JP4815158B2 - Oil-water separation method - Google Patents

Description

  The present invention relates to an oil-water separation method and an oil-water separator, and in particular, supplies air to a liquid to be treated and pressurizes it with a pump to dissolve the air in the liquid to be treated, and the air dissolved from the lower part of the treatment tank is covered as bubbles. The present invention relates to an oil-water separation method and an oil-water separation device by a levitation separation method in which an oil component contained in a liquid to be treated is floated together with bubbles in a treatment tank by blowing it together with the treatment liquid, thereby separating the liquid to be treated from water and oil.

  As described in Patent Document 1 below, as a separation apparatus based on the levitation separation method, gas suction means is provided in the liquid suction port of the vortex pump, and air is dissolved in the liquid to be processed in the pressurization process of the vortex pump. Some gas bubbles are generated in the liquid to be processed in the processing tank by performing (gas-liquid mixing and dissolution) and jetting and decompressing from the nozzle in the processing tank.

Japanese Patent Laid-Open No. 2003-236305

  In the above prior art, when the hydrophobicity of the oil itself is high, the fine bubbles generated in the treatment tank and the oil component are combined, and the oil component floats together with the bubbles and can be separated into oil and water. However, when the hydrophobicity of the oil itself is low, the bonding between the microbubbles and the oil does not proceed sufficiently, and the oil-water separation cannot be performed.

  As a result, water (drain) containing mineral oil such as reciprocating compressor lubricating oil or special screw compressor lubricating oil may not be able to be separated to 5 mg / L, which is the drainage standard for mineral oil.

  Therefore, an object of the present invention is to provide an oil / water separation method and an oil / water separation device capable of performing oil-water separation at high speed up to a drainage standard for water containing oil having low hydrophobicity.

The oil-water separation method of the present invention that achieves the above object is characterized by supplying air to the liquid to be treated, pressurizing with a pump to dissolve the air in the liquid to be treated, and dissolving the air dissolved from the lower part of the treatment tank. In the oil-water separation method in which the oil contained in the liquid to be treated is floated together with the bubbles in the treatment tank by blowing out the bubbles together with the liquid to be treated, and the liquid to be treated is separated into water and oil. Ri near supplying bubbles into the liquid to be treated by mixing at least one of sodium hydroxide, in particular, is to mix the sodium hydroxide later than at least one of calcium chloride and magnesium chloride.

  In addition, the oil-water separation method of the present invention that achieves the above object is characterized by separately mixing at least one of calcium chloride and magnesium chloride and sodium hydroxide into a liquid to be treated containing an oil component having low hydrophobicity. .

  According to the present invention, the oil in the liquid to be treated is agglomerated by calcium chloride (CaCl2) or magnesium chloride (MgCl2), and this aggregation is promoted by sodium hydroxide (NaOH), and the dispersed fine oil is bonded. As a result of the body becoming larger in diameter, not only will it rise easily, but it will also become easier to adsorb with fine bubbles produced with air that has been pressure-dissolved with a pump, making it easier to float, and oil-water separation proceeds at high speed. .

  Calcium chloride and magnesium chloride are the main components of bittern used in the production of tofu, and are used in foods, and their aqueous solutions are drained with sodium hydroxide in a form diluted with the liquid to be treated. Will not pollute. That is, even water containing oil with low hydrophobicity can be separated at high speed to the drainage standard, the oil can be recovered, and the water can be discarded as it is.

  Further, according to the present invention, the concentration of sodium hydroxide aqueous solution is increased by reducing the addition amount of calcium chloride and magnesium chloride which are corrosive to metals, maintaining the oil aggregation effect as a whole, By increasing the pH value, the corrosiveness of calcium chloride and magnesium chloride is reduced, making it difficult for various metal members such as treatment tanks and pipes to corrode, and by making the liquid to be treated alkaline, Separation can be promoted.

