Solid-liquid separation device

Abstract

To provide a solid-liquid separation device suitable for miniaturization.SOLUTION: A solid-liquid separation device includes: a storage tank 4 that stores a mixed liquid which is poured from a supply port 9421 and obtained by mixing a liquid with sand; a liquid feeding pipe 6 which has an inlet port 631 disposed inside the storage tank 4 below the supply port, and an outlet port 621 disposed outside the storage tank 4, and sends liquid in the mixed liquid stored in the storage tank 4 from the inlet port 631 to the outside of the storage tank 4; and a conveying device 50 in which a lower end portion of the conveying path extending obliquely upward is connected to a bottom portion of the storage tank 4, and an upper end portion of the conveying path is disposed above the inlet port 631, and which conveys sand in the mixed liquid that has settled at the bottom portion of the storage tank 4 obliquely upward along the conveying path. The conveying device 50 discharges the sand collected on the bottom side, while draining the liquid from the upper end portion, to the outside of the storage tank 4 in a state where a liquid level in the storage tank 4 is lower than a predetermined height when the liquid feeding pipe 6 sends the liquid in the mixed liquid stored in the storage tank 4 to the storage tank 4.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a solid-liquid separator that separates a liquid from a liquid containing solids. [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 basin, sand contained in the wastewater flowing into the grit basin is 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 water from metal powder and the like from industrial wastewater, and devices that separate sediment and the like that has flowed into a reservoir such as a dam lake from water. Hereinafter, sand, sludge, and screen residue 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 mixed liquids.

[0003] A known example of this solid-liquid separation device is one that includes a concentration container, a storage tank, and a conveying device (see, for example, Patent Document 1). The concentration container in Patent Document 1 is located above the storage tank and is connected to a sand lifting pump located in the settling basin via a sand lifting pipe. The concentration container receives sand-containing water transferred from the settling basin by the sand lifting pump, and discharges the concentrated sand-containing water, which has a higher sand concentration relative to the wastewater than the sand-containing water, from an outlet provided in the concentration container. The storage tank receives and stores the concentrated sand-containing water discharged from the concentration container. The conveying device is connected to the lower end of the storage tank and extends diagonally upward from the connected part. Sand that has settled at the lower end of the storage tank is conveyed diagonally upward by the conveying device while being drained, and is sent to the outside 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] The conveying device of the solid-liquid separation apparatus disclosed in Patent Document 1 has a conveying path that extends from the lower end of the storage tank to a position considerably above the storage tank. The conveying device conveys sand while draining water in a portion of the conveying path that is located above the water level of the storage tank. By increasing the distance over which the conveying device conveys while draining water, the conveying device prevents wastewater in the concentrated sand-containing water stored in the storage tank from being sent out of the storage tank along with the sand. However, increasing the distance over which the conveying device conveys while draining water increases the conveying path of the conveying device, resulting in a problem of an increased size of the solid-liquid separation apparatus.

[0006] In view of the above circumstances, an object of the present invention is to provide a solid-liquid separation device that is suitable for miniaturization. [Means for solving the problem]

[0007] The solid-liquid separation device of the present invention that achieves the above object includes: a storage tank that stores a liquid containing sand mixed therein, the liquid being poured through a supply port; a liquid delivery mechanism having an inlet located within the storage tank below the supply port and an outlet located outside the storage tank, which delivers the liquid in the mixed liquid stored in the storage tank from the inlet to outside the storage tank; a conveying device having a lower end portion of a conveying path extending obliquely upward and connected to the bottom of the storage tank, and an upper end portion of the conveying path located above the inlet, for conveying the sand in the mixed liquid that has settled to the bottom of the storage tank obliquely upward along the conveying path; The conveying device is characterized in that it sends the liquid in the mixed liquid stored in the storage tank out of the storage tank using the liquid delivery mechanism, thereby lowering the liquid level in the storage tank below a predetermined height, and then drains the sand collected on the bottom side out of the storage tank while draining it at the upper end. [Effects of the Invention]

[0008] According to the present invention, a solid-liquid separation device suitable for miniaturization can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a solid-liquid separation device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a front view showing the main configuration of the solid-liquid separator shown in FIG. [Figure 3] 2 is a flowchart showing the operation of the solid-liquid separator shown in FIG. [Figure 4] 2(a) is a front view similar to FIG. 2(a), showing a first modified example of the solid-liquid separator shown in FIG. [Figure 5] 2(a) is a front view similar to FIG. 2(a), showing a second modified example of the solid-liquid separator shown in FIG. [Figure 6] 2(a) is a front view similar to FIG. 2(a), showing a third modified example of the solid-liquid separator shown in FIG. [Figure 7]FIG. 2( a ) is a front view similar to FIG. 2( a ) of a solid-liquid separator according to a second embodiment. [Figure 8] 8 is a flowchart showing the operation of the solid-liquid separator shown in FIG. [Figure 9] FIG. 10(a) is a plan view of a concentration vessel provided in a solid-liquid separator of a third embodiment, and FIG. 10(b) is a cross-sectional view taken along the line AA in FIG. [Figure 10] (a) is a plan view showing the concentration container and storage tank of the third embodiment, (b) is a front view showing the concentration container and storage tank of the third embodiment, and (c) is a cross-sectional view along the line BB in the same figure (b). [Figure 11] 11 is a flowchart showing the operation of the solid-liquid separator shown in FIG. [Figure 12] 10(a) is a front view similar to FIG. 10(b) showing a first modified example of the solid-liquid separator shown in FIG. 10, and FIG. 10(b) is a cross-sectional view taken along CC in FIG. 10(a). [Figure 13] 10(a) is a front view similar to FIG. 10(b) showing a second modified example of the solid-liquid separator shown in FIG. 10, and FIG. 10(b) is a cross-sectional view taken along the line DD in FIG. 10(a). DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 driving method of 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 and serves 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.

[0011] 1 is a schematic diagram showing a solid-liquid separation device according to one embodiment of the present invention, which also shows a grit basin 9.

[0012] As shown in FIG. 1 , the settling basin 9 of this embodiment 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 sewage flows slowly toward the left side of the figure. As the sewage flows through the settling basin 9, the sand contained in the sewage 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 stores the sewage from which sand has been removed. A lifting pump 911 is installed inside the pump well 91. The lifting pump 911 discharges the sewage stored in the pump well 91 out of the settling basin 9. A lifting pipe 912 is connected to the lifting pump 911. The sewage drawn by the lifting pump 911 is sent through the lifting pipe 912 to a settling basin (not shown). Note that FIG. 1 also shows the water level WL1 of the sewage pond. The position of this pond water surface 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 wastewater flowing into the settling basin 9.

[0013] 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, the bottom of the pond is formed with inclined pond bottom surfaces 95 that slope downward toward the trough 92. Sand contained in the wastewater that flows into the settling basin 9 settles toward the bottom of the pond and slides down the inclined pond bottom surfaces 95 or is deposited directly in the trough 92.

[0014] The sand collection nozzle 93 is positioned at the upstream end of the trough 92. The sand collection nozzle 93 is supplied with wastewater pumped from the sedimentation basin. 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. The 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. 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 transported together with the wastewater to the solid-liquid separation device 1, where it is separated into solids (sand) and liquid (wastewater).

[0015] A sand lifting pump 941 is disposed inside the sand collection pit 94 near the bottom of the pit. This sand lifting pump 941 is an example of a mixed liquid transfer pump. A sand lifting pipe 942 is connected to the sand lifting pump 941. The sand lifting pump 941 sucks sand collected inside the sand collection pit 94 together with wastewater, and transfers the sand-mixed wastewater to the solid-liquid separation device 1 through the sand lifting pipe 942. The ratio of sand to wastewater transferred by the sand lifting pump 941 to the solid-liquid separation device 1 varies depending on the amount of sand collected inside the sand collection pit 94, but is approximately 5% sand and 95% wastewater. The sand-mixed water, which is wastewater mixed with sand and transferred by the sand lifting pump 941, is an example of a mixed liquid. The sand in the sand-mixed water is an example of a solid, and the wastewater in the sand-mixed water is an example of a liquid.

[0016] The solid-liquid separation device 1 includes a storage tank 4, a belt gate 5, a liquid feed pipe 6, and an overflow pipe 7. The storage tank 4 and the belt gate 5 are disposed on the ground near a settling basin 9. The belt gate 5 is disposed at the lower end of the storage tank 4. This belt gate 5 corresponds to an example of a discharge means. The storage tank 4 and the belt gate 5 are held by a frame 45 at a position higher than the height of the truck T.

[0017] The storage tank 4 separates the wastewater from the sand contained in the transported sand-containing water and sends it out through the liquid supply pipe 6 and overflow pipe 7. The wastewater separated from the sand in the storage tank 4 is returned to the grit basin 9 through the liquid supply pipe 6 and overflow pipe 7. The liquid supply pipe 6 has a horizontal section 61 consisting of a horizontally extending pipe, a vertical section 62 consisting of a pipe bent downward from the horizontal section, and an end section 63 (see Figure 2) consisting of a pipe inserted into the storage tank 4 and bent downward from the horizontal section. This liquid supply pipe 6 corresponds to an example of a liquid supply mechanism. The vertical section 62 is provided on the other end of the liquid supply pipe 6, and at its lower end is formed an outlet 621 through which the wastewater separated from the sand in the storage tank 4 flows out. This outlet 621 is located outside the storage tank 4 and below the storage tank 4. Furthermore, this outlet 621 faces the pond water level WL1 and discharges the wastewater sent from the storage tank 4 through the liquid supply pipe 6 into the grit basin 9. The other end of the liquid supply pipe 6 may be extended below the pond water level WL1 of the grit basin 9 so that the outlet 621 is submerged. Alternatively, an intermediate tank may be installed between the storage tank 4 and the grit basin 9 to store the wastewater flowing out from the outlet 621. By providing an intermediate tank, the state of the wastewater can be confirmed by checking the wastewater accumulated in the intermediate tank. Even if a certain amount of sand is sent out along with the wastewater through the liquid supply pipe 6, the sand can be allowed to settle in the intermediate tank and the supernatant liquid of the intermediate tank can be returned to the grit basin 9, thereby further preventing the sand from being returned to the grit basin 9.

