Driving method of solid-liquid separation device and solid-liquid separation device

Abstract

To provide a driving method of a solid-liquid separation device which cleans sand in a storage tank, and to provide the solid-liquid separation device.SOLUTION: A solid-liquid separation device 1 includes: a container 3 which discharges a mixed liquid, in which a ratio of sand is increased by removing a part of a liquid from a sand mixed liquid containing sand, from a discharge port 331; and a storage tank 4 which receives the mixed liquid discharged from the discharge port 331. A driving method of the solid-liquid separation device 1 includes: an inflow step in which the sand mixed liquid is flowed into the container 3; and a discharge / suction step in which a liquid component in the storage tank 4 is suctioned from the discharge port 331 and, at the same time, the mixed liquid is discharged from the discharge port 331 to the storage tank 4. In the discharge / suction step, the liquid component is suctioned from the discharge port 331 and, at the same time, cleaning water is discharged from the discharge port toward the sand piled up at a lower end portion of the storage tank 4.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for driving a solid-liquid separator that separates a liquid from a solid-containing liquid containing solids, and a solid-liquid separator. [Background technology]

[0002] Sewage treatment facilities are equipped with grit basins for removing sand from wastewater and sedimentation basins for removing sludge from wastewater. In the grit basins, sand contained in the wastewater that flows into the grit basin is allowed to settle and collected in a sand collection pit at the bottom of the basin. The collected sand is then pumped up by a sand pump and transported to a solid-liquid separator installed above ground. This solid-liquid separator receives the transported sand-containing water, separates the sand and wastewater from the sand-containing water, and returns the wastewater to the grit basin. The sedimentation basin also collects sludge contained in the received wastewater in a sludge pit at the bottom of the basin. The sludge-containing water collected in the sludge pit is then transported by a sludge pump to a solid-liquid separator installed above the sedimentation basin. The solid-liquid separator installed above the sedimentation basin also receives the transported sludge-containing water, separates the sludge from the sludge, and returns the sludge-containing water to the sedimentation basin. Furthermore, solid-liquid separators for separating liquid from solid-containing liquid are used in facilities other than sewage treatment facilities. Such solid-liquid separation devices include, for example, devices that separate metal powder and the like from water in industrial wastewater, and devices that separate water from sediment and the like that has flowed into a reservoir such as a dam lake. Hereinafter, sand and sludge contained in wastewater, metal powder contained in industrial wastewater, or sediment and the like that flows into a reservoir with water may be collectively referred to as solids. Furthermore, liquids that have solids mixed in them may be collectively referred to as solid-containing liquids.

[0003] A known example of such a solid-liquid separation device includes a container, a storage tank, and a discharge device (see, for example, Patent Document 1). The container in Patent Document 1 is located above the storage tank and is connected to a sand pump located in the settling basin via a sand lifting pipe. The container receives sand-containing water transferred from the settling basin by the sand lifting pump and discharges a concentrated solution, in which the sand concentration relative to the wastewater is higher than that of the sand-containing water, from an outlet provided in the container. The storage tank receives and stores the concentrated solution discharged from the container. An overflow port is provided at the top of the storage tank. Sand and wastewater settle and separate in the storage tank, and the supernatant wastewater is discharged from the overflow port and returned to the settling basin. The discharge device is connected to the bottom of the storage tank and extends diagonally upward from the connected portion. Sand that has settled at the bottom of the storage tank is conveyed diagonally upward by the discharge device while being drained and sent out of the storage tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-21483 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a demand for washing the sand in the storage tank.

[0006] In view of the above circumstances, an object of the present invention is to provide a method for driving a solid-liquid separator that washes sand in a storage tank, and a solid-liquid separator. [Means for solving the problem]

[0007] The method for driving a solid-liquid separator of the present invention, which solves the above-mentioned object, is a method for driving a solid-liquid separator comprising: a container that removes a portion of liquid from a sand-containing liquid containing sand and discharges the mixed liquid having an increased proportion of sand from a discharge port; and a storage tank that receives the mixed liquid discharged from the discharge port, an inflow step of injecting the sand-containing liquid into the container; a discharge / suction step of discharging the mixed liquid from the discharge port into the storage tank while sucking the liquid component in the storage tank through the discharge port, The discharge and suction step is characterized in that it is a step of suctioning the liquid component from the discharge outlet while discharging cleaning water from the discharge outlet toward the sand accumulated in the lower end portion of the storage tank.

[0008] This method for driving a solid-liquid separator may include a pre-injection step that is started before the inflow step and that injects the cleaning water into the storage tank until the water surface in the storage tank faces the discharge outlet.

[0009] The solid-liquid separator of the present invention, which achieves the above object, comprises a container having an inlet into which a sand-mixed liquid containing sand flows, an outlet for discharging a part of the liquid from the sand-mixed liquid, and an outlet for discharging the mixed liquid in which the proportion of sand has increased due to the part of the liquid being discharged from the outlet; a reservoir for receiving the mixed liquid; a discharge port for discharging cleaning water toward the sand accumulated in the lower end portion of the storage tank, the outlet is open into the storage tank, the container has a constricted portion between the inlet and the outlet, in which a cross-sectional area of ​​an internal space defined by an inner peripheral surface of the container is smaller on the outlet side than on the inlet side, The outlet is characterized in that it discharges the mixed liquid into the storage tank while sucking in the liquid components in the storage tank through the outlet. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for driving a solid-liquid separator that washes sand accumulated in the lower end portion of a storage tank, and a solid-liquid separator. [Brief explanation of the drawings]

[0011] [Figure 1]1 is a schematic diagram showing a settling basin in which a solid-liquid separation device corresponding to one embodiment of the present invention is disposed. [Figure 2] 2(a) is a plan view of the container shown in FIG. 1, and FIG. 2(b) is a cross-sectional view taken along the line AA in FIG. 2(a). [Figure 3] 2 is a front view showing the container, the storage tank, and the lower part of the carrying-out device shown in FIG. 1. FIG. [Figure 4] 2 is a right side view showing the container, the storage tank, and the lower part of the carrying-out device shown in FIG. 1. FIG. [Figure 5] 2 is a flowchart showing the operation of the solid-liquid separator shown in FIG. [Figure 6] 1. FIG. 4 is a front view similar to FIG. 3, showing a modification of the solid-liquid separator shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of this embodiment, an example will be used in which the present invention is applied to a solid-liquid separation device to which sand-containing wastewater is transferred from a grit basin. The grit basin is located upstream of a sewage treatment facility to remove sand from wastewater such as sewage or rainwater. The wastewater from which sand has been removed in the grit basin is sent to a downstream sedimentation basin or the like.

