System and method for controlling the screening of a flow of ore, and computer-readable medium
Patent Information
- Application Number
- PCT/BR2025/050580
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-25
- Filing Date
- 2025-12-15
- Publication Date
- 2026-09-03
Smart Images
Figure BR2025050580_03092026_PF_FP_ABST
Abstract
Description
SYSTEM AND METHOD FOR CONTROLLING ORE FLOW SCREENING AND COMPUTER-READABLE STORAGE MEDIUM FIELD OF THE INVENTION
[0001] The present invention relates to a method and system for controlling screening devices to increase the efficiency of mineral processing. More specifically, the invention relates to a control system for mining and mineral processing, more specifically to the optimization of the screening process at natural moisture content. FUNDAMENTALS OF THE INVENTION
[0002] Processing iron ore at its natural moisture content offers economic, environmental, and operational advantages. This is due to the simplification of processes, generally involving comminution, classification, and handling steps. However, this method, combined with climate and variations in ore type, leads to processing challenges, mainly due to the high moisture content. This situation frequently results in operational shutdowns due to overloads, blockages, and reduced efficiency.
[0003] According to Luz, ABd and Lins, FAF (2018) - Introduction to mineral processing, the mineral processing process consists of developing operations on mineral resources with the objective of modifying their particle size and the concentration of mineral species, but without altering their chemical or physical identity. In general, the treatment is carried out through unit operations, the most common being: classification, handling, comminution, and concentration. The iron ore industry processes ore with particles of different sizes. Therefore, size classification is an important step necessary for the particle size control in the feeding of unit operations, as it contributes to ensuring greater efficiency in subsequent stages of the process. The definition of screening can be found in Chaves, AP and Peres, AEC.(2003) - Theory and practice of mineral processing: Crushing, screening and grinding as the operation of separating a population of particles into two different fractions, by presenting them to a template with a fixed and predetermined opening. The term screening efficiency is defined in Andery, P. (1980) - Mineral processing and hydrometallurgy. VII National Meeting on Mineral Processing and Hydrometallurgy, Recife, as the ratio between the quantity of particles finer than the screen opening that pass through it, and the quantity of these particles present in the feed. Also according to Chaves and Peres (2003), industrially, a good screening efficiency is between 80% and 90%.
[0004] Screens are widely used equipment in crushing circuits, playing a significant role in process efficiency through good particle separation, delivering to the crushers the fraction of material that actually needs to be comminuted. In other variations of the process, they act by recirculating oversized material to be crushed and classified again, forming a closed circuit. Screening is said to be dry when it is done with the material in its natural moisture, and wet or wet-processed when the material is fed in the form of a pulp or receives additional water through sprays conveniently arranged on the screening decks (Chaves and Peres, 2003). Delfim, O.(2015) - The circular eccentric screen in the classification of iron ore with natural moisture indicates that in recent years, mining has been adopting classification with natural moisture as a replacement for wet classification for the processing of high-grade iron ore, with the aim of reducing costs and environmental impacts.
[0005] In a study to improve screening efficiency at natural moisture levels, Fonseca, AG (2022) - Fuzzy control for increasing screening efficiency in mineral processing, describes that during the screening process, some operational parameters can affect its performance, which can be divided into machine parameters, related to the equipment; and flow characteristics, related to the ore fed. Machine parameters can be exemplified by screen dimensions, deck material, vibration frequency, amplitude, acceleration and depend on the installed unit and the selected operational strategy. Flow characteristics include material properties such as distribution, particle size, shape, density and material flow rate, as cited by Asbjömsson, G., Bengtsson, M., Hulthéen, E., and Evertsson, M. (2016) - Model of banana screen for robust performance. Minerals Engineering.Another important aspect related to material flow that interferes with screening performance and capacity is moisture, that is, the percentage of water present in the sample. Free water on the surface tends to cause particles to adhere, reducing screening efficiency and directly impacting screening capacity, as described in King, RP (2001) - Modeling and simulation of mineral processing systems. Another effect that can occur with increased moisture is the "blinding" of the screening screens, preventing the passage of ore.
[0006] In these scenarios, the feed rate of the screen should be reduced, resulting in a reduction in the height of the material bed, to adjust the process to its actual capacity at the moment. As discussed in De São José, F., Junior, MLT, and Pereira, CA (2017) - Analysis of an iron ore screening route at the ITM of Namisa SA - a case study, there is a need for adaptation in screening circuits to meet the constant mineralogical and quality variations that directly affect the efficiency of the processes.