The oil-water separator according to this embodiment is characterized in that air is supplied to the liquid to be processed and pressurized with a pump to dissolve the air in the liquid to be processed, and the air dissolved from the lower part of the processing tank is covered as bubbles. In an oil / water separator that blows off the oil contained in the liquid to be treated in the treatment tank together with bubbles by blowing it together with the treatment liquid, and separates the water and the oil of the liquid to be treated in the aqueous solution of calcium chloride on the suction side of the pump A pipe for supplying at least one of an aqueous solution of magnesium chloride and a pipe for supplying an aqueous solution of sodium hydroxide, and further providing a pressure regulating valve on the suction side of the pump, and adjusting the opening of the pressure regulating valve Calcium chloride aqueous solution and magnesium chloride water with the suction pressure lower than the atmospheric pressure and the differential pressure between the atmospheric pressure and the pump suction pressure as the driving force It is to be mixed to said processing solution separately at least one of sodium hydroxide solution of a liquid.
In addition, the feature is that by supplying air to the liquid to be processed and pressurizing with a pump to dissolve the air in the liquid to be processed, the air dissolved from the lower part of the processing tank is blown out together with the liquid to be processed as bubbles. In the oil-water separator that floats the oil contained in the liquid to be treated together with bubbles in the treatment tank and separates the water and the oil in the liquid to be treated, an aqueous calcium chloride solution and an aqueous magnesium chloride solution are used as the liquid to be treated in the treatment tank. This is because a pump for separately metering at least one and an aqueous sodium hydroxide solution is provided.
Furthermore, the feature is that air is supplied to the liquid to be processed and pressurized with a pump to dissolve the air in the liquid to be processed, and the air dissolved from the lower part of the processing tank is blown out together with the liquid to be processed as bubbles. In the oil-water separator that floats the oil contained in the liquid to be treated together with bubbles in the treatment tank and separates the water and the oil in the liquid to be treated, at least one of an aqueous calcium chloride solution and an aqueous magnesium chloride solution and an aqueous sodium hydroxide solution Tanks to be stored are provided at locations higher than the surface of the liquid to be treated in the treatment tank, valves are provided in pipes that lead each aqueous solution from the tanks to the treatment tank, and each valve is opened to cover each aqueous solution by gravity. It is to be mixed with the treatment liquid.
Hereinafter, an oil-water separator according to an embodiment of the present invention will be described.

  The oil-water separator 10 shown in FIG. 1 is used as an example for treating drain discharged from an air compressor.

  In FIG. 1, a treatment tank 11 stores a liquid to be treated in the tank and separates oil and water into the separation tank (described as a treatment tank in the claims) 81 and a floating oil that collects oil separated and floated by the separation section 81. There is a receiving portion 83, and a shielding plate 12 that separates both portions 81 and 83 is provided. In the lower part of the side wall of the processing tank 11, the large bubble separating unit 13 is connected to the separating unit 81.

  The pipe 30 attached to the bottom of the separation part 81 in the treatment tank 11 is connected to the circulation pump 31 via the valve 36 and the pipe 32, and the outlet side pipe 37 of the circulation pump 31 is installed in the large bubble separation part 13. It is connected to the nozzle 33. One end of an air supply pipe 41 having a valve 42 is connected to the pipe 32, and the other end of the air supply pipe 41 is open to the atmosphere.

  The pipes 30, 32, and 37 constitute an external circulation system of the liquid to be processed in the separation unit 81. As will be described later, air is sucked and pressurized from the air supply pipe 41 by the operation of the circulation pump 31. The liquid to be treated which is dissolved therein and in which air is dissolved is ejected from the nozzle 33.

  As an example of the circulation pump 31, a vortex pump is used. Although not shown, a gauge for measuring the pressure (water pressure) of the liquid to be treated is provided at the outlet of the circulation pump 31.

  The nozzle 33 is provided on the side wall of the lower part of the separation unit 81 in the processing tank 11 together with the large bubble separation unit 13, so that the large bubble that may be ejected from the nozzle 33 is not sent to the separation unit 81 in the large bubble separation unit 13. The discharge pipe 14 is provided, and the discharge port of the discharge pipe 14 is positioned above the separation portion 81.

  A supply pipe 23 having a supply pump 21 and a valve 22 and constituting a supply system for an unprocessed liquid is connected to the pipe 32. The supply pipe 23 may be connected to the lower part of the separation unit 81 to supply untreated liquid to the separation unit 81.

  A pipe 72 from a sodium hydroxide (NaOH) aqueous solution tank 71 is connected to the pipe 32 via a valve 77. A pipe 92 from a calcium chloride (CaCl 2) aqueous solution tank 91 is connected to the pipe 32 via a valve 97.

  A discharge pipe 51 for discharging the processed liquid to be processed is provided at the upper part of the separation unit 81, and the discharge pipe 51 is lifted from a connection part (tube seat) with the separation part 81, and its downstream is connected to the separation part 81. The pipe is piped to a position lower than the connecting portion, and has a valve 52 in the middle thereof. The highest position of the discharge pipe 51 is set lower than the highest position of the shielding plate 12 of the treatment tank 11 to have a positional difference D1.