[0013] FIG. 1 is a schematic diagram showing a settling basin in which a solid-liquid separator corresponding to one embodiment of the present invention is disposed.

[0014] As shown in FIG. 1, the settling basin 9 in which the solid-liquid separation device 1 of this embodiment is disposed is a basin equipped with a pump well 91, a trough 92, a sand collection nozzle 93, and a sand collection pit 94. Wastewater flows into the settling basin 9 from the right side of the figure. The flowing wastewater slowly flows toward the left side of the figure. As the wastewater flows through the settling basin 9, the sand contained in the wastewater settles toward the bottom of the basin. The pump well 91 is located at the most downstream side of the settling basin 9. The pump well 91 is a portion where the wastewater from which sand has been removed is stored. A lifting pump 911 is installed inside the pump well 91. The lifting pump 911 sends the wastewater stored in the pump well 91 out of the settling basin 9. A lifting pipe 912 is connected to the lifting pump 911. The wastewater sucked by the lifting pump 911 is sent through the lifting pipe 912 to a settling basin (not shown). The sewage pond water level WL1 is also shown in Figure 1. The position of this pond water level WL1 varies in height from the bottom of the trough 92 within a range of, for example, 1 m to 5 m depending on the amount of sewage flowing into the settling basin 9.

[0015] The trough 92 is formed in the center of the pond width direction at the bottom of the pond upstream of the pump well 91. This trough 92 extends along the direction in which the wastewater flows in the settling basin 9. On both sides of the trough 92 in the pond width direction, a pond bottom slope 95 is formed on the bottom of the pond that slopes downward toward the trough 92. The sand contained in the wastewater that flows into the settling basin 9 settles toward the bottom of the pond and slides down the pond bottom slope 95 or is deposited directly in the trough 92.

[0016] The sand collection nozzle 93 is disposed at the upstream end of the trough 92. The sand collection nozzle 93 is supplied with wastewater pumped up from the above-mentioned sedimentation basin (not shown). The wastewater supplied to the sand collection nozzle 93 is discharged from the tip of the sand collection nozzle 93 toward the downstream side of the sedimentation basin 9. The downstream end of the trough 92 is connected to a sand collection pit 94. Sand deposited in the trough 92 is collected in the sand collection pit 94 by the flow of water discharged from the sand collection nozzle 93.

[0017] The sand collection pit 94 is formed between the pump well 91 and the trough 92. The sand collected in the sand collection pit 94 is sent to the solid-liquid separation device 1 by a sand lifting pump 941. The sand lifting pump 941 is located inside the sand collection pit 94 near the bottom of the sand collection pit 94. A sand lifting pipe 942 is connected to the sand lifting pump 941. The sand lifting pump 941 sucks the sand collected inside the sand collection pit 94 together with the wastewater and transfers the sand-mixed wastewater to the container 3 through the sand lifting pipe 942. The sand corresponds to an example of a solid, and the wastewater corresponds to an example of a liquid. Note that the wastewater may also contain impurities such as organic matter. In this embodiment, the wastewater mixed with such impurities may be simply referred to as wastewater. Hereinafter, the sand-mixed wastewater transferred to the container 3 by the sand lifting pump 941 will be referred to as sand-mixed water. The sand-mixed water corresponds to an example of a solid-mixed liquid. The percentage of sand contained in the sand-containing water transferred to the container 3 by the sand pump 941 varies depending on the amount of sand collected in the sand collection pit 94, but is approximately 5% on average. The rate of sand-containing water transferred to the container 3 by the sand pump 941 is approximately 2.0 m3 / min. The rate of sand-containing water flowing into the container 3 is determined by the capacity of the sand pump 941. Therefore, the sand pump 941 is appropriately selected depending on the size of the container 3 and the storage tank 4. However, to balance the amount of liquid components pumped from the storage tank 4 (described below) and the concentrated liquid (described below) discharged from the outlet 331 of the container 3, it is preferable to use a sand pump 941 that can transfer sand-containing water at a rate of 2.0 m3 / min or more into the container 3. However, using a sand pump 941 with excessively high capacity will only increase the cost and power consumption of the sand pump 941. Therefore, it is preferable to use a sand pump 941 that transfers sand-containing water at a rate of 4 m3 / min or less into the container 3.

[0018] The solid-liquid separation device 1 includes a container 3, a storage tank 4, a discharge device 5, and a delivery pipe 6. The container 3, the storage tank 4, and the delivery device 5 are located on the ground near the settling basin 9. The lower part of the container 3 is located within the storage tank 4, and the upper part of the container 3 protrudes above the storage tank 4. The container 3 is a so-called liquid cyclone that removes some of the wastewater from the sand-containing water that flows into it and delivers it to the delivery pipe 6. The container 3 also discharges a concentrated liquid with an increased sand concentration due to the removal of some of the wastewater into the storage tank 4. The storage tank 4 stores the discharged concentrated liquid facing the discharge port 331. The wastewater delivered directly from the container 3 to the delivery pipe 6 is returned to the settling basin 9 through the delivery pipe 6 together with liquid components pumped up from the storage tank 4, which will be described later. Hereinafter, the wastewater delivered directly from the container 3 to the delivery pipe 6 and the liquid component pumped up from the storage tank 4 and delivered to the delivery pipe 6 will be collectively referred to as delivery water. The sand and liquid component stored in the storage tank 4 will be collectively referred to as the stored liquid. Note that the stored liquid may contain impurities. In this embodiment, the stored liquid containing impurities will be simply referred to as the stored liquid, and the liquid component containing impurities will be simply referred to as the liquid component. The delivery pipe 6 has one end 61 connected to the container lid 312 of the container 3, a horizontal portion extending horizontally above the container 3, and a vertical portion bending from the horizontal portion and extending downward. The other end 6a, which is the lower end of the vertical portion, is located below the container 3 and outside the storage tank 4, upstream of the settling basin 9. By arranging the other end 6a upstream of the sand collection pit 94 of the settling basin 9, even if sand is accidentally delivered from the solid-liquid separator 1 through the delivery pipe 6, the sand will settle to the bottom of the settling basin 9 as it flows downstream, and can be transferred back to the container 3. The other end 6a of the delivery pipe 6 may be extended below the water level WL1 of the settling basin 9 so that the other end 6a is submerged in water. Furthermore, the other end 6a may be arranged near the bottom of the settling basin 9. The container 3 and the storage tank 4 will be described in detail later.

