A spiral desilting device automatic control system and a reagent filtering system

Abstract

The present application provides a kind of grit chamber spiral discharge automatic control system and reagent filtering system, the automatic control system includes grit chamber spiral discharge device, detection component and control component;Grit chamber spiral discharge device includes discharge device cylinder, material conveying screw rod, variable frequency motor;Detection component includes first detection unit, second detection unit, third detection unit;Control component includes controller, and the controller is configured as: based on the preset reference inherent speed of material conveying screw rod, the spiral torque deviation of material conveying screw rod, water content compensation weight coefficient and the water content deviation of corrected discharge are calculated the target speed of material conveying screw rod, and control variable frequency motor drives material conveying screw rod to rotate at target speed.

Description

Technical Field

[0001] This invention belongs to the field of plastic recycling technology, specifically relating to an automatic control system for spiral slag discharge of a sedimentation tank and a chemical filtration system. Background Technology

[0002] In the recycling process of PET tray waste plastics, the chemical filtration system is the core unit for realizing chemical reuse, reducing recycling costs, and ensuring cleaning effect. Among them, the sand setter, as a key equipment for solid-liquid separation, is mainly used to separate solid impurities such as PET fragments and adhesive clumps in the cleaning agent. The stability of its spiral slag discharge directly affects the operating efficiency and economy of the entire recycling system.

[0003] Currently, in existing PET recycling production lines, the spiral discharge of sedimentation tanks generally adopts a rough control mode with fixed speed, timed start and stop, and fixed flow rate set manually based on experience. This mode suffers from prominent problems such as a lack of refined control and poor adaptability to operating conditions: the spiral speed, spiral pitch, and real-time solid content of the cleaning agent cannot be dynamically matched. If the speed is too low, it is easy to cause solid impurities to accumulate in the cylinder and the spiral shaft to become stuck and blocked; if the speed is too high, a large amount of cleaning agent water will be discharged with the solid slag, resulting in unnecessary waste of cleaning agent and a decrease in the recycling rate. At the same time, the industry generally lacks online monitoring methods for the moisture content of the discharged slag, making it impossible to dynamically adjust the spiral speed according to the actual dewatering effect. This leads to long-term large fluctuations in the moisture content of the discharged slag. If the moisture content is too high, it will increase the cost of subsequent solid waste pressure filtration and drying treatment. If the moisture content is too low, it will easily cause dry slag caking, exacerbate the spiral load oscillation, and increase the risk of blockage.

[0004] Specifically, the existing technology for adjusting the spiral speed relies on manual experience or simple timing and flow logic. If a fixed speed is used, the speed cannot be increased in time to prevent blockage when the solid content increases, and the speed cannot be reduced in time to save water when the solid content decreases, resulting in a long-term dilemma of "either blockage or waste of medicine".

[0005] Secondly, existing technologies completely ignore the strong coupling relationship between the slag moisture content and the screw speed, and fail to incorporate the final dewatering effect into the speed control logic. The slag moisture content is the final result indicator of solid-liquid separation, which is directly determined by the screw residence time. The residence time is entirely determined by the screw speed: the higher the speed, the shorter the pressing stroke and residence time of the slag in the screw, the higher the slag moisture content and the greater the amount of reagent carried out; the lower the speed, the longer the pressing time, the lower the moisture content and the easier it is to caking and deposit.

[0006] Therefore, those skilled in the art need to improve existing control systems to overcome the aforementioned deficiencies. Summary of the Invention

[0007] This invention addresses the technical problems of existing technologies, such as coarse control of screw speed, easy clogging, waste of reagents, large fluctuations in slag moisture content, and lag in adjustment. This invention provides an automatic control system for screw slag discharge in a sand setter and a reagent filtration system. The main PID closed loop is constructed using the real-time torque of the screw, and the moisture content deviation after speed coupling correction is introduced as a feedforward compensation to achieve dynamic and fine adjustment of the screw speed.