[0007] However, in plant operational routines, screening efficiency is still performed visually, meaning it's a sensitive process depending on the area technician's knowledge, or through sampling and laboratory analysis, which are carried out sporadically and without real-time response capability. Zhang, Y., Wang, X., Wang, J., and Zhang, Y. (2020) - Deep reinforcement learning based volt-var optimization in smart distribution systems, mention that industrially there are many operational scenarios that are not managed by control logics and that can lead to undesirable events, causing operational stoppages. The major difficulty is how to identify changes in process variables to manage them automatically. Seeking dynamic adaptation to process variations, Matos et al.(2021) propose a method to evaluate the degree of fragmentation of the ore on the conveyor belt resulting from the oversize screening using a two-dimensional laser scanner. In this way, the efficiency of this stage of the process is estimated, however, the acquisition and maintenance of the instrument is necessary.
[0008] Industrially, the use of instruments capable of evaluating the performance of screens in ore processing plants is not common. The most widely used method in industries is visual inspection of the screens and, through tacit knowledge, evaluation of screening efficiency. However, this evaluation depends on the inspector's knowledge and the moment they are evaluating the process, coupled with the availability of the team. Therefore, the great challenge for optimizing screening efficiency is to find ways to replace sensory techniques with automatic control strategies that adapt dynamically to process changes, generating stability and maximizing production without exceeding the equipment's protection limits.
[0009] Several techniques are known for controlling devices or processes for screening mineral materials. Some examples of screening control techniques are cited below.
[0010] The document WO2021058387A1 refers to a method for controlling and regulating a material flow screening device, wherein the method comprises: screening the material flow (rock or excavation) in at least one screening stage and regulating at least one vibration operating parameter of the screening device during operation. The control is performed based on a material input parameter from the following group: instantaneous material flow, particle size spectrum, particle geometry, moisture content, material composition or color, local distribution of material on the screen. The control in document WO2021058387A1 is performed in relation to a vibration operating parameter from the following group: vibration waveform, vibration amplitude, vibration frequency.Thus, it allows the vibration behavior to be adjusted according to the current material parameters (in particular as external effects) based on the characteristics of the material in flow, specifically in real time individually for each batch of material to be treated.
[0011] Document CN113219843B refers to an adaptive control system for controlling the dynamic load on the surface of a vibrating screen. The system includes a monitoring module and a control module. An adaptive control method is implemented, including monitoring the feed quantity with a feed sensor and, using the intelligent controller, obtaining a predefined initial motor speed to drive the motor and drop the material from the feed end onto the screen. Then, using each acceleration sensor to monitor the acceleration signal from the screen surface, the frequency and amplitude of the screen surface vibration are obtained in real time to adjust and adapt a machine learning model.Regarding control, if the dynamic load on the sieve surface exceeds a predetermined value, the CN113219843B intelligent controller controls the feed control device and the frequency converter. The feed control device adjusts the amount of feed to the sieve surface, and the frequency converter controls the motor to adjust the vibration frequency and amplitude.
[0012] Regarding control techniques, Fonseca (2022) presents a fuzzy control solution applied to a screening process consisting of parallel lines in an iron ore beneficiation plant, achieving increased screening efficiency through reduced circulating load and increased productivity. This document seeks to stabilize the processing by controlling the silos in the circuit, balancing the silos that store the material before the screen, thus avoiding circuit stoppages. The control acts based on the speed and feed rate of the screen.
[0010] As can be seen, the state of the art comprises several solutions related to screen control. However, as can be observed, none of the above documents describes a method that is specific to screening lines (primary or secondary), adjusting the screen feed according to the screen's momentary capacity.
[0011] Furthermore, the state of the art does not present a solution that regulates the activity of the screen according to the lithological characteristics of the fed material, where the material with greater processing capacity does not alter the feeder, while the material with less processing capacity alters the feeder to limit the feed according to the momentary capacity of the screen. SUMMARY OF THE INVENTION
[0012] The present invention aims to provide a system and a method for controlling sieves that provides increased productivity, increased operational efficiency and sieve lifespan, and reduces exposure to risks (health and safety) related to shutdown events due to overloads and obstructions in the circuit, where manual intervention is necessary.
