Apparatus and method for controlling pressure filters

Abstract

The present disclosure relates to apparatuses and methods of controlling a pressure filter. The apparatus includes a pressure filter that performs a solid-liquid separation to produce a filter cake and a moisture analyzer to provide an indication of the moisture content of the filter cake. One or more controllers can be used to set a drying time of the solid-liquid separation using the indication of the moisture content.

Description

[0001] This application is a divisional application of Metso Outote Finland GmbH's invention patent application (filed on November 1, 2021, application number 202111283358.6, entitled "Apparatus and Method for Controlling Pressure Filters"). Technical Field

[0002] This disclosure relates to pressure filters. More particularly, it relates to controlling pressure filters. Background Technology

[0003] Filtration cycles are traditionally controlled by a process recipe, which is divided into different subroutines. Each subroutine has operating parameters that affect the performance of the pressure filter. These operating parameters are entered manually, without taking into account changes in feed characteristics or filter media conditions. Summary of the Invention

[0004] Purpose

[0005] One objective is to mitigate the aforementioned drawbacks.

[0006] In particular, one objective is to provide pressure filters that offer improved process control and reduced human intervention.

[0007] Another objective is to provide pressure filtration that can automatically stabilize the output relative to changes in feed quality.

[0008] Improving productivity through optimized solid-liquid separation cycles for pressure filtration is also an objective.

[0009] For example, one objective is to optimize the balance between energy consumption and output quality, including output consistency.

[0010] In addition, one objective is to improve the flexibility of pressure filter operation and control, and to enhance process visibility, even under varying process conditions.

[0011] summary

[0012] As discovered in this disclosure, various improvements to the operation of a pressure filter can be achieved by measuring an indication of the moisture content of the filter cake produced by the pressure filter and using it as a controlled variable of the pressure filter. In particular, it has been found that multivariate control can be effectively utilized. It has also been found that an indication of the operating capacity of the pressure filter, along with an indication of moisture content, can be used as a controlled variable to significantly improve the operation of the pressure filter. Automated process control using one or more controlled variables allows for significant improvements compared to manual operation of the pressure filter, where laboratory samples of the filter cake are collected only occasionally for quality monitoring and therefore do not respond immediately to process changes. Moreover, any possibility of changing the operating parameters of the pressure filter in the correct direction during manual operation relies on the operator's ability to understand the process and filtration theory. Changes in the feed to the pressure filter can be relatively rapid (e.g., changes in feed density) or slow (e.g., clogging of the filter media). Automated measurement of one or more controlled variables allows for a rapid response to any changes in their values ​​via one or more control operations. In turn, the automated execution of one or more control operations allows for a significant reduction in response time to changes. Each control operation can be associated with a setpoint value, which can be provided through the optimization of one or more controlled variables. Within the context of this disclosure, it has been determined that specific operational improvements can be achieved when control operations include setting a drying time and optionally, the feed rate and / or extrusion rate for the pressure filter. Each control operation can therefore be associated with optimizing an operational phase of the pressure filter. Each control operation may correspond to a manipulated variable used to control the pressure filter. In addition to drying time, manipulated variables may include feed rate (such as feed weight) and / or extrusion rate (such as extrusion time or extrusion pressure).

[0013] In this specification, a moisture content may refer to the moisture content itself or one or more parameter values ​​indicating the moisture content. For example, it may refer to the average of more than one measurement of the moisture content of a single filter cake at different locations. Moisture content may correspond to the residual moisture of the filter cake. Similarly, an indication of operating capacity may refer to the operating capacity or one or more parameter values ​​representing the operating capacity. Operating capacity may correspond to the amount of filter cake produced within a time period. The foregoing applies accordingly to any other indications mentioned below. "Indication" in this specification may refer to one or more parameter values.

[0014] According to a first aspect, a device for controlling a pressure filter is disclosed. The device includes a pressure filter that performs solid-liquid separation to produce a filter cake and a moisture analyzer for providing an indication of the moisture content of the filter cake. The moisture content indication can be used to set the drying time for solid-liquid separation. The device may include one or more controllers for this purpose. Optimizing the drying time can significantly improve the performance of the pressure filter, as drying is an expensive stage in the solid-liquid separation process. This is particularly significant in air drying due to the energy required to generate compressed air. The one or more controllers can be configured to set one or more setpoint values ​​associated with one or more control operations of the pressure filter. Automated moisture sampling and parameter adjustment can significantly reduce the input required by human operators.

[0015] In one embodiment, the moisture analyzer is or includes a microwave analyzer, a capacitive sensor, or a near-infrared sensor. This has been found to improve reliability, thereby enabling accurate calculation of setpoint values, including drying time, for the control operations disclosed herein. Particular advantages have been observed with the use of a microwave analyzer. In a further embodiment, the moisture analyzer has an accuracy of ±0.5 w%, which has been found to significantly improve control performance. Any combination of the above-described devices may also be used.

[0016] In one embodiment, the device is configured to set the drying time using an indication of moisture content provided by more than one solid-liquid separation cycle of the pressure filter. This mitigates rapid changes in one or more set points during the cycle due to measurement errors or unexpected stops.

