JP6990905B2 - Oil-water separation device and oil-water separation method - Google Patents

Description

The present invention relates to an apparatus and a method for separating an oil-water mixture into oil-water.

Generally, when the waste liquid discharged from a factory or the like is an oil-water mixed liquid, it is necessary to separate the oil-water mixture. Various oil-water separation methods have been proposed, but those using electrolysis are known. Typical methods for oil-water separation using electrolysis include those that adsorb oil to the bubbles of hydrogen (cathode side) and oxygen (anode side) generated from the electrodes and float them on the liquid surface, and water that precipitates on the electrode surface. It is known that oil-water separation is performed by trapping an oil component in a precipitate such as an oxide and recovering the floating / settling substance by a recovery means. These take advantage of the fact that the oil is hydrophobic and has weak conductivity in the mixed solution.

As described above, in the oil-water separation method using electrolysis, a method in which the polarities of a pair of electrodes are switched at predetermined time intervals is known (see, for example, Patent Document 1). Such polarity switching prevents the life of one electrode from becoming too fast and prolongs its life, and prevents the accumulation of precipitates such as hydroxides on one electrode and the deterioration of electrolytic performance. It is done for the purpose of doing.

Japanese Unexamined Patent Publication No. 5-253409

By the way, in such an oil-water separation method using electrolysis, when a voltage is applied to an electrode, a large amount of oil is attracted to the vicinity of the electrode immediately after electrolysis, and oil is laminated on the electrode surface, resulting in low conductivity. There is a problem that electrolysis may be hindered. Such a problem does not become a big problem, for example, when cleaning a machined product, because various substances become electrolytes in the cleaning drainage after painting. Even in the case described in Patent Document 1, it is understood that such a problem has not become apparent because NaCl is an electrolyte in bilge water. On the other hand, the wastewater washed with pure water after press working etc. contains almost no other electrolytes, and the electric power drops immediately after the voltage is applied, and the time required for oil-water separation becomes longer as a whole. It ends up.

Therefore, it is desired to enable oil-water separation that enables efficient oil-water separation by electrolysis, while suppressing a decrease in conductivity due to the rapid deposition of oil on the electrodes immediately after voltage application. These have problems to be solved by the present invention.

The present invention has been earnestly created to solve the above problems, and the invention of claim 1 is an electrolytic tank that accommodates and electrolyzes an oil-water mixed solution, and is arranged in the electrolytic tank to generate electricity. At least a pair of electrodes used for decomposition, a power source for applying a predetermined voltage to the electrodes, a control means for controlling the applied voltage, and a recovery means for recovering separated oil from the electrolytic tank. In the oil-water separation device for separating the oil-water mixture by electrolysis , the control means controls the control means so that the voltage applied to the electrodes changes to a predetermined applied voltage. The applied voltage controlled by the control means is switched between the anode and the cathode in the first half and the second half of the cycle in which the polarity is repeated, and in the period of each polarity, the pulse voltage for switching ON-OFF is applied. It is divided into a period, a constant voltage period to which a constant voltage is applied, and a zero voltage period without an applied voltage. It is an oil-water separation device characterized by being applied .
The invention according to claim 2 is characterized in that the pulse voltage applied during the pulse period is a square wave having a predetermined ON-OFF duty ratio, and is controlled so as to have a low frequency sequentially every predetermined period. The oil-water separation device according to claim 1.
The invention of claim 3 is the oil-water separation device according to claim 1 or 2, wherein the constant voltage period is divided so that the latter half becomes a high voltage .
The invention of claim 4 is an electrolytic tank that accommodates an oil-water mixed solution and electrolyzes it, at least a pair of electrodes arranged in the electrolytic tank and used for electrolysis, and a power source that applies a predetermined voltage to the electrodes. A control means for controlling the applied voltage, and a recovery means for recovering the separated oil component from the electrolytic tank, and the control means is used to separate the oil-water mixture by electrolysis. A method of controlling the voltage applied to the electrodes to a predetermined applied voltage, wherein the applied voltage controlled by the control means has an anode in the first half and the second half of the polarity in one repeated cycle. It has a process of switching to the cathode, and the process of each polarity period is in the order of the pulse period to which the ON-OFF switching pulse voltage is applied, the constant voltage period to which the constant voltage is applied, and the zero voltage period without the applied voltage. The oil-water separation method is characterized in that the process of the pulse period is controlled from the high frequency state after the start of voltage application to the process of applying the pulse voltage controlled to be sequentially low frequency. Is.

