JPS61161190A - Device for flocculating impurity in liquid - Google Patents

Abstract

PURPOSE:To permit the flocculation of the impurities even in liquid having low electrical conductivity without decreasing the purity thereof and without forming unnecessary ions by flocculating the impurities in the liquid by the hydroxide of a metal forming electrodes. CONSTITUTION:Electrolytic cells 6a, 6b having the electrodes 13, 14 formed of the metal (e.g.; copper) which is easily dissolved by electrolysis and a constant current device for impressing the voltage for obtaining the prescribed current density in the liquid in said electrolytic cells to the above-mentioned electrodes are respectively provided and the impurities in said liquid are flocculated by the hydroxide of said metal. As a result, the impurities are flocculated without forming the unnecessary ions and without decreasing the purity of the liquid having the low electrical conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for coagulating impurities such as suspended substances and solute substances contained in a liquid.

BACKGROUND OF THE INVENTION In recent years, water with extremely high purity has been used in the production of electronic equipment parts, medical equipment parts, high purity chemical products, and the like.

However, such highly purified water cannot be produced by hand at a low cost, and if large quantities are consumed, the cost of the product will rise.

Therefore, it is a natural idea to remove the impurities from used water that has been contaminated with impurities and recycle the water.

Even when used water is discharged without being recycled, it is necessary to remove impurities to the extent that it does not violate water quality standards based on the Water Pollution Control Law.

Furthermore, if polluted groundwater, river water, etc. can be purified to high purity water, the product cost will be lower than when high purity water itself is obtained.

By the way, for example, when polishing debris generated by polishing wafers of silicon, gallium arsenide, etc. in a semiconductor process is mixed into water as an impurity, the polishing debris is dispersed in the water in the size of colloidal particles.

Therefore, the water after use is in the form of a suspension containing abrasive debris as a suspended substance, and solid-liquid separation is difficult with ordinary filtration.

Therefore, in order to separate the suspension into solid and liquid, it is necessary to first aggregate the suspended matter prior to filtration. Furthermore, the same can be said of solutions containing dissolved substances such as organic substances.

The first conventionally known method for agglomerating impurities in this manner is electrolysis.

In this electrolysis method, sulfuric acid or the like is added to the liquid to increase its electrical conductivity, and a metal plate that is not easily corroded by electrolysis, such as a plate made of lead coated with titanium, is used as an electrode.

If suspended matter is contained in water, this suspended matter generally has an electric charge, so that the suspended matter is electrically neutralized by the electrode and coagulates.

The flocculated suspended solids float to the surface by fine bubbles of hydrogen and oxygen generated at the electrode, and the flocculated suspended solids are filtered out.

Note that in the electrolysis method for liquids that inherently have high electrical conductivity, such as seawater, aluminum or the like is used as an electrode. In this case, impurities are adsorbed and aggregated by the metal hydroxide formed when the metal dissolved from the anode immediately reacts with water.

A second conventionally known method for coagulating impurities is to add a large amount of highly ionized substances such as strong electrolytes, strong acids, and strong bases to the liquid. In this method, ions generated by ionization electrically neutralize suspended substances and coagulate and precipitate them.

A third conventionally known method for agglomerating impurities is to add a water-soluble metal salt to the liquid and then add a base. In this method, metal hydroxide produced by neutralization of a metal salt and a base adsorbs impurities and coagulates and precipitates them. Therefore, this third method is effective for liquids containing not only suspended substances but also dissolved substances such as organic substances that do not have much electric charge as impurities.

Problems to be Solved by the Invention However, in the second method, additive substances remain as impurities at high concentrations, and even if suspended substances are completely removed, the water after this treatment must be recycled as is. I can't really do that.

On the other hand, in the third method, the concentration of the added metal salt as an impurity may be low. However, new ions are generated as a result of neutralization, and even with this third method, the treated water cannot be recycled as it is.

For recycling, newly generated ions must be removed, which requires a large amount of ion exchange resin. Therefore, a large amount of expense is required to recycle water, making recycle use meaningless.

