JPH0584429A - Membrane separator - Google Patents

Abstract

PURPOSE:To prevent lowering of membrane permeation flux in a lapse of time by removing a cake layer, which sticks on a surface of a separation membrane, without using special power or a cleaning member. CONSTITUTION:In the membrane separator, plural filtration membrane unit 21 is provided in the tight closed vessel 11. The inflow opening 16 of a solution to be treated and the outflow opening 17 of a concentrated solution are provided through the outside case 12 in the inside case 13 of the tight closed vessel 11. The filtration membrane unit 21 consists of the hollow rotary shaft 22 and the cylindrical separation membrane 23 provided on the outer circumferential surface of the hollow rotary shaft 22. The hollow rotary shaft 22 is supported freely rotatably with the bearing 24 through the tight closed vessel 11, the hollow rotary shaft 22 adjacent to each other are closely arranged in parallel and the communicating hole 26 is formed to introduce the permeating solution, which permeates the cylindrical separation membrane 23 at regular interval in axial direction, into the hollow part 25, in which the permeating solution flows as a passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separator used for concentrating bacterial cells in a bioreactor, for example.

[0002]

2. Description of the Related Art Membrane separation is used in bioreactors and the like as an energy-saving separation method that does not involve phase separation. An apparatus for performing such membrane separation is disclosed in Japanese Patent Laid-Open No. 1-215.
308, JP-A-62-180706 or JP-A-61-138505. All of these are provided with a rotating filtration membrane unit in a closed container, and a liquid to be treated such as a culture solution introduced into the closed container is brought into contact with the filtration membrane unit, and separated into a permeated liquid and a concentrated liquid by a filtration membrane. It is collected or circulated.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The filtration membrane unit of the membrane separation device disclosed in Japanese Patent Application Laid-Open No. 8 and Japanese Patent Application Laid-Open No. 62-180706 has a structure in which a large number of hollow fiber separation membranes are arranged around the rotation axis as a center. For this reason, the shear stress applied to the liquid to be treated is different between the separation membrane near the rotation axis and the separation membrane at the far position, and the treatment liquid containing a substance vulnerable to the shear stress such as microorganisms and cells is separated. Has a great disadvantage. Further, since a large number of hollow fiber separation membranes are arranged, it is difficult to remove the fouling layer such as the cake layer or gel layer attached to the surface of the inner hollow fiber separation membrane.

On the other hand, in the membrane separation device disclosed in Japanese Patent Laid-Open No. 61-138505, a fouling layer is removed by bringing a cleaning member such as a sponge into contact with the surface of a separation membrane stretched on a drum. However, this not only adds a mechanism for washing, but also a member such as a sponge comes into direct contact with the separation membrane, so that the life of the membrane is extremely shortened. Incidentally, backwashing and washing with chemicals are disclosed in JP-A-61-1385.
As described in Japanese Patent Publication No. 05, there are various problems such as having to stop the operation.

[0005]

In order to solve the above problems, the present invention is directed to arranging filter membrane units provided in a closed container having an inlet for a liquid to be treated and an outlet for a concentrated liquid in close proximity to each other. And a plurality of hollow rotating shafts that rotate in the same direction, and a cylindrical separation membrane mounted on the outer peripheral surface of the hollow rotating shafts.

[0006]

Since each of the filtration membrane units rotates in the same direction, the membrane surfaces run in opposite directions in the gaps between the facing portions that are close to each other, and as a result, a vortex is generated in the gaps and shearing of the vortex flows occurs. The stress removes the fouling layer attached to the surface of the separation membrane.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a diagram showing an example of a filtration system to which the membrane separation device according to the present invention is applied, FIG. 2 is a sectional view of the membrane separation device, and FIG. 3 is a sectional view taken along line AA of FIG.

The filtration system stores the liquid to be treated in the storage tank 1, and supplies the pressurized liquid from the compressor 2 equipped with the aseptic filter 3 to the storage tank 1 to supply the liquid to be treated through the pipe 4 to the present invention. Is supplied to the membrane separation device 10 according to the above, and the liquid to be treated is separated into a permeated liquid and a concentrated liquid by the membrane separation device 10. The concentrated liquid is returned to the storage tank 1 through the pipe 5, and the permeated liquid is supplied through the pipe 6. The permeated liquid storage tanks 7a, 7b and 7c are used to store them. still,
The permeated liquid storage tanks 7b and 7c are connected to a vacuum pump 8.