[0019] The unloading device 5 is connected to the lower end of the storage tank 4 and extends diagonally upward. The unloading device 5 has a screw conveyor 51 and a drop port 52. The screw conveyor 51 is disposed within the unloading device 5. The axial direction of the screw conveyor 51 coincides with the extension direction of the unloading device 5. A motor 53 and a drive transmission mechanism 54 are fixed to the upper end portion of the unloading device 5. When the motor 53 is driven, the screw conveyor 51 rotates via the drive transmission mechanism 54. The drive transmission mechanism 54 is composed of sprockets fixed to the drive shaft of the motor 53 and the screw conveyor 51, and chains wound around each sprocket, but may also be composed of other mechanical transmission elements such as gears. Alternatively, the motor 53 and the screw conveyor 51 may be directly connected without providing the drive transmission mechanism 54. The sand contained in the concentrated liquid discharged into the storage tank 4 settles within the storage tank 4 and flows into the discharge device 5 connected to the storage tank 4, where it is drained and transported diagonally upward as the screw conveyor 51 rotates. The drop port 52 is located near the upper end of the screw conveyor 51. The sand drained by the screw conveyor 51 is dropped downward from the drop port 52. In other words, the discharge device 5 discharges the sand contained in the liquid stored in the storage tank 4 to the outside of the storage tank 4. Note that the screw conveyor 51 may be replaced with another transport mechanism such as a belt conveyor.

[0020] Fig. 2(a) is a plan view of the vessel shown in Fig. 1, and Fig. 2(b) is a cross-sectional view taken along line AA in Fig. 2(a). Fig. 2(a) and Fig. 2(b) also show one end portion 61 of the delivery pipe 6 and a part of the sand lifting pipe 942.

[0021] As shown in FIG. 2(b), the container 3 includes a fluid introduction section 31, a throttle section 32, a discharge section 33, and a fluid inlet pipe 34. The fluid introduction section 31 is provided in the upper portion of the container 3. The upper end of the throttle section 32 is connected to the lower end of the fluid introduction section 31. The upper end of the discharge section 33 is connected to the lower end of the throttle section 32. The inner circumferential surface 3a of the container 3 is formed by the inner circumferential surface 31a of the fluid introduction section 31, the inner circumferential surface 32a of the throttle section 32, and the inner circumferential surface 33a of the discharge section 33. The inner circumferential surface 3a of the container 3 defines an internal space X1. In other words, the fluid introduction section 31, the throttle section 32, and the discharge section 33 form a hollow tank having the internal space X1.

[0022] The fluid introduction section 31 includes a cylindrical section 311 having a cylindrical inner circumferential surface 31a, and a container lid 312 that closes the upper end of the cylindrical section 311. The cylindrical section 311 is made of a 3.2 mm thick steel plate processed into a cylindrical shape with an inner diameter of 500 mm. The container lid 312 is made of a 6.0 mm thick steel plate processed into a ring shape with an outer diameter of 586 mm and an inner diameter of 216 mm. The container lid 312 is provided with an inspection door (not shown), which allows air to flow into and out of the container 3. The shape, material, and thickness of the cylindrical section 311 and the container lid 312 may be selected appropriately depending on the size of the internal space X1, etc.

[0023] The fluid inlet pipe 34 is connected to the upper portion of the cylindrical portion 311. The sand lifting pump 941 and the fluid inlet pipe 34 shown in FIG. 1 are connected via a sand lifting pipe 942. The sand lifting pipe 942 and the fluid inlet pipe 34 are detachably coupled by fastening flanges at their connecting ends with bolts. The fluid inlet pipe 34 has an inner diameter of 100 mm. As shown in FIG. 2(b), an inlet 341 is formed at the connection between the fluid inlet pipe 34 and the cylindrical portion 311. As indicated by the straight arrow pointing right in FIGS. 2(a) and 2(b), sand-containing water pumped up by the sand lifting pump 941 is introduced into the internal space X1 through the inlet 341 in the tangential direction of the inner circumferential surface 31a of the cylindrical portion 311. This creates a swirling flow of sand-containing water in the internal space X1.

[0024] The throttle section 32 is disposed between the inlet 341 and the outlet 33. In this throttle section 32, the cross-sectional area of ​​the internal space X1 decreases toward the outlet 33. In other words, the throttle section 32 has an inverted conical inner surface 32a whose diameter gradually decreases with increasing distance from the cylindrical section 311. This throttle section 32 is formed by processing a steel plate with a thickness of 3.2 mm into a conical shape, with an inner diameter of 500 mm at the upper end and 100 mm at the lower end. The material and thickness of the throttle section 32 may be selected appropriately depending on the size of the internal space X1, the amount of narrowing, and the like. The throttle section 32 may also be formed so that the cross-sectional area of ​​the internal space X1 gradually decreases with increasing distance from the cylindrical section 311. That is, the throttle section 32 may be formed so that the cross-sectional area of ​​the internal space X1 is smaller on the outlet 331 side than on the inlet 341 side. The cross-sectional area of ​​the lower end of the throttle section 32 is equal to the opening area of ​​the outlet 331. In this embodiment, the cross-sectional area of ​​the lower end of the throttle section 32, i.e., the opening area (cross-sectional area) of the outlet 331, is set to be equal to the opening area (cross-sectional area) of the inlet 341. However, the opening area of ​​the outlet 331 may be equal to or greater than the opening area of ​​the inlet 341. However, if the opening area of ​​the outlet 331 is made too small, the pressure loss in the container 3 increases, so the opening area of ​​the outlet 331 is preferably equal to or greater than the opening area of ​​the inlet 341. In addition, if the opening area of ​​the outlet 331 is made too small or too large, the suction action from the storage tank 4 to the container 3, which will be described later, decreases, so it is desirable to set the opening area of ​​the outlet 331 to be 50% or more and 150% or less of the opening area of ​​the inlet 341. A container flange 321 protruding toward the outside of the container 3 is formed at the upper end of the throttle section 32.

