A magnetic heavy medium recovery magnetic separation control method for coal mine processing

Abstract

The present application relates to the field of coal mine recovery magnetic separation control, and particularly relates to a magnetic heavy medium recovery magnetic separation control method for coal mine processing. After the coal slime accumulation indexes of the feeding section, the middle section and the discharge section are determined, the monitoring intensity of each section in the next magnetic separation cylinder discharge period is obtained; the initial value of the collection period is divided by the monitoring intensity of each section, and the collection period of each section in the next magnetic separation cylinder discharge period is obtained. Thus, the collection period of the monitoring point is dynamically adjusted according to the coal slime accumulation state of each section, redundant collection when there is no accumulation is avoided, sufficient sampling density when the accumulation is serious is ensured, the change of the coal slime accumulation state is captured more timely, and thus the adjustment and control are performed.

Description

Technical Field

[0001] This invention relates to the field of magnetic separation control for coal mine recovery, and specifically to a magnetic separation control method for recovering magnetic heavy media in coal mine processing. Background Technology

[0002] In coal washing and beneficiation processes, after the heavy medium suspension is recovered by magnetic adsorption in a magnetic separator, the remaining slurry containing coal slime is discharged from the separator and enters an overflow weir. Coal slime gradually accumulates at the weir opening, leading to localized blockage, a reduced overflow cross-section, a higher liquid level, and a lower flow velocity. This causes the slurry to overflow from the point where it hasn't accumulated, and in severe cases, unilateral flow deviation occurs, resulting in the heavy medium escaping along the higher side of the slurry, thus reducing magnetic separation recovery efficiency. In large coal preparation plants, the total length of the overflow weir is relatively longer, and the spatial variation in the distribution of coal slime accumulation along the weir is greater, making these problems more pronounced.

[0003] To address the aforementioned issues, some manufacturers have opted to install monitoring points within the weir body to monitor the overflow weir's outflow status in real time. They also rely on manual experience to periodically flush or adjust the overall height of the overflow weir. However, this approach has the following problems: First, the fixed sampling cycle of the monitoring points prevents dynamic adjustment of the sampling frequency based on the actual coal slime accumulation. This results in redundant sampling when there is no accumulation at the overflow weir, and insufficient sampling density when accumulation is severe, making it difficult to capture the accumulation conditions in a timely manner and thus hindering timely adjustments. Second, setting only one monitoring point in the middle of the weir body, or one at each of the inlet and outlet ends, to assess the overall overflow weir condition results in a large blind spot. This makes it impossible to identify local anomalies along the overflow weir. When local coal slime accumulation at the weir or flow deviation caused by narrowing of the flow cross-section occurs, timely intervention is impossible, leading to the escape of magnetic heavy media with the tailings and a decrease in recovery efficiency. Summary of the Invention

[0004] The technical solution adopted by the present invention to solve its technical problem is: a magnetic separation control method for recovering magnetic heavy media in coal mining, comprising the following steps: dividing the overflow weir along the slurry flow path into a feeding section, a middle section, and a discharge section; setting up monitoring points in each section, collecting the slurry liquid level height and overflow velocity during the discharge interval of the magnetic separator, and determining the coal slime accumulation position.

[0005] By comparing the slurry level and overflow velocity at adjacent monitoring points in each section, a flow difference sequence along the flow path is obtained; based on the flow difference sequence along the flow path and the real-time collected feed slurry flow rate, a basic control opening is generated.

[0006] The locations of coal slime accumulation in each section are summarized to obtain the overall coal slime accumulation distribution, and the opening compensation amount is generated at the same time. The basic control opening and the opening compensation amount are superimposed to obtain the final control opening.

[0007] The overflow height of the overflow weir is adjusted according to the final control opening. At the same time, the actual flushing frequency and actual flushing pressure are determined based on the location of the coal slime accumulation section in order to carry out high-pressure flushing.

[0008] Based on the slurry level and overflow velocity at each monitoring point, determine whether the overflow flow field has returned to uniformity; if so, lock the overflow weir height and stop high-pressure flushing.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. After determining the coal slime accumulation index of the feeding section, the middle section, and the discharge section, the present invention obtains the monitoring intensity of each section in the next magnetic separator discharge period; by dividing the initial value of the collection cycle by the monitoring intensity of each section, the collection cycle of each section in the next magnetic separator discharge period is obtained. Thus, the collection cycle of the monitoring point is dynamically adjusted according to the coal slime accumulation state of each section, avoiding redundant collection when there is no accumulation, and ensuring sufficient sampling density when the accumulation is severe, so as to capture the changes in the coal slime accumulation state more timely and thus carry out regulation.

