Solid-liquid separation device

Abstract

To provide a solid-liquid separation apparatus that can perform solid-liquid separation by optimizing the chemical injection conditions of the coagulant. [Solution] The solid-liquid separation apparatus of the present invention comprises: a chemical injection device for adding a coagulant to a processing liquid containing solids; a separation device for separating the processing liquid into solid and liquid components; a monitoring device for acquiring image data of the separated liquid discharged from the separation device; an analysis unit for analyzing the image data to acquire information about foam in the separated liquid; and a determination unit for determining whether or not to execute control to change the chemical injection conditions based on the information about foam in the separated liquid, based on the separation performance value and / or control factor value of the separation device.

Description

Technical Field

[0001] The present invention relates to a solid-liquid separation apparatus that performs solid-liquid separation on a treatment liquid containing solid components.

Background Art

[0002] As an apparatus for performing solid-liquid separation on a treatment liquid containing solid components, a centrifugal separator called a decanter is known. The decanter is installed, for example, in a sewage treatment facility, and performs solid-liquid separation on a sewage-derived treatment liquid containing sludge into dehydrated cake and separated liquid. Figure 10 schematically shows the basic structure of the decanter. The horizontal decanter 1 includes a bowl 11 and a screw conveyor 12 that rotate around a horizontal axis. Although not illustrated, a vertical decanter in which the bowl 11 and the screw conveyor 12 rotate around a vertical axis is also known.

[0003] The bowl 11 is configured as a cylindrical body with one end side or both end sides formed in a conical shape. The screw conveyor 12 is provided with screw blades 12a that convey the solid components that have undergone solid-liquid separation inside the bowl 11. The screw conveyor 12 is hollow along the central axis of rotation, and a supply nozzle 13 for the treatment liquid to be centrifugally separated is inserted with a slight clearance so as not to come into contact with the screw conveyor 12. The treatment liquid to be centrifugally separated is supplied to the decanter 1 via the supply nozzle 13 after a flocculant is added. The treatment liquid discharged from the tip of the supply nozzle 13 is supplied to the treatment liquid chamber inside the screw conveyor 12, is discharged from the supply port 14 formed on the outer peripheral surface by the action of centrifugal force, and is supplied into the bowl 11.

[0004] In this configuration, treated wastewater from a sedimentation tank or the like within a wastewater treatment facility is continuously supplied into the bowl 11. When the bowl 11 is rotated at a predetermined speed, the treated wastewater is separated into a solid phase and a liquid phase within the bowl 11 by centrifugal force. The solids are transported by the screw conveyor 12 toward one end of the bowl 11, where they separate from the liquid in the conical portion and are discharged as a dewatered cake through the solids outlet 15. The liquid phase (separated liquid), on the other hand, overflows and is discharged from the separated liquid outlet 16 on the opposite side.

[0005] The control factors for obtaining a dewatered cake with the desired moisture content in the decanter 1 described above include the centrifugal force set by the rotation speed of the bowl 11, the differential speed between the bowl 11 and the screw conveyor 12, the torque value of the screw conveyor 12, and the amount of coagulant added. In recent years, the development of control technologies using artificial intelligence (AI) to adjust these control factors to appropriate values ​​has progressed. Therefore, there is a need to establish a method for optimizing the chemical injection conditions of the coagulant, for example, by using a computer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-83261 [Patent Document 2] Japanese Patent Publication No. 2019-162601 [Patent Document 3] Japanese Patent Application Publication No. 5-177153 [Patent Document 4] Japanese Patent Application Publication No. 63-45000 [Patent Document 5] Japanese Patent Publication No. 2020-195949 [Patent Document 6] Japanese Patent Publication No. 2022-21243 [Patent Document 7] Japanese Patent Publication No. 2020-25943 [Patent Document 8] Japanese Patent Publication No. 2022-21245 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention was made based on these circumstances, and its purpose is to provide a solid-liquid separation device that can perform solid-liquid separation by appropriately controlling the chemical injection conditions of the coagulant. [Means for solving the problem]

[0008] The gist of this invention is as follows: (1) The solid-liquid separation apparatus of the present invention is characterized by comprising: a chemical injection device for adding a coagulant to a processing liquid containing solids; a separation device for separating the processing liquid into solid and liquid components; a monitoring device for acquiring image data of the separated liquid discharged from the separation device; an analysis unit for analyzing the image data and acquiring information about foam in the separated liquid; and a determination unit for determining whether or not to perform control to change the chemical injection conditions based on the information about foam in the separated liquid, based on the separation performance value and / or control factor value of the separation device. (2) The determination unit maintains the current chemical injection conditions if the foam state of the separated liquid is within the appropriate range, continues the current chemical injection conditions if the separation performance value and / or control factor value of the separation device meet predetermined conditions even if the foam state of the separated liquid is not within the appropriate range, and executes control to change the chemical injection conditions based on the foam state of the separated liquid if the foam state of the separated liquid is not within the appropriate range and the separation performance value and / or control factor value of the separation device also do not meet predetermined conditions. (3) The control factor of the separation device is a control factor whose value fluctuates depending on the water content of the separated solids. (4) The determination unit determines the modified chemical injection conditions based on chemical injection conditions parameterized in correspondence with at least the amount of foam in the separated liquid, or chemical injection conditions parameterized in correspondence with at least the amount of foam in the separated liquid and the concentration of solids remaining in the separated liquid. (5) The analysis unit that acquires information regarding the bubbles in the separated liquid is a computer with AI capabilities. (6) The separation device is a decanter comprising a bowl and a screw conveyor, and the control factor of the separation device is one or more of the following: the torque value of the screw conveyor, the load value of the drive motor for the bowl, and the load value of the differential that controls the differential speed between the bowl and the screw conveyor. [Effects of the Invention]

