JP2010247144A - Oil separation tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil separation tank which is in a compact and simple structure and has high oil separation efficiency. <P>SOLUTION: Inside the oil separation tank for separating oil from water to be treated by a specific gravity difference, a porous member through which the water to be treated passes and which arranges the flow, and a partition plate which is disposed on the downstream side of the porous member and has a passing path of the water to be treated formed at the lower end, are provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gravity-type oil separation tank that separates oil from water to be treated by specific gravity difference.

  The drainage water in the hydroelectric power station contains oil such as lubricating oil for machinery. When draining wastewater outside the premises, if it is released while containing oil, it may adversely affect the external natural environment. Therefore, it is necessary to release the oil after separating it. For this reason, the oil separation tank is passed before discharging the waste water, and the oil is floated and separated and collected in the tank to prevent the oil from leaking outside the premises.

  As oil separation tanks used in general industries, there are standards such as the American Petroleum Institute (hereinafter referred to as API). The API-type oil separation tank is a gravity-type oil separation tank that separates oil from water to be treated by specific gravity difference.

  FIG. 10 shows a longitudinal sectional view of a typical gravity oil separation tank. A partition plate 14 is installed in the tank so that the water to be treated passes between the lower end of the partition plate 14 and the tank bottom surface 17. After the water to be treated is injected into the oil separation tank from the inflow port 11, the oil component rises before reaching the partition plate 14, and is collected upstream of the partition plate 14 (oil floating area 13 surrounded by a dotted line). Collected and oil separated. If the oil concentration is high, the treated water is sent to secondary treatment (removal by an oil filter, chemical treatment, etc.) if the oil concentration is high, and is discharged out of the system as it is if the oil concentration is low.

  Although the gravity type oil separation tank has a simple structure, the oil separation efficiency is low. Therefore, when the oil concentration is high, the oil separation tank may be extended to several tens of meters. Therefore, attempts have been made to shorten the separation tank as much as possible.

  For example, an oil separation tank provided with a recirculation line that measures the oil concentration of the treated water that has passed the lower end side of the partition plate in the oil separation tank and circulates it back to the oil separation tank when the oil concentration is high. Yes (see Patent Document 1).

JP 11-197403 A

  However, even if the improvement as in Patent Document 1 is made, the oil separation tank is only about 40% longer than the conventional one, and is still longer than 10 m, and does not enter the narrow hydroelectric power station.

  Moreover, if the oil separation tank of FIG. 10 is extended so as to enter the premises of the hydroelectric power plant, the oil separation efficiency is lowered, and the cost and time for the secondary treatment are increased.

  Furthermore, even if the oil separation efficiency is high, it is not preferable to greatly improve the existing oil separation tank or replace it with an oil separation tank having a complicated separate structure because the equipment cost and the maintenance cost increase. A simple improvement is required for an existing oil separation tank base.

  As described above, an object of the present invention is to provide an oil separation tank having a compact and simple structure and high oil separation efficiency.

  As a result of intensive studies by the inventors in order to solve the above problems, it was found that oil separation efficiency is improved by providing a porous member for rectifying water to be treated on the upstream side of the partition plate, and the present invention is completed. It came to do.

  That is, the present invention is disposed in an oil separation tank that separates oil from the water to be treated by specific gravity difference, a porous member through which the water to be treated passes and regulates the flow thereof, and a downstream side of the porous member. An oil separation tank comprising a partition plate formed with a passage for water to be treated at a lower end.

  The porous member may be a planar object having no depth in the flow direction, such as a wire mesh, or a three-dimensional object having a depth in the flow direction, such as a rectifying grid.

  Here, in the case where the porous member is a planar object, the size of each hole is preferably the same as the substantially minimum particle diameter of the oil contained in the water to be treated. In the case of a three-dimensional object, it is preferable that the size of each hole is sufficiently small as long as it can be manufactured.