[0013] Another objective of the present invention is to provide a system and a method of control to optimize performance and reduce operational downtime caused by overloads.
[0014] Another objective of the present invention is to implement a control system capable of reducing the occurrence of unwanted shutdown events due to overloads, as well as increasing the operating time in automatic mode.
[0015] In order to achieve the objective described above, the present invention provides a system for controlling ore flow screening comprising: at least one feeder configured to feed a material stream; at least one screening device configured to process the material stream from the feeder; and at least one material flow processing controller comprising: a product rate controller configured to determine a first reference speed value of at least one feeder as a function of the product rate; at least one current controller configured to determine a second reference speed value of at least one feeder as a function of the electric current of at least one screening device;and at least one minimum point selector to select the feeder reference value from among the first feeder speed reference value, the second feeder speed reference value, and a predetermined material classification reference value; wherein the material flow processing controller is configured to control the speed of at least one feeder based on the value selected by the minimum point selector.
[0016] The present invention also provides a method for controlling ore flow screening, the method comprising: to feed a material stream through at least one feeder; to process the material flow using at least one screening device; To determine, using a product rate controller, an initial reference speed value for at least one feeder as a function of the product rate; To determine, by means of at least one current controller, a second reference speed value for at least one feeder as a function of the electric current of at least one screening device; Select, using at least one minimum point selector, the lowest feeder reference value from among the first feeder speed reference value, the second feeder speed reference value, and a predetermined material classification reference value; and Control the speed of at least one feeder based on the value selected by the minimum point selector.
[0017] The present invention also relates to a computer-readable storage medium comprising a set of computer-readable instructions which, when executed on a processor, cause the computer to perform the method of the present invention. BRIEF DESCRIPTION OF THE FIGURES
[0018] The detailed description presented below refers to the attached figures and their respective reference numbers.
[0019] Figure 1 illustrates a flowchart for sinter feed beneficiation.
[0020] Figure 2 illustrates a schematic of primary screening control.
[0021] Figure 3 illustrates a schematic of primary screening control according to the present invention.
[0022] Figure 4 illustrates a sieveability test graph. DETAILED DESCRIPTION OF THE INVENTION
[0023] First, it should be noted that the description that follows will be based on a preferred embodiment of the invention. As will become evident to anyone skilled in the art, however, the invention is not limited to this particular embodiment.
[0024] The present invention provides a system for controlling ore flow screening comprising: at least one feeder configured to feed a material stream; at least one screening device configured to process the material stream from the feeder; and at least one material flow processing controller comprising: a product rate controller configured to determine a first reference speed value of at least one feeder as a function of the product rate; at least one current controller configured to determine a second reference speed value of at least one feeder as a function of the electric current of at least one screening device;and at least one minimum point selector to select the feeder reference value from among the first feeder speed reference value, the second feeder speed reference value, and a predetermined material classification reference value; wherein the material flow processing controller is configured to control the speed of at least one feeder based on the value selected by the minimum point selector.
[0025] The present invention also provides a method for controlling ore flow screening, the method comprising: to feed a material stream through at least one feeder; to process the material flow using at least one screening device; To determine, using a product rate controller, an initial reference speed value for at least one feeder as a function of the product rate; To determine, by means of at least one current controller, a second reference speed value for at least one feeder as a function of the electric current of at least one screening device; Select, using at least one minimum point selector, the lowest feeder reference value from among the first feeder speed reference value, the second feeder speed reference value, and a predetermined material classification reference value; and Control the speed of at least one feeder based on the value selected by the minimum point selector.
[0013] Based on a statistical correlation analysis, using industrial data for the screening process, the inventors verified a correlation between screen parameters and the material to be screened. The correlation was verified between the electric current (A) of the screen drive and the physical, chemical, and lithological characteristics of the ore. Based on the results of this correlation, the present invention proposes a new regulatory rate control, using the override strategy, to protect and adjust the process dynamically, replacing the manual intervention of the operational team based on the use of this screen current variable to implement it.
[0014] For a better understanding of the present invention, a flowchart of a mineral processing system will first be presented. In this description, a simplified sinter beneficiation process will be considered. Equipment and flowchart for mineral processing.
[0015] Figure 1 illustrates a simplified sinter feed beneficiation flowchart. The ore treatment involves comminution (particle reduction) and classification (size separation) by screening in open and closed circuits. This route includes intermediate storage and final product stockpiles connected by conveyor belts.
