JP2009160561A - Filtration module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filtration module which endures use at high temperature and is capable of using broad kinds of cleaning liquids. <P>SOLUTION: The filtration module has a hollow fiber membrane for carrying out the solid-liquid separation of a liquid to be treated containing suspended solids, a supply port which stores the hollow fiber membrane and allows the liquid to be treated to be supplied thereinto, and a discharge port for discharging the filtration residue liquid of the liquid to be treated. The filtration module is provided with a housing configured of an electron beam crosslinked polypropylene or a fiber reinforced polypropylene and a holding part for collecting water which holds one end of the hollow fiber membrane to discharge filtered water in the hollow fiber membrane outside the housing. Preferably, the tensile elastic modulus of the electron beam crosslinked polypropylene or the fiber reinforced polypropylene is not less than 2,200 MPa and is not less than 1,100 MPa at 80°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a filtration module that performs filtration of a liquid to be treated containing a suspended substance using a hollow fiber membrane, and particularly suitable for filtration of water containing an oily substance as a high temperature liquid to be treated and a suspended substance. The present invention relates to a filtration module capable of cleaning a hollow fiber membrane with acid, alkali, organic solvent or the like.

In recent years, as a method for filtering a liquid containing suspended substances such as bacteria, sand, and fine particles, a filtering device using a tube (hollow fiber membrane) made of a porous membrane is being realized.
When the hollow fiber membrane is exposed to a liquid containing a suspended material, the suspended material cannot pass through the hollow fiber membrane, and only the liquid can permeate and flow into the hollow fiber membrane. By utilizing such a solid-liquid separation function of the hollow fiber membrane, highly polluted water such as river water, waste liquid, and industrial waste water can be purified.

  As a filtration module used in a filtration device that purifies highly polluted water, for example, as shown in FIG. 1, a hollow fiber bundle in which a number of hollow fiber membranes 2 that perform solid-liquid separation are concentrated in a cylindrical housing 1. Is attached to the holding member 3 on the bottom surface side of the housing 1 so that one end of the hollow fiber membrane 2 is closed, and the other end of the hollow fiber membrane 2 communicates with the outside of the housing 1. The holding member 4 is inserted. The holding member 3 on the bottom surface side of the housing is provided with a large number of through holes 3 a so that a liquid to be treated containing suspended substances, fine particles and the like can be supplied into the housing 1 from the bottom surface of the housing 1. Yes. The filtered water that has passed through the hollow fiber membrane 2 passes through the holding member 4 on the upper surface of the housing 1 and can be taken from the opening in the upper portion of the housing 1.

  As the hollow fiber membrane, depending on the required filtration performance or the like, generally, as described in paragraph No. 0018 of JP-A-2000-42375 (Patent Document 1), polyethylene (PE), polypropylene (PP) Polyolefin, nylon, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polycarbonate, polyester, polysulfone, cellulose-based, polyvinyl alcohol-based, and polyimide-based hollow fiber membranes are used. Alternatively, as described in paragraph No. 0011 of JP-A-5-96136 (Patent Document 2), polyolefin, polysulfone, polyethersulfone, polyvinyl alcohol, cellulose acetate, polyacrylonitrile and the like can be used.

  The housing is generally composed of a material having mechanical strength and durability as described in paragraph No. 0037 of JP 2000-42375 A (Patent Document 1). For example, polyethylene, polypropylene, polyester, Resin materials such as nylon, PTFE, and PVDF, and metal materials such as stainless steel are used. When an organic solvent is used for the liquid to be treated, polypropylene, PTFE, PVDF, etc. excellent in solvent resistance are preferably used. In paragraph No. 0012 of JP-A-5-96136 (Patent Document 2) and paragraph No. 0018 of JP-A-7-136469 (Patent Document 3), an appropriate material such as metal or plastic is used as a housing material. A preferable material includes acrylic resin, vinyl chloride resin, polysulfone, modified polyphenylene oxide, and polycarbonate resin.

JP 2000-42375 A JP-A-5-96136 JP-A-7-136469

  The constituent material of the housing is also appropriately selected according to the required performance among the above materials, similarly to the material of the hollow fiber membrane. As the required characteristics, first, the material must be corrosion resistant to the liquid to be treated. In addition, when used in purification equipment for industrial wastewater, river water, etc., mechanical strength is also important because a large filtration module with a module height of 1.5 to 2.5 m is often used.

