Disk filter control system and method

Abstract

Disclosed is a disc filter system and method for dewatering a fiber suspension. The disc filter system includes a disc filter and a control system. The disc filter includes an inlet for introducing the fiber suspension into a tank, a rotor shaft, a variable speed drive unit operably connected to the rotor shaft, and at least one filter unit connected to the rotor shaft, the at least one filter unit rotating with the rotor shaft. The control system measures the torque applied to the variable speed drive unit and causes the variable speed drive unit to adjust the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed based on the torque applied to the variable speed drive unit.

Description

Cross - reference to related applications

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 472,051, filed on June 9, 2023, under the title "Disc Filter Control Systems and Methods", the content of which is incorporated herein by reference.

Technical Field

[0002] This specification generally relates to systems and methods for concentrating fiber suspensions, and more particularly to disc filter control systems and methods for dewatering fiber suspensions such as pulp suspensions in the pulp and paper industry.

Background Art

[0003] Typical disc filters used to dewater cellulose fiber suspensions in the pulp and paper industry generally include a number of disc - shaped filter sections mounted on a rotatable shaft, and the filter sections rotate with the rotor shaft in a tank. The disc - shaped filter sections are partially immersed in the cellulose fiber suspension contained in the tank. Each filter section may include several filter sectors distributed around the rotatable shaft. Each filter sector is provided with an outer filtration lining such as a screen and an internal flow path communicating with the filtrate path of the rotatable shaft.

[0004] As the filter unit rotates with the rotatable shaft, the filter sector moves through the suspension in the tank. As the filter sector moves through the suspension, water is drawn from the suspension through the filtration lining on the filter sector into the flow path within the filter sector, while the fibrous material forms a fibrous mat on the outer surface of the filtration lining. The filtrate containing the water then flows from the flow path within the filter sector into the filtrate channel in the rotor shaft and is discharged from the tank through the filtrate outlet. As the filter unit rotates continuously, the filter sector moves out of the suspension and past a spray nozzle that directs a fluid jet onto the fibrous mat, thereby separating the fibrous mat from the filtration lining. The fibrous material separated from the filtration lining falls into receiving chutes located alongside the filtration lining on both sides of each filter unit that rotates out of the tank after the filter sector has moved through the suspension, i.e., on one side of the rotor shaft where the filter sector moves upward during the rotation of the filter unit. At the bottom of the receiving chute, the fibrous material is received by a conveyor and sent for further processing. [Overview of the project] [Problems that the invention aims to solve]

[0005] Under certain operating conditions, the fiber suspension in the tank of the disc filter can become considerably concentrated, which increases the risk of the filter portion of the disc filter, also referred to herein as the "disk," colliding with the tank due to the large lateral force generated by the concentrated fiber suspension. To prevent disk damage and improve the operation of the disc filter, an improved control system and method are needed to appropriately respond to operating conditions that lead to a considerably concentrated fiber suspension in the tank and control the disc filter. [Means for solving the problem]

[0006] The disk filter control systems disclosed herein may be operable to receive signals from one or more measuring devices corresponding to variables of the disk filter system and to adjust one or more control devices based on the signals received from the measuring devices. The torque applied to the drive unit used to rotate the rotor shaft can be used to determine the degree of lateral force acting on the filter unit rotating in the fiber suspension, and therefore to determine the risk of filter unit failure. This disclosure discloses, but does not limit, control operating parameters of a disk filter, such as rotational speed, vacuum pressure, and / or liquid level, at least in part, based on the torque applied to the drive unit used to rotate the rotor shaft of the disk filter.

[0007] This disclosure provides a disc filter system for dewatering a fiber suspension. The disc filter system includes a disc filter and a control unit. The disc filter is a tank, and includes a tank having an inlet located in the wall of the tank and configured to introduce a fiber suspension into the tank. The disc filter further includes a rotor shaft having a rotating shaft axis, and a variable speed drive unit operably connected to the rotor shaft and configured to rotate the rotor shaft about the rotating shaft axis. The disc filter further includes at least one filter section connected to the rotor shaft and rotating together with the rotor shaft about the rotating shaft axis, which may be a disc-shaped filter section. The control system includes at least one processing unit, at least one memory module communicatively connected to the processing unit, and machine-readable and executable instructions stored in the memory module. The control system may be communicatively connected to the variable speed drive unit and a torque measuring device operable to measure the torque applied to the variable speed drive unit. A machine-readable and executable instruction, when executed by the processing unit, may cause the disk filter system to automatically measure the torque applied to the variable drive unit and adjust the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed that is different from the first rotational speed and not zero, based on the torque applied to the variable drive unit. The rotational speed of the rotor shaft may be adjusted using the variable drive unit.

[0008] The disclosure also provides a method for dewatering a fiber suspension. The method may include the steps of introducing a fiber suspension into a disc filter, the disc filter being a tank including an inlet located in the wall of the tank and configured to introduce the fiber suspension into the tank, a rotor shaft including a rotating shaft axis, and at least one filter section connected to the rotor shaft and rotating together with the rotor shaft about the rotating shaft axis. The method may further include the steps of rotating the rotor shaft about the rotating shaft axis, measuring the torque applied to a drive unit used to rotate the rotor shaft about the rotating shaft axis, and adjusting the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed different from the first rotational speed and other than zero, based on the torque applied to a variable speed drive unit.

[0009] Further features and advantages of the disk filters described herein are shown in the following detailed description, which will be in part readily apparent to those skilled in the art from the description or will be evident from carrying out the embodiments described herein, including the following detailed description, claims, and accompanying drawings.

[0010] Both the summary description above and the detailed description below should be understood as intended to describe various embodiments and provide an overview or framework for understanding the essence and characteristics of the claimed subject matter. The accompanying drawings are included for a further understanding of the various embodiments and are incorporated into and form part of this specification. The drawings illustrate the various embodiments described herein and, together with the description of the specification, serve to illustrate the principles and operation of the claimed subject matter.

[0011] For the sake of simplified and schematic representation, the drawings may omit numerous valves, temperature sensors, flow meters, pressure regulators, electronic control units, pumps, etc., that are used in certain processing operations and are known to those skilled in the art. Furthermore, accompanying components that are often included in typical processing operations, such as valves, pipes, pumps, agitators, instrumentation systems, internal tank structures, or other subsystems, may not be shown. Although not shown, these components should be understood to be within the spirit and scope of the disclosed embodiments. Nevertheless, operating elements such as those disclosed herein may be added to the various embodiments disclosed herein.

[0012] Here, various embodiments are described in great detail, and some embodiments are shown in the accompanying drawings. Throughout the drawings, the same reference numerals are used to refer to the same or similar parts whenever possible. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram schematically shows an axial cross-section of a disk filter system according to one or more embodiments described herein. [Figure 2] This is a cross-sectional view along line A-A of the disk filter system of Figure 1 according to one or more embodiments shown and described herein. [Figure 3] This specification schematically illustrates a disk filter system according to one or more embodiments described herein. [Modes for carrying out the invention]

[0014] Embodiments of the disc filter system described herein are described in detail, with examples shown in the accompanying drawings. Throughout the figures, the same reference numerals are used whenever possible to refer to the same or similar parts. One embodiment of the disc filter system 100 is schematically shown in Figure 1, which generally includes a disc filter 1 and a control system 400. The disc filter 1 includes a tank 2, which includes an inlet 3 located in the wall of the tank 2, and the inlet 3 introduces a fiber suspension into the tank 2. The disc filter 1 further includes a rotor shaft 7, which includes a rotating shaft axis 131. A drive unit 10, for example, a variable-speed drive unit, is used to rotate the rotor shaft 7 about the rotating shaft axis 131. At least one filter section 11 may be coupled to the rotor shaft 7 such that at least one filter section 11 rotates together with the rotor shaft 7 about the rotating shaft axis 131. The control system 400 is communicatively coupled to the drive unit 10 and a torque measuring device 414 that is operable to measure the torque applied to the drive unit 10. The control system 400 may be configured to adjust the rotational speed of the rotor shaft 7 from a first rotational speed to a second rotational speed based on the torque applied to the drive unit 10. Various embodiments of the disk filter system and methods for operating it are described herein with particular reference to the accompanying drawings.

[0015] For example, terms used herein to describe directions, such as up, down, right, left, front, back, top, and bottom, are for reference only to the drawings shown and are not intended to imply absolute orientation.

[0016] Unless otherwise explicitly stated, no method described herein is intended to be construed as requiring the steps to be performed in a specific order or that any apparatus to be in a specific orientation. Therefore, if a method claim does not actually describe the order of steps, or a claim for any apparatus does not actually describe the order or orientation of its individual components, or if the claim or specification does not specify that the steps are limited to a particular order or that a particular order or orientation of the components of the apparatus should be specified, no order or orientation should be inferred in any respect. This applies to interpretations based on the absence of any description, including logical matters, grammatical structures or punctuation regarding the sequence of steps, the flow of operations, the order of components, or the orientation of components, and the number or type of embodiments described herein.

[0017] As used herein, indefinite and definite articles in the original English text include plurals unless it is evident from the context otherwise. Therefore, for example, a component with an indefinite article includes a configuration having two or more such components unless it is evident from the context otherwise.

[0018] As used herein, the terms “upstream” and “downstream” refer to the position of a component or unit of the system with respect to the direction of material flow through the system. For example, if material passing through the system encounters a first component before encountering a second component, the first component is considered “upstream” of the second component. If material encounters a second component before encountering a first component, the first component is considered “downstream” of the second component.

[0019] As used herein, the term "consistency" refers to the concentration of solid fibers in a fiber suspension, which is equal to the mass of solid fibers in a given sample volume divided by the total mass of the fiber suspension in that sample volume.

[0020] As used herein, the term "vacuum pressure" refers to the absolute pressure reading when the pressure is lower than atmospheric pressure. According to this definition, vacuum pressure is inversely proportional to the degree of vacuum applied to the disk filter; as vacuum pressure decreases (i.e., as the difference between vacuum pressure and atmospheric pressure increases), the amount of vacuum applied to the disk filter increases. Conversely, as vacuum pressure increases (i.e., as the difference between vacuum pressure and atmospheric pressure decreases), the amount of vacuum applied to the disk filter decreases.

