Dewatering System

Abstract

To provide a dewatering system which can grasp a state of sludge discharged from a screw press in real time.SOLUTION: A dewatering system DS includes: a dewatering device SP; an image acquisition device 200 which produces image data of a cake discharged from the dewatering device SP; and a control device 6 which determines a state of the cake on the basis of the image data acquired by the image acquisition device 200.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a dewatering system. [Background technology]

[0002] Screw presses have been known as devices that compress sludge (liquid-containing material) discharged from liquid treatment facilities such as water and sewage treatment plants, sewage treatment plants, industrial wastewater treatment plants, and organic waste treatment plants, and separate water from the sludge (i.e., dehydrate it).

[0003] This screw press comprises a filter cylinder formed from a screen (perforated plate) and a screw disposed inside the filter cylinder. The screw squeezes and dehydrates the sludge fed into the filter cylinder. The dehydrated sludge (cake) is discharged from the discharge end of the filter cylinder. It is desirable that the cake be discharged from the discharge end of the filter cylinder with its moisture content as low as possible. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-51582 [Patent Document 2] Patent Publication No. 2021-159878 [Patent Document 3] Patent Publication No. 2021-37508 Summary of the Invention [Problem to be solved by the invention]

[0005] Screw presses are widely used for dewatering sludge, but the dewatering state of sludge can change from moment to moment due to various factors (fluctuations in sludge properties (e.g., physical properties such as sludge concentration, sludge temperature, sludge viscosity, and sludge chemical composition) and fluctuations in sludge volume). In response to these factors, sludge dewatering is performed by adjusting the operating parameters of the screw press (e.g., coagulant injection rate and machinery rotation speed) to maintain the moisture content of the dewatered cake. However, fluctuations in sludge properties and volume pose challenges such as fluctuations in the moisture content of the dewatered cake and co-rotation (a phenomenon in which sludge in the dewatering machine cannot be transported to the discharge section).

[0006] Therefore, an object of the present invention is to provide a dewatering system that can grasp the state of sludge discharged from a screw press in real time. [Means for solving the problem]

[0007] In one aspect, a dehydration system is provided that includes a coaxial dehydration device having a first screw and a second screw, an image acquisition device that generates image data of a cake discharged from the dehydration device, and a control device that determines the state of the cake based on the image data acquired by the image acquisition device.

[0008] In one aspect, the control device determines the occurrence of co-rotation inside the dehydration device based on the image data. In one aspect, the control device determines whether or not there is a chip in the screw mark formed on the cake based on the image data, and determines whether or not the co-rotation has occurred based on the presence or absence of the chip. In one aspect, the dewatering device is equipped with a slit forming member that forms a slit in the cake along the cake transport direction, and the control device determines the occurrence of co-rotation based on the shape of the slit formed by the slit forming member.

[0009] In one embodiment, the control device increases the rotational speed of at least the second screw when it determines that the co-rotation is occurring. In one aspect, the control device determines the moisture content of the cake based on the image data. In one aspect, the control device divides the cake into a reference area and a comparison area to be compared with the reference area, using the screw marks formed on the cake as a boundary, based on the image data, and determines whether the moisture content of the comparison area is higher than the moisture content of the reference area.

[0010] In one embodiment, the control device adjusts the rotational speed of at least the second screw when at least one of the following conditions is met: a first condition that the moisture content of the comparison region deviates from a predetermined target value; and a second condition that the difference between the moisture content of the reference region and the moisture content of the comparison region is greater than or equal to a predetermined value. In one aspect, the dewatering device is equipped with a filter cylinder into which liquid-containing material is introduced and a pressure sensor that detects the pressure of the liquid-containing material against the filter cylinder, and the control device measures a pressure value based on a signal sent from the pressure sensor, constructs a sludge condition discrimination model based on data of the measured pressure value, and determines the operating state of the dewatering device based on the condition discrimination model and the image data. In one aspect, the control device includes a storage device that stores a model constructed by a machine learning algorithm, and a processing device that inputs the image data into the model and performs calculations to output a judgment result indicating the state of the cake from the model.

[0011] In one embodiment, the control device controls at least the rotational speed of the second screw based on the judgment result indicating the state of the cake so as to prevent the cake from rotating together with the second screw. In one embodiment, the control device controls at least the rotation speed of the second screw based on the determination result indicating the state of the cake so that the moisture content of the cake becomes a predetermined moisture content. [Effects of the Invention]

