JPH0468002B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a fluid filtration device for removing impurities from a fluid. [Prior art] Conventional techniques for removing impurities from a fluid include the filter method, in which the fluid is pumped toward a filter and the impurities are filtered out by the filter, and the impurities are caused to collide with a cylindrical wall surface using centrifugal force to settle. This is done using centrifugation. In addition, as a device for removing dust from dust-containing gas, a DC voltage of tens of thousands of volts is applied between opposing electrodes to generate a discharge, and impurities in the gas sent between the electrodes are captured by the dust collecting electrode. There is a device that uses electrostatic precipitator method. [Problems to be solved by the invention] However, in the impurity removal device using the filter method or centrifugation method as described above, it is difficult to perform precision filtration such as removal of colloid particles, which has recently become a demand. However, there was a problem that it was technically difficult, and even if it were possible, it would not be cost-effective and would not be suitable for practical use. In other words, the filtration accuracy required these days has become extremely strict, such as dust of 1μ or less, moisture in oil of 50PPM or less, and oil in wastewater of 15PPM or less, and the filter method and centrifugal separation method mentioned above can meet these requirements. It cannot be done. On the other hand, electrostatic precipitator-based devices are extremely high-performance devices that can collect particles of 1μ or less, but because they use a high-voltage power supply, they require insulation and explosion-proof specifications, making the devices larger and more expensive. There was a problem that it could not be used with water-based fluids. However, the demand for highly accurate filtration as described above has become even greater as surfactants have recently come to be used in large quantities. [Object of the Invention] Filtration that requires extremely high precision as described above is in the area of colloid filtration, and it is difficult to achieve such filtration by mere physical means such as the above-mentioned filter method and centrifugation method. Therefore, in the present invention, when the molecules and particles in the colloidal region are charged due to dielectricity, ion adsorption, etc., a zeta potential is generated due to an electric double layer at the interface between these particles and the fluid, and this zeta potential causes the interparticles to Focusing on the fact that the particles repel each other due to the Coulomb force generated in the fluid and become suspended in the fluid, it is difficult for them to settle.This zeta potential is eliminated and the colloidal particles are pre-compared before passing through the filter by settling or floating due to agglomeration and coarsening. An object of the present invention is to provide a fluid filtration device that can improve filtration accuracy and extend filter life by reducing filter load by removing impurities with large target particles. [Means for Solving the Problems] In order to achieve the above object, the fluid filtration device according to the present invention includes a cylindrical outer tube electrode and an inner tube provided at the same potential as the outer tube electrode. A charged electrode is arranged between the pipe-shaped internal electrode and insulated from both the inner and outer electrodes, the surface of the inner electrode is covered with a filter made of a dielectric, and a charged electrode is arranged between the outer electrode and the charged electrode. A voltage source that applies a voltage is provided to cause the fluid press-fitted between the outer cylindrical electrode and the charged electrode to flow between the charged electrode and the inner electrode, and to flow out through the filter to the outside. This is what I did. [Operation] According to the fluid filtration device of the present invention, by passing the fluid into the electric field between the outer cylinder electrode and the charged electrode, colloidal particles having a zeta potential on the surface are transferred to the surface of the charged electrode by Coulomb force. are collected and the zeta potential is canceled out. As a result, colloidal particles coagulate or float, and relatively large impurities are removed before passing through the filter. Next, by flowing fluid between the charged electrode and the internal electrode, the remaining colloid particles are polarized in the electric field between the charged electrode and the internal electrode, and Coulomb force is applied to the surface of the filter, which generates a strong zeta potential. They are attracted and adsorbed, forming a cake layer of impurities on the filter surface, and this cake layer provides highly accurate filtration performance. [Example] Hereinafter, the present invention will be described in detail based on an illustrated example. 1 to 3 show the basic principle of the fluid filtration device according to the present invention. In the figures, 1 is a cylindrical charging electrode with both ends closed, and a processing chamber 2 is located above the charging electrode 1. The inflow port 3 and the energizing hole 4 that lead to the
Furthermore, an electrode support hole 5 and a drain hole 6 are provided at the bottom. Reference numeral 7 denotes a pipe-shaped internal electrode provided at the center of the charging electrode 1. A passage 8 passes through the internal electrode 7 in the axial direction, and a large number of water holes 9 are formed in the peripheral wall. Further, the surface of the inner and outer poles 7 is covered with a filter 10 made of a dielectric material, and one end is connected to the outlet 12 via an insulator 11. 13 is a power supply device. These components are constructed by inserting the internal electrode 7 into the processing chamber 2 of the charging electrode 1 through the electrode support hole 5, supporting and fixing the insulator 11 part in the electrode support hole 5, and connecting the outlet 12 to the charging electrode 1. Further, one terminal of the power supply device 13 is connected to the charging electrode 1, and the other terminal is connected to the internal electrode 7 through the lead-in insulator 14 supported in the current carrying hole 4. ing. As shown in FIG. 2, this device is connected from an untreated liquid tank _T1 to an inlet port 3 via a pump P.