[0017] In one embodiment, one or more controllers include a multivariable controller. This is to utilize an indication of moisture content to set the drying time for solid-liquid separation, and it allows for significant improvement in the control of the pressure filter through multivariable optimization. This includes multiple controlled variables and / or multiple manipulated variables, where one or more manipulated variables can be manipulated by one or more control operations. Particularly for pressure filters, this allows one or more objectives (such as the controlled variables (or their values) disclosed herein) to be optimized (simultaneously) by means of optimized control operations performed on solid-liquid separation in multiple separate operating phases. Regarding multivariable optimization, all references to “setting” one or more setpoint values ​​(such as drying time) disclosed herein can include any combination of setting one or more setpoint values ​​for controlled variables, particularly setting setpoint values ​​for all controlled variables. As a result of a single optimization problem, the multivariable controller can produce multiple setpoint values, thereby optimizing the performance of the pressure filter across multiple control operations. Importantly, one or more control operations and their one or more control values ​​can correspond to the manipulated variables of the multivariable controller, while one or more indications, particularly indications of moisture content and optional operating capacity, act as one or more controlled variables of the multivariable controller.

[0018] In one embodiment, one or more controllers include a multivariable MPC (Model Predictive Control) controller. This is to utilize the moisture content indication to set the drying time for solid-liquid separation, and this not only provides the modeling advantages of model predictive control and the effects of the aforementioned multivariable control, but also improves the integration of solid-liquid separation with one or more upstream control processes, thus allowing its information to be used for solid-liquid separation process control at the pressure filter. This allows the dynamics of the upstream process to better explain the solid-liquid separation. While one of the main advantages of MPC is its ability to handle slow-response dynamics, it is also suitable for controlling batch-operated equipment such as pressure filters. One advantage here is its built-in ability to consider process constraints and the desired priorities among the controlled variables.

[0019] In one embodiment, the device is configured to additionally utilize an indication of moisture content to set the pressure filter's compression rate. This has been found to allow for optimized control at specific critical operational stages of solid-liquid separation, thereby significantly improving the pressure filter's operational performance.

[0020] In one embodiment, the device includes one or more weight sensors for providing an indication of the filter cake weight. This can be used to provide an indication of the operating capacity of the pressure sensor. This effectively utilizes the feed rate setting as a manipulated variable, thus effectively reducing the risk of overfilling the pressure filter chamber and consequently causing the pressure filter to rupture.

[0021] In one embodiment, the pressure filter includes one or more load cells for providing an indication of the filter cake weight. This allows for an indication of the operating capacity of the pressure sensor. Specifically, it can be used to provide an indication before the filter cake is discharged from the filter chamber of the pressure filter. The accuracy of the operating capacity indication is improved by using one or more load cells. This, in turn, significantly improves the performance of the pressure filter, as it can operate near its limits without being damaged by overfilling.

[0022] In a further embodiment, the device is configured to use a weight indication to set the feed rate of the pressure filter. This allows the feed rate to be effectively used as a controlled manipulator variable to allow the pressure filter to operate closer to its maximum capacity while managing the risk of overfilling the filter chamber. The weight indication can be used to provide a capacity indication of the pressure filter.

[0023] In one embodiment, the device is configured to simultaneously use an indication of moisture content and an indication of the operating capacity of the pressure filter to set the drying time, as well as, optionally, the feed rate and / or the pressure filter compression rate. This allows for the simultaneous optimization of both the quality and efficiency of solid-liquid separation, optionally across several key operational stages.

[0024] In one embodiment, the device includes one or more sensors for providing an indication of the quality of the washing phase of the solid-liquid separation. This is used to set one or more setpoint values, such as control values ​​for the washing phase, i.e., the washing of the filter cake and / or the drying time. The latter allows for direct optimization of one or more control operations of the washing phase, such as washing time and / or the amount of washing medium.

[0025] In one embodiment, the device includes one or more sensors for providing indications of the pH, conductivity, or turbidity of the filtrate produced by the pressure filter. This is used to set one or more setpoint values, such as drying time and / or control values ​​for washing the filter cake. This can be used to improve control over the filtrate of the pressure filter, which may be important in some applications. When solid-liquid separation includes washing the filter cake, any or all of the foregoing indications can be used to set one or more control values ​​for washing, such as washing time and / or the amount of washing medium.

[0026] According to a second aspect, a method for controlling a pressure filter used for solid-liquid separation is disclosed. The method includes receiving an indication of the moisture content of the filter cake produced by the pressure filter for solid-liquid separation, and using the moisture content indication to set a drying time for the solid-liquid separation.

[0027] The method may additionally include any combination of the above-described operations for prompting the setting of one or more setpoint values. For example, the method may include additionally receiving an indication of the operating capacity of the pressure filter and using that indication to set one or more setpoint values ​​for controlling operation, such as drying time. The method may also include using an indication of moisture content and / or an indication of operating capacity to set the feed rate and / or the extrusion rate of the pressure filter. The method may involve multivariate optimization (e.g., through model predictive control) to set the drying time and optionally the feed rate and / or extrusion rate.

[0028] The method may include receiving any number of additional indications, which may be used in conjunction with other indications for setting any setpoint values. The method may include receiving an indication of the filter cake weight and using that indication to provide an indication of operating capacity. The method may include receiving an indication of the quality of the washing phase of solid-liquid separation and using it to set one or more setpoint values, such as drying time and / or control values ​​for the washing phase, such as the amount of washing time and / or washing medium. The method may include receiving an indication of the pH and / or conductivity of the filtrate produced by the pressure filter (such as washing filtrate produced during filter cake washing) and using that indication to set one or more setpoint values, such as drying time. Any number of indications may be used simultaneously to set the drying time and optionally the feed rate and / or extrusion rate, but other control values, such as washing time and / or the amount of washing medium, may also be used if necessary. The indications used may be received from more than one solid-liquid separation cycle of the pressure filter.