  Therefore, when supplying and storing the liquid to be processed in the separation unit 81, if the valve 52 is opened, the liquid to be processed flows out of the discharge pipe 51, and the liquid surface 61 to be processed in the separation part 81 is discharged from the discharge pipe. Regulated at the highest of 51. When the valve 52 is closed and the liquid to be treated is supplied into the separation tank 81, the liquid surface 61 to be treated rises from the highest level of the discharge pipe 51, so that the discharge pipe 51 is covered by opening and closing the valve 52. It has the function of discharging the processing liquid and adjusting the water level.

  The pipe 53 provided in the discharge pipe 51 is open to the atmosphere so that it is not drained below the highest horizontal plane of the discharge pipe 51 by the siphon effect. In addition, a floating oil liquid level 62 of the floating oil that has been raised by the oil-water separation is formed on the top of the liquid surface 61 to be treated.

  A partition plate 15 is provided to prevent fine bubbles and oil particles rising in the separation unit 81 from entering the treated liquid that has flowed out of the separation unit 81 through the discharge pipe 51, and the pocket-like suction unit 82 is provided. Is formed. That is, the separation unit 81 is configured such that the lowering speed of the processing liquid in the suction part 82 determined by the outflow amount of the processing liquid in the discharge pipe 51 and the inlet area of the suction part 82 is slower than the rising speed of the bubbles. The fine bubbles and the oil particles that are moving up the flow do not flow into the suction portion 82 and flow out of the discharge pipe 51.

  The highest position of the partition plate 15 is lower than the highest position of the discharge pipe 51, that is, the liquid surface 61 to be processed when the valve 52 is opened, so as to have a positional difference D2. Further, the highest position of the partition plate 15 is set higher than the connection portion (tube seat) with the separation portion 81 of the discharge pipe 51 so as to have a positional difference D3.

  An oil discharge pipe 55 is provided at the bottom of the floating oil receiving portion 83 to discharge the waste oil 63 that flows over the shielding plate 12 from the separation portion 81 and flows in (overflows). Moreover, although not shown in figure, piping is provided outside from the bottom part of the processing tank 11, the valve | bulb is provided in the middle, and these are used when it is necessary to discharge | emit the liquid inside the separation part 81.

  The separation unit 81 is provided with a temperature measuring device 84 so that the temperature of the liquid to be processed in the separation unit 81 can be measured. Instead of the temperature measuring device 84, a temperature measuring device may be installed in the piping 37 from the piping 30 to the nozzle 33 via the circulation pump 31, and the temperature of the liquid to be processed may be measured.

Next, the operation of the oil / water separator shown in FIG. 1 will be described.
The drain discharged from the air compressor has a large drain flow rate and a low oil concentration in the drain when the absolute humidity is high (summer season). On the other hand, when the absolute humidity is low (winter and spring / autumn), the drain flow rate is small and the oil concentration in the drain is high. A continuous operation process is preferable when the absolute humidity is high (summer), and an intermittent operation process is preferable when the absolute humidity is low (winter and spring / autumn).

First, the continuous processing operation performed when the absolute humidity is high will be described.
As a preparation, the valve 52 is opened and the separation unit 81 of the treatment tank 11 is filled with fresh water or a treated liquid to be treated. When the treated liquid level 61 coincides with the highest level of the discharge pipe 51, the circulation pump 31 is operated. Let At this time, the valve 22 is closed and the supply pump 21 is stopped. The valves 36 and 42 are open.

  Next, the opening of the valve 36 is adjusted so that the inlet pressure of the circulation pump 31 (not shown) is lower than the atmospheric pressure. In the operation of the circulation pump 31, the fresh water or the treated liquid in the separation unit 81 is sucked through the pipes 30 and 32, and is pressurized and flows from the pipe 37 to the nozzle 33, so that the air supply pipe 41 side further becomes negative pressure, Dissolving air flows from the air supply pipe 41 and reaches the pipe 32.

  In the circulation pump 31, the air is divided and pressurized to be dissolved in fresh water or a processed liquid to be processed, but the air that cannot be completely dissolved flows as a large bubble to the nozzle 33 through the pipe 37. The to-be-treated liquid pressurized by the circulation pump 31 and the dissolved air are decompressed by being discharged from the nozzle 33 into the to-be-treated liquid of the separation unit 81, and the air dissolved in the water becomes fine bubbles. The amount of air dissolved in the liquid to be treated by the pressurization by the circulation pump 31 follows the Henry's law under the pressure, and the pressure applied to the fresh water flowing through the pipe 37 or the treated liquid to be treated and the pipe 37 The amount of dissolved air increases in proportion to the flowing flow rate. Moreover, the amount of dissolved air increases as the temperature of the fresh water flowing through the pipe 37 or the processed liquid to be processed is lower. In actual operation, the operation is performed so that the pressure and flow rate are constant.

