JP7663264B2 - Method for driving a solid-liquid separator - Google Patents

Description

The present invention relates to a method for operating a solid-liquid separator that separates liquid from a liquid containing solids.

Sewage treatment facilities are provided with grit basins for removing sand from wastewater and sedimentation basins for removing sludge from wastewater. In the grit basin, the sand contained in the wastewater that flows in is collected in a sand collection pit at the bottom of the basin, and then the sand-mixed water containing the collected sand is sucked up by a sand pump and transported to a solid-liquid separation device installed on the ground. This solid-liquid separation device receives the transported sand-mixed water, separates the sand and wastewater from the sand-mixed water, and returns the wastewater to the grit basin. In addition, the sedimentation basin collects the sludge contained in the received wastewater in a sludge pit at the bottom of the basin, and then transports the sludge-mixed water containing the sludge collected in the sludge pit to a solid-liquid separation device installed above the sedimentation basin by a sludge pump. The solid-liquid separation device installed above the sedimentation basin also receives the transported sludge-mixed water, separates the wastewater from the sludge-mixed water, and returns it to the sedimentation basin. Furthermore, solid-liquid separation devices that separate liquid from a mixed liquid containing solids are used in places other than sewage treatment facilities. Such solid-liquid separation devices include, for example, devices that separate water and metal powder from industrial wastewater, and devices that separate sediment 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, and sediment that flows into a reservoir with water may be collectively referred to as solids. Liquids that have solids mixed in them may also be collectively referred to as mixed liquids.

A known example of such a solid-liquid separation device is one that includes a concentration container, a concentrated liquid tank, and a conveying device (see, for example, Patent Document 1, etc.). The concentration container in Patent Document 1 is located above the concentrated liquid tank and is connected to a sand lifting pump located in the settling basin by a sand lifting pipe. The concentration container receives the sand-mixed water transferred from the settling basin by the sand lifting pump, and discharges the concentrated liquid, which has a higher sand concentration relative to the wastewater than the sand-mixed water, from an outlet provided in the concentration container. The concentrated liquid tank receives and stores the concentrated liquid discharged from the concentration container. The conveying device is connected to the lower end of the concentrated liquid tank and extends diagonally upward from the connected part. The sand that has settled in the lower end of the concentrated liquid tank is conveyed diagonally upward by the conveying device while being drained, and is sent to the outside of the concentrated liquid tank.

JP 2012-21483 A

Recently, however, there has been a demand for more efficient separation of solids and liquids.

In view of the above circumstances, the present invention aims to provide a method for driving a solid-liquid separation device that can efficiently separate solids and liquids.

The present invention provides a method for driving a solid-liquid separation apparatus that achieves the above object, the method comprising: a concentration container that receives a mixed liquid in which solids are mixed into a liquid and discharges from an outlet a concentrated liquid in which the concentration of solids in the liquid has increased; a concentrated liquid tank having the outlet disposed within the tank and storing the concentrated liquid obtained in the concentration container; a transport device having a transport path whose lower end portion extends obliquely upward and is connected to the bottom of the concentrated liquid tank, whose upper end portion is disposed above the outlet and which is provided with a drop portion extending downward from near the upper end of the transport path; and a liquid delivery pipe whose inlet is connected to the concentration container and whose outlet is disposed outside the concentrated liquid tank and below the inlet, the method comprising the steps of: collecting solids in the concentrated liquid at the lower end portion; driving the transport device to transport the solids obliquely upward along the transport path; and sending the liquid in the mixed liquid received by the concentration container to the outside of the concentrated liquid tank through the liquid delivery pipe,
a filling step of raising the liquid level in the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container;
a driving step of driving the conveying device at a speed at which a liquid component contained in the concentrated liquid does not reach the dropping portion, and conveying the solids collected in the lower end portion,
The filling step and the driving step are performed simultaneously.

The present invention provides a method for driving a solid-liquid separator that can efficiently separate solids and liquids.

1 is a schematic diagram showing a solid-liquid separation device according to one embodiment of the present invention. 1A is a plan view of the concentration container, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A is a plan view showing the concentration container and the concentrated liquid tank, FIG. 1B is a front view showing the concentration container and the concentrated liquid tank, and FIG. 1C is a cross-sectional view taken along line BB in FIG. 2 is a flowchart showing the operation of the solid-liquid separation apparatus shown in FIG. 1 . 3(a) is a front view similar to FIG. 3(b) showing a modified example of the solid-liquid separation device shown in FIG. 1, and FIG. 3(b) is a cross-sectional view taken along the line CC in FIG. 3(a). 5A is a front view similar to FIG. 3B of a solid-liquid separator according to a modified example different from the modified example shown in FIG. 5, and FIG. FIG. 5 is a front view similar to FIG. 3( b ) of a solid-liquid separator according to a second embodiment. 8 is a flowchart showing the operation of the solid-liquid separation device shown in FIG. 7 . 8 is a front view similar to FIG. 7, showing a modification of the solid-liquid separation device shown in FIG. 7.

Below, an embodiment of the present invention will be described with reference to the drawings. In the description of this embodiment, an example is used in which the driving method of the present invention is applied to a solid-liquid separation device to which wastewater containing sand is transferred from a grit basin. The grit basin is located upstream of a sewage treatment facility and is used 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 sedimentation basin or the like located downstream.

Figure 1 is a schematic diagram showing a solid-liquid separation device according to one embodiment of the present invention. This figure also shows a grit basin.

As shown in FIG. 1, the sedimentation 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 sedimentation basin 9 from the right side of the figure. The sewage flows slowly toward the left side of the figure. In the sedimentation basin 9, as the sewage flows, 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 sedimentation basin 9. The pump well 91 stores the sewage from which the sand has been removed. A lifting pump 911 is provided inside the pump well 91. The lifting pump 911 discharges the sewage stored in the pump well 91 to the outside of the sedimentation basin 9. A lifting pipe 912 is connected to the lifting pump 911. The sewage sucked up by the lifting pump 911 is sent through the lifting pipe 912 to a sedimentation basin (not shown). In addition, the sewage pond water level WL1 is also shown in Figure 1. The position of this pond water level WL1 varies in height from the bottom of the trough 92, for example, in the range of 1 m to 5 m, depending on the amount of sewage flowing into the settling basin 9.

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

The sand collection nozzle 93 is disposed at the upstream end of the trough 92. Wastewater pumped from the sedimentation basin is supplied to the sand collection nozzle 93. 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 accumulated 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 transferred to the solid-liquid separation device 1 together with the wastewater, and separated into a solid (sand) and a liquid (wastewater).

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

The solid-liquid separation device 1 includes a concentration container 3, a concentrated liquid tank 4, a conveying device 5, and a liquid supply pipe 6. The concentration container 3, the concentrated liquid tank 4, and the conveying device 5 are arranged on the ground near the grit basin 9. The concentration container 3 is arranged in the tank of the concentrated liquid tank 4. The concentration container 3 separates a part of the wastewater in the transferred sand-containing water from the sand and sends it to the liquid supply pipe 6. Hereinafter, the wastewater separated from the sand-containing water is referred to as separated water. In addition, the concentration container 3 discharges a concentrated liquid in which the concentration of sand relative to the wastewater is increased by removing a part of the wastewater to the concentrated liquid tank 4. The wastewater contained in this concentrated liquid also corresponds to an example of a liquid. The separated water sent from the concentration container 3 is returned to the grit basin 9 through the liquid supply pipe 6. The liquid supply pipe 6 has one end portion 61 (see FIG. 2) inserted into the concentration container 3, a horizontal portion extending horizontally above the concentration container 3, and a vertical portion bent from the horizontal portion and extending downward. The outlet 62 formed at the bottom end of the vertical portion is located above the grit basin 9, below the concentration container 3 and outside the concentrated liquid tank 4. The concentration container 3 and concentrated liquid tank 4 will be described in detail later.