[0021] A disk filter is used to separate cellulose fibers from a suspension of cellulose fibers in a fluid such as water. Examples of disk filters are disclosed in U.S. Patent No. 9,238,188, assigned to Kadant Black Clawson Inc. under the title "Disk Filter," U.S. Patent No. 4,136,028, assigned to Rauma-Rapola Oy under the title "Method for Filtering a Fibrous Material by Means of a Disk Filter as well as a Disk Filter for Performing the Method," and U.S. Patent No. 6,258,282, assigned to Kvaerner Pulping AB under the title "Rotatable Filter System for Filtration of a Flowing Substance." Under certain operating conditions, the fiber suspension can become quite concentrated in the chamber of the disk filter, and the large lateral forces generated by the concentrated fiber suspension in the chamber can cause the filter sections to collide (for example, come into contact with each other). The collision of the filter sections can damage the filter sections. The systems and methods of this disclosure can prevent the accumulation of high-density material in the tank, thereby reducing or preventing damage to the filter section caused by impact. The systems and methods of this disclosure can also improve the operational efficiency of the disk filter under overall processing and mechanical conditions.

[0022] In a typical disk filter operation, a drive unit is used to rotate a rotor shaft on which a filter unit is placed. The filter unit rotates while entering and exiting the fiber suspension of the disk filter. When the filter unit rotates, the filter unit is subjected to the action of lateral forces and shear stresses whose levels change partially based on the consistency of the fiber suspension. As the consistency of the fiber suspension increases, the density and / or viscosity of the fiber suspension increases, whereby a greater lateral force is applied to the filter unit. As the degree of these lateral forces increases, the risk of disk failure also increases. The degree of these lateral forces can be determined using the measurement of the torque applied to the drive unit used to rotate the rotor shaft. Existing disk filter control methods include monitoring the torque applied to the drive unit of the disk filter, and in response to the torque reaching a predetermined high threshold torque, turning off the drive unit to stop the rotor and prevent damage to the filter unit. Therefore, when an increase in the consistency of the fiber suspension is indicated, the existing control method reduces the rotational speed of the rotor shaft and finally stops it (for example, reduces the rotational speed to zero) to protect the filter unit from collisions.

[0023] The inventors of the present subject matter have found that the performance of a disk filter system can be improved by controlling it according to the torque measured by the drive unit used to rotate the rotor shaft. When the rotational speed of the filter unit increases, the fiber material removal rate increases compared to the filtrate removal rate, and the consistency of the fiber suspension decreases. When the rotational speed of the filter unit decreases, the fiber material removal rate decreases compared to the filtrate removal rate, and the consistency of the fiber suspension increases.

[0024] The disk filter system and method of the present disclosure measure the torque applied to a drive unit used to rotate a rotor shaft and adjust the rotational speed of the rotor shaft based on the measured torque. In particular, the disk filter system and method of the present disclosure measure the torque applied to a drive unit used to rotate a rotor shaft and, if the measured torque exceeds a threshold value, increase the rotational speed of the rotor shaft, which can then reduce the density and / or viscosity of the fiber suspension. The reduction in the density and / or viscosity of the fiber suspension can reduce the lateral force applied to the filter section, thereby reducing the risk of disk failure. The disk filter system and method disclosed herein further include additional control methods for reducing the risk of disk failure and improving the operating efficiency of the disk filter. For example, increasing the rotational speed of the filter section, such as via an increase in the rotational speed of the rotor shaft, can increase the fiber material removal rate and the filtrate removal rate, resulting in a decrease in the filling level of the fiber suspension within the disk filter system. When returning the filling level in the tank to a desired level, diluting the fiber suspension supplied to the tank can complement the increased rotational speed of the filter section and further reduce the consistency of the fiber suspension, thereby further reducing the risk of disk failure.

[0025] In an embodiment, the disk filter control system can maintain the torque applied to the drive unit at a torque setpoint by controlling the rotational speed of the rotor shaft. In an embodiment, the disk filter control system can maintain the torque applied to the drive unit at a torque setpoint by implementing a proportional integral derivative (PID) control scheme to control the rotational speed of the rotor shaft. Similarly, in an embodiment, the disk filter control system can maintain the filling level in the tank at a setpoint level by implementing a PID control scheme to control the flow rate of the fiber suspension entering the tank and / or the flow rate of the diluent entering the fiber suspension before the fiber suspension is introduced into the tank.

[0026] In an embodiment, the disk filter control system and method may include the steps of determining whether the vacuum pressure applied to the filter section is higher than a high threshold vacuum pressure even after increasing the speed of the rotor shaft for a certain period of time, and if so, stopping the disk filter to prevent disk failure.

[0027] An embodiment of a disk filter system is disclosed, in which the rotational speed of the disk filter is adjusted as a function of the torque applied to the drive unit used to rotate the disk filter. The disk filter system of this disclosure includes a disk filter and a control system for controlling the operation of the disk filter.

[0028] Referring to Figures 1 and 3, the disk filter system 100 may include a disk filter 1 and a control system 400 that is communicatively connected to the disk filter 1. Referring to Figures 1 and 2, the disk filter 1 may include, but is not limited to, a tank 2 having an inlet 3 for introducing a fiber suspension, such as a cellulose fiber suspension, into the tank 2. The inlet 3 is connected to a conduit 4, and the fiber suspension is supplied to the inlet 3 through the conduit 4 (e.g., by a primary pump 120 shown in Figure 3). The tank 2 may include a lower section 2a and an upper section 2b connected to the lower section 2a. The lower section 2a generally has a U-shaped structure and may be closed at its uppermost part by the upper section 2b, which can form a hood that covers the lower section. The lower section 2a and the upper section 2b of the tank 2 together generally define the internal space of the tank.

[0029] In this embodiment, the inlet 3 of the tank 2 includes a plurality of inlet openings (not shown in Figures 1 and 2) located in a part of the tank 2, and the filter unit 11 rotates downward from a position above the fiber suspension into the fiber suspension in the tank while the rotor unit 6 is rotating. The plurality of inlet openings may be configured to introduce the fiber suspension into the space 36 between the receiving chute units 30. The inlet 3 and its inlet openings may be configured to introduce the fiber suspension flow into the tank 2 in a direction consistent with the rotation direction of the filter unit 11.

[0030] As shown in Figure 2, the internal space of the tank 2 may be accessible through a hatch 5 at the top 2b of the tank. As shown in Figure 1, the filling level sensor 412 may be connected to the tank 2 and operable to measure the filling level of the fiber suspension in the tank 2. In embodiments, the filling level sensor 412 may be, but is not limited to, a radar sensor, a capacitance sensor, a tuning fork sensor, a diaphragm sensor, a float level sensor, an ultrasonic sensor, an infrared sensor, a nuclear sensor, or a combination thereof. The control system 400 may be communicatively connected to the filling level sensor 412 and configured to receive a filling level signal from the filling level sensor 412.

[0031] The disc filter further includes a rotor section 6 disposed within the internal space of the tank 2. The rotor section 6 includes a rotor shaft 7 that is rotatably mounted in the tank 2 and extends across the internal space of the tank. In embodiments, the rotor shaft 7 may be rotatably mounted in the lower part 2a of the tank through a first bearing 8a arranged at a first end of the rotor shaft and a second bearing 8b arranged at the other end of the rotor shaft 7. The rotor shaft 7 may be rotated by a drive unit 10, for example in the form of a drive motor, which extends through sealed openings in the inclined side walls 9a and 9b of the tank 2 and can be operably connected to the rotor shaft 7. In the embodiment shown in Figure 2, the rotation direction D of the rotor shaft 7 is clockwise, but in embodiments, it should be understood that the rotation direction of the rotor shaft may be counterclockwise. The drive unit 10 may be an electric motor, a hydraulic motor, or other type of drive unit capable of rotating the rotor shaft 7. In an embodiment, the drive unit 10 can rotate the rotor shaft 7 and control the rotational speed of the rotor shaft 7. In an embodiment, the drive unit 10 may be a variable speed drive unit (VSD) that includes both a device such as an electric motor or hydraulic motor that rotates the rotor shaft 7 and a variable frequency control unit that performs pulse wave modulation, or a device that controls power to the device used to rotate the rotor shaft 7, such as a variable speed transmission or other mechanical link structure. The torque measuring device 414 may be connected to the drive unit 10 and be operable to measure the torque applied to the drive unit 10. The control system 400 may be connected to the torque measuring device 414 in a communicative manner and configured to receive torque signals from the torque measuring device 414.

[0032] In embodiments, the drive unit 10 is an electric drive unit, and the torque measuring device 414 may include an ammeter that is operable to measure the current load applied to the drive unit 10 in combination with a rotor shaft speed sensor that measures the rotational speed of the rotor shaft 7. If the efficiency of the drive unit 10 is known, the torque applied to the drive unit 10 can be determined by combining the speed and amperage. In embodiments, the torque applied to the drive unit 10 can also be measured directly, for example, using a rotational torque sensor and strain gauges. Any other existing or future-developed torque sensors or measuring devices are also suitable for the torque measuring device 414 and are intended in this disclosure.

[0033] As the consistency of the fiber suspension in tank 2 increases, the torque applied to the filter section 11 of the rotor section 6 may increase due to the increase in the density and / or viscosity of the fiber suspension. The increase in torque increases the current demand from the drive unit 10 to maintain the rotation of the rotor section 6 at a predetermined rotational speed. Therefore, measuring the rotational speed and the current used by the drive unit 10 indicates the torque applied to the rotor section 6, which may correlate with the consistency of the fiber suspension in tank 2. In embodiments, the drive unit 10 is a hydraulic motor, and the torque measuring device 414 may also be a device that can operate to determine torque by measuring one or more operating conditions of the hydraulic motor, such as hydraulic pressure and speed, but is not limited to these.

[0034] The control system 400 may be configured to be communicatively connected to the drive unit 10 and to adjust the rotational speed of the rotor shaft 7. In embodiments where the drive unit 10 is a VSD, the control system 400 may be configured to transmit speed control signals used by the VSD to the VSD to control the power supplied to the VSD's device used to rotate the rotor shaft 7. As described in more detail herein, the control system 400 may control the rotational speed of the rotor shaft 7 based on one or more signals received from one or more sensors of the disk filter system 100.