  When operated in this way, the power of the circulation pump 31 becomes heat and is transmitted to the liquid to be treated, the liquid temperature rises, and the amount of dissolved air decreases. For this reason, the relationship between the flow rate of the liquid to be treated in the pipe 37, the liquid temperature of the liquid to be treated, the amount of pressure applied by the circulation pump 31 and the amount of dissolved air is obtained in advance, and air is supplied at the liquid temperature obtained by the temperature measuring device 84. The operation is performed by adjusting the valve 42 so that the amount of the air for dissolving flowing in from the pipe 41 becomes an amount in which the bubbles almost rise in the processing tank 11.

  As described above, the air dissolved in the liquid to be treated is decompressed by being discharged from the nozzle 33 and becomes bubbles, and floats in the separation unit 81. The amount of air dissolved is adjusted by the valve 42 so that the bubbles are discharged from the nozzle 33. A large bubble having a large diameter rises faster than a fine bubble because buoyancy works greatly. Fast ascent does not contribute to oil-water separation, disturbs the flow in the separation part 81, obstructs the contact of fine bubbles and oil, and may degrade the separation performance.

  Since it can be considered that large bubbles are generated due to the presence of air that has not been dissolved in the liquid to be treated even when the circulation pump 31 is pressurized, the amount of the dissolving air taken in from the air supply pipe 41 is controlled by the valve 42. Adjust so that excess air does not get in and keep large bubbles from rising continuously. The generated large bubbles are extracted to the discharge pipe 14 of the large bubble separating unit 13 so that the large bubbles that may be ejected from the nozzle 33 are not sent to the separating unit 81.

  While maintaining this operating state, the valve 22 is opened and the supply pump 21 is driven to operate the supply system of the liquid to be treated (drain), and the fresh water or the treated liquid being circulated in the external circulation system of the separation unit 11 is operated. An untreated liquid (drain) is mixed with the treatment liquid.

  Next, the valve 97 is opened, and a desired amount of calcium chloride aqueous solution is continuously supplied from the tank 91 through the pipe 92. Similarly, the valve 77 is opened, and a sodium hydroxide aqueous solution is continuously supplied from the tank 71 through the pipe 72.

  Then, the drain is ejected from the nozzle 33 together with the fine bubbles, and the oil component aggregated by the calcium chloride aqueous solution in the drain adheres to the fine bubbles and floats, and the oil component is separated from the liquid to be treated (water).

  At this time, the power of the supply pump 21 becomes heat, which is transferred to the mixed liquid to be treated, the temperature rises, and the amount of soluble air decreases. An excess bubble (large bubble) that cannot be dissolved by reducing is generated. As described above, surplus bubbles have a large bubble diameter and a high ascending speed, and flow turbulence occurs in the tank, and fine bubbles adhering to oil are separated to prevent oil-water separation.

  Therefore, as described above, the relationship between the liquid temperature and the amount of dissolved air is obtained in advance, and the amount of dissolving air to be introduced from the air supply pipe 41 at the liquid temperature obtained by the temperature measuring device 84 is generated in the processing tank 11 by bubbles. The valve 42 is readjusted so that the amount rises almost uniformly so as not to generate excess air so that the oil / water separation performance does not deteriorate.

  In addition, a decrease in the liquid temperature due to mixing of the untreated liquid to be processed may be predicted, and the operation may be performed by fixing the flow rate at a temperature in which the amount of dissolution air is reduced in advance by the amount of decrease. However, the circulating flow rate may be reduced.

  The pressure at the outlet of the circulation pump 31 is preferably about 0.3 to 0.8 MPa in consideration of reducing the required power and reducing the diameter of the fine bubbles. Considering that the amount of dissolved air is proportional to the pressure, the circulating water flow rate is 30 to 100 times the amount of untreated liquid to be treated supplied from the untreated liquid supply system, and the untreated liquid is circulated. Since it is diluted 30 to 100 times with water, the oil content of the liquid to be treated supplied to the separation unit 81 has a low concentration.

  In the suction part 82 at the upper part of the separation part 81, the processed liquid corresponding to the unprocessed liquid to be processed supplied from the pipe 23 is sucked at a speed slower than the rising speed of the fine bubbles, and the discharge pipe 51. To discharge from. In the oil-water separation process, in which the oil-water separation process is performed with fine bubbles, the large-diameter oil particles in the liquid to be treated float and separate before the small-diameter oil particles. Even if it remains in the liquid, it can be continuously discharged in a state where the oil concentration in the treated liquid that has been treated has reached a target value (for example, oil concentration 5 mg / L, which is a drainage standard for mineral oil), High processing capacity.