The conveying device 5 extends obliquely upward from the lower end of the concentrated liquid tank 4. The conveying device 5 has a screw conveyor 51, a throwing part 52, and a cylindrical part 53 that covers the outside of the screw conveyor 51. The screw conveyor 51 is arranged in the cylindrical part 53. The axial direction of the screw conveyor 51 coincides with the extension direction of the conveying device 5. The screw conveyor 51 forms a conveying path that extends obliquely upward. The lower end part of this conveying path is connected to the bottom of the concentrated liquid tank 4. The upper end part of the conveying path is arranged above the discharge port 331 (see FIG. 2 (b)) of the concentration container 3. The sand contained in the concentrated liquid discharged into the concentrated liquid tank 4 settles in the concentrated liquid tank 4 and collects at the lower end of the concentrated liquid tank 4. The sand that has collected at the lower end of the concentrated liquid tank 4 is conveyed obliquely upward by the rotation of the screw conveyor 51, and is conveyed while being drained at the upper end part of the conveying path of the conveying device 5. The throwing part 52 is a tube extending downward from near the upper end of the screw conveyor 51, and a throwing port 52a is formed at the lower end. The upper end of the throwing part 52 is connected to an opening formed at the lower part near the upper end of the cylindrical part 53. The sand drained by the transport by the screw conveyor 51 is dropped downward from the throwing port 52a through the throwing part 52. That is, the transport device 5 transports the sand contained in the concentrated liquid received in the concentrated liquid tank 4 to the outside of the concentrated liquid tank 4. Note that, instead of the screw conveyor 51, other transport mechanisms such as a belt conveyor or a flight conveyor may be used. Note that, an opening and closing lid that can freely close and open the throwing part 52 may be provided on the throwing part 52, and the throwing part 52 may be closed when the transport device 5 is not driven. The closing lid is preferably formed at the upper end of the throwing part 52, i.e., between the throwing part 52 and the cylindrical part 53, but may be provided near the throwing port 52a. By providing an opening and closing lid, it is possible to prevent the concentrated liquid from leaking out of the pouring part 52 even if the tank water level WL2 rises above the upper end of the pouring part 52.

Figure 2(a) is a plan view of the concentration container, and Figure 2(b) is a cross-sectional view taken along the line A-A in Figure 2(a). Figures 2(a) and 2(b) also show one end of the liquid delivery tube.

As shown in FIG. 2(b), the concentration container 3 includes a fluid inlet 31, a throttle section 32, a discharge section 33, a fluid inlet pipe 34, and a pair of mounting sections 36. The concentration container 3 in this embodiment is a so-called fluid cyclone device. The fluid inlet 31 is provided in the upper part of the concentration container 3. The upper end of the throttle section 32 is connected to the lower end of the fluid inlet 31. The upper end of the discharge section 33 is connected to the lower end of the throttle section 32. The inner circumferential surface 3a of the concentration container 3 is composed of the inner circumferential surface 31a of the fluid inlet 31, the inner circumferential surface 32a of the throttle section 32, and the inner circumferential surface 33a of the discharge section 33. The inner circumferential surface 3a of the concentration container 3 defines an internal space X1. That is, the fluid inlet 31, the throttle section 32, and the discharge section 33 form a hollow tank having an internal space X1.

The fluid introduction section 31 includes a cylindrical section 311 having a cylindrical inner surface 31a and a lid 312 that closes the upper end of the cylindrical section 311. The cylindrical section 311 is a steel plate having a thickness of 3.2 mm that is processed into a cylindrical shape with an inner diameter of 500 mm. The lid 312 is a steel plate having a thickness of 6.0 mm that is 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 appropriately selected according to the size of the internal space X1. The cylindrical section 311 may be a cone-shaped or dome-shaped section in which the cross-sectional area of the internal space X1 increases downward. The cylindrical section 311 may be a cone-shaped or dome-shaped section in which the cross-sectional area of the internal space X1 increases downward in the upper part where the receiving port 341 described later is formed, and the lower part may be a cylindrical section. A pair of mounting parts 36 are fixed to the outer circumferential surface of the cylindrical part 311. These mounting parts 36 are used to fix the concentration container 3 to the concentrated liquid tank 4 shown in FIG. 1.

In addition, the fluid inlet pipe 34 is connected to the upper part of the cylindrical portion 311. The sand lifting pump 941 and the fluid inlet pipe 34 shown in FIG. 1 are connected via the sand lifting pipe 942. The sand lifting pipe 942 and the fluid inlet pipe 34 are detachably connected by fastening the flanges provided at the connection 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 portion between the fluid inlet pipe 34 and the cylindrical portion 311. As shown by the straight arrow in FIG. 2(a), the sand-mixed water sucked up by the sand lifting pump 941 is introduced into the internal space X1 from the tangential direction of the inner peripheral surface 31a of the cylindrical portion 311 through the receiving port 341. Therefore, the sand-mixed water received by the concentration container 3 is introduced between the outer peripheral surface of one end portion 61 of the liquid supply pipe 6 and the inner peripheral surface 31a of the cylindrical portion 311. This creates a swirling flow of sand-mixed water in the internal space X1.

The throttling section 32 is disposed between the receiving port 341 and the discharge port 33. In this throttling section 32, the cross-sectional area of the internal space X1 decreases toward the discharge port 33. In other words, the throttling section 32 has an inverted cone-shaped inner peripheral surface 32a that gradually reduces in diameter as it moves away from the cylindrical section 311. The throttling section 32 may have a cross-sectional area of the internal space X1 that gradually decreases toward the discharge port 331. That is, the throttling section 32 is formed so that the cross-sectional area of the internal space X1 is smaller on the discharge port 331 side than on the receiving port 341 side. The throttling section 32 is formed by processing a steel plate with a plate thickness of 3.2 mm into a cone shape, and the upper end is formed with an inner diameter of 500 mm and the lower end is formed with an inner diameter of 100 mm. The material and thickness of the throttling section 32 may be appropriately selected according to the size of the internal space X1, the amount of throttling, etc. 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 container 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.

The discharge section 33 is connected to the side of the throttling section 32 opposite to 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 throttling 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 throttling section 32. The opening at the lower end of this discharge section 33 becomes the discharge port 331. Note that the discharge section 33 may be omitted. In that case, the opening at the lower end of the throttling section 32 becomes the discharge port.

One end portion 61 of the liquid supply tube 6 penetrates the lid 312 of the fluid introduction section 31 in the vertical direction. This one end portion 61 extends from below the lower end of the lid 312 to above the upper end of the lid 312 along the radial center axis of the cylindrical portion 311, and is joined to the lid 312 in a watertight state by welding. Therefore, the lower part of the one end portion 61 protrudes into the internal space X1. However, the lower part of the one end portion 61 does not have to protrude into the internal space X1, and for example, the lower surface of the lid 312 and the lower end of the one end portion 61 may be on the same plane. The one end portion 61 has a tubular shape with an inner diameter of 100 mm. The lower end of this one end portion 61 becomes one end of the liquid supply tube 6, and the opening of the one end becomes the inlet 611. Therefore, the one end portion 61 and the inlet 611 (one end of the liquid supply tube 6) are connected to the concentration container 3. In addition, the inlet 611 in this embodiment is arranged in the internal space X1. The separated water separated from the sand-containing water is returned to the grit basin 9 through the inlet 611 through the liquid supply pipe 6. The inlet 611 is located below the receiving port 341. The part of the liquid supply pipe 6 other than the one end portion 61 and the one end portion 61 are detachably connected by fastening with a bolt. The length of the one end portion 61 in the extension direction is arbitrary, and for example, the lower part of the one end portion 61 (the part inside the internal space X1) may be formed longer than the fluid introduction part 31. In this case, the inlet 611 is formed in a region of the internal space X1 defined by the inner circumferential surface 32a of the throttling part 32. In addition, although an example has been shown in which the cross-sectional area of the inlet 611 is the same as the cross-sectional area of the lower end of the throttling part 32, it is preferable that the cross-sectional area of the inlet 611 is equal to or larger than the cross-sectional area of the discharge port 331. In this way, the amount of separated water discharged from the inlet 611 can be increased, and the pressure loss in the concentration container 3 can be reduced.