[0025] The discharge section 33 is connected to the side of the throttle section 32 opposite to the side to which the fluid introduction section 31 is connected. In other words, the discharge section 33 is connected to the lower end of the throttle section 32. The discharge section 33 is cylindrical with a flange 332 formed at the lower end. The opening at the lower end of this discharge section 33 becomes the discharge port 331. Note that the discharge section 33 may be omitted. In that case, the opening at the lower end of the throttle section 32 becomes the discharge port. The flange 332 is annular with an outer diameter of 200 mm.

[0026] The delivery pipe 6 has an inner diameter of 200 mm. One end portion 61 of the delivery pipe 6 is watertightly connected to the container lid 312 by welding. Alternatively, the one end portion 61 may protrude into the internal space X1. The lower end of the one end portion 61 forms one end of the delivery pipe 6, and the opening of that end forms the delivery outlet 611. Therefore, the one end portion 61 and the delivery outlet 611 are connected to the container 3. The delivery water delivered from the delivery outlet 611 is returned to the settling basin 9 through the delivery pipe 6. In Figures 2(a) and 2(b), the flow direction of the delivery water is indicated by a straight arrow pointing left. The opening area of ​​the delivery outlet 611 is preferably equal to or larger than the opening area of ​​the outlet 331. This increases the amount of delivery water discharged from the delivery outlet 611 and reduces pressure loss in the container 3. The opening area of ​​the delivery outlet 611 is preferably equal to or larger than the opening area of ​​the inlet 341. This allows a larger amount of fluid to be discharged from the outlet 611 than the amount of sand-containing water flowing in from the inlet 341. In this embodiment, the opening area of ​​the outlet 611 is four times the opening area of ​​the outlet 331 and the inlet 341.

[0027] Fig. 3 is a front view showing the container, the storage tank, and the lower part of the carrying-out device shown in Fig. 1. Fig. 4 is a right side view showing the container, the storage tank, and the lower part of the carrying-out device shown in Fig. 1.

[0028] As shown in FIG. 3 , the storage tank 4 includes a sidewall 41 positioned outside the container 3 and extending above the discharge port 331, a tank lid 42 closing the upper end of the sidewall 41, and legs 43 supporting the storage tank 4. In this embodiment, the sidewall 41 extends from below the discharge port 331 to the height of the connection between the throttled section 32 and the fluid introduction section 31. A hole having the same diameter as the outer periphery of the fluid introduction section 31 of the container 3 is formed in the center of the tank lid 42 in a plan view. The container 3 is joined to the storage tank 4 by welding the container flange 321 to the tank lid 42 with the upper end portion of the throttled section 32 inserted into the hole. A deodorizing pipe 421 is provided on the tank lid 42. The legs 43 are located at each of the four corners of the storage tank 4 in a plan view. In FIG. 3 , only the upper and lower ends of the legs 43 are shown, with the middle portion omitted. The lower ends of the legs 43 are grounded, allowing the storage tank 4 to be placed above ground. It should be noted that a support member for supporting the carry-out device 5 is also provided at the middle portion of the carry-out device 5 in the extending direction, but this support member is not shown.

[0029] The upper portion of the storage tank 4 is formed as a rectangular tube with a substantially square shape in a plan view. As shown in FIG. 4, a tank inclined surface 41a is formed on the lower portion of the storage tank 4. The lower end of this tank inclined surface 41a is connected to the discharge device 5. As shown in FIG. 3, the lower end of the storage tank 4 is notched obliquely upward at the same angle as the inclination of the discharge device 5. Sand contained in the concentrated liquid discharged from the discharge port 331 of the container 3 slides down the tank inclined surface 41a or is deposited in the lower portion of the discharge device 5, which is directly connected to the lower end of the storage tank 4. As described above, the sand deposited in the discharge device 5 is discharged to the outside of the solid-liquid separation apparatus 1 by the screw conveyor 51. A discharge pipe 55 is provided at the lower end of the discharge device 5 for discharging liquid and sand remaining in the storage tank 4 and the discharge device 5 during inspection, etc. A valve (not shown) is provided on the discharge pipe 55. 3 and 4 also show the tank water surface WL2 formed at a height facing the discharge port 331 by the supernatant liquid of the stored liquid discharged from the discharge port 331.

[0030] Next, we will explain the driving method and operation of this solid-liquid separator 1. Figure 5 is a flowchart showing the operation of the solid-liquid separator shown in Figure 1.

[0031] The operations of the settling basin 9 and the solid-liquid separator 1 are centrally controlled by a control device (not shown). The settling basin 9 and the solid-liquid separator 1 may each be provided with a control device, allowing them to transmit and receive information or commands to and from each other. At a predetermined time when a certain amount of sand has accumulated on the bottom of the settling basin 9 shown in FIG. 1 , the settling basin 9 discharges wastewater from a sand collection nozzle 93 to collect the sand accumulated in the trough 92 in a sand collection pit 94. After this sand collection operation, the solid-liquid separator 1 begins solid-liquid separation. The predetermined time may be periodically, for example, once a month, or when the total flow rate of wastewater flowing into or discharged from the settling basin 9 reaches a certain amount. The solid-liquid separation operation may also be started while sand is being collected in the sand collection pit 94.