  Moreover, since the pH value is maintained from neutral to weakly alkaline by a sodium hydroxide aqueous solution as described later, the liquid to be processed during processing and the liquid to be processed are reduced in the corrosiveness of the metal member. There is no problem even if it is discarded.

  The floating oil accumulates on the upper part of the separation unit 81. Therefore, when the valve 52 provided in the middle of the discharge pipe 51 is temporarily closed during continuous operation, the liquid surface 61 to be treated and the floating oil liquid level 62 in the separation unit 81 rise, and the floating oil liquid level 62 is shielded. When the height of the plate 12 is exceeded, the floating oil overflows (overflows) and flows down to the floating oil receiving portion 83. When the floating oil in the separation unit 81 decreases, the valve 52 is opened slowly, the liquid to be processed is discharged from the discharge pipe 51, the liquid surface 61 to be processed is lowered, and the continuous processing is continued.

Next, the intermittent processing operation will be described.
As a preparation, the circulation pump 31 is operated in a state in which the valve 52 is closed and the separation unit 81 is filled with fresh water or a processed liquid to be processed. Although the valve 22 is closed, the valves 36 and 42 are open, and the dissolving air flows from the air supply pipe 41. The power of the circulation pump 31 becomes heat and is transmitted to the liquid to be processed, and the temperature of the liquid to be processed in the separation unit 81 is increased. In order to reduce the density of the liquid to be processed, a heating unit for increasing the temperature of the liquid to be processed may be provided in the separation unit 81.

  When the liquid to be processed rises to a predetermined temperature, the operation of the circulation pump 31 in the circulation system is stopped, the valve 42 is closed, the valve 22 of the liquid supply system to be processed is opened, and the supply pump 21 is operated. A liquid to be processed in a processing state is supplied. The liquid to be processed flows from the nozzle 33 to the separation unit 81 via the path of the pipe 30 and the pipes 32 and 37.

  Since the liquid to be processed has a lower temperature and a higher density than the fresh water or the processed liquid to be processed in the separation unit 81, the liquid to be processed accumulates at the bottom of the separation unit 81, and the processed liquid with a low processed and low oil concentration. Is pushed up to the top of the separation part 81 and discharged from the suction part 82 via the discharge pipe 51 and the valve 52. For example, the volume from the upper end of the partition plate 15 to the bottom of the separation unit 81 is 40 L, the temperature of fresh water or treated liquid to be treated is 320 K, the temperature of untreated liquid to be treated is 283 K, and the untreated liquid to be treated is supplied. Is performed at 20 L / h, only 30 L or more of the processed liquid can be discharged.

  When only the processed liquid to be processed is discharged, the valve 22 and the valve 52 are closed to stop the supply of the unprocessed liquid to be processed, and the circulation pump 31 performs circulation outside the tank. Next, the valve 36 is adjusted to confirm that the pressure at the inlet of the circulation pump is lower than the atmospheric pressure using a pressure gauge (not shown), the valve 97 is opened, and the difference between this pressure and the pressure of the calcium chloride aqueous solution 91 is determined as the driving force. Then, a desired amount of calcium chloride aqueous solution is supplied from the tank 91 and the valve 97 is closed. Similarly, the valve 77 is opened, a desired amount of aqueous sodium hydroxide solution is supplied from the tank 71, and then the valve 77 is closed.

  Next, when the valve 42 is opened, dissolution air flows from the air supply pipe 41.

  The amount of air dissolved in the liquid to be treated by the pressurization by the circulation pump 31 follows the Henry's law under the pressure, and the pressure applied to the fresh water flowing through the pipe 37 or the treated liquid to be treated and the pipe 37 The amount of dissolved air increases in proportion to the flowing flow rate. Further, the lower the temperature of the fresh water flowing through the pipe 37 or the processed liquid to be processed, the more air is dissolved. In actual operation, the operation is performed so that the pressure and flow rate are constant.

  Also in this case, the power of the circulation pump 31 becomes heat and is transmitted to the liquid to be treated, the liquid temperature rises, and the amount of dissolved air decreases. Therefore, the relationship between the liquid temperature and the amount of dissolved air is obtained in advance, and the amount of dissolving air introduced from the air supply pipe 41 by the liquid temperature obtained by the temperature measuring device 84 rises almost uniformly in the processing tank 11. The amount is adjusted by the valve 42 so that the amount is adjusted. For this reason, large bubbles due to excess air are not continuously generated, and the oil / water separation performance is not deteriorated.