[0009] According to the present invention, the chemical injection conditions for the coagulant can be appropriately controlled by deciding whether or not to perform control that changes the chemical injection conditions based on information about bubbles in the separated liquid, based on the separation performance value and / or the control factor value of the separation device. In other words, while control that changes the chemical injection conditions based on information about bubbles in the separated liquid is useful, if this control is performed at all times, it may in some cases change the chemical injection conditions in an inappropriate direction. The present invention prevents the chemical injection conditions from being changed in an inappropriate direction by suspending the change in chemical injection conditions depending on the separation performance value and / or the control factor value of the separation device. As a result, it is possible to ensure that solid-liquid separation is performed with appropriate chemical injection conditions for the coagulant.

[0010] Therefore, the present invention can contribute to the realization of automatic control of solid-liquid separation equipment using artificial intelligence (AI), which has been under development in recent years. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the configuration of a sewage treatment facility with a decanter arranged according to the first embodiment. [Figure 2] This is a cross-sectional diagram of the decanter shown above. [Figure 3] This is a diagram showing the configuration of the monitoring device for the separated liquid discharged from the decanter mentioned above. [Figure 4] This image shows the separated liquid being released into the liquid receiving box and flowing downwards. [Figure 5] This is a cross-sectional view of the channel for discharging the separated liquid into the liquid receiving box and its end. [Figure 6]This is a diagram obtained by imaging the separated liquid flowing in the flow path through a sight glass. [Figure 7] This is a control flow of chemical injection conditions based on the amount of foam in the separated liquid. [Figure 8] This is a matrix diagram of set values of chemical injection conditions associated with the amount of foam in the separated liquid. [Figure 9] This is a matrix diagram of set values of chemical injection conditions associated with the amount of foam in the separated liquid and the solid matter concentration. [Figure 10] This is a diagram showing the configuration of a conventional centrifugal separator. DETAILED DESCRIPTION OF EMBODIMENTS

[0012] Hereinafter, a solid-liquid separation apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the technical scope of the present invention is not limited in any way by the embodiments described below.

[0013] (First Embodiment) FIG. 1 is a schematic configuration diagram of a sewage treatment facility 3 in which a decanter 2, which is a preferred example of a solid-liquid separation apparatus, is arranged. The sewage treatment facility 3 is roughly divided into a water treatment facility and a sludge treatment facility. The water treatment facility is constituted by equipment such as a primary sedimentation tank 31, an aeration tank, and a final sedimentation tank. The aeration tank, the final sedimentation tank and the like are illustrated as "downstream process" for convenience of drawing. Sewage collected from sewage collection target areas of each municipality and the like is supplied to the primary sedimentation tank 31 to be subjected to solid-liquid separation into a supernatant liquid and primary settled sludge. The supernatant liquid is transferred to the aeration tank, and the primary settled sludge is sent to the sludge treatment facility. The supernatant liquid from the primary sedimentation tank 31 supplied to the aeration tank is biologically treated by activated sludge in the aeration tank. A part of the generated activated sludge is supplied to the final sedimentation tank to be subjected to solid-liquid separation into a supernatant liquid and settled sludge. The supernatant liquid is further rendered harmless and then discharged, a part of the settled sludge is returned to the aeration tank, and the rest is sent to the sludge treatment facility as excess sludge.

[0014] A sludge treatment facility is a facility that processes the sludge generated in the aforementioned water treatment facility, and consists of a thickening unit, a digestion unit, a dewatering unit, etc. Figure 1 shows an example of a separation and thickening system. In this case, the primary sludge from the primary sedimentation tank 31 is gravity-thickened in a gravity-type thickening tank 32, and the excess sludge from the final sedimentation tank is mechanically thickened in a mechanical thickener 33. The mechanical thickener 33 is a belt-type filtration thickener, and a decanter-type centrifugal thickener may also be used. The sludge (thickened sludge) thickened in the gravity-type thickening tank 32 and the mechanical thickener 33 is supplied from the thickened sludge tank 34 to the decanter 2, which acts as a dewatering unit, via a supply pump 35, or is supplied to the decanter 2 after digestion.

[0015] Decanter 2 separates the sludge (concentrated sludge), which is the processing liquid, into a dewatered cake and a separated liquid. The dewatered cake discharged from Decanter 2 is then supplied to the incinerator 37 via transfer equipment 36, such as a pressure pump and a conveyor belt, for incineration. Other treatments may also be performed. Meanwhile, the separated liquid discharged from Decanter 2 is collected in the separated liquid recovery tank 38 via the separated liquid monitoring device 4, which will be described in more detail later. The separated liquid, which is a clarified liquid, is treated to render it harmless if necessary, and then discharged.

[0016] The operation of each piece of equipment in the sewage treatment plant 3 is centrally managed, for example, by a computer in the central control room 39. Operators can communicate with the central control room 39 using, for example, a terminal 30. However, the overall configuration of the sewage treatment plant 3 shown in Figure 1 is just one example, and the equipment configuration and treatment method are not limited.