In recent years, the use of filtration devices has further expanded. For example, the use of drain water for boilers operated at high temperatures and the filtration of water used for oil field mining has been studied.
In boiler drain water operated at a high temperature, a liquid of 70 ° C. or higher is supplied to the housing. Therefore, it is necessary to use a housing that can maintain mechanical strength even at high temperatures.

  Also, in the case of filtration modules used outdoors, especially when used in water filtration equipment used for oil extraction in desert areas, the difference in the temperature of the environment where the equipment is installed is large. Strength that can withstand temperature cycling is required. However, in reality, it is difficult to satisfy such requirements with the plastic materials as described above.

  Further, in the filtration module, the filtration residue adheres to the surface of the hollow fiber membrane due to continuous operation, and eventually the pores of the hollow fiber membrane are blocked, resulting in a decrease in filtration performance. In this case, generally, when the filtration performance is lowered, a washing liquid is poured into the filtration device, and the hollow fiber membrane is washed.

  In the case of a liquid to be treated containing an oily substance, it is effective to wash the hollow fiber membrane with an organic solvent such as acetone or methyl ethyl ketone. Therefore, as a hollow fiber membrane, it is a matter of course to use a material resistant to an organic solvent, and it is desirable to use a material that is durable to an organic solvent as a material for the housing. However, when a large amount of organic solvent is supplied for cleaning in a housing made of a plastic material as exemplified in the above-mentioned patent document and exposed for a long time, decomposition of the plastic constituting the housing is promoted. The strength of the housing is lowered and the durability is lowered. Patent Document 1 discloses the use of PP, PTFE, and PVDF that are excellent in organic solvent resistance. However, the above-described large-sized filtration module is not satisfactory in terms of strength. On the other hand, metal materials such as stainless steel have durability against organic solvents. However, in the case of water used at oil field mining sites, inorganic substances such as silica are often attached, and such inorganic substances cannot be removed with an organic solvent. In order to remove inorganic substances, it is efficient to clean with an acid. However, a cleaning operation in which a metal housing is exposed to a large amount of acid for a long time causes corrosion of the metal material.

  Furthermore, in recent years, as a cleaning method, a method has been proposed in which air is supplied into the filtration module to remove contaminants attached to the membrane surface by vibration of the hollow fiber membrane bundle or bubbles. For example, in the above-mentioned Patent Document 2, it is proposed to install a pipe having pores at the center of the hollow fiber membrane bundle and supply cleaning air from the pipe. Alternatively, the liquid to be treated may contain bubbles and be supplied into the housing. In any case, not only the internal pressure due to the supply of the liquid to be treated but also the internal pressure due to the cleaning bubbles is applied to the housing, so that the strength required for the housing becomes even stricter and is satisfied with the above materials. The current situation is that we cannot find anything.

  The present invention has been made in view of such circumstances, and the object of the present invention is to be used at a high temperature in a large-scale filtration device, such as drain water of a high-temperature boiler or treated water at an oil field mining site. Another object of the present invention is to provide a filtration module that can use a wide variety of cleaning liquids so that it can withstand water and can clean oily substances and inorganic substances.

  The inventors of the present invention have reached the present invention by examining the load applied to the housing in the case of supplying the liquid to be processed under various conditions in a large filtration module.

  That is, the filtration module of the present invention includes a hollow fiber membrane that performs solid-liquid separation of a liquid to be treated containing a suspended substance; a supply port that accommodates the hollow fiber membrane and is supplied with the liquid to be treated; A housing made of polypropylene or fiber reinforced polypropylene, which has a discharge port for discharging the liquid filtration residue liquid; and so that the filtered water in the hollow fiber membrane is discharged outside the housing; A water collection holding part for holding one end of the hollow fiber membrane is provided.

  The tensile modulus of elasticity of the electron beam crosslinked polypropylene or fiber reinforced polypropylene is preferably 2200 MPa or more, more preferably 1100 MPa or more at 80 ° C.

  The housing preferably has a thickness of 5 to 10 mm, an outer diameter of 150 to 300 mm, and a length of 1500 to 2500 mm. Moreover, it is preferable that the said hollow fiber membrane is comprised with the porous membrane of the fluororesin.

  The filtration module of the present invention is suitable for filtering water containing an oily substance, or for filtering a liquid to be treated at 70 ° C. or higher.

