JP6940848B2 - Precoat filtration method and precoat filtration device - Google Patents

Description

The present invention relates to a precoat filtration method and a precoat filtration device.

Precoat filtration is a filtration method that can repeatedly perform high-precision filtration by precoating the surface of a filter medium with a filtration aid, and is used in a wide range of fields including surface treatment fields such as plating. However, cleaning waste liquid and used filtration aid may become cleaning waste during cleaning, and the final treatment thereof may become a problem.

There is a technical problem of increasing the amount of particles to be removed in order to reduce cleaning emissions, and although various studies have been conducted on this, there is no effective solution to date. rice field.

Japanese Unexamined Patent Publication No. 10-258208

An object of the present invention is to improve the above-mentioned conventional problems, that is, to provide a precoat filtration method and a precoat filtration device having excellent filtration processing capacity.

The precoat filtration method according to one aspect of the present invention is a filtration method in which a filtration aid is supplied to the surface of a filter medium to form a precoat layer, and the filtration aid is supplied in the presence of microbubbles to form the precoat layer. It is characterized by having a micro-bubble body feed pre-coating step, and having a water permeation step of permeating water through the pre-coating layer and the filter medium after the micro-bubble body feed pre-coating step.

In the above aspect, the water permeation step may be performed in the range of 1 minute or more and 120 minutes or less.

In the above aspect, the configuration may include an auxiliary agent-only precoating step of precoating the filtration aid without using the microbubbles in advance of the microbubble body feed precoating step.

The precoat filtration device according to one aspect of the present invention includes a microbubble supply means for supplying microbubbles to a filter medium together with a filtration aid at the time of precoating, and a water supply means for supplying water to the filtration aid and the filter medium. And, characterized by having.

The precoat filtration method according to one aspect of the present invention is a filtration method in which a filtration aid is supplied to the surface of a filter medium to form a precoat layer, in which microbubbles are supplied to form a precoat layer in the presence of microbubbles. It has a body feed precoating step, and has a water permeation step of permeating water through the precoat layer and the filter medium after the microbubble body feed precoating step. With such a configuration, a precoat filtration method having excellent filtration processing capacity can be obtained.

Further, the precoat filtration device according to one aspect of the present invention includes a microbubble supply means for supplying microbubbles to the filter medium together with a filtration aid at the time of precoating, and a water supply means for supplying water to the precoat layer and the filter medium. Have. With such a configuration, it is possible to obtain a precoat filtration device having excellent filtration processing capacity.

It is a model diagram which shows an example of the precoat filtration apparatus which concerns on one Embodiment of this invention. It is a graph which shows the distribution of the bubble diameter of the microbubbles generated by the microbubble generator. It shows the relationship between the filterable time and the water permeation time when the suspension to be filtered is filtered using the precoat filtration device of FIG. It shows the relationship between the filtration capacity and the water permeation time when the suspension to be filtered is filtered using the precoat filtration device of FIG.

Hereinafter, the precoat filtration method according to the embodiment of the present invention will be described.

The precoat filtration method of the present embodiment is a filtration method in which a filtration aid is supplied to the surface of a filter medium to form a precoat layer, and the filtration aid is used in the presence of microbubbles (hereinafter, also referred to as “MB”). It has a micro-bubble body feed pre-coating step of supplying and forming a pre-coating layer, and has a water permeation step of permeating water through the pre-coating layer and the filter medium after the micro-bubble body feed pre-coating step.

According to the above-mentioned precoat filtration method, it is possible to obtain a significantly higher filtration processing capacity as compared with the conventional precoat filtration method without using a special material or chemical. Further, as a result, the amount of the filtration aid used can be relatively reduced and the number of times of backwashing is required can be reduced, so that the filtration pause time can be shortened and the efficiency of the filtration process can be improved. Furthermore, it is possible to realize cost reduction by reducing the amount of water, filtration aid, etc. used and the waste products generated as a result of their use.

Further, although the precoat filtration method in the present embodiment is performed in combination with microbubbles, the conventional precoat filtration method without microbubbles can be applied as it is except for the combined use of microbubbles, and for this reason, it is extremely easy. Can be carried out.