[0017] As shown in Figure 2, the decanter 2 comprises a casing 2a having a solids outlet 20 and a separated liquid outlet 21 on its lower side, a bowl 5 placed inside the casing 2a, a screw conveyor 6 that transports the solids centrifuged in the rotating bowl 5, and a pipe-shaped feed tube 7 that supplies the centrifuged liquid into the bowl 5. The bowl 5 is supported on both shafts by a bearing mechanism 22, such as a bearing located outside the casing 2a. Furthermore, the screw conveyor 6 is supported on both shafts by a bearing mechanism 23, such as a conveyor bearing. Reference numeral 24 denotes a partition wall that divides the space inside the casing 2a.

[0018] Then, when the power from the drive motor 25, which is the drive device, is transmitted to the pulley 25b on the bowl 5 side via the rotating belt 25a, the bowl 5 rotates, and rotational power is further transmitted to the screw conveyor 6 via the gearbox 26 and spline shaft 26a, which are differential speed generating devices, causing the bowl 5 and the screw conveyor 6 to rotate with a relative differential speed. The speed can be adjusted as appropriate depending on the type and concentration of the processing liquid, but as an example of normal operation, it is 500 to 8000 min⁻¹. -1 The bowl 5 is rotated at a predetermined number of rotations selected within the range, and the bowl 5 is subjected to a process of 0.5 to 50 min. -1 By rotating the screw conveyor 6 with a relative difference in speed, the treated liquid is centrifuged into solids and separated liquid. For example, when sludge derived from sewage is used as the treated liquid, for example, 2 to 25 m 3 Supply into bowl 5 at a flow rate of / hr.

[0019] The gearbox 26 is connected to a motor called a back drive motor 27, which is an example of a differential motor, via a rotating belt 27a and a pulley 27b. The back drive motor 27 is used to brake the screw conveyor 6 so that it rotates slower than the bowl 5. The regenerative power generated in the back drive motor 27 by braking can be supplied to the main motor 25. However, the back drive motor 27 is not necessarily required. Reference numeral 28 denotes the support frame for the decanter 2, and reference numeral 29 denotes a support member that supports the feed tube 7.

[0020] Bowl 5 has a cylindrical body with a conical section 51 at one end and a disc-shaped member called a front hub 52 at the other end. The body of bowl 5 forms a pool (liquid reservoir) for the processing liquid supplied into bowl 5. On the other hand, the conical section 51 forms a beach section through which solids conveyed by the screw conveyor 6 separate from the liquid phase, and a solids discharge port 53 is provided at its end. The front hub 52 is provided with a separation liquid discharge port 54 through which the separation liquid overflows and is discharged. The separation liquid discharge port 54 is, for example, a circular opening that penetrates the front hub 52.

[0021] The outer surface of the screw conveyor 6 is provided with screw blades 61 arranged in a spiral pattern for conveying solid matter. Furthermore, a processing liquid supply port 62 is provided on the outer surface of the screw conveyor 6. The processing liquid supply port 62 is in communication with a processing liquid supply chamber 63 formed inside the screw conveyor 6.

[0022] The feed tube 7 is positioned so as not to come into contact with the rotating bowl 5 and screw conveyor 6, and is positioned close to or inserted into the processing liquid supply chamber 63. At the inlet of the processing liquid supply chamber 63, a vertical wall 64 is formed along the circumferential direction, serving as a liquid containment barrier to prevent the supplied processing liquid from flowing back out. On the other hand, the base end of the feed tube 7 is connected to the supply pump 35 (see Figure 1) via a flow path 71. The processing liquid sent from the supply pump 35 is discharged into the processing liquid supply chamber 63 from the tip of the feed tube 7. The processing liquid supplied into the processing liquid supply chamber 63 is discharged from the processing liquid supply port 62 and supplied into the bowl 5 by the centrifugal force of the rotating screw conveyor 6.

[0023] Next, the chemical injection device 8 for adding a coagulant to the treatment liquid will be described. The decanter 2 of this embodiment is configured to allow the coagulant to be added by either external or internal chemical injection. As a preferred example of external chemical injection, line injection is used. Specifically, chemical injection nozzles 80A, 80B, and 80C are placed in the middle of the treatment liquid flow path 71 (for example, piping). Multiple chemical injection nozzles 80A, 80B, and 80C are provided so that the coagulation reaction time (i.e., the time until the treatment liquid with the added coagulant is supplied to the decanter 2) can be varied.

[0024] Figure 2 shows three chemical injection nozzles 80A, 80B, and 80C, but the number of nozzles may be changed as appropriate. The nozzles from which the coagulant is added are switched by opening and closing valves 81A, 81B, and 81C. However, it is not necessary to use just one of them; two or more of the nozzles 80A, 80B, and 80C may be used. In this case, the ratio of the added amounts may be adjusted by adjusting the valve opening. The opening and closing or adjustment of the opening of valves 81A, 81B, and 81C may be performed automatically by the control unit 9 of the decanter 2, or manually by the operator.