Next, the operation of the concentration container 3 will be described mainly with reference to FIG. 2. As described above, by driving the sand pump 941 (see FIG. 1), the sand-mixed water flows into the internal space X1 from the receiving port 341, and a swirling flow of the sand-mixed water is formed in the internal space X1. The sand contained in the sand-mixed water has a larger specific gravity than the wastewater, so it is pressed against the inner circumferential surface 3a of the concentration container 3 by centrifugal force and gradually falls downward while rotating along the inner circumferential surface 3a. Meanwhile, separated water from which sand has been removed from the sand-mixed water is collected in the radial center of the cylindrical portion 311. The separated water is discharged from the inlet 611. However, since the size of the receiving port 341 and the outlet 331 of the concentration container 3 of this embodiment is the same, depending on the amount of sand-mixed water received from the receiving port 341 per unit time, a concentrated liquid tank 4, which will be described in detail later, needs to be provided in order to discharge the separated water from the inlet 611. As shown in FIG. 1, the separated water is discharged toward the grit basin 9 through the liquid supply pipe 6 from the outlet 62 formed at the other end of the liquid supply pipe 6. The outlet 62 formed at the other end of the liquid supply pipe 6 is disposed below the inlet 611 formed at one end of the liquid supply pipe 6. Therefore, when the liquid supply pipe 6 is filled with liquid, the sand-mixed water (separated water) in the internal space X1 is forced to flow out of the inlet 611 to the grit basin 9 due to the principle of a siphon. This produces the effect that the sand-mixed water can be transported to the concentration container 3 even if the power of the sand lifting pump 941 is small. 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 62 is submerged in water. An intermediate tank may be provided between the concentration container 3 and the grit basin 9, and the separated water flowing out from the outlet 62 may be stored in the intermediate tank. By providing the intermediate tank, the state of the separated water can be confirmed by the separated water accumulated in the intermediate tank. Furthermore, even if a small amount of sand is sent out from the inlet 611 along with the separated water, the sand can be allowed to settle in the intermediate tank and the supernatant liquid of the intermediate tank returned to the settling tank 9, thereby further preventing the sand from being returned to the settling tank 9.

Figure 3(a) is a plan view showing the concentration container and the concentrated liquid tank, Figure 3(b) is a front view showing the concentration container and the concentrated liquid tank, and Figure 3(c) is a cross-sectional view taken along line B-B in Figure 3(b).

3(a) and 3(b), the concentrated liquid tank 4 has a side wall 41 that is disposed outside the outer peripheral side surface 3b of the concentrated liquid container 3 and extends above the discharge port 331. As shown in FIG. 3(c), in this embodiment, the side wall 41 extends above the upper end 6c of the liquid supply pipe 6. The concentrated liquid container 3 is detachably fixed in the concentrated liquid tank 4 by connecting the mounting portion 36 with a bolt to a pair of arms 42 that are fixed at one end to the inner peripheral surface of the side wall 41 and extend inward. As shown in FIG. 3(b) and 3(c), the liquid supply pipe 6 and the sand lift pipe 942 penetrate the side wall 41 of the concentrated liquid tank 4. The penetration parts of the liquid supply pipe 6 and the sand lift pipe 942 are welded to the side wall 41, and the penetration parts are watertight.

The concentrated liquid tank 4 is a tank having a substantially square shape in a plan view with two tank inclined surfaces 41a formed on the lower part. The lower end of the concentrated liquid tank 4 is cut diagonally upward at the same angle as the inclination angle of the conveying device 5. The tank inclined surface 41a is formed at a certain height from the lower end of the concentrated liquid tank 4. The lower end of this tank inclined surface 41a is connected to the conveying device 5. The sand contained in the concentrated liquid discharged from the discharge port 331 of the concentration container 3 slides down the tank inclined surface 41a and is deposited in the conveying device 5 connected to the lower end of the concentrated liquid tank 4. As described above, the sand deposited in the conveying device 5 is transported diagonally upward by the screw conveyor 51 and is dropped from the drop part 52 (see FIG. 1) at the upper end part. As shown in FIG. 3(c), an overflow port 43 is formed above the discharge port 331 and slightly below the upper end of the concentrated liquid tank 4. This overflow port 43 allows the supernatant of the concentrated liquid to flow out of the concentrated liquid tank 4 when too much concentrated liquid is discharged from the discharge port 331. The supernatant liquid that flows out from the overflow port 43 is returned to the grit basin 9 (see FIG. 1) through the overflow pipe 7. Providing this overflow port 43 prevents the concentrated liquid from overflowing from the top end of the side wall 41 of the concentrated liquid tank 4.

Figure 4 is a flowchart showing the operation of the solid-liquid separation device shown in Figure 1.

The operations of the grit basin 9 and the solid-liquid separation device 1 are centrally controlled by a control device (not shown). Note that the grit basin 9 and the solid-liquid separation device 1 may each be provided with a control device, and may be configured to be capable of transmitting and receiving information or commands to each other. At a predetermined time when a certain amount of sand has accumulated on the bottom surface of the grit basin 9 shown in FIG. 1, the grit basin 9 performs a sand collection operation in which wastewater is discharged from the sand collection nozzle 93 to collect the sand in the sand collection pit 94. After the sand collection operation, the solid-liquid separation device 1 starts a solid-liquid separation operation. The predetermined time may be, for example, periodically, such as once a month, or when the total flow rate of wastewater flowing into the grit basin 9 or the total flow rate of wastewater discharged from the grit basin 9 reaches a certain amount. Note that the solid-liquid separation operation may be started while sand is being collected in the sand collection pit 94.

In the solid-liquid separation operation, first, the sand lifting pump 941 is started with the conveying device 5 stopped. This start of driving starts the reception of sand-mixed water in the concentration container 3 shown in FIG. 3 (step S1). The conveying device 5 does not have to be completely stopped, and may be driven at a slow speed at which the liquid components contained in the concentrated liquid do not reach the drop section 52 by the driving of the conveying device 5. That is, the conveying device 5 may be driven at a driving speed slower than a predetermined driving speed described later. If the internal space X1 (see FIG. 2(b)) of the concentration container 3 and the tank of the concentrated liquid tank 4 are empty before the driving of the sand lifting pump 941 starts, most of the sand-mixed water supplied to the internal space X1 is discharged from the discharge port 331. As the concentrated liquid discharged from the discharge port 331 is stored in the tank of the concentrated liquid tank 4, the tank water level WL2, which is the water level formed by the concentrated liquid stored in the concentrated liquid tank 4, gradually rises. This tank water level WL2 corresponds to an example of a liquid level. In addition, the sand contained in the concentrated liquid stored in the concentrated liquid tank 4 sinks toward the bottom of the concentrated liquid tank 4 due to its own weight and gathers at the lower end of the transport path of the transport device 5. When the tank water level WL2 reaches the discharge port 331, the discharge port 331 is blocked by the concentrated liquid, and the amount of concentrated liquid discharged from the discharge port 331 decreases. That is, the resistance due to the reduction in the cross-sectional area of the internal space X1 in the constricted section 32 and the water pressure of the concentrated liquid applied to the discharge port 331 combine to make it difficult for the concentrated liquid to be discharged from the discharge port 331, and the separated water begins to be sent out from the inlet 611 (see FIG. 2(b)). As the tank water level WL2 rises, the water pressure of the concentrated liquid applied to the discharge port 331 increases, so the amount of concentrated liquid discharged from the discharge port 331 decreases, and the amount of separated water sent out from the inlet 611 increases, and the liquid supply pipe 6 is filled with separated water (liquid). As described above, when the liquid supply pipe 6 is filled with the separated water, the separated water acts to flow out to the grit basin 9 due to the principle of a siphon. That is, due to the potential energy of the liquid in the sand-containing water and the concentrated liquid, the separated water starts to be sent out of the concentrated liquid tank 4 through the liquid supply pipe 6. As a result, the amount of separated water sent out from the inlet 611 further increases, and the amount of concentrated liquid discharged from the outlet 331 further decreases. When the amount of sand-containing water supplied to the internal space X1 is, for example, 1.0 m3/min, when the tank water level WL2 becomes slightly lower than the receiving port 341 (see FIG. 2(b)), almost only sand is discharged from the outlet 331, and the tank water level WL2 stops rising. The tank water level WL2 at this time is shown in FIG. 3(b) and FIG. 3(c). In addition, when the amount of sand-mixed water supplied to the internal space X1 is set to, for example, 1.5 m3/min, the amount of separated water sent out from the inlet 611 also increases, but concentrated liquid containing a certain proportion of sewage is discharged from the outlet 331, and the tank water level WL2 continues to rise. After the tank water level WL2 reaches the overflow port 43, the supernatant liquid of the sand-mixed water flows out from the overflow port 43 at about 0.3 m3/min. In addition, before the sand lifting pump 941 is driven, sewage or tap water stored in the settling tank may be flowed into the concentrated liquid tank 4 to fill the concentrated liquid tank 4 with liquid. When the concentrated liquid tank 4 is filled with liquid, the internal space X1 is also filled with liquid to the same height as the concentrated liquid tank 4. Therefore, if liquid is stored so that the tank water level WL2 is equal to or higher than the height of the inlet 611, separated water can be sent from the inlet 611 almost simultaneously with the driving of the sand lifting pump 941. When the sand lifting pump 941 is driven for the second or subsequent times, separated water can be sent from the inlet 611 almost simultaneously with the driving of the sand lifting pump 941, unless the liquid stored in the concentrated liquid tank 4 is drained.