[0010] 2. This invention first divides the overflow weir along the slurry flow path into a feeding section, a middle section, and a discharge section, and sets up multiple monitoring points in each section to form a continuous spatial coverage along the length of the overflow weir, reducing blind spots. By comparing the slurry level and overflow velocity at adjacent monitoring points, the outflow difference sequence along the overflow weir is obtained, thereby identifying local anomalies along the overflow weir and locating the coal slime accumulation position. Based on the section where the coal slime accumulation position is located, the actual flushing frequency and actual flushing pressure are determined to achieve targeted high-pressure flushing, which helps reduce the escape of magnetic heavy media with tailings and thus improves magnetic separation recovery efficiency. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0013] Figure 2 This is a flowchart illustrating the process of dividing the present invention into a feeding section, a middle section, and a discharging section.

[0014] Figure 3 This is a schematic diagram illustrating the process of generating the basic control opening degree for this invention;

[0015] Figure 4This is a schematic diagram of the process for determining whether the overflow flow field is uniform according to the present invention. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. Furthermore, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale.

[0017] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0018] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] The following describes in detail, with reference to the accompanying drawings, a specific scheme for a magnetic separation control method for recovering magnetic heavy media in coal mining provided by the present invention.

[0021] Please see Figure 1 and Figure 2 As shown, the present invention provides a magnetic separation control method for recovering magnetic heavy media in coal mining, including: step S1, dividing the overflow weir along the slurry flow path into a feeding section, a middle section, and a discharge section; setting up monitoring points in each section, collecting the slurry liquid level height and overflow velocity during the discharge interval of the magnetic separator, and determining the coal slime accumulation position.

[0022] In the heavy media recovery magnetic separation process, the slurry enters the magnetic separator from the upstream heavy media suspension tank via the feed pipe. After the magnetic heavy media is adsorbed and recovered within the separator, the magnetic separation operation is complete. The remaining slurry containing coal slime is discharged from the separator and enters the overflow weir. The slurry flows along the length of the overflow weir from the feed end to the discharge end, eventually overflowing from the weir opening in the discharge section and entering the tailings stream. Specifically, the overflow weir is in a standby state when the magnetic separator is performing magnetic separation operations; the slurry enters the overflow weir when the separator is discharging.

[0023] For the remaining slurry after magnetic separation, this embodiment monitors the liquid level and flow velocity in each section along the overflow weir to prevent the escape of heavy media due to local flow deviation.

[0024] The specific monitoring process is as follows: First, the flow rate of the feed slurry is read using an electromagnetic flowmeter installed on the feed pipe; then, the cross-sectional dimensions of the feed pipe are read from the equipment structural drawings. When the feed pipe is circular, the cross-sectional dimension is the inner diameter of the pipe; when the feed pipe is square, the cross-sectional dimension is the side length of the pipe. The cross-sectional area of ​​the feed pipe is calculated based on the inner diameter or side length of the pipe. The calculation process is existing technology and will not be elaborated here.

[0025] Next, the flow rate of the feed slurry is divided by the cross-sectional area of ​​the feed pipe to obtain the impact velocity of the feed slurry; the impact velocity characterizes the initial flow velocity of the slurry when it enters the overflow weir from the feed pipe.

[0026] During equipment commissioning or when changing coal types and batches, operators collect coal slime samples at the overflow weir inlet or the magnetic separator discharge port. These samples are then analyzed using a standard sieve to determine the particle size and density of the largest particles in the coal slime. Simultaneously, the density of the slurry is measured using a sampling and weighing method, and the viscosity is measured using a rotational viscometer or capillary viscometer. These measurement results are pre-written into the equipment process parameter table and can be directly accessed during operation.

[0027] Subsequently, according to Stokes' law of settling, the settling velocity of the largest particle is calculated using the following formula: Where v is the settling velocity of the largest particle, in m / s; g is the acceleration due to gravity, specifically taken as 9.8 m / s². ; This represents the density of the largest particle, expressed in kg / m³. d is the density of the slurry, in kg / m³; d is the particle size of the largest particle, in m; μ is the viscosity of the slurry, in Pa·s.

[0028] Next, the vertical height of the overflow weir from the bottom to the top surface is read from the equipment structural drawings and taken as the vertical height of the overflow weir. Then, the impact velocity is divided by the settling velocity, and the result is multiplied by the vertical height to obtain the maximum particle drift distance. The maximum particle drift distance represents the theoretical distance that the largest particles of coal slime drift horizontally with the slurry during the process of settling from the liquid surface to the bottom of the weir.