[0012] The control device can determine the state of the cake based on the image data acquired by the image acquisition device, and therefore can grasp the state of the sludge discharged from the screw press in real time. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows a dewatering system. [Figure 2] FIG. 1 illustrates an embodiment of a dewatering device. [Figure 3] FIG. 1 illustrates an image acquisition device. [Figure 4] 10A and 10B are diagrams showing an embodiment of a slit-forming member. [Figure 5] 5(a) and 5(b) are diagrams showing other embodiments of the slit-forming member. [Figure 6] FIG. 10 shows a slit made in a cake. [Figure 7] FIG. 10 is a diagram showing a chip that occurred in a screw mark. [Figure 8] FIG. 1 shows a cake divided into two regions. [Figure 9] FIG. 10 shows another embodiment of the screw press. [Figure 10] FIG. 10 is a diagram showing changes in pressure measurements when an abnormality occurs in the operating state of the screw press. [Figure 11] FIG. 10 is a diagram showing a data set that combines image data acquired by an image acquisition device and pressure value data. [Figure 12] FIG. 1 shows a data set of pressure values ​​and a data set of image data. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing a dehydration system. The dehydration system DS is a system for performing dehydration treatment on sludge (organic sludge) as organic waste. As shown in Fig. 1, the dehydration system DS includes a sludge storage tank 101 for storing sludge, a coagulation tank 103 for preparing coagulated sludge, and a sludge supply pump 102 for supplying the sludge in the sludge storage tank 101 to the coagulation tank 103.

[0015] The dewatering system DS includes a polymer dissolution tank 105 in which a polymer agent (i.e., a coagulant) is dissolved, and a polymer supply pump 106 that supplies the polymer agent in the polymer dissolution tank 105 to the coagulation tank 103. The coagulated sludge in the coagulation tank 103 is prepared by adding the polymer agent to the sludge. The dewatering system DS includes a thickener 104 that separates water from the coagulated sludge coagulated in the coagulation tank 103 to produce concentrated sludge with low fluidity, and a dewatering device SP that dewaters the concentrated sludge (liquid-containing matter) concentrated in the thickener 104.

[0016] Fig. 2 is a diagram showing one embodiment of a dehydrator. As shown in Fig. 2, the dehydrator SP includes a cylindrical screen casing (filter cylinder) 1, a coaxial (two-shaft) first screw 3 and a second screw 4 that are arranged concentrically with the screen casing 1 within the screen casing 1 and transport thickened sludge in a predetermined transport direction D, a first rotation mechanism 7 that rotates the first screw 3, and a second rotation mechanism 20 that rotates the second screw 4 independently of the first screw 3. Hereinafter, the dehydrator SP may be referred to as a screw press SP.

[0017] The screen casing 1 is formed from a screen (perforated plate) such as punched metal, and has a double structure with an outer cylinder and an inner cylinder. A sludge inlet (in other words, a hopper) 2 is formed at the upstream end of the screen casing 1. The sludge introduced into the screen casing 1 from the inlet 2 is transported in a predetermined transport direction D within the screen casing 1 by rotating first and second screws 3 and 4.

[0018] The dewatering system DS includes a control device 6 that controls the operation of the devices that constitute the dewatering system DS. As shown in Fig. 1, the control device 6 is configured to control the operation of the sludge supply pump 102, the polymer supply pump 106, the coagulation tank 103 (more specifically, the operation of the agitator 103a that agitates the mixed liquid of the polymer agent and sludge in the coagulation tank 103), the thickener 104, and the screw press SP.

[0019] As shown in FIG. 2, the control device 6 includes a storage device 6a that stores programs (including various data), and a processing device 6b that executes calculations according to instructions included in the programs stored in the storage device 6a.

[0020] The control device 6 is configured to control the operation of the first rotation mechanism 7 and the second rotation mechanism 20. The second screw 4 is connected to the first screw 3 so as to be rotatable independently of the first screw 3. The first screw 3 and the second screw 4 extend through the screen casing 1 and the discharge chamber 33, respectively. The discharge chamber 33 is connected to the screen casing 1. A plug cake, which will be described later, is discharged from the screen casing 1 into this discharge chamber 33. The axial length of the second screw 4 is shorter than the axial length of the first screw.

[0021] The first screw 3 has a first screw shaft 3A with a truncated cone shape (tapered shape) whose diameter gradually increases downstream in the sludge transfer direction D, and a first screw blade 3B fixed to the outer surface of the first screw shaft 3A. The second screw 4 has a cylindrical second screw shaft 4A and a second screw blade 4B fixed to the outer surface of the second screw shaft 4A. The second screw 4 is disposed downstream of the first screw 3 in the sludge transfer direction D.

[0022] The upstream end of the screen casing 1 is sealed by a blocking wall 8. One end of the first screw shaft 3A (the upstream end in the transfer direction D) extends through this blocking wall 8. A water sealing device 10 is installed on this blocking wall 8 to seal the gap between the blocking wall 8 and the first screw shaft 3A. The upstream end of the first screw shaft 3A extending through the blocking wall 8 is rotatably supported by bearings 11 and 12 installed on a base (not shown) while its axial movement is restricted. Note that one of the bearings 11 and 12 may be omitted.

[0023] The upstream end of the first screw shaft 3A is connected to a first rotation mechanism 7 for rotating the first screw 3. In this embodiment, the first rotation mechanism 7 includes a first driving machine (e.g., an electric motor) 14, a sprocket 15 fixed to the rotating shaft of the first driving machine 14, a sprocket 16 fixed to the first screw shaft 3A, and a chain 17 wound around these sprockets 15 and 16.