[0035] Referring again to Figures 1 and 2, the rotor section 6 also includes at least one filter section 11 supported by the rotor shaft 7 to rotate with the rotor shaft 7 while being partially immersed in the fiber suspension received in the tank 2. As shown in Figure 1, the rotor section 6 may be provided with four such filter sections 11. However, it should be understood that the disc filter 1 may contain fewer than four filter sections, or conversely, more than four filter sections. In embodiments, each filter section 11 may be perpendicular to the longitudinal axis of the rotor shaft 7. The longitudinal axis coincides with the rotational shaft axis 131 of the rotor shaft 7 (as shown in Figure 3). Each filter section 11 extends in an annular configuration radially outward from the rotor shaft 7. Each filter section 11 may be divided into several filter sectors 12 distributed around the rotor shaft 7. The filter sectors 12 of individual filter sections 11 may be separated from each other by radially oriented partitions extending between the opposing transverse surfaces of the filter section 11. As illustrated, the filter sector 12 may be separated by radially oriented partitions. However, it should be understood that the partitions may be positioned in various locations other than radially, depending on cost factors and other desirable structurally equivalent orientations. As illustrated, each filter section 11 is provided with an outer filtration lining 13 on opposing lateral surfaces (shown as a dotted pattern in Figure 2), and an internal flow path (not shown) that communicates with the filtrate passage 14 in the rotor shaft 7 and transports the filtrate that has passed through the filtration lining 13 to the filtrate passage 14. It should be noted that various equivalent filtration lining arrangements may be used in addition to the outer arrangement shown in the drawings.

[0036] Referring again to Figure 2, each individual filter sector 12 may include a conduit section 15 for transporting the filtrate, i.e., the liquid filtered from the fibrous suspension in the tank 2, from the filter sector 12 to the associated filtrate passage 14 of the rotor shaft 7, through an opening provided in the cylindrical surface of the rotor shaft 7 between the conduit section 15 and the filtrate passage 14.

[0037] The filtrate passages 14 may extend axially along the rotor shaft 7. These filtrate passages 14 may be formed as fan-shaped spaces separated from each other by radially oriented partitions extending along the rotor shaft 7. The filtrate passages 14 may be defined radially inward by a tubular core 17 of the rotor shaft 7. The tubular core 17 has a diameter that varies along the length of the rotor shaft 7, with the smallest diameter at the end of the tubular core located at its end on the rotor shaft 7, where the filtrate exits the rotor shaft 7 axially. In the illustrated example, two outlets are provided for the filtrate. A first outlet 20 may be intended for prefiltrate (opaque filtrate), and the other outlet 21 may be intended for clear filtrate. At least the clear filtrate outlet 21 is connected to a descending pipe 24 intended to establish a vacuum at the suction head 22, and furthermore, the prefiltrate outlet 20 may also be connected to the descending pipe 24. The suction head 22 can communicate with the filtrate passage 14 of the rotor shaft 7 through the filtrate valve 23. As the rotor shaft 7 rotates relative to the filtrate valve 23 and the suction head 22, the filtrate valve 23 can connect each filtrate passage 14 to either the front filtrate outlet 20 or the clear filtrate outlet 21, depending on the predetermined rotational position of the rotor shaft 7.

[0038] The pressure sensor 416 may be operable to fluidly communicate with the filter section 11 and measure the vacuum pressure of the filter section 11. For example, the pressure sensor 416 may be provided on the suction head 22, and the vacuum pressure sensed by the pressure sensor 416 may indicate the vacuum pressure of the filter section 11. The control system 400 may be configured to communicate with the pressure sensor 416 and receive the vacuum pressure signal from the pressure sensor 416. If the vacuum pressure signal indicates that the vacuum pressure of the filter section 11 is too high (i.e., indicates a lower vacuum), the disk filter 1 is not operating normally and may take further action to reduce or prevent damage to the filter section 11. For example, if the fibrous material in the fiber suspension does not accumulate on the outer filtration lining 13 of the filter section 11, the rate at which the liquid filtrate is removed from the fiber suspension increases compared to the rate at which the fibrous material is removed. This can increase the consistency in the fiber suspension, thereby increasing the density and / or viscosity of the fiber suspension. As the density and / or viscosity of the fiber suspension increases, a large shear force may be applied to the filter section 11 as it rotates through the concentrated fiber suspension. Therefore, as described in more detail herein, by incorporating a pressure sensor 416 into the suction head 22 and further monitoring the vacuum pressure in the suction head 22 via the pressure sensor 416 using the control system 400, it is possible to indicate problematic operating conditions that may occur before a system failure (e.g., damage or destruction of the filter section 11) occurs.

[0039] Referring again to Figure 2, the disc filter 1 further includes at least one second injection section 110 extending through the wall of the tank 2. At least one second injection section 110 can be used to introduce a second flow of fiber suspension into the tank 2, facilitating dilution, agitation, and mixing of the fiber suspension within the tank, thereby reducing the concentration of the fiber suspension and improving the efficiency of the disc filter 1. The second injection section may be positioned to help mitigate the concentration in areas of the tank 2 where the fiber suspension tends to concentrate most. The design and operation of the second injection section of the disc filter system are disclosed in U.S. Patent Application Publication No. 2021 / 0291087, which is incorporated herein by reference in its entirety. As shown in Figure 2, the secondary conduit 19 may be connected to the conduit 4. The secondary conduit 19 can receive the fiber suspension injected into the tank 2 through at least one second flow injection section 110. In Figure 2, any valves and flow meters along the secondary conduit 19 are not shown. While we do not wish to be bound by theory, the use of the second injection section 110 can complement the advantages provided by torque-based control of the rotational speed of the rotor shaft 7, as using both can accommodate operating conditions that would lead to a substantially thicker fiber suspension in the tank, thereby preventing disk damage and improving the operation of the disk filter.

[0040] Referring again to Figure 1, the disc filter 1 may also include release members 25 for removing the fibrous material that has been filtered from the fibrous suspension in the tank 2 and formed as a fibrous mat on the filtration lining 13 of each filter section 11. In an embodiment, the release members 25 may be spray nozzles configured to release the fibrous material formed on the filtration lining 13 of the filter section 11 from one filter sector 12 at a time in succession as the filter sector 12 of the filter section rotates past the release members 25. The release members 25 are arranged on opposing sides of each filter section 11 and may emit a jet of water or any other suitable fluid from these release members 25.

[0041] The disc filter 1 may also include a cleaning member 26 for cleaning the filtration lining 13 of each filter section 11 with a flushing fluid emitted from the cleaning member 26. In embodiments, the cleaning member 26 may be spray nozzles arranged on opposing sides of each filter section 11. The cleaning member 26 may be configured to emit a spray of water or any other suitable flushing fluid toward the filtration lining 13 on opposing sides of each filter section 11. To allow the cleaning member 26 to sweep the filtration lining 13 of each filter section 11 while the rotor section 6 is rotating, the cleaning member 26 may be appropriately mounted on a pivotable carrier 27 configured to pivot back and forth. The carrier 27 may be pivoted by a drive unit 29, for example, in the form of a drive motor. A release member 25 may be connected to the pivotable carrier 27 to pivot the release member 25 together with the cleaning member 26. Alternatively, in embodiments, the release member 25 may be stationary. In one embodiment, the cleaning member 26 may be located behind the release member 25 with respect to the rotational direction of the filter section 11. In such an embodiment, during rotation of the filter section 11, each filter sector 12 of the filter section 11 rotates past the release member 25 and then past the cleaning member 26.

[0042] The disc filter 1 may include a plurality of receiving chute sections 30. Each receiving chute section 30 may include an inlet opening 38 at its upper end for receiving the fiber mat that has come off the filtration lining 13 of an adjacent filter section 11. Each filter section 11 has a first receiving chute section 30 located beside a portion of the filtration lining 13 on the first side of the filter section 11, and another receiving chute section 30 located beside a portion of the filtration lining 13 on the opposite side of the filter section 11. One receiving chute section 30 may be located in the space between each pair of adjacent filter sections 11, and in the space between each outermost filter section 11 on the rotor shaft 7 and adjacent inclined side walls of the tank 2. In an embodiment, the receiving chute section 30 may be located in a part of the tank 2 where the filter sector 12 rotates as the rotor section 6 rotates, descending from a position above the fiber suspension and entering the fiber suspension, such as on one side of the rotor shaft 7 where the filter sector 12 rotates downward after the fiber mat has been removed and cleaned by the cleaning member 26. In other words, the receiving chute section 30 is located on one side of the tank 2, and the main component of the angular velocity of the filter section 11 is in the vertical downward direction.

[0043] However, in an alternative embodiment (not shown), the receiving chute 30 may be located on one side of the rotor shaft 7 where the filter sector 12 rotates upward as the rotor 6 rotates, so as to be released from a position below the fiber suspension into the tank 2. In other words, in the alternative embodiment, the receiving chute 30 is located on one side of the tank 2, and the principal component of the angular velocity of the filter 11 is vertically upward. The inlet opening 38 at the upper end of each receiving chute 30 is located above the horizontal plane extending through the longitudinal axis of the rotor shaft 7, and the lateral edge of the inlet opening 38 extends near the filtration lining 13 of the adjacent filter 11 to efficiently capture the fiber mat that has come off the filter sector 12 of those filter 11. As shown in Figure 1, the lateral wall of each receiving chute 30 may branch at the top of the receiving chute 30 near the inlet opening 38 of the receiving chute 30. The inlet opening 38 can receive the fiber mat that has come off the filtration lining 13 of the adjacent filter section 11, along with the flushing liquid from the cleaning member 26. Furthermore, as shown in Figure 2, each receiving chute section 30 has a portion 31 at its upper end that curves inward within the region above the rotor shaft 7, and the inlet opening 38 of the receiving chute section 30 can extend into this region.

[0044] The release member 25 and the cleaning member 26 are located above the receiving chute 30 on one side of the rotor shaft 7, and the filter sector 12 rotates downward toward the water surface of the fiber suspension in the tank 2. The cleaning member 26 may be configured to allow the fiber mats removed by the release member 25 to flow into the receiving chute 30 with a flushing liquid emitted from the cleaning member 26. The receiving chute 30 may be configured to receive the fiber mats along with the flushing liquid from the cleaning member 26, thereby allowing the fiber mats to be diluted to a desired consistency in the receiving chute 30 by this flushing liquid. At the lower end 32, each receiving chute 30 is connected to a transport unit 33 which may be configured to pick up the fiber mats that have fallen through the receiving chute 30 and send the fiber mats to an outlet 34 (see Figure 1), from which the fiber mats can be sent for further processing. In the illustrated example, the conveying unit 33 is a screw conveying unit that extends parallel to the rotor shaft 7 and can be rotated by a drive unit 35, for example, in the form of a drive motor.