[0008] To achieve the above objectives, in a first aspect, this application provides an automatic control system for a spiral slag discharger for a sand setter, including a spiral slag discharger device, a detection component, and a control component. The sedimentation tank spiral slag discharge device includes a slag discharge device cylinder, a material inlet, a slag discharge outlet and a reagent overflow outlet opened on the slag discharge device cylinder, a material conveying screw rotatably installed in the slag discharge device cylinder, and a variable frequency motor that drives the material conveying screw to rotate. The detection assembly includes a first detection unit for detecting the rotational speed of the material conveying screw, a second detection unit for detecting the load torque of the material conveying screw, and a third detection unit for detecting the moisture content of the slag at the discharge port. The control component includes a controller configured to: calculate the slag discharge moisture content deviation based on the actual moisture content of the slag detected by the third detection unit and the preset slag moisture content; calculate the corrected slag discharge moisture content deviation based on the slag discharge moisture content deviation, the rotation speed-moisture content coupling correction coefficient, the real-time rotation speed of the material conveying screw detected by the first detection unit, and the preset rated optimal operating speed of the material conveying screw; calculate the helical torque deviation of the material conveying screw based on the load torque of the material conveying screw detected by the second detection unit and the preset target torque; calculate the target rotation speed of the material conveying screw based on the preset reference inherent rotation speed of the material conveying screw, the helical torque deviation of the material conveying screw, the moisture content compensation weight coefficient, and the corrected slag discharge moisture content deviation; and control the variable frequency motor to drive the material conveying screw to rotate at the target rotation speed.

[0009] Optionally, the deviation in slag moisture content ,in, The actual moisture content of the slag material detected by the third detection unit at time k. The preset moisture content of the slag material.

[0010] Optionally, the corrected slag discharge moisture content deviation Where α is the rotational speed-moisture content coupling correction coefficient. This represents the real-time rotational speed of the material conveying screw detected by the first detection unit at time k. This is the preset rated optimal operating speed of the material conveying screw.

[0011] Optionally, the helical torque deviation of the material conveying screw ,in, For the preset target torque, The load torque of the material conveying screw detected by the second detection unit at time k is denoted as .

[0012] Optionally, the target rotational speed of the material conveying screw, + + ,in, The reference natural speed of the material conveying screw. This is the cumulative sum of torque deviations from the initial time to the current time k. This represents the rate of change of torque deviation. = - This is the proportionality coefficient. K is the integral coefficient. d These are the differential coefficients. This is the moisture content compensation weighting coefficient.

[0013] Optionally, the first detection unit is a speed encoder, which is connected to the output shaft of the variable frequency motor via a coupling.

[0014] Optionally, the third detection unit is a capacitive online moisture content sensor, which is fixedly installed on the inner wall of the slag discharge port.

[0015] Optionally, the second detection unit is a strain gauge torque sensor, which is fixedly installed at the connection between the output shaft of the variable frequency motor and the material conveying screw.

[0016] To achieve the above objectives, in a second aspect, this application provides a reagent filtration system, including the aforementioned automatic control system for spiral slag discharge from the sedimentation tank.

[0017] Optionally, it also includes a sedimentation tank, a sand setter located at the bottom of the sedimentation tank, a paper belt filter, and a water collection tank. The separated reagent enters the sedimentation tank for settling. The upper layer of reagent after separation enters the paper belt filter for filtration. The lower layer of sediment after separation is discharged into the sand setter through a valve. The reagent separated by the sand setter enters the paper belt filter. The material outlet at the bottom of the sand setter is connected to the material inlet on the slag discharge device cylinder.

[0018] This invention provides an automatic control system for spiral slag discharge and a chemical filtration system for a sand setter. Compared with existing technologies, its advantages are as follows: This invention dynamically corrects the rotation speed by following the changes in spiral load torque in real time: Increased torque indicates increased slag and a tendency for sedimentation and blockage, so the target rotation speed is automatically increased for rapid slag discharge and anti-blockage; Low torque indicates low slag load, so the rotation speed is automatically reduced. The integral term eliminates long-term steady-state deviations, and the derivative term suppresses sudden speed overshoot. Combined with the lower limit constraint of rotation speed, this completely solves the defects of traditional fixed rotation speed which is prone to blockage and manual adjustment which is lagging, significantly reducing the downtime failure rate. In addition, a corrected moisture content deviation is introduced. When the moisture content of the discharged slag is too high, it indicates that the original rotation speed is too fast, the pressing time is insufficient, and a large amount of chemical is carried out. The rotation speed is automatically and appropriately reduced to extend the pressing and dehydration time, significantly reducing the loss of chemical with the slag; When the moisture content is too low, the slag is too dry and prone to caking, so the rotation speed is automatically and appropriately increased to balance dehydration indicators and continuous slag discharge, significantly improving the recycling rate of cleaning chemicals and reducing raw material consumption costs. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This is a schematic diagram of a drug circulation system. Figure 1 ; Figure 2 This is a schematic diagram of a drug circulation system. Figure 2 .