[0024] The sprocket 16 is located between the bearings 11 and 12. When the first driver 14 of the first rotation mechanism 7 is driven, the sprocket 15 fixed to the rotation shaft of the first driver 14 rotates, which in turn rotates the sprocket 16 fixed to the first screw shaft 3A via a chain 17. As a result, the first screw 3 is rotated by the first rotation mechanism 7. The first driver 14 is connected to the control device 6, which is configured to be able to control the operation of the first driver 14.

[0025] The second screw shaft 4A of the second screw 4 is arranged concentrically with the first screw shaft 3A. The outer diameter of the second screw shaft 4A is the same as the maximum diameter of the first screw shaft 3A. The second screw shaft 4A has a reduced diameter portion 4F that extends through the inner wall 33A of the discharge chamber 33.

[0026] The upstream end of the second screw shaft 4A is rotatably supported by the first screw shaft 3A via a plain bearing (not shown), and the downstream end of the second screw shaft 4A is rotatably supported while being constrained from moving in the axial direction by bearings 22 and 23 installed on a base (not shown). Note that the bearing 23 can be omitted.

[0027] The downstream end of the second screw shaft 4A is connected to a second rotation mechanism 20 for rotating the second screw 4. In this embodiment, the second rotation mechanism 20 includes a second driving machine (e.g., an electric motor) 24, a sprocket 25 fixed to the rotation shaft of the second driving machine 24, a sprocket 26 fixed to the second screw shaft 4A, and a chain 27 wound around these sprockets 25 and 26.

[0028] The sprocket 26 is located between the bearings 22 and 23. When the second driver 24 of the second rotation mechanism 20 is driven, the sprocket 25 fixed to the rotation shaft of the second driver 24 rotates, which in turn rotates the sprocket 26 fixed to the second screw shaft 4A via the chain 27. As a result, the second screw 4 is rotated by the second rotation mechanism 20.

[0029] The second driving machine 24 is connected to the control device 6. The second driving machine 24 has a built-in inverter (not shown), and the control device 6 is configured to be able to control the operation of the second driving machine 24 via the inverter. That is, the control device 6 can control the rotation speed and rotation direction of the second driving machine 24 via the inverter. The second driving machine 24 can rotate the second screw 4 independently of the first screw 3. The first driving machine 14 also has a built-in inverter (not shown) that can change the rotation speed and rotation direction of the first driving machine 14.

[0030] The first screw blade 3B extends spirally along the axial direction of the first screw shaft 3A, and the second screw blade 4B extends spirally along the axial direction of the second screw shaft 4A. The combined length of the portion of the first screw 3 to which the first screw blade 3B is fixed and the portion of the second screw 4 to which the second screw blade 4B is fixed is equal to or longer than the axial length of the screen casing 1.

[0031] A small gap is formed between the screen casing 1 (more specifically, the inner cylinder) and the first screw blade 3B, allowing the first screw blade 3B to rotate without contacting the screen casing 1. Similarly, a small gap is formed between the inner surface of the screen casing 1 and the second screw blade 4B, allowing the second screw blade 4B to rotate without contacting the screen casing 1.

[0032] The rotating first screw blade 3B and second screw blade 4B can transport sludge that has been introduced into the screen casing 1 from the inlet 2 formed at the upstream end of the screen casing 1 toward the discharge chamber 33 (i.e., in the transport direction D).

[0033] In this embodiment, the winding direction (i.e., helical direction) of the second screw blade 4B is opposite to the winding direction of the first screw blade 3B. Therefore, when the sludge introduced from the inlet 2 is sent to the discharge chamber 33, the second screw 4 is rotated in the opposite direction to the first screw 3, as shown in FIG.

[0034] In one embodiment, the winding direction of the second screw blade 4B may be the same as the winding direction of the first screw blade 3B. In this case, when the sludge introduced from the inlet 2 is sent to the discharge chamber 33, the second screw 4 is rotated in the same direction as the first screw 3.

[0035] 2, the screen casing 1 is divided into a dewatering region 1A in which the first screw 3 is disposed, and a plug-forming region 1B in which the second screw 4 is disposed. The space through which the sludge is transported in the dewatering region 1A is formed by the inner surface of the screen casing 1, the first screw blade 3B, and the first screw shaft 3A.

[0036] As shown in Figure 2, the cross-sectional area of ​​this transfer space gradually decreases along the sludge transfer direction D. Therefore, as the sludge introduced through the inlet 2 is transferred through this transfer space by the first screw blade 3B, the sludge is squeezed and dewatered. The filtrate that passes through the screen (perforated plate) of the screen casing 1 is collected in a filtrate receiver 38 disposed below the screen casing 1. A drain 39 is connected to the filtrate receiver 38, and the filtrate collected by the filtrate receiver 38 is discharged from the screw press SP via the drain 39.