The same reason why a large amount of ions remain in the water after filtration is the same in the first and second methods. Moreover, a large amount of electrolyte, metal hydroxide, etc. is attached to the solid residue that is agglomerated and separated.

For this reason, for example, it is difficult to melt and recrystallize and reuse polishing waste from silicon wafers, and the utility value of the solid residue is extremely low.

In view of the above-mentioned problems, the present invention provides an impurity in a liquid that can aggregate impurities without reducing its purity even in a liquid with low electrical conductivity, and that reduces the amount of adhesion of other substances to the impurities. The purpose of the present invention is to provide a device for agglomerating .

Means for Solving the Problem The device according to the invention for agglomerating impurities in a liquid comprises an electrolytic cell 6a having electrodes 13, 14 made of metals that are easily dissolved by electrolysis.

6b, and a constant current device that applies a voltage to the electrodes 13, 14 to obtain a predetermined current density in the liquid in the electrolytic cells 6a, 6b, and the liquid is heated by the metal hydroxide. It is designed to coagulate the impurities inside.

Operation In the apparatus for agglomerating impurities in a liquid according to the present invention, the electrodes 13, 14 are formed of a metal that is easily dissolved by electrolysis, and a voltage is applied to the electrodes 13, 14 in the liquid.

Therefore, impurities in the liquid are adsorbed and aggregated by the metal hydroxide forming the electrodes 13,14. Furthermore, by controlling the current density in the liquid, the amount of metal hydroxide produced can be controlled.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5.

Figure 1 shows that water of relatively high purity is used, impurities contained in the used water are coagulated and filtered by electrolysis, and the water that has been returned to its original purity is circulated and reused. This is a device for obtaining highly pure residue.

First, highly purified water is used and discharged by the wastewater discharge source 1 for X17 minutes, and is stored in the wastewater tank 3 via either the filter 2a or 2b having a 200 μm filter medium.

In other words, in the wastewater from wastewater discharge source 1, there is a diameter of 200 μm.
Filters 2a and 2b are provided so that the thin tube portion of the apparatus of this embodiment will not be clogged even when such large impurities are contained.

Further, the discharge amount from the wastewater discharge source 1 is not necessarily constant, and the average is considered to be X27 minutes.

For this purpose, the waste water tank 3 needs to have a capacity of at least about 2xl, and may have a larger capacity if the overall size of the device allows for it.

The waste water in the waste water tank 3 is pumped out by the pump 4, set to a flow rate of (X+α)17 minutes by the constant flow valve 5, and then forced into either the electrolytic cell 6a or 6b.

The outer boxes 7 of the electrolytic cells 6a and 6b are made of synthetic resin with sufficient insulation and airtightness, and have a water inlet 11 and an outlet 12 in their lower and upper parts, respectively, as shown in FIG. have.

Inside the electrolytic cells 6a and 6b, a large number of electrode plates 13 and 14 are arranged so as to alternately face each other.

These electrode plates 13 and 14 are made of metals such as copper, iron, zinc, nickel, and aluminum that are easily melted by electrolysis, and have a thickness of 1 to 5 mm.

A partition plate 15 is sandwiched between electrode plates 13 and 14 facing each other. These partition plates 15 are made of synthetic resin such as vinyl chloride, which has sufficient insulation properties.
It has a thickness of 1 to 5 u, a width of 5 wm or less, and a length of 100 mm or less.

In other words, the electrode plates 13 and 14 are sufficiently insulated from each other via the partition plate 15 of a predetermined thickness, and are fixed at a distance between them such that desired electrical conduction can be maintained. Further, lead wires 16 made of copper or the like are connected to each of the electrode plates 13 and 14.

In this way, the electrode plates 13, 14, the partition plate 15, and the lead wire 16 constitute an electrode block 17, and the electrode block 17 is housed in the outer box 7 so as to be in close contact with it. Note that instead of the partition plate 15, a square bar or a round bar having a diameter of 1 to 5N may be used.

