Coalescer system and oil water separator

Abstract

The present invention prevents a decrease in the degree of oil-water separation over time caused by bypass flow of a liquid to be treated due to deterioration of a peripheral section of the coalescer for oil-water separation.　Pressure is applied only to the peripheral section of a coalescer 2 in contact with the inner wall of a housing container 11 in a oil-water separation treatment tank 1, thereby maintaining the pressure on the peripheral section higher than in the central section. In order to form a pressure gradient, a recess 31 parallel to the flow path direction is provided on the bottom surface of a porosity difference generation section 3, and pressing sections 32 are disposed on both sides of the recess 31. As a result, the liquid to be treated bypasses the deteriorated peripheral section and selectively flows only through the central section with less deterioration, thereby preventing a decrease in oil-water separation performance.

Description

Coalescer system and oil-water separator

[0001] The present invention relates to a coalescer system used for wastewater treatment and the like, and an oil-water separation apparatus equipped with the coalescer system.

[0002] Conventional coalescers used for wastewater treatment, etc., are composed of a packed bed made of resin fibers and are installed in the flow path of the liquid to be treated. They capture oil droplets in the liquid, causing them to aggregate and coarsen. The coarsened oil droplets tend to float and escape from the coalescer. This separates the oil from the water.

[0003] However, oil droplets trapped and coagulating in the packed bed increase the pressure loss during the flow of the treated liquid, which results in an increase in the driving energy required to move the treated liquid.

[0004] Furthermore, when capturing and agglomerating oil in a packed bed, at low flow rates, oil droplets may bypass the packing and escape by bypassing the voids. In this case, the oil droplets are discharged from the system without being coarsened, and the coalescer does not function properly. Therefore, in order to achieve high-precision separation using a coalescer using conventional technology, it is necessary to increase the flow rate to prevent oil droplets from bypassing the packing, and to use the inertial effect to make the droplets collide with the packing. This increases the pressure loss of the flow and the energy required to drive the coalescer.

[0005] In order to solve the above problems, Patent Document 1 proposes a coalescer that is composed of an assembly of sheet-like metal meshes, and the direction of the surfaces of the metal meshes is oriented in the same direction as the flow direction of the liquid to be treated.

[0006] That is, according to the invention of Patent Document 1, oil droplets in the treated liquid are quickly coalesced and coarsened without coagulating due to the oil film formed along the metal mesh layer extending in the direction of flow of the treated liquid. This reduces pressure loss and saves the driving energy required for flow. Furthermore, because the oil droplets move as an oil film and do not coagulate, clogging can be avoided, thereby suppressing the occurrence of clogging and significantly reducing the maintenance burden.

[0007] Japanese Patent Application Laid-Open No. 2021-602

[0008] However, the diameter of the oil droplets targeted by this invention is on the order of micrometers. Therefore, in order to capture oil droplets without gaps, the mesh must have high dimensional accuracy on the order of nanometers and dimensional stability to maintain that accuracy. However, due to the flexible structure of the mesh, it is difficult to simultaneously achieve and maintain such high dimensional accuracy and dimensional stability, which makes it unsuitable for industrial production processes. Furthermore, high pressure is continuously applied to the side walls of the mesh-filled section, causing the packing to deform over time, resulting in "sag." This deformation can create gaps, resulting in bypass flow, which can lead to a decrease in oil-water separation efficiency over time.

[0009] Furthermore, in Patent Document 1, the entire mesh layer is pressed uniformly from the top surface of the mesh layer, resulting in a flow toward the periphery. Therefore, if there are gaps in the side of the mesh, the liquid to be treated will flow into those gaps, causing a flow that does not pass through the mesh layer, preventing the oil droplets contained in the liquid from coarsening and resulting in a decrease in separation efficiency. In contrast, in the present invention, by creating a situation in which the porosity of the peripheral portion of the mesh layer is lower than that of the central portion, the flow resistance in the central portion is lower than that of the peripheral portion, and flow toward the periphery is suppressed. In other words, the present invention has been made to address the above-mentioned problems, and its purpose is to effectively prevent a decrease in oil-water separation efficiency over time while maintaining a simple mechanism by preventing bypassing flow through gaps that tend to occur, particularly in the side walls of the mesh-filled portion.