[0029] In one embodiment, the method includes receiving an indicated weight of the filter cake. The weight indication, along with a moisture content indication, is used to set the drying time, feed rate, and optionally the compression rate for the pressure filter.

[0030] According to a third aspect, a controller is configured to cause the method according to the second aspect or any embodiment thereof to be executed. The controller may be configured to set any number of setpoint values ​​to control a pressure filter. It may be configured to utilize controlled variables and / or manipulated variables and any combination thereof as indicated in this disclosure.

[0031] A computer program product may also be provided, comprising instructions that, when executed by a computer, cause the computer to perform the method according to the second aspect.

[0032] It should be understood that the above aspects and embodiments can be used in any combination with each other. Several aspects and embodiments can be combined together to form further embodiments of the present invention. Attached Figure Description

[0033] This specification includes accompanying drawings to aid in further understanding, and the drawings form part of this specification. The drawings illustrate various examples and, together with the textual description, help to explain the principles of this disclosure. In the drawings: Figure 1a This illustrates solid-liquid separation using a pressure filter according to an example. Figure 1b This illustrates solid-liquid separation using a pressure filter according to another example; Figure 2 This illustrates a device for controlling a pressure filter according to an example; Figure 3 This illustrates a control system for a pressure filter according to an example; and Figure 4 This illustrates a method for controlling a pressure filter according to an example.

[0034] The same reference numerals are used in the accompanying drawings to indicate equivalent or at least functionally equivalent parts. Detailed Implementation

[0035] The detailed description provided below, in conjunction with the accompanying drawings, is intended as an example and not to represent the only form that can be constructed or utilized. However, the same or equivalent functionality and structure can be implemented through different examples.

[0036] Figure 1a The illustration shows solid-liquid separation (also referred to as “separation” in this specification) performed using a pressure filter 100 according to an example (shown as part of a plate assembly of the pressure filter). In this process, the pressure filter receives a feed 12 such as a slurry, and the liquid is removed from the feed during solid-liquid separation to produce a filter cake 14 (also referred to as a “cake” in this specification). The filter cake has a lower moisture content than the feed, while the liquid is removed as filtrate 16 of the pressure filter. The pressure filter is a batch-operated device configured to process subsequent batches of feed individually. One batch is processed during one operating cycle of the pressure filter (also referred to as a “solid-liquid separation cycle” in this specification). The pressure filter can be an automatic filter, which can be configured to automatically process multiple subsequent feeds. The pressure filter can thus be configured to automatically perform multiple subsequent operating cycles.

[0037] Pressure filter 100 can be configured for a variety of applications. The pressure filter can be a concentrator filter, in which case its optimization may focus on optimizing the operating capacity and / or energy consumption of the pressure filter, but also on operating quality, particularly the residual moisture in the filter cake. The pressure filter can also be a bulk material and / or tailings filter. The pressure filter can be primarily used to provide filtrate 16 and / or filter cake 14 as the final product. In particular, the pressure filter can be a mineral processing filter such as a tailings filter, or a chemical processing filter such as a pigment production filter. In the former case, the feed 12 can be a slurry from an upstream mineral processing step. Especially in the latter case, solid-liquid separation may include washing as an important stage in the processing. For example, the pressure filter can be a PF filter (particle filter), an FFP (quick-open pressure filter) filter, or a PF-DS (double-sided) filter. Typically, the pressure filter can be a horizontal or vertical pressure filter and / or a double-sided filter. Horizontal pressure filters have horizontally placed filter plates, while vertical pressure filters have vertically placed filter plates. Although... Figure 1a This diagram illustrates a horizontal pressure filter, such as a PF filter, but the principles illustrated also apply to other types of pressure filters. As an additional example, Figure 1b It is shown in the form of a vertical pressure filter, such as an FFP filter.

[0038] Pressure filter 100 may include one or more filter chambers 102, through which feed may be (individually) introduced for separation. After separation, filter cake 14 may subsequently (individually) be discharged from one or more filter chambers 50. In some pressure filters, such as PF filters, filter cake may enter and exit the filter chambers on filter media 110, which may extend through multiple filter chambers. In some pressure filters, such as FFP filters, multiple filter chambers may have their own independent filter media. Pressure filters may be configured to simultaneously introduce and / or discharge feed into filter chambers (e.g., for FP filters) or sequentially introduce and / or discharge feed into filter chambers (e.g., for FFP filters). For example, for this purpose, a conveyor may extend through multiple filter chambers. For example, two or more filter chambers may be stacked to form a compact structure of the pressure filter. This also allows the filter cake to be discharged by gravity. Pressure filters or devices may also include one or more conveyors, such as conveyor belts, for transporting the filter cake after it has been discharged from the filter chambers.