A constant current device (not shown) is connected to the lead wire 16, and a voltage corresponding to the electrical conductivity of the wastewater is applied to the electrode plates 13 and 14 so as to obtain a predetermined current density, for example, O, IA/dm2. is applied to

Therefore, the wastewater injected into either the electrolytic cell 6a or 6b from the inlet 11 is electrolytically treated while rising between the electrode plates 13 and 14 at a predetermined speed, and is discharged from the outlet 12. Through this electrolytic treatment, the metal on the anode side of the electrode plates 13 and 14 is dissolved and becomes metal hydroxide, and this metal hydroxide adsorbs and aggregates impurities such as suspended and dissolved substances in the wastewater. flocs are generated by

A predetermined amount of the flocs rises by adsorbing the above-mentioned wastewater flow and the generated fine bubbles of hydrogen gas and is also discharged from the outlet 12, but some of the flocs and precipitated metal water Part of the oxide is on the electrode plate 13.1
It adheres and deposits on the anode surface of No. 4.

Therefore, if the current used for electrolysis is direct current,
The above-mentioned sticking and depositing occurs on one of the electrode plates 13,14. For this reason, the passage of waste water becomes narrower and the electrolysis area becomes smaller over time. As a result, the current density increases abnormally, causing electrolysis failure, and finally solid-liquid separation becomes impossible.

Furthermore, if the current used for electrolysis is direct current, even if both electrode plates 13 and 14 are made of the same metal,
Only the anode is melted and consumed.

For this reason, the time during which electrolysis is possible is only half as long as it would be if both electrode plates 13, 14 were consumed evenly.

For these reasons, in this embodiment, a polarity reversing device (not shown) is installed between a DC power source (not shown) and the electrolytic cells 6a and 6b to change the electrical polarity of the electrode plates 13 and 14 to a predetermined value. It is inverted at time intervals. ``In this way, the anode on which the flocs etc. are fixed and deposited becomes the cathode at the same time as the polarity is reversed.
Hydrogen gas is generated from this cathode. As a result, the flocs and the like that have adhered and accumulated are separated from the electrode plates 13 and 14, and the adhesion and accumulation do not progress.

However, even in this case, the electrode plate 13.1'4 is consumed and eventually disappears. However, before the electrode plates 13.14 disappear, the distance between the electrode plates 13.14 increases and the area of the electrode plates 13.14 gradually decreases. , the voltage between electrode plates 13 and 14 increases.

Therefore, in this embodiment, a voltmeter is connected to the power supply system for electrolysis, and when the indicated value of this voltmeter exceeds a predetermined value, the electromagnetic valve 21a installed in front of the population 11 of the electrolytic cells 5a and 5b , 21b, those that are open are closed and those that are closed are opened. Also, the solenoid valve 21
At the same time as the electrolytic cells 5a and 21b are switched, the energization to the electrolytic cells 5a and 5b is switched. Electrolytic cell 6 that should be used in this way
Since the electrode blocks 17a and 6b are automatically switched, the electrode blocks 17 of the electrolytic cells 6a and 6b that are inactive are replaced with new ones.

The treated water discharged from the outlets 12 of the electrolytic cells 6a and 6b is
The electrolytic cells 5a and 5b are press-fitted into a flotation separation tank 22 located substantially directly above the electrolytic cells 5a and 5b.

The flotation separation tank 22, as shown in FIGS. 3A and 3B,
The bottom portion 23 has a substantially conical shape, and the side portions are double walls 24. The inlet 25 of the flotation tank 22 projects from the bottom 23 and is located approximately at the center of the flotation tank 22 . The outlet 26 of the flotation tank 22 communicates with the gap between the double walls 24 via a small hole 27 .

A scraping device 33 in which a scraping fin 31 made of rubber or urethane foam is moved by a chain 32 at several centimeters per minute is installed near the upper part of the flotation separation tank 22 . Further, near the side of the flotation separation tank 22, a plurality of floating residue receiving tanks 35 having paper or cloth bags 34 are installed, and the floating residue receiving tanks 35 communicate with the wastewater tank 3. .