[0010] To achieve this objective, the coalescer system of the present invention comprises a coalescer made of laminated sheet-like meshes that is placed in the flow path through which the liquid to be treated passes, and a porosity difference generating section that generates a difference in the porosity of the flow path in a direction perpendicular to the flow path within the surface of the mesh layer of the coalescer, so that the porosity of the flow path at the periphery of the coalescer is lower than the porosity of the flow path at the center.

[0011] The void ratio difference generating section is a piston-shaped pressing member that presses the coalescer perpendicularly against the surface formed by the mesh, and a recess is formed in the center of the lower surface of this pressing member along the flow path direction.

[0012] Furthermore, the piston-shaped pressing member is configured to gradually decrease the void ratio of the flow path from the center toward both ends of the flow path.

[0013] The piston-shaped pressing member has slanted sides on both sides of the recess.

[0014] Furthermore, the porosity difference generating portion is made of an elastic body, and is configured so that the thickness of the elastic body in the peripheral portion is greater than the thickness of the elastic body in the central portion.

[0015] The coalescer is an assembly of laminated sheet-like resin or metal mesh members.

[0016] Furthermore, the mesh member has meridian members and weft members that intersect with the meridian members.

[0017] The sheet-like coalescer is an assembly of laminated mesh members made of resin or metal, and the mesh members have meridian members and weft members intersecting the meridian members.

[0018] The porosity difference generating portion has a sponge structure around the flow path.

[0019] Furthermore, the oil-water separation device of the present invention comprises a treated liquid supply tank, a pump, an oil-water separation treatment tank, and a treated liquid recovery tank, and the oil-water separation treatment tank is equipped with any of the coalescer systems described above.

[0020] That is, the coalescer system of the present invention comprises an assembly of stacked sheet-like meshes installed in a flow path for the liquid to be treated, the assembly having a mesh surface oriented in the same direction as the flow direction of the liquid to be treated, and a pressurizing means for pressurizing the assembly in a direction perpendicular to the mesh surface, thereby generating high pressure in the peripheral areas along the flow path of the coalescer, thereby increasing the flow resistance in the peripheral areas compared to the central area. Furthermore, the porosity difference generating section has pressurized portions on opposing outer peripheries of the assembly from a direction perpendicular to the mesh surface of the assembly, and the pressurized portions are parallel to the flow direction of the liquid to be treated, with both the inlet and outlet sides of the liquid to be treated open. As a result, the liquid to be treated preferentially flows through the central area, preventing the occurrence of bypass flow.

[0021] In addition, a piston-shaped pressing member is used in the void ratio difference generating section to press the coalescer, and a recess is provided in the center of the underside of the pressing member along the flow path, allowing the contact pressure between the pressing member and the coalescer to be locally adjusted. Furthermore, the slanted shape of the pressing member makes it possible to gradually increase the pressure gradient from the periphery of the coalescer toward both ends.

[0022] Furthermore, because the pressing member is made of an elastic material, the peripheral portion deforms more than the central portion, allowing for stronger pressing force to be applied to the peripheral portion. Furthermore, the use of a sponge structure allows for finer deformation compared to the mesh opening size, and the sponge structure penetrates into the mesh openings, reducing the porosity of those portions, thereby contributing to preventing bypassing flow. The sheet-like coalescer is made of mesh-like members made of resin or metal that have a high affinity for oil, and these layered mesh-like members include meridian and weft members that effectively guide oil droplets into an oil film.

[0023] The oil-water separation system also includes a treated liquid supply tank, a pump, an oil-water separation tank container, and a treated liquid recovery tank. The oil-water separation tank incorporates the aforementioned coalescer system, achieving simple yet highly efficient oil-water separation as a whole.