  The filtration module of the present invention is made of electron beam cross-linked polypropylene or fiber reinforced polypropylene that can withstand acid, alkali, and high temperature, and the housing is constituted. Therefore, depending on the filtration performance and filtration life of the hollow fiber membrane, It can be used for filtration of liquids to be treated and hot water that require washing with alkali.

An embodiment of the filtration module of the present invention will be described with reference to FIG.
In the filtration module shown in FIG. 1, one end of a bundle of hollow fiber membranes in which a number of hollow fiber membranes 2 for solid-liquid separation are concentrated on a water collecting holding member 4 attached to the upper surface of a cylindrical housing 1 The hollow fiber membrane bundle is housed in the housing 1 with the other end of the hollow fiber membrane 2 being attached to the holding member 3 so as to be closed. The holding member 3 on the bottom surface side of the housing 1 is provided with a large number of through holes 3a so that a liquid to be treated containing suspended substances, fine particles and the like can be supplied into the housing 1 from the bottom surface of the housing 1. Yes. The filtered water that has passed through the hollow fiber membrane 2 can be taken from an opening at the top of the housing through the holding member 4 on the top surface of the housing. Further, the liquid to be processed (concentrated liquid) concentrated with the filtration residue is discharged from the discharge port 5 provided on the wall surface above the housing 1.

The filtration module of the present invention is characterized in that the housing is made of electron beam cross-linked polypropylene or fiber reinforced polypropylene.
The size of the housing is not particularly limited, but in order to filter a large amount of liquid to be processed, a filtration device installed outdoors or a filtration module used in a filtration device installed in a factory has a wall thickness of 5 to 10 mm. It is preferable that the diameter is 150 to 300 mm and the total length is 1500 to 2500 mm.

  Cross-linked polypropylene is a polypropylene having a three-dimensional structure that has been cross-linked by irradiation or the like. In general, when radiation or the like is irradiated to polypropylene, the cross-linking reaction and the molecular cleavage reaction proceed with almost the same probability, so it is difficult to improve mechanical properties. However, irradiation with the addition of a polyfunctional monomer is necessary. As a result, a cross-linked polypropylene can be obtained in which the cross-linking reaction preferentially takes place over the molecular cutting reaction and the mechanical properties are improved.

  As the polyfunctional monomer, a monomer having a plurality of double bonds in the molecule such as trimethylolpropane trimethacrylate is preferably used. Such a polyfunctional monomer is preferably mixed at a ratio of 6 to 20 parts by mass with respect to 100 parts by mass of polypropylene.

  As the polypropylene, any of a homopolymer, a random polymer, a block polypropylene and the like can be used, but a random polypropylene is preferable. In general, it seems that random copolymers with many amorphous parts and polypropylene with lower crystallinity are more likely to be crosslinked.

  Moreover, although γ-rays, electron beams (β-rays), X-rays or the like can be used as radiation for crosslinking, γ-rays from cobalt 60 and electron beams from electron beam accelerators are preferable for industrial production. The irradiation amount can be crosslinked if it is several tens of kGy or more, but is preferably 200 kGy or more.

  Such a crosslinked polypropylene can have a tensile elastic modulus of 2200 MPa or higher, and preferably has a tensile elastic modulus of 1100 MPa or higher at 80 ° C. Further, the thermal deformation rate (when a 100 g load is applied to a sample having a thickness of 1 mm at 70 ° C.) can be 1% or less.

  Such a cross-linked polypropylene housing may be cross-linked by forming a housing having a predetermined shape with a polypropyne composition in which a polyfunctional monomer is mixed with polypropyne in a predetermined ratio and then irradiating with radiation.

As the fiber used for the fiber reinforced polypropylene, a known fiber used for a fiber reinforced plastic can be used. Specific examples include glass fiber, carbon fiber, boron fiber, aramid fiber, ceramic fiber, and metal fiber.
Such fibers are preferably contained in an amount of 20 parts by mass per 100 parts by mass of polypropylene.

  The polypropylene composition in which the reinforcing fibers are mixed at the predetermined ratio may be formed into a predetermined shape using an injection molding machine, an extrusion molding machine, or the like. In addition, the predetermined shape may be obtained by heat welding, high frequency welding, ultrasonic welding, or the like.

  Such fiber reinforced polypropylene can have a tensile modulus of elasticity of 2200 MPa or more, and preferably has a tensile modulus of elasticity of 1100 MPa or more at 80 ° C.