Microbubbles The microbubbles used in the body feed precoating process refer to bubbles having a diameter of 1 mm or less. By using bubbles having a size in this range, the bubbles can be taken into the precoat layer, so that a precoat filtration method having excellent filtration processing ability can be provided. If the amount is small, large bubbles of 1 mm or more may be contained.

Air is usually used as the gas constituting the bubbles because it can be obtained at low cost, but a more inert gas such as nitrogen, carbon dioxide gas, or a rare gas can also be used. Further, if necessary, an oxidizing gas such as oxygen or ozone can be used.

Such microbubbles are usually supplied in a state of being dispersed in water or the like as a dispersion medium, and are also supplied to and mixed with a filtration aid dispersed in a dispersion medium such as water.

The microbubble body feed precoating step is preferably performed in the range of 30 seconds or more and 900 seconds or less. By performing the micro-bubble body feed precoating step in such a range, a high filtration processing capacity can be obtained.

The above-mentioned microbubbles dispersed in water can be easily obtained by using a fine bubble generator (macro bubble generator) obtained from Nikuni Co., Ltd. or the like. The water in which the microbubbles are densely dispersed, which is obtained by such a fine bubble generator, is visually recognized as milk. Here, the microbubbles dispersed in water are lost after a long time has passed since they were generated. Therefore, a fine bubble generator is provided near the precoat filtration device, or in the case of a pump-type fine bubble generator, filtration is performed. It is preferable to use it as a liquid feed pump to a container, and in the latter case, the entire device can be made compact and the cost of the device can be reduced.

A general filter aid can be used. Examples thereof include diatomaceous earth, cellulose, pearlite, activated carbon and the like, and the particle size is selected as before according to the purpose of filtration. That is, it is not necessary to change the particle size of the filtration aid used even when the microbubbles are used in combination. Therefore, the particle size range of the filter aid is usually 100 μm or less, and the lower limit of this range is appropriately selected according to the type of the filter medium to be used in combination. In addition, the amount of the filtration aid used for the precoating at one time is also the same as or about the same as the conventional condition without microbubbles.

A suitable mixing ratio of the dispersion medium for dispersing the microbubbles and the filtration aid (dispersion medium in which the microbubbles are dispersed) is examined and determined in advance. If the amount of microbubbles is too small with respect to the filtration aid, it is difficult to obtain the effect of the present invention sufficiently, and if the amount of microbubbles is too large, the number of leaking particles may increase during filtration and sufficient filtration may not be performed. ..

In the present embodiment, the micro-bubble body feed pre-coating step may be performed only once, but may be performed a plurality of times. By performing the micro-bubble body feed pre-coating step a plurality of times in this way, the filtration accuracy is improved.

The water permeation step is a step of permeating water such as purified water into the precoat layer and the filter medium after the microbubble body feed precoat step. By permeating water through the precoat layer and the filter medium after the microbubble body feed precoating step, the filtration processing capacity can be improved.

This water permeation step is preferably performed in the range of 1 minute or more and 120 minutes or less. By permeating water in such a range, it is possible to increase the amount of captured particles to be removed. The water permeation step may be performed in a reduced pressure state or a pressurized state, and the range of the pressure (gauge pressure) in the filter in the water permeation step is preferably −20 kPa or more and 20 kPa or less.

The precoat layer formed by such a microbubble body feed precoat step and a water permeation step captures particles to be removed not only on the surface of the precoat layer but also inside the precoat layer as in deep filtration. For this reason, especially when microfiltration is required, the auxiliary agent single precoating step of precoating the filtration aid without using the microbubbles is carried out prior to the microbubble body feed precoating step. be able to. At this time, the amount of the filtration aid used in the auxiliary agent single precoating step and the amount of the filtering auxiliary used in the microbubble body feed precoating step are determined in advance by examining them. The effect of the present invention can be sufficiently obtained by making the amount equal to or about the same as that of the conventional precoat filtration without bubbles, and more accurate precision filtration becomes possible as compared with the case where the auxiliary agent alone precoat step is not performed.

The auxiliary agent single precoating step may be performed only once or may be performed a plurality of times.

The precoat filtration method according to the present embodiment can be applied to general fields to which the precoat filtration method is applied, such as a surface treatment field such as plating, a food / chemical field, and the like.