The sand lifting pump 941 continues to be driven for a first predetermined time from the start of driving (step S2). Steps S1 and S2 described above correspond to an example of a filling process. This first predetermined time is a sufficient time to raise the tank water level WL2 above the discharge port 331 and fill the liquid supply pipe 6 with separated water. A water level sensor that detects when the tank water level WL2 has risen above the discharge port 331 may be provided in the concentrated liquid tank 4, and a water detection sensor that detects when the liquid supply pipe 6 is filled with separated water may be provided in the liquid supply pipe 6. Then, instead of determining whether the first predetermined time has elapsed, it may be determined whether detection by these sensors has occurred.

After the first predetermined time has elapsed, the operation of the sand pump 941 is stopped (step S3). Even after the operation of the sand pump 941 is stopped, the concentrated liquid and the sand-mixed water still act to flow out through the liquid feed pipe 6 to the sand settling basin 9 due to the effect of the siphon principle described above. As a result, the supernatant liquid of the concentrated liquid and the sand-mixed water flows out through the liquid feed pipe 6 to the sand settling basin 9, and the tank water level WL2 drops. In other words, the wastewater in the concentrated liquid stored in the concentrated liquid tank 4 is sent to the outside of the concentrated liquid tank 4 through the liquid feed pipe 6 using the potential energy of the wastewater, thereby lowering the tank water level WL2. Meanwhile, even while the tank water level WL2 is lowering, the sand contained in the concentrated liquid and the sand-mixed water gradually settles due to its own weight and gathers at the lower end of the transport path of the transport device 5. When the tank water level WL2 falls to the discharge port 331, air flows from the discharge port 331 through the concentration container 3 into the liquid feed pipe 6, and the effect of the siphon principle ends. Until the second predetermined time has elapsed since the driving of the sand lifting pump 941 has stopped, the state immediately after the sand lifting pump 941 was stopped is maintained (step S4). The above-described steps S3 and S4 correspond to an example of a liquid feed process. This second predetermined time is the time for the tank water level WL2 to fall to the vicinity of the discharge port 331. Note that this second predetermined time may be shorter than the time for the tank water level WL2 to fall to the vicinity of the discharge port 331, as long as it is the time for the tank water level WL2 to fall to a position lower than the height of the upper end part of the transport path of the transport device 5. In addition, instead of determining whether the second predetermined time has elapsed, a water level sensor that detects that the tank water level WL2 has fallen to a position lower than the height of the upper end part of the transport path of the transport device 5 may be provided in the concentrated liquid tank 4, and whether or not the detection has occurred may be determined. Furthermore, in steps S3 and S4, a small amount of sand-mixed water may be supplied to the concentration container 3 without completely stopping the operation of the sand pump 941, as long as the amount is enough to lower the tank water level WL2.

After the second predetermined time has elapsed, the driving of the conveying device 5 is started (step S5). By driving the conveying device 5 at a predetermined driving speed, the sand collected at the lower end of the conveying path is conveyed to the upper end of the conveying path. At the time of starting this driving, the tank water level WL2 is lowered to a position lower than the upper end of the conveying path, so the sand conveyed by the screw conveyor 51 is conveyed while being drained at the upper end of the conveying path. Then, the sand that has reached the upper end of the dropping part 52 is dropped downward from the drop port 52a. The driving of the conveying device 5 continues from the start of driving until the third predetermined time has elapsed (step S6). Steps S5 and S6 described above correspond to an example of the conveying process. This third predetermined time is the time during which most of the sand collected at the lower end of the conveying path can be conveyed and dropped from the drop part 52. Note that instead of determining whether the third predetermined time has elapsed, a sand presence/absence sensor that detects the presence or absence of sand at the lower end of the conveying path may be provided at the bottom of the concentrated liquid tank 4, and whether or not the detection has occurred may be determined. After the third predetermined time has elapsed, the drive of the conveying device 5 is stopped (step S7), and the solid-liquid separation operation is terminated.

According to this method of driving the solid-liquid separation device, the tank water level WL2 of the concentrated liquid tank 4 is lowered, and then the conveying device 5 is driven, so that even if the conveying path is short, the sand can be conveyed while being drained. That is, the height of the conveying path can be lowered from the normal level at least by the amount by which the tank water level WL2 is lowered in the above-mentioned steps S3 and S4. Since the conveying path extends diagonally upward, the width of the conveying device 5 can be shortened by lowering the height of the conveying device 5. As a result, the solid-liquid separation device 1 can be made smaller. In addition, in the above-mentioned steps S3 and S4, the potential energy of the wastewater in the concentrated liquid is used to send it outside the concentrated liquid tank 4, so the liquid level of the concentrated liquid tank 4 can be lowered without providing a device such as a pump in the solid-liquid separation device 1.

In addition, in the above-mentioned step S2, the discharge port 331 is blocked by the liquid stored in the concentrated liquid tank 4, so that the water pressure of the liquid stored in the tank of the concentrated liquid tank 4 is generated at the discharge port 331. This water pressure makes it difficult for the concentrated liquid to be discharged from the discharge port 331, so that the amount of separated water sent out through the liquid feed pipe 6 can be increased. That is, the ratio of separated water sent out from the inlet 611 to the concentrated liquid discharged from the discharge port 331 increases, so that the separation efficiency in the concentration container 3 is improved. In addition, since the concentrated liquid discharged to the concentrated liquid tank 4 is small, the concentrated liquid tank 4 can be made smaller. Furthermore, even if the amount of throttling (amount of reduction in cross-sectional area) in the throttling section 32 is reduced, the amount of concentrated liquid discharged from the discharge port 331 can be suppressed. By reducing the amount of throttling in the throttling section 32, the pressure loss in the concentration container 3 can be reduced, so that the power of the sand lifting pump 941 can be reduced. Furthermore, the concentrated liquid discharged from the discharge port 331 does not scatter, and the sand contained in the concentrated liquid easily settles to the bottom of the concentrated liquid tank 4 in a short time. In addition, because the separated water tends to flow out of the inlet 611 into the grit basin 9 due to the siphon principle, the power required for the sand lifting pump 941 can be further reduced. In addition, the transport device 5 is connected to the concentrated liquid tank 4, and the concentrated liquid tank 4 and the concentration container 3 are arranged in a position where they overlap in the height direction, so the height of the entire solid-liquid separation device 1 can be reduced. And, because the concentration container 3 can be arranged in a position close to the ground, the head required for the sand lifting pump 941 is lowered, and the mixed water can be transferred to the concentration container 3 with even less power.

