JPH04145929A - Cross-flow filter - Google Patents

Abstract

PURPOSE:To obtain a high membrane-permeable flux and to efficiently and economically carry out the separation, recovery, refining, concentration, etc., of the suspended matter by providing a filter membrane support on the raw fluid contg. suspended matter side of the membrane. CONSTITUTION:A filter membrane support is provided on the raw fluid side of the membrane of the cross-flow filter. The flow of the raw fluid must not be disturbed by the support, and hence a protrusion is formed on or close to the membrane in parallel with the raw fluid flow. The shape of the protrusion is determined so that the raw fluid flow is not considerably disturbed, and a linear and/or dotted shape is preferably used. Since such a support is provided, the membrane is not deformed in backwashing, the cake and deposit are easily removed, and consequently a high membrane-permeable flux is obtained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a cross-flow type filter,
In particular, the present invention relates to a cross-flow type filter that maintains a high membrane permeation flux.

The cross-flow type filter of the present invention can separate fluids containing or suspending various polymers, microorganisms, yeast, and fine particles.
It can be applied in purification, recovery, concentration, etc., and in particular in any case where it is necessary to separate fine particles from a fluid containing fine particles that requires filtration, such as in various suspensions containing fine particles. In addition to liquids, fermented liquids, culture liquids, etc., it is also applied to the separation of fine particles from suspensions of pigments, etc. It is also used to purify gases by separating and removing fine particles from suspended gases containing fine particles, e.g. For the production of sterilized nitrogen gas filled into pharmaceutical ampoules, dust-free and sterile gas filled as positive pressure gas into ultrapure water production equipment, and dust-free and microorganism-free air for air conditioning in IC production lines. also applies.

(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, and can perform separation, purification, or acondensation without significantly changing the temperature or pH conditions during the separation operation, and are capable of separating a wide range of particles, molecules, and ions. It is economical because it can maintain large processing capacity even with a small blunt, and it is widely used because the energy required for separation operation is small and it is possible to process low-concentration raw fluids that are difficult to use with other separation methods. It has been implemented. 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 membranes with heat resistance, chemical resistance, etc. There are porous ceramic membranes with excellent durability, ultrafiltration membranes are mainly used for colloid filtration, and precision filtration membranes have micropores suitable for filtration of fine particles. A microfiltration membrane is used.

In recent years, with the progress of biotechnology, higher purity, higher performance, and higher precision have been required, and the fields of application of microfiltration or ultrafiltration technology are expanding. However, when separating fine particles using a membrane in microfiltration or ultrafiltration, a cake layer is generated due to the influence of concentration polarization, creating resistance to the flow of the permeate fluid.
There is also the problem that the resistance due to membrane clogging increases and the membrane permeation flux suddenly and significantly decreases.
This was the biggest reason for preventing the practical application of precision 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 dead-end filtration method in which all the fluid to be filtered is filtered through a filter medium (filter cloth, membrane, etc.) and a cake layer to separate suspended substances 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, fluid pressure is required to overcome the resistance of the filter media and cake layer that impedes fluid flow. In filtration, if such dead-end filtration is performed, the membrane permeation flux becomes small. For this reason, it was considered that the cross-flow type filtration method could also be applied to the precision filtration method. In this cross-flow type filtration method, the raw fluid to be filtered is passed parallel to the membrane surface of the filtration membrane in the axial direction of the membrane, and the fluid is filtered to the opposite side through the filtration membrane. This is a filtration method in which the fluid flows parallel to the filtration membrane, and the filtered fluid flows perpendicularly to the filtration membrane surface, so called because the two flows are exactly perpendicular to each other.

In this cross-flow type precision filtration method, the cake layer formed on the membrane surface is peeled off by the flow of the raw fluid parallel to the membrane, so the membrane permeation flux is larger than the conventional dead-end filtration method, and a large amount of It is possible to directly and continuously separate, purify, and concentrate the raw fluid of By controlling the interaction between the micropore size and the target substance, extremely pure filtration fluid can be obtained.

For cross-flow type filtration membranes, please refer to Special Publication No. 5210113
No., JP 53-3756, JP 64-22307
No. 58-14919.

However, these membrane modules have a flat membrane stretched on both sides of the membrane plate, and the module units of the membrane plate are arranged side by side on the same axis with a gap between them, and backwashing operations such as backflowing the permeated liquid are performed. Otherwise, there was a risk that the membrane would be deformed and its performance would change, or that the membrane would break and the raw fluid would flow out to the permeate side.