[0039] Solid-liquid separation may include multiple stages (also referred to as "operation stages" in this specification), such as filtration stage 10, extrusion stage 20, and drying stage 40. In one example, the separation includes the three stages described above in the order shown, as indicated by the dashed arrows in the figure. The separation may additionally include one or more washing stages 30, which may follow extrusion stage 20, as indicated by the dashed arrows in the figure. Each washing stage 30 may be followed by an additional extrusion stage 20, as indicated by the dashed arrows in the figure.

[0040] Filtration stage 10 includes directing feed 12 into the pressure filter 100, particularly into one or more of its filter chambers 102. This can be performed by pumping. In this specification, feed rate may refer to the amount of feed delivered into the filter chamber in a single operating cycle, or one or more parameter values ​​representing that feed rate. The pressure filter may include one or more distribution channels 120, such as pipes and / or hoses, for directing feed into the pressure filter and one or more filter chambers. Filtrate 16 flows through a filter medium, such as a filter screen, of the pressure filter into a filtrate collection area 122 of the pressure filter, from which the filtrate may be discharged for treatment or further use. The filtered material forms a filter cake 14. The filter cake may be collected on the filter medium.

[0041] The extrusion stage 20 includes using the extrusion unit 130 of the pressure filter 100 to extrude the filter cake 14 with extrusion pressure. The extrusion stage 20 may also include diaphragm extrusion, in which case the extrusion unit may be a diaphragm such as a rubber diaphragm. The extrusion unit presses the filter cake 14 against the filter medium, thereby extruding filtrate 16 from the cake through the filter medium. The filtrate can be discharged again from the filtrate collection area 122. The extrusion pressure can be generated by the extrusion fluid 22, which may be a gas or liquid such as air and / or water. For this purpose, the pressure filter may include one or more extrusion fluid channels 140 for guiding the extrusion fluid against the extrusion unit. The extrusion pressure may correspond to a pressure differential, which is the difference between the overpressure within the pressure filter and atmospheric pressure, or delta-pressure, such as the pressure difference between the nominal extrusion pressure and the feed manifold pressure.

[0042] The washing stage 30 includes conveying a washing medium 32, such as a liquid, into one or more filter chambers 102 to wash the filter cake 14. For this purpose, one or more distribution channels 120, the same as those used to guide the feed 12 into the one or more filter chambers, can be used. When the filter chamber is full of washing medium, the pressure applied to the extrusion unit by the washing medium can be used to lift the extrusion unit from the filter cake 14. In the case of diaphragm extrusion, residual extrusion fluid 22 can be expelled through the diaphragm. Again, the filtrate of the pressure filter 100 can be discharged from the filtrate collection area 122, in which case the filtrate is the washing filtrate 36.

[0043] The solid-liquid separation process may also include one or more separate stages for washing one or more distribution channels 120.

[0044] The drying stage 40 includes conveying a drying medium 42, such as a drying gas, into one or more filter chambers 102 to dry the filter cake 14. For this purpose, one or more distribution channels 120, the same as those used to guide the feed 12 into the one or more filter chambers, may be used. In particular, air may be used for drying, in which case the drying medium may include or consist of compressed air. The pressure filter 100 may include one or more compressors, such as an air compressor, for conveying the drying medium into the one or more filter chambers. The pressure filter may be configured to convey the drying medium into the one or more filter chambers within a set drying time, which is variable in subsequent drying stages of subsequent operating cycles, i.e., from one operating cycle to another. The drying time may thus correspond to the time that the compressor of the pressure filter is used to dry the filter cake for solid-liquid separation. When the filter chamber is full of drying medium, the extrusion unit may be lifted from the filter cake 14 by the pressure applied to it by the drying medium. For diaphragm extrusion, residual extrusion fluid 22 may be expelled through the diaphragm. The filtrate 16 may be discharged again from the filtrate collection area 122, for example, by the flow of the expelled drying medium. The flow of the drying medium through the cake reduces its moisture content.

[0045] After drying stage 40, filter cake 14 may be discharged from filter chamber 102. However, pressure filters may include one or more weight sensors, such as pressure sensing elements, to provide an indication of the weight of filter cake 14 after drying stage 40, for example, just before the cake is discharged from the filter chamber or pressure filter together.

[0046] Figure 1b A solid-liquid separation is illustrated according to another example using a pressure filter 100 (in this figure, the pressure filter is also shown as part of a pressure filter plate assembly). In this example, the pressure filter is a vertical pressure filter such as an FFP filter. Further illustration is provided according to a double-sided filter. In the illustrated example, four filter chambers 102 have been integrated to guide the feed into the filter chambers using the same distribution channel.

[0047] Here, solid-liquid separation may include... Figure 1a The same operational phase referred to in the context, and may also include any combination of the functional and / or structural features mentioned therein.

[0048] Regarding the one or more washing stages 30, it should be noted that the washing medium 16 may be fed into one or more filter chambers 102 via the same one or more distribution channels used to guide the feed 12 into one or more filter chambers, and / or via one or more additional channels such as corner channels 150. Only the latter option is shown in the figure. The additional one or more channels may also be configured to discharge filtrate 16, 36 during one or more other operating stages of the pressure filter. The additional one or more channels may be configured to discharge washing filtrate 36 during the washing stage according to the first selection, since these channels are not used to deliver washing medium in this stage. Solid-liquid separation may also include a first washing stage and a second washing stage, in which the washing medium is fed into one or more filter chambers via the same one or more distribution channels used to guide the feed into one or more filter chambers, and in the second washing stage, the washing medium is fed into one or more filter chambers via one or more additional channels. The first washing stage may be after the filtration stage 10 and before the (first) compression stage 20.