[0032] In the solid-liquid separation operation, first, the operation of the discharge device 5 is started (Step S10). While the discharge device 5 is operating, sand accumulated in the lower portion of the discharge device 5 is transported diagonally upward along the discharge path of the discharge device 5. The sand transported by the screw conveyor 51 is drained in the latter half of the discharge path, which is higher than the tank water level WL2, while being transported. Then, the sand that reaches the upper end of the discharge path of the discharge device 5 is dropped downward from the drop port 52. After the operation of the discharge device 5 is started, the operation of the sand lifting pump 941 is then started. This start of operation starts the inflow of sand-containing water into the container 3 (Step S11). Because the sand-containing water flows in from the tangential direction of the inner circumferential surface 31a of the cylindrical portion 311, a swirling flow of sand-containing water is formed near the inner circumferential surface 3a of the container 3 in the internal space X1. Because the sand contained in the sand-containing water has a greater specific gravity than the wastewater, it is pressed against the inner circumferential surface 3a of the container 3 by centrifugal force and gradually falls downward while swirling along the inner circumferential surface 3a. Meanwhile, the wastewater, from which the sand has been removed, gathers in the radial center of the container 3, generating an upward flow. This upward flow causes the wastewater collected in the center to be discharged from the outlet 611 at the top of the container 3. The discharged wastewater passes through the delivery pipe 6 and is then released into the grit basin 9 from the other end 6a of the delivery pipe 6. Because the other end 6a of the delivery pipe 6 is located below the outlet 611 formed at one end of the delivery pipe 6, when the delivery pipe 6 is filled with liquid, a force is generated that sucks up the sand-containing water and other substances in the internal space X1 through the outlet 611 and discharges them into the grit basin 9 due to the siphon principle. This increases the amount of water being delivered, further enhancing the suction effect of the discharge outlet 331, which will be described later.

[0033] In the internal space X1, the sand gradually falls downward while swirling along the inner circumferential surface 3a, and begins to be discharged as concentrated liquid from the discharge port 331 together with a certain amount of wastewater (step S12). The concentrated liquid is discharged radially from the discharge port 331 due to the centrifugal force of the swirling flow. In Figures 3 and 4, the direction of concentrated liquid discharge is indicated by curved arrows. If the storage tank 4 is empty when the discharge of concentrated liquid begins, the water level WL2 in the storage tank 4 gradually rises. Furthermore, the sand contained in the stored liquid in the storage tank 4 settles toward the bottom of the storage tank 4 due to its own weight and accumulates in the lower part of the carry-out device 5. Note that as the amount of accumulated sand increases, the sand that does not fit into the lower part of the carry-out device 5 also accumulates in the lower part of the storage tank 4.

[0034] As the tank water level WL2 rises and reaches a height position facing the discharge port 331 (YES in step S13), as shown in FIGS. 3 and 4, the supernatant liquid (polluted water) of the stored liquid in the portion facing the discharge port 331 is sucked into the discharge port 331 (step S14). This supernatant liquid sucked into the discharge port 331 corresponds to an example of a liquid component. The supernatant liquid is sucked from the radial center portion of the discharge port 331 by the upward flow in the container 3. In FIGS. 3 and 4, the direction in which the supernatant liquid is sucked is indicated by a straight arrow. When this supernatant liquid is sucked into the discharge port 331, the air around the discharge port 331 is also sucked into the discharge port 331. In other words, a volume of fluid (supernatant liquid and air) greater than the volume of the concentrated liquid being discharged is sucked into the discharge port 331. In this embodiment, the delivery port 611 has an opening area larger than that of the discharge port 331, allowing a large amount of fluid to be delivered from the delivery port 611. As a result, fluid can be easily sucked through the discharge port 331. Even if a volume of fluid greater than the volume of the concentrated liquid being discharged is sucked through the discharge port 331, it can still be delivered through the delivery port 611. When the supernatant liquid and air are being sucked through the discharge port 331, a balanced state is formed in which the volume of the concentrated liquid discharged from the discharge port 331 to the storage tank 4 and the volume of the supernatant liquid sucked through the discharge port 331 into the internal space X1 are approximately equal. The volume of air sucked into the discharge port 331 is 1 / 5 or less of the volume of the supernatant liquid. In this embodiment, a flange 332 extending horizontally is formed around the discharge port 331, making it difficult for air above the discharge port 331 to be sucked into the discharge port 331. In addition, the flange 332 suppresses rippling of the tank water surface WL2 near the discharge port 331. As a result, air is less likely to be sucked into the discharge port 331, and the ratio of supernatant liquid to air sucked into the discharge port 331 is increased. Furthermore, the flange 332 makes it easier for the concentrated liquid discharged from the discharge port 331 to be discharged orderly in the radial direction. As a result, sand contained in the concentrated liquid discharged from the discharge port 331 is prevented from mixing with the supernatant liquid sucked from the radial center of the discharge port 331.The height position where the tank water surface WL2 faces the discharge outlet 331 refers to the position where the tank water surface WL2 reaches a height where the distance between the tank water surface WL2 and the discharge outlet 331 is 0 mm or more and 20 mm or less. Here, as described above, because the concentrated liquid is discharged radially from the discharge outlet 331, it is unlikely that sand contained in the concentrated liquid will be sucked in from the center of the discharge outlet 331. In addition, sand has a high specific gravity and tends to settle quickly to the bottom of the storage tank 4. Therefore, even if a strong upward flow is formed in the container 3 and the suction force generated at the discharge outlet 331 is strong, the amount of sand sucked into the container 3 is limited to an extremely small amount. Because this extremely small amount of sand has a higher specific gravity than the supernatant liquid, most of it is repelled radially from the upward flow in the container 3, absorbed into the swirling flow, and then discharged again from the discharge outlet 331 into the storage tank 4. As described above, air is also sucked in from the outlet 331, so the upward flow occurring in the center of the container 3 is a flow of fluid with a low specific gravity mixed with the sucked air. Therefore, the difference in specific gravity between the fluid that mainly constitutes the upward flow and the sand becomes larger, and the sand with a high specific gravity is more likely to be expelled in the radial direction.