  The valve 52 is closed, and fine bubbles are present in the liquid to be processed in the separation unit 81, and the liquid surface 61 to be processed is higher than the highest position of the discharge pipe 51. In this state, the floating oil accumulates above the liquid surface 61 to be treated in the separation unit 81, but the upper end position of the shielding plate 12 is set higher than the floating oil liquid surface 62, and the floating oil is collected during circulation of the liquid to be treated. There is no overflow from the shielding plate 12 to the floating oil receiving portion 83.

  During the circulation outside the tank, the oil content below the separation unit 81 rises by the fine bubbles and separates the oil and water. In the floating oil separation method, the higher the oil content, the better the separation performance. The low concentration region has separation performance close to continuous processing.

  According to the observation by the present inventors, the oil concentration of the liquid to be treated in the untreated state decreases to about 1/5 of the intermediate concentration or less in the first half 50% of the circulation outside the tank, and intermediate in the second half 50% of the time. It has been confirmed that the oil concentration is lower than the concentration, and further reduced to a low concentration of about 1/5 (the target concentration in the continuous treatment). The ratio of reduction in the first half is about the same, but in terms of absolute value, most of the oil is separated in the first half.

  When the liquid to be treated in the separation unit 81 decreases to the target oil concentration, the circulation pump 31 is stopped, the valve 42 is closed, the valves 22 and 52 are opened, the supply pump 21 is operated, and the untreated state is reached. The liquid to be processed is supplied from the bottom of the separation unit 81. During this period, the processed liquid to be processed in the upper part of the separation unit 81 flows out from the discharge pipe 51 by the same amount as the newly supplied unprocessed liquid to be processed.

  When the supply pump 21 and the circulation pump 31 are alternately operated and stopped for supplying and circulating the liquid to be treated as described above, and the difference between the floating oil liquid level 62 and the liquid surface 61 to be treated becomes large, that is, When the floating oil collects on the upper part of the separation unit 81, the valve 52 of the discharge pipe 51 is closed during the operation of the supply pump 21, and the liquid surface 61 to be treated is flush with the shielding plate 12 to shield the floating oil. It overflows from the upper end of the plate 12 and is discharged to the floating oil receiving portion 83.

  In a normal screw-type air compressor, about 1 mm of floating oil is accumulated by continuous operation for one week, and therefore, the floating oil may be discharged about once a week. This discharge time can be determined not only by the operation time but also by measuring the floating oil amount and the floating oil thickness.

  In this intermittent treatment, clean water or a treated liquid to be treated and a liquid to be treated of about 50% in an untreated state are mixed in the separation unit 81 to perform an oil / water separation treatment, and the oil content is reduced from a high concentration to a low concentration. It will be lowered in time.

  As described above, the drain flow rate is high and the oil concentration is low when the amount of moisture in the atmosphere corresponding to summer is high. When the amount of water in the atmosphere corresponding to winter is small, the drain flow rate is small and the oil concentration is high. Therefore, taking advantage of the features of the above two operation methods, it is possible to perform continuous processing when the drain flow rate is high and the oil concentration is low, and by performing intermittent operation when the drain flow rate is low and the oil concentration is high, small and high speed processing is possible. A possible oil / water separator can be constructed.

  In the intermittent treatment operation, it is possible to prepare a plurality of patterns with different lengths of the circulation period outside the tank and the liquid supply period to be treated to widen the margin of the intermediate concentration range. In addition, the apparatus can be configured only by the intermittent processing operation.

According to the present invention, since the low-hydrophobic oil is contained, the liquid to be treated which does not separate the oil and water can be separated at high speed even after being left for about half a year.
In the method of promoting oil-water separation by adding calcium chloride or magnesium chloride and sodium hydroxide, the addition of sodium hydroxide after sufficiently mixing calcium chloride or magnesium chloride and the liquid to be treated increases the oil-water separation effect. Oil-water separation performance is higher in the intermittent treatment operation than in the continuous treatment operation.

  Information on the drain flow rate or oil concentration is necessary for selecting these operation patterns. Since there is no method for measuring the oil concentration in a short time, information on the drain flow rate is used for selecting an operation pattern. The drain flow rate can be calculated from the amount of moisture in the atmosphere, the air compressor discharge air pressure, the air cooler outlet temperature, and the condensate collection efficiency. Accordingly, the atmospheric temperature and atmospheric humidity may be measured. On the other hand, a tank for storing drainage from the air compressor is usually provided, and a liquid level gauge may be attached therein, and the drain flow rate may be calculated from the change in the liquid level. It is also possible to measure only the atmospheric temperature, calculate the maximum drain flow rate with an atmospheric humidity of 100%, and use this value for control.