Most of the flocs that are forced into the flotation tank 22 from the population 25 along with the treated water and hydrogen gas float in the flotation tank 22 and reach the water surface, forming a layer of flocs. This layer of floc is scraped up on the water surface by a scraping device 33, and floating residual light falls into a tank 35.

The flocs dropped into the tank 35 are filtered out by the bag 34, and the filtered water is returned to the waste water tank 3.

Further, the concentrated solid residue is accumulated in the bag 34, and when the weight of the solid residue reaches a predetermined value, the floating residue light is emitted from the tank 22.
Another floating residue light installed adjacently is automatically exchanged with a tank (not shown).

The flocs with insufficient adsorption of hydrogen gas are transferred to the flotation separation tank 22.
It settles inside, and deposits on the bottom 23.

The bottom part 23 is opened only for a very short time at predetermined time intervals by means of an electric valve 36. The flocs deposited on the bottom 23 are guided to the tank 35 by floating residue light in the same way as the flocs which float.

However, other parts of the floc are removed from the double wall 24 along with the treated water.
It rises therein, passes through the small hole 27 and is discharged through the outlet 26.

The treated water discharged from the outlet 26 is stored in a treated water tank 37, then pumped out by a pump 41, set to a flow rate of (X+α)l1 by a constant flow valve 42, and then pressurized into a precision filter 43. . The treated water tank 37 needs to have a capacity of at least about 2xf since there is some deviation in the amount of treatment in the previous process, and may have a larger capacity if there is room for the overall size of the apparatus.

The flocs that cannot be completely removed in the flotation separation tank 22 usually have a size of 1 μm or more. For this purpose, the precision filter 43 has a diameter of 0.5 μm as shown in FIGS. 4 and 5.
It has a second filter medium 44, which is automatically replaced.

That is, a pressure gauge 45 is installed on the inlet side of the precision filter 43, and when the indicated value of the pressure gauge 45 exceeds a set value due to clogging of the filter medium 44, the electromagnetic valves 46 and 47 are first activated. Closed. Then, several seconds after this closure, the solenoid valve 51
．． 52 is released.

Then, compressed air is introduced into the microfilter 43 via the electromagnetic valve 52, and the treated water in the microfilter 43 is returned to the treated water tank 37 via the electromagnetic valve 51.

Thereafter, the outer cylinder 55 of the precision filter 43 is pushed down by the air cylinder 53 and crank 54 as shown in FIGS. 4A and 4B. A pin 56 is fixed to the outer cylinder 55, and this pin 56 is guided in a guide groove 57.

Therefore, at the beginning of the stroke of the air cylinder 53, the outer cylinder 55 is separated from the fixed lid 61, and eventually only the outer cylinder 55 turns over by 90 degrees as shown in FIG. 4C. However, the outer cylinder 55
Since the treated water inside has already been returned to the treated water tank 37 as described above, it will not flow away from the outer cylinder 55 due to the overturning of the outer cylinder 55.

After that, a filter medium clip 62 as shown in FIG.
3 remains open and is pressed by cylinder 64. When the filter media clip 62 is inserted into the outer cylinder 55,
Due to the pressure of the cylinder 63, the filter media clip 62 clamps the deteriorated filter media 44. Further, the cylinder 64 pulls back the filter medium clip 62 with the filter medium 44 between them from inside the outer cylinder 55 to its original position, as shown in FIGS. 5A and 5B.

When the filter media clip 62 is pulled back to the position shown in FIGS. 5A and 5B, the filter media clip 62 is released by the cylinder 63, and the filter media 44 falls and is stored in a used filter media box (not shown).

Subsequently, a new filter medium receiver 6 as shown in Fig. 5C is used.
5 is pulled up by the cylinder 66 to the position shown by the dashed line. Then, the cylinder 68 of the new filter medium magazine 67 located directly above the new filter medium receiver 65 moves the stopper 71 backward, and the new filter medium 4 supported by this stopper 71 is moved back.
4 onto the new filter medium receiver 65.

