JP3951549B2 - Cylindrical membrane element and cleaning method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical membrane element and a cleaning method thereof, and is particularly suitable for concentration or solid-liquid separation of high-concentration slurry-like liquid such as manure sludge, sewage sludge, industrial waste sludge, or fermented cells or pulp slurry. The present invention relates to a cylindrical membrane element and a method for cleaning the cylindrical membrane element.
[0002]
[Prior art]
Membrane filtration is generally used for waste processing such as sewage sludge, sewage sludge, industrial waste sludge, etc. and separation processes for fermented cells in industrial fields such as food and pharmaceuticals, because the device is small and has excellent workability. A lot of equipment is used.
[0003]
However, when a high-concentration slurry liquid as described above is membrane filtered, the suspension in the slurry adheres to and accumulates on the membrane surface of the primary side (raw water, that is, the water to be filtered) in a normal membrane, and the filtration performance over time Will fall.
[0004]
Conventionally, a method of generating turbulent flow on the surface on the primary side of the membrane has been adopted in order to prevent the membrane filtration performance from being deteriorated due to such adhesion and deposition of the suspension. For example, in the hollow fiber membrane, a method of circulating the slurry at high speed in the hollow fiber, or a method of circulating the slurry in the flat membrane so that turbulent flow is generated on the membrane surface is adopted.
[0005]
[Problems to be solved by the invention]
However, such a method of generating turbulent flow on the membrane surface has the disadvantage that the energy consumption for circulating the slurry is large and the equipment becomes complicated.
[0006]
The present invention solves the above-mentioned conventional problems, a membrane performance which can be easily recovered by washing, and is suitable for membrane filtration of high-concentration slurry liquid, and a method for washing the cylindrical membrane element. The purpose is to provide.
[0007]
[Means for Solving the Problems]
The cylindrical membrane element of the present invention includes a cylindrical membrane and a plurality of rod-like membrane support members provided inside and outside the cylindrical membrane in a direction parallel to the axial center line of the cylindrical membrane. 6 to 24 membrane support members are arranged on substantially the same circumference as the cylindrical membrane, and the membrane support members are first membranes arranged outside the cylindrical membrane. It comprises a support member and a second membrane support member arranged inside the cylindrical membrane, and the first membrane support member and the second membrane support member are alternately arranged in the circumferential direction. It is characterized by.
[0008]
The method for cleaning a cylindrical membrane element according to the present invention is a method for cleaning such a cylindrical membrane element according to the present invention, and is a pressurized gas from the secondary side of the cylindrical membrane, that is, the filtered water (permeate) side. And / or supplying a liquid.
[0009]
In the cylindrical membrane element of the present invention, the cylindrical membrane is supported by the membrane support member, and swings in the centrifugal direction during membrane filtration and in the centripetal direction during washing (back washing), thereby depositing on the membrane surface Can be easily peeled and removed. For this reason, it is possible to easily restore the membrane performance only by periodically performing cleaning for supplying pressurized gas and / or liquid from the secondary side of the cylindrical membrane (hereinafter sometimes referred to as “back washing”). be able to.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a cross-sectional view showing an embodiment of a cylindrical membrane element of the present invention. FIG. 1 (a) shows a state during membrane filtration, and FIG. 1 (b) shows a state during backwashing. FIG. 2 is a view showing an embodiment of the cylindrical membrane of the cylindrical membrane element of the present invention, where (a) is a perspective view before winding, and (b) is after winding. It is sectional drawing shown. FIG. 3 is a system diagram illustrating an embodiment of a membrane filtration step and a washing step of the cylindrical membrane element of the present invention.
[0012]
1A and 1B includes a cylindrical membrane 2 and a plurality of cylindrical membranes 2 provided inside and outside the cylindrical membrane 2 in a direction parallel to the axis of the cylindrical membrane 2 (FIG. 1). (A) and (b) are composed of eight rod-shaped membrane support members 3 (3A to 3H). As shown in the figure, the membrane support members 3 are arranged at substantially equal intervals on the same circumference. The cylindrical membrane 2 is zigzag so that the membrane support members 3A to 3H are alternately positioned inside and outside, that is, the membrane support member (second membrane support) among the eight membrane support members 3A to 3H. Members) 3A, 3C, 3E, 3G are positioned on the inner peripheral side of the cylindrical membrane 2, and the membrane support members (first membrane support members) 3B, 3D, 3F, 3H are positioned on the outer peripheral side of the cylindrical membrane 2. Is arranged.