On the other hand, the outlet 12 is piped to the clean tank _T2 . Next, the basic filtration process using the apparatus shown in FIGS. 1 to 3 above will be explained. When a voltage supplied by the power supply 13 is applied between the charged electrode 1 and the internal electrode 7 and the filter 10 is placed in an electric field, the filter 10 made of a dielectric material is polarized in the direction of the electric field, and a strong zeta is formed on its surface. A potential is generated. Therefore, when the fluid is forced into the processing chamber 2 through the inlet 3, the charged colloidal particles in the fluid are attracted by the Coulomb force to the zeta potential generated on the surface of the filter 10 and adsorbed to the surface of the filter 10.
The colloid particles, which have the same potential as the surface of the filter 10 due to this adsorption, lose their zeta potential and aggregate due to Van der Fars force, forming a cake layer of aggregates on the surface of the filter 10. The colloidal particles forming this cake layer are aggregated by the filter 10.
The cake layer prevents impurities from passing through with a much higher filtration accuracy than the filter 10 originally has because the pores of the filter 10 are made small. And 10 filters
Since the particles are polarized, the colloidal particles do not necessarily aggregate on the surface of the filter 10 and enter the inside, and the filter 10 will not be clogged. The voltage supplied from the power supply device 13 is a DC voltage of 1000 to 3000 V/cm when the fluid is a gas, an AC voltage of 10 to 200 V/cm when the fluid is a non-aqueous liquid, a weight voltage of AC and DC, or a DC voltage. , or in the case of an aqueous liquid, an alternating current voltage or a superimposed voltage of alternating current and direct current of 1 to 20 V/cm is preferably used. However, the selection of such voltage type and voltage value is
It is appropriately determined depending on the electric resistance specific to the fluid, and is preferably appropriately selected experimentally. Therefore, the type of voltage and voltage value are not necessarily limited to those shown above. However, in the case of a water-based fluid, DC charging involves the risk of electrolytic corrosion of the electrodes due to electrolysis or the generation of hydrogen and oxygen, so AC or AC/DC superimposed voltage is desirable. In the case of alternating current, the fluid is violently agitated in response to cycle fluctuations, and it is presumed that the zeta potential disappears due to the agitation, causing aggregation of colloids. In addition, the charging effect due to the DC component generated by the polarity effect of AC, or the synergistic effect of both, is also considered to be the cause of aggregation. In addition, the flow rate of the fluid is determined according to the viscosity of the fluid. 4-6 illustrate a first embodiment of a fluid filtration device according to the present invention. In the figure, 1 is a cylindrical charging electrode with both ends open. 7
is a pipe-shaped internal electrode provided at the center of the charging electrode 1, through which a passage 8 passes through in the axial direction.