[0037] The space through which the sludge is transferred in the plug formation region 1B is formed by the inner surface of the screen casing 1, the second screw blade 4B, and the second screw shaft 4A. As shown in Figure 2, the cross-sectional area of ​​this transfer space is constant. In the plug formation region 1B, a plug cake is formed from the sludge (i.e., cake) dewatered in the dewatering region 1A.

[0038] The cake in the plug-forming region 1B is compressed by being prevented from moving by the second screw flight 4B, resulting in a cake with a low moisture content. This cake with a low moisture content forms a plug cake that prevents the movement of subsequent cakes. The plug cake formed around the second screw shaft 4A applies back pressure to the subsequent cakes, further compressing them. The liquid separated from the plug cake in the plug-forming region 1B is collected in a filtrate receiver 38 and discharged from the screw press SP via a drain 39.

[0039] After the plug cake is formed, the control device 6 drives the second rotation mechanism 20 to rotate the second screw 4 (or operates the second rotation mechanism 20 to increase the rotational speed of the second screw 4). By rotating the second screw 4 in the direction opposite to the rotational direction of the first screw 3, the plug cake is sent out little by little to the discharge chamber 33 (i.e., discharged). In this way, the plug cake is continuously formed and discharged, so the screw press SP can be operated with a plug cake always present in the plug-forming region 1B.

[0040] However, in the screw press SP, the dehydration state of the sludge can change from moment to moment due to various events. Therefore, the dehydration system DS (more specifically, the control device 6) is configured to grasp the state of the cake discharged from the screw press SP in real time. This configuration will be described below with reference to the drawings.

[0041] FIG. 3 is a diagram showing an image capture device. As shown in FIGS. 2 and 3, the dewatering system DS includes an image capture device 200 that generates image data of the cake discharged from the screw press SP. The image capture device 200 is configured to generate still images or continuous images (i.e., video). The image data includes still image data and continuous image data (i.e., video data).

[0042] The image captured by the image capture device 200 may be a monochrome image, but is preferably a color image. An example of the image capture device 200 is an image sensor (e.g., a CCD image sensor or a CMOS image sensor). In one embodiment, the image capture device 200 may capture a photograph having a wavelength different from that of visible light, such as an infrared photograph or an ultraviolet photograph.

[0043] In the embodiment shown in Fig. 2, the image capturing device 200 is disposed on the discharge side of the screw press SP (i.e., the discharge end, on the discharge chamber 33 side). More specifically, the image capturing device 200 is disposed above the discharge chamber 33 (i.e., above the cake being discharged), and is capable of capturing images in real time of the cake being continuously discharged from the screen casing 1. The image capturing device 200 may adjust its shutter speed to capture more detailed image data of the cake being discharged.

[0044] There are no particular limitations on the location of the image capturing device 200, as long as the image capturing device 200 can capture an image of the cake being discharged from the screen casing 1. For example, the image capturing device 200 may be placed below the cake being discharged or to the side of the cake being discharged. To stabilize the imaging environment, the image capturing device 200 may be covered with a cover member.

[0045] 2, a single image capture device 200 is provided, but multiple image capture devices 200 may be provided, and the image capture device 200 may be a combination of a camera and a lighting device. To prevent dirt from adhering to the lens of the image capture device 200, the image capture device 200 may include a transparent plate (or filter) that covers the lens.

[0046] The control device 6 is electrically connected to the image acquisition device 200. The memory device 6a is configured to store image data of the cake acquired by the image acquisition device 200, and the processing device 6b is configured to determine the state of the cake based on the image data stored in the memory device 6a. In one embodiment, the control device 6 (more specifically, the processing device 6b) is configured to determine the occurrence of rotation of the cake based on the image data.

[0047] Fig. 4 is a diagram showing one embodiment of a slit forming member. As shown in Fig. 4, the screw press SP is equipped with a slit forming member 210 that forms slits in the cake along the cake transfer direction D. The slit forming member 210 is fixed to the outer surface of the screen casing 1 and is a scratching rod that makes marks (scratches) on the cake as it is discharged from the screen casing 1.

[0048] Figures 5(a) and 5(b) are views showing another embodiment of a slit-forming member. As shown in Figures 5(a) and 5(b), the screw press SP has a slit-forming member 211 disposed in a cylindrical member (sheath tube) 212 that extends in a straight line with the screen casing 1. The cylindrical member 212 is connected to the discharge chamber 33 (see Figure 2) and protrudes from the inner wall 33A. The slit-forming member 211 is fixed to the inner surface of the cylindrical member 212 and makes slits (marks, scratches) in the cake discharged from the screen casing 1.

[0049] Because the second screw blade 4B is not present in the cylindrical member 212, the rotating second screw blade 4B does not come into contact with the slit forming member 211 fixed to the inner surface of the cylindrical member 212. In one embodiment, when the axial length of the screen casing 1 is longer than the length of the portion of the second screw 4 to which the second screw blade 4B is fixed, even if the slit forming member 211 is fixed to the inner surface of the screen casing 1, the second screw blade 4B does not come into contact with the slit forming member 211. Therefore, in this case, the screw press SP does not necessarily have to include the cylindrical member 212.