[0016] The process begins in stockpiles 01 and 02, which mark the transition between the mine and the processing plant. The ore is fed from stockpiles 01 and 02 to long-reach belt conveyors (LTBCs) 03, which take it to the primary screening and secondary crushing stage. In this stage, there are six parallel lines, each with a silo 04, a feeder 05, a screen 06, and a crusher 07. Processing is carried out in each line as follows: the ore from silo 04 is fed to screen 06 via feeder 05. Screen 06 processes the ore flow so that the fine material goes to subsequent stages, while the coarser material goes to crusher 07. Then, the processed ore is directed to the leveling yard 08 or to secondary screening and tertiary crushing, according to the operational strategy adopted.
[0017] Primary screening is carried out using banana-type vibrating screens with linear movements. Each screen is driven by a motor, operating through a frequency inverter and using a spring damping system. Banana-type screens have a certain curvature and inclination, resulting in high drag speeds and aiming to achieve high ore processing rates, even with a high concentration of fines, without losing screening efficiency. The screens in question have three sections with different angles of inclination, with a difference of 5 between the sections. oThe high initial angle imposes high velocity on the ore, decreasing the thickness of the ore layer and thus reducing the amount of fines. In the following sections of the screen, the ore velocity decreases and the residence time increases, resulting in the removal of the remaining fines. Low screening efficiency tends to retain a lot of ore in the last part of the screen, where the drag velocity is lower, which can overload the equipment and increase the strain on the drive motor. An experienced technician can identify this problem and adjust the screen feed rate, thus minimizing this negative effect on the process. Primary screening control system
[0026] According to systems already known in the art, the primary screening control system in a flowchart like the one in Figure 1 can be built on an override control structure, capable of automatically identifying the main process constraints and dynamically adjusting the product setpoint or directly intervening in the feeder speed. In this control structure, it is also possible to allow manual interventions to limit the feeder speed based on field evaluation of screening conditions by operators. Figure 2 illustrates a primary processing control strategy with an override control structure according to the state of the art.
[0027] The main objectives of this control strategy are: • To offer safe operating conditions, reducing the risk of overloading transport equipment; • To promote continuous and optimized operation, always seeking to utilize the available processing capacity, which varies according to process conditions; and • Regulate the product rate at the exit of the Primary Screening, subject to restriction by low average level in the Screening silos (process restriction) and by the nominal and process capacity of the subsequent stage (secondary screening).
[0028] Therefore, the control strategies used involve controlling the feeder speed by monitoring parameters such as silo levels, the capacity of the product destination after processing, and the product rate, using controllers with corresponding structures.
[0029] With this strategy, in the absence of any process restriction, the setpoint (SP) value of the Product Rate Controller 20 of the sieves assumes the value determined by the operator, which is established in this control architecture as the maximum setpoint allowed for the circuit. In case of activation of any restriction, that is, if any process variable exceeds the established limits, the controller in question will adjust the setpoint in an effort to regulate the process and allow its operational continuity at the maximum possible production rate, without exceeding the safety and interlock limits.
[0030] This switching between available selections occurs within the concept of the override structure, where the selected controller is the one that presents the lowest value in the Controller Output (CO). This task is performed by a minimum selector logic block 13, which has as inputs the OP of the level controller 10, the target capacity controller 11, and the maximum value defined by the operator 12. The output of the minimum selector logic block 13 is simply the lowest value among the inputs. The controllers used in this arrangement are the well-known and widely used PI (proportional and integral) controllers. Then, the screening product rate controller 20, also a PI controller, is responsible for the regulatory layer, according to the setpoint defined by the override structure.
[0031] The main feature of the product rate controller 20 is that it works with an estimated Process Variable (PV), instead of the actual value read from the rate measurement instrument. In this case, the product rate estimator 14 is fed by an integrating scale positioned downstream in the ore processing circuit. The product rate estimator 14 is used to eliminate process dead time caused by the distance between the feeders and the scale, allowing for a faster response to setpoint changes. Basically, this estimated process variable is the result of multiplying the sum of the actual feeder velocities by a gain. This gain, known as the feeder gain, is dynamically updated and its value is defined by the ratio of the rate to the sum of the time-delayed velocities, considering the scale's position in the process.