[0029] Multiplying the maximum particle drift distance by a safety factor yields the division length of the feed section. The feed section is the initial section of the overflow weir, used to buffer the impact of the incoming slurry and facilitate the initial settling of larger particles in the coal slime. Based on industry experience, the safety factor ranges from 1.1 to 1.5. When the slurry flow rate exceeds 100% of the rated flow rate, the safety factor should be adjusted to 1.4 to ensure that the largest particles settle sufficiently within the feed section. In this embodiment, the safety factor is specifically set at 1.2 to ensure that larger coal slime particles settle sufficiently within the feed section, preventing them from entering the middle and discharge sections. In practical applications, the safety factor can be adjusted adaptively according to the slurry flow rate.

[0030] Considering that when coal slime accumulates at the overflow weir, it directly reduces the flow cross-section of the weir, which in turn causes the slurry level to rise due to backwater and the overflow velocity to decrease due to the reduced flow cross-section, this invention reflects the accumulation intensity of coal slime from the two aspects of backwater level and flow capacity of the weir by measuring the slurry level height and the overflow velocity.

[0031] The specific calculation process is as follows: Read the design overflow velocity of the overflow weir from the equipment nameplate of the overflow weir, and read the opening width of the overflow weir in the horizontal direction from the structural drawings of the overflow weir, which is recorded as the weir opening width.

[0032] If the design overflow velocity is not recorded on the equipment nameplate, the rated flow rate and design liquid level height are read from the technical specifications of the overflow weir, and the overall length of the overflow weir body from the first end to the last end (i.e., the direction of slurry flow) is read from the equipment structural drawings and recorded as the total length of the overflow weir body; the rated flow rate is divided by the total length of the overflow weir body, and then divided by the design liquid level height, and the result is the design overflow velocity.

[0033] Next, the slurry viscosity is divided by the slurry density to obtain the kinematic viscosity of the slurry; the design overflow velocity is multiplied by the weir width, and the product is divided by the kinematic viscosity of the slurry to obtain the flow Reynolds number; based on the flow Reynolds number, the division length of the discharge section is determined.

[0034] It should be added that when the slurry flows in the overflow weir, it forms an overflow flow field. The discharge section is the end section of the overflow weir, used to allow the overflow flow field to fully develop into a uniform state before stable discharge. Therefore, the spatial length required for the overflow flow field to fully develop is used as the division length of the discharge section. The above spatial length depends on the flow state of the slurry in the overflow weir, which can be characterized by the flow Reynolds number. The specific process is as follows: When the flow Reynolds number is less than 1000, the overflow flow field is mainly laminar with less disturbance, and it can fully develop into a uniform state within a short distance. In this case, the first multiple of the weir width is taken as the division length of the discharge section. When the flow Reynolds number is greater than or equal to 1000, the overflow flow field is mainly turbulent with greater disturbance, and it requires a longer distance to fully develop into a uniform state. In this case, the second multiple of the weir width is taken as the division length of the discharge section to prevent local flow deviation and escape of heavy media due to insufficient development of the overflow flow field, which would lead to a decrease in magnetic separation recovery efficiency. Among them, one thousand is the engineering discrimination value of the Reynolds number of flow in the field of fluid mechanics; based on known engineering experience in fluid mechanics, the first multiple is specifically three times, and the second multiple is specifically five times.

[0035] After determining the division lengths of the feeding section and the discharge section, the division lengths of the feeding section and the discharge section are subtracted from the total length of the overflow weir to obtain the division length of the middle section. The middle section is the part between the feeding section and the discharge section, which is used for the continuous settling and overflow of smaller particles in the coal slime.

[0036] Based on the above calculations, the overflow weir body is divided into a feeding section, a middle section, and a discharge section along the direction of slurry flow. Furthermore, a one-dimensional coordinate axis is established with the head of the overflow weir body as the origin, along the direction of slurry flow, with the positive direction of the coordinate axis aligned with the direction of slurry flow.

[0037] The starting point of the feeding section is the origin, and the ending point is the length of the feeding section. The starting point and ending point of the middle section are the same, and the ending point is the sum of the lengths of the feeding and middle sections. Similarly, the starting and ending points of the discharging section are obtained. Then, the coordinates of the starting and ending points of each section are written into the controller configuration parameters for subsequent use.

[0038] It should be noted that when the coal type is changed in batches, the physical structure of the overflow weir is modified, or the viscosity and density of the feed slurry are adjusted, the length of each section is recalculated and the coordinates of the start and end points of each section are updated.