[0018] Fig. 2 is a front view showing the main configuration of the solid-liquid separation device shown in Fig. 1. Fig. 2(a) shows a state in which the lower end of the storage tank is closed by a belt gate, and Fig. 2(b) shows a state in which the lower end of the storage tank is open.

[0019] The storage tank 4 shown in Figure 2 is a rectangular cylindrical tank that is roughly square in plan view and is made up of four vertically rising side walls 41. The top end of the storage tank 4 is open, and the end of the sand lifting pipe 942 opposite the end to which the sand lifting pump 941 is connected is inserted into this open part. A supply port 9421 is formed at the tip of the part of the sand lifting pipe 942 that is inserted into the storage tank 4. Sand-containing water sucked in by the sand lifting pump 941 (see Figure 1) passes through the sand lifting pipe 942 and is poured into the storage tank 4 from the supply port 9421.

[0020] One end of the liquid supply pipe 6 penetrates the sidewall 41 that constitutes one side of the storage tank 4. The penetrating portion of the liquid supply pipe 6 is welded to the sidewall 41, making the penetrating portion watertight. The portion of the liquid supply pipe 6 that is disposed within the storage tank 4 is the first end portion 63. This first end portion 63 protrudes into the lower portion of the storage tank 4, and a downward-facing inlet 631 is formed at the protruding end. A cap-shaped cover member 632 that extends around the inlet 631 in a plan view is fixed to the first end portion 63 slightly above the inlet 631. This cover member 632 prevents sand contained in the sand-containing water poured into the storage tank 4 from being sucked into the inlet 631 as it settles within the sand-containing water stored in the storage tank 4. Note that the peripheral portion of the cover member 632 may extend below the inlet 631. Furthermore, covering member 632 may be disk-shaped. Furthermore, covering member 632 may extend from the same height as inlet 631 to the periphery of inlet 631. That is, covering member 632 may be provided above inlet 631 or around inlet 631. In other words, covering member 632 may be disposed between supply port 9421 and inlet 631. Note that if a disk-shaped covering member extending horizontally is used as covering member 632, sand will accumulate on top of covering member 632, so it is preferable to use a cap-shaped covering member or a disk-shaped covering member installed at an angle.

[0021] The end of the overflow pipe 7 penetrates the side wall 41 slightly below the top of the storage tank 4, protruding slightly into the tank. The penetration portion of the overflow pipe 7 is welded to the side wall 41, making the penetration portion watertight. An overflow port 43 is formed at the protruding end of the overflow pipe 7. This overflow port 43 allows the supernatant liquid of the sand-containing water (contaminated water) to flow out of the storage tank 4 when the tank water level WL2 formed by the sand-containing water poured into the storage tank 4 reaches near the top of the storage tank 4. This tank water level WL2 is an example of a liquid level. The supernatant liquid flowing out from the overflow port 43 is returned to the grit basin 9 (see Figure 1) through the overflow pipe 7. The provision of this overflow port 43 prevents the sand-containing water from overflowing from the top of the storage tank 4.

[0022] An opening 4a is formed at the bottom of the storage tank 4. In FIG. 2(a), this opening 4a is blocked by a belt gate 5. The opening 4a of the storage tank 4 is tilted upward by 3° from left to right in the figure. The belt gate 5 is disposed at the bottom of the storage tank 4, tilted upward by 3°, just like the opening 4a. However, the opening 4a and the belt gate 5 may be disposed horizontally. When the opening 4a is blocked by the belt gate 5, the sand-containing water stored in the storage tank 4 is prevented from being discharged through the opening 4a. Hereinafter, the state in which the opening 4a is blocked by the belt gate 5 shown in FIG. 2(a) is referred to as the blocked state. The belt gate 5 has multiple rollers 51 extending in a direction perpendicular to the paper surface and a belt 52 wound around these rollers 51. Of the multiple rollers 51, the rollers 51 located at both the left and right ends in Fig. 2(a) are for driving, and by driving these driving rollers 51, the belt gate 5 moves from the closed position to the right as shown by the arrow in Fig. 2(a). Hereinafter, the direction in which the belt gate 5 moves from the closed position is referred to as the opening direction. Note that because the belt gate 5 is well known, a detailed description will be omitted, and the belt gate 5 is shown in a simplified form in the drawings, omitting the drive device, frame, etc.

[0023] Sand-containing water is poured into the storage tank 4 in a closed state. The sand contained in the sand-containing water poured into the storage tank 4 sinks within the sand-containing water and accumulates on the belt gate 5. That is, the sand contained in the sand-containing water stored in the storage tank 4 is collected at the bottom of the storage tank 4. In FIG. 2(a), an example of the accumulated sand SA is indicated by a dot surrounded by a two-dot chain line. A sensor 42 that detects the height of the accumulated sand SA is fixed to the storage tank 4. This sensor 42 corresponds to an example of a height position detection means. The sensor 42 may be of a contact type or a non-contact type. This sensor 42 outputs an output when the height of the accumulated sand SA reaches a predetermined height position lower than the inlet 631. However, the sensor 42 may also be one that linearly outputs the height position of the accumulated sand SA (the distance from the accumulated sand SA to the sensor 42) as a current value or a voltage value.

[0024] FIG. 2(b) shows the state in which the belt gate 5 has moved from the closed position shown in FIG. 2(a) toward the open position, opening all of the openings 4a. As the belt gate 5 moves toward the open position, the sand SA accumulated on the belt gate 5 is discharged from the opening 4a of the storage tank 4 along with a small amount of wastewater. This small amount of wastewater is the wastewater remaining between the top surface of the accumulated sand SA and the inlet 631 after the completion of the liquid transfer process (described later). In other words, as the belt gate 5 moves toward the open position, sand-mixed water with an extremely high sand concentration is discharged to the outside of the storage tank 4. Note that FIG. 2(b) shows the state in which all of the accumulated sand SA, indicated by the dots surrounded by the two-dot chain line in FIG. 2(a), has been discharged. Hereinafter, the state of the belt gate 5 in which all of the openings 4a are open will be referred to as the open state. The belt gate 5 moves from the open position shown in FIG. 2(b) to the left, as indicated by the arrow in FIG. 2(b), by the drive roller 51. Hereinafter, the direction in which the belt gate 5 moves from the open position is referred to as the closing direction. That is, the belt gate 5 changes the state of the solid-liquid separation device 1 between the closed state and the open state, and by changing it to the open state, the sand SA accumulated on the bottom side of the storage tank 4 is discharged to the outside of the storage tank 4.

[0025] Next, the operation of the solid-liquid separator 1 will be described with reference to Figures 1 to 3. Figure 3 is a flowchart showing the operation of the solid-liquid separator shown in Figure 1.

[0026] 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 in a sand collection pit 94. After the sand collection operation, the solid-liquid separator 1 starts a solid-liquid separation operation. The predetermined time may be periodically, for example, once a month, or when the total flow rate of wastewater flowing into the settling basin 9 or the total flow rate of wastewater 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.

[0027] During solid-liquid separation, the sand lifting pump 941 starts operating in the closed state. This operation starts the storage tank 4 to receive sand-containing water (step S11). If the storage tank 4 is empty when the reception of sand-containing water begins, the water level WL2 in the storage tank 4 gradually rises. Furthermore, the sand contained in the sand-containing water stored in the storage tank 4 settles to the bottom of the storage tank 4 due to its own weight and accumulates on the belt gate 5. When the water level WL2 rises and exceeds the inlet 631 and reaches the lower end of the horizontal portion 61 of the liquid transfer pipe 6, wastewater, which is the supernatant liquid of the sand-containing water, begins to be sent to the grit basin 9 by the liquid transfer pipe 6. When the water level WL2 continues to rise and reaches the upper end of the horizontal portion 61, the horizontal portion 61, vertical portion 62, and one end portion 63 of the liquid transfer pipe 6 are all filled with wastewater. When these pipes are filled with sewage, due to the siphon principle, the sewage tends to flow out of the outlet 621, which is lower than the inlet 631. Therefore, the potential energy of the sewage in the sand-containing water increases the amount of sewage delivered to the outside of the storage tank 4 through the liquid delivery pipe 6. Although a force that sucks the sand-containing water is generated near the inlet 631, sand that settles near the inlet 631 slides down the cover member 632 and falls from the edge of the cover member 632, thereby being directed away from the inlet 631. This prevents sand that settles near the inlet 631 from being sucked into the inlet 631 and delivered to the outside of the storage tank 4 through the liquid delivery pipe 6. In this embodiment, the amount of sand-containing water pumped up by the sand lifting pump 941 is greater than the amount of sewage delivered from the inlet 631. Therefore, the tank water level WL2 continues to rise even after the amount of sewage delivered from the inlet 631 increases. After the tank water level WL2 reaches the overflow port 43, the supernatant liquid of the sand-containing water also flows out of the overflow port 43. This stops the tank water level WL2 from rising, and the tank water level WL2 is maintained at that position. Figure 2 shows the tank water level WL2 at this time. While the tank water level WL2 is rising, and even after it has stopped rising, the sand contained in the sand-containing water received by the storage tank 4 settles and collects at the bottom of the storage tank 4.

[0028] After the sand lifting pump 941 starts operating, the sensor 42 constantly detects whether the height of the accumulated sand SA has reached a position slightly lower than the inlet 631 (step S12). The height of the accumulated sand SA detected by the sensor 42 is set to the maximum height at which the accumulated sand SA will not be sucked into the inlet 631 when the flow of wastewater toward the inlet 631 is at its strongest. Instead of the sensor 42, a timer may be provided that sets the time at which the accumulated sand SA will reach a position slightly lower than the inlet 631, and the timer may detect that the time has elapsed since the sand lifting pump 941 started operating. However, since the concentration of sand contained in the sand-containing water received by the storage tank 4 is not constant and the time it takes for the accumulated sand SA to reach a position slightly lower than the inlet 631 is also not constant, it is preferable to use the sensor 42 rather than a timer in order to accurately detect the height of the accumulated sand SA.