[0035] If the rate of sand-containing water flowing into the container 3 is less than 2.0 m3 / min, the amount of supernatant liquid drawn into the outlet 331 will be less than the amount of concentrated liquid discharged from the outlet 331, causing the tank water level WL2 to rise beyond the outlet 331. However, when the tank water level WL2 reaches the outlet 331, the outlet 331 becomes blocked by the retained liquid, reducing the amount of concentrated liquid discharged from the outlet 331. That is, the resistance caused by the reduced cross-sectional area of ​​the internal space X1 in the throttle section 32, combined with the water pressure of the retained liquid acting on the outlet 331, makes it difficult for the concentrated liquid to be discharged from the outlet 331. As the tank water level WL2 rises, the water pressure of the retained liquid acting on the outlet 331 increases, reducing the amount of concentrated liquid discharged from the outlet 331 and increasing the amount of water delivered from the delivery port 611. Furthermore, as described above, when the delivery pipe 6 is filled with liquid, the delivery water tends to flow out of the delivery outlet 611 into the grit basin 9 due to the siphon principle, further increasing the amount of delivery water delivered from the delivery outlet 611. As a result, the amount of supernatant liquid drawn into the discharge outlet 331 increases, causing the tank water level WL2 to fall to a position facing the discharge outlet 331. In other words, while the tank water level WL2 is falling, an amount of supernatant liquid greater than the amount of concentrated liquid being discharged from the discharge outlet 331 is being drawn in. In this way, reducing the amount of sand-containing water flowing into the container 3 allows the use of an inexpensive sand lifting pump 941 and reduces the amount of electricity used by the sand lifting pump 941. Note that even when the tank water level WL2 is above the discharge outlet 331, the stored liquid remains facing the discharge outlet 331.

[0036] When a first predetermined time has elapsed since the start of operation of the sand raising pump 941 (YES in step S15), the operation of the sand raising pump 941 is stopped (step S16). This first predetermined time is the time required for the sand raising pump 941 to suck up most of the sand collected in the sand collection pit 94, and is set appropriately depending on the capacity of the sand raising pump 941 and the amount of sand that can be collected in the sand collection pit 94. Stopping the sand raising pump 941 also stops the inflow of sand-containing water into the container 3, the discharge of concentrated liquid into the storage tank 4, the suction of supernatant liquid, and the delivery of delivery water. Steps S11 to S16 described above correspond to an example of an inflow process. Steps S14 to S16 correspond to an example of a discharge / suction process.

[0037] When the second predetermined time has elapsed since the operation of the sand lifting pump 941 was stopped (YES in step S17), the operation of the carry-out device 5 is stopped (step S18). Steps S10 to S18 described above correspond to an example of the carry-out process. This second predetermined time is the sum of the time it takes for the sand contained in the concentrated liquid discharged from the discharge port 331 to settle to the lower part of the carry-out device 5 and the time it takes for the sand to be transported from the lower part of the carry-out device 5 to the drop port 52. Instead of determining whether the second predetermined time has elapsed, a sand presence / absence sensor that detects the presence or absence of sand in the lower part of the carry-out device 5 may be provided in the carry-out device 5, and the determination may be made as to whether this detection has occurred. This completes the operation of the solid-liquid separation device. While the carry-out device 5 is operating, the tank water level WL2 is below the discharge port 331 or is approximately aligned with the discharge port 331. Therefore, even if the carry-out path is short, the sand can be transported while draining the water. Since the discharge path extends obliquely upward, shortening the discharge path reduces the width and height of the discharge device 5. As a result, the solid-liquid separation device 1 can be made smaller in size.

[0038] Next, a modified example of this embodiment will be described. In the following description, the names of components that are the same as those described above may be assigned the same reference numerals as those used above, and duplicate descriptions may be omitted.

[0039] FIG. 6 is a front view similar to FIG. 3, showing a modification of the solid-liquid separator shown in FIG.

[0040] As shown in FIG. 6, the solid-liquid separation apparatus 1 of this modification differs from the solid-liquid separation apparatus 1 shown in FIG. 1 in that a cleaning water supply pipe 45 is connected to the storage tank 4. The cleaning water supply pipe 45 penetrates the side wall 41 of the storage tank 4 in a watertight manner. A discharge port 451 is formed at the tip of the cleaning water supply pipe 45. The discharge port 451 is located inside the storage tank 4 at the lower end portion of the storage tank 4. A valve 452 is provided on the cleaning water supply pipe 45. When the valve 452 is opened, purified water is discharged from the discharge port 451. As a result, purified water is injected into the storage tank 4 at a rate of approximately 0.2 m / min. This purified water corresponds to an example of cleaning water. In this modification, the discharge water is discharged from the delivery port 611 at a rate of approximately 2.2 m / min. Although the valve 452 is a manual valve in this modification, it may also be an electrically operated valve. The discharge port 451 discharges purified water toward sand accumulated at the lower end portion of the storage tank 4. By configuring in this way, the accumulated sand can be washed away efficiently. Although the washing effect will be reduced, the discharge port 451 may be provided at the upper end of the storage tank 4, and purified water may be injected from above the tank water level WL2.

[0041] The injection of purified water into the storage tank 4 is performed between step S11 (starting operation of the sand lifting pump 941) and step S16 (stopping operation of the sand lifting pump 941) shown in FIG. 5, i.e., during the inflow process. However, injection may be started before step S11 so that the tank water level WL2 faces the discharge outlet 331 in advance. In this case, the suction of the supernatant liquid begins simultaneously with the discharge of the concentrated liquid. From step S14 onward, the height position of the tank water level WL2 and the height position of the discharge outlet 331 become approximately the same. Therefore, in this modified example, almost no air is sucked through the discharge outlet 331. The injection of purified water into the storage tank 4 may be performed after step S11, for example, between step S14 (starting suction of the supernatant liquid) and step S16 (stopping operation of the sand lifting pump 941), i.e., during the discharge / suction process. This process of injecting purified water into the storage tank 4 corresponds to an example of an injection process. Injecting purified water can clean the sand in the storage tank 4.

[0042] Alternatively, a fine bubble water generator (not shown) may be provided to inject fine bubble water into the storage tank 4 instead of purified water. Fine bubble water is a liquid containing fine bubbles of 100 μm or less. Fine bubble water may be a liquid containing microbubbles, which are bubbles with a diameter of more than 1 μm and 100 μm or less, or may be a liquid containing ultrafine bubbles, which are bubbles with a diameter of 1 μm or less. Furthermore, fine bubble water may be a liquid containing both microbubbles and ultrafine bubbles. Using fine bubble water allows the sand in the storage tank 4 to be washed more effectively.

[0043] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, in this embodiment, the solid-liquid separator 1 is installed in a settling basin 9, but the solid-liquid separator 1 may also be installed in a settling basin or a reservoir such as a dam lake. The solid-liquid separator 1 may also be used to separate water and metal powder from industrial wastewater generated in a factory, etc.

