JP2009183890A - Oil and water separation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil and water separation apparatus capable of performing high-speed treatment up to a low oil concentration even when a treatment tank of an oil and water separation apparatus according to a flotation method is compact. <P>SOLUTION: The oil and water separation apparatus causes oil content in the liquid to be treated to float and performs oil and water separation by mixing and dissolving air into the liquid to be treated which is to be fed to the treatment tank 11, ejecting the liquid to be treated in which air is mixed and dissolved into liquid to be treated in the treatment tank 11 and supplying air which is mixed and dissolved in the liquid to be treated in the treatment tank 11 as air bubbles. A nozzle 33 is used for ejecting the liquid to be treated in which air is mixed and dissolved into the liquid to be treated in a first treatment tank 81, and a nozzle 47 is disposed for ejecting the liquid to be treated containing fine air bubbles in the first treatment tank 81 into the liquid to be treated in a second treatment tank 82, wherein two treatment tanks are communicated with each other in the neighborhood of the surface of the liquid to be treated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil / water separator, and in particular, supplies air to a liquid to be processed to be sent to a processing tank and pressurizes it with a pump to dissolve part or all of the air in the liquid to be processed. It is related to the oil-water separator by the floating separation method in which the air contained in the treatment tank in the treatment tank is floated together with the bubbles by blowing out air as bubbles from the treatment liquid and the treatment liquid is separated into water and oil. is there.

A conventional oil / water separation apparatus based on a flotation separation method is described in Patent Document 1 below, in which air is mixed with a liquid to be treated, which is pumped from a large-capacity treatment tank, at a pump inlet, and a gas liquid at a pump outlet is mixed. After the air is further mixed and dissolved by the mixing means (air pulverizing means), the liquid to be treated is returned to the treatment tank, and fine bubbles are generated by spraying and depressurizing from the nozzle (or pressure valve). The fine bubbles adhere to the oil in the liquid to be treated, so that the oil rises in the water and the oil and moisture are separated.
JP 2005-246183 A

  In the above prior art, since most of the air that could not be dissolved in the liquid to be processed by the gas-liquid mixing means (air pulverizing means) becomes large bubbles in the processing tank, the floating separation performance is deteriorated. A large bubble separator for connecting the tanks is provided, and the large bubble separator is provided with a large bubble discharge pipe for separating and discharging only the large bubbles.

  One way to increase the oil separation capability of this apparatus is to increase the amount of air dissolved in the liquid to be treated. As an implementation means, the volume of the gas-liquid mixing means is increased, and the liquid retention time for the liquid to be treated is reduced. In the method of increasing the amount of dissolution by lengthening, there is a problem that the apparatus becomes large and takes a long processing time.

  When the object to be treated is a drain of an air compressor, a small amount of liquid to be treated is continuously discharged, and the flow rate and oil concentration change depending on the amount of moisture in the atmosphere. In order to reliably handle this, it is necessary to have a processing capability with the maximum oil concentration. On the other hand, it is desired that the installation area of the oil / water separator itself is small and the treatment tank is made small.

  If the installation area is simply reduced in size, the treatment tank must be made deeper (higher), the circulating flow that rises and falls within the treatment tank becomes stronger, and the oil particles that have once floated to the liquid level ride on the downward flow of water. Therefore, the oil concentration does not drop below a certain value.

  In order to improve the oil separation performance, increasing the amount of liquid to be treated ejected from the pressure valve so as to generate a large amount of fine bubbles from the pressure valve (nozzle), the circulating flow up and down in the treatment tank becomes stronger, Oil / water separation performance is reduced.

  An object of the present invention is to provide an oil / water separation apparatus based on a flotation separation method that can process even a small treatment tank at a high speed up to a low oil concentration.

  In order to achieve the above object, the present invention comprises mixing and dissolving air in a liquid to be processed to be sent to a processing tank, and discharging the liquid to be processed in which the air is mixed and dissolved into the liquid to be processed in the processing tank. In the oil / water separation apparatus for separating the oil and water by floating the oil in the liquid to be treated by supplying the mixed and dissolved air as bubbles to the liquid to be treated in the treatment tank, the treatment tank includes the first treatment tank and the second treatment tank. 1st pump which consists of a tank and sends a process liquid to a 1st process tank, the air dissolver which mixes and dissolves air in a process liquid, and the to-be-processed in the process tank for the process liquid which mixed and dissolved the air from this air dissolver A first circulation system composed of a first nozzle that discharges into the liquid, a second pump that sucks in the liquid to be processed containing bubbles in the first processing tank, and the sucked liquid to be processed is discharged into the second processing tank. A second circulation system comprising a second nozzle for supplying fine bubbles is provided. It is characterized in.