Reference numeral 15 denotes a cylindrical outer tube electrode with both ends closed and having a processing chamber 2 housing the charging electrode 1 and the internal electrode 7, and this outer tube electrode 15 is connected to the protective insulator 1.
The charging electrode 1 is supported concentrically via the electrode 6. The outer cylinder electrode 15 has an inlet 3 communicating with the processing chamber 2 and a current supply hole 4 in the upper side of the electrode, and an electrode support hole 5 and a drain hole 6 in the bottom thereof. The internal electrode 7 projects outward from the electrode support hole 5, and the internal electrode 7 has an outlet 12 at the tip of this projecting portion. The outer cylinder electrode 15 and the internal electrode 7 are in contact with each other at the electrode support hole 5, and therefore, the outer cylinder electrode 15 and the internal electrode 7 are always at the same potential. Further, the surface of the internal electrode 7 is covered with a filter 10 made of a dielectric material at the portion facing the charging electrode 1, and one end of this filter 10 is supported by a support protrusion 17 formed in the shape of a brim on the internal electrode 7. The other end is supported by the upper surface 15a of the outer cylindrical electrode 15 via an insulator 18 provided with a gap from the upper end of the internal electrode 7. 13
is the power supply device. With the above-described configuration, the fluid injected from the inlet 3 in this device passes between the outer cylindrical electrode 15 and the charging electrode 1, passes downward, then passes through the filter 10, and flows from the upper end of the inner electrode 7. A flow path is formed that enters the passage 8 and exits from the outlet 12. Next, the operation will be explained. In this device, the fluid press-injected from the inlet 3 first passes through an electric field between the outer cylinder electrode 15 and the charging electrode 1. Therefore, colloidal particles having a zeta potential on the surface gather on the surface of the charged electrode 1 due to Coulomb force, where the zeta potential is canceled out. Since the only force that acts between colloid particles whose zeta potential is canceled is the Juan de Wears force, the particles aggregate and become coarse due to this intermolecular attraction. If the coarse colloidal particles have a higher specific gravity than the fluid, they will settle and separate. Examples of sedimentation include fine particles in gas, water and fine particles in oil, and SS in water. In addition, coarse colloidal particles float and separate when their specific gravity is lower than that of a fluid, and an example of this is oil in water. In addition, when the fluid is water-based, metal ions generated by electrolysis of water due to the application of voltage erase the zeta potential of colloid particles and cause the colloids to aggregate, and active metal hydroxides may encapsulate the colloids. It is thought that this effect is synergistic, such as coagulation. On the other hand, the remaining colloid particles that could not be coagulated and sedimented collect on the surface of the filter 10 along the filter flow path, but a charged electrode 1 is placed on the surface of the filter 10.
A zeta potential is generated by the electric field generated by the voltage applied between the internal electrode 7 and the internal electrode 7, and a cake is formed on the surface of the filter 10 in exactly the same manner as explained in the basic principle of FIGS. 1 to 3 above. form a layer. As described above, in the device of this embodiment, before passing the fluid through the filter 10 placed in an electric field, the zeta potential of the colloid particles is erased between the outer cylindrical electrode 15 and the charged electrode 1, so that the colloid particles coagulate and settle or float. Therefore, relatively large particles of impurities can be removed before passing through the filter 10. Therefore, the load on the filter 10 is reduced,
Its lifespan is extended. It can also contribute to obtaining good filtration accuracy with a small number of filtration times. Note that the type and voltage value of the voltage applied between the charging electrode 1 and the internal electrode 7 or the outer cylinder electrode 15, the velocity of the fluid, etc. are the same as those explained in the above-mentioned basic principle. 7 and 8, the inlet 3 is arranged above the processing chamber 2 so that the fluid flows in from the tangential direction of the inner circumference of the outer cylindrical electrode 15, and
A dielectric material 1 such as glass wool is placed between the charging electrode 1 and the charging electrode 1.