[0020] The components include: 1. Sedimentation tank; 2. Grit chamber; 3. Paper belt filter; 4. Water collection tank; 5. Spiral slag discharge device for grit chamber. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0024] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0025] In addition, the term "multiple" should mean two or more.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] like Figures 1-2 As shown, a chemical filtration system includes a sedimentation tank 1, a sand setter 2 located at the bottom of the sedimentation tank 1, a paper belt filter 3, and a water collection tank 4. The separated chemicals enter the sedimentation tank 1 for settling. The upper layer of chemicals after separation enters the paper belt filter 3 for filtration. The lower layer of sediment after separation is discharged into the sand setter 2 through a valve. The chemicals separated in the sand setter 2 enter the paper belt filter 3. The material discharge port at the bottom of the sand setter 2 is connected to the spiral slag discharge device 5 of the sand setter.

[0028] The spiral slag discharge device 5 for the sand settling chamber includes a slag discharge device cylinder, a material inlet, a slag discharge port, and a reagent overflow port opened on the slag discharge device cylinder, a material conveying screw rotatably installed in the slag discharge device cylinder, and a variable frequency motor with a power of 3kW and a frequency range of 0-100r / min that drives the material conveying screw to rotate. The material inlet is connected to the material discharge port, and a slag collection bucket can be set at the slag discharge port to collect slag. The reagent overflow port can also be connected to the paper belt filter 3 for reagent recycling and reuse, avoiding reagent waste.

[0029] In addition to the aforementioned spiral slag discharge device 5, the automatic control system for the sand setter spiral discharge also includes detection components and control components. The detection assembly includes a first detection unit for detecting the rotational speed of the material conveying screw, a second detection unit for detecting the load torque of the material conveying screw, and a third detection unit for detecting the moisture content of the slag at the slag discharge port. The first detection unit is a speed encoder, which is connected to the output shaft of the variable frequency motor via a coupling. The third detection unit is a capacitive online moisture content sensor, which is fixedly installed on the inner wall of the slag discharge port. The second detection unit is a strain gauge torque sensor, which is fixedly installed at the connection between the output shaft of the variable frequency motor and the material conveying screw.

[0030] The control component includes a controller configured to: calculate the slag discharge moisture content deviation based on the actual moisture content of the slag detected by the third detection unit and the preset slag moisture content; calculate the corrected slag discharge moisture content deviation based on the slag discharge moisture content deviation, the rotation speed-moisture content coupling correction coefficient, the real-time rotation speed of the material conveying screw detected by the first detection unit, and the preset rated optimal operating speed of the material conveying screw; calculate the screw torque deviation of the material conveying screw based on the load torque of the material conveying screw detected by the second detection unit and the preset target torque; calculate the target rotation speed of the material conveying screw based on the preset reference inherent rotation speed of the material conveying screw, the screw torque deviation of the material conveying screw, the moisture content compensation weight coefficient, and the corrected slag discharge moisture content deviation; and control the variable frequency motor to drive the material conveying screw to rotate at the target rotation speed.

[0031] Specifically: the deviation in moisture content of the discharged slag ,in, The actual moisture content of the slag material detected by the third detection unit at time k. The corrected slag discharge moisture content deviation is used to preset the slag material moisture content. Where α is the rotational speed-moisture content coupling correction coefficient. This represents the real-time rotational speed of the material conveying screw detected by the first detection unit at time k. The screw torque deviation of the material conveying screw is the preset rated optimal operating speed. ,in, For the preset target torque, The load torque of the material conveying screw detected by the second detection unit at time k, and the target rotational speed of the material conveying screw. + + ,in, The reference natural speed of the material conveying screw. This is the cumulative sum of torque deviations from the initial time to the current time k. This represents the rate of change of torque deviation. = - This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. This is the moisture content compensation weighting coefficient, which indicates how much the screw speed needs to be adjusted for every 1% change in moisture content.