  The bottom area of the first treatment tank is larger than the bottom area of the second treatment tank.

  Further, in the present invention, air is mixed with the liquid to be processed to be sent to the processing tank, the liquid to be processed containing air is discharged into the liquid to be processed in the processing tank, and does not dissolve with the air dissolved in the liquid to be processed. In an oil / water separator that separates oil and water by supplying a part of the air as bubbles to the liquid to be treated in the treatment tank, the oil in the liquid to be treated is floated, and the treatment tank is horizontally below the liquid surface to be treated. A partition wall that is divided into two in the direction is provided and divided into a first treatment tank and a second treatment tank. In the first treatment tank, air is mixed and dissolved in the liquid to be processed, and the liquid to be processed is mixed and dissolved in the processing section. The first circulating system that discharges the liquid to be processed using a nozzle is configured, and the oil mixed in the liquid to be processed is supplied as fine bubbles to the liquid to be processed in the processing unit to reduce the oil content in the liquid to be processed. The liquid to be treated that floats and contains fine bubbles from the first treatment tank in the second treatment tank Pumping, constituting the second circulation system for injecting a pressurized treatment tank bottom nozzle by a pump without mixing air into the liquid to be treated in the treatment tank. The first treatment tank and the second treatment tank share the liquid level, and the treatment liquid is allowed to continuously flow from the second treatment tank to the first treatment tank during the treatment operation.

  According to the present invention, the liquid to be treated sucked from the first treatment tank by the circulation system of the second treatment tank uniformly contains fine bubbles, but the amount of dissolved air in the liquid to be treated is large and the residence time in the pipe Therefore, since the fine bubbles are not sufficiently dissolved in the liquid to be treated only by pressurization with the pump, the fine bubbles are injected from the nozzle into the liquid to be treated in the second treatment tank as a reinforcement. This injection forms a negative pressure region in the vicinity of the injection flow, so that the fine bubbles in the injection flow are expanded once, and the expanded bubbles are compressed by the pressure recovery in the downstream part, and split from the initial stage. Also become small bubbles with a small diameter. As the bubble diameter decreases, the surface area increases and the performance of adsorbing oil particles improves.

  However, it is considered that the oil separation performance is deteriorated when the bubble diameter is small because the floating speed necessary for the floating separation is small. Therefore, in the second treatment tank, the liquid to be treated is made to flow uniformly from the lower part to the upper part. For this reason, the fine bubbles will rise in the treatment tank at a total speed of the rising speed of the liquid to be treated and the speed of rising in the stationary liquid, which is equivalent to the speed at which the fine bubbles rise in the first treatment tank. More than that.

  As a result, the fine oil particles having the same diameter as that of the first treatment tank can be separated in a short time in the second treatment tank, and the high ability of separating large oil particles in the first treatment tank can be achieved. Together, the overall oil separation rate is increased. Due to these effects, even in a small treatment tank, oil-water separation can be reliably performed in a short time to a low oil concentration that can be discharged directly to the drainage channel.

  Hereinafter, embodiments shown in the drawings will be described.

  FIG. 1 shows an oil-water separator 10 according to an embodiment of the present invention. In FIG. 1, the inside of the processing tank 11 is divided into a first processing tank 81 and a second processing tank 82 by a partition wall 13 below the liquid surface position 61 to be processed. 82 and a floating oil receiving portion 83. The first treatment tank 81 and the second treatment tank 82 contain the treatment liquid and perform oil / water separation, and the floating oil receiving portion 83 receives the oil content 64 that is separated and floated in the treatment tanks 81 and 82 and overflows the shielding plate 12.

  The shielding plate 12 is disposed so as to be higher than the designed liquid surface position 61 and the floating oil surface position 62.

  A large bubble separator 14 is provided below the treatment tank 11 on the first treatment tank 81 side, and a nozzle (first nozzle) 33 for discharging a processing liquid is disposed inside the large bubble separator 14. A large bubble discharge pipe 15 is provided so as to communicate with the upper part of the first treatment tank 81 from the line 14. The large bubble discharge pipe 15 whose lower end is connected to the upper portion of the large bubble separator 14 is configured such that the upper end thereof opens near the processing liquid surface position 61. The large bubble separator 14 evacuates large bubbles that occur without stopping, but is not pressurized and the upper part is in an open state, and does not affect the fine bubbles discharged from the large bubble separator 14 to the first treatment tank 81. It is like that.