[0024] 1 is a diagram showing the overall configuration of an oil-water separation apparatus. A cross-sectional view showing the configuration of a coalescer system. A schematic diagram of the flow path of the liquid to be treated in the coalescer system, viewed from above. A front view of a prototype example of a porosity difference generating section of the coalescer system. A measurement diagram showing the relationship between the pressure difference and the degree of oil-water separation by the coalescer system. A cross-sectional view showing the configuration of the coalescer system. A schematic diagram of the flow path of the liquid to be treated in the coalescer system, viewed from above. A bottom view of a prototype example of a porosity difference generating section of the coalescer system. A top view of a prototype example of a porosity difference generating section of the coalescer system. A measurement diagram showing the relationship between the pressure difference and the degree of oil-water separation by the coalescer system. A plan view and a cross-sectional view of a sheet-like mesh used in the coalescer system. A plan view showing oil adhering to the sheet-like mesh used in the coalescer system. A perspective view showing the flow of the treatment liquid into a coalescer formed by stacking sheet-like meshes. A top view and a bottom view showing an example of the operation of the coalescer system.

[0025] 1 includes a coalescer 2 constructed by stacking mesh sheets in an oil-water separation tank 1, and a coalescer system 12 having a porosity difference generating unit 3 that generates a pressure gradient by locally pressing on the coalescer 2. The oil-water separation tank 1 also includes a storage container 11 that functions as its container.

[0026] Reference numeral 4 denotes a supply tank for supplying a liquid to be treated 41 containing oil 61. The liquid to be treated 41 is produced as wastewater from petroleum plants, food factories, etc. Oil droplets 44 schematically represent the oil 61 contained in this liquid. A pump 5 supplies the liquid to be treated 41 to the oil-water separation treatment tank 1.

[0027] The liquid to be treated 41 supplied by the pump 5 is treated in the oil-water separation treatment tank 1, and then separated into oil 61 and water 62, which are then stored in the recovery tank 6.

[0028] Here, the structure and function of the coalescer 2 will be explained. As shown in the plan view of Figure 11(a), the coalescer 2 is constructed by laminating sheet-like mesh 22 having warp rods 23 and weft rods 24 that intersect with them, and these are arranged orthogonally in a plain weave. Also, as shown in the side view of Figure 11(b), the coalescer 2 is made up of mesh 22 having interlayer portions 25 arranged alternately with mesh layers 26.

[0029] As the material for the mesh 22, metals such as stainless steel can be used, but resin materials that have an affinity for oil 61, particularly polypropylene (PP) and polyethylene (PE), which are excellent at absorbing oil 61, are also suitable. Furthermore, materials that have been subjected to physical or chemical treatments that make it easier to absorb oil 61 by applying an oleophilic coating agent such as a silicone-based or fluorine-based polymer are also suitable.

[0030] Figure 13 is a perspective view of the coalescer 2. The coalescer 2 is formed by stacking and assembling meshes 22. Its external shape is adapted to the flow path 42 of the storage container 11 in the oil-water separation treatment tank 1, and is appropriately formed according to the cross-sectional shape of the flow path. The coalescer 2 shown in Figure 13 has a rectangular parallelepiped shape and is made up of multiple meshes 22. These meshes 22 are stacked and assembled in one direction. The white arrow in the figure indicates the direction in which the liquid to be treated 41 flows.

[0031] In the flow path 42 extending from the inlet surface 2a to the outlet surface 2b of the coalescer 2 in Fig. 1, fine oil droplets 44 in the liquid to be treated 41 come into contact with an oil film 45 formed on the surfaces of the meridian wires 23 and weft wires 24, as shown schematically in Fig. 12. The oil film 45 moves along the meridian wires 23 and weft wires 24, which extend mainly in the flow direction, as the liquid to be treated 41 flows, and subsequent oil droplets 44 come into contact with and coalesce with it. The weft wires 24 also capture oil droplets 44 that do not come into contact with the meridian wires 23, converting them into oil films 45 and promoting coalescence.

[0032] Next, the oil droplets 44 coalesce to form an oil film 45, which moves downstream through the mesh layer 26 and the interlayer portion 25. The oil film 45, which has grown at the lower end of the mesh layer 26, grows further at the ends of the meridian wires 23 and weft wires 24 that make up the outlet surface 2b, and becomes coarse droplets 46. These coarse droplets 46 grow until they can no longer resist the flow of the treated liquid 41, and then leave the coalescer 2 as coarse droplet particles 47.