In addition, in this embodiment, the side wall 41 of the concentrated liquid tank 4 extends above the upper end of the internal space X1, so that liquid can be stored in the tank of the concentrated liquid 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 is increased, and the force of the wastewater in the sand-mixed water in the internal space X1 trying to flow out of the discharge port 331 due to gravity can be countered. This further suppresses the amount of wastewater discharged from the discharge port 331, and the concentration of sand in the concentrated liquid can be further increased. In addition, since the amount of concentrated liquid discharged from the discharge port 331 to the concentrated liquid tank 4 is reduced, the size of the concentrated liquid tank 4 can be reduced. Furthermore, the amount of reduction in the throttle section 32 can be reduced to further reduce pressure loss. In addition, the height of the side wall 41 of the concentrated liquid tank 4 is set higher than the upper end 6c of the liquid supply pipe 6, so 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 separated water, and the effect of the siphon principle can be obtained.

Next, a modified example of the solid-liquid separation device of this embodiment will be described. In the following description, the names of components that are the same as those described so far may be assigned the same reference numerals as those used so far, and duplicate descriptions may be omitted.

Figure 5(a) is a front view similar to Figure 3(b) showing a modified example of the solid-liquid separation device shown in Figure 1, and Figure 5(b) is a cross-sectional view taken along the line C-C in Figure 5(a).

As shown in FIG. 5(a), the solid-liquid separation device 1 of this modification is different from the solid-liquid separation device 1 shown in FIGS. 1 to 4 in that the fine bubble water supply pipe 8 is connected to the sand lift pipe 942 and the height of the concentrated liquid tank 4 is low. In this modification, nanobubble water generated by a nanobubble water generator (not shown) is supplied to the sand lift pipe 942 through the fine bubble water supply pipe 8. However, microbubble water may be supplied to the sand lift pipe 942 instead of nanobubble water, and micro-nano bubble water, which is a mixture of nanobubble water and microbubble water, may be supplied to the sand lift pipe 942. This fine bubble water supply pipe 8 corresponds to an example of a fine bubble supplying means. Nanobubble water means water containing air bubbles with a particle size of nanometer order. Microbubble water means water containing air bubbles of micrometer order. Note that water containing oxygen bubbles of nanometer order may be used as nanobubble water. Similarly, water containing oxygen bubbles of micrometer order may be used as microbubble water. The fine bubble water supply pipe 8 may also be directly connected to the concentration container 3. That is, the fine bubble water supply pipe 8 may be connected between the sand pump 941 (see FIG. 1) and the discharge port 331. Nanobubble water and microbubble water have a cleaning effect, so adding them to sand-mixed water can clean the sand and dirty water contained in the sand-mixed water. By adding nanobubble water or microbubble water to the sand-mixed water between the sand pump 941 (see FIG. 1) and the discharge port 331, the sand-mixed water can be cleaned with a high cleaning effect in the internal space X1 (see FIG. 2) of the concentration container 3. That is, the nanobubbles and microbubbles are mixed with the sand-mixed water in the internal space X1 by the swirling flow generated in the internal space X1, so that a high cleaning effect can be achieved.

The side wall 41 of the concentrated liquid tank 4 extends to a height above the upper end of the concentration container 3 and below the upper end 6c of the liquid supply pipe 6. As in the previous embodiment, if the side wall 41 of the concentrated liquid tank 4 is made higher, it is possible to make the tank water level WL2 of the concentrated liquid tank 4 higher than the upper end 6c of the liquid supply pipe 6. As described above, the water pressure applied to the discharge port 331 increases according to the height of the tank water level WL2, so a higher tank water level WL2 is preferable in terms of further increasing the concentration of sand in the concentrated liquid and reducing pressure loss. However, if the side wall 41 of the concentrated liquid tank 4 is made too high, the height of the entire solid-liquid separation device 1 will also increase, and the manufacturing cost of the concentrated liquid tank 4 will also become expensive, so in this sense it is preferable that the height of the side wall 41 of the concentrated liquid tank 4 is low. If the side wall 41 extends above the discharge port 331, the discharge port 331 can be blocked by the liquid stored in the concentrated liquid 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 according to 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 FIG. 2(b)).

Next, we will explain a modification of the solid-liquid separation device shown in Figure 1 that is different from the modification shown in Figure 5.

Figure 6(a) is a front view similar to Figure 3(b) of a solid-liquid separation device of a modified example different from the modified example shown in Figure 5, and Figure 6(b) is a cross-sectional view taken along line D-D in Figure 6(a).

The solid-liquid separation device 1 shown in Figures 6(a) and 6(b) differs from the solid-liquid separation device 1 shown in Figures 1 to 4 in that the constriction container 3 does not have a constriction section 32 and a discharge section 33, the height of the concentrated liquid tank 4 is low, and the position of the overflow port 43. The concentration container 3 is composed of a fluid introduction section 31. Therefore, the internal space X1 is defined only by the inner circumferential surface 31a of the fluid introduction section 31. The lower end of the concentration container 3 is the lower end of the cylindrical section 311, and the opening of the lower end becomes the discharge port 331. This discharge port 331 is an opening with a diameter of 500 mm, which is considerably larger than the receiving port 341 (see Figure 2(b)). Therefore, in this modified example, there is almost no pressure loss in the concentration container 3. The concentrated liquid tank 4 is formed lower by the total height of the constriction section 32 and the discharge section 33 compared to the concentrated liquid tank 4 shown in Figure 3. In addition, the receiving port 341 formed in the concentration container 3 is located at a position close to the lower end of the concentrated liquid tank 4 by the total height. The length (height) of the conveying device 5 can also be reduced by the amount that the height of the concentrated liquid tank 4 is reduced. That is, by lowering the height of the concentration container 3, the height of the entire solid-liquid separation device 1 can be reduced, and the solid-liquid separation device 1 can be made smaller. In addition, since the receiving port 341 is located at a position close to the ground, the lift 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. The overflow port 43 is located at the same height as the receiving port 341. However, the overflow port 43 may be located at a position higher than the receiving port 341 or at a position higher than the upper end 6c of the liquid supply pipe 6. By locating it at a higher position, the liquid can be quickly stored in the concentrated liquid tank 4 up to a position higher than the upper end 6c of the liquid supply pipe 6, and 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 generated can be shortened.