[0013]
The number of the membrane supporting member 3, it is not preferable in this manner is even present for placement every other inside and outside of the cylindrical film 2. Further, during membrane filtration and backwashing of the cylindrical membrane 2, the cylindrical membrane 2 is kept in a good shape, and deposits due to oscillation of the cylindrical membrane 2 during membrane filtration and backwashing described later are also maintained. In order to obtain a sufficient peeling effect, the number of membrane support members 3 is 6 to 24 . The diameter of the membrane support member 3 is preferably about 5 to 20 mm.
[0014]
On the other hand, if the inner diameter of the cylindrical membrane 2 is excessively small, the fluidity of slurry such as sludge that circulates in the membrane is poor and there is a risk of blockage of the flow path. Therefore, it may be 25 mm or more, particularly 32 mm or more. preferable. Although there is no restriction | limiting in particular about the upper limit of the internal diameter of the cylindrical film | membrane 2, From the surface of handleability etc., generally it shall be 200 mm or less.
[0015]
The membrane material of the cylindrical membrane 2 may be any material as long as it is applied to a normal membrane filtration element, and any membrane material can be applied. From the viewpoint of physical strength that can be sufficiently secured, fluororesins such as polytetrafluoroethylene, polysulfone, and the like are preferable, and polytetrafluoroethylene is particularly optimal.
[0016]
In the case of the cylindrical membrane element 1 composed of the cylindrical membrane 2 and the membrane support member 3, as shown in FIG. 1 (a), at the time of membrane filtration, the cylindrical membrane 2 serving as the primary side of the membrane The cylindrical membrane 2 is separated from the inner membrane support members 3A, 3C, 3E, and 3G and supported by the outer membrane support members 3B, 3D, 3F, and 3H by the internal pressure of the liquid that filters the membrane from the inside. In this state, it expands in the centrifugal direction. At the time of backwashing in which pressurized air and / or liquid is supplied from the outer peripheral side of the cylindrical membrane 2 as the secondary side of the cylindrical membrane 2, the pressure of the backwashing fluid is used as shown in FIG. The cylindrical membrane 2 is separated from the outer peripheral membrane support members 3B, 3D, 3F, and 3H and contracts in the centripetal direction while being supported by the inner peripheral membrane support members 3A, 3C, 3E, and 3G. . Therefore, in the back washing process of the membrane, the pressure of the back washing fluid is received, and the cylindrical membrane 2 swings greatly during back washing as compared with the membrane filtration, so that the primary side of the cylindrical membrane 2 is moved. The deposit on the surface, that is, the inner peripheral surface of the cylindrical film 2 is easily peeled and removed.
[0017]
By the way, the cylindrical membrane 2 is required to be a porous membrane having a pore size smaller than the particle size of the suspended substance in the slurry in order to separate the suspended substance in the slurry to be subjected to membrane filtration treatment. . At the same time, the cylindrical membrane 2 is required to have a physical strength that can sufficiently withstand fluctuations during membrane filtration and backwashing as shown in FIGS. 1 (a) and 1 (b).
[0018]
Therefore, in order to combine such a pore diameter and durability against membrane oscillation, the cylindrical membrane 2 according to the present invention preferably has a multilayer structure as shown in FIG.
[0019]
A cylindrical membrane 2 shown in FIG. 2 (b) is obtained by forming a large-diameter support membrane layer 2B as a reinforcing layer on the outer periphery of a pore thin film layer 2A responsible for membrane filtration.
[0020]
The pore thin film layer 2A preferably has a pore diameter of about 0.01 to 1 μm and a thickness of about 10 to 50 μm from the viewpoint of membrane filtration.
[0021]
The large pore diameter supporting membrane layer 2B preferably has a pore size of 1 to 10 μm and a thickness of 500 to 5000 μm in order to ensure the strength of the cylindrical membrane 2.
[0022]
As shown in FIG. 2 (a), the cylindrical membrane 2 having such a multilayer structure is formed by laminating a porous thin film 2a on one end side of a large pore diameter supporting membrane 2b and winding it in the direction of the arrow from the laminated end side. Can be easily manufactured.
[0023]
Both the thin pore film 2a and the large pore diameter supporting membrane 2b are preferably made of a fluororesin, a polysulfone, a polyvinyl alcohol, or the like, and particularly made of polytetrafluoroethylene.
[0024]
Such a cylindrical membrane element of the present invention can perform membrane filtration with the inner side of the cylindrical membrane 2 as the primary side and the outer periphery as the secondary side, and supply pressurized gas and / or liquid from the secondary side. By doing so, the deposit | attachment of the internal peripheral surface of the cylindrical film | membrane 2 can be peeled and removed easily.
