JP2002153736A - Cleaning method of membrane module and membrane separation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method of a membrane module, which can recover the treatment efficiency of the membrane module. SOLUTION: This cleaning method is a method for cleaning a membrane module 3a which obtains a concentrate and a permeate from a liquid to be treated by the cross flow membrane separation of the liquid to be treated. The cleaning method comprises a cleaning liquid supply process for supplying a cleaning liquid to the permeate side 3b of the membrane module 3 so that pressure exceeds the internal pressure of the side 3a of the liquid to be treated, and a flow velocity fluctuation process for fluctuating the flow velocity of the liquid to be treated in the membrane module 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a membrane module and a membrane separation apparatus, and more particularly to a method for removing sulfur from a saccharified solution.
The present invention relates to a washing method and a membrane separation device which can be suitably applied to a membrane module used for membrane filtration in a pharmaceutical or food manufacturing process, such as S separation, separation of bacterial cells from a fermented solution, and finish filtration of sake, beer, and wine. More specifically, the present invention relates to a membrane module cleaning method and a membrane separation device capable of obtaining a sufficient cleaning effect.

[0002]

2. Description of the Related Art When performing a membrane separation treatment using a membrane module, if the treatment is performed for a long time, the liquid to be treated is concentrated, and solids adhere to the separation membrane surface on the liquid to be treated side, The permeation flux of the membrane module is reduced and the separation performance is reduced. For this reason, for the purpose of recovering the membrane separation performance, backwashing is performed in which a permeated liquid or compressed air is permeated through the separation membrane from the permeated liquid side to the liquid to be treated side.

[0003]

In particular, in the case of performing membrane separation of a liquid to be treated having a high concentration of a suspended substance such as a saccharified liquid or a fermentation liquid in a pharmaceutical or food production process, a high permeation flux is set. When the load operation is performed, the suspended substance is easily deposited on the film surface, and the suspended substance tends to be in a compact state. In such a case, the conventional cleaning method described above tends to have an insufficient cleaning effect, and cannot sufficiently recover the processing efficiency of the membrane module. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cleaning method capable of sufficiently recovering the processing efficiency of a membrane module.

[0004]

The method for cleaning a membrane module according to the present invention is a method for cleaning a membrane module in which a liquid to be treated is subjected to membrane separation by a cross-flow method to obtain a concentrated solution and a permeate. On the permeate side of the module, there is provided a cleaning liquid supply step of supplying a cleaning liquid so as to have a pressure exceeding the internal pressure of the liquid to be treated, and a flow rate changing step of varying the flow rate of the liquid to be treated in the membrane module. I do. As the washing liquid, it is preferable to use the above-mentioned permeate. The membrane separation device of the present invention is a membrane module for obtaining a concentrated solution and a permeate by subjecting a liquid to be treated to membrane separation by a cross flow method, a cleaning solution supply path for supplying a cleaning solution to a permeate side of the membrane module, It is characterized by comprising pressure means for increasing the pressure of the cleaning liquid supplied through the passage, and flow rate changing means for changing the flow rate of the liquid to be treated in the membrane module.

[0005]

FIG. 1 shows an embodiment of a membrane separation apparatus according to the present invention. The membrane separation apparatus 1 shown here comprises a liquid storage tank 2 for storing a liquid to be processed and a storage tank 2 for storing the liquid. A membrane module 3 for subjecting the liquid to be treated from the tank 2 to a membrane separation treatment. The membrane separation apparatus 1 includes a processing liquid supply path 4 for supplying a processing liquid to a processing liquid side 3a of the membrane module 3 and a processing liquid for returning the processing liquid in the processing liquid side 3a to the storage tank 2. A liquid return path 5, a permeated liquid lead-out path 6 for drawing out the permeated liquid from the permeated liquid side 3b, a permeated liquid introduction path 7 which is a cleaning liquid supply path for introducing the permeated liquid to the permeated liquid side 3b as a cleaning liquid, and this introduction path 7, a pressurizing pump P2 which is a pressurizing means for increasing the pressure of the permeated liquid, and a bypass path 8 for increasing the flow rate of the liquid to be treated in the return path 5. Code V1
To V6 indicate valves provided in each path. Code P1
Denotes a liquid feed pump provided in the liquid supply path 4 to be processed.