[0033] The coarse droplet particles 47 that flow out of the oil-water separation treatment tank 1 easily separate from the water and float up in the recovery tank 6. As a result, a layer of oil 61 is formed in the upper layer in the recovery tank 6, and a layer of water 62 remains in the lower layer.

[0034] However, as a result of long-term operation of the oil-water separation device 10, pressure is constantly applied to the part of the coalescer 2 that contacts the storage container 11, and the mesh 22 may become deformed due to "sagging" caused by aging of the packing. When such deformation occurs, a bypass flow occurs, significantly reducing the degree of oil-water separation. As a result, the treated liquid is sent to the recovery tank 6 without sufficient removal of the oil 61, and the performance of the oil-water separation treatment device is reduced.

[0035] The coalescer system 12 of the present invention was provided to improve this situation. Fig. 2 is a schematic cross-sectional view of the coalescer system as viewed from the front. As shown in Fig. 2, the voidage difference generating section 3 is a piston-like device that presses a part of the coalescer 2 to generate a pressure gradient. In this embodiment, only the two ends of the coalescer 2, i.e., the peripheral parts 21 that contact the inner wall of the storage container 11, are pressed, and the pressure in these parts is set higher than in the central part. A recess 31 is provided in the bottom part of the voidage difference generating section 3 along the flow path direction, and protruding pressing parts 32 are formed on both sides of the recess 31.

[0036] 2 is applied to the upper part of the porosity difference generating section 3, the pressure is applied as a step-like pressure gradient to the peripheral section 21 of the coalescer 2 through the pressing section 32, and this pressure gradient causes vertical deformation of the mesh layer 26 in the peripheral section 21 of the coalescer 2. This deformation increases the pressure loss ΔPfp for the inflowing treated liquid 41, and increases the flow resistance in that section.

[0037] As a result, the treated liquid 41 flowing into the coalescer 2 avoids the peripheral portion 21, which has high flow resistance, and selectively flows through the central portion, which has relatively low flow resistance. This prevents the liquid from passing through the peripheral portion 21 of the coalescer 2, where the oil-water decomposition ability has deteriorated, and selectively passes through only the central portion, where the deterioration is small, preventing deterioration of the oil-water decomposition performance of the entire device.

[0038] Figure 3 is a schematic diagram showing the flow path of the treated liquid 41 as seen from above the coalescer 2. In Figure 3, the treated liquid 41 that flows into the oil-water separation tank 1 from below follows the flow path indicated by the white arrows, avoiding the peripheral area 21 of the coalescer 2, where flow resistance is high, and flows concentrated toward the center. In this way, the treated liquid 41 that flows out of the oil-water separation tank 1 has passed only through the center of the coalescer 2, where oil-water separation has been efficiently performed, achieving high oil-water separation efficiency.

[0039] An elastic body such as rubber or elastomer may be used as the material for the porosity difference generating section 3. When an elastic body is used, even if the central section of the pressed coalescer 2 is deformed, the amount of deformation of the peripheral section 21 is relatively large, so that the flow resistance of the peripheral section 21 can be increased, and a flow path can be formed in the central section.

[0040] The pressure increase caused by pressing inside the coalescer 2 is caused by a reduction in the vertical void ratio between the internal meshes. Here, the pressure loss ΔPfc in the central part of the coalescer 2 must be smaller than the pressure loss ΔPfp in the peripheral part 21, and must satisfy the following equation 1. As a result, the relationship between ΔPfp and ΔPfc follows equation 2.

[0041]

[0042]

[0043] The relationship between the void fraction of the flow path and the flow resistance can be estimated using the following equation 3 regarding the pressure drop ΔPf of the fiber-packed bed.

[0044]

[0045] where L [m] is the flow path length of the element, ρ [kg / m3] is the fluid density, μ [m / s] is the flow velocity, ε [-] is the void fraction, gc [kg / m / s2] is the gravitational acceleration, Df [m] is the fiber diameter, and C De [-] represents the effective drag coefficient. C De Various correlation equations have been proposed for N, and the following equation 4 has been disclosed as an example. Re [-] is the Reynolds number based on the effective flow velocity and fiber diameter in the fiber packed bed.