[0025]
This backwashing varies depending on the properties of the slurry to be membrane-filtered, etc., but in normal cases, it is 1 to 10 seconds at a frequency of 10 to 300 seconds for membrane filtration, particularly 1 to 30 seconds for membrane filtration. It is preferable to backwash for 2 seconds.
[0026]
Next, with reference to FIG. 3, the operation | movement method of the membrane filtration process and backwashing process by the cylindrical membrane element of this invention is demonstrated.
[0027]
In FIG. 3, reference numeral 10 denotes a membrane module, and the cylindrical membrane element 1 of the present invention is accommodated in the pressure vessel 4. 5 is an air filter, 6 is a water purification filter, and 7 is a liquid level detection sensor.
[0028]
This apparatus introduces the slurry flowing from the slurry introduction pipe 11 into the membrane module 10 and performs membrane filtration treatment.
[0029]
The membrane module 10 has a raw water chamber (primary side) and a filtered water chamber (secondary side) separated by a cylindrical membrane element 1, and the raw water chamber is provided with an introduction port 10a and an outflow port 10b. ing.
[0030]
The filtered water chamber is provided with an inlet port 10c for tap water or pressurized air and an outlet port 10d for filtered water.
[0031]
The slurry introducing pipe 11, inlet valve V ₁ is provided, the drain pipe 12 is branched from between the introduction valve V ₁ and the port 10a of the pipe 11, drain valve V to the drain pipe 12 ₂ is provided.
[0032]
A pipe 13, an exhaust valve V _3, and an exhaust pipe 14 are connected in this order to the slurry outflow port 10 b, and a liquid level detection sensor 7 is provided in the pipe 13.
[0033]
In order to pressurize the slurry in the raw water chamber of the membrane module 10 with air (air), air from the pressurized air source is supplied to the pipe 13 via the pipe 15, the air filter 5, the pipe 16, the air supply valve V ₄ and the pipe 17. It can be introduced.
[0034]
Further, in order to clean the raw water chamber with tap water, tap water can be introduced into the pipe 13 through the pipe 18, the water supply valve V ₅ and the pipe 19.
[0035]
In order to introduce tap water into the filtrate water chamber of the membrane module 10, the pipe 18 communicates with the introduction port 10 c of the filtrate water chamber via the branch pipe 20, the water purification filter 6, the washing water valve V ₆ and the pipe 21. Yes.
[0036]
The pipe 21, the air from the pipe 22 branched from the pipe 16 is capable introduced through the air supply valve V _7.
[0037]
The outlet port 10d of the filtration water chamber is filtered water outlet pipe 23 is connected, takeout valve V ₈ is provided in the pipe 23.
[0038]
Next, the filtration process and the washing and backwashing process by the thus configured filtration device will be described.
[0039]
[Water sampling process]
By opening the introduction valve V ₁ and the exhaust valve V ₃ , a predetermined amount of slurry is introduced into the membrane module 10 from the pipe 11. The exhaust valve V ₃ and the introduction valve V ₁ are opened until the liquid level measurement sensor 7 detects the liquid level, and when the liquid level measurement sensor 7 detects the liquid level, the exhaust valve V ₃ and the introduction valve V ₁ are turned on. close.
[0040]
[Filtering process]
As the take-out valve V ₈ opens, and collecting the filtered water through the cylindrical membrane element 1 of the membrane module 10 from a slurry having solid. In this filtration step, the solid content of the slurry gradually covers the membrane surface, making it difficult for filtered water to come out. Therefore, the open air supply valve _{V 4,} guides the air in the pipe 13 at about 0.1~0.2MPa through the air filter 5. As a result, the slurry in the raw water chamber of the membrane module 10 is pressurized by the air pressure, and the filtered water is taken out from the piping 23.
[0041]
[Washing process 1]
In the filtration step, sufficient filtered water may not be ensured depending on the type of slurry. In that case, close the supply valve V ₄ and the lead valve V _8, applying a counter pressure to the cylindrical membrane element 1 by opening briefly the exhaust valve V ₃ and the air supply valve V _7. Thereby, the solid content adhering to the surface of the cylindrical membrane element 1 on the raw water chamber side is temporarily separated from the membrane surface. And filtered water is taken out by operation similar to a filtration process again.
[0042]
The water sampling step, the filtration step, and the washing step 1 are repeated until a predetermined amount of slurry is processed.