[0029] When the sensor 42 detects that the height of the accumulated sand SA has reached a position slightly lower than the inlet 631 (YES in step S12), the operation of the sand lifting pump 941 is stopped (step S13). This stops the reception of sand-containing water into the storage tank 4. The process from step S11 to step S12, as described above, corresponds to an example of the receiving process. The operation of the sand lifting pump 941 may be stopped immediately upon detection by the sensor 42, or may be stopped some time after detection by the sensor 42. In other words, the operation of the sand lifting pump 941 may be stopped based on the detection by the sensor 42. Even after the operation of the sand lifting pump 941 is stopped, the sand-containing water continues to flow out through the liquid supply pipe 6 into the settling basin 9 due to the effect of the siphon principle described above. As a result, the supernatant liquid of the sand-containing water flows out through the liquid supply pipe 6 into the settling basin 9, and the tank water level WL2 drops. That is, the potential energy of the wastewater contained in the sand-containing water stored in the storage tank 4 is utilized to send the wastewater out of the storage tank 4 through the liquid supply pipe 6, thereby lowering the tank water level WL2. Meanwhile, while the tank water level WL2 is lowering, the sand contained in the sand-containing water gradually settles under its own weight and collects at the bottom of the storage tank 4. When the tank water level WL2 drops to the vicinity of the inlet 631, air enters the liquid supply pipe 6 from the inlet 631, and the effect of the siphon principle ends. The state immediately after the sand lifting pump 941 is stopped is maintained until a first predetermined time has elapsed since the drive of the sand lifting pump 941 was stopped (step S14). This first predetermined time is sufficient time for the tank water level WL2 to drop from the vicinity of the overflow port 43 to the vicinity of the inlet 631. Instead of determining whether the first predetermined time has elapsed, a water level sensor may be provided in the storage tank 4 to detect when the tank water level WL2 has dropped to a position lower than the height of the inlet 631, and whether this detection has occurred may be determined. Steps S13 and S14 described above correspond to an example of a liquid transfer process. In steps S13 and S14, a small amount of sand-mixed water may be supplied to the storage tank 4 without completely stopping the operation of the sand lifting pump 941, as long as the amount is enough to lower the tank water level WL2.

[0030] After the first predetermined time has elapsed, with the tank water level WL2 having dropped to near the inlet 631, the belt gate 5 is moved in the opening direction to open it (step S15). As the belt gate 5 moves, the sand SA that had accumulated on the belt gate 5 is discharged outside the storage tank 4. This step S15 corresponds to an example of a discharge process. Before the storage tank 4 is opened, a truck T is made to wait below the storage tank 4 as shown in FIG. 1. The sand discharged from the storage tank 4 falls into the loading platform of the truck T or a container provided on the loading platform and is transported by the truck T. Once the sand in the storage tank 4 has been discharged, the belt gate 5 is moved in the closing direction to close it (step S16), thereby completing the solid-liquid separation operation.

[0031] According to this solid-liquid separation apparatus 1 and its driving method, the water level WL2 in the storage tank 4 is lowered until the amount of wastewater in the sand-containing water in the storage tank 4 becomes extremely small, and then the sand is discharged. This allows a gate device such as a belt gate 5 to be used instead of a conveying device that drains the sand while discharging it. Because the belt gate 5 does not need to extend diagonally upward like a conveying device that drains the water while discharging, the height and width of the solid-liquid separation apparatus 1 can be reduced, allowing for a more compact solid-liquid separation apparatus 1. Furthermore, in the liquid transfer step (steps S13 and S14), the wastewater in the sand-containing water is sent to the outside of the storage tank 4 using the potential energy of the wastewater, eliminating the need for a pump or other device in the solid-liquid separation apparatus 1. This allows the solid-liquid separation apparatus 1 to be constructed inexpensively. Furthermore, since the height position of the accumulated sand SA is detected by the sensor 42, the sand SA can be accumulated up to approximately the same height as the inlet 631, preventing the accumulated sand SA from being sucked in from the inlet 631 along with the wastewater, while maximizing the amount of sand SA remaining in the storage tank 4 after the liquid transfer process. In other words, the amount of wastewater remaining in the storage tank 4 after the liquid transfer process can be minimized, thereby increasing the concentration of sand SA in the sand-containing water. Furthermore, according to this solid-liquid separation device 1 and its driving method, the wastewater tends to flow out of the storage tank 4 into the grit basin 9 due to the siphon principle while the sand lifting pump 941 is operating, allowing the power required for the sand lifting pump 941 to be reduced.

[0032] Next, a modified example of the solid-liquid separator and its driving method according to the present 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 duplicated descriptions may be omitted.

[0033] FIG. 4 is a front view similar to FIG. 2(a), showing a first modified example of the solid-liquid separator shown in FIG.

[0034] As shown in FIG. 4, the solid-liquid separation apparatus 1 of this first modified example differs from the solid-liquid separation apparatus 1 shown in FIG. 1 in that it does not have a cover member 632 but has an electric valve 64 instead. In this first modified example, the electric valve 64 is provided in the vertical middle portion of the vertical portion 62 of the liquid transfer pipe 6. The electric valve 64 is a flow rate control valve that can adjust the flow rate of wastewater sent out of the storage tank 4 through the liquid transfer pipe 6. The electric valve 64 corresponds to an example of a flow rate control unit. The electric valve 64 can also be used to shut off the wastewater, thereby setting the flow rate in the liquid transfer pipe 6 to zero. The electric valve 64 may be located anywhere other than the vertical middle portion of the vertical portion 62, as long as it is located between the inlet 631 and the outlet 621 of the liquid transfer pipe 6.

[0035] Next, the operation of the solid-liquid separator 1 of the first modified example will be described mainly with reference to FIGS. 3 and 4. In the solid-liquid separator 1 of the first modified example, during the receiving process (from step S11 until YES is returned in step S12), the motor-operated valve 64 blocks the flow of wastewater or allows only a very small amount of wastewater to pass through the liquid feed pipe 6. Then, during the receiving process, the overflow pipe 7 is mainly used to discharge wastewater from the storage tank 4. Because the cover member 632 is not provided, sand settling within the storage tank 4 during the receiving process may approach the inlet 631. However, because there is no or only a very small flow of wastewater flowing into the inlet 631, the sand is prevented from being discharged from the inlet 631. Then, in step S13, the operation of the sand lifting pump 941 (see FIG. 1) is stopped, and the motor-operated valve 64 is opened, and steps S14 and subsequent steps are carried out. That is, a liquid sending step is performed in which wastewater is discharged from the inlet 631 to lower the tank water level WL2, followed by a discharge step in which the belt gate 5 is moved in the opening direction to discharge the accumulated sand SA to the outside of the storage tank 4, and then the belt gate 5 is moved in the closing direction to close the tank. Note that after stopping the operation of the sand lifting pump 941, it is also possible to wait several minutes until all the sand has settled, then open the motor-operated valve 64, and then perform step S14 and subsequent steps. Although this increases the time required for the solid-liquid separation operation, opening the motor-operated valve 64 after several minutes can prevent the settling sand from being sucked in through the inlet 631.

[0036] In the liquid-transfer process of the solid-liquid separation apparatus 1 of the first modified example, the wastewater in the sand-containing water may be transferred to the outside of the storage tank 4 at a flow rate adjusted by the motor-operated valve 64. Specifically, when the motor-operated valve 64 is opened in step S13, the flow rate of the wastewater transferred to the outside of the storage tank 4 may be adjusted to a lower value by adjusting the opening of the motor-operated valve 64. This weakens the force with which the wastewater is sucked into the liquid-transfer pipe 6. Even if the sand SA is allowed to accumulate close to the inlet 631, the sand SA is prevented from being sucked into the inlet 631 along with the wastewater and transferred to the outside of the storage tank 4. This minimizes the amount of wastewater remaining in the storage tank 4 after the liquid-transfer process, thereby increasing the concentration of sand SA in the sand-containing water. Instead of the motor-operated valve 64, a manually adjustable valve or a constant flow valve with a fixed flow rate may be used. In this case, these valves serve as examples of a flow rate adjuster.

[0037] FIG. 5 is a front view similar to FIG. 2(a), showing a second modified example of the solid-liquid separator shown in FIG.

[0038] As shown in Figure 5, the solid-liquid separation apparatus 1 of this second modified example differs from the solid-liquid separation apparatus 1 shown in Figure 1 in that it does not have a cover member 632, but instead has a small pump 633. In this second modified example, the small pump 633 is provided at the tip side of one end portion 63 of the liquid transfer pipe 6. In this second modified example, the suction port of the small pump 633 becomes the inlet 631. This small pump 633 is a pump that can adjust the amount of wastewater sucked in from the inlet 631 by changing the rotation speed of the inverter motor. However, a small pump that cannot adjust the amount of wastewater sucked in may also be used, and a flow rate adjustment valve similar to that of the first modified example may be installed together with the small pump.

[0039] Next, the operation of the solid-liquid separator 1 of the second modified example will be described mainly with reference to FIGS. 3 and 5. In the solid-liquid separator 1 of the second modified example, the small pump 633 is stopped or the amount of wastewater sucked by the small pump 633 is reduced during the receiving process (from step S11 until YES is returned in step S12). During the receiving process, the wastewater is mainly discharged from the storage tank 4 using the overflow pipe 7. Because the cover member 632 is not provided, sand settling within the storage tank 4 during the receiving process may approach the inlet 631. However, since there is no or only a very small flow of wastewater flowing into the inlet 631, the sand is prevented from being discharged from the inlet 631. Then, in step S13, the operation of the sand lifting pump 941 is stopped and the small pump 633 is started simultaneously, or the amount of wastewater sucked by the small pump 633 is increased, and steps S14 and subsequent steps are performed. Specifically, the small pump 633 pumps the wastewater mixed with sand out of the storage tank 4. After stopping the operation of the sand lifting pump 941, it is also possible to wait for a few minutes until all the sand has settled, then operate the small pump 633 or increase the suction amount, and then execute step S14 and subsequent steps.