[0025] The distance from Decanter 2 to the addition position of the chemical injection nozzle 80A (i.e., the length of the flow path 71) is, for example, 10 m. The distance from Decanter 2 to the addition position of the chemical injection nozzle 80B (i.e., the length of the flow path 71) is, for example, 3 to 5 m. The distance from Decanter 2 to the addition position of the chemical injection nozzle 80C (i.e., the length of the flow path 71) is, for example, 1 m. The coagulation reaction time is determined by the respective distances and the flow velocity of the treatment liquid (= flow velocity × distance). In other words, the chemical injection nozzles 80A, 80B, 80C and valves 81A, 81B, 81C are examples of means for adjusting the addition position of the coagulant. Means to enhance the stirring effect, such as a line mixer or mixing valve, may be provided downstream of the coagulant addition position.

[0026] On the other hand, in-machine chemical injection is performed using a feed tube 7 as an example. The feed tube 7 has a double-tube structure with a central channel 72 through which the treatment liquid flows and a channel 73 surrounding its outer circumference through which the coagulant flows. A coagulant channel 82 (for example, piping) is connected to the channel 73, and a valve 81D is provided in the channel 82. Therefore, by opening and closing valves 81A, 81B, 81C, and 81D, it is possible to switch between in-machine and external chemical injection. By adjusting the valve opening, the coagulant may be added using both in-machine and external injection.

[0027] At the tip of the feed tube 7, a coagulant discharge port is formed separately from the central processing liquid discharge port. The coagulant discharge port is, for example, a circular opening formed radially through the circumferential surface of the tip of the feed tube 7. Meanwhile, the inside of the screw conveyor 6 is divided into a processing liquid supply chamber 63 and a coagulant supply chamber 65 via an upright wall 64 that acts as a partition. The coagulant supply chamber 65 is a supply chamber with a groove-shaped cross-section formed around the entire circumference of the inner circumferential surface of the cavity of the screw conveyor 6, and can receive the coagulant discharged radially from the feed tube 7. Furthermore, a coagulant discharge port 66 is formed at the bottom of the coagulant supply chamber 65. The coagulant discharge port 66 is, for example, a circular opening that radially penetrates the screw conveyor 6. In other words, the coagulant, like the processing liquid, can be supplied into the bowl 5 by utilizing the centrifugal force of the rotating screw conveyor 6.

[0028] A flow meter 83 is provided in the coagulant flow path 82 to measure the flow rate of the coagulant supplied by the coagulant supply pump 84. The flow control unit 85 adjusts the discharge flow rate of the coagulant supply pump 84 so that the flow rate measured by the flow meter 83 becomes the target flow rate, for example, by feedback control. The coagulant supply pump 84 is, for example, a metering pump or a pump with variable output by an inverter. In other words, the flow meter 83 and the coagulant supply pump 84 are just one example of means for adjusting the amount of chemical injected. However, flow rate adjustment using the flow meter 83 and the coagulant supply pump 84 is just one example, and other configurations may be adopted as long as the flow rate can be adjusted. One example of another configuration is to provide a flow rate adjustment valve in the flow path 82.

[0029] The base end of the flocculant channel 82 is connected to a tank 86 storing a flocculant solution via a flocculant supply pump 84. The flocculant is, for example, a polymer flocculant. The polymer flocculant can be an amphoteric polymer, anionic polymer, or cationic polymer, or a combination thereof. Preferred examples of polymer flocculants include one or more of dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, and polyvinyl amidine. The polymer flocculant solution can be produced, for example, by dissolving a solid polymer flocculant in a solvent (e.g., water) to produce a solution. The polymer flocculants for in-machine and external injection may be the same type, or they may be different types supplied from different sources. Additionally, a configuration to add an inorganic flocculant may be added.

[0030] The decanter 2 of this embodiment allows for the selection of various chemical injection conditions, such as the amount of chemical injected, the injection location, and the ratio of external to internal injection. In the following description, the optimization of chemical injection conditions is explained using the change in the amount of chemical injected as an example, but the amount of chemical injected, the injection location, and the ratio of external to internal injection may be changed in combination. Conversely, it is not necessary to have a configuration that allows all of the chemical injected amount, injection location, and the ratio of external to internal injection to be changed. For example, it may only have a configuration that allows the chemical injected amount to be changed. The amount of chemical injected may also be controlled as a ratio to the flow rate of the processing liquid (chemical injection rate).

[0031] As shown in Figure 3, the separated liquid monitoring device 4 is installed in the middle of the flow path 21a (for example, piping) of the separated liquid discharged from the separated liquid outlet 21 of the decanter 2. When multiple decanters 2 are arranged in the sewage treatment facility 3, it is desirable to install a separated liquid monitoring device 4 in each decanter 2, but the separated liquid monitoring device 4 may also be installed where the separated liquids discharged from multiple decanters 2 merge.

[0032] As a preferred example, the separated liquid monitoring device 4 includes a monitoring unit 42 that monitors the state of the separated liquid discharged into a liquid receiving box 41, which is an example of a monitoring box, and a monitoring unit 40 that monitors the state of the separated liquid flowing through the flow path 21a. The flow path 21a branches into a line leading to the monitoring unit 42 and a line leading to the monitoring unit 40, and is provided with valves 45A and 45B. Normally, valves 45A and 45B are kept open.