By doing so, immediately after the voltage is applied, a voltage with a high frequency pulse waveform is applied to suppress the adsorption of oil to the electrodes, and then the frequency is changed to a low frequency, so that oil and water due to electrolysis as a whole are obtained. The efficiency of separation will be improved.

It is (A) front view and (B) plan view which shows the outline of the oil-water separation apparatus. It is a schematic diagram showing the structure of an electrolytic cell, and shows (A) three pairs of electrodes, (B) one pair of electrodes, and (C) two pairs of electrodes. (A), (B) is a schematic diagram showing the structure of an electrolytic cell of a modified example in which the electrodes are cylindrical. It is a schematic diagram of the main part of the modification of the oil-water separation device, and is (A) a front view and (B) a plan view. It is a graph which shows the waveform of the voltage applied to an electrode. It is an enlarged view of the main part of FIG. It is a graph which shows the other example of the waveform of the voltage applied to an electrode, and is (A) a serrated waveform, and (B) a sinusoidal waveform. It is a graph which shows the current between electrodes at the time of voltage application, and is the superimposition of (A) with a pulse, (B) without a pulse, (C) with a pulse and without a pulse. (A) is a graph showing the correlation between the frequency of the applied voltage and the amount of oil adsorbed on the electrode, and (B) is a graph showing the correlation between the frequency of the applied voltage and the height of the bubbles. It is a graph which shows the correlation of (A) the duty ratio and the height of a bubble, and (B) the temperature of an oil-water mixture, and the height of a bubble.

Hereinafter, embodiments of the present invention will be described in detail. In the drawing, 1 is an oil-water separation device. The oil-water separation device 1 includes an electrolytic cell 3 that accommodates and electrolyzes a drainage oil-water mixed solution 101, an electrode 4 arranged in the electrolytic cell 3, and a power supply unit 5 that is a power source that applies a voltage to the electrode 4. I have. In the power supply unit 5, the voltage applied to the electrode 4 is controlled by the control means 6. Then, the oil-water separation device 1 performs oil-water separation by trapping oil in precipitates such as bubbles and hydroxides generated from the electrode 4 and floating it by applying a voltage, and adsorbing the floating oil. A collection means 7 for collecting the object 102 is further provided. The recovery means 7 has a recovery tank 7a that separates and recovers the oil adsorbent 102 from the electrolytic cell 3. The oil-water separation device 1 further includes a liquid-filling tank 8 provided with a liquid-filling port 8a for allowing the oil-water mixing liquid 101 to flow into the oil-water separating device 1, and a liquid-filling tank 8 including a warmer 9a as a heating means. Next to 8, the heating tank 9 through which the oil-water mixture liquid passes, and the drainage tank 10 provided with the drainage port 10a for discharging the water from which the oil and water are separated from the electrolytic cell are provided.

The oil-water mixed solution 101 may be one in which oil is adsorbed on the electrode immediately after the voltage is applied by the conventional separation method, such as drainage washed with pure water after press processing of a machine, but the present invention is not limited to this. Any type is acceptable as long as it is trapped by bubbles generated by electrolysis and becomes an oil adsorbent 102 and can be separated into oil and water.

Next, each of the liquid inlet tank 8, the heating tank 9, the electrolytic cell 3, the drainage tank 10, and the recovery tank 7a provided in the oil / water separation device 1, the oil / water mixed liquid 101, and the oil adsorbent containing the separated oil content. 102, the movement route of the drainage 103 from which the oil component is separated will be described. The liquid filling tank 8 is provided with a liquid filling port 8a at the bottom for allowing the oil-water mixed liquid 101 to flow in, and is separated from the heating tank 9 by a partition wall 8b. The upper end of the partition wall 8b is open, and the oil-water mixture 101 moves from the liquid inlet tank 8 to the heating tank 9 by overcoming the upper end.