Next, the filter medium clip 62 grips the new filter medium 44, and at the same time, the new filter medium receiver 65 is returned to its original position as shown by the solid line. Then, the cylinder 64 operates, and the filter medium clip 62 holding the filter medium 44 therebetween is pressed and inserted into the outer cylinder 55. When the filter medium 44 is inserted into the outer cylinder 55, the filter medium clip 62
is opened, and the filter medium clip 62 is retracted by the cylinder 64 while leaving the filter medium 44 in the outer cylinder 55.

Thereafter, when the stopper 71 returns to the original position shown in FIG. 5C, the stopper 73 is retracted by the cylinder 72, and the plurality of new filter media 44 supported by the stopper 73 fall to the position of the stopper 71. .

Subsequently, the stopper 73 returns to its original position, and preparation for the next supply is completed.

When a new filter medium 44 is loaded into the outer cylinder 55, the cylinder 53 and crank 54 shown in FIG. Thereafter, the solenoid valves 51 and 52 are closed, and the solenoid valve 46
．． 47 will be released.

The replacement of the filter medium 44 is completed by the above operations, and these operations are completed within one minute.

Although most of the impurities in the wastewater have been removed through the treatment up to the microfilter 43, it still contains a small amount of electrolyte. Therefore, if the water to be recycled is required to be deionized pure water, the treated water after being filtered by the precision filter 43 is sent to either the ion exchanger 74a or 74b.

The treated water from the ion exchanger 74a or 74b is
It is sent to the pure water tank 75 as pure water having an electrical conductivity of ~2 μS/cm, but the ion exchanger 74a or 74
If the ion exchange resin b deteriorates, the electrical conductivity of deionized water increases.

For this purpose, an electrical conductivity meter 76 is installed on the population side of the pure water tank 75, and when the indicated value of this electrical conductivity meter 76 exceeds the set value, the electrical conductivity meter 76 installed on the population side of the ion exchangers 74a and 74b is activated. Among the electromagnetic valves 77a and 77b, the one that is open is closed, and the one that is closed is opened to continue deionization.

Note that there is some deviation in the amount of water sent to the pure water tank 75, so this pure water tank 75 needs to have a capacity of at least 1xl, and if there is room in the overall size of the device, more It may have a large capacity. In addition, if deionization is not necessary, the filtered water from the precision filter 43 is transferred to the pure water tank 7.
Enter directly into 5.

The deionized pure water in the pure water tank 75 may contain fragments of ion exchange resin.

For this purpose, the water pumped from the pure water tank 75 by the pump 81 is transferred to the filter 8 having a filter medium of 100 μm or more.
2a or 82b.

These filters 82a, 82b and the above-mentioned filter 'la
, 2b, pressure gauges 83 and 84 are installed on the population side, respectively. When the indicated values of these pressure gauges 83 and 84 exceed the set values due to clogging of the filter media, the solenoid valves 85a to 85a installed at the inlet and outlet sides of the filters 82a and 82b and the filters 2a and 2b are activated. 85d and 86a,
Among the filters 86b, those that are open are closed and those that are closed are opened, so that the deteriorated filter medium is replaced during this time.

When replacing the filter medium etc. in this way, the filter 82a
, 82b, 2a, 2b, etc., and the filter medium is replaced after closing these manual valves.

However, these filters 82a, 82b and filters 2a, 2
Switching as in b can be performed only when the filter medium does not become clogged even after continuous use for 24 hours or more. If the life of the filter medium is less than 24 hours, it is necessary to automatically replace the filter medium as in the precision filter 43 described above.

The water filtered by the filter 82a or 82b is circulated to the wastewater discharge source 1 at a flow rate of exactly xN/min by the constant flow valve 87. However, if deionization is not necessary, the water from the precision filter 43 stored in the pure water tank 75 is circulated to the wastewater discharge source 1 through the constant flow valve 87.