[0050] 6 is a diagram showing slits made in the cake. The cake inside the screen casing 1 rotates together with the rotating second screw blade 4B and is discharged from the screen casing 1. The discharged cake has a screw mark formed by the rotating second screw blade 4B.

[0051] If there is no co-rotation of the discharged cake, the cake will rotate while being discharged smoothly from the screen casing 1, and the slits formed in the cake will extend at a constant rotation angle relative to the transfer direction D of the discharged cake. The slits are formed to clearly show the rotation angle of the discharged cake as image data, and the rotation angle of the slits corresponds to the rotation angle of the cake. The rotation angle of the slits refers to the rotation angle of the slit relative to the transfer direction D of the cake, and the closer the rotation angle of the slits is to a direction perpendicular to the transfer direction D of the cake, the larger the rotation angle of the slits becomes.

[0052] If co-rotation occurs in the discharged cake, part of the cake will stagnate inside the screen casing 1 and will not be discharged smoothly from the screen casing 1. Therefore, if co-rotation occurs, the rotation angle of the slit will be larger than the reference rotation angle, which is an index for determining whether co-rotation occurs.

[0053] The degree of co-rotation varies depending on the rotation angle of the slit. For example, if the degree of co-rotation is small, the rotation angle of the slit will be small (i.e., the slit rotation angle will approach a direction parallel to the cake transfer direction D). If the degree of co-rotation is large, the rotation angle of the slit will be large (i.e., the slit rotation angle will approach a direction perpendicular to the cake transfer direction D).

[0054] In this way, the control device 6 grasps the shape of the slit formed by the slit forming member 210 (or the slit forming member 211) (in this embodiment, the rotation angle of the slit) based on the image data acquired by the image acquisition device 200, and determines the occurrence of co-rotation based on the shape of the slit.

[0055] The control device 6 may additionally process the acquired image data (e.g., by processing or padding the image data). Examples of additional processing include trimming, black and white conversion, standardization, and compression. In one embodiment, the control device 6 may combine multiple pieces of image data together. For example, the control device 6 may combine multiple images captured by multiple image capture devices 200, or may combine multiple pieces of image data captured over time by a single image capture device 200.

[0056] The control device 6 not only determines whether or not there is co-rotation, but may also determine the degree of co-rotation (for example, low, medium, or high level of co-rotation) according to the rotation angle of the slit. The degree of co-rotation corresponds to the magnitude of the rotation angle of the slit, and data (correlation data) showing the correlation between the degree of co-rotation and the magnitude of the rotation angle of the slit is stored in the storage device 6a.

[0057] The control device 6 may include a memory device 6a storing at least one model constructed by a machine learning algorithm, and a processing device 6b that inputs image data into the model and performs calculations to output a determination result indicating the state of the cake from the model.

[0058] A suitable machine learning algorithm is the deep learning method. The deep learning method is a learning method based on a convolutional neural network (CNN) with multiple hidden layers. In this specification, machine learning using a neural network consisting of an input layer, two or more hidden layers, and an output layer is referred to as deep learning. By using the deep learning method, the condition of a cake, which has previously been determined based on human eyes and experience, can now be determined by a computer based on image data of the cake.

[0059] The input layer of the model receives pixel data that constitutes the image of the cake. The pixel data includes color index values ​​for each pixel (RGB values, brightness values ​​according to the grayscale, numerical values ​​representing white or black, etc.). The control device 6 performs calculations according to the algorithm defined in the neural network, and the output layer of the model outputs a judgment result indicating the state of the cake.

[0060] Using machine learning algorithms such as deep learning, it is possible to build a model that can determine the state of the cake by learning (supervised or unsupervised learning) various factors, including the rotation angle of the slits. The model, which uses a machine learning algorithm, is continuously updated based on newly obtained data in the dehydration system DS, which is operating using the model. A model that is updated to suit the actual situation can continuously output appropriate determination results.

[0061] The control device 6 may be a computer located on the screw press SP side, or may utilize a server on the cloud. The computer may be equipped with a GPU. The storage device 6a may be located inside the control device 6 or may be located outside the control device 6. The control device 6 may include an output device that outputs image data.

[0062] In addition to the control device 6, the dehydration system DS may also include a monitoring device (not shown) that acquires image data. The monitoring device may be configured to save captured images and output values ​​of image discrimination results, and a user may check and save the captured images and output values ​​of image discrimination results via the monitoring device. The monitoring device may also issue an alarm. The alarm may be issued to the screw press SP or to a central monitoring room. In one embodiment, an email corresponding to the alarm may be sent to an individual.

[0063] The server of the monitoring device may be an edge device or a cloud server. If the monitoring device is on a cloud server, the user may remotely monitor the condition of the cake via the Internet. The monitoring screen of the monitoring device may display captured images and videos, graphs of output results, graphs calculated from the output results (including moving average processing), graph legends, alarms, and control thresholds, and the user may set the above thresholds, etc. through the monitoring screen of the monitoring device. The monitoring device may be configured to perform calculations using the above output results.