[0049] For a vertical pressure filter, the extrusion unit 130 may be kept active through one or more stages other than the extrusion stage 20. As shown, the extrusion unit 130 may be kept active through one or more washing stages 40 and / or drying stages 40. Accordingly, the extrusion fluid 22 may be held in one or more extrusion fluids 140 through one or more corresponding stages. The delivery of the extrusion fluid may also be maintained to maintain the extrusion pressure.

[0050] The pressure filter may include one or more drying channels for conveying drying medium 42 into one or more filter chambers 102 to dry the filter cake 14. For this purpose, additional channels such as corner channels 150 may be used, particularly channels for conveying washing medium 16 into one or more filter chambers.

[0051] A vertical pressure filter may include one or more vertical discharge channels 160 for discharging one or more filter cakes 14. These channels may be separate from one or more distribution channels 120 for guiding feed 12 into one or more filter chambers. One or more vertical discharge channels may be opened to discharge filter cakes.

[0052] Figure 2An example apparatus 200 for controlling a pressure filter 100 is shown. With this apparatus, an indication of the moisture content of the filter cake 14 produced by the pressure filter is received and used to set the drying time of solid-liquid separation 210, wherein the solid-liquid separation may correspond to any of the examples of solid-liquid separation disclosed above with reference to FIG. 1. For solid-liquid separation, the apparatus is configured to control the drying medium by setting a drying time 220. For the same purpose, the apparatus may be configured to control the feed by setting a feed rate 222 for the pressure filter, and / or to control the extrusion unit by setting an extrusion amount 224 for the pressure filter. In one embodiment, the manipulated variable for the feed rate may correspond to the feed weight. Alternatively or additionally, one or more manipulated variables for the feed rate may correspond to the extrusion pressure and / or extrusion time. The apparatus may be further configured to control a washing medium, such as a washing liquid, by setting one or more control values, such as the washing time and / or the amount of the washing medium, for the washing stage 226. Further control values ​​are also possible. Any or all control values ​​can be provided as setpoints for control operations. One or more control values ​​can be automatically set so that different one or more control values ​​can be automatically used in two subsequent operating cycles. One or more control values ​​can directly correspond to control operations, and thus also to manipulated variables used for multivariate optimization or MPC. One or more manipulated variables can be used to control the pressure filter during any single operating phase.

[0053] Solid-liquid separation 210 is performed by pressure filter 100. As a result of the separation, filtrate 16 and filter cake 14 are produced. Device 200 is configured to provide one or more indications of the quality and / or efficiency of the solid-liquid separation, and to use one or more indications to set one or more control values, including at least drying time but optionally also feed rate, and / or extrusion rate or other control values. The device or pressure filter may include one or more weight sensors, such as a pressure-sensing element of the pressure filter, for controlling the feed rate. For example, in the absence of a weight sensor, the feed rate may also be controlled by means of delivery time and / or delivery pressure. The device or pressure filter may include a feed manifold pressure sensor and / or feed density sensor for controlling one or more controlled variables. The device or pressure filter may also include an extrusion pressure sensor for controlling the extrusion force. The device may also include one or more of a feed, drying medium, and washing medium flow transmitter for controlling one or more corresponding control values. Such additional instrumentation may help with performance evaluation and improve control accuracy. While any sensors, such as additional instruments, can be integrated into the filter, they are often more conveniently provided as a separate part of the device. For example, they can be configured to connect to a factory automation system. Any sensors separate from the pressure filter can be configured to transmit information to the filter via bus communication.

[0054] One or more indicators of the quality and / or efficiency of the solid-liquid separation 210 include at least an indication of the moisture content of the filter cake 14. This allows for effective quality control of the separation. Here, quality can refer to accurately achieving target values ​​for controlled variables such as moisture content relative to a filter cake or batch, and / or achieving uniformity of target values ​​across multiple batches of filter cake. The device 200 may include one or more moisture analyzers for providing an indication of moisture content. The aforementioned analyzers may include microwave analyzers for providing an indication of filter cake moisture content, but other alternatives, including capacitive sensors and / or near-infrared sensors for the same purpose, are also feasible. The one or more moisture analyzers may be part of the pressure filter 100, or they may be independent. The moisture content indication can be obtained by measuring the filter cake along its entire length and calculating an average value for control. It has been found that significant benefits can be obtained when measuring moisture content with an accuracy of ±0.5 w%.

[0055] One or more indications of the quality and / or efficiency of the solid-liquid separation 210 may also include various other indications, particularly an indication of the operating capacity of the pressure filter, which may be obtained using an indication of the weight of the filter cake produced by the pressure filter. Any sensors used to obtain one or more indications, including weight sensors for providing weight indications, may be part of the pressure filter 100, or they may be independent. The indication of operating capacity may be expressed by the weight of the filter cake produced by the pressure filter over time, for example, in tons per hour.