[0033] The monitoring unit 42 monitors the state of foam in the separated liquid discharged into the liquid receiving box 41. Specifically, the end 21d of the flow path 21a is connected to the box-shaped liquid receiving box 41, allowing the separated liquid to be discharged into the liquid receiving box 41. The monitoring camera 46 preferably images the separated liquid flowing down into the liquid receiving box 41. The image data acquired is analyzed by a computer to obtain information about the foam in the separated liquid. The information about the foam in the separated liquid preferably includes the amount of foam. Alternatively, it may include the color of the foam or the degree of foaming. This is because some types of coagulants can affect the color of the foam or the degree of foaming. The monitoring camera 46 is, for example, a CCD camera. The monitoring camera 46 may be equipped with a flash function, or a separate light source that turns on when imaging is performed may be provided.

[0034] Foam in the separated liquid is caused by residual flocculant. Foam is particularly likely to occur with polymer-based flocculants. It should be noted that residual flocculant can occur not only when an excessive amount is added beyond the appropriate amount, but also when the flocculation reaction is poor, even if the appropriate amount is used. This embodiment achieves control that takes these factors into consideration, as will be described later.

[0035] The amount of foam, which is an example of information regarding foam in the separated liquid, is preferably derived by analyzing the image with a computer equipped with AI capabilities. In other words, the computer equipped with AI capabilities functions as the analysis unit. As explained in the example in Figure 4, first, the region of the flowing separated liquid (hereinafter referred to as the "flowing liquid section 90") is extracted from the acquired image data. In other words, regions other than the flowing liquid section 90 are excluded from the image data. Then, the flowing liquid section 90 is subdivided into minute regions, and it is determined whether or not what is captured in each minute region is foam. Then, the minute regions determined to be foam are totaled, and the area of ​​foam in the entire flowing liquid section 90 is calculated, for example, as a percentage. This is considered to be the amount of foam in the separated liquid. The analysis results, along with the value of the foam area, should preferably be displayed graphically on a monitor or the like so that the operator can confirm them. Figure 4 shows an example in which imaging of the separated liquid flowing into the liquid receiving box 41 is continued, and the area of ​​foam in the flowing liquid section 90 is analyzed by a computer.

[0036] As image data (i.e., video) is continuously transmitted from the surveillance camera 46, the AI-enabled computer performs a continuous analysis of the amount of foam. Similarly, when analyzing the color and degree of foaming, the image data is analyzed to quantify the color and foaming conditions. The AI-enabled computer is installed somewhere within the sewage treatment facility 3, for example. It may also be a computer outside the sewage treatment facility 3 via a communication line, such as a cloud server.

[0037] The cross-sectional shape of the end 21d of the flow path 21a connected to the liquid receiving box 41 is not particularly limited and may be of various shapes, but is preferably a square or circular shape. More preferably a square shape. For example, if the flow rate of the separated liquid changes depending on the amount of sludge treated in the decanter 2, in the case of a circular shape, the measurement range of the bubbles in the fluid section 90 as seen from the monitoring camera 46 will differ depending on the water level and flow rate of the separated liquid. See Figure 4 for the image of the fluid section 90 as seen from the monitoring camera 46. That is, as schematically shown in Figure 5, the width of the measurement range of the bubbles becomes smaller as the flow rate decreases and the water level drops compared to when the water level is around the center of the circle. The same is true when the water level rises. Also, when the water level drops, the thickness of the bubbles in the depth direction of the fluid section 90 may increase, but this change in the thickness of the bubbles in the depth direction may not be captured by subsequent image analysis. In contrast, in the case of a square shape, the measurement range of the bubbles is stable regardless of the water level and flow rate of the separated liquid, and the width is constant, so the thickness of the bubbles is also stable. As a result, it has been confirmed that a rectangular shape is less affected by changes in water level and flow rate, and provides higher accuracy in analyzing the amount of foam. The flow path can be square or rectangular as long as the width is constant, but a wide rectangle is preferable. This is because it reduces the thickness of the foam in the depth direction of the fluid section 90 and allows the foam to spread across the measurement range.

[0038] In addition to the surveillance camera 46 that images the fluid section 90 from the front, a surveillance camera that images the fluid section 90 from the side may be added to enable image analysis of the foam thickness in the depth direction of the fluid section 90. Furthermore, the fluid section 90 used for foam measurement is not necessarily limited to the separated liquid discharged from the end 21d of the flow path 21a. For example, the separated liquid flowing through the flow path 21a may be used as the fluid section 90. The flow path 21a may be inclined. In this case as well, a rectangular cross-sectional shape is preferable for the flow path 21a, as it is less affected by changes in water level. As an example, a flow path 21a in which the area to be imaged by the surveillance camera 46 is formed of a transparent material may be used. A sight glass may also be used, but since foam may accumulate in areas with steps such as joints, it is preferable to form the flow path 21a itself with a transparent tube or the like.

[0039] The value related to foam (preferably the amount of foam) used to control the chemical injection conditions described later may be an instantaneous value, or if the value varies over time, a moving average value may be used to suppress the influence of random errors. The separated liquid released into the liquid receiving box 41 is discharged from the outlet 47 provided on the bottom side of the box and collected in the separated liquid tank 38 or the like (see Figure 1).