[0064] FIG. 7 is a diagram showing chipping that has occurred in the screw trace. In one embodiment, the control device 6 may determine the presence or absence of chipping that has occurred in the screw trace formed by the second screw blade 4B based on image data, and determine the occurrence of co-rotation based on the presence or absence of chipping. The screw trace is formed by the rotating second screw blade 4B. In FIG. 7, chipping has occurred in the screw trace formed by the back side of the second screw blade 4B, but it may also occur in the screw trace formed by the front side of the second screw blade 4B.

[0065] Like the rotation angle of the slit, the degree of co-rotation varies depending on the size of the chipping that occurs in the screw mark. As shown in Fig. 7, if the degree of co-rotation is small, a small chipping occurs (see abnormality 1 in Fig. 7), and if the degree of co-rotation is large, a large chipping occurs (see abnormality 2 in Fig. 7). The control device 6 determines the shape of the chipping (for example, the size of the chipping) based on the image data acquired by the image acquisition device 200, and determines the degree of co-rotation based on the shape of the chipping.

[0066] In one embodiment, the control device 6 may determine the shape of the slit and the shape of the defect based on the image data, and may determine the occurrence of co-rotation based on these shapes. In one embodiment, the control device 6 may determine the shape of the slit and the shape of the defect by object detection (means for detecting position information of a specific object) based on the image data.

[0067] In one embodiment, the control device 6 may determine the size of the chip by area detection based on image data (means for detecting area information of a specific object). The image analysis method is not particularly limited. As the image analysis method, any of classification, object detection, and segmentation methods can be used.

[0068] According to this embodiment, the control device 6 can determine the state of the cake based on the image data acquired by the image acquisition device 200. Therefore, the control device 6 can grasp the state of the cake discharged from the screw press SP in real time.

[0069] The control device 6 determines that co-rotation is occurring based on the state of the cake, and operates the second rotation mechanism 20 (and / or the first rotation mechanism 7) to temporarily increase the rotation speed of the second screw 4 (and / or the first screw 3) above the current rotation speed. This configuration allows the cake to be quickly discharged, and the co-rotation can be resolved.

[0070] Patent Document 1 discloses a coaxial screw press but does not disclose a screw press SP configured as in this embodiment. In Patent Document 1, the first screw and the second screw rotate independently, making it difficult to appropriately control the rotation speeds of these two screws. For example, if the rotation speed of the second screw is too high, a plug for squeezing the subsequent sludge is not formed in the filter cylinder, and a cake with a high moisture content is discharged. On the other hand, if the rotation speed of the second screw is too low, the plug is subjected to high pressure from the subsequent sludge and sticks to the filter cylinder. In this embodiment, the control device 6 can grasp the state of the cake discharged from the screw press SP in real time, thereby appropriately controlling the rotation speed of the second screw 4 (and / or the first screw 3).

[0071] Patent Document 2 discloses generating an image of the outer surface of the filter cylinder, determining the rotation speed of the second screw based on the image, and rotating the second screw at the determined rotation speed. However, the camera capturing the image of the outer surface of the filter cylinder is located in a dehydrator room, which is a highly humid environment, where water and sludge are scattered due to the periodic cleaning of the filter cylinder. Therefore, camera maintenance is cumbersome due to the risk of the camera lens fogging up or water and sludge adhering to the camera lens. Furthermore, because the camera captures images of the side of the filter cylinder, it is difficult to directly determine the rotation and moisture content. According to this embodiment, the image capture device 200 is configured to capture images of the cake discharged from the screen casing 1, so problems arising from the installation environment of the image capture device 200 do not arise.

[0072] Patent Document 3 discloses that cameras are installed in the raw sludge, coagulation tank, thickening tank, etc. of a dehydrator (sliding shaft screw press, belt press, coaxial differential screw press) to keep the moisture content within a range. However, Patent Document 3 differs from the dehydration system DS, which captures images of cake discharged from a filter cylinder for a coaxial differential screw press that does not have a tapered cone. Patent Document 3 also has a different purpose from the dehydration system DS, which aims to constantly monitor the rotation (and / or moisture content of the cake). In the dehydration system DS of this embodiment, the control device 6 constantly monitors the dehydration state in more detail, such as the presence or absence of rotation and the moisture content, enabling more advanced operational control.

[0073] In one embodiment, the control device 6 may determine the moisture content of the cake based on the image data. For example, the control device 6 may determine the state of the moisture content (high, low, etc.) or may determine the moisture content value (e.g., percentage (%)). In one embodiment, the control device 6 may divide the moisture content value into ranges (e.g., ranges such as 70-75%, 75-80%, 80-85%). When dividing the value into ranges, the control device 6 preferably divides the ranges in increments of 3-5%, which provides high classification accuracy.

[0074] In one embodiment, the control device 6 may be configured to control at least the rotational speed of the second screw 4 based on the determination result indicating the state of the cake so that the moisture content of the cake becomes a predetermined moisture content.