[0056] One or more indicators can be obtained automatically. One or more indicators can be obtained 230 by one or more measurements of the filter cake 14 after solid-liquid separation 210 or its drying stage 40. Alternatively or additionally, one or more indicators can be obtained by one or more measurements of the filter cake 14 before the cake is discharged from the filter chamber or from the pressure filter 50. In particular, a weight indication of the filter cake 14 can be conveniently obtained while the filter cake is still in the filter chamber, at which point the pressure filter includes one or more weight sensors, such as pressure-measuring elements for this purpose. On the other hand, the apparatus may include weight sensors, such as a conveyor belt scale, for obtaining a weight indication after the filter cake is discharged from the filter chamber or pressure filter. For example, an indication of moisture content can be obtained before and / or after the filter cake is discharged from the filter chamber or pressure filter. The apparatus may also include one or more timers for determining one or more indications of duration. The one or more indications of duration may correspond to the duration of one or more stages of solid-liquid separation 210, or the total duration of separation. For example, by dividing the indication of filter cake weight by the indication of the total duration of solid-liquid separation, one or more indications of duration can be used to obtain an indication of the operating capacity of the pressure filter. One or more indications of duration can also be used to control the delivery time and / or squeezing time.

[0057] Since any or all indicators are available from the existing filter cake 14 after solid-liquid separation 230, they can be used to set one or more control values ​​for any subsequent batch. The moisture content indicator of the filter cake and the operating capacity indicator of the pressure filter can be obtained from the same batch or specifically from the same filter cake 14. However, indicators from multiple different batches can also be used together, for example, as an average value.

[0058] The device is configured to set one or more control values ​​for manipulating variables using one or more indicators of the quality and / or efficiency of the solid-liquid separator 210. The device may include one or more controllers configured for this purpose. For example, the pressure filter 100 may include its own controller capable of performing any or all of the operations disclosed in this specification. Alternatively, the pressure filter may include a sub-controller that receives one or more control values ​​from a main controller, the sub-controller being used to set one or more control values ​​for its own operation, thereby forwarding only the one or more control values ​​set by the main controller. The separation of one or more controllers from one or more sub-controllers and one or more main controllers allows for remote control of the pressure filter.

[0059] Controlling the solid-liquid separator 210 using one or more indicators involves determining an optimized set of one or more control values ​​for the pressure filter 100. Figure 2This is illustrated as filter optimization 240, which involves setting one or more control values ​​for manipulating variables using one or more indicators of the quality and / or efficiency of solid-liquid separation 210. One or more controllers may be configured to perform filter optimization, for example, by setting one or more control values ​​via a main controller. If necessary, the device and the one or more controllers may be configured to pass one or more control values ​​to the pressure filter. Finally, one or more controllers may be configured to locally set control values ​​for performing solid-liquid separation at the pressure filter, which may be performed, for example, by a sub-controller of the pressure filter. This corresponds to locally setting control values ​​for the filter operation sequence 250 of the pressure filter.

[0060] Figure 3 A control system for controlling a pressure filter 100 is shown according to an example. The control system may include or consist of one or more controllers for setting the drying time for solid-liquid separation using an indication of moisture content. The one or more controllers may include sub-controllers and a main controller, wherein the sub-controllers are local process controllers of the pressure filter and may be directly integrated into the pressure filter, while the main controller is located remotely from the pressure filter. The main controller may be configured to control multiple pressure filters.

[0061] One or more controllers (e.g., a main controller) may be configured to receive one or more indications of the quality and / or efficiency of the solid-liquid separator 210, including an indication of the moisture content of the filter cake produced by the pressure filter 100 for solid-liquid separation. The one or more controllers may then be configured to use the one or more indications to set one or more control values, such as the drying time for solid-liquid separation. The one or more controllers (e.g., the main controller) may be configured to determine one or more control values ​​through multivariate optimization using the one or more indications. For this purpose, the corresponding one or more controllers may be multivariate controllers and / or model predictive control (MPC) controllers.

[0062] A multivariable controller responds to changes in one or more values ​​(CV) of one or more controlled variables while simultaneously setting one or more control values ​​(MV) for one or more manipulated variables. In multivariable control, there is not necessarily any direct relationship between a single controlled variable and a manipulated variable; a particular manipulated variable (e.g., drying time) may be directly adjusted to control a particular controlled variable such as an indication of moisture content. Alternatively, the controller output can be calculated as the result of optimizing a cost function. Here, the cost function may correspond to a sum that includes penalties for predictive control errors, actuator position tracking, actuator movement suppression, and violations of given constraints.

[0063] Controller tuning can be divided into two parts. The first part involves building a process model for each MV-CV relationship. This is accomplished by performing a step response test and modeling the measured response. During the step response test, the drying time and optional feed rate can be manually modified. The effect on agglomeration moisture can then be measured using a moisture analyzer, as disclosed in this specification. The accuracy of the moisture analyzer can be calibrated before performing the step response test. Step response tests for drying time and optional feed rate can be performed one by one so that all other variables in the filtration formulation remain constant during the test. The collection and analysis of feed samples can also be performed during the step response test. The second part involves parameterizing the controller cost function, i.e., describing how penalties are calculated and how these penalties are weighted together.

[0064] When calculating a new setpoint for an upcoming operating cycle, setpoints from previous cycles can be considered. Averaging over multiple cycles helps prevent rapid changes in the setpoint due to measurement errors or unexpected stops during the cycle. The same logic applies when the filter restarts after a stop. For example, three cycles can be executed until a new setpoint is calculated and the filter is put into use.