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

In addition, looking at specific examples of conventional separation of suspended solids and fluids, for example, when separating bacterial cells from fermentation liquid, conventional centrifugation, cake filtration, and diatomaceous earth filtration methods are used. Primary filtration, such as filtration, and secondary filtration, such as microfiltration, are used together, and during this, yeast that tends to flocculate and settle is used for sedimentation separation, and the yeast is reused. It is difficult to make the process continuous when separating bacterial cells, and the recovery rate decreases due to strong adsorption of enzymes and other products to the filter aid. However, there were problems in that the membrane permeation flux decreased with the passage of filtration time due to the cake layer formed on the membrane surface and clogging of the membrane, and furthermore, the activation of bacterial cells was lost due to the centrifugation method.

For example, in the biological treatment of sewage, the activated sludge produced contains a large amount of water, so it is first concentrated before further treatment. For components larger than the colloidal components, coagulation and sedimentation is performed, and metal ions among the dissolved components are insolubilized as hydroxides, oxides, sulfides, etc., and are separated by sedimentation after being made into a size larger than that of the colloid. ,
Solid-liquid separation of activated sludge is performed by further separating the liquid from the a-condensate obtained here, but in order to carry out advanced treatment in the concentration of such activated sludge, extensive equipment is required for sedimentation. The process was complicated, the operation and management of solid-liquid separation required advanced technology, and a large area was required to dispose of the large amount of sludge generated. .

In order to solve these problems, conventional methods have been to intermittently stop the flow of the raw fluid (filtration stock solution in which suspended substances are dispersed) into the filtration membrane, or to close the valve on the permeate side of the filtration membrane. By closing, the pressure applied perpendicular to the membrane surface of the filtration membrane is intermittently eliminated or reduced, or by applying pressure from the permeate side of the filtration membrane and flowing fluid from the permeate side to the raw fluid side, Attempts have been made to intermittently remove the cake layer and (-1 adhesion layer) deposited on the membrane surface on the raw fluid side of the filtration membrane. , the pressure difference between the raw fluid side and the permeate side of the filtration membrane fluctuates, causing the filtration membrane to stretch and the membrane surface on the raw fluid side to come into contact with the filter, resulting in insufficient removal of the cake layer or deposited layer, or damage to the filtration membrane. Problems such as failure to achieve the original function occurred, and furthermore, if the strength of the filtration membrane was weak, there was a risk that the filtration membrane would break and suspended matter would pass through to the permeate side.

(Means and effects for solving the problem) The present invention is
- This was done in order to solve the problems of the prior art mentioned above, and the purpose is to provide a new loss-flow type filter with a practical and high membrane permeation flux. be.

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 suspension membrane in a cross-flow manner and filtered to separate a fluid and suspended matter. This is a cross-flow filter characterized in that a support for the filtration membrane is provided on the raw fluid side of the filtration membrane.

Here, the support is a support that suppresses the deformation of the membrane when performing an operation called backwashing, which removes the adhesive layer deposited on the membrane, such as removing the pressure applied to the membrane or causing the permeate to flow backwards. Attach it to the fluid side.

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 a cross-flow filtration system, a filtration membrane support is provided on the raw fluid side of the filtration membrane of a 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 protrusion does not need to significantly impede the flow of the raw fluid, preferably a linear shape, and preferably located at a position of 35 mm or less from the membrane surface.

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.

Note that the amount of fluid passing through a filtration membrane per unit time is measured in terms of the fluid, but since that amount varies depending on the area of the filtration membrane, the flow rate is divided by the area of the membrane, and that amount is called the membrane filtration flux [ Unit: m/sec].

The filtration membrane used in the present invention has micropores with a pore diameter of 10 μm or less, preferably 5 μm or less, and the actual use depends on the type of fluid stock solution containing suspended solids to be filtered. ζ Select the optimal pore size.

The suspended matter referred to herein includes both inorganic and organic substances, including microorganisms and yeast, and when an ultrafiltration membrane is used as the filtration membrane, it also includes proteins, polymers, and the like.

The fluid to be filtered may be a gas in addition to a liquid, but it is particularly frequently used for liquids. Any fine particles contained in the liquid can be removed as long as they can be removed by filtration, but since coarse particles can be separated and removed by ordinary filtration, it is most effective to separate and remove fine particles. Further, the shape of the membrane does not matter whether it is a flat membrane or a tubular 1 hollow system.

