JP4194469B2 - Oil / water separator - Google Patents

Description

  The present invention relates to an oil-water separation apparatus by a levitation separation method in which oil contained in a liquid to be treated is floated by supplying fine bubbles into the stored liquid to be treated to separate water and oil.

  As an oil-water separator by the floating separation method, there is one described in Patent Document 1 described below.

In this apparatus, the liquid to be treated in the treatment tank is obtained by pumping up the liquid to be treated from a large-capacity treatment tank, pressurizing and mixing the pressurized air, removing excess air, and then depressurizing the liquid into the treatment tank. Microbubbles are generated inside. By attaching these fine bubbles and oil, the oil rises and the oil and water are separated.

  In the following Patent Document 1, no reference is made to the recovery of the floated oil.

  As an oil-water separator that performs oil-water separation by a floating separation method by generating fine bubbles in a liquid to be treated in a treatment tank in a form different from the following Patent Document 1, there is one described in Patent Document 2 described below.

  In Patent Document 2, as a means for collecting oil, a scum scraping device is provided near the liquid surface, and the scum scraping device is periodically operated to be accumulated in the scum receiver.

  The scum is said to be a cream-like substance that floats, such as dust contained in the liquid to be treated, agglomerates into fine bubbles together with oil.

JP-A-5-317847

JP 2001-300540 A

  If a scum scraping device that periodically removes oil or scum that has floated to the liquid surface as in Patent Document 2 is provided near the liquid surface, the liquid surface becomes complicated and the inside of the processing tank in which the liquid to be processed is stored is cleaned. However, the scum itself that adheres to and solidifies on the scum scraping device must also be removed, which may make maintenance difficult. Moreover, the apparatus becomes large by providing the scum scraping device.

  Therefore, an object of the present invention is to provide an easy-to-maintain oil-water separator that can reliably collect floating oil even if the apparatus has a simple configuration without increasing the size.

  A feature of the oil / water separation device of the present invention that achieves the above object is that the oil contained in the liquid to be treated is floated by supplying fine bubbles into the liquid to be treated stored in the treatment tank, thereby separating the water and the oil. In the oil / water separation apparatus, the treatment tank has a shielding plate for partitioning the inside of the tank into a separation part for storing the liquid to be treated and separating the oil and water, and a floating oil receiving part for collecting the oil floating and separated in the separation part. A nozzle that blows out bubbles is provided at the lower part of the separation unit, and an excess air discharge pipe that guides large bubbles out of the bubbles blown out from the nozzle to the liquid surface part above the separation unit is provided. It is directed to the oil receiving part, and the floating oil in the liquid surface part is pushed to the floating oil receiving part and collected by the flow of air coming out of the opening of the surplus air discharge pipe.

According to the present invention, the floating oil that floats on the liquid surface portion of the liquid to be treated in the separation section by using the large bubbles that do not contribute to the oil- water separation among the bubbles blown out from the nozzle is received by the floating oil receiver. Since there is no need to install a special device such as a scum scraping device, it is easy to collect the floating oil without increasing the size of the device, and to maintain the device easily. It is.

  Hereinafter, an embodiment of the present invention shown in FIG. 1 will be described by taking an example of processing drain (liquid to be processed) discharged from a screw compressor.

  In FIG. 1, a shielding plate that separates a separation unit 81 that stores a liquid 61 to be treated and performs oil-water separation and a floating oil receiving unit 82 that collects oil floating and separated by the separation unit 81 in the treatment tank 11. 12 is provided. A pipe 30 attached to the bottom of the treatment tank 11 is connected to a circulation pump 31 via a valve 36, and an outlet side pipe 37 of the circulation pump 31 is connected to a nozzle 33 in the large bubble remover 10 connected to the treatment tank 11. It is. The nozzle 33 in the large bubble remover 10 uses the separating direction 81 as the ejection direction. A path from the pipe 30 through the circulation pump 31 to the large bubble removing device 10 constitutes a liquid to be treated circulation piping system for circulation outside the tank.