Next, the precoat filtration device of the present invention will be described with reference to FIG. FIG. 1 is a model diagram showing an example of the precoat filtration device A.

The precoat filtration device A is a mixing tank 1, water in which microbubbles supplied to the mixing tank 1 are dispersed (hereinafter, may be referred to as “MB water”) or a storage tank (water supply means) for storing water. Filtering in which 2 and a filtration aid (not shown) supplied to the mixing tank 1 and deposited on the filter medium 7a are stored in a dispersion medium (hereinafter, referred to as “filtration aid suspension”). A stirrer 5 composed of an auxiliary agent storage tank 3, a stirring blade 5b for uniformly stirring various liquids in the mixing tank 1, and a motor 5a for rotationally driving the stirring blade 5b, and a storage tank. A micro-bubble generator that takes in the water stored in 2 and generates MB water and supplies it into the storage tank 2 (in this example, KTM15ND04S-001 manufactured by Nikuni, pressurized water flow rate 0.6 m ³ / hour, motor power 0. 56 kW. Pressurized dissolution type using a vortex turbine pump. Fig. 2 shows the distribution of the bubble diameter of the microbubbles generated by this fine bubble generator 6.) 6 and a filter equipped with a filter medium 7a inside. (Filtration area: 19.6 cm ² , filtration flow rate 5.88 L / hour) 7, a suspension suspension storage tank 4 to be filtered, and a treatment liquid tank 8 for storing the treatment liquid filtered by the filter 7 are provided. ing.

Further, the precoat filtration device A has a water supply line L6a that takes in water in the storage tank 2 and supplies it to the fine bubble generator 6, and MB water generation that supplies MB water generated by the fine bubble generator 6 to the storage tank 2. MB water supply line 2La (supplied upstream of pump P1 to supply MB water or water to MB water supply line 2La) including a line 6Lb and a pump P1 for supplying MB water or water in the storage tank 2 to the mixing tank 1. It is provided with a valve 2Laa for enabling the valve 2Laa and a valve 2Lab arranged downstream of the branch point between the MB water supply line 2Lb described later) and a pump branching from the MB water supply line 2La upstream of the pump P1. It is provided with an MB water supply line 2Lb (providing a valve 2Lba arranged near a branch point with the MB water supply line 2La) for supplying MB water or water to the mixing tank 1 or the filter 7 via P2. ..

Further, the precoat filtration device A is connected to the MB water supply line 2Lb and supplies the dispersion medium containing the filtration aid in the filtration aid storage tank 3 to the mixing tank 1 in the filtration aid supply line 3L (filter aid). It is provided with a valve 3La for supplying the dispersion medium containing the dispersion medium to the filtration aid supply line 3L), MB water in the mixing tank 1, water and a suspension of the filtration aid or a mixture thereof, and a mixture thereof, which will be described later. A filter supply line 1L for supplying the suspension to be filtered to the filter 7 (provided a valve 1La arranged closer to the mixing tank 1 from a connection portion with the pump supply line 9La described later) and a filter supply line 1L. MB water, water, a filtration aid suspension and a suspension to be filtered, which are connected to and supplied to the filter 7 via the pump P2, are supplied to the filter 7 with a pump supply line 9La (with a pump supply line 9Lb described later). It is provided with a valve 9Laa arranged closer to the filter supply line 1L from the connecting portion of the filter (), and MB water, water and a filtration aid suspension branched from the pump supply line 9La and supplied via the pump P2. Alternatively, a pump supply line 9Lb (providing a valve 9Lba) for supplying a mixture of these to the mixing tank 1 and a processing liquid storage tank supply line 8L (valve) for supplying the processing liquid filtered by the filter 7 to the storage tank 8. 8La is provided.) And.

Further, a pressure gauge is provided in the MB water generation line 6Lb, the filter supply line 1L, and the treatment liquid storage tank supply line 8L, and the storage tank 2 is a line for supplying water into the storage tank 2 (not shown). ) Is provided, and the microbubble generator 6 is provided with a gas supply line (not shown) that supplies a gas for forming microbubbles to the microbubble generator 6. Further, it is provided with equipment for receiving water discharged from the filter 7 when MB water, water and a suspension of a filtration aid (not shown) are supplied to the filter 7.