The membrane module 3 is provided with a separation membrane 3d in an outer container 3c. As the separation membrane 3d, a material composed of an organic material (eg, cellulose acetate, polyamide, polysulfone, polypropylene, polyfluorinated ethylene, polyvinylidene fluoride, polycarbonate) or an inorganic material (eg, metal, ceramic) can be used. . Among them, it is particularly preferable to use a membrane made of an inorganic material since a decrease in separation performance can be prevented even when operation is performed at a high pressure or when a chemical solution is frequently washed with an alkali or an acid. In particular, it is preferable to use titanium-coated stainless steel in which the stainless steel surface is coated with titanium because the separation membrane is hardly damaged even when a sudden pressure fluctuation occurs.

The shape of the separation membrane 3d may be tubular, hollow fiber, pleated, spiral, plate and frame, or the like. In particular, the tubular membrane is preferable because even if it is applied to a liquid to be treated containing a large amount of solid content, the separation performance hardly decreases and the pressure resistance is excellent.

[0008] The bypass passage 8 serves as a flow rate variation means, and is connected upstream and downstream with respect to the valve V6 provided in the return passage 5. In the return passage 5, the liquid to be treated on the upstream side of the valve V6 is passed. , And can flow downstream of the valve V6 without passing through the valve V6. A multi-stage turbine pump can be used as the liquid sending pump P1. It is preferable to use a plunger pump as the pressurizing pump P2 in order to obtain a high head. In the apparatus shown here, the pressurizing pump P2 was used as the pressurizing means, but a separate sealed permeate storage tank (not shown) was provided separately.
The storage tank may be configured to be pressurized by a compressor or the like so that the permeated liquid can be supplied to the membrane module 3.

Next, a method for performing a membrane separation process on a liquid to be treated by using the membrane separation apparatus 1 will be described. In the present invention, examples of the treatment target (liquid to be treated) of the membrane module include pharmaceutical products, saccharified liquids, fermented liquids, and intermediate products of beverages (sake, beer, wine, etc.) in a food production process. These liquids to be treated usually contain solids composed of proteins, sugars, microorganisms and the like.

In order to carry out the membrane separation treatment of the liquid to be treated, the liquid to be treated in the liquid to be treated storage tank 2 is passed through the liquid to be treated supply path 4 using the pump P1 and the liquid to be treated 3a of the membrane module 3 is treated.
To be introduced. In this membrane separation process, a filtration process is performed by a cross-flow method in which the liquid to be treated flows parallel to the surface of the separation membrane 3d. Part of the liquid to be treated permeates through the separation membrane 3d, and as a permeate, the permeate side 3b, the permeate outlet path 6
The remaining part is returned to the processing liquid storage tank 2 through the processing liquid return path 5 as a concentrated liquid, and is circulated by repeating this process. At this time, the valve V
4, V6 is open and valves V1, V2, V3, V5 are closed. The permeated liquid derived from the passage 6 is preferably stored in a permeated liquid storage tank (not shown). At this time, the pressure of the liquid to be treated in the liquid to be treated 3a is preferably set to a value exceeding the normal pressure by appropriately setting the opening of the valve V6 provided in the return path 5.

When the above-mentioned membrane separation treatment is performed for a long time, the liquid to be treated is concentrated, and the solid content in the liquid to be treated adheres to the surface of the liquid to be treated 3a of the separation membrane 3d. The permeation flux of Therefore, the separation membrane 3d is cleaned by the cleaning method described below. This washing can be performed when the permeation flow rate becomes equal to or less than a predetermined value in the membrane separation process (in the case of constant pressure filtration). Further, it can be performed when the internal pressure of the liquid to be treated 3a becomes a predetermined value or more (in the case of constant flow rate filtration).

An embodiment of the method for cleaning a membrane module according to the present invention will be described below, taking the case where the above-mentioned membrane separation apparatus 1 is used as an example. The cleaning method of this embodiment has the following two steps.

(1) Cleaning Liquid Supplying Step (First Step) While the opening degree of the valve V6 is maintained, the liquid to be treated is circulated through the paths 4, 5 and the membrane module 3 using the pump P1, and the valve V4 is supplied. Is closed, the valve V3 is opened, and the pressurizing pump P2 is driven to supply the permeate drawn out of the system in the membrane separation process to the permeate side 3b as a cleaning solution through the passages 7 and 6. In this step, the pressure of the permeated liquid in the permeated liquid side 3b increases
The permeate is supplied so as to exceed the pressure of the liquid to be treated in a.

