is located almost in contact with the filtration membrane so as not to impede the flow of the stock fluid. The shape of this filtration membrane support does not matter as long as it does not impede the flow of the raw fluid, as long as it can prevent the filtration membrane from deforming during pressure fluctuations. Figure 9 shows permeation through the lower plate of the cross-flow filter of the present invention. It is a view seen from the side through which the liquid flows, and grooves are formed through which the permeated fluid flows. Figure 10.11 shows cross sections A and B in Figure 9. FIG. 12 shows a diffusion plate that is fitted into the upper plate, and is provided with a plurality of communication ports for forming flow paths for raw fluid on the membrane surface. FIG. 13 shows cross section A in FIG. 12.

(Example) The present invention will be explained in more detail by giving specific examples below.
The present invention is not limited to this.

Example Escherichia coli (IFO-3301) was dispersed in Q, 9 wt/% physiological saline at a content of ldryg/I and filtered through a microfiltration membrane with a nominal pore size of 0.2 μm. Flow filtration was performed.

The module used was a thin layer flow channel type with an effective membrane area of 100 cm, and the experimental conditions were a pressure difference of 0.5 x 10'Pa,
The raw fluid flow rate was 101/+sin, and the liquid temperature was 25°C. A filtration was performed according to the flow shown in FIG. 14, and after the start of filtration, the pump for feeding the raw fluid was intermittently stopped to perform backwashing. The results of an operation in which the pump was operated for 150 seconds and stopped for 30 seconds are shown together with a comparative example in which the ring 15 is not provided with a support for supporting the filtration membrane.

In the comparative example, one hour after the start of filtration, the permeation flux decreased to the initial level of 1.
In contrast, when the support was provided, the initial permeation flux was maintained.

(Effects of the Invention) According to the present invention, basically a high membrane permeation flux can be obtained in a cross-flow type filtration system, thereby making it possible to separate and recover each suspended component from a liquid containing various suspended substances. , purification, concentration, etc. can be carried out extremely efficiently and economically. Furthermore, it is possible to make the process continuous and downsize the equipment, and by utilizing the selectivity of the membrane, it is possible to continuously and selectively separate only the target substance, making it possible to remove yeast and bacterial cells from the reaction solution. By immobilizing it, it can be applied to bioreactors, and compared to conventional technology, it is easier to manage and operate at higher concentrations, and there is no need for special cleaning to restore membrane permeability. Various effects can be produced.

[Brief explanation of the drawing]

The first circle shows the flow of the raw fluid on the membrane surface of a normal cross-flow filter, and the second figure shows the A section in Figure 1, which shows the deformation of the membrane when backwashing is performed. There is. Figure 3 shows the flow of the raw fluid on the membrane surface of the cross-flow filter of the present invention.
The figure shows cross-section A in FIG. 3 in a backwashed state. Fifth
The figure is a block diagram of the cross-flow filter of the present invention, which is composed of an upper plate, a diffusion plate, a lower plate, and a membrane support on the permeate side. FIG. 6 is a view of the upper plate of the cross-flow filter of the present invention viewed from the side where the raw fluid flows, and a filtration membrane support is provided in a direction parallel to the flow direction of the raw fluid. Figures 7 and 8 are 6
It shows cross sections A and B in the figure. FIG. 9 is a view of the lower plate of the cross-flow filter of the present invention viewed from the side through which the permeate flows, and grooves are formed through which the permeate flows. 10 and 11 show cross sections A and B in FIG. 9. FIG. 12 shows a diffusion plate that is fitted into the upper plate, and is provided with a plurality of communication ports for forming flow paths for raw fluid on the membrane surface. Figure 13 is A of Figure 12.
It represents a cross section. FIG. 14 shows an example of a cross-flow filtration device for implementing the filter of the present invention. FIG. 15 shows a comparison of changes in permeation flux over time when using the filter of the present invention and a conventional filter. (Explanation of symbols) 1...raw fluid inlet 2...raw fluid outlet 3...+3 filter, outlet 4...filter membrane 5 ... Deposit 6 ... Diffusion plate 7 ... Raw fluid side membrane support 8 ... Upper layer 9 ... Lower plate 10 ... Permeated liquid side membrane support 11 ... Screw fixing holes Patent applicant Fuji Photo Film Co., Ltd. Figure 1 I Figure 2 Figure 3 Figure 4 Figure 6 Figure 8 -! Hiki

Claims (1)

[Scope of Claims] 1) A filtration method in which a fluid and suspended matter are separated by supplying a raw fluid consisting of a fluid containing suspended matter to a filtration membrane in a cross-flow manner and filtering the raw fluid. A cross-flow filter characterized in that a support for a filtration membrane is provided on the side through which fluid flows. 2) The cross-flow filter according to claim 1, wherein the support is a plurality of projections located in a direction parallel to the flow of the raw fluid. 3) The cross-flow filter according to claim 2, further comprising a diffusion plate for allowing the raw fluid to flow uniformly over the membrane surface between the protrusions.