This precoated filtration device A is further connected to a suspension suspension storage tank 4 for storing a suspension (suspension to be filtered) containing particles to be removed and a suspension to be filtered by being connected to an MB water supply line 2Lb. 4L of suspension suspension supply line 4L for supplying the suspension to be filtered in the liquid storage tank 4 to the filter 7 (valve 4La for supplying the suspension to be filtered to the suspension supply line 4L to be filtered). ) And. The suspension to be filtered after the filtration treatment is stored in the storage tank 8.

According to the precoat filtration device A of the above embodiment, it is possible to easily realize a highly efficient and low cost precoat filtration method having excellent filtration processing capacity.

It should be noted that the above-described embodiment merely shows a typical embodiment of the present invention, and the present invention is not limited to the embodiment. That is, those skilled in the art can carry out various modifications according to conventionally known knowledge within a range that does not deviate from the gist of the present invention. As long as the precoat filtration method and the configuration of the precoat filtration device of the present invention are still provided, such deformation is, of course, included in the category of the present invention.

Examples and comparative examples of the precoat filtration method of the present invention will be specifically described below.

As the experimental device, the precoat filtration device A shown in FIG. 1 described above was used.

<Example 1>
[MB water permeation step through filter medium 7a]
Purified water was supplied into the storage tank 2 with all the valves of the precoat filtration device A closed, and at the same time, the fine bubble generator 6 was driven to replace the purified water in the storage tank 2 with MB water. Air was used as the gas for forming MB water. At this time, the MB generation pressure in the fine bubble generator 6 was 0.45 MPa, and the air intake amount was 0.4 L / hour. While maintaining the drive of the fine bubble generator 6 to the storage tank 2, the valve 2Laa, the valve 2Lab, the valve 1La and the valve 8La are opened, the stirring device 5 and the pump P1 are driven, and the MB water passes through the mixing tank 1. The mixture was supplied into the filter 7 and the MB water was permeated through the filter medium 7a. The permeation of MB water in the filter medium 7a was performed for 60 seconds.

[Micro bubble body feed precoat process]
Next, the valve 3La and the valve 9Lba were opened, and the pump P2 was driven to supply the filtration aid suspension stored in the filtration aid storage tank 3 to the mixing tank 1. The MB water and the filtration aid suspension supplied to the mixing tank 1 were stirred and mixed by the stirring device 5 in the mixing tank 1. In the mixed solution of MB water and the filtration aid suspension in the mixing tank 1 at this time, the volume ratio of the MB water and the filtration aid suspension was 1: 1 and the diatomaceous earth concentration was 0. It was 368% by volume.

The mixed solution of MB water and the filtration aid suspension mixed in the mixing tank 1 was supplied to the filter 7, and diatomaceous earth as a filtration aid was deposited on the filter medium 7a. Next, the valve 2Lba was opened, the valve 3La was closed, the pump P1 was stopped, and MB water was permeated through the filter 7 through the line 2Lb, the line 9La and the line 9Lb. As a result, the diatomaceous earth remaining on the line 2Lb, the line 9La and the line 9Lb can be supplied to the filter 7. The amount of diatomaceous earth per unit area on the filter medium 7a was 750 g / m ² .

[Water permeation process]
Next, by stopping the fine bubble generator 6, the MB water in the storage tank 2 was replaced with purified water, the valve 9Laa was opened, the valve 1La and the valve 9Lba were closed, and the particles were deposited on the filter medium 7a and the filter medium 7a. Purified water permeated the diatomaceous earth.

<Example 2>
Similar to Example 1 above, however, in the mixed solution of MB water and the filtration aid suspension in the mixing tank 1 in the microbubble body feed precoating step, the volume of the MB water and the filtration aid suspension. The ratio was 1: 1 or 3: 1 and the diatomaceous soil concentration was 0.368% by volume or 0.184% by volume. The amount of diatomaceous earth per unit area on the filter medium 7a was 380 g / m ² .