The heating tank 9 is provided with a warmer 9a for heating the oil-water mixed liquid 101. The warmer 9a is a heating means for heating the oil-water mixed solution 101 to a predetermined temperature during electrolysis, and a known one can be appropriately adopted. The processing power due to electrolysis changes depending on the temperature of the oil-water mixture 101, and the predetermined temperature is preferably about 45 to 55 ° C. The improvement of the processing power by heating is shown in FIG. 10 (B). The heating tank 9 and the electrolytic cell 3 are separated by a partition wall 9b. An insertion port 9c for moving the oil-water mixed liquid 101 to the electrolytic cell 3 is provided in the lower part of the partition wall 9b.

The electrolytic cell 3 is separated from the recovery tank 7a and the drainage tank 10 by partition walls 3a and 3b having open upper ends, respectively. The oil-water mixture 101 that has moved from the insertion port 9c to the electrolytic cell 3 is separated into oil and water by electrolysis as described later, and the oil is trapped by bubbles or the like and floats on the liquid surface as an oil adsorbent 102. Then, the floating oil adsorbent 102 is moved to the recovery tank 7a beyond the upper end of the partition wall 3a by the recovery means 7 described later, and is filtered and removed by a filtration means (not shown). On the other hand, the drainage from which the oil content has been removed moves beyond the upper end of the partition wall 3b to the drainage tank 10, and is discharged to the outside from the drainage port 10a.

Subsequently, the structure related to electrolysis in the electrolytic cell 3 will be described. In the present embodiment, three pairs of flat plate-shaped electrodes 4 are arranged in the electrolytic cell 3. In the three pairs of electrodes 4, the first electrode 4a and the second electrode 4b are alternately arranged so as to face each other. In each of the electrodes 4a and 4b, during the cycle A of the applied voltage described later, the _first electrode 4a becomes the anode and the second electrode 4b becomes the cathode in the first half period B1, and the polarities are switched in the _second half period B2, so that the first electrode 4a Is the cathode and the second electrode 4b is the anode.

In the present embodiment, both the first electrode 4a and the second electrode are magnesium electrodes made of magnesium. By using all the electrodes 4 as magnesium electrodes, the processing power for oil-water separation is improved. Further, the first electrode 4a may be a magnesium electrode made of a magnesium material, and the second electrode 4b may be an aluminum electrode made of an aluminum material. By making the electrode 4 have the magnesium electrode and the aluminum electrode facing each other in this way, the filtration rate is improved when the oil adsorbent 102 recovered by the recovery means 7 is filtered by a filtration means (not shown). The electrode 4 is preferably made of these materials, but is not limited to these, and can be selected from various electrode materials.

The electrodes 4 in the present embodiment are three pairs of electrodes as shown in FIG. 2 (A), but the number of electrodes can be changed as appropriate, and a pair of electrodes or a pair of electrodes as shown in FIG. 2 (B) can be used. As shown in FIG. 2C, two pairs of electrodes may be used. Further, the electrode 4 is not limited to a flat plate shape, and may have a cylindrical shape as shown in FIG. In this case, the first electrode 4a and the second electrode 4b are alternately arranged from the center in the radial direction to form a cylindrical shape having a longer diameter toward the outer side in the radial direction. In FIG. 3, the central first electrode 4a has a solid cylindrical shape. In the case of FIG. 3B, the second electrode 4b, which is the electrode 4 arranged on the outermost circumference, is also used as the wall surface of the electrolytic cell 3.

An insulator 11 is attached to a non-opposing surface 4c that does not face the other electrodes 4 in the first electrode 4a and the second electrode 4b arranged at the outer ends in the stacking direction of the electrodes. By energizing only the facing surface of the electrode 4, the insulator 11 promotes efficient electrolysis and prevents the oil adsorbent 102 from diffusing. When the cylindrical electrode 4 is used as shown in FIG. 3A, the cylindrical insulator 11 may be attached to the non-opposing surface 4c of the outermost electrode 4. As shown in FIG. 3B, when the second electrode 4b, which is the electrode 4 arranged on the outermost circumference, is also used on the wall surface of the electrolytic cell 3, the second electrode 4b on the outermost circumference is used as another tank, member, or the like. It is assumed that the insulator 11 is attached to the lower part of the outer circumference so as not to come into contact with.