[0043]
[Extrusion process]
After completion of the filtration, the air supply valve V ₄ and the introduction valve V ₁ are opened to push back the slurry remaining in the membrane module 10 and the surrounding piping from the introduction piping 11 by air pressure.
[0044]
[Washing process 2]
In order to clean the inside of the membrane module 10, the water supply valve V ₅ and the drain valve V ₂ are opened to allow cleaning water such as tap water to flow into the raw water chamber of the membrane module 10 through the pipes 18, 19, and 13. The dirt adhering to the inner surface of the membrane element 1 is washed away and drained through the drain valve V ₂ and the drain pipe 12.
[0045]
[Washing process 3]
Since the cleaning step 2 is cleaning of the membrane surface with water, there may be a case where the dirt attached to the surface of the cylindrical membrane element 1 or the membrane cannot be removed. In addition, the following cleaning is performed because dirt accumulates over a long period of time and may interfere with the filtration process.
[0046]
That is, the washing water valve V ₆ and the drain valve V ₂ are opened, and the washing water is introduced into the filtration water chamber of the membrane module 10 through the water purification filter 6 for removing the solid content in the washing water. Wash water is passed from the filtered water side to the raw water side to wash away the solid matter adhering to the inner surface of the cylindrical membrane element 1.
[0047]
This washing the air-supply valve V ₇ is opened, even if the compressed air may also be carried out in a gas-liquid mixture of pressurized air and washing water.
[0048]
In FIG. 1, the cleaning water and pressurized air used for cleaning the membrane module 10, particularly the cleaning water and pressurized air supplied so as to permeate the cylindrical membrane element 1 are both filtered by the cylindrical membrane element 5. Dust removal treatment is performed so as not to contain particles larger than one pore diameter. By removing particles that block the membrane holes of the cylindrical membrane element 1 in this way, contamination by washing water and washing air during washing can be prevented, and effective membrane washing can be performed.
[0049]
In this cleaning step, as shown in FIGS. 1A and 1B, the cylindrical membrane 2 of the cylindrical membrane element 1 swings, so that a good deposit cleaning effect can be obtained.
[0050]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to easily remove and remove the deposits on the membrane surface only by performing periodic backwashing, so that the sludge can be concentrated, separated, and fermented. In a membrane filtration process such as separation of bacterial cells, a membrane filtration treatment of a high-concentration slurry can be stably performed over a long period of time.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a cylindrical membrane element of the present invention, wherein FIG. 1 (a) shows a state during membrane filtration, and FIG. 1 (b) shows a state during backwashing.
2A and 2B are diagrams showing an embodiment of a cylindrical membrane of a cylindrical membrane element of the present invention, wherein FIG. 2A is a perspective view before winding, and FIG. 2B is a cross-sectional view after winding. It is.
FIG. 3 is a system diagram illustrating an embodiment of a membrane filtration step and a washing step of a cylindrical membrane element of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical membrane element 2 Cylindrical membrane 3 Membrane supporting member 2a Porous thin film 2b Large pore diameter supporting membrane 2A Porous thin film layer 2B Large pore diameter supporting membrane layer 4 Pressure vessel 5 Air filter 6 Water purification filter 7 Liquid level detection sensor 10 Membrane module

Claims (4)

A cylindrical membrane element comprising a cylindrical membrane and a plurality of rod-like membrane support members provided inside and outside the cylindrical membrane in a direction parallel to the axial center line of the cylindrical membrane,
6 to 24 membrane support members are arranged on the same circumference as the cylindrical membrane ,
The membrane support member includes a first membrane support member arranged outside the cylindrical membrane and a second membrane support member arranged inside the cylindrical membrane, and the membrane support member in the circumferential direction A cylindrical membrane element , wherein the first membrane support member and the second membrane support member are alternately arranged.   2. The cylindrical membrane element according to claim 1, wherein the cylindrical membrane has an inner diameter of 25 to 200 mm.   In Claim 1 or 2, the cylindrical membrane has a pore thin film layer disposed on the inner peripheral side and a large pore diameter supporting membrane layer disposed on the outer peripheral side, and the pore thin film layer comprises: A cylindrical membrane element having a pore diameter of 0.01 to 1 μm and a thickness of 10 to 50 μm, and the large pore diameter supporting membrane layer having a pore diameter of 1 to 10 μm and a thickness of 500 to 5000 μm.   The method for cleaning a cylindrical membrane element according to any one of claims 1 to 3, wherein pressurized gas and / or liquid is supplied from a secondary side of the cylindrical membrane.

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