Sludge dehydrator

Abstract

To provide a technique capable of improving the efficiency in managing the operation of a sludge dehydrator.SOLUTION: The sludge dehydrator comprises a water-content acquiring unit 110 acquiring the water content in dehydrated sludge, a sludge amount acquiring unit 120 acquiring the current amount of sludge in a sludge storage tank 20, a dehydration controller 130 controlling the action of a screw press dehydrator 60, with the sludge amount acquiring unit 120 further acquiring an estimated amount of sludge, i. e., an estimated value of the amount of sludge, in the sludge storage tank subsequent to the passage of a specified time, and the dehydration controller 130 controlling the action of the screw press dehydrator 60 so that the water content in the dehydrated sludge becomes a set target value and adjusting the rotation rate of a screw 62 so that the estimated amount of the sludge does not exceed the upper limit of the amount of the sludge in the sludge storage tank, in preference to the water content of the dehydrated sludge when the estimated amount of sludge exceeds the upper limit of the amount of sludge in the sludge storage tank.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a sludge dewatering apparatus that dewaters sludge. [Background technology]

[0002] Conventionally, one type of sludge dewatering apparatus that dewaters sludge is known that includes a screw press dewatering machine. In addition, as one type of sludge dewatering apparatus, for example, there is one that estimates the moisture content of dewatered sludge dewatered by the screw press dewatering machine and controls the rotation speed of the screw press dewatering machine based on the estimated moisture content (see Patent Document 1).

[0003] Patent Document 1 describes measuring the moisture content of turbid residue (dewatered sludge) dewatered by a dewatering device main body, which is a screw press dewatering machine, and controlling the operating parameters, including the rotation speed of the screw press dewatering machine, so that the moisture content of the turbid residue falls within a target range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-175217 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, industrial sludge dewatering equipment used in manufacturing plants for food, chemicals, semiconductors, etc., has a smaller capacity than sludge dewatering equipment for water supply and sewerage, and the properties of the sludge tend to change more rapidly. In such cases, the operation and management of the sludge dewatering equipment often relies on manpower and experience, and sufficient efficiency has not been achieved.

[0006] In addition, the operation and management of the sludge dewatering equipment often involves responding to emergencies such as water leakage, etc. Therefore, the majority of the operation and management costs are comprised of emergency response costs and labor costs.

[0007] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a technique that can improve the efficiency of operation and management of a sludge dewatering apparatus. [Means for solving the problem]

[0008] The sludge dehydration apparatus disclosed herein is a sludge dehydration apparatus including a sludge storage tank in which sludge is stored, and a screw press dehydrator that dehydrates the sludge supplied from the sludge storage tank while transporting it by rotating a screw, and includes a moisture content acquisition unit that acquires the moisture content of the dehydrated sludge discharged from the screw press dehydrator, a sludge volume acquisition unit that acquires the current amount of sludge in the sludge storage tank, and a dehydration control unit that controls the operation of the screw press dehydrator based on detection results of the moisture content acquisition unit and the sludge volume acquisition unit, and the sludge volume acquisition unit acquires the current amount of sludge in the sludge storage tank and the process volume of the screw press dehydrator. and an estimated sludge volume, which is an estimate of the amount of sludge in the sludge storage tank after a predetermined time has elapsed, based on dehydration control information including at least the amount of sludge, and the dehydration control unit controls the operation of the screw press dehydrator so that the moisture content of the dehydrated sludge acquired by the moisture content acquisition unit becomes a predetermined set target value, and if the estimated sludge volume acquired by the sludge volume acquisition unit exceeds a predetermined upper limit value of the sludge volume of the sludge storage tank, the dehydration control unit adjusts the screw rotation speed, taking priority over the moisture content of the dehydrated sludge, so that the estimated sludge volume does not exceed the upper limit value of the sludge volume of the sludge storage tank. Effect of the Invention

[0009] According to the technique of the present disclosure, it is possible to improve the efficiency of operation management of a sludge dewatering apparatus. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of an overall configuration of a sludge dewatering apparatus according to an embodiment; [Diagram 2] 4 is a flowchart illustrating an example of control of a dewatering machine in a sludge dewatering apparatus according to an embodiment. [Diagram 3] 5 is a time chart showing an example of control of the screw rotation speed in a sludge dewatering apparatus according to a comparative example. [Figure 4] 4 is a time chart showing an example of control of the screw rotation speed in the sludge dewatering apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In addition, in all drawings for describing the embodiment, the same reference numerals are used for the same or substantially the same configurations, elements, etc. In addition, as a rule, configurations, elements, etc. that have been described once will not be described again.

[0012] <Overall configuration of sludge dewatering equipment> First, an example of the overall configuration of a sludge dewatering apparatus according to an embodiment will be described. Fig. 1 is a diagram showing an example of the overall configuration of a sludge dewatering apparatus according to an embodiment.

[0013] As shown in FIG. 1, the sludge dewatering apparatus 10 includes a sludge storage tank 20, a sludge relay tank 30, a measuring tank 40, a flocculation mixing tank 50, a screw press dewatering machine (hereinafter simply referred to as the “dewatering machine”) 60, and a control device 100.