[0075] Fig. 8 is a diagram showing a cake divided into two regions. As shown in Fig. 8, the control device 6 may divide the cake into two regions based on image data. More specifically, the control device 6 may divide the cake into a reference region SL1 and a comparison region SL2 that is compared with the reference region SL1, using the screw marks on the cake as the boundary.

[0076] The reference area SL1 is the area of ​​cake that is discharged from the screen casing 1 first in the cake transfer direction D, and the comparison area SL2 is the area of ​​cake that is discharged from the screen casing 1 after the reference area SL1 in the cake transfer direction D.

[0077] The control device 6 determines whether the moisture content of the comparison region SL2 is higher than the moisture content of the reference region SL1. For example, the control device 6 is configured to compare the moisture content of the reference region SL1 with the moisture content of the comparison region SL2, and if the moisture content of the comparison region SL2 deviates from a predetermined target value (first condition), operate the second rotation mechanism 20 to adjust (control) the rotation speed of the second screw 4. The predetermined target value is stored in the memory device 6a.

[0078] For example, if the moisture content of the comparison region SL2 is higher than the target value, the control device 6 reduces the rotation speed of the second screw 4 to lower the moisture content of the cake. If the moisture content of the comparison region SL2 is lower than the target value, the control device 6 increases the rotation speed of the second screw 4 to increase the moisture content of the cake. In one embodiment, the control device 6 may adjust (control) the rotation speed of the second screw 4 when the difference between the moisture content of the reference region SL1 and the moisture content of the comparison region SL2 is equal to or greater than a predetermined value (second condition).

[0079] In the above-described embodiment, in order to avoid co-rotation and / or to keep the moisture content of the cake within a target moisture content range, the control device 6 may control the amount of flocculant (inorganic or organic) added to the flocculation tank 103 (see FIG. 1), the amount of sludge fed to the screw press SP, and the rotation speeds of the components of the dehydration system DS (the agitator 103a of the flocculation tank 103, the thickener 104, and the first and second rotation mechanisms 7 and 20 of the screw press SP).

[0080] When co-rotation occurs, it is desirable that the control device 6 increase the rotation speed of the second screw 4. When the moisture content of the cake is outside the target moisture content range, it is desirable that the control device 6 control the amount of flocculant added and the rotation speed of the second screw 4.

[0081] Fig. 9 is a diagram showing another embodiment of the screw press. As shown in Fig. 9, the screw press SP is equipped with a plurality of pressure sensors 40 (40A, 40B, 40C, 40D) that detect the pressure of the sludge against the screen casing 1. In one embodiment, the screw press SP may be equipped with a single pressure sensor 40. Each of the plurality of pressure sensors 40 is electrically connected to the control device 6. Therefore, the control device 6 is configured to measure the pressure of the sludge against the screen casing 1 based on signals sent from each of the plurality of pressure sensors 40, and to determine the operating state of the screw press SP (more specifically, the first screw 3 and the second screw 4) based on the measured pressure.

[0082] As shown in Figure 9, the screen casing 1 is divided into a first screw area Pt where the first screw 3 is arranged, a second screw area Pp where the second screw 4 is arranged, and a transition area Py between the first screw area Pt and the second screw area Pp.

[0083] 9, the pressure sensors 40 are arranged in the first screw area Pt, the second screw area Pp, and the switching area Py, respectively. More specifically, the pressure sensors 40A and 40D are arranged in the first screw area Pt, the pressure sensor 40B is arranged in the second screw area Pp, and the pressure sensor 40C is arranged in the switching area Py.

[0084] FIG. 10 is a diagram showing changes in pressure measurements when an abnormality occurs in the operating state of the screw press. In FIG. 10, the horizontal axis represents time, and the vertical axis represents pressure measurements. In the graph shown in FIG. 10, the peaks of the pressure measurements in the first screw area Pt change irregularly. In this case, it is highly likely that the sludge in the screen casing 1 is co-rotating with the first screw 3. Therefore, the control device 6 can prevent the sludge from co-rotating with the first screw 3 by increasing the rotation speed of the first screw 3.

[0085] 11 is a diagram showing a data set that combines image data and pressure value data acquired by an image acquisition device. As shown in Fig. 11, the control device 6 may create a data set by integrating pressure value data (e.g., waveform data) measured based on signals sent from multiple pressure sensors 40 (or a single pressure sensor 40) and image data acquired by the image acquisition device 200.

[0086] As described above, the moisture content and whether or not there is co-rotation can be determined based on changes in pressure values ​​(higher pressure values ​​result in lower moisture content), and so using pressure value data allows for more accurate determination of the operating state. This pressure value data can be used as a data set to build a sludge condition determination model (moisture content, co-rotation). The data set of pressure values ​​used to build the model may use pressure values ​​as they are, or may use an image of a graph drawn based on the pressure values.