Further, an ultrasonic oscillator 12 for oscillating ultrasonic waves is provided in the lower part of the electrolytic cell 3. The ultrasonic oscillator 12 vibrates the oil, precipitates, and oil adsorbent 102 adhering to the surface of the electrode 4 by oscillating ultrasonic waves toward the electrode 4, and separates the oil adsorbent 102 from the electrode 4. Can be adopted.

Next, the control means 6 for controlling the voltage applied to the electrode 4 will be described. The control means 6 can appropriately change the voltage applied to the electrode 4 according to the elapsed time. The change in the applied voltage due to the control means in the present embodiment is schematically shown in the graphs of FIGS. 5 and 6, and this change will be described below.

In the present embodiment, the applied voltage is 130 seconds as one cycle cycle A, the _first half period B1 where the first electrode 4a becomes the anode for the first 65 seconds, and the second electrode 4b becomes the anode for the latter 65 seconds. It is set to B ₂ in the latter half period. Therefore, the polarity switching time in this embodiment is 65 seconds. Then, in the first half period B ₁ and the second half period B ₂ , the waveform W of the applied voltage is controlled so as to have a symmetrical shape in which positive and negative are alternated. Further, the voltage applied during the first half period B ₁ is 0 V or more, and the applied voltage during the second half period B ₂ is 0 V or less. By switching the polarity in this way, it is possible to prevent one of the electrodes 4 from being consumed, so that it is possible to prolong the life of the electrode 4 and prevent oil from being adsorbed on one of the electrodes. .. The first half period B ₁ is divided into a pulse period C for 20 seconds in which a pulsed voltage is applied, a constant voltage period D for 40 seconds in which a constant voltage is applied, and a zero potential period E for 5 seconds in which no voltage is applied. .. The time of the cycle A, the polarity switching time, and the length of each period are not limited to the above time, but can be appropriately set including other periods described later. For example, the length of the cycle A can be about 0.1 to 200 seconds.

In the pulse period C, the applied voltage is controlled to be 90 V and a pulsed voltage having a duty ratio of 80% (ON: OFF = 8: 2) as a square wave is applied, and the frequency f (Hz) is applied. It is controlled so that the frequency becomes low sequentially from the start. Specifically, the pulse period C is the first pulse period C ₁ at f = 10 Hz, the second pulse period C ₂ at f = 5 Hz, the third pulse period C ₃ at f = 2.5 Hz, and f every 5 seconds. It is subdivided into the _fourth pulse period C4 of = 1.25 (see FIG. 6). Then, the frequency f = 10 Hz of the first pulse period C ₁ corresponds to the initial frequency f ₀ , and the voltage of the above waveform is applied to the electrode 4 during the first pulse period C ₁ to be the first pulse. Corresponds to the application step. Further, during the second to _fourth pulse periods _C2 to C4, a voltage having a pulse waveform whose frequency is lower than the initial frequency _f0 is applied, which corresponds to the second pulse application step. In this way, by converting the waveform W into a high-frequency pulse wave immediately after the voltage is applied, it is possible to prevent the oil content from rapidly laminating on the surface of the electrode 4 immediately after the voltage is applied, resulting in a decrease in conductivity and a decrease in processing power. can do. Then, by gradually lowering the frequency, the processing power will be improved.

The changes in the amount of oil adsorbed and the processing power due to the change in the frequency f are shown in FIG. FIG. 9A shows a change in the amount of oil adsorbed on the electrode 4 (mg) due to a change in frequency when a pulsed square wave voltage having a duty ratio of 80% is applied at 70 V for 3 minutes. be. As is clear at first glance, it can be seen that the higher the frequency, the smaller the amount of oil adsorbed on the electrode 4. Further, FIG. 9B shows a change in the height of bubbles generated on the liquid surface due to a change in frequency when a pulsed square wave voltage having a duty ratio of 80% is applied at 70 V for 15 minutes. Is. Since the bubbles are trapped with oil, it can be said that the height of the oil indicates the processing power of oil-water separation. As is clear from FIG. 9B, the higher the frequency, the lower the height of the bubbles. Therefore, as a simple processing force, it is preferable to use a pulse wave having a low frequency or a constant voltage. I understand.