[0046]

[0047] 4 is a front view of a prototype porosity difference generating section 3 for measuring the relationship between pressure and oil-water separation rate. The porosity difference generating section 3 has a central recess 31 located at the bottom end and a pressing section 32 at the peripheral section 21.

[0048] Figure 5 shows the results of an oil-water separation experiment conducted using the prototype coalescer system 12. In this experiment, the relationship between the pressure difference ΔP [kPa] between the peripheral portion 21 and the center portion of the coalescer 2 and the oil-water separation degree E [-] (1 indicates 100% successful separation) was measured. As is clear from the results in Figure 5, by maintaining the pressure difference ΔP between the peripheral portion 21 and the center portion of the coalescer 2 at 40 kPa or more, a separation degree of 99% or more was maintained even about one week after the start of the experiment. This confirms the effectiveness of preventing a decrease in oil-water separation degree due to deterioration of the peripheral portion 21 of the coalescer 2.

[0049] Figure 6 is a schematic cross-sectional view of a coalescer system 12 according to another embodiment of the present invention, as viewed from the front. The difference from Figure 2 is that both sides of a recess 31 provided in the bottom surface of the porosity difference generating section 3 are inclined (slanted) toward the ends. In Figure 6, a recess 31 parallel to the flow path direction is provided in the center of the bottom surface of the porosity difference generating section 3, and slanted pressing sections 33 inclined toward both ends are formed on both sides of the recess 31.

[0050] 6 is applied to the upper portion of the porosity difference generating portion 3, the slanted pressing portion 33 increases the pressure toward both ends of the coalescer 2, making it possible to increase the flow resistance in those portions. In this method, only the ends of the coalescer 2 are initially pressed, preventing the inflow of the treated liquid 41, and allowing a certain amount of inflow in the peripheral portion 21 of the coalescer 2 near the center.

[0051] 7 is a schematic diagram showing the flow path of the treated liquid 41 as seen from above the coalescer 2 of the above embodiment. As shown in FIG. 7, the treated liquid 41 flowing into the oil-water separation treatment tank 1 does not flow into either end of the coalescer 2 but into the center because the pressed portion has a slant shape. However, it is also shown that some of the treated liquid 41 flows into the lower part of the slant portion.

[0052] As a result, the treated liquid 41 does not have to pass through the end of the coalescer 2 where the oil-water separation efficiency has decreased, but flows into the peripheral part 21 close to the central part which has not deteriorated, so that effective oil-water separation can be carried out while avoiding a decrease in the treatment volume.

[0053] Furthermore, by using a resin material such as an elastomer that is capable of elastic deformation for the porosity difference generating section 3, it becomes possible to change the pressing force in stages from the end to the center, and the flow path of the liquid to be treated 41 can be controlled according to the deteriorated area at the end of the coalescer 2. Furthermore, the accuracy of the porosity difference generating section 3 is sufficient on the order of millimeters rather than nanometers, relative to the positioning accuracy of the coalescer 2, which has the advantage that the pressing force on the coalescer 2 can be easily controlled.

[0054] Fig. 8 is a bottom view of a prototype of the porosity difference generating part 3 made of elastomer, which has slanted pressing parts 33 on both sides of the recess 31. Fig. 9 is a top view of the prototype.

[0055] Figure 10 shows the results of an oil-water separation experiment conducted using this prototype. In this experiment, the relationship between the pressure difference ΔP [kPa] and the oil-water separation rate E [-] (1 indicates 100% separation success) was measured while varying the depth d (mm) of the recess 31 and the difference in pressure between the central and peripheral sections 21 (the screw tightening torque values ​​[cNm] between the inlet and outlet sides; the values ​​in parentheses in the figure), which are the values ​​shown in the symbol legend in the figure. As shown in Figure 10, by maintaining the pressure difference ΔP between the peripheral section 21 and the central section of the coalescer 2 at 20 kPa or higher, a high separation rate of 93.4 to 96.0% (average 94.6%) was achieved, confirming that high separation efficiency can be achieved without requiring dimensional accuracy on the nanometer order.