[0040] In the solid-liquid separation apparatus 1 of the second modified example, when driving the small pump 633 or increasing the suction amount in step S13, the flow rate of the wastewater sent out of the storage tank 4 in the liquid sending step may be reduced by adjusting the suction amount of the small pump 633. By doing so, even if the sand SA is allowed to pile up until it is quite close to the inlet 631, the sand SA is prevented from being sucked into the inlet 631 along with the wastewater and sent out of the storage tank 4. Therefore, the amount of wastewater remaining in the storage tank 4 after the liquid sending step can be minimized, and the concentration of sand SA in the sand-mixed water can be increased.

[0041] FIG. 6 is a front view similar to FIG. 2(a), showing a third modified example of the solid-liquid separator shown in FIG.

[0042] As shown in FIG. 6, the solid-liquid separation apparatus 1 of this second modified example differs from the solid-liquid separation apparatus 1 shown in FIG. 1 in the configuration of one end portion 63 of the liquid transfer pipe 6 and the configuration of the cover member 632. One end portion 63 of the liquid transfer pipe 6 protrudes horizontally within the reservoir tank 4, and the inlet 631 faces horizontally. The cover member 632 is attached to the inner surface of the side wall 41 of the reservoir tank 4 and protrudes toward the inside of the reservoir tank 4 parallel to the one end portion 63 of the liquid transfer pipe 6. As shown in the view seen from the arrow Z in FIG. 6, the cover member 632 is made of a plate material with a V-shaped cross section that covers the upper part of the inlet 631. The cover member 632 can prevent sand settling near the inlet 631 from entering the inlet 631.

[0043] Next, a solid-liquid separator 1 according to a second embodiment will be described.

[0044] FIG. 7 is a front view similar to FIG. 2(a) of the solid-liquid separator of the second embodiment.

[0045] As shown in FIG. 7, the solid-liquid separation apparatus 1 of this second embodiment differs from the solid-liquid separation apparatus 1 shown in FIG. 1 in that a conveying device 50 is provided instead of the belt gate 5 and in the shape of the lower portion of the side wall 41 of the storage tank 4. The conveying device 50 extends obliquely upward from the lower end of the storage tank 4. The lower end of the storage tank 4 is notched obliquely upward at the same angle as the inclination of the conveying device 50. Of the four side walls 41 of the storage tank 4, tank inclined surfaces 41a are formed on the lower portions of the side walls 41 on the front and rear sides of the page in FIG. 7. The tank inclined surfaces 41a are formed at a fixed height from the lower end of the storage tank 4. The lower end of the tank inclined surfaces 41a is connected to the conveying device 50. Sand contained in the sand-containing water stored in the storage tank 4 settles toward the bottom of the storage tank 4 and accumulates on the lower end of the conveying device 50. In Figure 7, an example of deposited sand SA is shown as a dot surrounded by a two-dot chain line.

[0046] The conveying device 50 has a screw conveyor 501, a dropping section 502, and a cylindrical section 503 that covers the outside of the screw conveyor 501. The screw conveyor 501 is disposed within the cylindrical section 503. The axial direction of the screw conveyor 501 coincides with the extension direction of the conveying device 50. The screw conveyor 501 forms a conveying path that extends diagonally upward. The lower end of this conveying path is connected to the bottom of the storage tank 4. The upper end of the conveying path is disposed above the inlet 631 formed in one end portion 63 of the liquid supply pipe 6. The sand contained in the sand-mixed water stored in the storage tank 4 settles within the storage tank 4 and collects at the bottom side of the storage tank 4. The sand that has collected at the bottom side of the storage tank 4 is transported diagonally upward as the screw conveyor 501 rotates, and is transported while being drained at the upper end of the conveying path of the conveying device 50. The dropping section 502 is tubular and extends downward from near the upper end of the screw conveyor 501, with a drop port 502a formed at its lower end. The upper end of the dropping section 502 is connected to the lower portion of the cylindrical section 503 near the upper end. The sand drained by the screw conveyor 501 passes through the dropping section 502 and is dropped downward from the drop port 502a. In other words, the conveying device 50 transports and discharges the sand contained in the sand-containing water received in the storage tank 4 to the outside of the storage tank 4. Note that other conveying mechanisms, such as a belt conveyor or a flight conveyor, may be used instead of the screw conveyor 501. Furthermore, the dropping section 502 may be provided with an openable / closable lid that can be freely closed and opened, and the dropping section 502 may be closed when the conveying device 50 is not in operation. The closing lid is preferably formed at the upper end of the dropping section 502, i.e., between the dropping section 502 and the cylindrical section 503, but may also be provided near the drop port 502a. By providing the open / close lid, even if the tank water level WL2 rises above the upper end of the dropping part 502, the sand-mixed water can be prevented from leaking out from the dropping part 502.

[0047] FIG. 8 is a flowchart showing the operation of the solid-liquid separator shown in FIG.

[0048] In the solid-liquid separation operation of the solid-liquid separator 1 of the second embodiment, first, the transfer device 50 is stopped, and the sand lifting pump 941 (see FIG. 1) is started to be driven, thereby starting the receipt of sand-containing water into the storage tank 4 (step S21). Note that the transfer device 50 does not have to be completely stopped. For example, the transfer device 50 may be driven at a slow speed at which the liquid component contained in the sand-containing water does not reach the dropping section 502 due to the drive of the transfer device 50. In other words, the transfer device 50 may be driven at a drive speed slower than a predetermined drive speed. Thereafter, the tank water level WL2 formed by the sand-containing water stored in the storage tank 4 gradually rises. The sand contained in the sand-containing water stored in the storage tank 4 settles toward the bottom of the storage tank 4 due to its own weight and collects at the lower end of the transfer path of the transfer device 50. When the tank water level WL2 reaches the bottom end of the horizontal section 61 of the liquid supply pipe 6, the supernatant liquid (sewage) of the sand-mixed water begins to be sent to the grit basin 9 through the liquid supply pipe 6. As the tank water level WL2 continues to rise, and reaches the height of the upper end 6c of the liquid supply pipe 6, the liquid supply pipe 6 becomes filled with sewage, causing a siphon effect and increasing the amount of sewage outflow. When the tank water level WL2 reaches the overflow port 43, the supernatant liquid of the sand-mixed water flows out from the liquid supply pipe 6 and overflow pipe 7, preventing the tank water level WL2 from rising any further.

[0049] After the operation of the sand raising pump 941 (see FIG. 1) is started, the sensor 42 constantly detects whether the height position of the accumulated sand SA has reached a position slightly lower than the inlet 631 (step S22). When the sensor 42 detects that the height position of the accumulated sand SA has reached a position slightly lower than the inlet 631 (YES in step S22), the operation of the sand raising pump 941 is stopped (step S23). This stops the reception of sand-mixed water into the storage tank 4. The process from step S21 to step S22, which has been described above, corresponds to an example of a receiving process. Until a first predetermined time has elapsed since the operation of the sand raising pump 941 was stopped, the state immediately after the sand raising pump 941 was stopped is maintained (step S24). The process of steps S23 and S24 described above corresponds to an example of a liquid transfer process.

[0050] After the first predetermined time has elapsed, the conveying device 50 starts to operate (step S25). As the conveying device 50 operates at a predetermined speed, the sand collected at the bottom of the conveying path is transported to the top of the conveying path. At the start of this operation, the tank water level WL2 has dropped to near the inlet 631, which is lower than the top of the conveying path. Therefore, the sand being conveyed by the screw conveyor 501 is drained at the top of the conveying path while being conveyed. Then, the sand that reaches the top of the dropping section 502 is dropped downward from the drop port 502a. The conveying device 50 continues to operate for a second predetermined time from the start of operation (step S26). Steps S25 and S26 described above correspond to an example of a discharging process. This second predetermined time is the time required for most of the sand collected at the bottom of the conveying path to be transported and dropped from the dropping section 502. Instead of determining whether the second predetermined time has elapsed, a sand presence sensor that detects the presence or absence of sand at the bottom end of the conveying path may be provided at the bottom of the storage tank 4, and whether detection has occurred may be determined. After the second predetermined time has elapsed, the driving of the conveying device 50 is stopped (step S27), and the solid-liquid separation operation is terminated.

[0051] According to the solid-liquid separator 1 and its driving method of the second embodiment, the conveying device 50 is driven after the tank water level WL2 in the storage tank 4 is lowered, so that sand can be conveyed while draining water, even if the conveying path is short. In other words, the height of the conveying path can be lowered compared to a normal solid-liquid separator 1 in which the tank water level WL2 is not lowered, at least by the amount by which the tank water level WL2 is lowered in steps S23 and S24 described above. Because the conveying path extends diagonally upward, lowering the height of the conveying device 50 shortens the width of the conveying device 50. As a result, the solid-liquid separator 1 can be made more compact.

[0052] Next, a solid-liquid separator 1 according to a third embodiment will be described. In the description of the third embodiment, differences from the solid-liquid separator 1 according to the second embodiment will be mainly described.

[0053] Fig. 9(a) is a plan view of a concentration vessel provided in a solid-liquid separation apparatus of the third embodiment, and Fig. 9(b) is a cross-sectional view taken along line AA in Fig. 9(a). Fig. 2(a) and Fig. 2(b) also show a part of one end portion 63 of the liquid feed pipe 6.