The operation of the solid-liquid separation device 1 of this modified example is similar to that of the solid-liquid separation device 1 shown in Figures 1 to 4, but the behavior of the sand-mixed water and the concentrated liquid in steps S1 and S2 shown in Figure 4 is slightly different, so these behaviors will be mainly described. When the internal space X1 of the concentration container 3 and the tank of the concentrated liquid tank 4 are empty, and the sand-mixed water starts to be supplied to the internal space X1 when the sand pump 941 shown in Figure 1 is driven, the sand-mixed water starts to be supplied to the internal space X1. In this modified example, 2.0 m3/min of sand-mixed water is supplied to the internal space X1. Since the sand-mixed water is introduced into the internal space X1 from the tangential direction of the inner peripheral surface 31a of the cylindrical portion 311 through the receiving port 341 (see Figure 2 (b)), a swirling flow of the sand-mixed water is formed in the internal space X1. Since the sand contained in the sand-mixed water has a larger specific gravity than the wastewater, it is pressed against the inner peripheral surface 31a of the cylindrical portion 311 by centrifugal force and gradually falls downward while swirling along the inner peripheral surface 31a. Meanwhile, separated water from which sand has been removed remains near the center of the diameter of the cylindrical portion 311. When the amount of liquid stored in the concentrated liquid tank 4 is small, all of the sand-containing water supplied to the internal space X1 is discharged from the outlet 331 as concentrated liquid. As the concentrated liquid discharged from the outlet 331 is stored in the tank of the concentrated liquid 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 liquid, and as the tank water level WL2 rises, the water pressure of the concentrated liquid applied to the outlet 331 increases. In this modified example, there is no throttle portion 32 shown in FIG. 2(b) and the outlet 331 is sufficiently large relative to the receiving port 341, so that even after the outlet 331 is blocked by the concentrated liquid, all of the sand-containing water supplied to the internal space X1 is discharged from the outlet 331 until the tank water level WL2 reaches a predetermined height. Thereafter, when the tank water level WL2 reaches the overflow port 43, the supernatant of the concentrated liquid flows out from the overflow port 43, but the amount of sand-mixed water supplied by the sand pump 941 is greater than the amount of the supernatant flowing out from the overflow port 43 by gravity, so 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 separated water starts to be sent out 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-mixed water tries to flow out from the inlet 611 to the grit basin 9 due to the siphon principle, so the amount of separated water sent out from the inlet 611 further increases, the rise of the tank water level WL2 stops, and then it drops and stabilizes at a certain position. The tank water level WL2 at this time is shown in Figures 6(a) and 6(b). When the tank water level WL2 is stable, about 1.2 m3/min of supernatant liquid flows out of the overflow port 43.

The solid-liquid separation device 1 of this modified example also has the same effect as the solid-liquid separation device 1 shown in FIG. 1. Furthermore, the amount of concentrated liquid discharged from the discharge port 331 can be suppressed even without the throttle section 32 due to the water pressure at the discharge port 331 generated by the liquid stored in the concentrated liquid tank 4. Since there is no throttle section 32, the pressure loss in the concentration container 3 is almost zero, and the power of the sand lifting pump 941 can be reduced. Furthermore, even when there is no liquid in the liquid supply pipe 6, simply driving the sand lifting pump 941 makes it possible to fill the liquid supply pipe 6 with liquid by causing the tank water level WL2 to reach the height of the pipe upper end 6c, and the siphon principle can be easily generated.

From the above-described embodiments and modified examples, a solid-liquid separation device is provided which includes a concentration container which receives a mixed liquid in which solids have been mixed into a liquid and which discharges from an outlet a concentrated liquid in which the concentration of the solids in the liquid has increased; a concentrated liquid tank which is disposed within the tank and which stores the concentrated liquid obtained in the concentration container; a transport device which has a lower end portion connected to the bottom of the concentrated liquid tank and an upper end portion of the transport path which extends obliquely upward and is disposed above the outlet; and a liquid delivery pipe which has an inlet connected to the concentration container and an outlet disposed outside the concentrated liquid tank and below the inlet, and which collects solids in the concentrated liquid at the lower end portion, and drives the transport device to transport the solids obliquely upward along the transport path, and sends the liquid in the mixed liquid received by the concentration container through the liquid delivery pipe to the outside of the concentrated liquid tank,
the concentration container receives the mixed liquid while the conveying device is stopped, so that the liquid level in the concentrated liquid tank rises above the discharge port and the liquid supply pipe is filled with the mixed liquid,
the liquid delivery pipe delivers the liquid in the concentrated liquid stored in the concentrated liquid tank to the outside of the concentrated liquid tank by utilizing potential energy of the liquid in the concentrated liquid,
The above-mentioned transport device starts operation after the liquid level in the concentrated liquid tank drops as a result of the liquid feed pipe sending the liquid in the mixed liquid to the outside of the concentrated liquid tank, and transports the solids collected in the lower end portion, which is a solid-liquid separation apparatus.

Next, we will explain the second embodiment of the solid-liquid separation device.

Figure 7 is a front view similar to Figure 3(b) of the solid-liquid separation device of the second embodiment.

The solid-liquid separation device 1 shown in FIG. 7 differs from the solid-liquid separation device 1 shown in the previous embodiment mainly in that the concentration container 3 is not provided. This solid-liquid separation device 1 includes a storage tank 40, a conveying device 5, and a liquid supply pipe 6. The storage tank 40 has the same configuration as the concentrated liquid tank 4 in the previous embodiment. However, this storage tank 40 differs from the concentrated liquid tank 4 in the previous embodiment in that it receives and stores sand-mixed water without passing through the concentration container 3 shown in the previous embodiment, and sends the supernatant liquid (corresponding to the separated water in the previous embodiment) from the inlet 611 without passing through the concentration container 3. A sand-pumping pump 941 is connected to one end of the sand-pumping pipe 942, and a supply port 9421 is formed at the other end of the sand-pumping pipe 942. The sand-mixed water sucked by the sand-pumping pump 941 is directly poured into the tank of the storage tank 40 from the supply port 9421. The sand lifting pipe 942 in this second embodiment is inserted into the tank of the storage tank 40 from the opening at the top end of the storage tank 40. However, the sand pipe 942 may be inserted into the tank of the storage tank 40 by penetrating the side wall 401 of the storage tank 40. Note that the sand lifting pump 941 is actually disposed in the sand collection pit 94 shown in FIG. 1, but in FIG. 7 it is shown to the side of the solid-liquid separation device 1 to simplify the drawing.

The liquid supply pipe 6 has an end portion 61 disposed in the tank of the storage tank 40, a horizontal portion extending horizontally, and a vertical portion bent from the horizontal portion and extending downward. An inlet 611 is formed at one end (the tip of the end portion 61). This inlet 611 is disposed in the lower portion of the storage tank 40. A cap-shaped cover member 612 that spreads around the inlet 611 in a plan view is attached to the end portion 61 slightly above the inlet 611. This cover member 612 prevents sand contained in the sand-mixed water poured into the tank of the storage tank 40 from being sucked into the inlet 611 while it is sinking in the sand-mixed water stored in the tank of the storage tank 40. The peripheral portion of the cover member 612 may be disposed below the inlet 611. Furthermore, the cover member 612 may be disk-shaped. When using a disk-shaped cover member 612, the cover member 612 may be at the same height as the inlet 611. That is, the cover member 612 may be provided above the inlet 611 or around the inlet 611. In other words, the cover member 612 may be provided between the supply port 9421 and the inlet 611. If a disk-shaped cover member that spreads horizontally is used as the cover member 612, sand will accumulate on the cover member 612, so it is preferable to use a cap-shaped cover member. An outlet 62 is formed at the lower end of the vertical part of the liquid supply pipe 6. This outlet 62 is located below the inlet 611 and above the grit basin 9 (see FIG. 1) outside the storage tank 40.

The operation of the solid-liquid separation device 1 of the second embodiment is similar to that of the solid-liquid separation device 1 of the previous embodiment, but the behavior of sand-mixed water is different. Below, the differences from the previous embodiment will be mainly explained using Figures 7 and 8.

Figure 8 is a flowchart showing the operation of the solid-liquid separation device shown in Figure 7.