  As described above, the mechanical properties of the crosslinked polypropylene and the fiber-reinforced polypropylene are improved without impairing the original chemical properties of polypropyne. Therefore, the housing made of cross-linked polypropylene and fiber reinforced polypropylene has chemical resistance against acids, alkalis and organic solvents. It is possible to maintain the desired strength.

  The housing used in the filtration module of the present invention has a wall thickness of 5 to 10 mm, an outer diameter of 150 to 300 mm, and a cylindrical height of 1500 to 2500 mm, and ensures a pressure resistance of 0.5 MPa even at 80 ° C. It is possible. This is because when the liquid to be processed is supplied from below using the filtration module as shown in FIG. 1 having the above size, the weight of the housing, the weight of the liquid to be processed, the supply pressure of the liquid to be processed Furthermore, it means that it can withstand the internal pressure applied to the lower part of the housing due to bubbles for cleaning.

  The constituent material of the hollow fiber membrane is not particularly limited as long as it is a resin that can form a tube (hollow fiber membrane) composed of a porous membrane. Polyethylene, polypropylene, polysulfone, polyethersulfone, polyacrylonitrile, polytetrafluoro Fluorinated polyolefins such as ethylene (PTFE) and PVDF are used. As the porous membrane constituting the hollow fiber membrane, the membrane may be made into a porous structure by appropriate treatment, or it is a fiber (fibril) structure formed by stretching, and the gap between the fibrils becomes pores. Alternatively, a tube structure may be formed by superposing a porous membrane in a spiral shape. In addition, the porous membrane constituting the hollow fiber membrane may be a single layer or a multi-layer structure in which production methods are appropriately combined.

  The size of the hollow fiber membrane is not particularly limited, but the tube inner diameter of the hollow fiber membrane is 0.3 to 12 mm, the outer diameter is 0.8 to 14 mm, the film thickness is 0.2 to 1 mm, the pore diameter of the porous membrane is 10 nm to 1000 nm, Those having a pressure resistance of a porosity of 50 to 90% and a transmembrane pressure difference of 0.1 to 1.0 MPa are preferably used.

  The constituent material of the hollow fiber membrane may be appropriately selected from the above materials according to the type of the liquid to be treated, but when the liquid to be treated is high-temperature drain water or petroleum mining water, it is composed of a fluororesin. In particular, a porous film of a fluororesin having a fiber structure formed by stretching such as expanded PTFE is preferably used.

  The holding member (water collecting holding member) constituting the upper surface of the housing is molded by curing a liquid resin such as an epoxy resin, an unsaturated polyester resin, or a polyurethane resin, or hot melted such as PFA, PP, or PE resin. A through-hole having an outer diameter of the hollow fiber membrane is formed in the porous plastic material, and the hollow fiber membrane is placed in the hole and can be heat-melted as it is.

  The holding member that constitutes the bottom surface of the housing can be made of the same material as the holding member for collecting water on the upper surface, and is a disk in which a large number of through-holes through which contaminated water can pass is opened, and a recess for holding one end of the hollow fiber membrane Is provided. One end of the hollow fiber membrane may be inserted into the recess and fixed with an adhesive.

  The filtration module having the above configuration is supplied with liquid water to be treated from the bottom surface of the housing. The liquid to be treated supplied into the housing comes into contact with the hollow fiber membrane, and only water or an aqueous solution flows into the hollow fiber membrane. The filtered water flowing into the hollow fiber membrane can be taken outside the housing through the upper fixing member. On the other hand, the liquid whose concentration of suspended matter and oil contained in the liquid to be treated is increased by the filtering action of the hollow fiber membrane is appropriately discharged out of the housing through the discharge port. In this way, the liquid to be treated is filtered by the filtration module.

Here, the oil contained in the liquid to be treated, suspended substances mixed in the liquid to be treated, and the like adhere to the surface of the hollow fiber membrane. If these are left as they are, the filtration performance of the hollow fiber membrane will be lowered, and eventually it will not be able to serve as a filtration device, so it is necessary to periodically wash them. The filtration module of the present invention cannot be easily disassembled due to its size, and cannot be disassembled and cleaned when it is installed in an oil mining site or factory. In this case, normally, instead of the liquid to be treated, a cleaning liquid is supplied into the housing, or a cleaning liquid is supplied into the hollow fiber membrane from the water intake port so that the housing is filled with the cleaning liquid (back washing). Will be washed. When there is a possibility that an organic solvent such as acetone or methyl ethyl ketone or an inorganic substance such as silica is attached to the attached oily substance, it is preferably washed with an acid.
The housing made of cross-linked polypropylene or fiber reinforced polypropyne can maintain the desired mechanical properties even if it is washed with an organic solvent or acid. Therefore, the cleaning liquid can be appropriately selected according to the type of substance attached to the hollow fiber membrane without limiting the cleaning liquid to be used.