  The large bubble remover 10 has a cylindrical portion extending into the separation portion 81, and has a plurality of small openings on both sides and an upper portion of the cylindrical portion, and the liquid 61 to be treated is ejected from the nozzle 33 into the cylindrical portion. By doing so, the structure by which to-be-processed liquid is supplied to the isolation | separation part 81 from each small mouth with a fine bubble may be sufficient.

  The large bubble remover 10 is divided into two parts, one part is connected to the separation part 81 of the processing tank 11, and the other is attached with an excess air discharge pipe 9 for flowing a branched flow mixed with large bubbles from the upper part. Yes. The surplus air discharge section 13 of the surplus air discharge pipe 9 is arranged at a position in the vicinity of the liquid surface 61A to be treated of the separation section 81 in the processing tank 11, and floating oil 62 is placed at the tip of the surplus air discharge section 13. An opening 14 for discharging the air that is pushed toward the floating oil receiving portion 82 is disposed. As shown in FIG. 2, the opening 14 of the surplus air discharge part 13 is parallel to the shielding plate 12 that divides the treatment tank 11 into a separation part 81 and a floating oil receiving part 82, and is one-stage configuration that is horizontal to the liquid surface 61A to be treated. It is said. Further, the opening 14 may be a plurality of small openings arranged horizontally.

  Returning to FIG. 1, an air supply pipe 35 for supplying air is connected to the pipe 30 via a valve 34, and a supply pipe 23 constituting a liquid supply system to be treated is connected to the pipe 30. A supply pump 21 is provided in the pipe 23 via a valve 22. Although not shown, there is a tank that stores an untreated liquid at the tip of the supply pump 21.

  A pipe seat for a discharge pipe 41 that discharges the processed liquid 61 to be processed from the top of the separation section 81 is provided at the upper part of the separation section 81, and the discharge pipe 41 is connected to a connection section (pipe seat) with the separation section 81. It is piped up to a position lower than the connecting portion with the separating portion 81 and has a valve 42 in the middle thereof.

  The highest position of the discharge pipe 41 is set lower than the highest position of the shielding plate 12 of the processing tank 11 so as to have a positional difference D1. Therefore, when supplying and storing the liquid 61 to be processed in the separation unit 81, if the valve 42 is opened, the liquid 61 to be processed flows out of the discharge pipe 41, and the liquid surface 61A to be processed in the separation unit 81 is If the valve 42 is closed and the liquid 61 to be treated is supplied into the separation tank 81 when the discharge pipe 41 is regulated at the highest level, the liquid level 61A to be processed rises above the highest level of the discharge pipe 41. The discharge pipe 41 has a function of discharging the liquid 61 to be processed and adjusting the water level by opening and closing the valve 42. Incidentally, the floating oil liquid level 62 </ b> A of the floating oil 62 that has risen as a result of the oil / water separation formed at the upper part of the liquid surface 61 </ b> A to be processed also moves up and down by the supply of the liquid 61 and the opening / closing of the valve 42.

  A partition plate 15 is provided so as to surround the periphery of the tube seat of the discharge pipe 41, a pocket-like suction part 83 is formed, and the separation part 81 is raised to the processed liquid 61 to be processed flowing into the discharge pipe 41 from the separation part 81. It prevents the fine bubbles and oil particles (oil content) from entering.

  The highest position of the partition plate 15 is set lower than the highest position of the discharge pipe 41 so as to have a positional difference D2. Further, the highest position of the partition plate 15 is made higher than the connection portion (tube seat) with the separation portion 81 of the discharge pipe 41 so as to have a positional difference D3.

  If the descending speed of the liquid 61 to be treated in the suction part 83 determined by the outflow amount of the liquid 61 to be treated in the discharge pipe 41 and the inlet area of the suction part 82 is slower than the rising speed of the fine bubbles, Air bubbles and oil particles do not flow into the suction portion 83 and enter the discharge pipe 41.