[0054] In the solid-liquid separator 1 of the third embodiment, a concentration container 3 shown in Figure 9 is connected to one end portion 63 of the liquid feed pipe 6. This concentration container 3 is a so-called fluid cyclone device. The concentration container 3 separates sand from part of the wastewater in the sand-containing water transferred from the settling basin 9 shown in Figure 1 through the sand lifting pipe 942, and sends the separated wastewater to the liquid feed pipe 6. The solid-liquid separator 1 of the third embodiment is also provided with a transfer device 50 (see Figure 10), similar to the second embodiment. First, the concentration container 3 will be described.

[0055] As shown in FIG. 9(b), the concentration container 3 includes a fluid inlet 31, a throttled portion 32, a discharge portion 33, a fluid inlet pipe 34, and a pair of mounting portions 36. The fluid inlet 31 is provided in the upper portion of the concentration container 3. The upper end of the throttled portion 32 is connected to the lower end of the fluid inlet 31. The upper end of the discharge portion 33 is connected to the lower end of the throttled portion 32. The inner circumferential surface 3a of the concentration container 3 is formed by the inner circumferential surface 31a of the fluid inlet 31, the inner circumferential surface 32a of the throttled portion 32, and the inner circumferential surface 33a of the discharge portion 33. The inner circumferential surface 3a of the concentration container 3 defines an internal space X1. That is, the fluid inlet 31, the throttled portion 32, and the discharge portion 33 form a hollow tank having the internal space X1.

[0056] The fluid introduction section 31 includes a cylindrical section 311 having a cylindrical inner circumferential surface 31a and a lid 312 closing 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 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 114 mm. The shape, material, and thickness of the cylindrical section 311 and the lid 312 may be selected appropriately depending on the size of the internal space X1. The cylindrical section 311 may be conical or dome-shaped, with the cross-sectional area of ​​the internal space X1 increasing downward. Furthermore, the cylindrical section 311 may have a conical or dome-shaped upper portion, where the receiving port 341 (described later) is formed, with the cross-sectional area of ​​the internal space X1 increasing downward, and a cylindrical lower portion. A pair of mounting members 36 are fixed to the outer circumferential surface of the cylindrical section 311. The attachment portion 36 is used to fix the concentration container 3 to the storage tank 4 shown in FIG.

[0057] 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 is a pipe with an inner diameter of 100 mm. As shown in FIG. 2(b), a receiving port 341 is formed at the connection between the fluid inlet pipe 34 and the cylindrical portion 311. As indicated by the straight arrow in FIG. 2(a), the sand-containing water pumped up by the sand lifting pump 941 is introduced into the internal space X1 through the receiving port 341 in the tangential direction of the inner circumferential surface 31a of the cylindrical portion 311. Therefore, the sand-containing water received by the concentration container 3 is introduced between the outer circumferential surface of the portion of the one end portion 63 of the liquid supply pipe 6 inserted into the concentration container 3 and the inner circumferential surface 31a of the cylindrical portion 311. As a result, a swirling flow of sand-mixed water is formed in the internal space X1.

[0058] The throttled portion 32 is disposed between the inlet 341 and the discharge portion 33. In this throttled portion 32, the cross-sectional area of ​​the internal space X1 decreases toward the discharge portion 33. In other words, the throttled portion 32 has an inverted conical inner circumferential surface 32a whose diameter gradually decreases with increasing distance from the cylindrical portion 311. Note that the throttled portion 32 may have a cross-sectional area of ​​the internal space X1 that gradually decreases toward the discharge portion 33. That is, the throttled portion 32 is formed so that the cross-sectional area of ​​the internal space X1 is smaller on the discharge portion 33 side than on the inlet 341 side. The throttled portion 32 is formed by processing a steel plate with a thickness of 3.2 mm into a cone shape, and has an inner diameter of 500 mm at its upper end and 100 mm at its lower end. Note that the material and thickness of the throttled portion 32 may be selected appropriately depending on the size of the internal space X1, the amount of throttling, etc. In addition, in this embodiment, the cross-sectional area of ​​the lower end of the throttle section 32 is made to match the cross-sectional area of ​​the receiving port 341, but the cross-sectional area of ​​the lower end of the throttle section 32 may be larger or smaller than the cross-sectional area of ​​the receiving port 341. However, if the cross-sectional area of ​​the lower end of the throttle section 32 is made too small, the pressure loss in the concentration vessel 3 increases, so it is preferable that the cross-sectional area of ​​the lower end of the throttle section 32 be equal to or larger than the cross-sectional area of ​​the receiving port 341.

[0059] The discharge section 33 is connected to the opposite side of the throttle section 32 from the side where the fluid introduction section 31 is provided. 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 formed at the lower end and an inner diameter the same as the lower end of the throttle section 32. The opening at the lower end of this discharge section 33 serves as the discharge port 331. When the siphon effect occurs during the liquid transfer process, this discharge port 331 functions as a wastewater inlet for sucking in wastewater and returning it to the grit basin 9 (see FIG. 1). Therefore, the discharge port 331 in this third embodiment corresponds to an example of an inlet. Note that the discharge section 33 may be omitted. In that case, the opening at the lower end of the throttle section 32 serves as the discharge port 331.

[0060] One end portion 63 of the liquid supply pipe 6 penetrates the lid 312 of the fluid introduction section 31 in the vertical direction. This one end portion 63 extends along the radial center axis of the cylindrical portion 311 from below the lower end of the lid 312 to above the upper end of the lid 312. Therefore, the lower portion of the one end portion 63 protrudes into the internal space X1. However, the lower portion of the one end portion 63 does not have to protrude into the internal space X1. For example, the lower surface of the lid 312 and the lower end of the one end portion 63 may be flush with each other. The portion of the one end portion 63 penetrating the lid 312 is welded to the lid 312 in a watertight manner. The one end portion 63 is tubular with an inner diameter of 100 mm. The lower end of this one end portion 63 forms one end of the liquid supply pipe 6, and the opening at that end forms the wastewater discharge outlet 634. Therefore, the one end portion 63 and the wastewater discharge outlet 634 (one end of the liquid supply pipe 6) are connected to the concentration container 3. In this embodiment, the wastewater discharge port 634 is disposed within the internal space X1. The wastewater separated from the sand-containing water in the concentration vessel 3 is returned to the grit basin 9 from the wastewater discharge port 634 through the liquid supply pipe 6. The wastewater discharge port 634 is disposed below the receiving port 341. The length of the portion of the one end portion 63 located within the internal space X1 (the portion located within the concentration vessel 3) is arbitrary. For example, the portion of the one end portion 63 located within the internal space X1 may be formed longer than the fluid introduction section 31. In this case, the wastewater discharge port 634 is formed in a region of the internal space X1 defined by the inner circumferential surface 32a of the throttle section 32. In addition, although an example has been shown in which the cross-sectional area of ​​the wastewater discharge port 634 is equal to the cross-sectional area of ​​the lower end of the throttle section 32, it is preferable that the cross-sectional area of ​​the wastewater discharge port 634 be equal to or greater than the cross-sectional area of ​​the discharge port 331. This increases the amount of wastewater discharged from the wastewater outlet 634, and also reduces the pressure loss in the concentration vessel 3.

[0061] Next, the operation of the concentration vessel 3 will be described. As described above, by driving the sand-lifting pump 941 (see FIG. 1), sand-containing water flows into the internal space X1 through the inlet 341, forming a swirling flow of sand-containing water in the internal space X1. The sand contained in the sand-containing water has a greater specific gravity than the wastewater, and is therefore pressed against the inner circumferential surface 3a of the concentration vessel 3 by centrifugal force, and gradually falls downward while swirling along the inner circumferential surface 3a. Meanwhile, wastewater from which sand has been removed collects in the radial center of the cylindrical portion 311. This wastewater is discharged from the wastewater discharge outlet 634. The discharged wastewater passes through the liquid supply pipe 6 and is discharged toward the grit basin 9 from the outlet 621 (see FIG. 1) formed at the other end of the liquid supply pipe 6. However, in the concentration container 3 of this embodiment, the inlet 341 and the outlet 331 are the same size, and therefore, depending on the amount of sand-containing water received per unit time from the inlet 341, in order to discharge the wastewater from the wastewater discharge outlet 634, it is necessary to provide a storage tank 4 having a sidewall 41 higher than the outlet 331, as shown in FIG. 10. Furthermore, the concentration container 3 discharges concentrated sand-containing water, in which the concentration of sand relative to the wastewater has been increased by removing some of the wastewater from the received sand-containing water, from the outlet 331 into the storage tank 4. This concentrated sand-containing water is an example of a mixed liquid, the wastewater in the concentrated sand-containing water is an example of a liquid, and the sand in the concentrated sand-containing water is an example of a solid.

[0062] Figure 10(a) is a plan view showing the concentration container and storage tank of the third embodiment, Figure 10(b) is a front view showing the concentration container and storage tank of the third embodiment, and Figure 10(c) is a cross-sectional view along the line BB in Figure 10(b).

[0063] As shown in FIGS. 10(a) and 10(b), the storage tank 4 has a sidewall 41 that is positioned outside the outer peripheral side surface 3b of the concentration container 3 and extends above the discharge port 331. As shown in FIG. 10(c), in this embodiment, the sidewall 41 extends above the upper end 6c of the liquid feed pipe 6. The concentration container 3 is detachably fixed within the storage tank 4 by bolting the mounting portion 36 to a pair of arms 44 that extend inward and have one end fixed to the inner peripheral surface of the sidewall 41. As shown in FIGS. 10(b) and 10(c), the liquid feed pipe 6 and the sand lifting pipe 942 penetrate the sidewall 41 of the storage tank 4. The penetrating portions of the liquid feed pipe 6 and the sand lifting pipe 942 are welded to the sidewall 41, making the penetrating portions watertight.