[0039] After dividing the feed section, middle section, and discharge section, several monitoring points are set up along the length of the overflow weir in each of the feed, middle, and discharge sections. Each monitoring point is equipped with an ultrasonic level gauge and an ultrasonic Doppler velocimeter. The probes of both the ultrasonic level gauge and the ultrasonic Doppler velocimeter are installed directly above the overflow weir opening, and the measurement target points of both probes are located at the same position on the slurry surface directly above the overflow weir opening, so that the slurry level height and overflow velocity reflect the overflow status at the same location.

[0040] The specific number of monitoring points in each section is determined based on the division length of the corresponding section. Specifically, the division length of each section is divided by the unit length, and the integer part of the result is taken as the specific number of monitoring points in the corresponding section. When the result is less than 3, the specific number is taken as 3.

[0041] Then, the coordinates of the monitoring points in each section are determined. Specifically, the sum of the number of monitoring points in each section and 1 is calculated to obtain the total number of spatial intervals between adjacent monitoring points in each section. The division length of each section is divided by the total number of spatial intervals in the corresponding section to obtain the distance between adjacent monitoring points, which is denoted as the point spacing. The coordinates of the first monitoring point are the sum of the coordinates of the starting point of the corresponding section and the point spacing; the coordinates of the second monitoring point are the sum of the coordinates of the first monitoring point and the point spacing, and so on, until the coordinates of all monitoring points are determined. Finally, the coordinates of each monitoring point are written into the controller.

[0042] In determining the specific number and coordinates of monitoring points in each of the aforementioned sections, the division length of each section was based on the initial calculation. To ensure spatial resolution while controlling monitoring costs, the unit length was set to 0.3 times the maximum particle drift distance calculated in the initial calculation. The coordinates and number of each monitoring point were determined once based on the initial calculation results and will not be changed during subsequent operation.

[0043] Subsequently, during the first magnetic separator discharge period after the equipment is put into operation, the controller controls all monitoring points in each section to collect the slurry level and overflow velocity at the corresponding locations. The collection cycle of each monitoring point is taken as a preset initial value. Specifically, the total number of monitoring points is counted, and the duration of a single pause period of the magnetic separator is divided by the total number of monitoring points to obtain the initial value of the collection cycle, so that each monitoring point completes at least one collection during the first pause period. The duration of a single pause period of the magnetic separator is directly read from the magnetic separator control system.

[0044] After the first magnetic separator discharge period ends, the last sampling period within that period, along with several consecutive sampling periods preceding it, are extracted as the calculation window. To mitigate instantaneous fluctuations and avoid decision delays, the specific number of sampling periods is set to four, meaning there are a total of five sampling periods within the calculation window.

[0045] For each monitoring point, the arithmetic mean of all slurry level heights within the calculation window is extracted as the baseline level height. Then, the square of the difference between each slurry level height and the baseline level height is calculated. All squared values ​​are summed and divided by the number of collection cycles within the calculation window. The square root of the result is taken as the standard deviation of the slurry level height fluctuation. Similarly, the arithmetic mean of all overflow velocities within the calculation window is extracted as the baseline velocity, and the standard deviation of the overflow velocity fluctuation is obtained in the same manner.

[0046] It should be added that before the equipment is put into operation, the overflow weir opening needs to be cleaned or inspected to ensure that there is no coal slime adhering to the weir opening. Based on this, during the first magnetic separator discharge period, no coal slime has formed at the weir opening. Therefore, the arithmetic mean of the slurry level height and the arithmetic mean of the overflow velocity within the above calculation window can reflect the slurry level height and overflow velocity at each monitoring point in the absence of accumulation, and thus can be used as the corresponding benchmark values.

[0047] Next, the standard deviation of the slurry level height fluctuation is multiplied by a preset multiple to obtain the reference fluctuation value of the slurry level height; the standard deviation of the overflow velocity fluctuation is multiplied by the same preset multiple to obtain the reference fluctuation value of the overflow velocity; according to statistical principles, the preset multiple is specifically set to 3 times.

[0048] Once the reference fluctuation values ​​for the slurry level and overflow velocity are determined during the first magnetic separator discharge period, they are written into the controller configuration parameters and directly called upon during subsequent operation. When the coal type is changed, the physical structure of the overflow weir is modified, or the viscosity and density of the feed slurry are adjusted, the reference fluctuation values ​​can be re-determined in the same manner during the new first magnetic separator discharge period.