In this cleaning liquid supply step, the cleaning liquid is transferred from the permeate liquid side 3b (high pressure side) to the liquid side 3a (low pressure side).
Therefore, the separation membrane 3d is back-flow-cleaned, and the deposits on the membrane surface and in the pores can be peeled off or in a state where they can be easily peeled off.

(2) Flow Velocity Fluctuation Step (Second Step) The valve V2 provided in the bypass path 8 is opened, and the liquid to be treated upstream of the valve V6 in the return path 5 is caused to flow downstream of the valve V6. And the flow rate of the liquid to be circulated through the passages 4 and 5 is increased. Thereby, the flow rate of the liquid to be treated in the membrane module 3 is increased. In this cleaning method, in the above-mentioned cleaning liquid supply step (first step), not only a force from the permeate liquid side 3b to the liquid to be treated side 3a is applied to the deposit by the cleaning liquid, but also a flow velocity fluctuation step (second step). A shearing force can be applied to the deposit from the liquid side 3a by the liquid to be treated. For this reason, a force can be applied to the attached matter from two different directions to facilitate separation from the separation membrane 3d. In this flow rate changing step, the valve V2 can be opened and closed or the opening degree adjusted as needed, and the flow rate of the liquid to be treated can be changed a plurality of times to enhance the adhered matter peeling effect.

The flow rate changing step may be performed after the cleaning liquid supply step is performed, or may be performed while the cleaning liquid supply step is performed. When the cleaning liquid supply step and the flow rate fluctuation step are performed simultaneously, a force is applied to the adhered substance from the permeate liquid side 3b toward the liquid to be treated 3a, and
From a, a shearing force in a direction parallel to the film surface can be applied. For this reason, a force is simultaneously applied to the adhered substance from two directions, so that the adhered substance can be easily separated from the separation membrane 3d. Further, the washing including these two steps can be performed a plurality of times as necessary.

After the cleaning consisting of the above two steps is completed, the valve V2 is closed and the valve V4 is opened to restart the membrane separation process.

According to the method for cleaning a membrane module of the present embodiment, the following effects can be obtained. 1) In the cleaning liquid supply step, the cleaning liquid is supplied to the permeated liquid side 3b of the membrane module 3 at a pressure exceeding the internal pressure of the liquid to be treated 3a.
a, the separation membrane 3d is back-flow-cleaned, and the deposits on the membrane surface and in the membrane pores can be peeled off or can be easily peeled off. For this reason, the permeation flux of the separation membrane 3d at the time of restarting the membrane separation process can be increased. 2) In the flow rate changing step, the flow rate of the liquid to be treated in the membrane module 3 is changed, so that the liquid to be treated applies a shearing force to the deposit on the separation membrane 3d, thereby facilitating the detachment of the deposit. For this reason, the permeation flux of the separation membrane 3d at the time of restarting the membrane separation processing can be further increased. From the above 1) and 2), the effect of removing the deposits on the separation membrane 3d can be improved, and the processing efficiency of the membrane module 3 can be sufficiently recovered even when the concentration of the suspended substance in the liquid to be processed is high. Further, since a sufficient cleaning effect can be obtained in a short time, the time required for cleaning can be reduced, and the production efficiency can be improved.

Further, since a permeate is used as the cleaning liquid,
There is no need to prepare a separate cleaning liquid, and the cleaning cost can be kept low.

In the flow rate changing step, the flow rate of the liquid to be treated is changed by increasing or decreasing the return flow rate of the liquid to be treated by using the bypass path 8, so that the liquid to be treated can be changed without changing the opening of the valve V6. To maximize the return flow of
A high liquid flow rate can be obtained. Therefore, an excellent cleaning effect can be obtained. A valve V6 used for adjusting the internal pressure of the liquid to be treated 3a during the membrane separation process.
It is not necessary to perform the above operation, so that the operation for restarting the membrane separation process after the completion of the washing becomes easy. In the present embodiment, the permeating liquid is used as the cleaning liquid. However, the present invention is not limited to this, and water or the like can be used as the cleaning liquid.