[0065] For example, the extrusion stage can be optimized based on the pressure difference between the extrusion pressure and the feed manifold pressure (i.e., incremental pressure). The controller can be configured to receive measurements of the incremental pressure and calculate a new setpoint for the incremental pressure based on its effect on the moisture content of the filter cake.

[0066] The main controller may include one or more server computers. Sub-controllers may include programmable logic controllers (PLCs) for the pressure filter. One or more controllers may include one or more human-machine interfaces (HMIs) through which users interact with one or more controllers.

[0067] For example, device 200 or pressure filter 100 itself may include sub-controllers 302 such as a PLC controller for pressure filter 100 and an optional HMI 304. These controllers may be coupled to filter control panel 300. Sub-controllers may be configured to connect to a main controller, which may include a server computer 312 and / or a distributed control system (DCS) 314, such as a distributed control system for a factory automation system. These may be located in automation room 310. The server may be provided with remote connectivity 316, which may include a firewall. This allows server 312 to connect to one or more remote workstations 330, for example, via an intranet, the Internet, or a cloud connection. Alternatively, the server may also have one or more local connections to one or more workstations 320, which may be located in the control room. Remote connectivity for controlling the pressure filter provides rapid support and fine-tuning of system parameters to resolve any issues and maximize performance.

[0068] Figure 4 A method for controlling a pressure filter 100 according to an example is illustrated. The method includes 410: receiving one or more indications of the quality and / or efficiency of a solid-liquid separator 210, including an indication of the moisture content of the filter cake produced by the pressure filter 100 for the solid-liquid separator 210. This may be performed or caused by one or more controllers (e.g., a main controller). The method also includes 420: utilizing one or more indications, including an indication of the moisture content for setting one or more control values, including the drying time of the solid-liquid separator.

[0069] The method allows for the calculation of one or more new setpoints for one or more manipulated variables as the performance of the pressure filter changes. Thus, during the drying stage, the use of the drying medium and compressed air can be optimized, thereby optimizing energy consumption. However, it is certain that for the pressure filter, optimization dynamics are not isolated stages, but can be significantly improved through multivariate optimization, including control values ​​for stages other than solid-liquid separation. Drying time can also be reduced by optimizing the extrusion rate and / or feed rate. One or more controllers can be configured to recalculate one or more control values ​​for one or more subsequent operating cycles of the pressure filter, for example, for a subsequent cycle. Accordingly, device 200 can be configured to automatically update one or more control values ​​for a new operating cycle (e.g., each operating cycle) of the pressure filter.

[0070] The apparatus and method disclosed herein allow for optimization of filter cake residual moisture by removing and retaining filter cake moisture relative to a target value. The primary manipulated variable is drying time, which has been found to have a significant impact on the residual moisture content of the filter cake. Filter cake moisture can be removed towards a given residual moisture setpoint (e.g., 8-30 wt%, where 8-15 wt% is suitable for mining applications, and 15-30 wt% is suitable for chemical applications, for example) by controlling the drying time between limit values.

[0071] It should be noted that an incomplete squeezing stage will not remove enough fluid bound to the filter cake formed during the filtration stage. Liquid removal via the drying stage increases the consumption of drying media such as compressed air and extends the operating cycle duration, which affects the overall capacity of the pressure filter. On the other hand, an excessively long squeezing stage can cause the cake to be over-compressed, making it difficult for the drying media to flow through it during the drying stage. Unnecessarily long squeezing stages also increase the operating cycle duration for solid-liquid separation. In many cases, squeezing can be optimized based on the pressure difference between the squeezing force and the pressure within a distribution channel, such as a distribution pipe. When free liquid is squeezed out of the filter cake, the fluid connection between these two pressure measurements is lost. Due to this phenomenon, the pressure in the distribution channel begins to drop. Depending on the application, squeezing can be stopped when a certain pressure difference is reached.

[0072] Controlling the feed rate has been found to significantly impact the operating capacity of pressure filters. While the limiting factor for the amount of feed pumped into the filter chamber is the chamber volume, the filter cake formed within also possesses other characteristics that limit filter capacity, including one or more of the following: cake thickness, feed time, compressibility, and flow resistance. Targeting maximum cake thickness may unnecessarily increase filtration time and affect subsequent extrusion and drying stages. Filter optimization involves calculating and optimizing the feed rate while minimizing delivery and drying times, taking into account the total capacity of the pressure filter throughout the solid-liquid separation process. Feed rate control can be conveniently achieved if the filter is equipped with one or more load cells.

[0073] The device and / or pressure filter may include at least one memory containing computer program code. At least one memory and computer program code may be configured to cause one or more controllers to perform any operation disclosed in this specification. In particular, this includes setting any one or more control values ​​and / or determining one or more control values ​​using any one or more indications.

[0074] One or more controllers may be implemented by software, hardware, application logic, or a combination of software, hardware, and application logic. Application logic, software, or instruction sets may be stored on any of a variety of conventional computer-readable media. "Computer-readable medium" can be any medium or apparatus capable of containing, storing, transmitting, propagating, or transferring instructions for use by or in connection with an instruction execution system, apparatus, or device (such as a computer). Computer-readable media may include computer-readable storage media, which can be any medium or apparatus capable of containing or storing instructions for use by or in connection with an instruction execution system, apparatus, or device (such as a computer). Examples include storing information relating to the various processes described herein. This information may be stored in one or more memories such as a hard disk, optical disk, magneto-optical disk, RAM, etc. One or more databases may store information used to implement embodiments. Databases may be organized using data structures (e.g., records, tables, arrays, fields, graphs, trees, lists, etc.) contained in one or more memories or storage devices listed herein. Databases may reside on one or more devices, including local and / or remote devices such as servers. The processes described in connection with the embodiments may include appropriate data structures for storing data collected and / or generated by the processes of the devices and subsystems of the embodiments in one or more databases.