  An oil discharge pipe 51 for discharging the recovered oil 63 is provided at the bottom of the floating oil receiver 82. Although not shown, a pipe is provided at the bottom of the separation unit 81 and a valve is provided in the middle thereof, and these are used when it is necessary to discharge the liquid 61 to be treated inside the separation unit 81. The liquid 61 to be processed may be supplied by connecting the supply pipe 23 to the lower portion of the separation unit 81.

Next, the operation will be described.
In the following description, oil particles and suspended matter in the liquid to be treated 61 adhering to the fine bubbles and floating or those floating on the liquid surface 61A are collectively referred to as floating oil.

  First, the continuous processing performed at the time when the absolute humidity and the drain flow rate are large as shown in FIG. 3 will be described.

  As a preparation, the valve 22 is closed, the supply pump 21 is stopped, the valve 42 is opened, the separation part 81 of the treatment tank 11 is filled with fresh water or a treated liquid, and the treated liquid surface 61A is a discharge pipe. If it coincides with the highest position of 41, the circulating pump 31 is operated to start continuous processing. At the start of continuous processing, the valve 22 is opened and the supply pump 21 is operated. The valves 34 and 36 are in an open state. When the liquid 61 to be treated flows through the pipe 30, the air supply pipe 35 side has a negative pressure, and dissolution air flows from the air supply pipe 35.

  The amount of air to be dissolved follows Henry's law under pressure, and the amount of air to be dissolved increases in proportion to the pressure and flow rate applied to the liquid 61 to be processed flowing through the pipe 30. Further, the lower the temperature of the liquid 61 to be processed flowing through the pipe 30, the larger the amount of dissolved air. In actual operation, the operation is performed so that the pressure and flow rate are constant.

  In the suction part 83 at the upper part of the separation part 81, the treated liquid 61 corresponding to the untreated liquid corresponding to the untreated state supplied from the treated liquid supply system is sucked at a speed slower than the rising speed of the fine bubbles. Then it is discharged from the discharge pipe 41.

  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 61 is untreated. Since it is diluted 30 to 100 times with circulating water, the oil content in the liquid 61 to be treated supplied to the separation unit 81 is low.

  The to-be-processed liquid 61 ejected from the nozzle 33 is decompressed in the large bubble removing device 10, and the air dissolved in the to-be-processed liquid 61 becomes fine bubbles, but the undissolved air blows out from the nozzle 33 as large bubbles. Since the buoyancy applied to the large bubbles is larger than that of the fine bubbles, the excess air discharge pipe 9 rises as large bubbles 93. The liquid to be treated in the surplus air discharge pipe 9 also has oil, and a part of the oil rises by adhering to the large bubbles 93, but most rises slowly, and the air flows from the opening 14 of the surplus air discharge unit 13. Attracted by and leaked.

  The fine bubbles ride on the flow of the liquid 61 to be treated that exits from the nozzle 33, reach the separation unit 81, and slowly rise to adhere and aggregate oil and suspended matter to become floating oil 62.

  In this continuous processing, the processed liquid 61 corresponding to the amount of processed liquid in an unprocessed state supplied from the processed liquid supply system is caused to flow out from the suction part 83 above the separation part 81 through the discharge pipe 41. Therefore, the downward flow that obstructs the oil / water separation is less than that in the case where only the circulation outside the tank is performed, and the separation performance by the fine bubbles can be maintained even if the separation portion is made small.

  When the floating oil 62 above the separation unit 81 temporarily closes the valve 42 provided in the middle of the discharge pipe 41 during continuous operation, the liquid surface 61A to be treated and the floating oil liquid level 62A inside the separation unit 81 rise, The surplus air discharged from the opening 14 of the surplus air discharge unit 13 causes the floating oil 62 on the liquid surface 61A to be treated to flow toward the shielding plate 12 and flow down to the floating oil receiving unit 82 over the shielding plate 12. .

  When the floating oil 62 on the liquid surface 61A to be processed decreases, the valve 42 is opened, the liquid 61 to be processed is discharged from the discharge pipe 41, the liquid surface 61A is lowered, and continuous processing is continued.