[0045] During the operation of the disc filter 1, the fiber suspension is introduced into the tank 2 through the inlet 3. Before being introduced into the tank 2, the fiber suspension is mixed with a diluent to adjust the consistency of the fiber suspension, which then adjusts the consistency of the fiber suspension in the tank 2 when it is introduced. As previously mentioned, the drive unit 10 rotates the rotor unit 6, which in turn rotates the filter unit 11 mounted on the rotor shaft 7 of the rotor unit 6. As the filter unit 11 rotates, the filter sector 12 is immersed in the fiber suspension in the tank 2 in the space 36 between the receiving chute units 30, and then moves through the fiber suspension to the opposite side of the rotor shaft 7, where the filter sector 12 rotates upward and exits the fiber suspension. As the filter sector 12 moves through the fiber suspension, liquid is drawn up from the fiber suspension through the filtration lining 13 on the filter sector 12 into the inner flow path of the filter sector 12, while the fibrous material is formed as a fiber mat on the outer surface of the filtration lining 13. The filtrate containing the liquid then flows from the flow path through the conduit section 15 into the filtrate passage 14 in the rotor shaft 7, and is discharged from the tank 2 through the suction head 22 and either the pre-filtrate outlet 20 or the clear filtrate outlet 21.

[0046] As the filter sector 12 rotates upward and exits the fiber suspension, continuous suction through the filtrate passage 14 of the rotor shaft 7 and the flow path of the filter sector 12 generates an airflow that passes through the fibrous material deposited on the filtration lining 13 of the filter sector 12 and then through the flow path back into the filtrate passage 14. The fibrous material deposited on the filtration lining 13 can be dried by this airflow. After the filter sector 12 has rotated past a vertically upward-facing corner position, it may continue to rotate past a release member 25 that removes the fiber mat from the filtration lining 13 of the filter sector 12 by a fluid jet directed toward the opposing lateral surfaces of each filter sector 12. As the rotor 6 continues to rotate, the filter sector 12 may then rotate past a cleaning member 26 that cleans the filtration lining 13 of the filter sector 12 with a flushing fluid jet directed toward the opposing lateral surfaces of each filter sector 12. The fiber mat, detached from the filtration lining 13 of the filter sector 12, falls into the receiving chute 30 along with the flushing liquid from the cleaning member 26. At the bottom of the receiving chute 30, the fiber mat can be picked up by the conveying unit 33 and sent for further processing. After rotating past the cleaning member 26 and the upper end of the receiving chute 30, the filter sector 12 rotates downward again into the fiber suspension to continuously filter the fiber suspension.

[0047] Referring here to Figure 3, the disc filter system 100 includes a fiber suspension source 200 (e.g., a storage tank) containing the input fiber suspension and connected to a primary pump 120, the primary pump 120 may be operable to flow the input fiber suspension from the fiber suspension source 200 through conduits 4 to the inlet 3 of the disc filter 1. In embodiments of the disc filter system 100 including at least one second injection section 110, a secondary conduit 19 may be connected to conduits 4 such that the primary pump 120 is also operable to flow the input fiber suspension from the fiber suspension source 200 to at least one second flow injection section 110. Thus, the characteristics of the fiber suspension delivered to the inlet 3 may be the same as those of the fiber suspension delivered to at least one second injection section 110, if there is at least one second injection section 110. As will be further detailed herein, the fiber suspension introduced into the tank 2 via the inlet 3 may include a mixture of the input fiber suspension supplied from a fiber suspension tank and a diluent. In an embodiment, as shown in Figure 3, a primary supply valve 122 is positioned between the primary pump 120 and the inlet 3 to regulate the flow rate and pressure of the fiber suspension to the inlet 3. In an embodiment, the disk filter system 100 may include a primary supply flow meter 124 positioned between the primary pump 120 and the inlet 3. The primary supply flow meter 124 can be used to monitor the flow rate and / or pressure of the fiber suspension supplied to the inlet 3 by the primary pump 120.

[0048] Unexpectedly, it was found that by providing the liquid of the second flow into tank 2 so that the second flow contacts the rotor shaft 7, sufficient agitation and mixing occurs in the tank facing the inlet 3, further reducing or mitigating the concentration of the fiber suspension in the tank. In particular, when the liquid of the second flow (shown as the main flow vector 111 in Figure 3) contacts the rotor shaft 7, the second flow changes direction and scatters in multiple directions (i.e., vertically and in directions between vertical and horizontal). This change in direction and scattering of the second flow by the rotor shaft 7 agitates and mixes the fiber suspension present in tank 2, aiding both the dilution of the suspension present in tank 2 and a more uniform mixing of the filtrate and fibers, thereby reducing or mitigating concentration and consequently achieving the effect of mechanically discarding the filter mat film formed on the filter section 11. Advantageously, it was found that the agitation and mixing by the liquid of the second flow directed towards the rotor shaft 7 does not interrupt the film formation of the fiber mat on the filter section 11.

[0049] Continuing with reference to Figure 3, in some embodiments, the secondary conduit 19 can deliver the fiber suspension from the conduit 4 to the supply manifold 108. Each of at least one second injection section 110 may be connected to the supply manifold through an injection section valve 112. If an injection section valve 112 is included, it can be used to adjust and regulate the flow rate and pressure of the liquid entering and passing through each injection section from the supply manifold 108. For example, the flow rate and pressure of the liquid entering and passing through each injection section 110 can be individually adjusted using the injection section valve 112. Thus, in some embodiments, it should be understood that the flow rate and / or pressure of the liquid passing through each injection section 110 can be individually adjusted. In some embodiments, the injection valve 112 may be operated manually, while in other embodiments, the injection valve 112 may be operated electrically or pneumatically and remotely by a control system 400 or the like which is communicatively connected to the injection valve 112 (communication connection between the injection valve 112 and the control system 400, not shown in Figure 3). In such embodiments, both the primary pump 180 and the control system 400 are communicatively connected to remotely control and / or adjust the flow rate and pressure of the liquid entering and passing through the injection section 110.

[0050] In some embodiments, each injection section 110 may be connected to a supply manifold 108 by an injection section flow meter 114. In an embodiment where the injection section 110 is connected to the supply manifold 108 by an injection section valve 112, the injection section flow meter 114 is positioned between the injection section valve 112 and the injection section 110, as shown in Figure 3. The injection section flow meter 114 can be used to monitor the flow rate and / or pressure of the fluid from the supply manifold 108 to the injection section 110. The injection section flow meter 114 is communicatively connected to a control system 400 (communication connection between the injection section flow meter 114 and the control system 400, not shown in Figure 3), thereby enabling automatic monitoring of the flow rate and / or pressure of the liquid entering and passing through the injection section 110. In some of these embodiments, such as embodiments that include both an injection section flow meter 114 and / or an injection section valve 112, the control system 400 may use the injection section flow meter 114 together with the injection section valve 112 and / or a primary pump 120 to facilitate feedback control of the flow rate and pressure of the liquid passing through the injection section 110.

[0051] In one embodiment, as shown in Figure 3, a secondary conduit supply valve 142 is positioned between the supply manifold 8 and the connection point between the conduit 4 and the secondary conduit 19 to regulate the flow rate and pressure of the fiber suspension to the second injection section 110. In another embodiment, the disk filter system 100 may include a secondary conduit flow meter 144 between the supply manifold 8 and the connection point between the conduit 4 and the secondary conduit 19. The secondary conduit flow meter 144 can be used to monitor the flow rate and / or pressure of the fiber suspension supplied to the second injection section 110 via the supply manifold 108.

[0052] In an embodiment, the secondary conduit 19 can directly deliver the fiber suspension from the conduit 4 to at least one second injection section 110. In an embodiment, the supply manifold 108, injection section valve 112, injection section flow meter 114, secondary conduit supply valve 142, and secondary conduit flow meter 144 can be omitted from the disk filter system 100 individually or in any combination.

[0053] The disc filter system 100 also includes a diluent source 300 (e.g., a storage tank, a water treatment section, etc.) containing a diluent, which may be connected to a secondary pump 130 that can be operated to pump the diluent from the diluent source 300 through a diluent conduit 301 into a conduit 4. In this way, the input fiber suspension pumped from the fiber suspension source 200 is diluted, i.e., its consistency may be reduced, before the fiber suspension is supplied to the disc filter 1 through the inlet 3. In an embodiment, the diluent conduit 301 carrying the diluent may intersect with the conduit 4, so that the diluent is mixed with the input fiber suspension flow through the conduit 4. In an embodiment, the diluent and the input fiber suspension may be mixed in the conduit 4 and tank 2 to produce a uniform fiber suspension. In an embodiment, the diluent and the input fiber suspension may also be mixed in another system element, such as a mixing tank or other system element located upstream of tank 2 and capable of achieving the desired dilution of the fiber suspension flowing into the disc filter through the inlet 3.

[0054] In an embodiment, the dilution control valve 132 may be located in the dilution conduit 301 between the secondary pump 130 and the intersection of the dilution conduit 301 and conduit 4. The dilution control valve 132 may be operable to adjust the flow rate and pressure of the diluent to conduit 4. In an embodiment, the disk filter system 100 may include the secondary pump 130 and a diluent flow meter 134 located in the dilution conduit 301 between the intersection of the dilution conduit 301 and conduit 4. The diluent flow meter 134 may be operable to monitor the flow rate and / or pressure of the diluent supplied to conduit 4 by the secondary pump 130.

[0055] In embodiments, the primary supply valve 122, the dilution control valve 132, or both thereof may be manually operated valves. In embodiments, the primary supply valve 122, the dilution control valve 132, or both thereof may be electrically or pneumatically operated control valves. The primary supply valve 122, the dilution control valve 132, or both thereof may be communicatively connected to the control system 400. In embodiments, the primary pump 120, the diluent pump 130, or both thereof may be communicatively connected to the control system 400 so that the flow rate and / or pressure of the fiber suspension (in both diluted and undiluted states) to the inlet 3 and / or the diluent to the conduit 4 may be controlled and / or regulated by the control system 400, respectively. The primary supply flow meter 124, the diluent flow meter 134, or both thereof, are communicatively connected to the control system 400, thereby enabling automatic monitoring of the flow rate of the fiber suspension to the inlet 3 and / or the diluent to the conduit 4, and / or the pressure, respectively. In an embodiment, the control system 400 can transmit control signals to one or more of the primary supply valve 122, the dilution control valve 132, the primary pump 120, the diluent pump 130, or a combination thereof, and can also receive signals from the primary supply flow meter 124 and the diluent flow meter 134, or both thereof, to facilitate feedback control of the flow rate of the fiber suspension to the inlet 3 and the diluent to the conduit 4.