[0056] A sponge-like material that exhibits greater elastic deformation may be used as the material for the porosity difference generating portion 3. In this case, by arranging the sponge-like material so that it enters the mesh openings, it becomes possible to prevent bypass flow by reducing the porosity of the relevant portion.

[0057] Furthermore, the sponge-like member may be configured to be placed on top of the mesh layer in the peripheral portion. In this case, by applying pressure from above to the entire sponge and mesh with a pressurizing unit, the sponge deforms so as to penetrate into the openings of the mesh. With this configuration, the pressure loss when flowing through the relevant portion and the inner part of the mesh satisfies Mathematical Formula 1 (pressure loss standard value). As a result, the liquid to be treated selectively passes through the central portion where the mesh is placed, coarsening the oil droplets contained in the liquid to be treated, achieving a high degree of separation.

[0058] Methods for lowering the porosity of the peripheral area compared to the central area include applying a greater force to the peripheral area than to the central area when compressing the mesh layer, or placing a sponge-like material in the peripheral area that deforms and penetrates into the mesh openings to reduce the porosity. In the present invention, even if gaps exist on the side of the mesh layer, the treated liquid hardly flows into those areas. By selectively passing through the mesh-filled area, the oil droplets in the treated liquid are coarsened, resulting in high separation performance. In fact, high separation performance was achieved, as shown in Figure 10, even though gaps existed on the side of the mesh-filled area of ​​the coalescer shown in Figure 9. This demonstrates that the configuration of the present invention is effective in suppressing the flow of the treated liquid to the peripheral area.

[0059] That is, as shown in Figure 14(a), the mesh layer is arranged so as to contact the inner wall on the inlet side, and as shown in Figure 14(b), pressure is applied from above the mesh layer. As a result, the gap in the relevant part becomes very small. With this configuration, the pressure loss when passing through the relevant part is much higher than when the liquid flows through the mesh layer in the flow path direction. Therefore, the inflow of the liquid to be treated into the relevant part is effectively suppressed.

[0060] REFERENCE SIGNS LIST 1 oil-water separation treatment tank 10 oil-water separator 11 storage container 12 coalescer system 2 coalescer 22 mesh 23 longitudinal wire 24 weft wire 25 interlayer portion 26 mesh layer 3 porosity difference generating portion 31 recess 32 pressing portion 33 slant pressing portion 4 supply tank 41 liquid to be treated 44 oil droplets 45 oil film 46 coarse droplets 47 coarse droplet particles 5 pump 6 recovery tank 61 oil 62 moisture

Claims

1. A coalescer system comprising a coalescer made of laminated sheet-like meshes placed in a flow path through which the liquid to be treated passes, and a porosity difference generating section that generates a difference in the porosity of the flow path in a direction perpendicular to the flow path within the surface of the mesh layer of the coalescer, characterized in that the porosity of the flow path in the peripheral part of the coalescer is lower than the porosity of the flow path in the center part.

2. The coalescer system according to claim 1, characterized in that the void ratio difference generating section is a piston-shaped pressing member which presses the coalescer in a direction perpendicular to the surface formed by the mesh, and a recess is formed in the center of the lower surface of the pressing member along the flow path direction.

3. The coalescer system according to claim 2, wherein said piston-like pressing member gradually reduces the void ratio of said flow passage from the center toward both ends of the flow passage.

4. The coalescer system according to claim 3, wherein said piston-shaped pressing member has slanted sides on both sides of said recess.

5. A coalescer system according to claim 2, characterized in that the void ratio difference generating portion is made of an elastic body, and the thickness of the elastic body in the peripheral portion is greater than the thickness of the elastic body in the central portion.

6. A coalescer system according to any one of claims 1 to 5, characterized in that the coalescer is an assembly in which the sheet-like resin or metal mesh members are laminated.

7. The coalescer system according to claim 6, wherein the mesh member has meridian members and lattice members intersecting the meridian members.

8. A coalescer system according to claim 7, wherein the porosity difference generating section has a sponge structure around the flow path.

9. An oil-water separation device comprising a treated liquid supply tank, a pump, an oil-water separation treatment tank, and a treated liquid recovery tank, wherein the oil-water separation treatment tank is equipped with a coalescer system described in any one of claims 1 to 5.

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