[0087] Fig. 12 is a diagram showing a data set of pressure values ​​and a data set of image data. The control device 6 may construct a data set by combining pressure value data (for example, waveform data) and image data as a sludge state discrimination model to be constructed (see Fig. 11), or may construct a data set of pressure values ​​and a data set of image data as shown in Fig. 12, and construct individual models from these data sets.

[0088] The control device 6 can measure the height of the sludge introduced into the inlet 2 based on the signal detected by the distance sensor 40D. If the measured sludge height is abnormally high or is on an upward trend even when the rotation speeds of the first screw 3 and the second screw 4 are appropriate, the amount of sludge introduced may be inappropriate, or the sludge may not be transported properly due to co-rotation of the sludge with the first screw 3. In this case, reducing the amount of sludge introduced or increasing the rotation speed of the first screw 3 can eliminate the co-rotation of the sludge with the first screw 3, thereby optimizing the operation of the screw press SP. In this way, the control device 6 can determine whether the sludge is co-rotating with the first screw 3 (and / or the second screw 4) based on the signal detected by the distance sensor 40D.

[0089] In this way, the control device 6 may be configured to determine the operating state of the screw press SP based on signals sent from each of the multiple pressure sensors 40A to 40C and the distance sensor 40D, and to determine the state of the cake based on image data.

[0090] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical concept of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0091] 1 Screen casing 1A Dehydration area 1B Plug formation region 2 Inlet 3 First screw 3A First screw shaft 3B First screw blade 4 Second screw 4A Second screw shaft 4B No. 2 screw blade 4F reduced diameter section 6. Control device 7 First rotation mechanism 8 Blocking wall 10 Water sealing device 11,12 Bearings 14 First Drive Unit 15,16 sprocket 17 Chain 20 Second rotation mechanism 22,23 Bearings 24 Second Drive 25,26 sprocket 27 Chain 33 Exhaust chamber 33A Inner wall 38 Filtrate receiver 39 Drain 40A~40C pressure sensor 40D distance sensor 101 Sludge storage tank 102 Sludge supply pump 103 Coagulation tank 103a Stirrer 104 Concentrator 105 Polymer melting tank 106 Polymer supply pump 200 Image acquisition device 210, 211 Slit forming member 212 Cylindrical member DS Dewatering System SP dehydration device (screw press)

Claims

1. a coaxial dewatering device having a first screw and a second screw; an image capture device that generates image data of the cake discharged from the dehydration device; and a control device that determines the state of the cake based on the image data acquired by the image acquisition device, The control device determines the occurrence of co-rotation inside the dehydration device based on the image data.

2. The control device Based on the image data, determine whether or not there is a chip in the screw mark formed on the cake; The dewatering system according to claim 1 , wherein occurrence of the co-rotation is determined based on the presence or absence of the chipping.

3. the dewatering device includes a slit forming member that forms a slit in the cake along a cake transfer direction, The dehydration system according to claim 1 , wherein the control device determines the occurrence of the co-rotation based on the shape of the slit formed by the slit forming member.

4. The dewatering system according to claim 1 , wherein the control device increases the rotational speed of at least the second screw when it determines that the co-rotation is occurring.

5. The dewatering system according to claim 1 , wherein the control device determines the moisture content of the cake based on the image data.

6. A coaxial dewatering device having a first screw and a second screw; an image capture device that generates image data of the cake discharged from the dehydration device; and a control device that determines the state of the cake based on the image data acquired by the image acquisition device, The control device Based on the image data, the cake is divided into a reference area and a comparison area to be compared with the reference area, using the screw marks formed on the cake as boundaries; A dewatering system that determines whether the moisture content of the comparison area is higher than the moisture content of the reference area.

7. The dewatering system described in claim 6, wherein the control device adjusts the rotational speed of at least the second screw when at least one of the following conditions is met: a first condition that the moisture content of the comparison area deviates from a predetermined target value; and a second condition that the difference between the moisture content of the reference area and the moisture content of the comparison area is greater than or equal to a predetermined value.

8. The dehydration device is a filter cylinder into which the liquid content is introduced; a pressure sensor for detecting the pressure of the liquid-containing substance against the filter cylinder, The control device measuring a pressure value based on a signal sent from the pressure sensor; A sludge state discrimination model is constructed based on the measured pressure value data, The dehydration system according to claim 1 , wherein the operating state of the dehydrator is determined based on the state discrimination model and the image data.

9. A coaxial dewatering device having a first screw and a second screw; an image capture device that generates image data of the cake discharged from the dehydration device; and a control device that determines the state of the cake based on the image data acquired by the image acquisition device, The control device a storage device in which a model constructed by a machine learning algorithm is stored; a processing device that inputs the image data into the model and executes a calculation to output a determination result indicating the state of the cake from the model, The control device controls at least the rotation speed of the second screw based on the determination result indicating the state of the cake so as to prevent the cake from rotating together with the second screw.

10. The dehydration system according to claim 9, wherein the control device controls at least the rotation speed of the second screw based on the determination result indicating the state of the cake so that the moisture content of the cake becomes a predetermined moisture content.

Images