[0056] Referring again to Figure 3, the control system 400 may include at least one processing unit 402, at least one memory module 404 communicatively connected to the processing unit 402, and machine-readable and executable instructions 406 stored in the memory module 404. When executed by the processing unit 402, the machine-readable and executable instructions 406 can cause the disk filter system 100 to automatically perform any of the steps described herein. The control system 400 may be communicatively connected to the disk filter system 100 by being communicatively connected to one or more of the following: the drive unit 10, the primary pump 120, the secondary pump 130, the primary supply valve 122, the dilution control valve 132, the secondary conduit supply valve 142, the injection valve 112, the primary supply flow meter 124, the diluent flow meter 134, the secondary conduit flow meter 144, the injection flow meter 114, the filling level sensor 412, the torque measuring device 414, and the pressure sensor 416, or a combination thereof. The control system 400 can be communicated with one or more other sensors or control devices related to the operation of the disk filter.

[0057] Herein, the control strategies for the operation of the disk filter system 100 are described in more detail. For clarity, each control strategy is described individually, but any measuring device and control strategy can be combined with any other measuring device and control strategy to control the disk filter system 100 in response to changes in the operation of the disk filter 1. Furthermore, any control strategy described herein can be implemented through the control system 400 using machine-readable and executable instructions 406 stored in at least one memory module 404 of the control system 400 and executed by the processing unit 402 of the control system 400.

[0058] Referring to Figure 3, when executed by the processing unit 402, the machine-readable and executable instruction 406 can cause the disk filter system 100 to automatically measure the torque applied to the drive unit 10 and, further, adjust the rotational speed of the rotor shaft 7 via the drive unit from a first rotational speed to a second rotational speed that is different from the first rotational speed and greater than zero, based on the torque applied to the drive unit. When measuring the torque applied to the drive unit 10, the control system 400 may receive a torque signal corresponding to the torque applied to the drive unit 10 from the torque measuring device 414. The first and second rotational speeds may be non-zero. In one embodiment, the second rotational speed is faster than the first rotational speed, and the rotational speed of the filter unit 11 increases based on the torque measured by the drive unit 10. In another embodiment, the second rotational speed is slower than the first rotational speed, and the rotational speed of the filter unit 11 decreases based on the torque measured by the drive unit 10. In this embodiment, the rotational speed may increase in response to an increase in torque and decrease in response to a decrease in torque.

[0059] In the embodiment, when executed by the processing unit 402, the machine-readable and executable instruction 406 can further cause the disk filter system 100 to automatically determine whether the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10. If the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10, the disk filter system 100 can increase the rotational speed of the rotor shaft 7 via the drive unit 10 from a first rotational speed to a second rotational speed that is faster than the first rotational speed. In the embodiment, the high threshold torque applied to the drive unit 10 is a torque of 95% or less of the maximum torque, 90% or less of the maximum torque, 80% or less of the maximum torque, 70% or less of the maximum torque, 60% or less of the maximum torque, or 50% or less of the maximum torque, and the maximum torque may be a torque greater than that which, when greater, would cause the torque to continue to increase rapidly without intervention, leading to damage to the filter unit 11. The maximum torque may depend, at least in part, on the physical properties of the fiber suspension and the operating state of the disk filter. The maximum torque may be the highest torque that the drive unit 10 can operate under its specifications. In embodiments, the high threshold torque applied to the drive unit 10 may be 50% or more and 95% or less of the maximum torque, 60% or more and 95% or less of the maximum torque, 70% or more and 95% or less of the maximum torque, 80% or more and 95% or less of the maximum torque, 90% or more and 95% or less of the maximum torque, or 95% or more and 99% or less of the maximum torque.

[0060] As described above, in the embodiment, the control system 400 can maintain the torque applied to the drive unit 10 at a torque setpoint by implementing a PID control scheme to control the rotational speed of the rotor shaft 7. In the embodiment, the torque setpoint may depend on the state of the fiber suspension in the tank 2 of the disc filter. In the embodiment, the high threshold torque applied to the drive unit 10 may be a torque of 105% or more of the torque setpoint and 95% or less of the maximum torque, 110% or more of the torque setpoint and 95% or less of the maximum torque, 120% or more of the torque setpoint and 95% or less of the maximum torque, 130% or more of the torque setpoint and 95% or less of the maximum torque, 140% or more of the torque setpoint and 95% or less of the maximum torque, or 150% or more of the torque setpoint and 95% or less of the maximum torque. By operating the disc filter system 100 with a constant motor torque, it may be possible to detect an increase in friction applied to the filter unit 11 and / or prevent an increase in friction applied to the filter unit 11. By varying the rotational speed of the filter section 11 and maintaining a constant motor torque, the control system 400 can reduce or prevent lateral forces (i.e., axial forces relative to the central axis of the rotor shaft). By selecting a torque setting value, these large axial forces caused by excessively high consistency of the fiber suspension in the tank 2 can be reduced or prevented.

[0061] We have found that the performance of the disc filter system 100 can be improved by increasing the rotational speed of the filter unit 11 when the fiber suspension has increased consistency. In particular, we have found that increasing the rotational speed of the filter unit 11 can increase the fiber material removal rate compared to the filtrate removal rate. Therefore, increasing the rotational speed of the filter unit 11 can decrease the consistency of the fiber suspension in the tank 2. Such a control strategy is counterintuitive, for example, because it might suggest that the increase in torque applied to the drive unit 10 due to the increase in the consistency of the fiber suspension should be reduced to prevent excessive shear force applied to the filter unit 11 that could cause damage to the filter unit 11. In other words, it might be expected that the drive unit used to rotate the rotor of the disc filter should be stopped when a predetermined torque level is reached. However, in the control method of the present invention, the control system 400 can increase the rotational speed of the rotor shaft 7 of the disc filter 1 in accordance with the arrival of a predetermined torque level. In an embodiment in which the control system 400 performs PID control to control the rotational speed of the rotor shaft 7 and maintains the torque applied to the drive unit 10 at a torque set value, the magnitude of the increase in the rotational speed of the rotor shaft 7 may correspond to the PID adjustment parameters set to achieve the desired control behavior.

[0062] In embodiments such as those implementing PID control, the rotational speed of the rotor shaft 7 can be continuously adjusted by the control system 400 based on the torque applied to the drive unit 10 and other measured variables of the disc filter system 100 (as described later). By continuously adjusting the rotational speed of the rotor shaft 7, the disc filter system 100 can protect the filter unit 11 from contact with other components in the tank 2, such as the side walls of the receiving chute unit 30 or the inlet flow path 40, while also achieving high energy efficiency in the separation process. Furthermore, it should be understood that additional control variables, such as those listed below, can also be continuously adjusted based on the torque applied to the drive unit 10 and other measured variables of the disc filter system 100.

[0063] In an embodiment, the control system 400 may be configured to monitor the filling level in the tank 2 and increase or decrease the flow rate of the diluent into the conduit 4, the flow rate of the fiber suspension into the tank 2, the flow rate of the fiber suspension into the second injection section 110, or any combination thereof, based on the filling level. In an embodiment, the control system 400 may maintain the filling level in the tank 2 at a set filling level by implementing a PID control scheme to control the flow rate of the diluent into the conduit 4, the flow rate of the fiber suspension into the tank 2, the flow rate of the fiber suspension into the second injection section 110, or any combination thereof.

[0064] In an embodiment, the control system 400 may be configured to control the operation of the disc filter in accordance with the torque applied to the drive unit 10 and the level of fiber suspension filling in the tank 2. As the rotational speed of the rotor shaft 7 increases, the speed at which the fiber material and filtrate exit the disc filter 1 also increases, which can decrease the level of fiber suspension filling in the tank 2. If the level of fiber suspension in the tank 2 falls below a low-level setting, a portion of the filter sector 12 may be exposed at a rotational position where it would normally be immersed in the fiber suspension, which can reduce the dewatering efficiency of the fiber suspension in the disc filter 1. In addition to reducing the consistency of the fiber suspension in the tank 2 by increasing the rotational speed of the rotor shaft 7, the consistency of the fiber suspension can be further reduced by diluting the fiber suspension introduced into the tank 2 through the inlet 3.

[0065] In an embodiment, if the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10, the machine-readable and executable command 406, when executed by the processing unit 402, may increase the rotational speed of the rotor and cause the disk filter system 100 to automatically measure the filling level of the fiber suspension in the tank 2 and determine whether the filling level of the fiber suspension in the tank 2 is lower than the low level setting value for the fiber suspension in the tank 2. When measuring the filling level of the fiber suspension in the tank 2, the control system 400 may receive a filling level signal corresponding to the filling level of the fiber suspension in the tank 2 from the filling level sensor 412. In an embodiment, if the filling level of the fiber suspension in the tank 2 is lower than the low level setting value, the control system 400 may cause the disk filter system 100 to increase the filling level of the fiber suspension in the tank 2 by increasing the flow rate of the diluent into the conduit 4, the flow rate of the fiber suspension introduced into the tank 2, or both. In embodiments, if the filling level of the fiber suspension is lower than the low-level setting for the fiber suspension, the disc filter system 100 may dilute the fiber suspension in the tank 2. In embodiments, the disc filter system 100 may dilute the fiber suspension at a position upstream of the inlet 3. In embodiments, the low-level setting for the fiber suspension in the tank 2 may be determined to improve the operation of the disc filter. It has been found that lower low-level settings tend to produce lower vacuum (e.g., higher absolute pressure), thereby reducing the filtrate extraction rate and the rate at which the disc filter system 100 can separate the fibrous material from the filtrate of the fiber suspension. In embodiments, the low-level setting may be determined based on the state of the fiber suspension and / or the operating state of the disc filter system 100.