[0014] The sludge storage tank 20 stores sludge (sludge wastewater) discharged from, for example, a manufacturing factory of food, chemical products, semiconductors, etc. The sludge storage tank 20 is provided with a first level gauge 21 and a first pump 22. The first level gauge 21 is provided to measure the amount of sludge stored in the sludge storage tank 20. As an example, the first level gauge measures the level of the sludge stored in the sludge storage tank 20, in other words, the water level (water surface height) of the sludge wastewater. The measurement result by the first level gauge 21 is sent to the control device 100. The first pump 22 is connected to a first pipe 23, which is a water supply line connecting the sludge storage tank 20 and the sludge relay tank 30. The sludge stored in the sludge storage tank 20 is sent to the sludge relay tank 30 via the first pipe 23 by the first pump 22.

[0015] The sludge relay tank 30 is a storage tank smaller than the sludge storage tank 20, and is provided between the sludge storage tank 20 and the flocculation and mixing tank 50. In other words, the sludge relay tank 30 is a so-called service tank, and temporarily stores the sludge sent from the sludge storage tank 20 to the flocculation and mixing tank 50. A flow meter 24 is provided on a first pipe 23 connecting the sludge storage tank 20 and the sludge relay tank 30. The flow meter 24 measures the flow rate of sludge flowing from the sludge storage tank 20 to the sludge relay tank 30 via the first pipe 23.

[0016] The sludge relay tank 30 is provided with a second level gauge 31 and a second pump 32. The second level gauge 31 measures the level of the sludge stored in the sludge relay tank 30. The measurement result by the second level gauge 31 is sent to the control device 100. The second pump 32 is connected to a second pipe 33, which is a water supply line connecting the sludge relay tank 30 and the metering tank 40. The sludge stored in the sludge relay tank 30 is sent by the second pump 32 through the second pipe 33 to the metering tank 40.

[0017] Metering tank 40 is a storage tank for measuring the flow rate of sludge flowing into flocculation mixing tank 50. Metering tank 40 constitutes a so-called weir type flowmeter, and is formed continuous with flocculation mixing tank 50 via, for example, a tank inner wall surface having a V-shaped groove (in other words, a V-weir) 41.

[0018] The flocculation mixing tank 50 is internally provided with an agitator 51 for agitating the sludge flowing in from the metering tank 40. The agitator 51 is provided with an agitator blade 52 disposed in the flocculation mixing tank 50, and an agitator motor 53 connected to the agitator blade 52. A supply pipe 71 leading to a flocculant tank 70 is also connected to the flocculation mixing tank 50, and this supply pipe 71 is provided with a third pump 72. The flocculant stored in the flocculant tank 70 is supplied to the flocculation mixing tank 50 via the supply pipe 71 by the third pump 72.

[0019] In the flocculation mixing tank 50, the sludge and the flocculant are mixed by stirring using a stirrer 51. As a result, the sludge in the flocculation mixing tank 50 becomes a state in which flocculated flocs are generated. The sludge in the state in which flocculated flocs are generated is then supplied from the flocculation mixing tank 50 to the dehydrator 60 via a fourth pipe 54. The flocculation mixing tank 50 is provided with a third level gauge 55. The third level gauge 55 measures the level of the sludge stored in the flocculation mixing tank 50. The measurement result by the third level gauge 55 is sent to the control device 100.

[0020] The screw press dehydrator 60 dehydrates the sludge flowing from the sludge storage tank 20 through the coagulation mixing tank 50 while conveying it with a screw. The configuration of the dehydrator 60 is an existing one, so it will be briefly described. It has a screw 62 provided in a cylindrical screen 61. A drive motor 64 driven by power supplied via an inverter 63 is connected to one axial end of the screw 62, and the screw 62 rotates at a predetermined rotation speed using the drive motor 64 as a power source. In addition, a press plate 65 is provided near the other axial end of the screw 62, i.e., the end of the screen 61 opposite to the drive motor 64, for pressing the sludge conveyed by the screw 62. In other words, the press plate 65 is provided at the outlet of the dehydrator 60 from which the sludge is discharged.

[0021] The sludge that flows from the flocculation mixing tank 50 into the dehydrator 60 via the fourth pipe 54 is transported through the screen 61 by the screw 62 that is rotated at a predetermined speed by the drive motor 64, and at that time, the filtrate is separated through the screen 61. The sludge from which the filtrate has been separated is further consolidated by the outlet resistance of the pressure plate 65, and becomes dehydrated.

[0022] The moisture content of the sludge that has flowed into the dehydrator 60 gradually decreases while it is transported through the screen 61 by the screw 62, and the sludge is dehydrated. The moisture content of the sludge dehydrated in the dehydrator 60 (dehydrated sludge) varies depending on the rotation speed of the screw 62. Specifically, the lower the rotation speed of the screw 62, the lower the moisture content of the dehydrated sludge.

[0023] The dewatered sludge thus transported within the screen 61 by the screw 62 and dewatered is pushed out from the outer periphery of the pressing plate 65 to the outside of the screen 61 and gradually falls off from the mass of dewatered sludge. It can also be said that the dewatered sludge finally falls off from the press screw dewatering machine 60. The fallen dewatered sludge is stored in a dewatered sludge container 66 installed outside the dewatering machine 60.

[0024] Although not shown, the pressure plate 65 is configured to be movable within a predetermined range in the axial direction of the screw 62. The size of the outlet through which the dewatered sludge is discharged is adjusted depending on the position of the pressure plate 65, and the outlet resistance changes accordingly. The larger the outlet resistance, the lower the moisture content of the dewatered sludge tends to be.