  Next, the intermittent process performed at a time when the absolute humidity shown in FIG. 4 is low and the drain flow rate is low will be described.

  First, as in preparation, as in the case of continuous processing, the circulation pump 31 is operated in a state where the separation unit 81 is filled with fresh water or a processed liquid 61 to be processed. The valve 36 and the valve 34 are in an open state, and dissolution air flows from the air supply pipe 35.

  The power of the circulation pump 31 becomes heat and is transmitted to the liquid to be processed 61 flowing through the pipe 30 to raise the temperature of the liquid to be processed 61 in the separation unit 81, so that the density of the liquid to be processed 61 is reduced. In order to reduce the density of the liquid 61 to be processed, a heating unit for raising the temperature of the liquid 61 to be processed may be provided in the separation unit 81.

  When the operation of the circulation pump 31 in the processing liquid circulation system is stopped, the valve 42 and the valve 22 of the processing liquid supply system are opened, the supply pump 21 is operated, and the unprocessed liquid 61 is supplied, The processing liquid 61 flows into the separation unit 81 from the pipe 30, the pipe 37, and the nozzle 33.

  Since the liquid 61 to be treated has a lower temperature and a higher density than the fresh water in the separation unit 81 or the processed liquid 61 to be treated, the liquid to be treated 61 accumulates at the bottom of the separation unit 81 and has a low density and a low concentration of treated oil. The processing liquid 61 is pushed up to the upper part of the separation part 81 and is discharged from the suction part 83 via the discharge pipe 41 and the valve 42.

  For example, the volume from the upper end of the partition plate 15 to the bottom of the separation part 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 61 to be treated is supplied. When performed at 20 L / h, only the processed liquid 61 to be processed can be discharged by 30 L or more.

  When only the processed liquid 61 to be processed is discharged, the valve 22 and the valve 42 are closed, the supply of the unprocessed liquid 61 is stopped, and circulation outside the tank by the circulation pump 31 is performed. The valve 36 and the valve 34 are in an open state, and dissolution air flows from the air supply pipe 35. In this case as well, the operation is performed so that the pressure and the flow rate become constant as in the continuous processing.

  Since the valve 42 is closed and air bubbles are present in the liquid 61 to be processed in the separation unit 81, the liquid surface 61 </ b> A to be processed becomes higher than the highest position of the discharge pipe 41. In this state, the floating oil 62 accumulates above the liquid surface 61A to be treated inside the separation unit 81, and the floating oil 62 passing through the surplus air discharge pipe 9 similarly accumulates above the liquid surface 61A to be treated from the surplus air discharge part 13. The shielding plate 12 is disposed higher than the floating oil liquid level 62A, and the floating oil 62 does not overflow from the shielding plate 12 to the floating oil receiving portion 82 during circulation. During the circulation outside the tank, the oil content of the separation unit 81 rises due to the fine bubbles and separates the oil and water.

  In the flotation separation method, the higher the oil content, the better the separation performance. The low concentration region has separation performance close to that of continuous processing.

  According to the observations of the present inventors, the oil concentration of the untreated liquid 61 is reduced to about 1/5 of the intermediate concentration or less in the first half 50% of the circulation outside the tank, and the middle in the second half 50%. 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 61 to be treated in the separation unit 81 decreases to the target oil concentration, the circulation pump 31 is stopped, the valves 22 and 42 are opened, and the supply pump 21 is operated to supply the untreated liquid 61 to be treated. To do. During this period, the processed liquid 61 processed by the separation unit 81 is discharged from the discharge pipe 41 by the same amount as the supplied unprocessed liquid 61 to be processed.