[0040] Meanwhile, the monitoring unit 40 monitors the solid content remaining in the separated liquid. Specifically, a sight glass 43 is placed in the flow path, and a monitoring camera 44 is installed opposite the glass window of the sight glass 43. The monitoring camera 44 captures images of the separated liquid flowing through the flow path and acquires image data. The acquired image data is analyzed by a computer to obtain information about the solid content remaining in the separated liquid. The information about the solid content is at least the solid content concentration. In addition to the concentration, particle size, degree of aggregation, or both may also be included. The monitoring camera 44 is, for example, a CCD camera. The monitoring camera 44 may be equipped with a flash function, or a separate light source that turns on when imaging is performed may be provided. Figure 6 is an example of image data of the captured separated liquid.

[0041] The solid content concentration is analyzed using a computer with AI capabilities, as a preferred example. That is, the computer functions as the analysis unit. The computer with AI capabilities analyzes the solid content concentration based on image data. As an example, the analysis of the solid content concentration utilizes image data of the separated liquid associated with the solid content concentration. That is, as shown in an example in Figure 6, the state of the separated liquid as it appears in the image data differs depending on the solid content concentration. Therefore, the computer with AI capabilities analyzes the solid content concentration from the actual image data of the separated liquid, based on the image data of the separated liquid associated with the solid content concentration. Alternatively, as in the foam analysis described above, the acquired micro-regions may be subdivided, and the solid content concentration may be derived by determining whether what is visible in each micro-region is solid content or not. The solid content concentration information is displayed on a monitor screen, for example, so that an operator can confirm it. This computer with AI capabilities is installed somewhere within the sewage treatment facility 3, for example. It may also be a computer outside the sewage treatment facility 3 via a communication line, such as a cloud server.

[0042] As shown in Figure 3, the monitoring unit 40 line includes a diaphragm pump 48, a sight glass 43, a monitoring camera 44, and a back pressure valve 49. The diaphragm pump 48 pumps the separated liquid towards the sight glass 43. The sight glass 43 is positioned vertically so that the separated liquid flows upwards from bottom to top. The back pressure valve 49 is positioned downstream of the sight glass 43. It is preferable to use flexible piping materials or fittings, such as a hose 21b, in the flow path between the valve 45B and the suction port of the diaphragm pump 48, and in the flow path between the discharge port of the diaphragm pump 48 and the sight glass 43. Similarly, it is preferable to use flexible piping materials or fittings, such as a hose 21b, in the flow path between the sight glass 43 and the back pressure valve 49, and in the flow path between the back pressure valve 49 and the liquid receiving box 41.

[0043] The diaphragm pump 48 delivers the separated liquid towards the sight glass 43. That is, it quantitatively samples the separated liquid and sends it to the sight glass 43. The flow rate of the separated liquid flowing through the sight glass 43 is set to, for example, 50 to 500 L / h. The diaphragm pump 48 is a preferred example of a pump for sampling the separated liquid monitored by the monitoring unit 40. However, the use of any positive displacement reciprocating pump other than a diaphragm pump is not restricted. Examples of other pumps include plunger pumps and piston pumps. Positive displacement reciprocating pumps have a structure that makes them prone to generating pulsation in the discharged fluid. Therefore, a back pressure valve 49 is often provided on the discharge side to suppress pulsation.

[0044] In the above configuration, the separated liquid quantitatively flowing through the sight glass 43 is imaged by the surveillance camera 44, and image data of the separated liquid is acquired. This embodiment employs a positive displacement reciprocating pump and places the sight glass 43B between the pump 48 and the back pressure valve 49, thereby making it easier to acquire image data of the solids remaining in the separated liquid by utilizing the action of pulsation. In other words, by applying pulsation to the separated liquid flowing through the sight glass 43, it is possible to acquire image data in which the solids are evenly dispersed in the liquid without breaking the aggregated particles. This makes it possible to improve the accuracy when determining the solid concentration.

[0045] Next, referring to Figure 7, we will explain the sequence of events in which the computer in the control unit 9 controls the drug injection conditions based on the acquired foam information. In other words, the computer functions as a decision unit. This computer is, for example, a programmable logic controller (PLC) (for convenience of explanation, we will refer to it as a control computer).

[0046] The following describes a preferred example of control based on the amount of bubbles. For example, a control computer such as a PLC determines whether the amount of bubbles is within the appropriate range, too little, or too much, based on the bubble area value sent from a computer with AI functionality as an analysis unit. As an example, this determination is made by setting a threshold for the appropriate range of bubble area, and determining that the amount of bubbles is "appropriate" if the bubble area value obtained by image analysis is within the appropriate range, too little if it is below the appropriate range, and too much if it is above the appropriate range. For example, when calculating the bubble area as a percentage, the appropriate range is set to, for example, 54.0% to 57.9% (step S100).

[0047] If the control computer determines that the amount of foam is within the appropriate range (step S101, Yes), it maintains the current operating conditions of Decanter 2 (step S102). That is, as a preferred example, it maintains the set value of centrifugal force, the set value of differential velocity, and the current set value of chemical injection amount. The set value of chemical injection amount is, for example, the output value of the coagulant supply pump 84.