The membrane separation device 10 has a plurality of filtration membrane units 21 arranged in a closed container 11. The closed container 11 has a jacket structure consisting of an outer case 12 and an inner case 13. The outer case 12 has an inlet 14 for hot water for temperature control.
And an outlet 15 are provided, and the inner case 13 has an outer case 1
An inlet 16 for the liquid to be treated and an outlet 1 for the concentrated liquid passing through 2.
7 is provided.

Here, in addition to the box-like or cylindrical shape of the closed container 11 as shown in FIG. 3, the bulging portion 11a for accommodating one filtration membrane unit 21 as shown in FIG. The shape may be continuous. By doing so, Taylor vortices are generated in portions other than the facing portions of the adjacent filtration membrane units 21, 21, and the scraping effect of the fouling layer is enhanced.

On the other hand, the filtration membrane unit 21 comprises a hollow rotary shaft 22 having a hollow portion 25 and a cylindrical separation membrane 23 mounted on the outer peripheral surface of the hollow rotary shaft 22. Hollow rotating shaft 22
Is rotatably supported through the sealed container 11 via a bearing 24, adjacent hollow rotating shafts 22 are arranged in parallel with each other, and the hollow portion 25 serves as a permeate passage.
Communication holes 26 for guiding the permeated liquid that has permeated the tubular separation membrane 23 to the hollow portion 25 at equal intervals in the axial direction are formed.

A pulley 27 is fitted to one end of the hollow rotary shaft 22, and the pulley 27 and a pulley 29 rotated by a motor 28 are connected by a belt 30 to make the motor 2
The hollow rotary shaft 22 of each filtration membrane unit 21 by the driving force of 8
Is designed to rotate in the same direction. It should be noted that the motor 28 is not provided for each filtration membrane unit 21, and the driving force of one motor 28 is applied to the shaft 31 and the gear train 32 as shown in FIG.
It may be transmitted to each of the hollow rotary shafts 22 via ... And rotate in the same direction. Further, the number of the filtration membrane units 21 is not limited to the two or three shown in the figure, and may be more.

The tubular separation membrane 23 is screwed to the outer peripheral surface of the hollow rotary shaft 22 by a nut member 34 via an O-ring 33. The cylindrical separation membrane 23 is made of, for example, ceramic,
The structure has a multilayer structure in which a porous layer having a pore size of 0.01 to 5 μm is formed on a support layer having a pore size of 10 to 100 μm. If you want to remove high-molecular components, select an ultrafiltration membrane. It is also possible to use metal or plastic as the material of the tubular separation membrane 23.

In the above, the liquid to be treated in the storage tank 1 is supplied into the closed container 11 of the membrane separation device 10 and each filtration membrane unit 21 is rotated in the same direction. Then, the treatment liquid is separated into the permeated liquid and the concentrated liquid by the same mechanism as the cross-flow filtration in which the treated liquid flows along the membrane surface, the concentrated liquid is returned to the storage tank 1 again, and the permeated liquid is filtered through the filtration membrane unit. It is stored in the permeated liquid storage tank through the tubular separation membrane 23 of 21, the communication hole of the hollow rotary shaft 22 and the hollow portion 25.

Since each of the filtration membrane units 21 rotates in the same direction, the surfaces of the separation membranes 23 run in opposite directions in the gap between the facing portions as shown in FIG. Then, in the vicinity of the surface of the separation membrane 23, a fluid flow distribution, that is, a boundary layer is formed by being dragged by the traveling of the membrane, and the boundary layers of the adjacent filtration membrane units act on each other to generate a vortex as shown in the figure. The vortex removes the fouling layer attached to the film surface.