[0025] The dehydrator 60 also includes a camera 67, which is an imaging device that images the outer periphery of the pressure plate 65, i.e., the outlet portion of the dehydrator 60. The camera 67 is provided to image the dehydrated sludge (dehydrated sludge discharged from the dehydrator 60) discharged from the outer periphery of the pressure plate 65. The image captured by the camera 67 may be a still image or a video image.

[0026] The control device 100 is configured to include, for example, a CPU (Central Processing Unit), a memory, etc., and performs comprehensive control of the sludge dewatering device 10. The control device 100 appropriately controls the operations of the first pump 22, the second pump 32, and the third pump 72 based on, for example, the measurement results of the first level gauge 21, the second level gauge 31, the third level gauge 55, the flow meter 24, etc., so that sludge appropriately flows from the sludge storage tank 20 into the dewatering machine 60, and also controls the operation of the dewatering machine 60.

[0027] The following describes in more detail how the control device 100 controls the operation of the dehydrator 60. Specifically, the control device 100 includes at least a moisture content acquisition unit 110, a sludge amount acquisition unit 120, a dehydration control unit 130, and a memory unit 140.

[0028] Further, an input / output device (input device) 200 serving as a user interface is connected to the control device 100. The configuration of the input / output device 200 is not particularly limited, and may be, for example, a display, a keyboard, and the like. When a user (such as an operation manager) operates the input / output device 200, for example, a part of the dehydration control information used to control the operation of the dehydrator 60 is input, and the input dehydration control information is stored in the storage unit 140. Further, the input / output device 200 displays various information for the user.

[0029] The contents of the dehydration control information input by the input / output device 200 are not particularly limited, and may include, for example, a target value for the moisture content of the dehydrated sludge (hereinafter referred to as the "set target value"), a lower limit value for the rotation speed of the screw 62 (hereinafter referred to as the "lower limit value of rotation speed"), an upper limit value for the rotation speed of the screw 62 (hereinafter referred to as the "upper limit value of rotation speed"), an initial value for the rotation speed of the screw 62 (hereinafter referred to as the "initial rotation speed value"), an operation plan (operation time period) for the dehydrator 60, a schedule for the inflow of sludge into the sludge storage tank 20, an upper limit value for the amount of sludge in the sludge storage tank 20 (hereinafter referred to as the "upper limit value of sludge amount"), etc. In this way, the input / output device 200 accepts inputs of an operation plan for the screw press dehydrator 60, a schedule for the amount of sludge inflow into the sludge storage tank 20, etc., as pieces of dehydration control information.

[0030] The moisture content acquisition unit 110 acquires the moisture content of the dewatered sludge discharged from the outer periphery of the pressing plate 65 and stored in the dewatered sludge container 66, i.e., the moisture content of the sludge (dewatered sludge) dewatered by the dewaterer 60. In this embodiment, the moisture content acquisition unit 110 estimates the moisture content of the dewatered sludge based on a current (real-time) image of the dewatered sludge captured by the camera 67. In other words, the moisture content acquisition unit 110 functions as an analysis device that analyzes the image captured by the camera 67, and estimates the moisture content of the dewatered sludge by image analysis.

[0031] More specifically, the moisture content acquisition unit 110 estimates the moisture content of the dewatered sludge based on an image of a portion of the dewatered sludge before it falls off from the lump of dewatered sludge captured by the camera 67. In other words, the moisture content acquisition unit 110 estimates the moisture content of the dewatered sludge based on an image of a portion of the dewatered sludge that is attached to the pressing plate 65 of the press screw dewaterer 60, etc., captured by the camera 67. By estimating the moisture content from the shape, color, etc. of the dewatered sludge based on an image of the dewatered sludge before it falls off in this way, the accuracy of the moisture content estimation can be improved.

[0032] As an example, the moisture content acquisition unit 110 estimates the moisture content of the dewatered sludge using a previously created learning model of the moisture content. The learning model of the moisture content is created from a plurality of past images of the accumulated dewatered sludge and the moisture content of the dewatered sludge corresponding to each image.

[0033] The moisture content learning model is basically created using a measurement evaluation value measured by a moisture content meter or the like, but may also be created by the operation manager using a sensory evaluation value based on his or her own senses (sight, touch, smell, etc.). The method of estimating the moisture content by the moisture content acquisition unit 110 is not particularly limited, and does not have to be estimation based on an image of the dewatered sludge. Furthermore, the method of acquiring the moisture content by the moisture content acquisition unit 110 is not particularly limited, and may of course acquire a value obtained by measuring the moisture content by a measuring instrument or the like.

[0034] The sludge amount acquiring unit 120 acquires the current amount of sludge in the sludge tank 20 (hereinafter also referred to as the "current sludge amount"). More specifically, the sludge amount acquiring unit 120 acquires the measurement result of the first level meter 21 as the current sludge amount in the sludge tank 20 at a predetermined timing. In this example, the sludge amount acquiring unit 120 acquires the measurement result of the first level meter 21, i.e., the height (level) of the sludge stored in the sludge tank 20, as the current sludge amount in the sludge tank 20 at a fixed sampling interval, for example, at intervals of about 10 minutes.