[0032] Parameter Description: The controller uses a Siemens S7-1200 PLC, running an adaptive screw speed control algorithm and a closed-loop control algorithm for slag discharge moisture content. The parameters are calibrated as follows: n0 = 50. =0.8, =0.05, =0.1, K w =-0.5, α=0.3%, =60.

[0033] It should be noted that the above formula only performs numerical calculations and does not substitute dimensions. Furthermore, the reference natural speed n0 of the material conveying screw and the preset rated optimal operating speed of the material conveying screw are considered. The specific differences are as follows: n0 represents the design screw pitch, cylinder diameter, and steady-state base speed under normal load, which is the system's preset "standard operating speed." Its calibration is based on the following conditions: no abnormal blockage in the sand setter, no excessive moisture content, and the solid content of the reagent water is within the normal range (not optimal). The preset rated optimal operating speed of the material conveying screw is the same as the rated optimal operating speed of the screw. This refers to the rotational speed of the grit chamber when it is in "rated operating condition," that is, the standard rotational speed of the grit chamber under rated capacity and optimal solid-liquid separation effect. Its calibration is based on the optimal operating condition where the grit chamber capacity reaches the rated value, the slag moisture content is optimal, and the amount of reagent carried out is minimal.

[0034] Explanation of principles: In the core formula of this invention, + The torque PID controller dynamically adjusts the rotational speed in real time according to the changes in the screw load torque: an increase in torque indicates an increase in slag and a tendency for slag to accumulate and block the rotor, so the target rotational speed is automatically increased to quickly discharge slag and prevent blockage; a low torque indicates a low slag load, so the rotational speed is automatically reduced. The integral term eliminates long-term steady-state deviations, and the derivative term suppresses speed overshoot due to sudden changes. Combined with the lower limit constraint of rotational speed, it completely solves the defects of traditional fixed rotational speed that are prone to blockage and the lag of manual adjustment, and significantly reduces the downtime failure rate.

[0035] Furthermore, this invention uses the corrected moisture content deviation through... The algorithm directly embeds the rotation speed calculation formula. When the moisture content of the slag is too high, it indicates that the original rotation speed is too fast, the pressing time is insufficient, and a large amount of chemicals are carried out. The algorithm automatically and appropriately lowers the rotation speed to extend the pressing and dehydration time and significantly reduce the loss of chemicals with the slag. When the moisture content is too low and the slag is too dry and prone to caking, the algorithm automatically and appropriately increases the speed to balance the dehydration index and continuous slag discharge, significantly improving the recycling rate of cleaning chemicals and reducing the cost of raw material consumption.