[0075] Those skilled in the computer and / or software art will recognize that all or part of the embodiments can be implemented using one or more general-purpose processors, microprocessors, digital signal processors, microcontrollers, etc., programmed according to the teachings of the embodiments. Those skilled in the software art will recognize that, based on the teachings of the embodiments, programmers of ordinary technology can easily prepare suitable software. Furthermore, those skilled in the electrical art will recognize that the embodiments can be implemented by fabricating application-specific integrated circuits or by using suitable networks to interconnect conventional component circuits. Therefore, the embodiments are not limited to any particular combination of hardware and / or software.

[0076] The different functions discussed in this manual may be executed in different orders and / or simultaneously with each other.

[0077] Unless otherwise stated, any range or device value given in this specification may be extended or modified without losing the desired effect. And unless expressly prohibited, any example may be combined with another example.

[0078] Although the subject matter has been described in structural and / or action-specific language, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific or foregoing features or actions. Rather, the specific features and actions described above are disclosed as examples of implementing the claims, and other equivalent features and actions are intended to fall within the scope of the claims.

[0079] It should be understood that the above benefits and advantages may relate to one embodiment or several embodiments. The embodiments are not limited to those that solve any or all of the described problems or have any or all of the described benefits and advantages. It will be further understood that a reference to "a" may refer to one or more of these items.

[0080] The term "comprising" is used in this specification to mean including identified methods, blocks, or elements, but such blocks or elements do not include an exclusive list and methods or apparatus may include additional blocks or elements.

[0081] While the invention has been described in conjunction with specific types of devices and / or methods, it should be understood that the invention is not limited to any particular type of device and / or method. Although the invention has been described in conjunction with numerous examples, embodiments, and implementations, it is not limited thereto, but rather covers various modifications and equivalent arrangements falling within the scope of the claims. While various examples have been described above with some degree of specificity or with reference to one or more individual embodiments, those skilled in the art can make various changes to the disclosed examples without departing from the scope of this specification.

Claims

1. An apparatus for controlling a pressure filter, the apparatus comprising: Pressure filters are used for solid-liquid separation to produce a filter cake. A moisture analyzer is used to provide an indication of the moisture content of the filter cake; One or more controllers are used to set the drying time for solid-liquid separation using an indication of moisture content. At least one memory containing computer program code, wherein the at least one memory and the computer program code are configured to cause one or more controllers to: After solid-liquid separation of the filter cake, an indication of moisture content is obtained from the existing filter cake; One or more control values ​​are set for subsequent batches processed by the pressure filter using an indication of moisture content.

2. The device according to claim 1, wherein, The moisture analyzer includes a microwave analyzer, a capacitive sensor, or a near-infrared sensor.

3. The apparatus according to any of the preceding claims is configured to set the drying time using an indication of moisture content provided by more than one solid-liquid separation cycle through the pressure filter.

4. The device according to any of the preceding claims, wherein, The one or more controllers include multivariable controllers.

5. The device according to any of the preceding claims, wherein, The one or more controllers include multivariable model predictive control (MPC) controllers.

6. The device according to any of the preceding claims is configured to additionally use an indication of moisture content to set the squeezing amount of the pressure filter.

7. The device according to any of the preceding claims, comprising one or more weight sensors for providing an indication of the weight of the filter cake.

8. The device according to any of the preceding claims, wherein, The pressure filter includes one or more pressure sensing elements for providing an indication of the weight of the filter cake.

9. The device according to claim 7 or 8 is configured to additionally utilize a weight indication to set the feed rate for the pressure filter.

10. The apparatus according to any of the preceding claims is configured to simultaneously use an indication of moisture content and an indication of the operating capacity of the pressure filter to set the drying time, and optionally the feed rate and / or the extrusion rate for the pressure filter.

11. The device according to any of the preceding claims, wherein, The solid-liquid separation includes a washing stage, and the device includes one or more sensors for providing indications of the quality of the washing stage to set drying time and / or control values ​​for washing the filter cake.

12. The device according to any of the preceding claims, comprising one or more sensors for providing indications of the pH, conductivity, or turbidity of the filtrate produced by the pressure filter, to set control values ​​for drying time and / or washing the filter cake.

13. A method for controlling a pressure filter used for solid-liquid separation, the method comprising: Receive an indication of the moisture content of the filter cake produced by the pressure filter used for solid-liquid separation; as well as Use moisture content indicators to set the drying time for solid-liquid separation; Specifically, after solid-liquid separation of the filter cake, an indication of moisture content is obtained from the existing filter cake; and One or more control values ​​are set for subsequent batches processed by the pressure filter using an indication of moisture content.

14. The method of claim 13, further comprising receiving an indication of the weight of the filter cake; wherein, The weight indication, along with the moisture content indication, is used to set the drying time, the feed rate of the pressure filter, and optionally the extrusion rate of the pressure filter.

15. A controller configured to cause the method of claim 13 or 14 to be performed.

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