[0066] In one embodiment, when the rotational speed of the rotor shaft 7 is increased in accordance with reaching a predetermined torque level, the machine-readable and executable instruction 406, when executed by the processing unit 402, may further cause the disk filter system 100 to automatically monitor the torque level and determine whether the torque level remains above a high threshold torque value despite the increase in the rotational speed of the rotor shaft 7. If the torque remains above a high threshold torque level, the control system 400 may cause the disk filter system 100 to increase the flow rate of the diluent into the conduit 4. In such an embodiment, both the increase in the rotational speed of the rotor shaft 7 and the increase in the flow rate of the diluent into the conduit may act to reduce the consistency of the fiber suspension in the disk filter 1.

[0067] In one embodiment, the control system 400 can dilute the fiber suspension by causing the disk filter system 100 to send a control signal to the dilution control valve 132 that increases the flow rate of the diluent from the diluent source 300 to the conduit 4 through which the fiber suspension is supplied to the inlet 3. In this way, the fiber suspension can be diluted at a location upstream of the inlet 3.

[0068] As described herein, the control system 400 may be fluidly connected to a pressure sensor 416 which is operable to measure the vacuum pressure of at least one of the filter units 11.

[0069] The control system 400 may be configured to monitor the vacuum pressure of at least one filter section 11 and, via the drive unit 10, increase or decrease the rotational speed of the rotor shaft 7 based on the vacuum pressure of at least one filter section 11. The control system 400 may also be configured to increase or decrease the flow rate of the diluent into the conduit based on the vacuum pressure of at least one filter section 11. The control system 400 may also be configured to increase or decrease the flow rate of the fiber suspension into the tank 2 based on the vacuum pressure of at least one filter section 11. The rotational speed of the rotor section 7, the flow rate of the diluent into the conduit 4, and the flow rate of the fiber suspension into the tank 2 can be adjusted independently or in any combination as a function of the vacuum pressure of at least one filter section 11.

[0070] In one embodiment, the control system 400 can control the operation of the disk filter 1 according to a combination of torque measured by the drive unit 10 and vacuum pressure measured for at least one filter unit 11.

[0071] In this embodiment, if the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10, and as a result the rotational speed of the rotor shaft 7 is adjusted to a second rotational speed, the machine-readable and executable instruction 406, when executed by the processing unit 402, may further cause the disk filter system 100 to automatically monitor the duration for which the rotational speed of the rotor shaft 7 is set to the second rotational speed, and to determine whether the duration for which the rotational speed of the rotor shaft 7 is set to the second rotational speed exceeds the threshold duration for the second rotational speed. If the duration for which the rotational speed of the rotor shaft 7 is set to the second rotational speed exceeds the threshold duration for the second rotational speed, the control system 400 may cause the disk filter system 100 to measure the vacuum pressure of at least one filter section, and to determine whether the vacuum pressure of at least one filter section 11 is higher than the high threshold vacuum pressure of at least one filter section 11. A significant spike in vacuum pressure, for example, a spike above the high threshold vacuum pressure, indicates that the filter unit 11 will not have an adequate level of accumulated fibers when it exits the fiber suspension in the tank 2. In this situation, the filtrate is rapidly extracted from the fiber suspension, potentially resulting in an accumulation of fiber material in the tank 2, which may necessitate stopping the disc filter system 100 to prevent damage to the filter unit 11. Furthermore, the accumulation of fiber material in the tank 2 may increase the torque applied to the drive unit 10. If the torque applied to the drive unit 10 exceeds the drive unit torque trip value, the disc filter system 100 may be stopped to prevent damage to the filter unit 11. In embodiments where the control system 400 implements a PID control scheme, the threshold time length for the second rotational speed may depend on PID adjustment parameters set to achieve the desired control behavior.

[0072] Furthermore, if (i) the time duration for which the rotational speed of the rotor shaft 7 is set to a second rotational speed exceeds a threshold time duration for the second rotational speed, and (ii) the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section 11, the control system 400 may stop the disk filter system 100 to prevent system damage. In an embodiment, the high threshold vacuum pressure of at least one filter section 11 is higher than 90% of the maximum vacuum pressure, higher than 80% of the maximum vacuum pressure, higher than 70% of the maximum vacuum pressure, higher than 60% of the maximum vacuum pressure, higher than 50% of the maximum vacuum pressure, higher than 40% of the maximum vacuum pressure, higher than 30% of the maximum vacuum pressure, or higher than 20% of the maximum vacuum pressure, where the maximum vacuum pressure may be a vacuum pressure such that, when greater, the torque continues to increase without intervention, leading to damage to the filter section 11. The maximum vacuum pressure may depend, at least in part, on the physical properties of the fiber suspension and the operating state of the disk filter. As described herein, a weak vacuum in the filter section 11 (i.e., a vacuum pressure higher than the high threshold vacuum pressure) may indicate that the disk filter 1 is not operating normally and needs to be stopped. Therefore, the risk of disk filter 1 failure can be reduced by monitoring the vacuum pressure in the filter section 11 and stopping the disk filter system 100 (if the above conditions are met).

[0073] In one embodiment, if the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10, and as a result the rotational speed of the rotor shaft 7 is adjusted to a second rotational speed, the machine-readable and executable instruction 406, when executed by the processing unit 402, may further cause the disk filter system 100 to automatically monitor the vacuum pressure of at least one filter section and determine whether the vacuum pressure is higher than the high threshold vacuum pressure. Furthermore, if the vacuum pressure is higher than the high threshold vacuum pressure, the disk filter system 100 may measure the duration of time during which the vacuum pressure is higher than the high threshold vacuum pressure and determine whether the duration of time during which the vacuum pressure is higher than the high threshold vacuum pressure is longer than the threshold duration for the high vacuum pressure. In one embodiment, the threshold duration for the high vacuum pressure may be determined based on the state of the fiber suspension and / or the operating state of the disk filter system 100.

[0074] Furthermore, if the duration for which the vacuum pressure is higher than the high threshold vacuum pressure is longer than the threshold duration for the high vacuum pressure, the control system 400 may shut down the disk filter system 100 to prevent system damage. By monitoring the duration for which the vacuum pressure is higher than the high threshold vacuum pressure, the control method of this embodiment may not react to temporary drops in vacuum that may occur during normal operation, i.e., temporary spikes in vacuum pressure.

[0075] In one embodiment, if the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10, the machine-readable and executable instruction 406, when executed by the processing unit 402, may further cause the disk filter system 100 to automatically measure the vacuum pressure of at least one filter section and determine whether the vacuum pressure of at least one filter section 11 is lower than the low threshold vacuum pressure of at least one filter section 11. Furthermore, if (i) the torque applied to the drive unit 10 is greater than the high threshold torque for the drive unit 10, and (ii) the vacuum pressure of at least one filter section is lower than the low threshold vacuum pressure of at least one filter section 11, the control system 400 may cause the disk filter system 100 to increase the rotational speed of the rotor shaft 7 from a first rotational speed to a second rotational speed that is faster than the first rotational speed via the drive unit 10.

[0076] In an embodiment, when a machine-readable and executable instruction 406 is executed by the processing unit 402, it may further cause the disk filter system 100 to automatically reduce the rotational speed of the rotor shaft 7 if (i) the torque applied to the drive unit 10 decreases to less than the low threshold torque for the drive unit 10, (ii) the vacuum pressure of at least one filter unit 11 is higher than the high threshold vacuum pressure of at least one filter unit 11, or (iii) both of the above conditions are met. In an embodiment, the low threshold torque may be 5% or more and 50% or less of the maximum torque, 5% or more and 45% or less of the maximum torque, 5% or more and 40% or less of the maximum torque, 5% or more and 35% or less of the maximum torque, 5% or more and 30% or less of the maximum torque, 5% or more and 25% or less of the maximum torque, 5% or more and 20% or less of the maximum torque, 5% or more and 15% or less of the maximum torque, or 5% or more and 10% or less of the maximum torque. In an embodiment, the low threshold torque applied to the drive unit 10 may depend on the state of the fiber suspension in the disk filter system 100. In an embodiment, the rotational speed of the rotor shaft 7 may be reduced by an amount determined based on the state of the fiber suspension and / or the operating state of the disk filter system 100.

[0077] In one embodiment, the control system 400 can increase the consistency of the fiber suspension by causing the disk filter system 100 to send a control signal to the dilution control valve 132 that reduces the flow rate of the diluent from the diluent source 300 to the conduit 4 through which the fiber suspension is supplied to the inlet 3. In this way, the consistency of the fiber suspension can be increased at a position upstream of the inlet 3.

[0078] Embodiments of the present disclosure include a control system 400 that automatically measures the filling level of the fiber suspension in the tank 2 and / or the vacuum pressure of at least one filter section 11 depending on whether the torque applied to the drive unit 10 is greater than a high threshold torque or less than a low threshold torque, but it should be understood that the control system 400 can continuously monitor the filling level and vacuum pressure.

[0079] With regard to the various thresholds for the variables measured in this disclosure, it should be understood that the specific thresholds will depend on the type of fiber suspension processed by the disk filter, the size of the disk filter, and the desired operating state and / or performance of the disk filter.

[0080] Embodiments of the present disclosure may be implemented in hardware and / or software (including firmware, resident software, microcode, etc.). As previously described herein, the control system 400 of the disk filter system 100 may include at least one processing unit 402 and a computer-readable storage medium (i.e., a memory module 404). The control system 400 may be communicatively connected to other components of the disk filter system 100 via any wired or wireless communication path. The computer-readable or computer-compatible storage medium, or one or more memory modules 404, may be any medium that contains, stores, communicates, propagates, or moves programs used by or in connection with an instruction execution system, apparatus, or device.

[0081] Computer-usable or computer-readable storage media, or memory modules 404, may, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, devices, or propagation media. More specific examples (non-exclusive list) of computer-readable storage media or memory modules 404, but are not limited to, the following, as non-exclusive examples: electrical connections with one or more wires, portable computer disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM, or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), and cloud-based storage media. Computer-usable or computer-readable storage media may be paper or other suitable media on which programs can be electronically obtained, for example, by optically scanning the paper or other media as needed, then compiling and interpreting, or otherwise appropriately processing as needed, and then storing them in computer memory.

[0082] A computer-readable storage medium or memory module 404 may include machine-readable and executable instructions 406 for performing the operations of the Disclosure. These machine-readable and executable instructions 406 may include, but are not limited to, computer program code written in a high-level programming language such as C or C++, depending on development needs. Furthermore, the computer program code for implementing the Disclosure may also be written in other programming languages, such as interpretable languages, but is not limited to any particular programming language. The scope of the Disclosure is not intended to be limited to any particular programming language. Some modules or routines may be written in assembly language or microcode to improve performance and / or memory usage. However, the software embodiments of the Disclosure are not dependent on implementation using a specific programming language. Furthermore, it will be found that the functions of any or all program modules may be implemented using individual hardware elements, one or more application-specific integrated circuits (ASICs), or programmed digital signaling units or microcontrollers.