<Filtration time evaluation test>
In the precoated filtration device A in which the precoated filtration methods of Examples 1 and 2 were performed, the valve 4La was opened and the valve 2Lba was closed, and the concentration was 104 mg / L as the filtered suspension in the filtered suspension storage tank 4. The iron (III) hydroxide suspension prepared in 1 was supplied to the filter 7. The iron (III) hydroxide suspension was supplied to the filter 7 under the conditions of 3 m / hour in Example 1 and 6 m / hour in Example 2, and the filter medium 7a, the precoat layer and the captured removal were performed. Filtration was continued until the pressure loss (filter differential pressure) due to the target particles reached 90 kPa (a guideline for starting washing). The relationship between the filterable time and the water permeation time at this time was investigated. In Example 1, the test was conducted in a state where the pressures (gauge pressures) in the filter 7 before the precoat filtration were −8 kPa, −2 kPa, and 1 kPa, respectively. Further, in Example 2, the test was conducted in a state where the gauge pressure before the precoat filtration method was 3 kPa and 5 kPa. The results are shown in FIG.

<Filtration capacity evaluation test>
In the precoated filtration device A in which the precoated filtration methods of Examples 1 and 2 were performed, the valve 4La was opened and the valve 2Lba was closed, and the concentration was 104 mg / L as the filtered suspension in the filtered suspension storage tank 4. The iron (III) hydroxide suspension prepared in 1 was supplied to the filter 7. The iron (III) hydroxide suspension was supplied to the filter 7 under the conditions of 3 m / hour in Example 1 and 6 m / hour in Example 2, and the filter medium 7a, the precoat layer and the captured removal were performed. Filtration was continued until the pressure loss (filter differential pressure) due to the target particles reached 90 kPa (a guideline for starting washing). The relationship between the filtration capacity at this time (the mass of iron (III) hydroxide per unit projected area captured until the filtration differential pressure reached 90 kPa) and the water permeation time was investigated. In Example 1, the test was conducted in a state where the pressure (gauge pressure) in the filter 7 before the precoat filtration method was −8 kPa, −2 kPa, and 1 kPa, respectively. Further, in Example 2, the test was conducted in a state where the gauge pressure before the precoat filtration method was 3 kPa and 5 kPa. The results are shown in FIG.

<Evaluation result>
From FIG. 3, it can be seen that in both Examples 1 and 2, the substantially filterable time when the filtration differential pressure reaches 90 kPa becomes longer in accordance with the water permeation time. That is, it can be seen that the filtration processing capacity increases in accordance with the water permeation time in the water permeation step after the microbubble body feed precoating step. Further, in Example 1, it can be seen that the lower the gauge pressure before the precoat filtration method is performed, the longer the available filtration time and the higher the filtration processing capacity. Further, in Example 2, it can be seen that the filtration processing capacity is higher when the microbubble body feed precoating step is performed in a state where the mixing ratio of MB water in the mixing tank 1 is high.

Further, from FIG. 4, it can be seen that in both Examples 1 and 2, the filtration capacity increases in accordance with the water permeation time. That is, it can be seen that the amount of particles captured increases in accordance with the water permeation time in the water permeation time after the microbubble body feed precoating step. Further, in Example 1, it can be seen that the lower the gauge pressure before the precoat filtration method is performed, the larger the particle capture amount. Further, in Example 2, it can be seen that the filtration processing capacity is higher when the microbubble body feed precoating step is performed in a state where the mixing ratio of MB water in the mixing tank 1 is high.

6 Micro bubble generator (micro bubble supply means)
7a Filter media 2 Water supply means A Precoat filtration device

Claims (4)

In the precoat filtration method in which a filtration aid is supplied to the surface of the filter medium to form a precoat layer.
It has a microbubble body feed precoating step of supplying the filtration aid to form the precoating layer in the presence of microbubbles.
Precoat filtration method characterized by having a water permeation process for transmitting only water to the pre-coat layer and the filter medium after the microbubble body feed precoating process. The precoat filtration method according to claim 1, wherein the water permeation step is performed in a range of 1 minute or more and 120 minutes or less. The precoat filtration method according to claim 1 or 2, further comprising an auxiliary agent-only precoating step of precoating the filtration aid without using microbubbles in advance of the microbubble body feed precoating step. A microbubble supply means that supplies microbubbles to the filter medium together with a filtration aid during precoating,
And water supply means for supplying water only to the pre-coat layer and the filter medium of the filter material pre-coat layer is formed,
A pre-coated filtration device characterized by having.

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