  The supply pump 21 is repeatedly operated and stopped alternately for supplying and circulating the liquid 61 to be treated. When the difference between the floating oil liquid level 62A and the liquid surface 61A to be processed increases, When 62 is accumulated, the valve 42 of the discharge pipe 41 is closed during the operation of the supply pump 21 so that the liquid surface 61A to be treated is flush with the shielding plate 12. Next, the surplus air 93 is discharged from the opening 14 of the surplus air discharge part 13 by operating the circulation pump 31 and processing the normal processing liquid. The air flowing out from the opening 14 blows the floating oil 62 on the liquid surface 61A to be treated, and guides the floating oil 62 to the floating oil receiving portion 82 over the shielding plate 12.

  In a normal screw compressor, about 1 mm of floating oil 62 is accumulated by continuous operation for one week, so that the floating oil 62 is 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 treated liquid to be treated and about 50% untreated liquid are mixed in the separation unit 81 and subjected to oil-water separation treatment, and the oil content is lowered from a high concentration to a low concentration in a short time. become.

  FIG. 3 shows a configuration of the surplus air discharge unit 13 that is suitable when the difference in the liquid level to be processed between the processing operation and the floating oil recovery is large.

  As shown in FIG. 1 and FIG. 2, when the opening 14 of the surplus air discharge unit 13 has a one-stage configuration that is horizontal to the liquid surface 61A to be processed at the time of the processing operation, When the difference is large (specifically, 15 mm or more), the position of the opening in the surplus air discharge unit 13 is lower than the liquid surface 61A to be treated when the floating oil is recovered.

  Even if surplus air flows out from the opening 14 of the floating oil discharge part 13 in this state, the surplus air cannot move upward in the liquid surface direction and push the floating oil 62 in the direction of the shielding plate 12. It cannot be led to the receiving part 82.

  Therefore, as a suitable case when the difference in the liquid level to be processed between the processing operation and the floating oil recovery is large, the surplus air discharge unit 13 has a position corresponding to the liquid level to be processed during the processing operation. Two openings, 14A, and an opening 14B at a position corresponding to the liquid surface height (height position of the shielding plate 12) at the time of recovery of the floating oil are provided. It is larger than the area. The openings 14A and 14B of the surplus air discharge unit 13 are parallel to the shielding plate 12 like the openings 14 shown in FIG. 2, but each of the openings 14A and 14B may be formed by horizontally arranging a plurality of small openings. In this case, in the sum total of the cross-sectional areas of the plurality of foreheads, the cross-sectional area of the opening 14A in the lower part may be larger than the cross-sectional area of the opening 14B in the upper part.

  When the liquid level of the liquid 61A to be processed is adjusted to the lower opening 14A of the surplus air discharge unit 13 as shown in FIG. 3A, the surplus air floats from the lower opening 14A. It flows out together with the oil 62.

  At this time, since the upper opening 14B is located higher than the liquid surface 61A to be treated, a part of the surplus air also flows out from the upper opening 14B, but due to the cross-sectional area of both the openings 14A and 14B, the opening 14B The amount of spilled water is small, and operation that maintains the processing performance is possible.

  Since the upper opening 14B is provided in the vicinity of the height position of the liquid surface 61A to be treated (the height position of the shielding plate 12) that is raised at the time of floating oil recovery, as shown in FIG. It is discharged together with the floating oil 62 from the upper opening 14B.

  At this time, surplus air flows in the direction of the shielding plate 12 in parallel with the liquid surface 61A to be treated and pushes the floating oil 62. The surplus air in the surplus air discharge section 13 at this time passes through the upper part of the horizontal pipe parallel to the liquid surface 61A to be treated and flows upward in the pipe perpendicular to the liquid surface 61A to be treated. Become. Since the lower opening 14A is disposed where this excess air does not flow, the excess air does not flow out. In addition, since the opening cross-sectional area of the upper opening 14B is smaller than the opening cross-sectional area of the lower opening 14A, the pressure in the surplus air discharge unit 13 rises, and the flow velocity of the air flowing out from the upper opening 14B becomes higher, so The oil 62 can be guided to the floating oil receiving portion 82 and the floating oil 62 can be recovered.

  FIG. 4 shows the relationship between the drain flow rate and oil concentration of a general screw compressor. When the amount of moisture in the atmosphere corresponding to summer is high, the drain flow rate is high and the oil concentration is low. 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, a small and high speed operation is achieved. A treatable 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.