[0083] In this embodiment, when a machine-readable and executable instruction is executed by the processing unit, it may further cause the disk filter system to automatically determine whether the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit. If the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit, the rotational speed of the rotor shaft may be increased via the variable speed drive unit from a first rotational speed to a second rotational speed that is faster than the first rotational speed.

[0084] In this embodiment, the control system may be communicatively connected to a filling level sensor that is connected to the tank and is operable to measure the filling level of the fiber suspension in the tank, and when a machine-readable and executable command is executed by the processing unit, the control system may automatically cause the disk filter system to measure the filling level of the fiber suspension in the tank if the torque applied to the variable speed drive unit is greater than the high threshold torque for the variable speed drive unit, to determine whether the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, and if the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, to dilute the fiber suspension.

[0085] In one embodiment, the inlet is connected to a conduit through which the fiber suspension is supplied to the inlet, and the control system is further communicatively connected to a dilution control valve that is operable to control the flow rate of diluent from a liquid source to the conduit, and the dilution of the fiber suspension may include increasing the flow rate of diluent from the liquid source to the conduit via the dilution control valve.

[0086] In this embodiment, the control system is communicatively connected to a pressure sensor that is fluidly connected to at least one filter section and operable to measure the vacuum pressure of at least one filter section, and when a machine-readable and executable command is executed by the processing unit, the control system may automatically cause the disk filter system to determine whether the time duration for which the rotational speed of the rotor shaft is set to a second rotational speed exceeds a threshold time duration for the second rotational speed, measure the vacuum pressure of at least one filter section, determine whether the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, and if (i) the time duration for which the rotational speed of the rotor shaft is set to a second rotational speed exceeds a threshold time duration for the second rotational speed, and further, (ii) if the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, the control system may stop the disk filter system.

[0087] In this embodiment, a machine-readable and executable instruction, when executed by the processing unit, may cause the disk filter system to automatically determine whether the torque applied to the variable speed drive unit is less than the low threshold torque for the variable speed drive unit, measure the vacuum pressure of at least one filter unit, and determine whether the vacuum pressure of at least one filter unit is higher than the high threshold vacuum pressure of at least one filter unit, and if (i) the torque applied to the variable speed drive unit is less than the low threshold torque for the variable speed drive unit, and further, (ii) the vacuum pressure of at least one filter unit is higher than the high threshold vacuum pressure of at least one filter unit, then reduce the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed slower than the first rotational speed via the variable speed drive unit.

[0088] According to a first aspect of the present disclosure, a disc filter system for dewatering a fiber suspension is a disc filter comprising a tank having an inlet located in the wall of the tank and configured to introduce a fiber suspension into the tank; a rotor shaft having a rotating shaft axis; a variable speed drive unit operably connected to the rotor shaft and configured to rotate the rotor shaft about the rotating shaft axis; and a disc filter comprising at least one filter unit connected to the rotor shaft and rotating together with the rotor shaft about the rotating shaft axis. The disk filter system further includes a control system comprising a processing unit, a memory module responsively connected to the processing unit, and a control system including machine-readable and executable instructions stored in the memory module. The control system is responsively connected to a variable speed drive unit and a torque measuring device responsive to measure the torque applied to the variable speed drive unit. When the machine-readable and executable instructions are executed by the processing unit, the disk filter system automatically measures the torque applied to the variable speed drive unit and adjusts the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed different from the first rotational speed (other than zero) via the variable speed drive unit, based on the torque applied to the variable speed drive unit.

[0089] The second aspect includes the first aspect, wherein the second rotational speed is faster than the first rotational speed.

[0090] A third aspect includes the first aspect, wherein when a machine-readable and executable instruction is executed by the processing unit, the disk filter system is further instructed to automatically determine whether the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit, and if the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit, the rotational speed of the rotor shaft is increased via the variable speed drive unit from a first rotational speed to a second rotational speed that is faster than the first rotational speed.

[0091] A fourth aspect includes the third aspect, wherein the control system is further communicatively connected to a filling level sensor which is connected to the tank and is operable to measure the filling level of the fiber suspension in the tank, and when a machine-readable and executable command is executed by the processing unit, the disk filter system is further automatically instructed to measure the filling level of the fiber suspension in the tank if the torque applied to the variable speed drive unit is greater than the high threshold torque for the variable speed drive unit, to determine whether the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, and if the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, to dilute the fiber suspension.

[0092] A fifth embodiment includes the fourth embodiment, wherein the inlet is connected to a conduit through which a fiber suspension is supplied to the inlet, and the control system is further communicatively connected to a dilution control valve that is operable to control the flow rate of diluent from a liquid source to the conduit, and the dilution of the fiber suspension includes increasing the flow rate of diluent from the liquid source to the conduit via the dilution control valve.

[0093] A sixth embodiment includes any one of the first to third embodiments, wherein the disk filter further includes at least one injection port located on the wall of the tank and configured to introduce a second flow of fiber suspension into the tank, the control system further includes a communicationally connected fill level sensor connected to the tank and operable to measure the fill level of the fiber suspension in the tank, and a machine-readable and executable command, when executed by the processing unit, further causes the disk filter system to automatically measure the fill level of the fiber suspension in the tank, determine whether the fill level of the fiber suspension in the tank is lower than a threshold fill level of the fiber suspension in the tank, and if the fill level of the fiber suspension in the tank is lower than a threshold fill level of the fiber suspension in the tank, increases the flow rate of the fiber suspension entering the tank by increasing the flow rate of the fiber suspension introduced into the tank through the inlet, increasing the flow rate of the second flow of fiber suspension introduced into the tank through at least one injection port, or both.

[0094] The seventh aspect includes any one of the third to sixth aspects, wherein the control system is further communicatively connected to a pressure sensor that is fluidly connected to at least one filter section and operable to measure the vacuum pressure of at least one filter section, and when a machine-readable and executable command is executed by the processing unit, the disk filter system is further to automatically cause the disk filter system to determine whether the time duration for which the rotational speed of the rotor shaft is set to a second rotational speed exceeds a threshold time duration for the second rotational speed, measure the vacuum pressure of at least one filter section, and determine whether the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, and if (i) the time duration for which the rotational speed of the rotor shaft is set to a second rotational speed exceeds a threshold time duration for the second rotational speed, and further (ii) if the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, the disk filter system is stopped.

[0095] The eighth aspect includes any one of the first to sixth aspects, wherein the second rotational speed is slower than the first rotational speed.

[0096] The ninth embodiment includes any one of the first to sixth embodiments, wherein the control system is further communicatively connected to a pressure sensor that is fluidly connected to at least one filter section and operable to measure the vacuum pressure of at least one filter section, and when a machine-readable and executable command is executed by the processing unit, the disk filter system is further automatically caused to determine whether the torque applied to the variable speed drive section is less than a low threshold torque for the variable speed drive section, to measure the vacuum pressure of at least one filter section, and to determine whether the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, and (i) if the torque applied to the variable speed drive section is less than a low threshold torque for the variable speed drive section, and (ii) if the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, the rotational speed of the rotor shaft is reduced via the variable speed drive section from a first rotational speed to a second rotational speed slower than the first rotational speed.

[0097] According to a tenth aspect of the present disclosure, a method for dewatering a fiber suspension includes the step of introducing the fiber suspension into a disc filter, wherein the disc filter is a tank including an inlet located in the wall of the tank and configured to introduce the fiber suspension into the tank, a rotor shaft including a rotating shaft axis, and at least one filter section connected to the rotor shaft and rotating together with the rotor shaft about the rotating shaft axis. The method for dewatering a fiber suspension includes the steps of rotating the rotor shaft about the rotating shaft axis, measuring the torque applied to a drive unit used to rotate the rotor shaft about the rotating shaft axis, and adjusting the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed different from the first rotational speed and other than zero, based on the torque applied to a variable speed drive unit.

[0098] The eleventh aspect includes the tenth aspect, wherein the second rotational speed is faster than the first rotational speed.

[0099] The twelfth aspect includes the tenth aspect and further includes the steps of determining whether the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit, and if the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit, increasing the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed that is faster than the first rotational speed.

[0100] The 13th embodiment includes any one of the 10th to 12th embodiments, the method comprising: measuring the filling level of the fiber suspension in the tank; determining whether the filling level of the fiber suspension in the tank is lower than a threshold filling level of the fiber suspension in the tank; and, if the filling level of the fiber suspension in the tank is lower than a threshold filling level of the fiber suspension in the tank, diluting the fiber suspension. It also includes.

[0101] A fourteenth aspect includes a thirteenth aspect, wherein the inlet is connected to a conduit through which a fiber suspension is supplied to the inlet, and the step of diluting the fiber suspension includes the step of increasing the flow rate of the diluent to the conduit.

[0102] A 15th aspect comprises any one of the 10th to 12th aspects, wherein the disc filter further comprises at least one injection unit located on the wall of the tank and configured to introduce a second flow of fiber suspension into the tank, the method further comprising: measuring the filling level of the fiber suspension in the tank; determining whether the filling level of the fiber suspension in the tank is lower than a threshold filling level of the fiber suspension in the tank; and if the filling level of the fiber suspension in the tank is lower than a threshold filling level of the fiber suspension in the tank, increasing the flow rate of the fiber suspension introduced into the tank through the inlet, increasing the flow rate of the second flow of fiber suspension introduced into the tank through at least one injection unit, or both, thereby increasing the flow rate of the fiber suspension entering the tank. Includes.

[0103] The 16th aspect includes any one of the 12th to 15th aspects, and includes the steps of: determining whether the time duration for which the rotational speed of the rotor shaft is set to a second rotational speed exceeds a threshold time duration for the second rotational speed when the torque applied to the variable speed drive unit is greater than a high threshold torque for the variable speed drive unit; measuring the vacuum pressure of at least one filter unit; determining whether the vacuum pressure of at least one filter unit is higher than a high threshold vacuum pressure for at least one filter unit; and stopping the disk filter system if (i) the time duration for which the rotational speed of the rotor shaft is set to a second rotational speed exceeds a threshold time duration for the second rotational speed, and further, (ii) the vacuum pressure of at least one filter unit is higher than a high threshold vacuum pressure for at least one filter unit.