The boundary layer thickness δ is irrelevant to the velocity of the film, and δ = (12νt) ^0.5 , where ν is the kinematic viscosity of the fluid and t is the time after the membrane starts to operate. Calculated. As can be seen from this equation, it takes a certain amount of time from when the filtration membrane unit 21 starts to rotate to when a vortex is generated, and a vortex that is effective for removing the fouling layer adhering to the membrane surface is generated. Adjacent separation membrane 2
It is preferable to make the interval of 3, 23 smaller than the diameter of the filtration membrane unit 21.

Further, the above-mentioned vortex flow differs in Taylor vortex generated in the transition region between the laminar flow state and the turbulent flow state from the generation mechanism thereof. In the membrane separation device of the present invention, a vortex flow effective for removing the fouling layer is generated even in a laminar flow state in which Taylor vortices are not generated, which is advantageous in terms of power.
Incidentally, with the structure shown in FIG. 4, Taylor vortices are likely to occur except in the gaps between the facing portions of the filtration membrane unit 21, so that the scraping effect is further enhanced.

FIG. 8 is a graph comparing changes in permeation flux with time when α-amylase produced by Bacillus subtilis fermentation is separated from the fermentation broth using the membrane separator of the present invention and the conventional membrane separator. .. The Bacillus subtilis used here is an α-amylase-producing thermophilic bacterium, and its strain name is Bacillis caldolyti.
After pre-culturing this bacterium using cus DSM405, in a 20-liter fermentation tank, maltose-casitone medium (casitone; 1 g / liter, maltose; 1 g / liter, K
H ₂ PO ₄ ; 0.05 g / liter, Cacl ₂ · 2H ₂ O;
1 g / _{l, MgSO 4 · 7H 2 O;} 0.25g / l, Mncl _2; 0.001g / l, FeSO ₄ · 7H ₂
O; 0.03 g / liter) was used for batch culture. The culture temperature was 60 ° C. and the culture time was 8 hours. As a result, the bacterial cell concentration at the end of the batch fermentation was 13,000 mg / l, the viable cell count was 2.4 × 10 ⁸ cells / ml, the activity of α-amylase was 500 U / l, and the viscosity of the fermentation solution was 1.8 cp. A fermented liquid was prepared. Then, the operating conditions and the like of the present invention and the conventional devices for separating α-amylase from this fermentation broth are as follows.

(Invention apparatus) First, steam of 121 ° C. or higher is fed from the inflow port 16 of the empty hermetically sealed container 11 to 20
After the sterilization was performed by maintaining the temperature at 121 ° C. for at least a minute, hot water was supplied from the hot water inlet 14 to control the inside of the closed container 11 at 60 ° C. in order to prevent the inactivation of α-amylase. Then, after the temperature was controlled at 60 ° C., the fermentation liquid was pressure-fed by the compressor 2 through the inflow port 16. The pressure of the compressor was such that the pressure in the closed container 11 was 0.5 kg / cm ² . The fermentation liquor decreased with the progress of filtration was replenished with the fermentation liquor in the tank 1 by pressure feeding, and the vacuum pump 8 did not reduce the pressure. Further, the two filtration membrane units 21 are arranged at an interval of 1 mm, each filtration membrane unit 21 is rotated in the same direction at 637 rpm, and the membrane surface velocity is 1.00 m.
/ S. The cylindrical separation membrane 23 is made of high-purity alumina, and a porous layer having a pore diameter of 0.1 μm is formed on a support layer having a pore diameter of 10 to 100 μm, and an outer diameter of 30 mm,
A microfiltration membrane having an inner diameter of 26 mm and a length of 500 mm was used in which the total membrane area of ^two filtration membrane units was 0.094 m ² .

(Conventional device: Cylindrical membrane) As shown in FIG. 9 (a), the overall structure of the system is such that the membrane modules 100 are vertically connected in series and the tubular separation used in the present invention is provided in the membrane module 100. Set the same cylindrical separation membrane as the membrane 23,
The membrane surface velocity was 1.00 m / s, and the transmembrane pressure difference was 0.5 kg / cm ² only by pressurization by a pump. In FIG. 9, the same parts as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

(Conventional device: rotary flat membrane) As shown in FIG. 9B, the entire structure of the system is separated by using a membrane module in which a rotary flat membrane 102 rotated by a motor 101 is placed in a closed container. To do. The closed container has a capacity of 2.1 liters, the separation membrane is made of high-purity alumina, and a porous layer of 0.1 μm is formed on a support layer having a pore diameter of 10 to 100 μm. 260m
m, inner diameter 89 mm disc, total membrane area 0.094 m ²
The rotation speed of the membrane was 109 rpm, the surface velocity of the membrane at the position of the average radius of the rotating flat membrane was 1.00 m / s, and the pressure difference between the membranes was 0.5 kg / cm ² with the compressor.