[0032] Continuing with the strategy, the output of the product rate controller 20 is connected to another minimum selector block 21, 22, which is responsible for defining the feeder speed, thus forming another override structure. This structure has as inputs the CO from the product rate controller 20 and a manual input 23 used to restrict the feeder speed when the presence of a difficult-to-classify material is detected in the field.
[0033] Under normal operating conditions, i.e., without active restriction in the minimum selector block of feeders 21, 22, they operate at a speed equal to and defined by the output of the product rate controller. In situations of necessity (related to the screening efficiency observed in the field), the operator can set a limit value for the feeder speed, thus restricting the action of the rate controller. Control system and method according to the present invention.
[0034] The following describes a system for controlling ore flow screening according to the present invention, applied to a beneficiation system comprising at least one feeder 05 for feeding a material stream comprising ores and having at least one screening device 06 configured to process the material stream. As will be evident to a person skilled in the art, the present invention relates to a control system in screening lines, whether primary or secondary screening as exemplified above.
[0035] The present invention proposes a material flow processing controller formed by a new implemented control structure, as illustrated in Figure 3, which expands the feeder speed definition override structure.
[0036] Thus, the controller according to the present invention comprises a product rate controller 20 configured to determine a first reference speed value of at least one feeder 05 as a function of the product rate, as in Figure 2.
[0037] This structure, in turn, now also includes a high-current controller for screens 30 and 31, which will take control of the feeder speed if the current limit is exceeded. The objective is to regulate the process, reducing and adjusting the screen feed rate to meet the ideal capacity at any given moment. With this control scheme, it is possible to dynamically avoid overload operations and low screening efficiency, adjusting the maximum supported rate for each situation and responding in real time to variations in the material's lithology.
[0038] For this new current controller, implemented as a PI controller, the parameters must be defined and adjusted according to practice, which can be done through industrial testing. The new control strategy was implemented in the primary screening and secondary crushing stage, which has six parallel screening lines. The new strategy, incorporated into the feeder speed definition, added a high-current screen controller, which will take control of the feeder speed if the current limit is exceeded. The objective is to regulate the process, reducing and adjusting the screen feed rate to meet the ideal capacity at any given moment. With this control scheme, it is possible to dynamically avoid overload operations and low screening efficiency, adjusting the maximum supported rate for each situation and responding in real time to variations in the material's lithology.For this new current controller, implemented as a proportional and integral PI controller, the parameters were defined and adjusted through industrial testing and are presented below. It is worth noting that the parameters are the same for all six screening lines, as they are composed of the same equipment.
[0018] Considering the override control structure, the current controller 30, 31 determines a reference speed value for at least one feeder 05 as a function of the electrical current of at least one screening device 06, which will be considered if it is determined as the lowest reference value. For this purpose, a minimum point selector 21, 22 selects the lowest feeder reference value from among the first feeder speed reference value, the second feeder speed reference value, or a predetermined material classification reference value determined by the operator.
[0019] It is observed that the embodiment described herein of the present invention is implemented in a material flow processing controller applied in primary screening control. However, as will be evident to a person skilled in the art, the present invention is not limited to this application and may be employed, for example, for secondary screening control.
[0020] It is emphasized that all the operating steps of the system according to the present invention described also apply to the present method. It is further noted that this method according to the present invention is implemented in a computer. The computer comprising at least one processor and a computer-readable storage medium, wherein the storage medium further comprises computer-readable instructions which, when executed by at least one or more processors, cause the computer to perform the method according to the present invention.
[0021] Thus, the example embodiments described herein can be implemented using hardware, software, or any combination thereof, and can be implemented on one or more computer systems or other processing systems. Additionally, one or more of the steps described in the example embodiments presented herein can be implemented, at least in part, by machines. Examples of machines that can be used to perform the operations of the example embodiments presented herein include general-purpose digital computers, specially programmed computers, desktop computers, server computers, client computers, laptops, mobile communication devices, tablets, and / or similar devices.
[0022] For example, an illustrative example system for carrying out the operations of the embodiments set forth herein may include one or more components, such as one or more processors or microprocessors, to perform the arithmetic and / or logical operations required for the execution of a computer program that performs the steps of the method described, and storage media, such as one or more disk drives or memory cards (e.g., flash memory) for storing the program and data, and a random access memory, for temporary storage of data and program instructions.