[0064] The storage tank 4 is a rectangular tank with a roughly square shape in plan view, with two inclined tank surfaces 41a formed on its lower portion. Sand contained in the concentrated sand-containing water discharged from the discharge port 331 of the concentration container 3 slides down the inclined tank surfaces 41a and deposits in a conveying device 50 connected to the lower end of the storage tank 4. As shown in FIG. 10(c), an overflow port 43 is formed above the discharge port 331 and slightly below the upper end of the storage tank 4. This overflow port 43 allows the supernatant of the concentrated sand-containing water to flow out of the storage tank 4 when too much concentrated sand-containing water is discharged from the discharge port 331. The supernatant flowing out of the overflow port 43 is returned to the settling basin 9 (see FIG. 1) through the overflow pipe 7.

[0065] FIG. 11 is a flowchart showing the operation of the solid-liquid separator shown in FIG.

[0066] In the solid-liquid separation operation, the sand-containing pump 941 is first started while the conveying device 50 is stopped. This starts the receiving of sand-containing water into the concentration container 3 shown in FIG. 10. The conveying device 50 does not have to be completely stopped. For example, the conveying device 50 may be driven at a slow speed so that the wastewater in the concentrated sand-containing water does not reach the dropping section 502 due to the driving of the conveying device 50. That is, the conveying device 50 may be driven at a driving speed slower than the predetermined driving speed described below. If the internal space X1 of the concentration container 3 and the tank of the storage tank 4 are empty before the sand-containing pump 941 (see FIG. 1) starts to be driven, most of the sand-containing water supplied to the internal space X1 is discharged from the discharge port 331. That is, the receiving of sand-containing water and concentrated sand-containing water into the storage tank 4 starts (step S31). As the concentrated sand-containing water discharged from the discharge outlet 331 is stored in the storage tank 4, the tank water level WL2, which is the water level formed by the concentrated sand-containing water stored in the storage tank 4, gradually rises. Furthermore, the sand contained in the concentrated sand-containing water stored in the storage tank 4 settles toward the bottom of the storage tank 4 due to its own weight and collects at the lower end of the transport path of the transport device 50. When the tank water level WL2 reaches the discharge outlet 331, the discharge outlet 331 is blocked by the concentrated sand-containing water, and the amount of concentrated sand-containing water discharged from the discharge outlet 331 decreases. Specifically, the resistance due to the reduced cross-sectional area of ​​the internal space X1 in the throttle section 32, combined with the water pressure of the concentrated sand-containing water acting on the discharge outlet 331, makes it difficult for the concentrated sand-containing water to be discharged from the discharge outlet 331, and wastewater begins to be discharged from the wastewater discharge outlet 634. As the tank water level WL2 rises, the water pressure of the thickened sand-containing water acting on the discharge port 331 increases, so the amount of thickened sand-containing water discharged from the discharge port 331 decreases, while the amount of sewage sent out from the sewage discharge port 634 increases, filling the liquid supply pipe 6 with sewage. When the liquid supply pipe 6 is filled with sewage, the sewage acts as a siphon and tries to flow out into the grit basin 9. In other words, due to the potential energy of the liquid in the sand-containing water and the liquid in the thickened sand-containing water, the sewage begins to be sent out of the storage tank 4 through the liquid supply pipe 6. As a result, the amount of sewage sent out from the sewage discharge port 634 increases further, and the amount of thickened sand-containing water discharged from the discharge port 331 decreases further.If the rate of sand-containing water supplied to the internal space X1 is, for example, 1.0 m³ / min, when the tank water level WL2 drops slightly below the receiving port 341, almost only sand is discharged from the discharge port 331, and the tank water level WL2 stops rising. Figures 10(b) and 10(c) show the tank water level WL2 at this time. Furthermore, if the rate of sand-containing water supplied to the internal space X1 is, for example, 1.5 m³ / min, the amount of wastewater discharged from the wastewater discharge port 634 also increases, but concentrated sand-containing water containing a certain proportion of wastewater is discharged from the discharge port 331, and the tank water level WL2 continues to rise. After the tank water level WL2 reaches the overflow port 43, the supernatant of the sand-containing water flows out of the overflow port 43 at a rate of approximately 0.3 m³ / min. Before the sand lifting pump 941 is driven, sewage or tap water stored in the settling basin may be flowed into the storage tank 4 to fill the storage tank 4 with liquid. When the storage tank 4 is filled with liquid, the internal space X1 is also filled with liquid to approximately the same height as the storage tank 4. Therefore, if liquid is stored so that the tank water level WL2 is at or above the height of the sewage outlet 634, sewage can be sent from the sewage outlet 634 approximately simultaneously with the driving of the sand lifting pump 941. When the sand lifting pump 941 is driven for the second or subsequent time, sewage can be sent from the sewage outlet 634 approximately simultaneously with the driving of the sand lifting pump 941, as long as the liquid stored in the storage tank 4 is not drained.

[0067] After the sand raising pump 941 starts operating, the sensor 42 constantly detects whether the height of the accumulated sand SA has reached a position slightly lower than the inlet 631 (step S32). When the sensor 42 detects that the height of the accumulated sand SA has reached a position slightly lower than the outlet 331 (YES in step S32), the operation of the sand raising pump 941 is stopped (step S33). This stops the concentration container 3 from receiving the sand-containing water. The storage tank 4 also stops receiving the concentrated sand-containing water. The process from step S31 to step S32, which has been described above, corresponds to an example of a receiving process. Until a third predetermined time has elapsed since the operation of the sand raising pump 941 stopped, the state immediately after the sand raising pump 941 was stopped is maintained (step S34). The process of steps S33 and S34 described above corresponds to an example of a liquid transfer process. This third predetermined time is the time it takes for the tank water level WL2 to fall to near the outlet 331. Instead of determining whether the third predetermined time has elapsed, a water level sensor may be provided in the storage tank 4 to detect when the tank water level WL2 has dropped to near the discharge outlet 331, and it may be determined whether this detection has occurred.

[0068] Even after the sand lifting pump 941 stops operating, the concentrated sand-containing water and sand-containing water continue to flow through the liquid feed pipe 6 into the grit basin 9 due to the effect of the siphon principle described above. As a result, the supernatant liquid of the concentrated sand-containing water and sand-containing water flows through the liquid feed pipe 6 into the grit basin 9, causing the tank water level WL2 to drop. Meanwhile, while the tank water level WL2 is dropping, the sand contained in the concentrated sand-containing water and sand-containing water gradually settles due to its own weight and collects at the bottom of the transport path of the transport device 50. When the tank water level WL2 drops to the discharge port 331, air enters the liquid feed pipe 6 from the discharge port 331 through the concentration container 3, ending the effect of the siphon principle. The state immediately after the sand lifting pump 941 is stopped is maintained until a third predetermined time has elapsed since the sand lifting pump 941 stopped operating (step S34). Steps S33 and S34 described above correspond to an example of a liquid transport process. In steps S33 and S34, a small amount of sand-containing water may be supplied to the concentration container 3 without completely stopping the operation of the sand-lifting pump 941, as long as the amount is enough to lower the tank water level WL2. Steps S35 to S37 below are the same as steps S25 to S27 in the second embodiment, and therefore will not be described here.

[0069] The solid-liquid separator 1 and its driving method of the third embodiment can also reduce the size of the solid-liquid separator 1, as in the solid-liquid separator 1 and its driving method of the second embodiment. Furthermore, in step S32 described above, the discharge outlet 331 is blocked by the liquid stored in the storage tank 4, and thus the water pressure of the liquid stored in the storage tank 4 is generated at the discharge outlet 331. This water pressure makes it difficult for the thickened sand-containing water to be discharged from the discharge outlet 331, thereby increasing the amount of wastewater delivered through the liquid delivery pipe 6. In other words, the ratio of the thickened sand-containing water delivered from the wastewater delivery outlet 634 to the thickened sand-containing water delivered from the discharge outlet 331 increases, thereby improving the separation efficiency in the concentration container 3. Furthermore, because less thickened sand-containing water is discharged to the storage tank 4, the storage tank 4 can be further reduced in size. Furthermore, even if the throttle amount (amount of reduction in cross-sectional area) of the throttle section 32 is reduced, the amount of thickened sand-containing water delivered from the discharge outlet 331 can be reduced. By reducing the throttling amount in the throttle section 32, pressure loss in the concentration container 3 can be reduced, thereby reducing the power required for the sand lifting pump 941 (see FIG. 1). Furthermore, the concentrated sand-containing water discharged from the discharge port 331 does not scatter, and the sand contained in the concentrated sand-containing water tends to settle to the bottom of the storage tank 4 in a short period of time. In addition, since the transfer device 50 is connected to the storage tank 4 and the storage tank 4 and the concentration container 3 are arranged so as to overlap each other in the height direction, the overall height of the solid-liquid separation apparatus 1 can be reduced. Furthermore, since the concentration container 3 can be arranged close to the ground, the head required for the sand lifting pump 941 is reduced, and the mixed water can be transferred to the concentration container 3 with even less power.

[0070] Furthermore, in this third embodiment, the sidewall 41 of the storage tank 4 extends above the upper end of the internal space X1, allowing liquid to be stored within the storage tank 4 up to above the upper end of the internal space X1. By storing liquid up to the upper end of the internal space X1, the water pressure applied to the discharge port 331 increases, counteracting the force of gravity that causes the wastewater in the sand-containing water in the internal space X1 to flow out of the discharge port 331. This further reduces the amount of wastewater discharged from the discharge port 331, thereby further increasing the sand concentration in the concentrated sand-containing water. Furthermore, because the amount of concentrated sand-containing water discharged from the discharge port 331 to the storage tank 4 is reduced, the size of the storage tank 4 can be reduced. Furthermore, the amount of reduction in the throttle section 32 can be reduced, further reducing pressure loss. Furthermore, since the height of the side wall 41 of the storage tank 4 is set higher than the upper end 6c of the liquid supply pipe 6, even if the amount of throttling of the throttling section 32 is reduced drastically, once the tank water level WL2 reaches the upper end 6c of the pipe, the liquid supply pipe 6 will be filled with wastewater, and the effect of the siphon principle can be obtained.