Based on these findings, it is necessary to increase the frequency f in order to suppress the adsorption of oil to the electrode 4, but it is necessary to decrease the frequency f in order to improve the processing power as a whole. I can say. Since the adsorption of oil to the electrode 4 occurs rapidly immediately after the voltage is applied, in order to avoid this, the frequency f is increased immediately after the voltage is applied to suppress the amount of oil adsorbed, and then the frequency f is decreased. By doing so, the processing power will be increased and the processing power as a whole will be improved.

In the present embodiment, the applied voltage is divided into the _first to _fourth pulse periods C1 to C4 in the pulse period C, and the frequency f is controlled to be gradually lowered for each period. The frequency f may be controlled to be lowered as a linear function, for example, instead of the target. Further, even when the stepwise change is controlled, the length of each period does not have to be constant, and a change such as lengthening the first pulse period may be added as necessary.

After the pulse period C, there is a constant voltage period D in which a constant voltage is applied, and the constant voltage period D is a first constant voltage period D ₁ and a first constant voltage period D ₁ in which a constant voltage of 90 V is applied for 20 seconds. It is divided into a _second constant voltage period D2 in which a higher constant voltage of 100 V is applied for 20 seconds. The second constant voltage period D ₂ is provided in order to promote the detachment of the oil adsorbent 102 such as bubbles generated in the electrode 4 from the electrode 4 by increasing the applied voltage before the polarity is switched.

After the constant voltage period D, there is a zero potential period E for 5 seconds in which no voltage is applied. Bubbles are generated in the electrode 4 by electrolysis, but these bubbles are minute at the beginning of generation, and the bubbles gather together with the passage of time to become large bubbles. Since the floating speed of small bubbles at the beginning of generation is slow, by providing a zero potential period E, the bubbles generated in the vicinity of the electrode 4 become a certain size, and oil can be trapped and floated. Consideration is given so that bubbles generated before the switching of the case do not remain on the electrode 4.

The above is the description of each period in the first half period B ₁ , and in the second half period B ₂ , since the waveform is symmetrical with the polarity of the electrode 4 switched, detailed description thereof will be omitted. The waveform W of the applied voltage of the present embodiment is a cycle A composed of the first half period B ₁ and the second half period B ₂ continuously repeated.

The recovery means 7 is for physically separating oil and water by trapping the oil content generated from the electrode 4 and removing the oil adsorbent 102 floating on the liquid surface from the electrolytic cell 3. The recovery means 7 includes a recovery tank 7a for accumulating the oil adsorbent 102 recovered from the electrolytic cell 3, and an extruder 7b for pushing the oil adsorbent 102 on the liquid surface surface of the electrolytic cell 3 toward the recovery tank 7a. The extruder 7b has a wide shape so as to cover the range in which the oil adsorbent 102 floats on the liquid surface. Further, the extruder 7b is made of an insulating material such as a synthetic resin such as polyvinyl chloride resin or rubber, and the lower end thereof is slightly below the liquid level of the oil-water mixture 101 in the electrolytic cell 3 (for example, 1 to 5 mm). Degree) It is provided so as to sink. In this way, by making the extruder 7b made of an insulating material, even if the extruder 7b accidentally comes into contact with the electrode 4, there is no short circuit. Then, the oil adsorbent 102 recovered in the recovery tank 7a by the extruder 7b is filtered by a filtration means (not shown) and then treated as waste.