In the cleaning method of the above embodiment, in the flow rate changing step, a method of changing the flow rate of the liquid to be processed by increasing or decreasing the return flow rate of the liquid to be processed by using the bypass path 8 is adopted. However, the present invention is not limited to this, and the flow rate of the liquid to be treated can be changed by the following method. i) By opening the valve V1 provided in the short-circuit path 10 connecting the supply path 4 and the return path 5, the supply path 4
A part of the liquid to be treated can be returned to the liquid to be treated storage tank 2 through the short circuit path 10 without passing through the membrane module 3. Therefore, by opening and closing the valve V1, the flow rate of the liquid to be treated flowing into the membrane module 3 can be increased or decreased, and the flow rate of the liquid to be treated in the membrane module 3 can be changed. In this case, the short-circuit path 10 corresponds to a flow speed changing unit. When this method is adopted, the flow rate of the liquid to be treated can be changed by a simple valve operation, so that the operation becomes easy. ii) The flow rate of the liquid to be processed flowing in the return path 5 is increased or decreased by opening and closing or adjusting the opening degree of the valve V6 provided in the return path 5 to change the flow rate of the liquid to be processed in the membrane module 3. In this case, the valve V6 corresponds to a flow speed changing unit. When this method is adopted, it is not necessary to newly provide a valve or a path, so that the apparatus configuration can be simplified and the equipment cost can be reduced. iii) A valve (not shown) as a flow rate variation means in the supply path 4
The flow rate of the liquid to be processed flowing in the supply path 4 is increased or decreased by changing the opening / closing or opening degree of the valve, and the flow rate of the liquid to be processed in the membrane module 3 is changed. When this method is adopted, the flow rate of the liquid to be treated can be changed by a simple valve operation, so that the operation becomes easy. iv) The flow rate of the liquid to be processed supplied from the supply path 4 is increased / decreased by driving / stopping control or driving force adjustment of the liquid feed pump P1 to change the flow rate of the liquid to be processed in the membrane module 3. In this case, the liquid sending pump P1 corresponds to a flow rate changing unit. When this method is adopted, it is not necessary to newly provide a valve or a path, so that the apparatus configuration can be simplified and the equipment cost can be reduced. v) A pressurized air supply path (not shown) serving as pressurized air supply means may be connected to the supply path 4 to supply the pressurized air to the membrane module 3 while adjusting the supply amount. By supplying the pressurized air, a mixed fluid of the pressurized air and the liquid to be processed is supplied to the liquid to be processed 3a, and the flow rate of the liquid to be processed flowing in the liquid to be processed 3a can be set high. By appropriately setting the supply amount of the pressurized air, the liquid to be treated 3a
The flow rate of the liquid to be processed flowing through the inside can be changed.
In this case, the pressurized air supply path corresponds to the flow velocity changing unit. When this method is employed, the shearing force of the separation membrane 3d on the deposits is increased by the pressurized air, and an excellent effect of removing the deposits can be obtained.

[0022]

The effects of the present invention will be clarified below with reference to specific examples. Example 1 SS separation of a saccharified solution was performed using the membrane separation device 1 shown in FIG. As the separation membrane 3 d of the membrane module 3, a stainless steel membrane (inner diameter: 19 mm, length: 3000 mm, four cylindrical membranes, total membrane area: 0.7 m ² , pore diameter: 0.1 μm) was used. Storage tank 2
500 L of a saccharified solution (dry SS concentration 0.5%) is placed in the inside, and the saccharified solution is circulated as a liquid to be treated via a path 4, a membrane module 3, and a path 5 using a pump P <b> 1 while a cross-flow system is used. A membrane separation treatment was performed (flow rate 270 L /
min). In this process, the valves V1, V2, V3, V
5 was closed and the valve V4 was opened. The opening of the valve V6 is
It was set so that a pressure of 1 MPa was applied to the liquid side 3a to be treated.