  The first treatment tank 81 is provided with a discharge pipe 68 for discharging the liquid to be treated which has been separated and purified by oil and water from the lower part, and a valve 66 is provided in the middle of the discharge pipe 68.

  A pipe 30 constituting the liquid circulation system to be treated is connected to the bottom of the first treatment tank 81, and has a valve 36 in the middle of the pipe 30 and connected to the first pump 31 via the pipe 32. The outlet side of the first pump 31 is connected to a nozzle 33 provided inside the large bubble separator 14 via a pipe 35 and an air dissolver 39. A pipe 37 connecting the first pump inlet pipe 32 is provided in the pipe 35 at the outlet of the first pump 31, and a valve 38 is provided in the middle.

  An air supply pipe 51 for introducing air is connected to the pipe 32 via a valve 52, and further, a supply pipe 23 constituting a system for introducing the liquid to be processed from the liquid tank 18 to be processed is connected. The supply pipe 23 is provided with a valve 22.

  Further, a bubble generating cylinder 16 is provided below the second processing tank 82 of the processing tank 11, and a nozzle (second nozzle) 47 for discharging the liquid to be processed is provided inside the bubble generating cylinder 16. A pipe 42 constituting a second processing liquid circulation system is connected to the bottom of the first processing tank 81, and is connected to the second pump 41 via a valve 44 provided in the middle of the pipe 42. The outlet side of the pump 41 is connected to a nozzle 47 provided inside the bubble generating cylinder 16 through a pipe 43. The pipe 43 at the outlet of the second pump 41 is provided with a pipe 45 that connects the pipe 42 at the inlet of the second pump, and a valve 46 is provided in the middle of the pipe 45.

  The second treatment tank 82 is provided with a discharge pipe 68 for discharging the cleaned liquid to be treated from below, and this discharge pipe 68 is connected to a discharge pipe 67 from the first treatment tank 81, and its position Is upstream of the valve 66. An oil discharge pipe 63 for discharging the oil 64 is provided at the bottom of the floating oil receiver 83. Note that the supply pipe 23 may be connected to the lower portion of the first processing tank 81 and a pump may be installed in the middle thereof to supply the liquid to be processed directly to the first processing tank 81.

  Next, the operation will be described. The oil / water separator 10 in FIG. 1 supplies the first treatment tank 81 and the second treatment tank 82 with a certain amount of liquid to be treated, and performs the treatment by the intermittent operation method of discharging after performing the oil / water separation treatment.

  First, the first pump 31 is operated in a state in which fresh water or treated liquid is supplied to the upper end of the large bubble separator 14 in the first treatment tank 81 of the treatment tank 11. At this time, the valve 36 is open, and the valve 38 is adjusted so that the outlet pressure of the first pump 31 becomes a predetermined value. When this operation is performed, the fresh water or the treated liquid inside the first treatment tank 81 is pumped up from the pipe 30 by the first pump 31, passes through the pipes 32 and 35 and the air dissolver 39, and then from the nozzle 33 to the large bubble separator 14. The first liquid to be processed (first circulation system) is returned to the first processing tank 81 and discharged.

  Subsequently, while operating the first liquid circulation system, the opening degree of the valve 36 is adjusted so that the inlet pressure of the first pump 31 becomes a predetermined value of negative pressure. Then, when the valve 22 of the processing liquid supply system is opened, the processing liquid is supplied to the first processing tank 81 through the first pump 31, the pipe 35, the air dissolver 39, and the nozzle 33, It is also supplied to the second treatment tank 82 through the upper part. When the liquid level gauge 71 detects that the liquid level position 61 to be processed has reached a predetermined position, the valve 22 is closed and the supply of liquid to be processed is terminated.

  Next, when the valve 52 provided in the middle of the air supply pipe 51 having a negative pressure is opened, air is sucked, so that the valve opening is adjusted so as to be a predetermined amount. The inflowed air is mixed with the liquid to be processed flowing in the pipe 32, and a part of the air is dissolved in the liquid to be processed in the process of being pressurized by the first pump 31. The undissolved air is mixed in the air dissolver 39 downstream of the first pump 31 to increase the amount of dissolution, and is discharged into the large bubble separator 14 from the nozzle 33 together with the liquid to be treated in which the air is dissolved. To do.