  Since the filtration module of the present invention has excellent chemical and mechanical properties as described above, it can withstand harsh use environments, and can be operated for a long time by maintaining the filtration performance.

  Although the liquid to be treated targeted by the present invention is not particularly limited, as described above, it is possible to ensure durability even under conditions where the liquid is exposed to a high temperature of 70 ° C. or higher, and a hollow fiber membrane. It is also possible to use a liquid to be treated that contains suspended substances that require the use of an acid, alkali, or organic solvent for cleaning. Therefore, like boiler drain water, it can be used for filtering contaminated water of 70 ° C. or higher and water used for oil mining. Especially in the case of oil mining water filtration devices such as those installed in desert oil fields, the difference in temperature cycle of the usage environment is large, and not only oily substances but also silica components are mixed in the liquid to be treated. However, it can cope with the filtration of the liquid to be treated, and can withstand long-term operation as a fixed structure.

In the filtration module shown in FIG. 1, the bottom surface is the supply port for the liquid to be treated and the top surface is the intake port for the filtered water. However, the present invention is not limited to this. Although the liquid to be treated is supplied from below and water is taken from above, the filtration module of the present invention is not limited to this, and the liquid to be treated may be supplied from above and taken from below. Alternatively, the housing may be installed horizontally and used.
In the case of a horizontal type or a module that supplies a liquid to be processed from above, the holding member 3 on the liquid supply side to be processed may be fixed to the housing 1.

  Further, in the filtration module shown in FIG. 1, the hollow fiber membrane is a so-called I-shaped filtration module in which both ends of the hollow fiber membrane are fixed to holding members respectively attached to the upper surface and the bottom surface of the housing. It is not limited to this configuration. The hollow fiber membrane bundle may be bent into a U shape, and both ends thereof may be fixed to a holding member fixed to the upper surface or the bottom surface of the housing. In this case, in order to hold the U-shape of the hollow fiber membrane bundle, the U-shaped top portion may be appropriately supported by a support member.

  Furthermore, in the embodiment of FIG. 1, the supply port of the polluted water is opened in the bottom fixing member that fixes and holds one end of the hollow fiber membrane, but the supply port does not need to be used also as the holding member for the hollow fiber membrane. . A supply port for the liquid to be processed may be separately opened on the wall surface of the housing.

  Furthermore, the cleaning bubbles may be mixed with the liquid to be treated and supplied, or an air diffuser for releasing the bubbles may be provided at the center of the hollow fiber membrane bundle.

It is the schematic which shows the structure of one Embodiment of a filtration module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Hollow fiber membrane 3 Holding member 4 Water holding member 5 Discharge port

Claims (7)

A hollow fiber membrane for solid-liquid separation of a liquid to be treated containing suspended substances;
The hollow fiber membrane is accommodated, and has a supply port to which the liquid to be processed is supplied and a discharge port for discharging a filtration residue liquid of the liquid to be processed, and is made of electron beam cross-linked polypropylene or fiber reinforced polypropylene. A filtration module comprising a housing; and a water collection holding part for holding one end of the hollow fiber membrane so that the filtered water in the hollow fiber membrane is discharged out of the housing. The filtration module according to claim 1, wherein the electron beam-crosslinked polypropylene or fiber-reinforced polypropylene has a tensile elastic modulus of 2200 MPa or more. The filtration module according to claim 2, wherein the electron beam cross-linked polypropylene or fiber reinforced polypropylene has a tensile elastic modulus at 80 ° C of 1100 MPa or more. The filtration module according to any one of claims 1 to 3, wherein the housing has a thickness of 5 to 10 mm, an outer diameter of 150 to 300 mm, and a length of 1500 to 2500 mm. The said hollow fiber membrane is a filtration module in any one of Claims 1-4 comprised by the porous membrane of the fluororesin. The filtration module according to claim 1, which is used for filtering water containing an oily substance. The filtration module according to any one of claims 1 to 6, which is used for filtration of a liquid to be treated at 70 ° C or higher.

Images