  Actually, these methods are used alone or in combination for the control. These patterns and operation mode switching are prepared as a sequence program in a control device (not shown), and based on the measurement results of each item described above, such as humidity in the atmosphere for checking the oil concentration, a calendar, etc. It can also be switched appropriately.

  Next, another embodiment of the present invention shown in FIG. 2 will be described.

  In the embodiment shown in FIG. 1, the supply of the sodium hydroxide aqueous solution and the calcium chloride aqueous solution uses the differential pressure between the inlet pressure of the circulation pump 31 and the atmospheric pressure as the driving force. However, the embodiment of FIG. A desired amount of aqueous sodium hydroxide solution and aqueous calcium chloride solution are supplied by air-operated syringes 73 and 93 that perform reciprocating motion, and air pipes 74 and 94 and air supply control valves 75 and 95 are attached. The sodium hydroxide aqueous solution and the calcium chloride aqueous solution can be supplied into the separation part 81 of the treatment tank 11 without depending on the operating condition of the external circulation system including the circulation pump 31 and the supply amount can be arbitrarily adjusted. .

  This embodiment is suitable for the intermittent treatment operation because the sodium hydroxide aqueous solution and the calcium chloride aqueous solution cannot be continuously supplied.

  Next, another embodiment of the present invention shown in FIG. 3 will be described.

  In the embodiment shown in FIG. 3, dedicated tanks 71 and 91 for sodium hydroxide aqueous solution and calcium chloride aqueous solution are provided with dedicated fixed supply pumps 76 and 96, respectively, and the operation conditions of the external circulation system including the circulation pump 31 and the like are affected. Accordingly, an aqueous solution of sodium hydroxide or an aqueous solution of calcium chloride is supplied into the separation part 81 of the treatment tank 11 and the supply amount can be arbitrarily adjusted, so that it is possible to cope with a continuous treatment operation and an intermittent treatment operation. It is also possible to operate by connecting the outlets of the pipes 72 and 92 to the pipe 30 or 32.

  Next, another embodiment of the present invention shown in FIG. 4 will be described.

  In this embodiment, as in the embodiment of FIG. 3, dedicated supply pumps 76 and 96 are provided respectively, but an aqueous solution of sodium hydroxide and an aqueous solution of calcium chloride are supplied to the addition liquid upper tanks 78a and 98a through the pipes 72 and 92, respectively. Then, the excess liquid after filling the additive liquid temporary tanks 78b, 98b inside these is recovered into the tanks 71, 91 through the pipes 80, 100.

  The sodium hydroxide aqueous solution and the calcium chloride aqueous solution are quantitatively mixed into the liquid to be treated in the separation unit 81 through the pipes 79 and 99 by opening the valves 77 and 97 from the additive solution temporary tanks 78b and 98b.

  This embodiment is suitable for the intermittent treatment operation because the sodium hydroxide aqueous solution and the calcium chloride aqueous solution cannot be continuously supplied as in the embodiment of FIG.

  Although not shown in the drawings, in each of the embodiments shown in FIGS. 2 to 4, a sodium hydroxide aqueous solution is supplied to the separation unit 81 of the processing tank 11 via a tank not shown, and the calcium chloride aqueous solution is supplied as shown in FIGS. You may make it supply to the separation part 81 of the processing tank 11 by the method of this.

  FIG. 5 shows an example of the oil separation effect according to the present invention.

  Superlub (trade name of Kobelco Compressor Co., Ltd.), a special oil for screw compressor lubricants, retains its colloidal shape even if the drain from the compressor is allowed to stand for more than 6 months. There is no floating separation. Even when this oil and pure water are mixed to produce a simulated drain, the oil does not float and separate even if left for a long period of time.

  When the oil concentration of this simulated drain is set to 300 mg / L equivalent to that of a normal screw compressor drain, when 1 g or more of calcium chloride is added to 1 L of drain and the treatment device of FIG. Oil separation up to L is possible. The same result is obtained even when the oil concentration is changed, and the characteristic is shown by the region surrounded by OBC in FIG.

  Calcium chloride is used as a food coagulant, and calcium, which is a positive divalent metal ion, has an effect of electrically neutralizing and aggregating negatively charged oil particles. However, calcium chloride is also used as a snow melting agent, and is known to corrode metals at high concentrations. Therefore, when calcium chloride is used for oil separation, it is necessary to reduce the amount of calcium chloride added. The moisture of the compressor drain is condensed from the moisture in the atmosphere and is acidic with a pH value of 4 to 6 even when the lubricating oil is mixed. Even if calcium chloride as an inorganic salt is added to this drain, the pH value does not change, and the acidity is 4 to 6.