  Since the liquid and gas that have been pressurized by discharging from the nozzle 33 are depressurized, the air dissolved in the water becomes fine bubbles, and a part of the air that could not be completely dissolved becomes fine bubbles, and the rest is It becomes a large bubble. When the air dissolver 39 is provided, the large bubbles become fine due to the internal stirring effect, the contact area between the bubbles and the liquid increases and the residence time increases, so the amount of dissolved air increases and the large bubbles greatly decrease. .

  Next, the liquid to be processed and the air that have exited the nozzle 33 flow while swirling inside the large bubble separator 14, and a reverse flow region is formed by reducing the pressure at the center, and the air is sheared by the liquid to be processed. Due to this effect, some of the large bubbles are crushed and become fine bubbles together with dissolved air. And the fine bubble exists in the 1st process tank 81 whole. When pure water is used as the liquid to be treated, the amount of fine bubbles generated decreases and the fine bubble diameter increases, but the above apparatus becomes opaque and white even when pure water is used. Is 40-50 μm. The bottom of the first treatment tank 81, particularly the lower part than the large bubble separator 14, has a slow downflow rate of the liquid to be treated, so that there are particularly fine bubbles among the fine bubbles present in the first treatment tank 81. To do.

  Next, in the second treatment tank 82, the liquid to be treated containing particularly fine bubbles in the first treatment tank 81 is pumped out from the bottom of the first treatment tank 81 while operating the first treatment liquid circulation system. 42, pressurizing with the second pump 41 without mixing air through the valve 44, and spraying the liquid to be processed into the liquid to be processed in the tank from the nozzle 47 inside the bubble generating cylinder 16 through the pipe 43. The second circulation system (second circulation system) is operated. No air is supplied from the outside during the second circulation system operation.

  In the second circulation system, the liquid to be treated sucked from the first treatment tank 81 uniformly contains fine bubbles, and the amount of dissolved air in the liquid to be treated is large and the residence time in the pipe is short. The microbubbles are hardly dissolved in the liquid to be processed only by pressurization. Then, a negative pressure region is formed in the vicinity of the injection flow by being injected from the nozzle 47 into the liquid to be processed in the second processing tank 82, and the fine bubbles in the injection flow are once expanded, and the pressure is reduced in the downstream portion. The expanded bubbles are compressed by the recovery, and become fine bubbles (10 to 20 μm) having a smaller diameter than the initial one. Therefore, the inside of the second processing tank 82 is filled with smaller fine bubbles than the inside of the first processing tank 81. Fine oil particles that could not be adsorbed in the first treatment tank 81 are adsorbed by these small fine bubbles, and oil separation proceeds by floating.

  When the concentration of the liquid oil to be treated reaches a predetermined value, the valve 52 is closed and the first pump 31 and the second pump 41 are stopped. Then, the valve 66 is opened, the liquid to be processed is discharged until the liquid surface position 61 to be processed reaches the upper surface of the large bubble separator 14, and the first processing operation is completed. The oil separation operation is repeated in the same procedure after the second time. When this operation is repeated, the floating oil accumulates in the upper portion, and the difference between the floating oil surface position 62 and the liquid surface position 61 to be treated increases. By continuing the supply of the liquid to be processed until the processing liquid surface position 61 becomes the same height as the shielding plate 12, the floating oil overflows the shielding plate 12 and flows out to the floating oil receiving portion 83. The separated oil component 64 is recovered from the pipe 63.

  This discharge time can be determined not only by the operation time but also by measuring the amount of floating oil and the thickness of the floating oil.

  Next, the to-be-processed liquid flow state and oil separation function in the 1st processing tank 81 and the 2nd processing tank 82 are demonstrated using FIG. The liquid to be processed sprayed from the nozzle 33 flows from the large bubble separator 14 together with the fine bubbles into the lower portion of the first treatment tank 81. Since the fine bubbles have a density lower than that of the liquid to be treated, they float up. At this time, the liquid to be treated also rises as an accompanying flow. If an upward flow exists, a downward flow having the same flow rate is formed in the first treatment tank 81.