  Moreover, it is preferable that at least two of the porous members are arranged at intervals.

  Moreover, it is preferable that the said porous member is arrange | positioned so that it may cover from the tank bottom surface to the water surface of to-be-processed water.

  Moreover, it is preferable that at least two of the partition plates are disposed with a space therebetween. Under the present circumstances, it is preferable to add the submerged board erected so that the upper end may become higher than the position of the lower end of a partition plate in the tank bottom face between the said partition plates.

  Furthermore, it is desirable that the porous member has an oil adsorption effect.

  According to the present invention, with a simple structure in which a porous member for rectifying water to be treated is provided on the upstream side of the partition plate, even in a compact oil separation tank, the oil content in the water to be treated can be efficiently obtained. Can be separated.

It is a longitudinal cross-sectional view of the oil separation tank concerning the 1st Embodiment of this invention. It is explanatory drawing of the rectification | straightening effect | action by the porous member in the 1st Embodiment of this invention. It is a block diagram of an example of the porous member different from FIG. 1 in the 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the oil separation tank at the time of using a rectification | straightening grid as a porous member of a kind different from FIG. 1 in the 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the oil separation tank concerning the 2nd Embodiment of this invention. 3 is a line graph showing the relationship between the opening area ratio of the wire mesh (porous member) and the oil separation efficiency in Example 1. FIG. 6 is a line graph showing the relationship between the number of wire meshes (porous members), the number of partition plates, the presence / absence of a submerged plate, and oil separation efficiency in Example 2. 6 is a longitudinal sectional view of an oil separation tank in Example 3. FIG. 6 is a graph of separation efficiency in an oil separation tank in Example 3. It is a longitudinal cross-sectional view of the gravity-type oil separation tank in a prior art example.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated in detail, referring an accompanying drawing below. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified.

[First Embodiment]
FIG. 1 is a longitudinal sectional view of an oil separation tank according to the first embodiment of the present invention. This oil separation tank is a gravity-type oil separation tank that separates oil from the water to be treated by a specific gravity difference, and a porous member 12 through which the water to be treated passes and adjusts the flow thereof, and the porous member 12 And a partition plate 14 formed with a passage 15 for water to be treated at the lower end. FIG. 1 shows a case where a planar object is used as the porous member. When a three-dimensional object is used as the porous member, the longitudinal sectional view of FIG. 4 is obtained. Since the action of the porous member is the same mechanism in any case, the description will be made with reference to FIG. 1 unless otherwise specified.

  Here, the water to be treated includes a wide range of waste water including oil regardless of the oil concentration. For example, drainage from the hydroelectric power station premises.

  Next, the flow of the water to be treated in the oil separation tank according to this embodiment (solid arrow in FIG. 1) will be described. First, the water to be treated is injected from the inlet 11 to the upstream side in the oil separation tank. Next, the water to be treated passes through the passage 15 formed by the lower end of the partition plate 14 and the tank bottom surface 17 after being rectified by passing through the inside of the porous member 12. At this time, the oil component having a small specific gravity floats (dotted line arrow in FIG. 1) and is collected upstream of the porous member 12 and the partition plate 14 (oil floating region 13 surrounded by the dotted line in FIG. 1), and the oil component is separated. Is done. The treated water that has passed through the passage 15 is discharged from the downstream side through the drain port 16 to the outside of the system.

  Next, the operation of the porous member 12 will be described. The porous member 12 itself acts as an oil filter to separate the oil component, to adjust the flow of water to be treated in the region surrounded by the porous member 12, and to make the oil component easily float, and to the downstream side of the porous member 12 It has the effect | action which produces | generates the area | region where a flow stays in and collects oil.

  First, the action of the porous member 12 itself acting as an oil filter to separate oil will be described. Not only does the oil component pass through the porous member 12, but if the pore diameter is sufficiently small, the oil component is adsorbed on the porous member 12, or dammed up so that the oil component floats upstream of the porous member and can be separated. As a result, since the amount of oil separation increases, the separation efficiency of the entire oil separation tank can be improved.