In order to perform filtration, it is necessary to apply a certain amount of pressure to the fluid to be filtered, but if the pressure is low, the membrane permeation flux will not recover much, so it is preferable to apply a certain amount of pressure. For E. coli suspensions, a pressure of 0.5 kg/cTM was best. Although the percentage of solute in the suspension solution in the suspension is not particularly limited in this technique, it is usually 0.1% or more.

Furthermore, the simplest way to intermittently apply pressure to the permeate fluid on the permeate side of the filtration membrane is to intermittently close a valve placed in the pipe through which the permeate fluid flows, and this can also be done manually. However, it is usually convenient to use a solenoid valve.

Next, a filtration method when using the cross-flow type filter of the present invention will be explained based on the drawings. FIG. 1 is an explanatory diagram showing the concept of a mechanism of an example of a device for implementing the filter of the present invention. In the figure, a suspension in a supply tank 1 is circulated via a flow path 2 by a pump 3 through a module 5 containing a filtration membrane. At this time, the pressure of the suspension is adjusted to a filtration pressure of preferably 0.01 to 5 k by the pressure regulating valve 8.
Adjust so that it is within the g/cf+ range. This pressure is read by a pressure gauge 4, and the flow rate of the liquid is read by a flow meter 9. The method of applying pressure intermittently can be performed by intermittently turning on the power of the motor that drives the valve 11. 6 is a flow path for the separated liquid, 7 is a pressure side,
9 is a flow meter, and 10 is a storage tank for the separated liquid. In this way, a high membrane permeation flux can be maintained through cross-flow filtration, but it usually depends on the filtration time, filtration pressure, flow rate, temperature of the fluid, etc.

Therefore, in order to have the desired performance, the type of fluid containing suspended solids and the properties of the filtration membrane are appropriately selected. Traditionally, membranes have been washed or backwashed to restore their performance, but washing requires draining all the fluid to be filtered, and both require pumps for washing or backflowing the fluid. However, the apparatus used in the present invention does not require these.

Next, the cross-flow filter of the present invention will be explained based on the drawings. FIG. 2 shows a cross-sectional view of a typical cross-flow filter, showing suspended solids forming a cake layer on the membrane surface.

FIG. 3 is a top view of the cross-flow filter of the present invention, in which a filtration membrane support is provided in a direction parallel to the flow direction of the raw fluid. FIG. 4.5 shows cross sections A and B in FIG. 3, 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 suspension membrane support may be of any shape as long as it does not inhibit the flow of the raw fluid, as long as it prevents the filtration membrane from deforming during pressure fluctuations.

(Example) A suspension in which E. coli (IFO-3301) was dispersed in 0.9 wt% physiological saline at a content of 1 dry g/1 was used, and the nominal pore size was 0.9 wt%. Cross-flow filtration was performed using a 2 μm microfiltration membrane.

The module used was a thin layer flow path type with an effective membrane area of 100 cJ, and the experimental conditions were a pressure difference of 0.5 x 10'Pa and a flow rate of raw fluid of 10 I! ,/min, and the liquid temperature was 2.5°C. After the filtration was started, the pump that sent the raw fluid was stopped intermittently to perform backwashing. The results of an operation in which the pump was operated for 150 seconds and stopped for 30 seconds are shown in FIG. 6 together with a comparative example in which no support was provided to support 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 the bioreactor, it is possible to react to the bioreactor, and compared to conventional technology, operation management is easier and operation at higher concentrations is possible, and there is no need to reduce the filtration area of the membrane (to restore the permeability of the membrane). Various effects can be achieved, such as no special cleaning required.

[Brief explanation of drawings]

FIG. 1 shows an example of a cross-flow filtration device for implementing the filter of the present invention. FIG. 2 shows a cross-sectional view of the cross-flow filter, showing a state in which suspended solids form a cake layer on the membrane surface. FIG. 3 is a view of the cross-flow filter of the present invention viewed from the -L section, in which a filtration membrane support is provided in a direction parallel to the flow direction of the raw fluid. FIG. 4.5 shows cross sections A and B in FIG. 3, and the filtration membrane support is located almost in contact with the filtration membrane so as not to inhibit the flow of the raw fluid. Patent applicant Fuji Photo Film Co., Ltd. Procedural amendment 1゜Display of the case 1990 Japanese Patent Application No. 89382 2゜Name of the invention Cross-flow filter 3゜Relationship with the case

Claims (1)

[Claims] In a filtration method in which fluid and suspended matter are separated by supplying a raw fluid containing suspended matter to a filtration membrane in a cross-flow manner and filtering it, a filtration membrane is provided on the side through which the raw fluid flows. A cross-flow filter characterized by being provided with a support.