  The dashed-dotted line in FIG. 4 indicates the concentration range divided into two patterns. It is divided into a high concentration region I and a medium concentration region II. In the region I, both the outside circulation period and the liquid supply period to be treated have a long first operation pattern. The treatment liquid supply period is a second operation pattern shorter than the I region. In winter, the first operation pattern is intermittently processed, and in spring and autumn, the second operation pattern is intermittently processed. In this way, the liquid to be processed in any state can be handled with a single device throughout the year. In addition, it can respond similarly also by changing only an outside tank circulation period.

  Selection of these operation patterns requires information on the drain flow rate or oil concentration. Since there is no method for measuring the oil concentration in a short time, drain flow rate information is used to select an operation pattern. The drain flow rate can be calculated from the amount of moisture in the atmosphere, compressor discharge air pressure, air cooler outlet temperature, and condensate collection efficiency. Therefore, there is a method for measuring the atmospheric temperature and atmospheric humidity.

  On the other hand, there is usually a method in which a tank for temporarily storing the drain from the compressor is provided, and a liquid level gauge is attached therein, and the drain flow rate is 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. In practice, these methods are used alone or in combination for control.

  The switching of these patterns and operation modes is prepared as a sequence program in a control device (not shown), and is based on the measurement results of the above-mentioned items such as atmospheric humidity for checking the oil concentration, a calendar, and the like. Thus, it can be switched appropriately.

  According to the present invention, floating oil can be reliably recovered without providing a special device using large bubbles that do not contribute to oil-water separation, and the device has a simple configuration and does not increase in size. An oil-water separator that is easy to maintain is obtained.

It is a figure which shows the oil-water separator which becomes one Embodiment of this invention. It is a schematic sectional drawing when the surplus air discharge part shown in FIG. 1 is seen from the top. It is a figure which shows the structure of the surplus air discharge part which becomes other embodiment of this invention. It is a figure which shows the relationship between the flow volume of the drain in a compressor, and oil concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 ... Excess air discharge pipe 10 ... Large bubble removal device 11 ... Processing tank 12 ... Shielding plate 13 ... Excess air discharge part 14, 14A, 14B ... Opening 15 ... Partition plate 21 ... Supply pump 31 ... Circulation pump 33 ... Nozzle 41 ... Discharge pipe 42 ... Valve 61 ... Liquid to be treated 61A ... Liquid surface to be treated 62 ... Floating oil liquid 62A ... Floating oil liquid surface 81 ... Separating part 82 ... Floating oil receiving part 83 ... Pocket-like suction part 93 ... Large bubbles (excess air)

Claims (3)

In the oil-water separator for separating the water and the oil by floating the oil contained in the liquid to be treated by supplying fine bubbles into the liquid to be treated stored in the treatment tank,
The treatment tank has a shielding plate that divides the inside of the tank into a separation part that stores the liquid to be treated and performs oil-water separation and a floating oil receiving part that collects the oil floating and separated in the separation part. A nozzle that blows out bubbles is provided, and an excess air discharge pipe that guides large bubbles out of the bubbles blown out from the nozzle to the liquid surface part above the separation part is provided, and the opening of the excess air discharge pipe faces the floating oil receiving part. The oil-water separator is characterized in that the floating oil on the liquid surface is pushed to the floating oil receiving part by the flow of air from the opening of the surplus air discharge pipe and recovered.   2. The oil / water separator according to claim 1, wherein the surplus air discharge part has two upper and lower openings, the lower opening is aligned with the liquid surface to be treated during the processing operation, and the upper opening is the floating oil. An oil-water separator characterized by being aligned with the position of oil floating on the surface of the liquid to be treated at the time of recovery, and forcing the oil to flow into the floating oil receiver with air flowing out from the upper opening. 3. The oil / water separator according to claim 2, wherein the upper opening has a smaller cross-sectional area than the lower opening.

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