[0036] The faster the screw rotation speed, the shorter the residence time and pressing / dehydration time of the slag within the screw cylinder. Consequently, the chemical water cannot be separated and squeezed out in time, resulting in a naturally higher moisture content in the discharged slag. Conversely, the slower the screw rotation speed, the longer the residence time and pressing time of the slag, resulting in sufficient precipitation of the chemical water and a naturally lower moisture content in the discharged slag. In other words, fluctuations in the screw rotation speed itself will actively cause fluctuations in moisture content. If the measured moisture content deviation is directly used to control the speed, the controller will reduce the speed when the moisture content is detected to be too high. The reduction in speed will further reduce the moisture content. Subsequently, the controller will increase the speed again because the moisture content is too low. This forms a closed-loop self-excited oscillation with mutual disturbance between speed and moisture content, which becomes increasingly chaotic with each adjustment. This invention innovatively introduces a corrected moisture content deviation. It first eliminates the false moisture content deviation caused by the speed fluctuation itself, retaining only the true moisture content deviation caused by changes in the solid content, viscose content, and chemical concentration of the material, and then adjusts the speed to cut off the self-excited oscillation at its source.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An automatic control system for spiral slag discharge in a sand setter, characterized in that, Includes a spiral slag discharge device for the sand settling chamber, detection components, and control components; The sedimentation tank spiral slag discharge device includes a slag discharge device cylinder, a material inlet, a slag discharge outlet and a reagent overflow outlet opened on the slag discharge device cylinder, a material conveying screw rotatably installed in the slag discharge device cylinder, and a variable frequency motor that drives the material conveying screw to rotate. The detection assembly includes a first detection unit for detecting the rotational speed of the material conveying screw, a second detection unit for detecting the load torque of the material conveying screw, and a third detection unit for detecting the moisture content of the slag at the discharge port. The control component includes a controller configured to: calculate the slag discharge moisture content deviation based on the actual moisture content of the slag detected by the third detection unit and the preset slag moisture content; calculate the corrected slag discharge moisture content deviation based on the slag discharge moisture content deviation, the rotation speed-moisture content coupling correction coefficient, the real-time rotation speed of the material conveying screw detected by the first detection unit, and the preset rated optimal operating speed of the material conveying screw; calculate the screw torque deviation of the material conveying screw based on the load torque of the material conveying screw detected by the second detection unit and the preset target torque; calculate the target rotation speed of the material conveying screw based on the preset reference inherent rotation speed of the material conveying screw, the screw torque deviation of the material conveying screw, the moisture content compensation weight coefficient, and the corrected slag discharge moisture content deviation; and control the variable frequency motor to drive the material conveying screw to rotate at the target rotation speed. The rotation speed-moisture content coupling correction coefficient represents the false moisture content deviation caused by the rotation speed fluctuation itself, and the moisture content compensation weight coefficient represents how much screw speed needs to be adjusted for every 1% change in moisture content.

2. The automatic control system for spiral slag discharge of a sand setter as described in claim 1, characterized in that: The deviation in moisture content of the slag discharge ,in, The actual moisture content of the slag material detected by the third detection unit at time k. The preset moisture content of the slag material.

3. The automatic control system for spiral slag discharge of a sand setter as described in claim 2, characterized in that: The corrected slag discharge moisture content deviation Where α is the rotational speed-moisture content coupling correction coefficient. This represents the real-time rotational speed of the material conveying screw detected by the first detection unit at time k. This is the preset rated optimal operating speed of the material conveying screw.

4. The automatic control system for spiral slag discharge of a sand setter as described in claim 3, characterized in that: The screw torque deviation of the material conveying screw ,in, For the preset target torque, The load torque of the material conveying screw detected by the second detection unit at time k is denoted as .

5. The automatic control system for spiral slag discharge of a sand setter as described in claim 4, characterized in that: The target rotational speed of the material conveying screw. + + ,in, The reference natural speed of the material conveying screw. This is the cumulative sum of torque deviations from the initial time to the current time k. This represents the rate of change of torque deviation. = - This is the proportionality coefficient. K is the integral coefficient. d These are the differential coefficients. This is the moisture content compensation weighting coefficient.

6. The automatic control system for spiral slag discharge of a sand setter as described in claim 1, characterized in that: The first detection unit is a speed encoder, which is connected to the output shaft of the variable frequency motor via a coupling.

7. The automatic control system for spiral slag discharge of a sand setter as described in claim 1, characterized in that: The third detection unit is a capacitive online moisture content sensor, which is fixedly installed on the inner wall of the slag discharge port.

8. The automatic control system for spiral slag discharge of a sand setter as described in claim 1, characterized in that: The second detection unit is a strain gauge torque sensor, which is fixedly installed at the connection between the output shaft of the variable frequency motor and the material conveying screw.

9. A pharmaceutical filtration system, characterized in that: Including an automatic control system for spiral slag discharge of a sand setter as described in any one of claims 1-8.

10. A pharmaceutical filtration system as described in claim 9, characterized in that: It also includes a sedimentation tank, a sand setter located at the bottom of the sedimentation tank, a paper belt filter, and a water collection tank. The separated reagent enters the sedimentation tank for settling. The upper layer of reagent after separation enters the paper belt filter for filtration. The lower layer of sediment after separation is discharged into the sand setter through a valve. The reagent separated by the sand setter enters the paper belt filter. The material outlet at the bottom of the sand setter is connected to the material inlet on the slag discharge device cylinder.

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