[0035] Furthermore, the sludge volume acquisition unit 120 estimates (predicts) the sludge volume in the sludge tank 20 after a predetermined time has elapsed based on the current sludge volume in the sludge tank 20 acquired as described above, as well as the dehydration control information. That is, the sludge volume acquisition unit 120 estimates (predicts) the future sludge volume in the sludge tank 20 based on the current sludge volume and the dehydration control information. In other words, the sludge volume acquisition unit 120 obtains an estimate of the future sludge volume in the sludge tank 20 (hereinafter referred to as the "estimated sludge volume"). In this example, the sludge volume acquisition unit 120 obtains the height (level) of the sludge in the sludge tank 20 after a predetermined time has elapsed as the estimated sludge volume.

[0036] Here, the dehydration control information includes information on the dehydrator 60 obtained in the sludge dehydration apparatus 10, and specifically includes at least information on the throughput of the dehydrator 60 (amount processed per unit time). The throughput of the dehydrator 60 is estimated, for example, from the rotation speed of the screw 62. The rotation speed of the screw 62 is calculated, for example, from the current value of the drive motor 64. The dehydration control information may also include information input by operating the input / output device 200 as described above.

[0037] The dehydration control unit 130 controls the operation of the dehydrator 60 based on the information acquired by the moisture content acquisition unit 110 and the sludge volume acquisition unit 120. More specifically, the dehydration control unit 130 controls the operation of the dehydrator 60 based on the moisture content of the dehydrated sludge acquired by the moisture content acquisition unit 110 and the current sludge volume and estimated sludge volume acquired by the sludge volume acquisition unit 120.

[0038] Basically, the dehydration control unit 130 appropriately controls the operation of the dehydrator 60 so that the moisture content of the dehydrated sludge discharged from the dehydrator 60 becomes a preset target value. For example, the dehydration control unit 130 appropriately adjusts the rotation speed of the screw 62, the position of the pressing plate 65, and the like so that the moisture content of the dehydrated sludge acquired by the moisture content acquisition unit 110 approaches the set target value.

[0039] Furthermore, the dehydration control unit 130 determines whether the estimated sludge amount acquired by the sludge amount acquisition unit 120 exceeds a preset sludge amount upper limit at a predetermined timing. If the dehydration control unit 130 determines that the estimated sludge amount exceeds the sludge amount upper limit, it adjusts the rotation speed of the screw 62 so that the estimated sludge amount does not exceed the sludge amount upper limit of the sludge tank 20, giving priority to the moisture content of the dehydrated sludge.

[0040] In other words, when the estimated sludge volume acquired by the sludge volume acquisition unit 120 exceeds the sludge volume upper limit value, the dewatering control unit 130 allows the moisture content of the dewatered sludge to exceed the set target value, and adjusts the rotation speed of the screw 62 so that the estimated sludge volume does not exceed the sludge volume upper limit value.

[0041] In this way, when the estimated sludge volume exceeds the upper sludge volume limit, the dewatering control unit 130 prioritizes the moisture content of the dewatered sludge and adjusts the rotation speed of the screw 62 so that the estimated sludge volume does not exceed the upper sludge volume limit, thereby improving the efficiency of operational management of the sludge dewatering device 10. Note that the adjustment range of the rotation speed of the screw 62 may be set appropriately, but it is preferable that the dewatering control unit 130 adjusts the rotation speed of the screw 62 between the preset upper and lower rotation speed limit values.

[0042] <How to adjust the screw rotation speed> Next, there will be described an example of a method for controlling the sludge dewatering apparatus 10, in particular, a method for adjusting the rotation speed of the screw 62. Fig. 2 is a flow chart showing an example of a method for adjusting the rotation speed of the screw.

[0043] The control device 100 of the sludge dewatering device 10 determines an appropriate rotation speed of the screw 62 at regular intervals, for example, of about 10 minutes, and appropriately controls the dewatering machine 60 so that the screw 62 rotates at the determined rotation speed.

[0044] 2, first, in step S1, the dehydration control unit 130 acquires dehydration control information necessary for controlling the dehydrator 60. As described above, the dehydration control information may include information such as a set target value, a lower limit value of the rotation speed, an upper limit value of the rotation speed, an initial value of the rotation speed, an operation plan (operation time period) of the dehydrator 60, a schedule for the inflow of sludge into the sludge storage tank 20, and an upper limit value of the sludge amount.

[0045] Next, the moisture content acquisition unit 110 acquires the moisture content of the dewatered sludge. In this example, the moisture content acquisition unit 110 estimates the moisture content of the dewatered sludge from the current image of the dewatered sludge captured by the camera 67 as described above and a learning model of the moisture content created in advance (step S2).

[0046] Next, the dehydration control unit 130 adjusts the rotation speed of the screw 62 so that the moisture content of the dehydrated sludge acquired by the moisture content acquisition unit 110 approaches a set target value (step S3). As an example, the dehydration control unit 130 acquires the current rotation speed of the screw 62, and calculates an adjustment value for the rotation speed of the screw 62 according to, for example, the difference between the moisture content of the dehydrated sludge acquired by the moisture content acquisition unit 110 and the set target value, and calculates an output value of the screw 62 from this adjustment value. Then, the screw 62 is rotated at this output value.

[0047] As an example, the spin-drying control unit 130 calculates the number of rotations of the screw 62 from the current value of the drive motor 64 that rotates the screw 62. The method of acquiring the number of rotations of the screw 62 is not particularly limited, and the number of rotations of the screw 62 may, of course, be measured.