[0071] Next, a modified example of the solid-liquid separator 1 of the third embodiment will be described.

[0072] FIG. 12(a) is a front view similar to FIG. 10(b) showing a first modified example of the solid-liquid separator shown in FIG. 10, and FIG. 12(b) is a cross-sectional view taken along CC in FIG. 12(a).

[0073] As shown in FIG. 12(a), the solid-liquid separation apparatus 1 of this modification differs from the solid-liquid separation apparatus 1 shown in FIG. 10 in that a fine-bubble water supply pipe 8 is connected to the sand lifting pipe 942 and the height of the storage tank 4 is lower. In this modification, nanobubble water generated by a nanobubble water generator (not shown) is supplied to the sand lifting pipe 942 through the fine-bubble water supply pipe 8. However, microbubble water may be supplied to the sand lifting pipe 942 instead of nanobubble water, or micro-nano bubble water, a mixture of nanobubble water and microbubble water, may be supplied to the sand lifting pipe 942. The fine-bubble water supply pipe 8 corresponds to an example of a fine bubble supplying means. Nanobubble water refers to water containing air bubbles with particle sizes on the order of nanometers. Microbubble water refers to water containing air bubbles with particle sizes on the order of micrometers. Note that nanobubble water may also be water containing oxygen bubbles on the order of nanometers. Similarly, microbubble water may also be water containing oxygen bubbles with particle sizes on the order of micrometers. Alternatively, the fine-bubble water supply pipe 8 may be connected directly to the concentration container 3. That is, the fine-bubble water supply pipe 8 may be connected between the sand lifting pump 941 (see FIG. 1) and the discharge port 331. Nanobubble water and microbubble water have a cleaning effect, so adding them to sand-containing water can clean the sand and contaminated water contained in the sand-containing water. By adding nanobubble water or microbubble water to the sand-containing water between the sand lifting pump 941 and the discharge port 331, the sand-containing water can be cleaned with a high cleaning effect in the internal space X1 (see FIG. 9(b)) of the concentration container 3. That is, the swirling flow generated in the internal space X1 causes the nanobubbles and microbubbles to mix with the sand-containing water within the internal space X1, thereby achieving a high cleaning effect.

[0074] The sidewall 41 of the storage tank 4 extends to a height above the top of the concentration container 3 and below the upper end 6c of the liquid feed pipe 6. By increasing the height of the sidewall 41 of the storage tank 4, as in the storage tank 4 of the third embodiment shown in FIG. 10 , it is possible to raise the tank water level WL2 of the storage tank 4 above the upper end 6c of the liquid feed pipe 6. As described above, the water pressure applied to the discharge port 331 increases with the height of the tank water level WL2. Therefore, a higher tank water level WL2 is preferable in terms of further increasing the sand concentration in the concentrated sand-containing water and reducing pressure loss. However, if the sidewall 41 of the storage tank 4 is made too high, the overall height of the solid-liquid separation apparatus 1 will increase, and the manufacturing cost of the storage tank 4 will also increase. Therefore, a lower height of the sidewall 41 of the storage tank 4 is preferable. If the side wall 41 extends above the discharge port 331, the discharge port 331 can be blocked by the concentrated sand-containing water stored in the storage tank 4, but in this modified example, the height is set with an emphasis on the balance between the overall height of the solid-liquid separation device 1 and the water pressure applied to the discharge port 331. The overflow port 43 can be positioned appropriately depending on the height of the side wall 41, but in this modified example, it is set at the same height as the receiving port 341 (see Figure 9(b)).

[0075] Next, a modification of the solid-liquid separator 1 shown in FIG. 10, which is different from the modification shown in FIG. 12, will be described.

[0076] FIG. 13(a) is a front view similar to FIG. 10(b) showing a second modified example of the solid-liquid separator shown in FIG. 10, and FIG. 13(b) is a DD cross-sectional view of FIG. 13(a).

[0077] The solid-liquid separation apparatus 1 shown in FIGS. 13(a) and 13(b) differs from the solid-liquid separation apparatus 1 shown in FIG. 10 in that the concentration vessel 3 does not have a throttle section 32 or a discharge section 33, the height of the storage tank 4 is low, and the position of the overflow port 43. The concentration vessel 3 is formed with a fluid inlet section 31. Therefore, the internal space X1 is defined only by the inner circumferential surface 31a of the fluid inlet section 31. The lower end of the concentration vessel 3 is the lower end of the cylindrical section 311, and the opening at this lower end is the discharge port 331. This discharge port 331 has a diameter of 500 mm, which is considerably larger than the receiving port 341 (see FIG. 9(b)). Therefore, in this modification, there is almost no pressure loss in the concentration vessel 3. The storage tank 4 is formed lower than the storage tank 4 shown in FIG. 10 by the combined height of the throttle section 32 and the discharge port 33. Furthermore, the receiving port 341 formed in the concentration container 3 is positioned closer to the lower end of the storage tank 4 by the total height of the receiving port 341. The reduced height of the storage tank 4 allows the length (height) of the transfer device 50 to be reduced accordingly. In other words, by reducing the height of the concentration container 3, the overall height of the solid-liquid separation device 1 can be reduced, thereby enabling the solid-liquid separation device 1 to be made more compact. Furthermore, since the receiving port 341 is positioned closer to the ground, the head required for the sand-lifting pump 941 (see FIG. 1 ) is reduced, allowing the mixed water to be transferred to the concentration container 3 with even less power. The overflow port 43 is positioned at the same height as the receiving port 341. However, the overflow port 43 may be positioned higher than the receiving port 341 or higher than the upper end 6c of the liquid transfer pipe 6. By positioning the overflow port 43 at a higher position, the liquid can be quickly stored up to a position higher than the upper end 6c of the liquid transfer pipe 6, thereby shortening the time from when the sand-mixed water begins to be supplied to the internal space X1 until the effect of the siphon principle is achieved.

[0078] The operation of this solid-liquid separation apparatus 1 is similar to that shown in FIG. 10 . However, the behavior of the sand-containing water and the concentrated sand-containing water in steps S31 and S32 shown in FIG. 11 is slightly different, and therefore these behaviors will be mainly described. When the internal space X1 of the concentration container 3 and the storage tank 4 are empty, the sand-containing water begins to be supplied to the internal space X1 by driving the sand-lifting pump 941 shown in FIG. 1 . In this modification, the sand-containing water is supplied to the internal space X1 at a rate of 2.0 m / min. The sand-containing water is introduced into the internal space X1 from the tangential direction of the inner circumferential surface 31a of the cylindrical portion 311 through the receiving port 341 (see FIG. 9(b)). This creates a swirling flow of the sand-containing water in the internal space X1. The sand contained in the sand-containing water has a higher specific gravity than the wastewater. Therefore, the sand is pressed against the inner circumferential surface 31a of the cylindrical portion 311 by centrifugal force, and gradually falls downward while swirling along the inner circumferential surface 31a. Meanwhile, wastewater from which sand has been removed remains near the radial center of the cylindrical portion 311. While there is only a small amount of liquid stored in the storage tank 4, all of the sand-containing water supplied to the internal space X1 is discharged from the outlet 331 as concentrated sand-containing water. As the concentrated sand-containing water discharged from the outlet 331 is stored within the storage tank 4, the tank water level WL2 gradually rises. When the tank water level WL2 reaches the outlet 331, the outlet 331 is blocked by the concentrated sand-containing water, and as the tank water level WL2 rises, the water pressure of the concentrated sand-containing water acting on the outlet 331 increases. 9(b) is not present, and the outlet 331 is sufficiently large relative to the inlet 341. Therefore, even after the outlet 331 is blocked by the thickened sand-containing water, all of the sand-containing water supplied to the internal space X1 is discharged through the outlet 331 until the tank water level WL2 reaches a predetermined height. When the tank water level WL2 subsequently reaches the overflow port 43, the supernatant of the thickened sand-containing water flows out through the overflow port 43. However, because the amount of sand-containing water supplied by the sand lifting pump 941 is greater than the supernatant flowing out of the overflow port 43 due to gravity, the tank water level WL2 continues to rise. When the tank water level WL2 reaches the lower end 6d of the liquid supply pipe 6, the wastewater begins to be discharged through the liquid supply pipe 6.When the tank water level WL2 reaches the upper end 6c of the pipe, the liquid supply pipe 6 is filled with liquid, and the sand-containing water acts like a siphon to flow out of the wastewater discharge outlet 634 into the grit basin 9. This causes the amount of wastewater discharged from the wastewater discharge outlet 634 to increase further, causing the tank water level WL2 to stop rising, then drop and stabilize at a certain position. Figures 13(a) and 13(b) show the tank water level WL2 at this time. When the tank water level WL2 is stable, supernatant liquid flows out of the overflow outlet 43 at a rate of approximately 1.2 m3 / min.

[0079] The solid-liquid separator 1 of this modification also provides the same effects as the solid-liquid separator 1 shown in Figure 10. Furthermore, the water pressure at the outlet 331 generated by the liquid stored in the storage tank 4 can reduce the amount of concentrated sand-containing water discharged from the outlet 331, even without the throttle section 32. The absence of the throttle section 32 virtually eliminates pressure loss in the concentration vessel 3, allowing for a reduction in the power required for the sand lifting pump 941 (see Figure 1). Furthermore, even when there is no liquid in the liquid feed pipe 6, simply driving the sand lifting pump 941 causes the tank water level WL2 to reach the height of the pipe upper end 6c, filling the liquid feed pipe 6 with liquid, thereby easily achieving the siphon action.

[0080] The present invention is not limited to the above-described embodiments, 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 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. Furthermore, while the embodiment uses a belt gate 5 and a screw conveyor 501, a gate device such as a slide gate or a cut gate, or a transport device such as a belt conveyor or a flight conveyor may also be used as a discharge device.

[0081] According to the above-described embodiment and modified examples, it is possible to provide a method for driving a solid-liquid separator that can reduce the size of the solid-liquid separator, and a solid-liquid separator that is suitable for miniaturization.