[0104] The 17th aspect includes either the 10th aspect or any one of the 13th to 15th aspects, wherein the second rotational speed is slower than the first rotational speed.

[0105] The 18th aspect includes the 10th aspect or any one of the 13th to 15th aspects, and further includes the steps of: measuring the vacuum pressure of at least one filter section when the torque applied to the variable speed drive section is less than the low threshold torque for the variable speed drive section; determining whether the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section; and if (i) the torque applied to the variable speed drive section is less than the low threshold torque for the variable speed drive section, and further (ii) if the vacuum pressure of at least one filter section is higher than the high threshold vacuum pressure of at least one filter section, reducing the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed slower than the first rotational speed.

[0106] The 19th aspect includes any one of the 10th to 18th aspects, wherein the drive unit is a variable speed drive unit.

[0107] Those skilled in the art will see that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Accordingly, this specification is intended to cover various modifications and variations to the embodiments described herein, insofar as such modifications and variations are within the scope of the appended claims and equivalents. [Explanation of Symbols]

[0108] 1. Disk Filter 2 tanks 7. Rotor shaft 10 Drive unit 100 Disk Filter System 400 Control Systems 402 Processing Unit 412 Filling level sensor 416 Pressure Sensor

Claims

1. In a disc filter system for dehydrating a fiber suspension, It is a disk filter, A tank having an inlet located on the wall of the tank and configured to introduce a fiber suspension into the tank, Rotor shaft having a rotating shaft axis, A variable speed drive unit is movably connected to the rotor shaft and configured to rotate the rotor shaft around the rotation shaft axis, and A filter unit connected to the rotor shaft and rotating together with the rotor shaft around the rotation shaft axis, Includes disk filters, A control system, Processing unit, A memory module connected to the aforementioned processing unit in a manner that allows for communication, and Machine-readable and executable instructions stored in the memory module control system and Includes, The control system is communicated with the gear shift drive unit and a torque measuring device that is operable to measure the torque applied to the gear shift drive unit. The machine-readable and executable instruction, when executed by the processing unit, is automatically sent to the disk filter system. The torque applied to the aforementioned gear shift drive unit is measured. A disc filter system that adjusts the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed that is different from the first rotational speed and is not zero, based on the torque applied to the variable speed drive unit, via the variable speed drive unit.

2. The disk filter system according to claim 1, wherein the second rotational speed is faster than the first rotational speed.

3. When the machine-readable and executable instruction is executed by the processing unit, it is further automatically transmitted to the disk filter system. The system determines whether the torque applied to the gear shift drive unit is greater than the high threshold torque for the gear shift drive unit. The disc filter system according to claim 1, wherein if the torque applied to the variable speed drive unit is greater than the high threshold torque for the variable speed drive unit, the rotational speed of the rotor shaft is increased from the first rotational speed to a second rotational speed faster than the first rotational speed via the variable speed drive unit.

4. The control system is further connected to a filling level sensor that is operable to measure the filling level of the fiber suspension in the tank, and is responsive to the tank. When the machine-readable and executable instruction is executed by the processing unit, it is further automatically transmitted to the disk filter system. If the torque applied to the gear shift drive unit is greater than the high threshold torque for the gear shift drive unit, The filling level of the fiber suspension in the tank is measured. To determine whether the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, The disc filter system according to claim 3, wherein if the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, the fiber suspension is diluted.

5. The aforementioned inlet is connected to a conduit through which the fiber suspension is supplied to the inlet. The control system is further connected in a manner that allows communication with a dilution control valve that is operable to control the flow rate of the diluent from the liquid source to the conduit. The disc filter system according to claim 4, wherein the dilution of the fiber suspension includes increasing the flow rate of the diluent from the liquid source to the conduit via the dilution control valve.

6. The disc filter further includes at least one injection unit located on the wall of the tank and configured to introduce a second flow of fiber suspension into the tank, The control system is further connected to a filling level sensor that is responsive to the tank and measures the filling level of the fiber suspension in the tank, and is responsive to the tank. When the machine-readable and executable instruction is executed by the processing unit, it is further automatically transmitted to the disk filter system. The filling level of the fiber suspension in the tank is measured. The tank is made to determine whether the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank. The disc filter system according to any one of claims 1 to 3, wherein if the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, the flow rate of the fiber suspension introduced into the tank through the inlet is increased, or the flow rate of the fiber suspension of the second flow introduced into the tank through the at least one injection port is increased, or both are increased, thereby increasing the flow rate of the fiber suspension entering the tank.

7. The control system is further connected to a pressure sensor that is fluidly connected to the at least one filter section and is operable to measure the vacuum pressure of the at least one filter section, and is responsive to this connection. When the machine-readable and executable instruction is executed by the processing unit, it is further automatically transmitted to the disk filter system. If the torque applied to the gear shift drive unit is greater than the high threshold torque for the gear shift drive unit, The system determines whether the time duration during which the rotational speed of the rotor shaft is set to the second rotational speed exceeds a threshold time duration for the second rotational speed. The vacuum pressure of the at least one filter section is measured. Determine whether the vacuum pressure of the at least one filter section is higher than the high threshold vacuum pressure of the at least one filter section. The disk filter system according to any one of claims 3 to 6, wherein (i) the time period during which the rotational speed of the rotor shaft is set to the second rotational speed exceeds the threshold time period for the second rotational speed, and (ii) the vacuum pressure of the at least one filter section is higher than the high threshold vacuum pressure of the at least one filter section.

8. The disk filter system according to claim 1 or 6, wherein the second rotational speed is slower than the first rotational speed.

9. The control system is further connected in a communicative manner to a pressure sensor that is fluidly connected to the at least one filter section and is operable to measure the vacuum pressure of the at least one filter section. When the machine-readable and executable instruction is executed by the processing unit, it is further automatically transmitted to the disk filter system. The system determines whether the torque applied to the gear shift drive unit is less than the low threshold torque for the gear shift drive unit. The vacuum pressure of the at least one filter section is measured. Determine whether the vacuum pressure of the at least one filter section is higher than the high threshold vacuum pressure of the at least one filter section. (i) The torque applied to the variable speed drive unit is less than the low threshold torque for the variable speed drive unit, and (ii) If the vacuum pressure of the at least one filter unit is higher than the high threshold vacuum pressure of the at least one filter unit, the rotational speed of the rotor shaft is reduced via the variable speed drive unit from the first rotational speed to the second rotational speed which is slower than the first rotational speed, the disk filter system according to claim 1 or 6.

10. In a method for dehydrating fiber suspensions, A step of introducing a fiber suspension into a disc filter, wherein the disc filter is A tank, comprising an inlet located in the wall of the tank and configured to introduce a fiber suspension into the tank, Rotor shaft including rotating shaft axis, and The process includes including at least one filter section connected to the rotor shaft and rotating together with the rotor shaft around the rotation shaft axis, The process of rotating the rotor shaft around the rotating shaft axis, A step of measuring the torque applied to the drive unit used to rotate the rotor shaft around the rotation shaft axis, A step of adjusting the rotational speed of the rotor shaft from a first rotational speed to a second rotational speed that is different from the first rotational speed and is not zero, based on the torque applied to the variable speed drive unit. A method for dehydrating a fiber suspension containing [a specific fiber].

11. The method according to claim 10, wherein the second rotational speed is faster than the first rotational speed.

12. A step of determining whether the torque applied to the gear shift drive unit is greater than the high threshold torque for the gear shift drive unit, If the torque applied to the variable speed drive unit is greater than the high threshold torque for the variable speed drive unit, the rotational speed of the rotor shaft is increased from the first rotational speed to a second rotational speed that is faster than the first rotational speed. The method according to claim 10, further comprising:

13. A step of measuring the filling level of the fiber suspension in the tank, A step of determining whether the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, If the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, the fiber suspension is diluted. The method according to any one of claims 10 to 12, further comprising:

14. The inlet is connected to a conduit through which the fiber suspension is supplied to the inlet. The method according to claim 13, wherein the step of diluting the fiber suspension includes a step of increasing the flow rate of the diluent to the conduit.

15. The disc filter further includes at least one injection unit located on the wall of the tank and configured to introduce a second flow of fiber suspension into the tank, The aforementioned method further, A step of measuring the filling level of the fiber suspension in the tank, A step of determining whether the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, If the filling level of the fiber suspension in the tank is lower than the threshold filling level of the fiber suspension in the tank, the process of increasing the flow rate of the fiber suspension entering the tank by increasing the flow rate of the fiber suspension introduced into the tank through the inlet, increasing the flow rate of the second flow of fiber suspension introduced into the tank through the at least one injection port, or both. The method according to any one of claims 10 to 12, including the method described in any one of claims 10 to 12.

16. If the torque applied to the gear shift drive unit is greater than the high threshold torque for the gear shift drive unit, A step of determining whether the time length set at the second rotational speed of the rotor shaft exceeds a threshold time length for the second rotational speed, A step of measuring the vacuum pressure of at least one of the filter sections, A step of determining whether the vacuum pressure of the at least one filter section is higher than the high threshold vacuum pressure of the at least one filter section, (i) If the time duration for which the rotational speed of the rotor shaft is set to the second rotational speed exceeds the threshold time duration for the second rotational speed, and (ii) if the vacuum pressure of the at least one filter section is higher than the high threshold vacuum pressure of the at least one filter section, the disk filter system is stopped. The method according to any one of claims 12 to 15, including the method described in any one of claims 12 to 15.

17. The method according to any one of claims 10 or 13 to 15, wherein the second rotational speed is slower than the first rotational speed.

18. If the torque applied to the gear shift drive unit is less than the low threshold torque for the gear shift drive unit, A step of measuring the vacuum pressure of at least one of the filter sections, A step of determining whether the vacuum pressure of the at least one filter section is higher than the high threshold vacuum pressure of the at least one filter section, (i) If the torque applied to the variable speed drive unit is less than the low threshold torque for the variable speed drive unit, and (ii) if the vacuum pressure of the at least one filter unit is higher than the high threshold vacuum pressure of the at least one filter unit, the rotational speed of the rotor shaft is reduced from the first rotational speed to the second rotational speed which is slower than the first rotational speed. The method according to any one of claims 10 or 13 to 15, further comprising:

19. The method according to any one of claims 10 to 18, wherein the drive unit is a variable speed drive unit.

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