[0023] The system may also include software residing on a storage medium (e.g., a disk drive or memory card) which, when executed, directs the processor(s) or microprocessor(s) in performing the steps of the method. The software may run on an operating system stored on the storage medium, such as, for example, UNIX or Windows, Linux, Android and the like, and may adhere to various protocols, such as Ethernet, ATM, TCP / IP protocols and / or other connection-based or connectionless protocols.
[0024] As is well known in technology, microprocessors can run different operating systems, and can contain different types of software, each type being devoted to a different function, such as handling and managing data / information from a particular source, or transforming data / information from one format to another. The embodiments described here should not be interpreted as being limited to use with any particular type of server computer, and any other suitable type of device to facilitate the exchange and storage of information may be employed instead.
[0025] The embodiments of the method discussed in this document can be carried out by a computer program that can be provided as a computer program product, or software, which may include an article of manufacture on a non-transient machine-accessible or computer-readable medium (also referred to as “machine-readable medium”) containing instructions. The instructions on the machine-accessible or machine-readable medium can be used to program a computer system or other electronic device. The machine-readable medium may include, but is not limited to, floppy disks, optical discs, CD-ROMs, and magneto-optical disks or other type of machine-readable medium suitable for storing or transmitting electronic instructions.
[0026] The techniques described herein are not limited to any particular software configuration. They may be applicable in any computing or processing environment. The terms “machine-accessible medium,” “machine-readable medium,” and “computer-readable medium” used herein shall include any transient or non-transient medium that is capable of storing, encoding, or transmitting a sequence of instructions for execution by the machine (e.g., a CPU or other type of processing device) and that causes the machine to perform the method described herein. Furthermore, it is common in technology to speak of software, in one form or another (e.g., program, procedure, process, application, module, unit, logic, and the like), as taking an action or causing a result.Such expressions are merely a quick way of stating that the execution of software by a processing system causes the processor to perform an action to produce a result. Regarding the effects and advantages of the present invention
[0027] Having described the present invention in detail above, theoretical descriptions will be presented below in order to better substantiate the effects and advantages provided by the present invention.
[0028] First, the tests performed to ascertain the correlation between ore lithology and screen operation will be described below. Depending on the mining region, different types of lithologies can be found. The main lithologies found in the iron ore body of the studied mining region are divided into: hematites (friable, compact, goethite and manganiferous), cangas (chemical and structural), jaspelites (carbonatic, siliceous and chloritic) and mafic rocks (decomposed and sound). In daily operations, mine planning teams consider all jaspelites, mafic rocks and chemical cangas as waste. The ROM ores intended for feeding the plants consist of all hematites and structural cangas, depending on the physical conditions of the material, such as moisture.It is also necessary to control the so-called hydrated ores (cangas and hematite goethite), which present handling difficulties due to the low flowability of the ore (high abrasiveness, high cohesiveness and low angle of repose).
[0029] In order to evaluate the correlation between variables related to the ore and screening capacity and efficiency, laboratory tests were carried out, followed by statistical analyses with real plant data.
[0030] In order to understand the effects of lithologies and humidity, samples were collected at a processing plant for laboratory sieving tests, using the main lithologies found: • Friable Hematite (FH); • Goethitic Hematite (GOH); and • Structural Canga (CE). Table 1 - Chemical analysis by lithology
[0031] Based on the results of the chemical analyses in Table 1, it is possible to compare the main differences between the lithologies: • Comparing HF x HGO, it is noticeable that the main discrepancies are in the Fe content, which is higher in HF, and in the PPC (loss on ignition), which is higher in HGO; • Comparing HF x CE, it is noticeable that the main discrepancies are in the Fe content, which is higher in HF, and in the PPC and A12O3 content, which is higher in CE; • Comparing HGO and CE, the main discrepancies are the higher Fe content in HGO, and the higher P and Al2O3 content in CE. Table 2 - Mineralogical composition
[0032] Table 2 shows the mineralogical composition of the samples, where sample HF has a predominance of hematite in its mineralogical composition, with smaller proportions of goethite, magnetite, and contaminating minerals such as quartz and Mn oxides. Samples HGO and Ce have a predominance of goethite, which is consistent with the PPC values obtained in the chemical analysis.