[0048] On the other hand, if the control computer determines that the amount of foam is not within the appropriate range (step S101, No), it then determines whether it is above or below the appropriate range (step S103). If the amount of foam is above the appropriate range (step S103, Excess), it then determines whether the current torque value of the screw conveyor 6 is above or below a threshold (step S104). The threshold is an example of a threshold used to determine whether a predetermined condition is met. If the torque value of the screw conveyor 6 is above the threshold (step S104, Above or Below), the control computer executes a control to reduce the amount of chemical injected (step S105). In other words, the torque value of the screw conveyor 6 is one of the control factors of the decanter 2, which is affected by the moisture content of the separated solid (e.g., dewatered cake). If the torque value is above the set value, it is highly likely that the moisture content of the separated solid meets the desired value. Therefore, it is determined that the amount of chemical injected can be reduced. The amount by which the amount of chemical injection is reduced is determined based on the change in the output of the coagulant supply pump 84, which is associated with the value of the foam area, as shown in Figure 8 as an example. For example, if the value of the foam area is 60%, the output of the coagulant supply pump 84 is set to -3% from the current value. Instead of the output of the coagulant supply pump 84, the flow rate of the coagulant or the chemical injection rate, which are associated with the value of the foam area, may be used for control.

[0049] If the torque value of the screw conveyor 6 is less than the set value (step S104, less than), the current chemical injection conditions are maintained (step S106). The reason for not changing the chemical injection conditions even though the amount of foam is not within the appropriate range is that changing the chemical injection conditions in this state may actually make the operation unstable. In other words, if the torque value is less than the set value, it is highly likely that the water content of the separated solids is high. If the amount of chemical injection is reduced despite this, the water content may increase even further and may not meet the specified water content. For this reason, the change in chemical injection conditions is postponed. This condition may resolve over time, but it may also be due to the chemical injection amount being appropriate but the coagulation reaction not progressing. Therefore, if this condition persists for a long time, the control computer will change the operating conditions of decanter 2, such as changing the differential speed setting. Alternatively, the chemical injection position may be changed, or the flow rate ratio of external and internal chemical injection may be changed. It is desirable that these changes to the operating conditions of decanter 2 be programmed to be performed automatically by the control computer, but the operator may make the decision. A computer with AI capabilities may determine how to modify the operating conditions of Decanter 2 to a desirable degree, and a control computer may then execute the control accordingly. Alternatively, a computer with AI capabilities may perform the control instead of a control computer.

[0050] On the other hand, in step S103, if the amount of foam is below the appropriate range (step S103, less), the system then determines whether the current torque value of the screw conveyor 6 is above or below a threshold (step S107). If the torque value of the screw conveyor 6 is above the threshold (step S107, above), the control computer maintains the current chemical injection conditions (step S108). The reason for not changing the chemical injection conditions even though the amount of foam is not within the appropriate range is that changing the chemical injection conditions in this state may actually make the operation unstable. In other words, if the torque value is above the set value, it is highly likely that the moisture content of the separated solids meets the desired value. If the chemical injection amount is increased despite this, the moisture content will decrease further, the solids separated at the beach of the bowl 5 will stop moving, and in some cases the screw conveyor 6 may overload and stop. For this reason, the change in chemical injection conditions is postponed. This condition may resolve itself over time, but if it persists for a long time, the control computer will change the operating conditions of the decanter 2, such as changing the differential speed setting. Alternatively, the injection location of the chemical agent may be changed, or the flow rate ratio between external and internal chemical injection may be changed. It is desirable that these changes to the operating conditions of Decanter 2 be programmed to be performed automatically by the control computer, but the operator may make the decision. The AI-enabled computer may determine how to best change the operating conditions of Decanter 2, and the control computer may execute the control accordingly, or the AI-enabled computer may perform the control instead of the control computer.

[0051] On the other hand, if the torque value of the screw conveyor 6 is less than the set value (step S107, less than), the control computer executes a control to increase the amount of chemical injected (step S109). In other words, if the torque value is less than the set value, it is highly likely that the water content of the separated solids is high. Therefore, it is determined that the amount of chemical injected can be increased. How much to increase the amount of chemical injected is determined, for example, based on the change in the output of the coagulant supply pump 84 corresponding to the value of the foam area, as shown in Figure 8. For example, if the value of the foam area is 35%, the output of the coagulant supply pump 84 is increased by 4% from the current value. Instead of the output of the coagulant supply pump 84, the flow rate of the coagulant or the chemical injection rate corresponding to the value of the foam area may be used for control. Of course, the control is not limited to the control computer changing the amount of chemical injected in stages. For example, a computer with AI functionality may derive a desirable amount of chemical injected and set it directly.

[0052] According to the above embodiment, by determining whether or not to perform control that changes the amount of chemical injection based on the state of foam in the separated liquid (preferably the amount of foam in the separated liquid) based on the torque value of the screw conveyor 6, the amount of coagulant injected can be appropriately controlled for solid-liquid separation. In other words, as described in detail above, while control that changes the amount of chemical injection according to the amount of foam in the separated liquid is useful, if this control is always performed, it may change the amount of chemical injection in an inappropriate direction. This embodiment prevents the amount of chemical injection from being changed in an inappropriate direction by suspending the change in the amount of chemical injection depending on the torque value of the screw conveyor 6, which is one of the control factors of the decanter 2. By monitoring the foam in the separated liquid in this way and setting appropriate chemical injection conditions, it becomes possible to obtain a dehydrated cake, which is the solid component, with a desirable moisture content (for example, a moisture content of 60-80%).