Fig. 9 shows a second embodiment of the present invention in which 9 is interposed. This second embodiment is basically the same as the first embodiment, and includes a cylindrical charging electrode 1, an internal electrode 7 provided at the center of the charging electrode 1,
It also includes an outer cylindrical electrode 15 that accommodates the charged electrode 1 and the internal electrode 7 and has the same potential as the internal electrode 7, and the surface of the internal electrode 7 is covered with a filter 10 made of a dielectric material. As described above, in the apparatus of this embodiment, the inlet port 3 is provided above the processing chamber 2 so that the fluid flows in from the tangential direction of the inner circumference of the outer cylindrical electrode 15. Therefore, the fluid flows into the processing chamber 2 while spirally swirling, and is evenly sent between the outer cylinder electrode 15 and the charging electrode 1, and when attracting colloid particles with Coulomb force, the surface of the charging electrode 1 is efficiently It can be used well. In addition, in this embodiment, the outer cylinder electrode 15 and the charging electrode 7
By interposing a dielectric material 19 such as glass wool between them, the dielectric material 19 is polarized by the voltage applied between the outer cylindrical electrode 15 and the charged electrode 7, which is equivalent to having a large number of electrodes interposed between them. effect can be obtained. Therefore, the colloidal particles between the outer cylinder electrode 15 and the charged electrode 7 can be aggregated more efficiently, and the filtration accuracy and life of the filter 10 can be improved. In addition, in this embodiment, the outer cylinder electrode 15 and the inner electrode 7
are connected by an inclined wall 20, and a cleaning liquid collecting chamber 21 isolated from the processing chamber 2 is formed between the inclined wall 20 and the bottom surface 15b of the outer cylinder electrode 15. The drain hole 6 is provided in the innermost part of the processing chamber 2, that is, in the side wall of the outer cylinder electrode 15 near the lowermost end of the inclined wall 20, and the outlet 12 is provided in the bottom surface of the outer cylinder electrode 15. Therefore, the impurities that have settled in the processing chamber 2 are efficiently discharged from the drain hole 6. Reference numeral 22 in the figure is an insulating plate that suppresses the rise of the filter 10 due to the upward flow, and is pressed by a spring 23 interposed between the top surfaces of the processing chamber 2. 9 and 10 show a third embodiment of the present invention in which a large number of internal electrodes 7 are provided inside a cylindrical charging electrode 1. FIG. This third embodiment is similar to the second embodiment described above.
This is a larger version of the device of the embodiment, with two inflow ports 3 in the tangential direction, and a large number of internal electrodes 7 (eight in the drawing) covered with a filter 10 along the inner peripheral surface of the charging electrode 1. The other components are the same as those of the previous embodiment. By providing a large number of internal electrodes 15 covered with filters 10 in this manner, processing capacity can be improved. The fluid filtration device as described in the above embodiments can be used to remove particulates from gases such as air and gas, dehydrate and remove particulates from non-aqueous lubricating oils, processing oils, cleaning oils, etc., and remove particulates from water-based pure water. It is used to remove oil and fine particles from waste water, drinking water, lubricating fluids, processing fluids, cleaning fluids, etc. Next, experimental data using a prototype of the fluid filtration device according to the present invention described as the first embodiment above will be shown. a Removal of particulates in nitrogen gas Filtration conditions Gas flow rate 0.5m ² /Hr, charging voltage 5000VDC/3
cm, data fine particles 0.1 to 1μ dust, filter nominal 1 micron, number of passes 1

[Table] It is clear that the processing capacity is improved by applying voltage. b. Comparative filtration test of DC and AC charging of lubricating oil. Filtration conditions: Flow rate 1/min, charging voltage AC and DC 0~
10000V/3cm filter nominal 1 micron, viscosity
56cst, temperature 25℃

[Table] According to this data, there is no big difference between AC and DC charging for oil, but DC charging is slightly more effective. The most effective voltage is 500V DC, which is judged to be the most suitable voltage for erasing zeta potential and generating zeta potential. Furthermore, as is clear from this data, in the fluid filtration device according to the present invention, the filtration ability decreases when a voltage exceeding 500V is applied to both AC and DC. It can be seen that impurities have been removed from the original. c Removal of metal salts from water glycol liquid Filtration conditions Flow rate 1/min, charging voltage AC 25V/3cm, filter nominal 1 micron, viscosity 46cst, temperature 25℃,
quantity 20

[Table] This data is an example in which AC25V/3cm was used as the applied voltage to prevent galvanic corrosion due to electrolysis, and it was observed that the filtration performance was significantly improved even with AC voltage. d Oil-containing wastewater treatment Filtration conditions Flow rate 1/min, filter nominal 1 micron,
However, if the applied voltage is 12VDC + 12VAC superimposed, glass wool must be inserted between the outer cylinder electrode and the charged electrode.