[0033] Considering the main chemical and mineralogical characteristics of each lithology, tests were conducted on a circular sieve that allows simulating a continuous sieving process, obtained by the constant circulation of the fed ore along the sieve. In these tests, the lithology and moisture content of the material were varied. The endless linear motion sieve was used for the purpose of calculating the capacity factor in t / h / m. 2For various applications, corresponding to the unit screening rate on an industrial scale. This approach allows determining the critical moisture content for screening and performing simulations to evaluate the influence of factors such as acceleration, layer height, screen type, and barriers during screening with natural moisture. For the test, blends were created with HF, HGO, and CE samples, thus generating 8 different samples / mixtures, as listed below: Sample 1: 100% HF; Sample 2: 100% HGO; Sample 3: 100% CE; Blend 2: 60% HF, 20% HGO and 20% CE; Blend 3: 60% HF, 10% HGO and 30% EC; Blend 4: 60% HF, 40% HGO; Blend 5: 60% HF, 40% CE; and Blend 6: 30% HF, 20% HGO and 50% EC.
[0034] The results of the continuous sieving test are presented in Figure 4 and allow us to conclude that: Moisture levels above 8% negatively affect the sieving capacity of all samples, and levels above 12% cause saturation during sieving, except for HGO, which reached higher moisture levels. Reducing the %HF content in the blends resulted in a reduction in screening capacity; Increased EC and HGO, associated with increased humidity, leads to a reduction in capacity; and The sample with 100% CE showed the worst behavior in the sieving process.
[0035] For the analysis, real data from a beneficiation plant are being considered, referring to the processing of iron ore in the primary screening stage of the circuit, composed of 6 parallel screening lines. For this study, only the central lines, which have higher utilization compared to the end lines due to their favorable process layout, will be considered, making them more representative for analysis. Daily average data were collected from Jan / 22 to Dec / 22, excluding days with low operational yield and reduced production for the circuit. As a result, of the 365 days, 200 remained after excluding data considered outliers, totaling 3,473 hours of operation with effective load in the circuit.
[0036] With the data collected and after appropriate selection, Minitab software version 2018 was used for statistical analyses. For the statistical tests, a multiple correlation model was employed with the following variables: sieve feed rate, PPC (loss on ignition), H2O (ore moisture), IMH (hydrated ore index), and HGO (hematite goethite). The response variable was the sieve drive motor current. The test results revealed a correlation with a coefficient of determination (R-squared) of 43.05%. This correlation is considered significant, especially considering that the data were obtained over a year of industrial operation. Therefore, a correlation exists between the sieve motor current, the characteristics of the fed ore, and the sieve feed rate.
[0037] Thus, the invention as described above provides an override controller designed to improve the efficiency of primary or secondary screening in iron ore beneficiation plants. The solution works by varying the speed of the feeders, regulating the feed flow so that a certain current limit on the screen is not exceeded. This reduces downtime due to high current in the screens, increasing the level of equipment protection and reducing premature breakdowns due to high current, resulting in a process with a larger screening area. Another benefit is the ability to optimize the rate in difficult screening scenarios, leading to productivity gains and reduced operational downtime. Consequently, a more efficient and stable screening process is achieved.
[0038] The effect and advantages of the present invention can also be observed in comparison with other material flow processing control techniques.
[0039] The Fonseca (2022) document presents a technique that seeks to stabilize the processing process by controlling the silos in the circuit, balancing the silos that store the material before the screen, thus avoiding circuit stoppages. The control system operates based on speed, specifically the screen feed rate. The control system considers secondary screening, aiming to balance silo levels to achieve an optimal process, and is capable of preventing stoppages due to high or low levels. It constantly monitors the feeder distribution to avoid stoppages due to high or low levels. In other words, when a high silo level is detected, the feeder speed is increased to lower and balance the level; similarly, when a low silo level is detected, the feeder speed is decreased, increasing the silo level to balance it.
[0040] The present invention also aims to stabilize the screening process using the screen feed rate, but with the objective of stabilizing the electrical current of the screening device. The control system is geared towards the screening line, whether in primary or secondary screening, adjusting the screen feed according to the screen's momentary capacity. The screen has a dynamic capacity in the process, not a static capacity, varying its capacity according to the lithology of the material being fed. Thus, the present invention acts to regulate the screen activity according to these characteristics; material with a higher processing capacity does not alter the feeder, while material with a lower processing capacity alters the feeder to limit the feed according to the screen's momentary capacity.