By the way, the amount of water circulated to the wastewater discharge source 1 through the constant flow valve 87 needs to be exactly X27 minutes. However, the amount of wastewater passing through the device of this embodiment is not necessarily the predetermined amount of water x17 minutes, and there is some deviation depending on the wastewater discharge source and the function of the equipment in the device.

Therefore, in order to alleviate this deviation, in the apparatus of this embodiment, the capacity of the waste water tank 3, the treated water tank 37, and the pure tank 75 is set to at least about 2xl as described above, and the water level gauges 91.92. 93 are installed and operated as follows.

That is, first, when the water level of the water level gauge 91 exceeds the upper limit, a warning is issued to the wastewater discharge source 1, and the discharge amount of wastewater can be determined by x minutes. Moreover, when the water level of the water level gauge 91 falls below the lower limit, the pump 4 is stopped to stop liquid delivery to the electrolytic cells 6a and 6b, and the power to these electrolytic cells 6a and 5b is cut off.

After that, when waste water is supplied and the water level of the water level gauge 91 exceeds the lower limit, the pump 4 is started one minute later, and the electrolytic cells 6a and 5b are powered on.

When the water level of the water level gauge 92 exceeds the upper limit, the pump 4 is stopped and the power to the electrolytic cells 6a and 6b is cut off. Moreover, when the water level of the water level gauge 92 falls below the lower limit, the pump 41 is stopped. At that time, if the water level of the water level gauge 91 is also below the lower limit, the solenoid valve 94 is released and the predetermined water tank 37 is replenished with clean water.

When the water level of the water level gauge 93 exceeds the upper limit, the pump 41 is stopped, and when it falls below the lower limit, the pump 81 is stopped.

Further, in the device according to this embodiment, the final constant flow valve 87 adjusts the flow rate to X67 minutes, but the intermediate constant flow valves 5 and 42 are used to compensate for the amount of water during stoppage due to replacement of the filter medium 44, etc. The flow rate was adjusted to ((X+α)6/min) as described above.

Although the present invention has been explained above based on one embodiment, it is applicable not only to a device for circulating water as in this embodiment, but also to a device for purifying and using underground water, river water, etc. The invention can be applied.

Effects of the Invention As described above, in the device for coagulating impurities in a liquid according to the present invention, impurities in the liquid are adsorbed and coagulated by the metal hydroxide forming the electrode, so that unnecessary ions are generated. Even in liquids with low electrical conductivity, impurities can be aggregated without reducing their purity.

In addition, the amount of metal hydroxide produced can be controlled by controlling the current density in the liquid, suppressing the production of metal hydroxide in excess of the required amount and preventing other substances from adhering to impurities. It can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an embodiment of the present invention;
Figure 2 is a partially cutaway perspective view of the electrolytic cell shown in Figure 1, Figure 3 is a vertical sectional view of the flotation tank shown in Figure 1, and Figures 4 and 5 are the parts shown in Figure 1. 3A and 3B are side views showing a method for automatically replacing filter media of a precision filter. In addition, in the symbols used in the drawings, 5a, 5b-.
------・--1----Electrolytic cell 13.14--・--
------1-----It is an electrode plate.

Claims (1)

[Claims] 1. An electrolytic cell having an electrode made of a metal that is easily dissolved by electrolysis, and applying a voltage to the electrode to obtain a predetermined current density in a liquid in the electrolytic cell. A device for coagulating impurities in a liquid, comprising a constant current device for coagulating impurities in the liquid using the metal hydroxide. 2. The device according to claim 1, further comprising a polarity inverter that inverts the electrical polarity of the electrode at predetermined time intervals. 3. A plurality of electrolytic cells having the electrodes, a voltmeter for measuring the voltage, and an electrolytic cell to be used when the indicated value of the voltmeter exceeds a predetermined value among the plurality of electrolytic cells. 3. The device according to claim 1 or 2, each comprising a switching device that switches sequentially.