  Next, with reference to FIG. 2, the effect | action which arranges the flow of to-be-processed water in the area | region enclosed by the porous member 12, and makes it easy to float an oil component is demonstrated. 2A is an explanatory diagram of the flow of the water to be treated when the porous member 12 is not present, and FIG. 2B is an explanatory diagram of the flow of the water to be treated when the porous member 12 is present. As shown in FIG. 2A, the flow of water to be treated in the absence of the porous member 12 passes through a region close to the tank bottom surface 17 as shown by the solid arrow in FIG. The flow passing through the passage 15 at the lower end of 14 is the mainstream. In this case, much of the oil component passes through the passage 15 as it is on the mainstream. On the other hand, as shown in FIG. 2 (b), when the porous member 12 is provided, the flow of water to be treated in the region surrounded by the porous member 12 increases as shown by the solid line arrow in FIG. 2 (b). It becomes a horizontal flow with uniform flow velocity in the vertical direction. When there is no porous member 12, there is no flow in which the oil component has been pushed down the tank, so that the oil component easily floats in this region.

  Next, the effect | action which produces | generates the area | region where a flow stays in the downstream of the porous member 12, and collects oil is demonstrated. On the downstream side of the porous member 12, the flow is concentrated toward the passage 15. In the region deviated from the flow (the region indicated by hatching in FIG. 2B), the flow velocity is almost zero. If oil reaches this area, it floats and is collected without being swept away.

  Therefore, by providing the porous member 12 to exert these effects, the oil separation efficiency can be improved while maintaining a constant oil treatment amount even in a compact oil separation tank.

  In addition, it is preferable that the porous member 12 is disposed so as to cover from the tank bottom surface 17 to the surface of the water to be treated so that these functions can be exhibited.

  The size (pore diameter) of each hole of the porous member 12 is preferably smaller. This is because a smaller pore diameter of the porous member 12 increases the amount of oil adsorbed on the porous member 12, increases the rectification effect of the water to be treated, and increases the oil separation efficiency.

  However, if the pore diameter of the porous member 12 is too small, the oil may be adsorbed too much on the porous member 12 to cause clogging. Furthermore, the oil in the water to be treated that has passed through the porous member 12 becomes fine and difficult to float, and separation may be difficult. Therefore, it is particularly preferable that the size of each hole of the porous member 12 is the same as the substantially minimum particle size of oil. By setting it as the size of such a hole, the flow rate of to-be-processed water, the oil adsorption amount to the porous member 12, and the grade of the foaming of an oil component can be made into an appropriate range.

  As described above, the porous member 12 may be a planar object or a three-dimensional object. Hereinafter, details of the planar porous member and the three-dimensional porous member will be described.

  Examples of the planar porous member 12 include a wire mesh and other pore filters, but a wire mesh is preferable because of its low price and easy availability and handling. The metal mesh is preferably made of stainless steel to prevent rust. In order to obtain an appropriate rectifying effect, the size of each opening of the wire net is preferably 40 to 80 mesh expressed by the number of meshes (number of openings per inch).

  Here, the number of planar porous members 12 is not limited to two as shown in FIG. 1, but may be three or more. This is because increasing the number of planar porous members 12 increases the rectification effect and improves the oil separation efficiency. However, if the number of planar porous members 12 is too large, the oil separation efficiency tends to decrease, and there is an optimal number that maximizes the oil separation efficiency. In general, the number of planar porous members 12 is preferably 2 to 3.

  Further, the planar porous member 12 needs to be arranged with an interval of a certain length (for example, 100 mm) or less. This is because if this arrangement interval is wide, a sufficient rectifying effect cannot be obtained even if the number of sheets is increased.