[0044] According to the above-described embodiment and modified examples, the solid-liquid separator 1 can be made smaller in size.

[0045] The above-described method for driving a solid-liquid separator is a method for driving a solid-liquid separator including a container that removes a portion of liquid from a solid-containing liquid containing solids to discharge a concentrated liquid having an increased concentration of solids from a discharge port, and a storage tank that receives the concentrated liquid discharged from the discharge port, an inflow step of injecting the solid-containing liquid into the container; a discharge / suction step of discharging the concentrated liquid from the discharge port into the storage tank while sucking the liquid component in the storage tank through the discharge port, The discharge and suction step is characterized in that the liquid component near the liquid surface is sucked through the discharge port in a state where the liquid surface faces the discharge port at a height position below the discharge port.

[0046] Also, there is provided a method for driving a solid-liquid separator including a container that removes a portion of liquid from a solid-containing liquid containing solids and discharges a concentrated liquid having an increased concentration of the solids from a discharge port, and a storage tank that receives the concentrated liquid discharged from the discharge port, an inflow step of injecting the solid-containing liquid into the container; The method may further include a discharge / suction step of discharging the concentrated liquid from the discharge port into the storage tank while sucking the liquid component in the storage tank through the discharge port.

[0047] The solid-liquid separation device described above includes a container having an inlet into which a solid-containing liquid containing solids flows, an outlet through which a portion of the liquid is discharged from the solid-containing liquid, and an outlet through which a concentrated liquid having an increased concentration of solids is discharged from the outlet; a reservoir for receiving the concentrated liquid; a flange extending horizontally around the outlet, the outlet is open into the storage tank, the container has a constricted portion between the inlet and the outlet, in which a cross-sectional area of ​​an internal space defined by an inner peripheral surface of the container is smaller on the outlet side than on the inlet side, The outlet is characterized in that it discharges the concentrated liquid into the storage tank while sucking in the liquid component in the storage tank through the outlet.

[0048] Also, a container having an inlet through which a solid-containing liquid containing solids flows in, an outlet through which a portion of the liquid containing solids is discharged, and an outlet through which a concentrated liquid having an increased concentration of solids is discharged by discharging the portion of the liquid from the outlet, a reservoir for receiving the concentrated liquid; the container has a constricted portion between the inlet and the outlet, in which a cross-sectional area of ​​an internal space defined by an inner peripheral surface of the container is smaller on the outlet side than on the inlet side, The outlet may be configured to discharge the concentrated liquid into the storage tank while sucking in the liquid component in the storage tank through the outlet.

[0049] In the solid-liquid separation device disclosed in Patent Document 1, if wastewater containing a large amount of sand is discharged from the overflow port, the sand recovery rate in the solid-liquid separation device will decrease, so a storage tank of a size corresponding to the amount of concentrated liquid to be received is used.In other words, it is necessary to use a storage tank with a capacity that prevents the received concentrated liquid from being discharged from the overflow port until the sand contained in the received concentrated liquid has settled in the storage tank and is almost completely separated from the supernatant liquid.This has resulted in the problem of the solid-liquid separation device becoming larger.

[0050] The method for driving the solid-liquid separator described above is a method for driving a solid-liquid separator including a container that removes a portion of liquid from a sand-containing liquid containing sand and discharges the mixed liquid having an increased proportion of sand from a discharge port, and a storage tank that receives the mixed liquid discharged from the discharge port, an inflow step of injecting the sand-containing liquid into the container; a discharge / suction step of discharging the mixed liquid from the discharge port into the storage tank while sucking the liquid component in the storage tank through the discharge port, The discharge / suction step is characterized in that the liquid component is sucked through the discharge outlet when the liquid level is at or below the height of the discharge outlet.

[0051] Also, there is provided a method for driving a solid-liquid separator including a container that removes a portion of liquid from a solid-containing liquid containing solids and discharges a concentrated liquid having an increased concentration of the solids from a discharge port, and a storage tank that receives the concentrated liquid discharged from the discharge port, an inflow step of injecting the solid-containing liquid into the container; a discharge / suction step of discharging the concentrated liquid from the discharge port into the storage tank while sucking the liquid component in the storage tank through the discharge port, The discharge / suction step may be characterized by sucking the liquid component through the discharge port in a state where the liquid level is at or below the height of the discharge port.

[0052] In the discharge and suction step, the liquid component in the storage tank is sucked through the discharge port, so that the liquid component in the storage tank is less likely to increase even when the concentrated liquid is discharged, allowing the use of a smaller storage tank, and as a result, the solid-liquid separation device can be made smaller.

[0053] Here, the container may be a liquid cyclone. The liquid components in the storage tank include liquid components of the concentrated liquid. Furthermore, the discharge / suction process may be a process of sucking in, through the discharge outlet, an amount of the liquid components equal to or greater than the amount of the concentrated liquid to be discharged into the storage tank. Furthermore, the discharge / suction process may be a process of sucking in air near the discharge outlet along with the liquid components. The discharge / suction process may be a process of creating and maintaining a balanced state in which the amount of the concentrated liquid to be discharged into the storage tank and the amount of the liquid components sucked in through the discharge outlet are approximately equal. Additionally, the discharge / suction process may be a process of sucking in the liquid components near the liquid level through the discharge outlet when the liquid level is below the height of the discharge outlet and faces the discharge outlet, or a process of sucking in the liquid components near the discharge outlet when the liquid level exceeds the height of the discharge outlet. The liquid components may include impurities with a low specific gravity, such as organic matter, contained in the concentrated liquid.

[0054] In this method for driving a solid-liquid separator, the discharge suction step may be a step of sending out the liquid component sucked from the discharge outlet through a delivery port formed in the container and having an opening area larger than the opening area of ​​the discharge outlet.

[0055] This increases the amount of the liquid component that can be delivered from the delivery port, making it easier to suck the liquid component through the discharge port. Furthermore, when the liquid surface faces the discharge port at a height below the discharge port and there is a gap between the discharge port and the liquid surface, air near the discharge port is sucked through the discharge port along with the liquid component. By increasing the opening area of ​​the delivery port, more of the liquid component mixed with the sucked air can be delivered to the outside of the container. Furthermore, the liquid component mixed with air has a lower specific gravity than the liquid component without air, resulting in a greater difference in specific gravity between the liquid component and the solid. This makes it easier for the solid, which has a higher specific gravity, to be discharged into the storage tank.