[0041] The Fonseca system (2022) is configured to adjust the silo level to balance them, while the present invention respects the screening capacity of the screen.
[0042] According to the proposed control system, the adjustment is made through the sieve current, in order to identify the ore lithology according to the sieve current. The main advantages are the simplicity and efficiency of the design.
[0010] Numerous variations falling within the scope of protection of this application are permitted. Thus, it is reinforced that the present invention is not limited to the particular configurations / embodiments described above.
Claims
1. CLAIMS 1. System for controlling ore flow screening characterized by comprising: at least one feeder (05) configured to feed a material flow; at least one screening device (06) configured to process the feeder material flow; and at least one material flow processing controller comprising: a product rate controller (20) configured to determine a first reference speed value of at least one feeder (05) as a function of the product rate; at least one current controller (30, 31) configured to determine a second speed reference value of at least one feeder (05) as a function of the electric current of at least one screening device (06); and at least one minimum point selector (21, 22) configured to select the lowest feeder reference value from among the first feeder speed reference value, the second feeder speed reference value and a predetermined material classification reference value; where the material flow processing controller is configured to control the speed of at least one feeder (05) based on the value selected by the minimum point selector (21, 22).
2. System according to claim 1, characterized in that the current controller (30, 31) is configured to limit the second speed reference value of at least one feeder (05) to a predetermined current reference value.
3. System according to claim 1 or 2, characterized in that the material flow processing controller further comprises: a level controller (10) configured to determine a first product rate reference value based on the average level of available material silos, wherein the first product rate reference value of the level controller (10) is limited to a predetermined average level limit value of available material silos; a target capacity controller (11) configured to determine a second product rate reference value based on the back-circuit rate to at least one screening device (06), wherein the second product rate reference value of the target capacity controller (11) is limited to a predetermined back-circuit rate limit value; a minimum product rate point selector (13) configured to select the smaller value among the first product rate reference value, the second product rate reference value and a predetermined limit value (12).
4. System according to claim 3, characterized in that the system further comprises a product rate estimator (14) configured to estimate the product rate based on the weight of product conveyed by the feeder, wherein the product rate estimator (14) is connected to an integrating scale; and wherein the product rate controller (20) is configured to determine the second speed reference value of at least one feeder (05) based on the value selected by the minimum product rate point selector (13) and the product rate estimated by the product rate estimator (14).
5. Method for controlling ore flow screening, the method characterized by comprising: feeding a material flow through at least one feeder (05); process the material flow by means of at least one screening device (06); determine, by means of a product rate controller (20), a first reference speed value of at least one feeder (05) as a function of the product rate; determine, by means of at least one current controller (30, 31), a second reference speed value of at least one feeder (05) as a function of the electric current of at least one screening device (06); select, by means of at least one minimum point selector (21, 22), the lowest feeder reference value among the first feeder speed reference value, the second feeder speed reference value and a predetermined material classification reference value; and control the speed of at least one feeder (05) based on the value selected by the minimum point selector (21, 22).
6. Method according to claim 5, characterized in that the current controller (30, 31) is configured to limit the second speed reference value of at least one feeder (05) to a predetermined current reference value.
7. Method according to claim 5 or 6, characterized in that it further comprises: to determine a first product rate reference value, by means of a level controller (10), based on the average level of the available material silos, wherein the first product rate reference value is limited to a predetermined average level limit value of the available material silos; to determine a second product rate reference value, by means of a target capacity controller (11), based on the circuit rate after at least one screening device (06), wherein the second product rate reference value of the target capacity controller (11) is limited to a predetermined circuit rate limit value; select, by means of a minimum product rate point selector (13), the smallest value among the first product rate reference value, the second product rate reference value and a predetermined limit value (12).
8. Method according to claim 7, characterized in that it further comprises: estimate, by means of a product rate estimator (14), the product rate based on the weight of product conveyed by the feeder, wherein the product rate estimator (14) is connected to an integrating scale; and wherein the product rate controller (20) is configured to determine the second speed reference value of at least one feeder (05) based on the value selected by the minimum product rate point selector (13) and the product rate estimated by the product rate estimator (14).
9. Computer-readable storage medium, characterized in that it comprises a set of computer-readable instructions which, when executed on a processor, cause the computer to perform the method as defined in any one of claims 5 to 8.