  On the other hand, the liquid to be processed flows from the second processing tank 82 into the upper portion of the first processing tank 81, and the pipe 30 that sends the liquid to be processed to the first pump 31 at the bottom of the first processing tank 81 and A pipe 42 for sending the liquid to be processed to the second pump 41 is connected, and the liquid to be processed is continuously sent. Therefore, a downward flow toward the bottom is formed in the first treatment tank 81. In order to realize oil levitation separation by fine bubbles, it is necessary to prevent the fine bubbles to which the oil particles have adhered from floating once and then returning to the bottom of the first treatment tank 81 by the downward flow. It is preferable that the bottom area of the first treatment tank 81 is formed to be larger so that the flow speed is slower than the rising speed of the fine bubbles.

  However, since the diameter of the fine bubbles is not uniform, fine bubbles smaller than the average are likely to descend by the downward flow, and the oil adsorption performance is high but the floating separation performance is low. Therefore, in the first treatment tank 81, oil is floated and separated by utilizing fine bubbles larger than the average.

  The liquid to be processed sprayed from the nozzle 47 flows into the lower portion of the second processing tank 82 from the bubble generating cylinder 16 together with the fine bubbles at a low speed. In the second treatment tank 82, the liquid to be treated is discharged from the upper part of the partition wall 13 to the first treatment tank 81. For this reason, the liquid to be processed flows gently from the lower part to the upper part in the second treatment tank 82, and the density of the fine bubbles is smaller than that of the liquid to be processed. Ascend at a fast speed. Thus, since the inside of the second treatment tank 82 is a gentle flow in one direction, there is almost no downward flow, and the rising speed of the fine bubbles necessary for the floating separation of oil is set equal to or higher than that of the first treatment tank 81. can do. Since there is almost no downward flow, the bottom area may be small.

  As a result, oil particles can be levitated and separated at high speed in the second treatment tank 82 by utilizing very fine bubbles that easily adsorb fine oil particles.

  The oil separation characteristics of this example and the conventional example will be described with reference to FIG. The vertical axis represents logarithmic oil concentration, and the horizontal axis represents processing operation time. The initial oil concentration of the liquid to be treated in the treatment tank 11 is A, and as shown by the broken line in the conventional example, the oil concentration B can be separated almost linearly with respect to the processing operation time. However, when the oil concentration is lowered, the residual oil particle diameter is reduced, and it becomes difficult to adsorb the fine bubbles having a large diameter, and the rate of decrease in the oil concentration is reduced. As a result, the processing operation time for separation to the oil content concentration C of the drainage standard is T1.

  In this embodiment, as shown by the solid line, the oil concentration can be separated almost linearly from the initial oil concentration A to the oil concentration B or less, and the oil concentration reduction rate when the oil concentration C is separated to the drainage standard is not reduced. The processing operation time can be separated at T2, which is shorter than the conventional method. This is because the residual oil having a relatively large particle size is separated from the oil concentration A to the vicinity of B, and the residual oil having a smaller particle size is efficiently separated after B.

1 is an overall system diagram of an oil / water separator according to an embodiment of the present invention. It is a flow state figure in a processing tank of an oily water separator similarly. It is an oil separation characteristic figure which compares the Example of this invention, and a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Oil-water separator, 11 ... Processing tank, 12 ... Shielding plate, 13 ... Partition wall, 31 ... 1st pump, 33 ... 1st nozzle, 32, 35 ... Piping, 39 ... Air dissolver, 41 ... 2nd pump , 42, 43 ... piping, 47 ... second nozzle, 81 ... first treatment tank, 82 ... second treatment tank, 83 ... floating oil receiving part, 31, 33, 39 ... first circulation system, 41, 47 ... first Two circulation systems.

Claims (2)

Air is mixed and dissolved in the liquid to be processed to be sent to the processing tank, and the liquid to be processed in which the air is mixed and dissolved is discharged into the liquid to be processed in the processing tank. In an oil-water separator that separates oil and water by levitation of the oil in the liquid to be treated by supplying it to the liquid to be treated,
The treatment tank includes a first treatment tank and a second treatment tank, and includes a first pump that sends a treatment liquid to the first treatment tank, an air dissolver that mixes and dissolves air in the treatment liquid, and air from the air dissolver. A first circulation system comprising a first nozzle for discharging the mixed and dissolved processing liquid into the processing liquid in the processing tank; a second pump for sucking the processing liquid containing bubbles in the first processing tank; An oil-water separator comprising a second circulation system comprising a second nozzle for discharging a treatment liquid into a second treatment tank and supplying fine bubbles.   The oil-water separator according to claim 1, wherein the bottom area of the first treatment tank is larger than the bottom area of the second treatment tank.

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