In the solid-liquid separation operation, first, the sand pump 941 is started to be driven with the conveying device 5 stopped, and the sand-mixed water is received in the storage tank 40 (step S11). The conveying device 5 does not have to be completely stopped, and may be driven at a slow speed at which the liquid components contained in the sand-mixed water do not reach the drop section 52 by the driving of the conveying device 5. That is, the conveying device 5 may be driven at a driving speed slower than a predetermined driving speed. After that, the water level WL3 formed by the sand-mixed water stored in the storage tank 40 gradually rises. This water level WL3 corresponds to an example of a liquid level. The sand contained in the sand-mixed water stored in the storage tank 40 sinks toward the bottom of the storage tank 40 due to its own weight and gathers at the lower end of the conveying path of the conveying device 5. When the water level WL3 rises above the lower end of the horizontal part of the liquid supply pipe 6, the supernatant liquid (sewage) of the sand-mixed water begins to flow out of the outlet 62 through the liquid supply pipe 6. This supernatant liquid also corresponds to an example of liquid. When the water level WL3 rises and reaches the height of the upper end 6c of the liquid supply pipe 6, the liquid supply pipe 6 is filled with the supernatant liquid of the sand-mixed water, and the effect of the siphon principle occurs, increasing the amount of the supernatant liquid that flows out. In other words, the potential energy of the liquid in the sand-mixed water causes the supernatant liquid of the sand-mixed water to be sent out of the storage tank 40 through the liquid supply pipe 6. Due to this effect, a force that sucks in the sand-mixed water is generated near the inlet 611, but the sand that settles near the inlet 611 slides down on the cover member 612 and falls from the edge of the cover member 612, so that it is moved away from the inlet 611. This prevents the sand that settles near the inlet 611 from entering the inlet 611. When the water level WL3 rises further and reaches the overflow port 43, the supernatant of the sand-mixed water flows out of the overflow port 43 together with the liquid supply pipe 6, preventing the water level WL3 from rising any further. The operation of the sand pump 941 continues from the start of operation until a fourth predetermined time has elapsed (step S12). Steps S11 and S12 described above correspond to an example of a receiving process. This fourth predetermined time is a sufficient time to raise the water level WL3 above the top end of the liquid supply pipe 6. A water level sensor that detects that the water level WL3 has risen above the top end of the liquid supply pipe 6 may be provided in the storage tank 40, and a water detection sensor that detects that the liquid supply pipe 6 is filled with the supernatant may be provided in the liquid supply pipe. Instead of determining whether the fourth predetermined time has elapsed, it may be determined whether detection by these sensors has occurred.

After the fourth predetermined time has elapsed, the operation of the sand lifting pump 941 is stopped (step S13). Even after the operation of the sand lifting pump 941 is stopped, the sand-mixed water still acts to flow out through the liquid supply pipe 6 to the sand settling basin 9 due to the effect of the siphon principle described above. As a result, the supernatant of the sand-mixed water flows out through the liquid supply pipe 6 to the sand settling basin 9, and the water level WL3 drops. In other words, the water level WL3 is lowered by sending the supernatant of the sand-mixed water stored in the storage tank 40 to the outside of the storage tank 40 through the liquid supply pipe 6 using the potential energy of the supernatant. When the water level WL3 drops to the inlet 611, air enters the liquid supply pipe 6 from the inlet 611, and the effect of the siphon principle ends. The state immediately after the sand lifting pump 941 is stopped is maintained until the fifth predetermined time has elapsed after the operation of the sand lifting pump 941 is stopped (step S14). The above-described steps S13 and S14 correspond to an example of the liquid transfer process. This fifth predetermined time is the time for the water surface WL3 to fall to the vicinity of the inlet 611. This fifth predetermined time may be shorter than the time for the water surface WL3 to fall to the vicinity of the inlet 611, as long as it is the time for the water surface WL3 to fall to a position lower than the height of the upper end part of the transport path of the transport device 5. Also, instead of determining whether the fifth predetermined time has elapsed, a water level sensor that detects that the water surface WL3 has fallen to a position lower than the height of the upper end part of the transport path of the transport device 5 may be provided in the storage tank 40, and it may be determined whether the detection has occurred. Furthermore, in steps S13 and S14, a small amount of sand-mixed water may be supplied to the storage tank 40 without completely stopping the drive of the sand lifting pump 941, as long as the amount is such that the water surface WL3 falls. Hereinafter, steps S15 to S17 are the same as steps S5 to S7 in the previous embodiment, and therefore will not be described.

This method of driving the solid-liquid separation device also uses the siphon principle to lower the water level WL3 in the storage tank 40 before driving the conveying device 5, making it possible to reduce the height of the conveying path and reduce the size of the solid-liquid separation device 1.

Figure 9 is a front view similar to Figure 7, showing a modified example of the solid-liquid separation device shown in Figure 7.

As shown in FIG. 9, the solid-liquid separation device 1 of this modification is different from the solid-liquid separation device 1 shown in FIG. 7 in the configuration of the liquid supply pipe 6 and the cover member 612. The liquid supply pipe 6 is composed of a horizontal part that extends horizontally and a vertical part that bends from the horizontal part and extends downward. In this modification, the opening at the end of the horizontal part of the liquid supply pipe 6 opposite the side connected to the vertical part becomes the inlet 611. The cover member 612 is attached to the inner surface of the side wall 401 of the storage tank 40 and protrudes toward the inside of the storage tank 40 parallel to the liquid supply pipe 6. As shown in the E arrow view of FIG. 9, the cover member 612 is composed of a plate material with a V-shaped cross section that covers the upper part of the inlet 611. The cover member 612 prevents sand that settles near the inlet 611 from entering the inlet 611. Even in this modified example, during the period from midway through step S12 described above until the water surface WL3 drops to the inlet 611 after step S14, the potential energy (weight) of the liquid in the sand-containing water causes the supernatant liquid of the sand-containing water to be sent out of the storage tank 40 through the liquid delivery pipe 6.

From the second embodiment and its modified example described above, a solid-liquid separation device is provided which includes a storage tank for storing a mixed liquid in which solids are mixed into a liquid, a liquid transfer pipe having an inlet arranged within the storage tank and an outlet arranged outside the storage tank and below the inlet, and a transport device having a lower end portion of a transport path extending obliquely upward and connected to the bottom of the storage tank and an upper end portion of the transport path arranged above the inlet, and which collects solids in the mixed liquid at the lower end portion, transports the solids obliquely upward along the transport path by driving the transport device, and sends the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid transfer pipe,
the storage tank receives the mixed liquid in a state in which the transport device is substantially stopped, thereby receiving the mixed liquid up to a level above an uppermost end of the liquid sending tube;
the liquid supply pipe supplies the mixed liquid received in the storage tank up to a level above the uppermost end of the liquid supply pipe to the outside of the storage tank by utilizing potential energy of liquid in the mixed liquid,
The above-mentioned conveying device starts operating after the liquid level in the storage tank drops as a result of the liquid supply pipe sending the liquid in the mixed liquid to the outside of the storage tank, and conveys the solids collected in the lower end portion, which is a solid-liquid separation device.

In this solid-liquid separation apparatus, a supply port for supplying the mixed liquid to the storage tank is provided above the inlet,
The storage tank may have a cover member disposed between the supply port and the inlet.

The cover member may be provided above the inlet or around the inlet to prevent solids in the mixed liquid supplied from the supply port from entering the inlet during settling.

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

The above-described embodiments and variations can provide a method for driving a solid-liquid separation device that can reduce the size of the solid-liquid separation device.

Note that even if a component is included only in the description of each of the embodiments and variations described above, that component may be applied to other embodiments and variations.

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 concentrated liquid tank to a position considerably above the concentrated liquid tank. The conveying device conveys the sand while draining water in the portion of the conveying path that is located above the water level in the concentrated liquid tank. By increasing the distance the conveying device conveys while draining water, it is possible to prevent wastewater in the concentrated liquid stored in the concentrated liquid tank from being sent outside the concentrated liquid tank together with the sand. However, increasing the distance the conveying device conveys while draining water also increases the conveying path, resulting in a problem of an increased size of the solid-liquid separation apparatus.