[0082] Note that even if a constituent element is included only in the description of each of the above-described embodiments and modifications, that constituent element may be applied to other embodiments and modifications.

[0083] The above-described method for driving a solid-liquid separator is a method for driving a solid-liquid separator including: a storage tank for storing a mixed liquid in which solids are mixed into a liquid; a liquid delivery mechanism having an inlet disposed within the storage tank and an outlet disposed outside the storage tank; and a discharge device for discharging solids collected on the bottom side of the storage tank to the outside of the storage tank, a receiving step of receiving the mixed liquid into the storage tank; a liquid sending step of sending the liquid in the mixed liquid stored in the storage tank out of the storage tank by the liquid sending mechanism to lower the liquid level in the storage tank; The method is characterized by having a discharge step in which, with the liquid level in the storage tank lowered below a predetermined height by the liquid transfer step, the solids collected on the bottom side are discharged outside the storage tank by the discharge device.

[0084] The solid-liquid separation device described above includes a storage tank for storing a mixed liquid in which a solid is mixed into a liquid, a liquid delivery mechanism having an inlet disposed within the reservoir tank and an outlet disposed outside the reservoir tank; a discharge device that discharges solids collected on the bottom side of the storage tank to the outside of the storage tank, The discharge device is characterized in that it discharges solids collected on the bottom side to the outside of the storage tank while lowering the liquid level in the storage tank below a predetermined height by sending the liquid in the mixed liquid stored in the storage tank out of the storage tank using the liquid delivery mechanism.

[0085] The above-described method for driving a solid-liquid separator includes a storage tank that stores a liquid containing solids mixed therein and that is poured in through a supply port, a liquid delivery mechanism that has an inlet located within the storage tank and below the supply port and an outlet located outside the storage tank and below the inlet, and a discharge device that discharges solids collected on the bottom side of the storage tank to the outside of the storage tank, a receiving step of receiving the mixed liquid into the storage tank; a liquid sending step of sending the liquid in the mixed liquid stored in the storage tank out of the storage tank by the liquid sending mechanism utilizing the effect of the siphon principle, thereby lowering the liquid level in the storage tank; The method is characterized by having a discharge step in which, with the liquid level in the storage tank lowered below a predetermined height by the liquid transfer step, the solids collected on the bottom side are discharged outside the storage tank by the discharge device.

[0086] According to this method for driving a solid-liquid separator, the liquid level in the storage tank is lowered to increase the concentration of solids in the mixed liquid, and then the discharger discharges the solids. Therefore, devices other than a conveying device that conveys solids diagonally upward can be used as the discharger. Examples of dischargers other than conveying devices include gate devices such as belt gates or slide gates that slide to open the bottom of the storage tank, and gates with double-door openings. Furthermore, even when a conveying device using a screw conveyor, belt conveyor, or flight conveyor is used as the discharger, the solids are transported with the liquid level lowered, thereby shortening the transport path. This allows the solid-liquid separator to be made more compact.

[0087] In this method for driving a solid-liquid separator, the liquid transporting step may be a step of transporting the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank by utilizing potential energy of the liquid in the mixed liquid.

[0088] In the liquid transfer step, the potential energy of the liquid in the mixed liquid is utilized to transfer the liquid to the outside of the storage tank, so the liquid level in the storage tank can be lowered without providing a device such as a pump in the solid-liquid separation device.Since no device for lowering the liquid level is provided, the solid-liquid separation device can be constructed inexpensively.

[0089] In addition, in the method for driving the solid-liquid separator, the liquid sending mechanism has a flow rate adjusting unit between the inlet and the outlet that adjusts the amount of liquid in the mixed liquid sent out to the outside of the storage tank, The liquid sending step may be a step of sending the liquid in the mixed liquid to the outside of the storage tank at a flow rate adjusted by the flow rate adjustment unit.

[0090] In the liquid sending step, the amount of liquid in the mixed liquid sucked through the inlet is adjusted by the flow rate adjuster, so that solids collected on the bottom side along with the liquid in the mixed liquid can be prevented from being sucked through the inlet. The flow rate adjuster may be configured as an electric valve.

[0091] In the method for driving a solid-liquid separator, the liquid sending step may be a step of sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank by a pump.

[0092] By using the pump, the liquid in the mixed liquid stored in the storage tank can be reliably pumped out of the storage tank. Furthermore, if a pump with an adjustable suction volume is used, the adjustment of the suction volume of the pump can prevent the solids collected at the bottom from being sucked in together with the liquid in the mixed liquid.

[0093] Furthermore, in the method for driving the solid-liquid separator, the storage tank is provided with height position detection means for detecting a height position of the solids collected on the bottom side, The liquid transfer process may be a process of lowering the liquid level in the storage tank below the predetermined height based on the height position detection means detecting that the height position of the solids collected on the bottom side has reached a specific height position lower than the height position at which the inlet is located.

[0094] This prevents solids collected at the bottom from being sucked in along with the liquid during the liquid transfer process, while increasing the concentration of solids in the mixed liquid remaining in the storage tank when the liquid transfer process is completed.

[0095] The solid-liquid separation device described above includes a storage tank for storing a liquid containing solids mixed therein and poured through a supply port; a liquid delivery mechanism having an inlet disposed within the storage tank below the supply port and an outlet disposed outside the storage tank below the inlet, which utilizes the effect of the siphon principle to deliver the liquid in the mixed liquid stored in the storage tank from the inlet to outside the storage tank; a discharge device that discharges solids collected on the bottom side of the storage tank to the outside of the storage tank, The discharge device is characterized in that it discharges solids collected on the bottom side to the outside of the storage tank while lowering the liquid level in the storage tank below a predetermined height by sending the liquid in the mixed liquid stored in the storage tank out of the storage tank using the liquid delivery mechanism.

[0096] According to this solid-liquid separation apparatus, the liquid level in the storage tank is lowered to increase the solid concentration in the mixed liquid, and then the discharger discharges the solids. Therefore, devices other than a conveying device that conveys solids diagonally upward can be used as the discharger. Furthermore, even when a conveying device using a screw conveyor, belt conveyor, flight conveyor, or the like is used as the discharger, the solids are conveyed with the liquid level lowered, so the conveying path can be shortened. Therefore, the solid-liquid separation apparatus can be made smaller.

[0097] The solid-liquid separator further comprises a height position detection means for detecting a height position of the solids collected on the bottom side, The liquid delivery mechanism may lower the liquid level in the storage tank below the specified height based on the height position detection means detecting that the height position of the solids collected on the bottom side has reached a specific height position lower than the height position at which the inlet is located.

[0098] This prevents the liquid delivery mechanism from sucking in solids collected at the bottom along with the liquid, while increasing the concentration of solids in the mixed liquid remaining in the storage tank after the liquid level in the storage tank is lowered below the specified height.

[0099] The solid-liquid separation device described above includes a storage tank for storing a mixed liquid containing sand poured through a supply port; a liquid delivery mechanism having an inlet located within the storage tank below the supply port and an outlet located outside the storage tank, which delivers the liquid in the mixed liquid stored in the storage tank from the inlet to outside the storage tank; a discharge device that discharges sand collected on the bottom side of the storage tank to the outside of the storage tank; a height position detection means for detecting the height position of the sand collected on the bottom side, The storage tank has an opening formed at a lower end, The discharge device closes the opening, and by sending the liquid in the mixed liquid stored in the storage tank out of the storage tank by the liquid sending mechanism, the liquid level in the storage tank is lowered by a predetermined height, and the discharge device moves in an opening direction to open the opening, and the liquid is collected on the bottom side. The sand collected in the tank is discharged to the outside of the tank. the height position detection means and the inlet are disposed above an upstream end of the discharge device in the opening direction, The supply port is characterized in that it is disposed above the downstream side of the discharge device in the opening direction.

[0100] The solid-liquid separation device described above includes a storage tank for storing a mixed liquid containing sand poured through a supply port; a liquid delivery mechanism having an inlet located within the storage tank below the supply port and an outlet located outside the storage tank, which delivers the liquid in the mixed liquid stored in the storage tank from the inlet to outside the storage tank; a gate device that slides to open the bottom of the storage tank and discharges sand collected at the bottom of the storage tank to the outside of the storage tank; a height position detection means for detecting the height position of the sand collected on the bottom side, The storage tank is a rectangular cylindrical tank having an opening at its bottom end and a vertically extending side wall, The gate device closes the opening, and moves in an opening direction to open the opening while the liquid level in the storage tank is lowered below a predetermined height by sending the liquid in the mixed liquid stored in the storage tank out of the storage tank using the liquid sending mechanism, thereby discharging the sand collected on the bottom side to the outside of the storage tank, the height position detection means and the inlet are disposed above an upstream end of the gate device in the opening direction, The supply port is characterized in that it is disposed above the downstream side of the gate device in the opening direction. [Explanation of symbols]

[0101] 1 Solid-liquid separator 4. Reservoir 5 Belt Gate 6. Liquid supply pipe 621 Outlet 631 Inlet

Claims

[Claim 1] a storage tank for storing a mixed liquid containing sand poured through a supply port; a liquid delivery mechanism having an inlet located within the storage tank below the supply port and an outlet located outside the storage tank, which delivers the liquid in the mixed liquid stored in the storage tank from the inlet to outside the storage tank; a conveying device having a lower end portion of a conveying path extending obliquely upward and connected to the bottom of the storage tank, and an upper end portion of the conveying path located above the inlet, for conveying the sand in the mixed liquid that has settled to the bottom of the storage tank obliquely upward along the conveying path; The conveying device is characterized in that the liquid in the mixed liquid stored in the storage tank is sent out of the storage tank by the liquid sending mechanism, thereby lowering the liquid level in the storage tank below a predetermined height, and then draining the sand collected on the bottom side at the upper end portion while discharging it out of the storage tank.

Images