    Here, the case where a metal mesh is used as the planar porous member 12 has been described, but instead of the metal mesh, a rectifying mesh made of lipophilic fibers such as polypropylene is used as the planar porous member 12, and the oil content is reduced. You may make it improve the effect | action to isolate | separate. That is, when the net material is made of lipophilic fibers, the net has an oil adsorbing effect in addition to the rectifying effect, and the separation efficiency of the oil separation tank is further improved.

  Further, when a metal mesh is used as the planar porous member 12, the action of separating the oil component may be improved by coating the metal mesh with an oil adsorbing material. That is, by coating the wire mesh with the oil adsorbing material, the wire mesh has an oil adsorbing effect in addition to the rectifying effect, and the separation efficiency of the oil separation tank is further improved.

  An example of the three-dimensional porous member 12 is a rectifying grid as shown in FIG. FIGS. 3A and 3B are configuration diagrams of the three-dimensional porous member 12 formed of a rectifying grid. FIG. 3A is a perspective view, and FIG. 3B is an enlarged view of a portion X in FIG. As shown in FIG. 3, the rectifying grids are formed in a grid shape, and each grid forms a water channel 19 having a depth d in the flow direction of the water to be treated. Accordingly, the water channel 19 is formed in multiple stages in the vertical and horizontal directions.

  FIG. 4 is a longitudinal sectional view of an oil separation tank when a rectifying grid is used as the three-dimensional porous member 12. A three-dimensional porous member 12 that is a rectifying grid is disposed inside the oil separation tank. First, the water to be treated is injected from the inflow port 11 to the upstream side in the oil separation tank, and the water to be treated flows into the water channel 19 of the three-dimensional porous member 12 using a rectifying grid. Thereby, after being rectified by the grid-like water channel 19, it passes through the passage 15 formed by the lower end of the partition plate 14 and the tank bottom surface 17. At this time, an oil component having a small specific gravity rises (dotted arrow in FIG. 4) and is collected on the upstream side of the three-dimensional porous member 12 and the partition plate 14 (oil floating region 13 surrounded by a dotted line in FIG. 4). The oil is separated. The treated water that has passed through the passage 15 is discharged from the downstream side through the drain port 16 to the outside of the system.

  The action of the three-dimensional porous member 12 is the same as that of the planar porous member. However, in the case of the planar porous member, the flow of water to be treated is adjusted in the region surrounded by the porous member. In the case of a three-dimensional porous member, the difference is that the water to be treated is arranged in the water channel 19 inside the porous member.

  In addition, when a wire mesh or a pore filter is used as the planar porous member 12, it is desirable to use a plurality of porous members 12 in order to obtain a rectifying effect. In the case of use, a sufficient rectifying effect can be obtained with one porous member 12 by appropriately selecting the size of the depth d. Needless to say, a plurality of rectifying grids may be used as the three-dimensional porous member 12 instead of selecting the depth d.

  Next, the partition plate 14 will be described. The partition plate 14 has a role of blocking the flow on the water surface side of the water to be treated that has passed through the porous member 12 and allowing the water to be treated to flow through the passage 15 on the bottom surface side of the tank. This is because the oil component floats in the water to be treated and collects in the vicinity of the water surface, so that the oil component does not flow downstream by blocking the flow on the water surface side.

  According to the first embodiment, a simple structure in which the porous member 12 for rectifying the water to be treated is provided on the upstream side of the partition plate 14 enables high efficiency even in a compact oil separation tank. The oil in the treated water can be separated.

[Second Embodiment]
FIG. 5 is a longitudinal sectional view of an oil separation tank according to the second embodiment of the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in that one partition plate 14 is added to keep two intervals, and a diving plate 18 is newly provided therebetween. FIG. 5 shows a case where a planar object is used as the porous member. When a three-dimensional object is used as the porous member, one partition plate 14 is added to the longitudinal sectional view of FIG. It becomes a shape (the figure is omitted) in which a diving plate 18 is newly provided between them.