  As a result of various investigations on methods that enable oil separation even when the amount of calcium chloride added is reduced, it becomes easier to separate oil if calcium chloride is added in advance and the pH value after addition of sodium hydroxide is made alkaline to 7 or more. When the treatment apparatus of FIG. 1 was operated with a pH value of 8 or more, it was found that oil separation was possible up to 5 mg / L or less of the drainage standard even with 50% of calcium chloride alone added. The characteristic is shown by the area surrounded by OCD in FIG. When operating in this region, the drainage is weakly alkaline and the metal material is less susceptible to oxidative corrosion.

  If the amount of calcium chloride added is further reduced, oil-water separation cannot be achieved up to 5 mg / L of the drainage standard even if sodium hydroxide is added. The characteristic is shown by the area surrounded by OAD in FIG. Therefore, the line segments OC and OD indicate the lower limit of the oil / water separation effect by adding calcium chloride or sodium hydroxide to the oil concentration of the drain, respectively.

  The above characteristics can also be explained as follows. That is, if the concentration of oil in the drain is increased with the addition amount of calcium chloride (CaCl2) as B1, the oil cannot be separated up to 5 mg / L of the drainage standard if the oil concentration is A1 or more. Therefore, when calcium chloride (CaCl2) is added in an amount of B1, and sodium hydroxide (NaOH) is added to make the drain alkaline, the oil is separated up to 5 mg / L of the drainage standard up to the oil concentration A2. become able to. When the oil concentration is A2 or more, oil-water separation cannot be performed when the amount of calcium chloride (CaCl2) added is B1.

  Another substance that promotes the aggregation of oil is magnesium chloride (MgCl2), which is approved for use as a food coagulant. When used in combination with sodium hydroxide in the same manner as calcium chloride, the same effect as in FIG. Is obtained. Calcium chloride and magnesium chloride may be used in combination with sodium hydroxide.

  When aluminum chloride, which is a compound of aluminum, which is a positive trivalent metal, is used as another substance for promoting oil aggregation, the aggregation effect is higher than that of calcium chloride. However, since aluminum has a particularly strong metal corrosiveness, it is difficult to use a metal because the metal cannot be used. In addition, there is concern about the impact on the human body, and there is a tendency to restrict use in water treatment.

  In the above description, oil-water separation of mineral oil has been described. However, the present invention may be applied to separation of edible oil. Since vegetable oil has a slightly effluent standard of 30 mg / L, the amount of calcium chloride, magnesium chloride, sodium hydroxide and the like can be reduced accordingly.

It is a figure which shows the oil-water separator which becomes one Embodiment of this invention. It is a figure which shows the oil-water separator which becomes other embodiment of this invention. It is a figure which shows the oil-water separator which becomes another embodiment of this invention. It is a figure which shows the oil-water separator which becomes another embodiment of this invention. It is a figure which shows an example of the oil-water separation effect of this invention.

Explanation of symbols

11 ... Processing tank
12 ... Shield plate
15 ... Partition plate
21 ... Supply pump
22, 36, 42, 52 ... valve
23, 30, 32, 37, 41, 51 ... piping
31 ... circulation pump
33 ... Nozzle
61 ... Liquid surface to be treated
62 ... Floating oil level
71 ... Sodium hydroxide tank 81 ... Separation part
82 ... Pocket-shaped inhalation part
83 ... Floating oil receiving part 91 ... Calcium chloride aqueous solution tank

Claims (2)

By supplying air to the liquid to be processed and pressurizing it with a pump to dissolve the air in the liquid to be processed, and blowing the air dissolved from the lower part of the processing tank as bubbles together with the liquid to be processed, the liquid to be processed in the processing tank In the oil-water separation method in which the oil contained in is floated with bubbles and the liquid to be treated is separated from water and oil.
Oil water and supplying bubbles into the liquid to be treated and at least one of sodium hydroxide calcium chloride and magnesium chloride are mixed by mixing sodium hydroxide later than at least one of calcium chloride and magnesium chloride Separation method. The oil-water separation method according to claim 1, wherein at least one of calcium chloride and magnesium chloride and sodium hydroxide are separately mixed in a liquid to be treated containing an oil component having low hydrophobicity, thereby bringing the liquid to be treated into an alkaline state. An oil-water separation method characterized by promoting oil-water separation.

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