When the permeation flux decreased from 400 L / m ² / Hr (at the start of the treatment) to 300 L / m ² / Hr, the following washing was performed. The valve V4 was closed, the pressure pump P2 was operated, and the valve V3 was opened, so that the permeate was supplied to the permeate side 3b through the paths 7 and 6 (washing liquid supply step). When the internal pressure on the permeate side 3b reached 3 MPa, the valve V2 was opened to guide the liquid to be processed into the bypass path 8, the valve V3 was closed, and the pump P2 was stopped (flow velocity variation step). Next, the valve V4 was opened and the valve V2 was closed to restart the membrane separation process. The time required from the start of the washing to the restart of the membrane separation treatment was about 10 seconds. The above membrane separation treatment and washing were repeated a plurality of times.
FIG. 2 shows the change over time of the permeation flux during that time. The point at which washing (backwashing) was performed is indicated by an arrow.

Comparative Example 1 A saccharified solution was subjected to membrane separation in the same manner as in Example 1, and the permeation flux was 400 L / m ² / Hr.
The following cleaning was performed at the time when the temperature was lowered from (at the start of the treatment) to 300 L / m ² / Hr. Close the valve V4, operate the pressurizing pump P2 and open the valve V3,
The permeate was supplied to the permeate side 3b through the passages 7 and 6.
When the internal pressure on the permeate side 3b reached 3 MPa, the valve V3 was closed and the pressure pump P2 was stopped. Next, the valve V4 was opened to restart the membrane separation process. The time required from the start of the washing to the restart of the membrane separation treatment was about 10 seconds. The above membrane separation treatment and washing were repeated a plurality of times. FIG. 2 also shows the temporal change of the permeation flux during that time. The point at which washing (backwashing) was performed is indicated by an arrow.

FIG. 2 shows that the recovery rate of the permeation flux when restarting the membrane separation process after cleaning is higher in Example 1 than in Comparative Example 1.

[0026]

As described above, the following effects can be obtained by the method for cleaning a membrane module of the present invention. 1) In the cleaning liquid supply step, the cleaning liquid is supplied to the permeated liquid side of the membrane module at a pressure exceeding the internal pressure of the liquid to be treated, so that the cleaning liquid flows from the permeated liquid side to the liquid to be treated to backwash the separation membrane. The deposits on the membrane surface and in the membrane pores can be peeled off or can be easily peeled off. For this reason, the permeation flux at the time of restarting the membrane separation process can be increased. 2) In the flow rate changing step, since the flow rate of the liquid to be treated in the membrane module is changed, a shearing force is applied to the deposit on the separation membrane, and the detachment of the deposit can be promoted. For this reason, the permeation flux of the separation membrane at the time of restarting the membrane separation processing can be further increased. According to the above 1) and 2), it is possible to improve the adhered substance peeling effect and sufficiently recover the processing efficiency of the membrane module even when the suspended substance concentration in the liquid to be treated is high. Further, since a sufficient cleaning effect can be obtained in a short time, the time required for cleaning can be reduced, and the production efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a membrane separation apparatus suitable for carrying out one embodiment of a membrane module cleaning method of the present invention.

FIG. 2 is a graph showing test results. The horizontal axis indicates time, and the vertical axis indicates permeation flux.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Membrane separation apparatus, 2 ... Treatment liquid storage tank, 3 ... Membrane module, 3a ... Treatment liquid side, 3b ... Permeate liquid side, 7 ...
Permeate introduction path (cleaning liquid supply path), 8: bypass path (flow rate changing means), P2 ... pressurizing pump (pressurizing means)

Claims (3)

[Claims] 1. A method for washing a membrane module (3) for subjecting a liquid to be treated to membrane separation by a cross-flow method to obtain a concentrated solution and a permeate, wherein a permeate solution side (3b) of the membrane module is provided. Cleaning of a membrane module, comprising: a cleaning liquid supply step of supplying a cleaning liquid so as to have a pressure exceeding the internal pressure of the processing liquid (3a); and a flow rate changing step of changing a flow rate of the liquid to be processed in the membrane module. Method. 2. The method for cleaning a membrane module according to claim 1, wherein the permeate is used as a cleaning liquid. 3. A membrane module (3) for obtaining a concentrated liquid and a permeate by subjecting a liquid to be treated to membrane separation by a cross flow method, and a cleaning liquid supply path for supplying a cleaning liquid to a permeate side (3b) of the membrane module. (7), a pressurizing means (P2) for increasing the pressure of the cleaning liquid supplied through the path, and a flow rate varying means (8) for varying the flow rate of the liquid to be treated in the membrane module. Membrane separation device (1).