  The number of the partition plates 14 is not limited to two as shown in FIG. 5, but may be three or more. This is because by increasing the number of the partition plates 14, the oil floating region 13 (region surrounded by the dotted line in FIG. 5) can be widened, and the oil separation efficiency can be improved.

  When two or more partition plates 14 are provided, it is preferable to provide a diving plate 18 between the partition plates 14. The diving plate 18 is a plate erected on the tank bottom surface 17 between the partition plates 14 so that the upper end thereof is higher than the position of the lower end of the partition plate 14. The diving plate 18 has a role of changing the flow of the water to be treated that has passed through the lower end side of the partition plate 14 to the upper side so that the oil can easily float upward.

  According to the second embodiment, by optimizing the number of the partition plates 14 and adding the diving plate 18, in addition to the effects of the first embodiment, the oil separation efficiency can be further increased.

  The test which changed the conditions of the oil separation tank as an Example was done, and the separation efficiency was compared. The extension of the longitudinal section of the water tank used here was 1000 mm, and the water to be treated was poured therein so that the water surface height was 400 mm. While injecting water at a flow rate of 38 L / min as water to be treated, 10 g of fine particles simulating oil droplets were simultaneously introduced into the oil separation tank. As the fine particles, phylite fine particles having a specific gravity of 0.70 and a diameter of 75 to 90 μm were used.

  As the porous member 12, a commercially available wire mesh (manufactured by SUS304, wire diameter 0.18 to 0.29 mm, 14 to 80 mesh) was used, and the entire water surface was covered from the tank bottom surface 17 by this wire mesh.

  The separation efficiency was calculated by the formula (1). Here, the “mass of fine particles floating in the oil levitation zone” and the “total mass of charged fine particles” in the denominator include the mass of fine particles that could not be collected due to precipitation at the bottom of the water tank. Not.

[Formula 1]
Separation efficiency = mass of fine particles floating in oil floating area / total mass of charged fine particles (Formula 1)
[Comparative Example]
In the comparative example, as shown in FIG. 10, an oil separation tank provided with only one partition plate 14 without using a wire mesh (porous member 12) was used. The partition plate 14 was disposed at a position 600 mm away from the tank end surface in the horizontal direction, and the height of the passage 15 at the lower end of the partition plate was 50 mm.

[Example 1]
In Example 1, an oil separation tank provided with one metal mesh (porous member 12) and one partition plate 14 was used (the number of porous members 12 in FIG. 1 is one). The wire mesh was placed at a position 100 mm away from the end face of the water tank in the horizontal direction, and other conditions were the same as in the comparative example.

  FIG. 6 is a line graph showing the relationship between the opening area ratio of the wire mesh (porous member 12) and the separation efficiency in Example 1. The opening area ratio was determined from the ratio between the opening of the wire mesh and the total area of the wire mesh. Note that data D0 with an opening area ratio of 100% is a result of a comparative example in which no wire mesh is provided. From the line L1 in FIG. 6, comparing the comparative example without the wire mesh (data D0) and Example 1 with the wire mesh (data D1 to D6), it can be seen that the separation efficiency is improved by inserting the wire mesh. Furthermore, when comparing cases with a wire mesh, it can be seen that a wire mesh having a smaller opening area ratio (large mesh) improves the separation efficiency. In the data D6 (mesh 80, opening area ratio 19%) having the highest separation efficiency, the width of each opening of the wire mesh was about 140 μm, which was close to the particle size of the fine particles.

[Example 2]
FIG. 7 is a line graph showing the relationship between the number of wire meshes (porous members), the number of partition plates, presence / absence of a submerged plate, and oil separation efficiency in Example 2. In the line L2 of FIG. 7, the number of the wire mesh is changed from 1 to 4 with the partition plate 14 being one (data D6 to D9). The wire mesh having the smallest aperture area ratio (mesh 80) used in Example 1 was used, and the second and subsequent wire meshes were arranged on the downstream side of the first wire mesh so that the interval was 100 mm. Other conditions are the same as in the first embodiment. Note that the data D0 for the number of wire meshes of 0 is the result of the comparative example described above.