[0048] Next, the dehydration control unit 130 acquires the throughput of the dehydrator 60 (step S4). As an example, the dehydration control unit 130 estimates the throughput of the dehydrator 60 (the throughput per unit time) from a learning model of the throughput created in advance.

[0049] Here, the throughput of the dehydrator 60 may vary depending on various conditions such as the properties of the sludge, in addition to the rotation speed of the screw 62. For this reason, the dehydration control unit 130 estimates the throughput of the dehydrator 60 using a learning model of the throughput created in advance. This can improve the accuracy of the throughput of the dehydrator 60.

[0050] The learning model of the throughput is created, for example, by extracting multiple combinations of the accumulated past rotation speed of the screw 62 and the throughput of the dehydrator 60. The throughput of the dehydrator 60 is estimated based on, for example, the detection results (output signals) of the first level meter 21, the second level meter 31, the third level meter 55, and the flow meter 24.

[0051] Next, the sludge amount acquisition unit 120 acquires the sludge amount (estimated sludge amount) after a predetermined time, for example, several hours, has elapsed (step S5). That is, the sludge amount acquisition unit 120 estimates the sludge amount in the sludge storage tank 20 after the predetermined time has elapsed. More specifically, the sludge amount acquisition unit 120 estimates the sludge amount in the sludge storage tank 20 after the predetermined time has elapsed based on the current sludge amount in the sludge storage tank 20 and information such as the processing amount of the dehydrator 60 obtained in step S4, the operation plan of the dehydrator 60, and the sludge inflow amount plan (incoming amount plan) to the sludge storage tank 20.

[0052] Next, the dehydration control unit 130 determines whether the estimated sludge amount acquired by the sludge amount acquisition unit 120 exceeds the sludge amount upper limit (step S6). If it is determined that the estimated sludge amount exceeds the sludge amount upper limit (step S6: Yes), the process proceeds to step S7, where the dehydration control unit 130 adjusts the rotation speed of the screw 62 based on the estimated sludge amount, prioritizing the moisture content of the dehydrated sludge. In other words, the dehydration control unit 130 determines and adjusts the rotation speed of the screw 62 so that the moisture content of the dehydrated sludge exceeds the set target value and the estimated sludge amount does not exceed the sludge amount upper limit.

[0053] On the other hand, if it is determined that the estimated sludge volume does not exceed the sludge volume upper limit value (step S6: No), the dewatering control unit 130 continues adjusting the rotation speed of the screw 62 based on the moisture content of the dewatered sludge without adjusting the rotation speed of the screw 62 based on the estimated sludge volume.

[0054] In this way, when the estimated sludge volume exceeds the upper sludge volume limit value, the rotation speed of the screw 62 is adjusted so that the moisture content of the dewatered sludge is prioritized and the estimated sludge volume does not exceed the upper sludge volume limit value, thereby making it possible to improve the efficiency of operational management of the sludge dewatering device 10.

[0055] <Examples of screw speed control> Next, a specific example of the control of the screw rotation speed in the sludge dewatering apparatus of the comparative example and the embodiment will be described. FIG. 3 is a time chart showing the change of various parameters during sludge dewatering treatment by the sludge dewatering apparatus of the comparative example. FIG. 4 is a time chart showing the change of various parameters during sludge dewatering treatment by the sludge dewatering apparatus of the embodiment. Specifically, FIG. 3 and FIG. 4 show the change over three days in the parameters during sludge dewatering treatment, such as the water content of the sludge, the screw rotation speed, the planned inflow amount of sludge into the sludge storage tank, the operation plan of the dewatering machine, the processing amount of the dewatering machine, and the sludge storage tank level (corresponding to the above-mentioned current sludge amount and estimated sludge amount). Note that the current sludge amount and the estimated sludge amount are generally the same, although there may be some errors, so in FIG. 3 and FIG. 4, these are collectively shown as the sludge storage tank level.

[0056] In the embodiment and the comparative example, the "operation plan" and the "inflow amount plan" are the same. The dehydrator is operated at a certain time each day based on the "operation plan", and in this example, it is operated during the period when the value of the "operation plan" is "1". The dehydrator is operated between times T1 and T2 on the first day, between times T3 and T4 on the second day, and between times T6 and T7 on the third day, and the operation time per day is about 8 hours. Also, sludge flows into the sludge tank based on the "inflow amount plan", and flows continuously at a constant flow rate between times T1 on the first day and T5 on the second day, and between times T6 and T7 on the third day.

[0057] <Sludge dewatering device of comparative example> In the sludge dewatering apparatus of the comparative example, the screw rotation speed of the dewatering machine is appropriately controlled based on the moisture content of the dewatered sludge. As shown in Fig. 3, when the operation of the dewatering machine starts at time T1 on the first day, the screw starts rotating at a preset initial value. As an example, the initial value is set to approximately the midpoint between the upper and lower limit values ​​of the rotation speed.

[0058] Thereafter, the screw rotation speed is adjusted so that the moisture content of the dewatered sludge approaches the set target value, as described above. In this example, the moisture content of the dewatered sludge immediately after the screw is rotated at the initial value is lower than the set target value. Therefore, the screw rotation speed is subsequently adjusted to a value slightly higher than the initial value so that the moisture content of the dewatered sludge approaches the set target value.