[0053] For example, the properties of the sewage collected at the sewage treatment plant 3 vary from day to day, and the properties of the sludge, which is the treatment liquid, are not necessarily constant. The control method of this embodiment is superior in that it can respond to changes in the properties of the sludge, which is the treatment liquid. Furthermore, it has been confirmed in actual tests that the same control method can be applied even if the type of coagulant is different, eliminating the need to change the control method for each sewage treatment plant 3.

[0054] The control factor for decanter 2, which determines whether or not to perform control to change the amount of chemical injected based on the amount of foam in the separated liquid, is suitable for the torque value of the screw conveyor, but is not limited to this. Other examples include the load value of the drive motor 25 of bowl 5, or the load value of the differential motor (e.g., back drive motor 27) that controls the differential speed between bowl 5 and screw conveyor 6. Alternatively, a combination of these may also be used. The load value of the drive motor 25 and the load value of the differential motor (e.g., back drive motor 27) are, for example, the motor current values.

[0055] Furthermore, while the control factor value of Decanter 2 was used in the above example, the separation performance value of Decanter 2 may be used instead. Alternatively, the control factor value and the separation performance value may be used in combination or selectively. An example of a separation performance value is the moisture content of the separated solids. The moisture content of the separated solids is measured using, for example, an existing moisture meter that uses infrared or microwaves. Alternatively, the moisture content is derived by imaging the solids discharged from Decanter 2 with a camera and analyzing the image with a computer equipped with AI capabilities.

[0056] Furthermore, Decanter 2 is just one example of a solid-liquid separation device, and the control method of this embodiment can be applied to other solid-liquid separation devices. For example, in the case of a rotary pressure dewatering machine, the outlet pressure, rotational load, etc., can be used as control factors to determine whether or not to execute control that changes the amount of chemical injected. For example, in the case of a screw press, the relationship between the inlet pressure and the processing volume, the presser pressure, etc., can be used as control factors to determine whether or not to execute control that changes the amount of chemical injected. In addition, the water content of the separated solids can be used as a separation performance value.

[0057] (Second Embodiment) Next, we will describe Decanter 2 according to the second embodiment. In the first embodiment, the amount of chemical to be injected is determined by the amount of foam in the separated liquid, but in the second embodiment, the amount of chemical to be injected is determined based on both the amount of foam in the separated liquid and the solid content concentration of the separated liquid.

[0058] The basic control flow is the same as in Figure 7. When the amount of chemical injected is decreased in step 105 of Figure 7, and when the amount of chemical injected is increased in step S109, the amount to change is determined based on the change in the output of the coagulant supply pump 84, which corresponds to both the amount of foam in the separated liquid and the solid content concentration of the separated liquid. Figure 9 shows an example. Figure 8 above shows an example of chemical injection conditions parameterized in relation to the amount of foam in the separated liquid, and Figure 9 shows an example of chemical injection conditions parameterized in relation to both the amount of foam in the separated liquid and the concentration of solids remaining in the separated liquid. These do not preclude the addition of other factors besides the amount of foam and the concentration of solids.

[0059] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those with ordinary skill in the art that various substitutions, modifications, and changes to the form and details can be made without departing from the spirit and scope of the invention as defined by the claims. [Explanation of Symbols]

[0060] 2 Decanters 3. Sewage treatment facilities 4 Separated liquid monitoring device 5 bowls 6. Screw conveyor 8 Chemical dosing device 9. Control Unit

Claims

1. A chemical injection device for adding a coagulant to a processing liquid containing solids, A separation device for separating the processed liquid into solid and liquid, A monitoring device that acquires image data of the separated liquid discharged from the separation device, An analysis unit analyzes the aforementioned image data to obtain information about bubbles in the separated liquid, A solid-liquid separation apparatus comprising: a determination unit that determines whether or not to perform control to change the chemical injection conditions based on information about bubbles in the separated liquid, based on the separation performance value and / or the control factor value of the separation apparatus.

2. The solid-liquid separation apparatus according to claim 1, characterized in that the determination unit maintains the current chemical injection conditions when the foam state of the separated liquid is within an appropriate range, continues the current chemical injection conditions if the separation performance value and / or control factor value of the separation apparatus meet predetermined conditions even if the foam state of the separated liquid is not within an appropriate range, and performs control to change the chemical injection conditions based on the foam state of the separated liquid if the foam state of the separated liquid is not within an appropriate range and the separation performance value and / or control factor value of the separation apparatus also do not meet predetermined conditions.

3. The solid-liquid separation apparatus according to claim 1 or 2, characterized in that the control factor of the separation apparatus is a control factor whose value fluctuates depending on the water content of the separated solids.

4. The solid-liquid separation apparatus according to claim 1 or 2, characterized in that the determination unit determines the modified chemical injection conditions based on chemical injection conditions parameterized in correspondence with at least the amount of foam in the separated liquid, or chemical injection conditions parameterized in correspondence with at least the amount of foam in the separated liquid and the concentration of solids remaining in the separated liquid.

5. The solid-liquid separation apparatus according to claim 1 or 2, characterized in that the analysis unit that acquires information regarding bubbles in the separated liquid is a computer with AI functionality.

6. The separation device is a decanter equipped with a bowl and a screw conveyor. The solid-liquid separation apparatus according to claim 1 or 2, characterized in that the control factor of the separation apparatus is one or more of the torque value of the screw conveyor, the load value of the drive motor of the bowl, and the load value of the differential that controls the differential speed between the bowl and the screw conveyor.

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