  It can be seen from the line L2 in FIG. 7 that the separation efficiency is maximized when there are two metal meshes (data D7). However, in a test using a wire mesh having a larger opening area ratio (for example, mesh 40), the separation efficiency may be maximized when the number of wire meshes is three. The optimal number of wire meshes varies depending on the specifications of the wire mesh and the state of the water to be treated, and two are not necessarily optimal.

  Data D10 in FIG. 7 is a result of testing under the condition that the number of partition plates 14 is increased to two under the condition of two metal meshes and the diving plate 18 is installed between the partition plates 14 as shown in FIG. The second partition plate 14 was installed on the downstream side of the first sheet so that the distance was 300 mm (the horizontal distance from the tank end surface was 900 mm). The diving plate 18 was installed at the intermediate position (horizontal distance from the tank end surface 750 mm), and the length (wrap length) from the upper end of the diving plate to the lower end of the partition plate was 200 mm. Other conditions are the same as those in the data D7. It can be seen that the separation efficiency of the data D10 is increased by about 5% compared to the data D7. Therefore, the separation efficiency can be further improved by increasing the partition plates 14 and adding the diving plates 18. As a result, the separation efficiency was improved by 40% or more in the data D10 of Example 2 compared to the data D0 of the comparative example.

Example 3
Next, an oil separation tank as shown in FIG. 8 was prepared. That is, two metal meshes as the porous member 12, one partition plate 14, and an oil separation tank with an extension of 1000 mm are prepared, and the first metal mesh and the side wall of the oil separation tank on the inlet 11 side are provided. The distance between the two metal meshes was 100 mm, the partition plate 14 was positioned 600 mm from the side wall of the oil separation tank on the inlet 11 side, and the passage 15 of the partition plate 14 was 50 mm. The wire mesh is 80 mesh with a wire diameter of 0.18 mm. Then, while injecting 32.3 L / min of water from the inlet 11, 100 mL of actual turbine oil was simultaneously injected instead of the phylite fine particles.

  And the actual oil of the oil floating area 13 was collect | recovered, and the separation efficiency was calculated | required by (1) Formula. The result is shown in FIG. 9 together with a comparative example in which two metal meshes are not provided.

  As shown in FIG. 9, when no wire mesh is provided, the separation efficiency is about 75%, but when two wire meshes are provided, the separation efficiency is improved to about 92%.

DESCRIPTION OF SYMBOLS 11 ... Inlet, 12 ... Porous member, 13 ... Oil floating area, 14 ... Partition plate, 15 ... Passage passage, 16 ... Drain port, 17 ... Tank bottom surface, 18 ... Submerged plate, 19 ... Water channel

Claims (7)

A porous member in which the water to be treated passes and regulates its flow inside the oil separation tank that separates the oil component by specific gravity difference from the water to be treated;
An oil separation tank, comprising a partition plate disposed downstream of the porous member and having a passage for water to be treated formed at a lower end thereof.   2. The oil separation tank according to claim 1, wherein each of the porous members has the same pore size as a substantially minimum particle size of oil contained in the water to be treated.   The oil separation tank according to claim 1 or 2, wherein at least two of the porous members are arranged at intervals.   4. The oil separation tank according to claim 1, wherein the porous member is disposed so as to cover from a tank bottom surface to a water surface of water to be treated.   5. The oil separation tank according to claim 1, wherein at least two of the partition plates are arranged with a space therebetween.   The oil separation tank according to claim 5, further comprising a submerged plate erected on the bottom surface of the tank between the partition plates so that an upper end thereof is higher than a position of a lower end of the partition plate.   The oil separation tank according to claim 1, wherein the porous member has an oil adsorption effect.

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