In the above experiment, the activity of α-amylase in the permeate 4 hours after the start of filtration was 500 U / l in all of the three types of membrane separators, which was the same as the initial activity. The number is 2.4 in the conventional device using the cylindrical membrane.
× 10 ⁸ pieces / ml to 1.4 × 10 ⁸ pieces / ml (58%)
In addition, in the conventional device using the rotating flat membrane, 1.9 × 10 ⁸ pieces /
While it was reduced to ml (79%), in the present invention, 2.
It was only reduced to 2 × 10 ⁸ cells / ml (92%). It is considered that this is because the circulating pump is not required in the present invention and the shear stress acting on the liquid to be treated is constant. As described above, in the present invention, since cross-flow filtration can be performed without using a circulation pump, an example in which a circulation pump is not used is shown in the illustrated example, but continuous operation may be performed using a circulation pump. Of course.

[0023]

As is apparent from the above description and the experimental results shown in FIG. 8, according to the present invention, the filtration membrane units arranged in the closed container are arranged in parallel with each other and in the same direction. Since it is composed of a plurality of rotating hollow rotary shafts and a tubular separation membrane attached to the outer peripheral surface of the hollow rotary shafts, vortexes are generated in the gaps of the facing parts that are close to each other, and due to the shear stress of these vortexes. The fouling layer adhering to the surface of the separation membrane is removed, a high membrane permeation flux can be maintained, and the shear stress applied to the liquid to be treated is constant. Can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a filtration system to which a membrane separation device according to the present invention is applied.

FIG. 2 is a sectional view of the membrane separation device.

3 is a sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view similar to FIG. 3, showing another embodiment of the closed container.

FIG. 5 is an enlarged sectional view of a main part of the membrane separation device.

FIG. 6 is a sectional view similar to FIG. 2, showing another embodiment of the membrane separation device with a different drive system.

FIG. 7 is a view showing a vortex flow generated in a gap between adjacent filtration membrane units.

FIG. 8 is a graph showing changes with time of permeation fluxes of the membrane separator of the present invention and the conventional membrane separator.

FIG. 9 is a schematic configuration diagram of a conventional membrane separation device used for comparison with the present invention.

[Explanation of symbols]

1 ... Storage tank, 2 ... Compressor, 5 ..., 6 ..., 7
a, 7b, 7c ... Permeate storage tank, 10 ... Membrane separation device, 11 ... Airtight container, 11a ... Swelling portion, 11b constricted portion,
12 ... Outer case, 13 ... Inner case, 14 ... Warm water inlet, 15 ... Warm water outlet, 16 ... Treatment liquid inlet, 17
... Concentrated liquid outlet, 21 ... Filtration membrane unit, 22 ... Hollow rotating shaft, 23 ... Cylindrical separation membrane, 25 ... Hollow part.

Claims (2)

[Claims] 1. A membrane separation device comprising a filtration membrane unit (21) provided in a closed container (11) having an inlet (16) for a liquid to be treated and an outlet (17) for a concentrated liquid. The unit (21) includes a plurality of hollow rotating shafts (22) each having a hollow portion (25) arranged in parallel with each other,
The hollow rotary shaft (22) is composed of a tubular separation membrane (23) mounted on the outer peripheral surface thereof, and the hollow rotary shafts (22) have the same rotation direction and pass through the tubular separation membrane (23). A membrane separation device, characterized in that a communication hole (26) for guiding the permeated liquid to the hollow portion (25) is formed. 2. The closed container (11) comprises a bulging portion (11a) for accommodating an individual filtration membrane unit (21) and a constricting portion (1).
The membrane separation device according to claim 1, wherein the membrane separation device has a continuous shape in 1b).