[Table] Compared to the case where only AC voltage was applied, good filtration results were obtained with fewer treatments by applying a superimposed voltage of AC and DC and interposing glass wool between the outer cylinder electrode and the charged electrode. From the above experimental data, it is clear that the fluid filtration device according to the present invention can perform extremely high-precision filtration regardless of whether it is a gas, a wastewater system, or an aqueous liquid. It should be noted that the present invention is not limited to the above embodiments, and appropriate design changes can be made without departing from the scope of the claims. [Effects of the Invention] As is clear from the above description, according to the fluid filtration device of the present invention, the zeta potential of impurities in the colloid region is reduced between the outer cylinder electrode and the charged electrode at a stage before passing through the filter. By erasing the impurities in the colloidal region, the impurities in the colloidal region are aggregated into coarse particles by Van der Juaars force (intermolecular attraction), and the aggregated relatively large impurities can be separated by settling or floating, and the subsequent fluid flow path can be separated. The zeta potential of impurities in the remaining colloid region is erased between the charged electrode to be formed and the internal electrode, and the intermolecular attraction allows the filter surface to have a higher filtration precision than the filter originally has.
Therefore, it is possible to demonstrate extremely high-precision filtration performance that cannot be achieved by conventional physical means such as filter methods and centrifugation methods, and
The load on the filter can be reduced and the life of the filter can be significantly extended. Moreover, good filtration accuracy can be obtained with a small number of filtration times. Moreover, it does not require high voltages of tens of thousands of volts like electrostatic precipitators, but only a low voltage can be applied.
It is easy to ensure insulation, and there is no need for explosion-proof specifications, making it easy to downsize the entire device, and
It has the advantage that it can be manufactured at low cost and can also be applied to water-based fluids.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of the device according to the basic principle of the present invention, FIG.
The figures are a radial sectional view of FIG. 1, FIG. 4 is a partially cutaway perspective view of the device according to the first embodiment of the present invention, FIG. 5 is a longitudinal sectional view of FIG. 4, and FIG. 4 is a radial sectional view, FIG. 7 is a partially cutaway plan view of a device according to a second embodiment of the present invention, FIG. 8 is a longitudinal sectional view of the same, and FIG. 9 is a third embodiment of the present invention. FIG. 10 is a partially cutaway plan view of the device according to the present invention, and FIG. 10 is also a longitudinal sectional view. DESCRIPTION OF SYMBOLS 1...Charging electrode, 3...Inflow port, 7...Internal electrode, 10...Filter, 13...Power supply device, 15
...Outer cylinder electrode.

Claims (1)

[Claims] 1. A charged electrode is arranged between a cylindrical outer tube electrode and a pipe-shaped inner electrode provided inside the outer tube electrode at the same potential as the outer tube electrode, insulated from both the inner and outer electrodes. , the surface of the internal electrode is covered with a dielectric filter, a voltage source is provided for applying a voltage between the external electrode and the charged electrode, and a fluid is press-fitted between the external cylindrical electrode and the charged electrode. 1. A fluid filtration device, characterized in that the fluid is configured to flow into between a charging electrode and an internal electrode, and flow out through the filter to the outside.