[0056] Furthermore, this method for driving a solid-liquid separator may include a step of injecting a cleaning liquid into the storage tank.

[0057] By injecting the cleaning liquid, the solids in the storage tank can be cleaned.

[0058] Here, the injection step may be a step of using purified water as the cleaning liquid, or may be a step of using fine bubble water as the cleaning water. The injection step may also be a step of discharging the cleaning liquid toward the solids deposited in the lower portion of the storage tank. By discharging the cleaning liquid toward the solids, the solids can be efficiently washed. The injection step may be a step performed simultaneously with the inflow step, or may be a step performed simultaneously with the discharge / suction step.

[0059] The solid-liquid separation device described above includes a container having an inlet into which a sand-mixed liquid containing sand flows, an outlet for discharging a part of the liquid from the sand-mixed liquid, and an outlet for discharging a mixed liquid having an increased proportion of sand as a result of the part of the liquid being discharged from the outlet; a reservoir for receiving the mixed liquid; a flange extending horizontally around the outlet, the outlet is open into the storage tank, the container has a constricted portion between the inlet and the outlet, in which a cross-sectional area of ​​an internal space defined by an inner peripheral surface of the container is smaller on the outlet side than on the inlet side, The outlet is characterized in that it discharges the mixed liquid into the storage tank while sucking in the liquid components in the storage tank through the outlet.

[0060] Also, a container having an inlet through which a solid-containing liquid containing solids flows in, an outlet through which a portion of the liquid containing solids is discharged, and an outlet through which a concentrated liquid having an increased concentration of solids is discharged by discharging the portion of the liquid from the outlet, a reservoir for receiving the concentrated liquid; a flange extending horizontally around the outlet, the outlet is open into the storage tank, the container has a constricted portion between the inlet and the outlet, in which a cross-sectional area of ​​an internal space defined by an inner peripheral surface of the container is smaller on the outlet side than on the inlet side, the outlet is configured to discharge the concentrated liquid into the storage tank while sucking in the liquid component in the storage tank through the outlet, The flange may be characterized in that it makes it difficult for air to be drawn through the outlet, thereby increasing the ratio of the liquid component drawn into the outlet relative to air.

[0061] By sucking the liquid component in the storage tank through the outlet, the amount of the concentrated liquid in the storage tank is less likely to increase, allowing the use of a smaller storage tank, and as a result, the solid-liquid separation device can be made smaller.

[0062] Here, the container may be a liquid cyclone. The liquid components in the storage tank include the liquid components of the concentrated liquid. Furthermore, the discharge port may be configured to suck in a liquid component in an amount equal to or greater than the amount of the concentrated liquid discharged into the storage tank. Furthermore, the discharge port may be configured to suck in air in the vicinity of the discharge port along with the liquid component. The discharge port may be configured to create and maintain a balanced state in which the amount of the liquid discharged into the storage tank and the amount of the liquid component sucked in through the discharge port are approximately equal. Additionally, the discharge port may be configured to suck in the liquid component in the vicinity of the liquid surface through the discharge port when the liquid surface is facing the discharge port at a height below the discharge port, or to suck in the liquid component in the vicinity of the discharge port when the liquid level exceeds the height of the discharge port.

[0063] In this solid-liquid separation apparatus, the delivery port may have an opening area larger than that of the discharge port.

[0064] According to this aspect, the amount of the liquid component that can be delivered from the delivery port increases, making it easier to suck the liquid component through the discharge port. Furthermore, when the liquid level in the storage tank faces the discharge port at a height below the discharge port and there is a gap between the discharge port and the liquid level, air near the discharge port is sucked through the discharge port along with the liquid component. By increasing the opening area of ​​the delivery port, more of the liquid component mixed with the sucked air can be delivered to the outside of the container. Furthermore, the liquid component mixed with air has a lower specific gravity, which increases the difference in specific gravity between it and the solid. This makes it easier for the solid, which has a higher specific gravity, to be discharged into the storage tank.

[0065] The solid-liquid separator may further include a flange extending horizontally around the discharge port.

[0066] The flange makes it difficult for air to enter from the sides or above the outlet, so that a large amount of liquid component can be sucked in through the outlet.

[0067] According to the above, it is possible to provide a method for driving a solid-liquid separator and a solid-liquid separator that can realize a reduction in size of the solid-liquid separator. [Explanation of symbols]

[0068] 1 Solid-liquid separator 3 containers 4. Reservoir 331 Outlet

Claims

1. A method for operating a solid-liquid separator comprising: a container that removes a portion of liquid from a sand-containing liquid containing sand and discharges the resulting mixed liquid from a discharge port; and a storage tank that receives the mixed liquid discharged from the discharge port, an inflow step of injecting the sand-containing liquid into the container; a discharge / suction step of discharging the mixed liquid from the discharge port into the storage tank while sucking the liquid component in the storage tank through the discharge port, A method for driving a solid-liquid separation apparatus, characterized in that the discharge and suction process is a process of discharging cleaning water from a discharge port toward the sand accumulated in the lower end portion of the storage tank while sucking the liquid component from the discharge port.

2. 2. The method for operating a solid-liquid separator according to claim 1, further comprising a pre-injection step, which is started before the inflow step and which injects the cleaning water into the storage tank until the water surface of the storage tank faces the discharge outlet.

3. a container having an inlet through which a sand-mixed liquid containing sand flows in, an outlet through which a portion of the liquid is discharged from the sand-mixed liquid, and an outlet through which the mixed liquid having an increased proportion of sand is discharged by discharging the portion of the liquid from the outlet; a reservoir for receiving the mixed liquid; a discharge port for discharging cleaning water toward the sand accumulated in the lower end portion of the storage tank, the outlet is open into the storage tank, the container has a constricted portion between the inlet and the outlet, in which a cross-sectional area of ​​an internal space defined by an inner peripheral surface of the container is smaller on the outlet side than on the inlet side, The solid-liquid separation device is characterized in that the discharge port discharges the mixed liquid into the storage tank while sucking in the liquid component in the storage tank through the discharge port.

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