The above-described method for driving a solid-liquid separation device includes a concentration container that receives a mixed liquid in which solids are mixed into a liquid and discharges from an outlet a concentrated liquid in which the concentration of solids in the liquid is increased, a concentrated liquid tank having the outlet disposed within a tank and storing the concentrated liquid obtained in the concentration container, a transport device having a transport path extending obliquely upward at a lower end portion connected to a bottom of the concentrated liquid tank and an upper end portion of the transport path disposed above the outlet, and a liquid feed pipe having an inlet connected to the concentration container and an outlet disposed outside the concentrated liquid tank and below the inlet, the method comprising the steps of: collecting solids in the concentrated liquid at the lower end portion; driving the transport device at a predetermined drive speed to transport the solids obliquely upward along the transport path; and sending the liquid in the mixed liquid received by the concentration container to the outside of the concentrated liquid tank through the liquid feed pipe,
a filling step of raising the liquid level of the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container while driving or stopping the conveying device at a driving speed slower than the predetermined driving speed;
a liquid sending step of sending the liquid in the concentrated liquid stored in the concentrated liquid tank to the outside of the concentrated liquid tank through the liquid sending pipe by utilizing potential energy of the liquid in the concentrated liquid, thereby lowering the liquid level in the concentrated liquid tank to a position lower than the height of the upper end portion;
and a transport step of driving the transport device at the predetermined drive speed after lowering the liquid level in the concentrated liquid tank by the liquid sending step, and transporting the solids collected in the lower end portion while draining them at the upper end portion.

a liquid conveying pipe having an inlet connected to the concentration container and an outlet outside the concentrated liquid tank and below the inlet, the liquid being mixed with a solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and the liquid being mixed with the solid, and
a filling step of raising the liquid level of the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container while the conveying device is stopped or driven at a drive speed slower than the predetermined drive speed;
a liquid sending step of sending the liquid in the concentrated liquid stored in the concentrated liquid tank to the outside of the concentrated liquid tank through the liquid sending pipe by utilizing potential energy of the liquid in the concentrated liquid, thereby lowering the liquid level in the concentrated liquid tank;
The method may further include a transporting step of driving the transport device at the predetermined driving speed after lowering the liquid level in the concentrated liquid tank by the liquid sending step, and transporting the solids collected in the lower end portion.

According to this method for driving a solid-liquid separation device, the conveying device is driven after the liquid level in the concentrated liquid tank is lowered, so the conveying path in the conveying device can be shortened. As a result, the solid-liquid separation device can be made smaller. In addition, in the liquid transfer process, the potential energy of the liquid in the concentrated liquid is used to transfer the liquid to the outside of the concentrated liquid tank, so the liquid level in the concentrated liquid tank can be lowered without providing a device such as a pump in the solid-liquid separation device.

In the method for driving the solid-liquid separator, the filling step may be a step of receiving the mixed liquid from a tangential direction of the inner circumferential surface of the cylindrical portion of the concentration container, the cylindrical portion having a cylindrical inner circumferential surface, and discharging the concentrated liquid from the discharge port.

In this way, a swirling flow can be generated within the cylindrical portion. The solids contained in the mixed liquid move downward while being pressed against the inner circumferential surface by the centrifugal force generated by the swirling flow. Meanwhile, the liquid in the mixed liquid collects in the radial center of the cylindrical portion, improving the separation performance of the solids and the liquid. Here, the filling process may include a delivery process of delivering the liquid in the mixed liquid from the inlet located in the radial center of the cylindrical portion.

In addition, in the method for driving the solid-liquid separator, the filling step may be a step of using a concentration container having a constriction portion between the cylindrical portion and the discharge outlet, in which the cross-sectional area of the internal space of the concentration container is smaller on the discharge outlet side than on the cylindrical portion side.

By using a device having the constriction portion, the amount of concentrated liquid discharged from the outlet can be reduced and the amount of liquid sent out from the inlet can be increased. Here, the filling process may include a sending process of sending out the liquid in the mixed liquid from the inlet located at the radial center of the constriction portion.

The above-described method for driving a solid-liquid separation device includes a storage tank for storing a mixed liquid in which solids are mixed into a liquid, a liquid transfer pipe having an inlet arranged within the storage tank and an outlet arranged outside the storage tank and below the inlet, and a transport device having a transport path extending obliquely upward and having a lower end portion connected to a bottom of the storage tank and an upper end portion of the transport path arranged above the inlet, the method comprising the steps of: collecting solids in the mixed liquid at the lower end portion; transporting the solids obliquely upward along the transport path by driving the transport device at a predetermined drive speed; and sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid transfer pipe,
a receiving step of receiving the mixed liquid into the storage tank while the transport device is stopped or driven at a drive speed slower than the predetermined drive speed, thereby raising the liquid level of the storage tank above the uppermost end of the liquid delivery pipe;
a liquid sending step of sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid sending pipe by utilizing potential energy of the liquid in the mixed liquid, thereby lowering the liquid level in the storage tank to a position lower than the height of the upper end portion;
The method is characterized by having a transport process in which, after the liquid level in the storage tank is lowered by the liquid delivery process, the transport device is driven at the specified drive speed and the solids collected in the lower end portion are transported while being drained at the upper end portion.

Also, there is provided a method for driving a solid-liquid separation device comprising: a storage tank for storing a mixed liquid in which solids are mixed into a liquid; a liquid transfer pipe having an inlet disposed within the storage tank and an outlet disposed outside the storage tank and below the inlet; and a transport device having a transport path extending obliquely upward, a lower end portion of which is connected to the bottom of the storage tank and an upper end portion of which is disposed above the inlet, the method comprising the steps of: collecting solids in the mixed liquid at the lower end portion; transporting the solids obliquely upward along the transport path by driving the transport device at a predetermined drive speed; and sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid transfer pipe,
a receiving step of receiving the mixed liquid into the storage tank while the transport device is stopped or driven at a drive speed slower than the predetermined drive speed, thereby raising the liquid level of the storage tank above the uppermost end of the liquid delivery pipe;
a liquid sending step of sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid sending pipe by utilizing potential energy of the liquid in the mixed liquid, thereby lowering the liquid level in the storage tank;
The method may further include a transporting step of driving the transport device at the predetermined drive speed after lowering the liquid level in the storage tank by the liquid sending step, and transporting the solids collected in the lower end portion.

This method of driving the solid-liquid separation device also allows the transport device to be driven after lowering the liquid level in the concentrated liquid tank, so the transport path in the transport device can be shortened. As a result, the solid-liquid separation device can be made more compact. In addition, in the liquid transport process, the potential energy of the liquid in the concentrated liquid is used to transport the liquid, so the liquid level in the concentrated liquid tank can be lowered without providing a device such as a pump in the solid-liquid separation device.

In addition, in the method for driving the solid-liquid separator, the receiving step may be performed in a state in which a cover member provided above the inlet or around the inlet prevents the solids settling from above the cover member from entering the inlet.

The ingress of solids through the inlet is suppressed, improving solid-liquid separation performance.

As a result of the above, it is possible to provide a method for driving a solid-liquid separation device that can realize miniaturization of the solid-liquid separation device.

Reference Signs List 1 Solid-liquid separation device 2 Sand lifting pump 3 Concentration vessel 4 Concentrated liquid tank 5 Conveyor device 6 Liquid delivery pipe 40 Storage tank 62 Outlet 331 Discharge port 611 Inlet

Claims (1)

a concentrated liquid tank having the outlet disposed within the tank and storing the concentrated liquid obtained in the concentrated liquid; a conveying device having a conveying path extending obliquely upward at a lower end portion connected to a bottom of the concentrated liquid tank, an upper end portion of the conveying path being disposed above the outlet and having a dropping section extending downward from near the upper end of the conveying path; and a liquid delivery pipe having an inlet connected to the concentrated liquid tank and an outlet disposed outside the concentrated liquid tank and below the inlet, the method comprising the steps of: collecting solids in the concentrated liquid at the lower end portion; driving the conveying device to convey the solids obliquely upward along the conveying path; and sending the liquid in the mixed liquid received by the concentrated liquid tank through the liquid delivery pipe to the outside of the concentrated liquid tank,
a filling step of raising the liquid level in the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container;
a driving step of driving the conveying device at a speed at which a liquid component contained in the concentrated liquid does not reach the dropping portion, and conveying the solids collected in the lower end portion,
The method for driving a solid-liquid separator, wherein the filling step and the driving step are performed simultaneously.

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