As the configuration of the collection means 7, an appropriate one can be adopted. For example, FIG. 4 shows an example of changing the configuration of the recovery means, which is provided with a roller 7c and an inclined plate 7d in order to move the oil adsorbent 102 to the recovery tank 7a. The roller 7c is a cylindrical rotating body that rotates upward from the liquid surface, and the oil adsorbent 102 on the liquid surface surface is moved to the roller 7c surface by rotation. The inclined plate 7d is a plate member arranged on the upper surface side of the roller 7c, and is inclined toward the recovery tank 7a in the axial direction of the roller 7c from the front to the rear in the rotation direction of the roller 7c. .. As a result, the oil adsorbent 102 rotated by the roller 7c and moved to the surface of the roller 7c is moved to the recovery tank along the inclination of the inclined plate 7d so that the oil adsorbent 102 can be separated from the electrolytic cell 3. It has become. Further, the recovery means 7 of the present embodiment targets the floating matter on the liquid surface surface, but when the precipitate trapped in the oil settles, the sediment is recovered below the electrolytic cell 3. It may be configured so that the floating matter and the sediment can be recovered respectively.

FIG. 8 is a graph showing that the processing power is improved by decomposing the oil-water mixture 101 with the oil-water separator 1 of the present embodiment as compared with the case where the voltage of the pulse waveform is not applied. Is. FIG. 8 is a graph comparing changes in the current generated between the electrodes 4 depending on the presence or absence of a pulse. As is clear from FIG. 8, when there is a pulse, the current between the electrodes 4 is higher than when there is no pulse, and the processing power for oil-water separation by electrolysis is higher. You can see that.

Although the present embodiment has been described above, the present invention is not limited to the specific configuration of the present embodiment. For example, various waveforms of the pulse voltage can be adopted. The waveform during the pulse period C does not have to be a square wave and may be a sawtooth wave or a sine wave, for example, as shown in FIG.

Further, in the present embodiment, the duty ratio of the pulse wave in the pulse period C is 80%, but the duty ratio is not limited to 80%. However, as shown in FIG. 10A, the higher the duty ratio, the higher the processing power, but on the other hand, when the duty ratio is high, the amount of oil adsorbed on the electrode 4 increases, so the duty ratio is changed. It is preferably about 80%. Further, the duty ratio may be changed for each period during the pulse period C, for example, 80% in the first pulse period C ₁ , 85% in the second pulse period C ₂ , and the third pulse period C ₃ . It may be gradually increased to 90%, 95% in the _fourth pulse period C4, and so on.

In the embodiment of the present invention configured as described above, the oil-water separation device 1 includes an electrolytic cell 3 that accommodates and electrolyzes an oil-water mixed solution 101 such as industrial wastewater, and is arranged in the electrolytic cell 3 to generate electricity. The electrolytic cell 3 contains an electrode 4 used for decomposition, a power supply unit 5 for applying a predetermined voltage to the electrode 4, a control means 6 for controlling the applied voltage, and an oil adsorbent 102 to which the separated oil is adsorbed. The collection means 7 for collecting from is provided. The control means 6 controls the voltage applied to the electrode 4 by the power supply unit 5 so as to be a voltage having a pulse waveform having a predetermined frequency f (Hz), and the first pulse period immediately after the start of application of the voltage. A power supply is applied so that a pulse voltage of a square wave having an initial frequency f ₀ is applied to C ₁ , and a pulse voltage having a frequency lower than the initial frequency f ₀ is applied in the subsequent second to fourth pulse periods C ₂ to C ₄ . It is set to control the unit 5. In this way, by applying a high-frequency pulse waveform voltage in the first pulse period C1, oil is rapidly adsorbed on the electrode 4, while the subsequent second to fourth pulse periods _C2 to _C4 are suppressed. Then, by gradually applying a voltage having a low frequency pulse waveform, the processing efficiency is improved, so that the efficiency of oil-water separation by electrolysis is improved as a whole.

Further, the control means 6 reverses the positive and negative of the pulse voltage applied by the power supply unit 5 between the first half period B ₁ and the second half period B ₂ every time a predetermined polarity switching time elapses, so that the polarity of the electrode 4 is switched. It is set. This makes it possible to extend the life of the electrode and separate oil and water by efficient electrolysis. Further, the control means 6 controls the power supply unit 5 so as to provide a zero potential section E in which no voltage is applied to the electrode 4 at the end of the first half period B ₁ and the second half period B ₂ immediately before the polarity of the electrode 4 is switched. .. As a result, the oil adsorbent 102 such as bubbles generated on the electrode 4 can be floated during the zero potential period E, so that it is possible to suppress a decrease in the processing power after the polarity is switched. Furthermore, since the pulse voltage waveforms are symmetrical between the first half period B ₁ and the second half period B ₂ , the oil and water separation by electrolysis as a whole is suppressed while suppressing the rapid adsorption of oil to the electrodes even after the polarity is switched. The efficiency is to be further improved.