[0059] Sludge flows into the sludge tank from time T1, the same time the dehydrator starts operating, but because the screw rotation speed is adjusted to a value higher than the initial value, the sludge tank level gradually decreases while the dehydrator is operating. Also, the operation of the dehydrator on the first day ends at time T2, but sludge continues to flow into the sludge tank, so the current sludge amount (sludge tank level) gradually increases thereafter.

[0060] At time T3 when the dehydrator starts operation on the second day, the current sludge volume exceeds the first threshold, which is the upper limit of the sludge volume. In the sludge dehydration device of the comparative example, even in this state, the screw rotation speed is adjusted based on the moisture content of the dehydrated sludge.

[0061] When the dehydrator starts operating at time T3 on the second day, as on the previous day, the screw starts rotating at a preset initial value, and then the screw rotation speed is adjusted so that the moisture content of the dehydrated sludge approaches the set target value. In this example, the moisture content of the dehydrated sludge is higher than the set target value immediately after time T3, and the screw rotation speed is then adjusted to a value lower than the initial value and closer to the lower limit of the rotation speed so that the moisture content of the dehydrated sludge approaches the set target value.

[0062] In this way, by adjusting the screw rotation speed to a value close to the lower limit of the rotation speed, the processing volume of the dehydrator is lower than that of the previous day. Therefore, even though the dehydrator is operating between times T3 and T4 on the second day, the current sludge volume is slightly increased. Furthermore, because sludge continues to flow into the sludge tank until time T5 after time T4 when the operation of the dehydrator ends, the current sludge volume at time T5 greatly exceeds the first threshold value.

[0063] Thereafter, when the dehydrator starts operating at time T6 on the third day, the screw starts rotating at a preset initial value, as on the previous day, and then the screw rotation speed is adjusted so that the moisture content of the dehydrated sludge approaches the set target value. In this example, since the moisture content of the dehydrated sludge immediately after time T6 is lower than the set target value, the screw rotation speed is then adjusted to a value higher than the initial value and closer to the upper rotation speed value so that the moisture content of the dehydrated sludge approaches the set target value.

[0064] By adjusting the screw rotation speed to a value close to the upper limit of the rotation speed, the processing volume of the dehydrator increases from the previous day, so that although sludge flows into the sludge tank between times T3 and T4 on the third day, the current sludge volume gradually decreases. Then, at time T7 when the operation of the dehydrator ends, the current sludge volume has decreased to near the first threshold value.

[0065] Thus, in the sludge dewatering apparatus of the comparative example, the moisture content of the dewatered sludge is always close to the set target value, but the current sludge amount continues to exceed the first threshold value after time T3 on the second day. In other words, in the sludge dewatering apparatus of the comparative example, a state in which sludge is at risk of overflowing from the sludge storage tank continues for a long period of time after time T3 on the second day. Such a state in which sludge is at risk of overflowing from the sludge storage tank is likely to cause a situation that requires personnel to take action, so it is not preferable for this state to continue for a long period of time.

[0066] <Sludge removal device of the embodiment> On the other hand, in the sludge dewatering apparatus of the embodiment, the screw rotation speed is basically appropriately controlled based on the moisture content of the dewatered sludge, but when the estimated sludge volume (sludge tank level) exceeds a first threshold value, which is the upper limit value of the sludge volume, the screw rotation speed is adjusted so that the estimated sludge volume does not exceed the first threshold value, taking precedence over the moisture content of the dewatered sludge. In other words, the control of the screw rotation speed is basically performed based on the moisture content of the dewatered sludge, but when the estimated sludge volume exceeds the first threshold value, the control is switched to the control based on the moisture content of the dewatered sludge. Also, when the control based on the estimated sludge volume is performed, the control is switched to the control based on the moisture content of the dewatered sludge when the estimated sludge volume and the current sludge volume each fall below a second threshold value lower than the first threshold value.

[0067] As shown in Figure 4, in the sludge dewatering apparatus of the embodiment, as in the sludge dewatering apparatus of the comparative example, when the dewatering machine starts operating at time T1 on the first day, the screw starts rotating at a preset initial value, and then the screw rotation speed is adjusted so that the moisture content of the dewatered sludge approaches the set target value.

[0068] In the sludge dewatering apparatus of the embodiment, an estimated sludge amount, which is the amount of sludge after a predetermined time has elapsed, is calculated during that time, and it is determined whether or not this estimated sludge amount exceeds a first threshold value. For example, at time T1, an estimated sludge amount, which is the amount of sludge at time T11, several hours after time T1, is calculated, and it is determined whether or not this estimated sludge amount exceeds the first threshold value. The estimated sludge amount at time T11 (the value estimated at time T1) does not exceed the first threshold value. Therefore, at time T1, the screw rotation speed is adjusted based on the moisture content of the dewatered sludge. The determination of whether or not the estimated sludge amount exceeds the first threshold value is performed, for example, at regular intervals.

[0069] Here, sludge flows into the sludge tank at the same time T1 as the dehydrator starts operating, but because the screw rotation speed is adjusted to a value higher than the initial value, the estimated sludge volume and current sludge volume gradually decrease while the dehydrator is operating (times T1-T2). Also, the operation of the dehydrator ends at time T2, but sludge continues to flow into the sludge tank, so the estimated sludge volume and current sludge volume gradually increase thereafter.

[0070] However, in this example, the estimated sludge amount after a predetermined time has elapsed during the operation period of the dehydrator on the first day (times T1-T2) will not exceed the first threshold. Therefore, during the operation period of the dehydrator on the first day, the screw rotation speed is adjusted based on the moisture content of the dehydrated sludge. In addition, the dehydrator stops at time T2, but while the dehydrator is stopped (between times T2 and T3), a determination as to whether the estimated sludge amount exceeds the first threshold is made at predetermined intervals, and the control of the screw rotation speed is switched based on the result of this determination.

[0071] Therefore, when the dehydrator starts operation on the second day (time T3), the screw rotation speed is adjusted based on the estimated sludge volume, giving priority to the moisture content of the dehydrated sludge. In this example, since the current sludge volume at the start of operation of the dehydrator on the second day (time T3) exceeds the first threshold, the screw rotation speed at time T3 is adjusted based on the estimated sludge volume, giving priority to the moisture content of the dehydrated sludge.

[0072] More specifically, the estimated sludge volume at time T3, estimated at time T31, several hours before time T3, exceeds the first threshold value. Therefore, at time T31, control of the screw rotation speed is switched from control based on the moisture content of the dewatered sludge to control based on the estimated sludge volume. In addition, the sludge tank level (estimated sludge volume, current sludge volume) does not fall below the second threshold value between time T31 and time T3. Therefore, when the dehydrator starts operating on the second day (time T3), the screw rotation speed is adjusted based on the estimated sludge volume.

[0073] At time T3, the screw starts rotating at a preset initial value, but thereafter, the screw rotation speed is adjusted to a value higher than the initial value so that the estimated sludge volume decreases. As a result, the estimated sludge volume and the current sludge volume (sludge tank level) gradually decrease. The adjustment range of the screw rotation speed is not particularly limited, but it is preferable to adjust the screw rotation speed between a preset upper limit value and a preset lower limit value. This makes it possible to suppress excessive adjustment of the screw rotation speed.

[0074] In this example, once the screw rotation speed is increased to the upper limit of the rotation speed, the screw rotation speed is maintained at the upper limit of the rotation speed until the current sludge amount falls below the first threshold. Thereafter, when the current sludge amount falls below the first threshold, the screw rotation speed is reduced from the upper limit of the rotation speed. In the example shown in Fig. 4, the screw rotation speed is reduced from the upper limit of the rotation speed at time T32 when the current sludge amount falls below the first threshold. Note that the screw rotation speed may also be reduced from the upper limit of the rotation speed when the estimated sludge amount, rather than the current sludge amount, falls below the first threshold.

[0075] However, at time T32, the screw rotation speed is not adjusted based on the moisture content of the dewatered sludge. For example, the screw rotation speed is controlled according to the estimated sludge amount until both the current sludge amount and the estimated sludge amount fall below a second threshold value that is lower than the first threshold value. Therefore, for a predetermined period from time T32, the screw rotation speed gradually decreases according to the estimated sludge amount. Accordingly, for a certain period from time T32, the moisture content of the dewatered sludge also gradually decreases. Note that the second threshold value is an arbitrary value lower than the first threshold value and is set in advance.

[0076] Therefore, during the operation period of the dehydrator on the second day (between times T3 and T4), the moisture content of the dehydrated sludge is higher than the set target value. However, compared to the sludge dehydration device of the comparative example, the estimated sludge volume and the current sludge volume can be reduced to values ​​lower than the first threshold value, which is the sludge volume upper limit, in a short time. In other words, in the sludge dehydration device of the embodiment, although the moisture content of the dehydrated sludge temporarily becomes higher than the set target value, the period during which the estimated sludge volume and the current sludge volume exceed the first threshold value, which is the sludge volume upper limit, can be suppressed to a short period of time.

[0077] Since the inflow of sludge into the sludge tank continues until time T5 after time T4 when the operation of the dehydrator ends, the estimated sludge amount and the current sludge amount gradually increase between times T4 and T5. However, even at time T5, the estimated sludge amount and the current sludge amount are maintained at values ​​slightly lower than the first threshold value, which is the upper limit value of the sludge amount. In other words, when adjusting the screw rotation speed based on the estimated sludge amount, the screw rotation speed is appropriately adjusted so that the estimated sludge amount at time T5 when the inflow of sludge into the sludge tank ends is lower than the first threshold value, which is the upper limit value of the sludge amount. In other words, the screw rotation speed is adjusted so that the estimated sludge amount at time T5 is lower than the first threshold value at a time point a predetermined time before time T5, for example, at a time point before time T4 when the operation of the dehydrator ends.

[0078] Also, as an example, the control of the screw rotation speed is reset once when the operation of the dehydrator for one day ends. For example, when the operation of the dehydrator ends at times T2, T4, and T7, the control of the screw rotation speed is reset once. If the control of the screw rotation speed is based on the estimated sludge volume at the time when the operation of the dehydrator ends for one day, the control of the screw rotation speed is once returned to control based on the moisture content of the dehydrated sludge, and then is appropriately switched again according to the estimated sludge volume. Therefore, for example, at the end of the operation on the second day (time T4), the control of the screw rotation speed is based on the estimated sludge volume, but at the start of the operation on the third day (time T6), the screw rotation speed is adjusted based on the moisture content of the dehydrated sludge.