Further, the waveform W of the pulse voltage is optimized by being a square wave having a duty ratio of 80%, and the efficiency of oil-water separation is increased. In addition, since the oil-water mixture 102 in the electrolytic cell 3 is heated by the warmer 9a and set to a temperature of 45 to 55 ° C., the efficiency of oil-water separation is improved.

When the oil-water mixture 102 is electrolyzed and separated into oil-water by such an oil-water separation device 1, a first pulse in which a pulse voltage having an initial frequency _f0 is applied immediately after the start of application of a voltage from the power supply unit 5 to the electrode 4. The application step is performed in the first pulse period C ₁ , and in the subsequent second to fourth pulse periods C ₂ to C ₄ , the second pulse application step of applying a pulse voltage lower than the initial frequency f ₀ is performed. ..

The present invention can be used in a field relating to oil-water separation of an oil-water mixture such as drainage.

1 Oil-water separator 3 Electrolytic cell 4 Electrode 4a 1st electrode 4b 2nd electrode 5 Power supply unit 6 Control means 7 Recovery means 9a Heater 101 Oil-water mixture 102 Oil adsorbent 103 Drainage B _{1 First} half period B _{2 Second} half period C pulse Period D Constant voltage period E Zero potential period f Frequency f ₀ Initial frequency

Claims (4)

An electrolytic cell that houses an oil-water mixture and electrolyzes it,
At least a pair of electrodes arranged in the electrolytic cell and used for electrolysis,
A power supply that applies a predetermined voltage to the electrodes, and
A control means for controlling the applied voltage and
A recovery means for recovering the separated oil from the electrolytic cell,
In the oil-water separation device for separating the oil-water mixture by electrolysis.
In controlling the control means so that the voltage applied to the electrodes changes to a predetermined applied voltage, the control is performed.
The applied voltage controlled by the control means is switched between the anode and the cathode in the first half and the second half in the period of one repeated cycle.
The period of each polarity is divided into the pulse period in which the pulse voltage of ON-OFF switching is applied, the constant voltage period in which the constant voltage is applied, and the zero voltage period in which there is no applied voltage.
An oil-water separation device characterized in that a pulse voltage controlled so as to sequentially decrease from a high frequency state after the start of application of a voltage to a low frequency is applied during the pulse period . The oil-water according to claim 1 , wherein the pulse voltage applied during the pulse period is a square wave having a predetermined ON-OFF duty ratio and is controlled so as to have a low frequency sequentially every predetermined period. Separator. The oil-water separation device according to claim 1 or 2, wherein the constant voltage period is divided so that the latter half becomes a high voltage . An electrolytic cell that houses an oil-water mixture and electrolyzes it,
At least a pair of electrodes arranged in the electrolytic cell and used for electrolysis,
A power supply that applies a predetermined voltage to the electrodes, and
A control means for controlling the applied voltage and
A recovery means for recovering the separated oil from the electrolytic cell,
Equipped with
The control means is a method of controlling the voltage applied to the electrode to separate the oil-water mixture by electrolysis so that the voltage applied to the electrode becomes a predetermined applied voltage.
The applied voltage controlled by the control means has a step in which the polarity is switched between the anode and the cathode in the first half and the second half in one repeated cycle.
The process of each polarity period is divided into a pulse period in which an ON-OFF switching pulse voltage is applied, a constant voltage period in which a constant voltage is applied, and a zero voltage period in which there is no applied voltage.
The oil-water separation method is characterized in that the step of the pulse period is controlled to a step of applying a pulse voltage controlled so as to sequentially decrease from a high frequency state after the start of application of the voltage to a low frequency .

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