[0079] As an example, the screw starts rotating at a preset initial value at time T6, and then the screw rotation speed is adjusted so that the moisture content of the dewatered sludge approaches the set target value. Since the moisture content of the dewatered sludge immediately after time T6 is lower than the set target value, the screw rotation speed is then adjusted to a value higher than the initial value and closer to the upper rotation speed value so that the moisture content approaches the set target value.

[0080] By adjusting the screw rotation speed to a value close to the upper limit of the rotation speed, the processing volume of the dehydrator is about the same as that of the previous day. Therefore, although sludge flows into the sludge tank during the operation period of the dehydrator (times T6 to T7), the estimated sludge volume and the current sludge volume gradually decrease. Then, at time T7 when the operation of the dehydrator ends, the estimated sludge volume and the current sludge volume are significantly lower than the first threshold value, which is the upper limit of the sludge volume.

[0081] As described above, in the sludge dewatering apparatus of the embodiment, although there are temporary periods when the moisture content of the dewatered sludge is higher than the set target value, the period during which the estimated sludge volume and the current sludge volume exceed the sludge volume upper limit value can be shortened. In other words, the period during which there is a risk of sludge overflowing from the sludge tank can be shortened. In other words, by optimizing the estimated sludge volume and the current sludge volume (sludge tank level) in this way, it becomes less likely that a situation will occur in which personnel will need to take sudden action against a leak from the sludge tank or the dewatered sludge container, a tank level alarm, etc., and this in turn makes it possible to improve the efficiency of the operation and management of the sludge dewatering apparatus and reduce the number of personnel required.

[0082] Although one embodiment of the technology of the present disclosure has been described above, the technology of the present disclosure is not limited to the above embodiment. It goes without saying that the technology of the present disclosure can be modified in various ways without departing from the gist of the technology.

[0083] For example, in the above embodiment, the screw rotation speed control is reset once at the end of the operation of the dehydrator for one day, but the screw rotation speed control does not necessarily have to be reset. The screw rotation speed control may be continued over multiple days.

[0084] In the above embodiment, the screw rotation speed control is switched even during the dehydrator operation stop period, but the screw rotation speed control does not have to be switched during the dehydrator operation stop period. In this case, when the dehydrator operation starts each day, the screw rotation speed may be controlled based on the estimated sludge amount after a predetermined time that is estimated at the start of operation. [Explanation of symbols]

[0085] 10...Sludge dewatering equipment 20…Sludge storage tank 21…First level gauge 22…First pump 23…First pipe 24…Flow meter 30…Sludge relay tank 31…Second level gauge 32…Second pump 33…Second piping 40...Measuring tank 41…Inner wall of tank 50...Agglomeration mixing tank 51... Stirring device 52...Mixing blade 53...Stirring motor 54…4th pipe 55…Third level gauge 60...Screw press dehydrator 61…Screen 62...Screw 63…Inverter 64...Drive motor 65…Pressure plate 66…Dewatered sludge container 67…Camera 70…Flocculant tank 71…Supply pipe 72…Third pump 100...Control device 110…Moisture content acquisition section 120…Sludge volume acquisition unit 130... Dehydration control unit 140...Storage section 200... Input / output device (input device)

Claims

1. A sludge dewatering apparatus comprising: a sludge storage tank in which sludge is stored; and a screw press dewatering machine that dewaters the sludge supplied from the sludge storage tank while conveying the sludge by rotating a screw, a moisture content acquisition unit that acquires a moisture content of the dewatered sludge discharged from the screw press dehydrator; a sludge amount acquiring unit for acquiring a current amount of sludge in the sludge storage tank; a dehydration control unit that controls an operation of the screw press dehydrator based on detection results of the moisture content acquisition unit and the sludge amount acquisition unit, The sludge amount acquisition unit, Further, an estimated sludge volume is obtained based on the current sludge volume in the sludge storage tank and dehydration control information including at least the throughput of the screw press dehydrator, and the estimated sludge volume is an estimated value of the sludge volume in the sludge storage tank after a predetermined time has elapsed; The dehydration control unit is controlling an operation of the screw press dehydrator so that the moisture content of the dewatered sludge acquired by the moisture content acquisition unit becomes a preset target value; and when the estimated sludge amount acquired by the sludge amount acquisition unit exceeds a preset upper limit value of the sludge amount of the sludge storage tank, the rotation speed of the screw is adjusted so that the estimated sludge amount does not exceed the upper limit value of the sludge amount of the sludge storage tank, taking precedence over the moisture content of the dewatered sludge. Sludge dewatering equipment.

2. The sludge dewatering apparatus according to claim 1, The dehydration control unit is The rotation speed of the screw is adjusted between a preset upper limit value and a preset lower limit value. Sludge dewatering equipment.

3. The sludge dewatering apparatus according to claim 1, An input device is provided for receiving an input of an operation plan of the screw press dehydrator as one of the dehydration control information. Sludge dewatering equipment.

4. The sludge dewatering apparatus according to claim 3, The input device further receives an input of a sludge inflow amount plan into the sludge storage tank as one of the dewatering control information. Sludge dewatering equipment.

5. The sludge dewatering apparatus according to claim 1, an imaging device for imaging the dewatered sludge discharged from the screw press dewatering machine; the moisture content acquisition unit estimates the moisture content of the dewatered sludge based on an image of a portion of the dewatered sludge before the dewatered sludge falls out of the screw press dewatering machine, the image being captured by the imaging device. Sludge dewatering equipment.

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