[0049] For the magnetic separator discharge periods other than the first magnetic separator discharge period, the calculation window is determined in the aforementioned manner, and the following process is performed: For each monitoring point, the difference between the slurry level height of each collection cycle and the slurry level height of the previous collection cycle is calculated one by one within the calculation window. When the obtained difference is greater than zero, it indicates that the slurry level height of the corresponding sampling cycle has increased. Similarly, the difference between the overflow velocity of each collection cycle and the overflow velocity of the previous collection cycle is calculated one by one. When the obtained difference is less than zero, it indicates that the velocity of the corresponding sampling cycle has decreased.

[0050] If the flow rate decreases while the liquid level increases during the same sampling period, the corresponding sampling period is recorded as the accumulation period; otherwise, it is not recorded as the accumulation period.

[0051] For each monitoring point, the number of accumulation cycles within the calculation window is counted; at the same time, the slurry level height of the last collection cycle within the calculation window is subtracted from the slurry level height of the first collection cycle within the calculation window to obtain the total increase in slurry level height; similarly, the total decrease in overflow velocity is obtained.

[0052] The following conditions are used to determine whether a coal slime accumulation trend exists: 1) The number of accumulation cycles is greater than half the total number of adjacent cycle pairs within the calculation window; 2) The total rise is greater than the reference fluctuation value of the slurry level height, and the total decrease in flow velocity is greater than the reference fluctuation value of the overflow velocity. Specifically, when the calculation window consists of five acquisition cycles, the total number of adjacent cycle pairs within the calculation window is four.

[0053] When both conditions 1) and 2) are met, it is determined that there is a coal slime accumulation trend at the monitoring point; otherwise, it is determined that there is no coal slime accumulation trend, and the corresponding coal slime accumulation index is set to 0.

[0054] The coordinates of monitoring points identified as having a tendency to accumulate coal slime will be directly determined as the location of coal slime accumulation, so that targeted control can be carried out on the location of coal slime accumulation in the future.

[0055] Subsequently, for monitoring points determined to have a tendency to accumulate coal slime, the total increase was divided by the slurry level height in the first collection cycle within the calculation window to obtain the relative increase in slurry level height, and the total decrease was divided by the overflow velocity in the first collection cycle within the calculation window to obtain the relative decrease in overflow velocity.

[0056] To capture changes in coal slime accumulation more promptly by shortening the collection cycle and increasing the collection frequency when the coal slime accumulation index is higher, the larger of the relative increase and relative decrease values ​​is taken as the accumulation intensity. Next, the maximum value is extracted from all accumulation intensities in the feeding section, middle section, and discharge section. Each accumulation intensity is divided by the maximum value, and the resulting ratio is the coal slime accumulation index for the corresponding monitoring point. The maximum value of the coal slime accumulation index within each section is taken as the coal slime accumulation index for that section, thus determining the coal slime accumulation index for the feeding section, middle section, and discharge section. The coal slime accumulation index ranges from 0 to 1.

[0057] The coal slime accumulation index of each section is added to 1 to obtain the monitoring demand intensity of each section in the next magnetic separator discharge period, which is denoted as the monitoring intensity. The initial value of the collection cycle is divided by the monitoring intensity of each section to obtain the collection cycle of each section in the next magnetic separator discharge period, thus updating the collection cycle. The monitoring intensity is a dimensionless amplification factor, ranging from 1 to 2. The larger the value, the more urgent the monitoring demand, and the shorter the collection cycle should be. When the coal slime accumulation index is 0, the monitoring intensity is 1, and the collection cycle remains unchanged from the initial value.

[0058] At the start of the next magnetic separator discharge period, the controller triggers the monitoring points in the corresponding section to collect the slurry level and overflow velocity according to the updated collection cycle for each section. After each magnetic separator discharge period, the collection cycle is updated in the above manner to ensure that the collection frequency of each section dynamically matches the changes in its coal slime accumulation state.

[0059] Please see Figure 3 Step S2: Compare the slurry level height and overflow velocity at adjacent monitoring points to obtain the overflow weir outflow difference sequence along the flow path; based on the outflow difference sequence along the flow path and the real-time collected feed slurry flow rate, generate the basic control opening.

[0060] First, for the feed section, the middle section, and the discharge section, all monitoring points in each section are arranged sequentially according to the direction of slurry flow.

[0061] Next, for each acquisition cycle within the calculation window, starting from the second monitoring point in each segment, the slurry level height of each monitoring point is subtracted from the slurry level height of the previous adjacent monitoring point to obtain the slurry level height difference between adjacent monitoring points; similarly, the overflow velocity of each monitoring point is subtracted from the overflow velocity of the previous adjacent monitoring point to obtain the velocity difference between adjacent monitoring points.

[0062] For each adjacent monitoring point, the difference between the liquid level height difference in each sampling cycle and the liquid level height difference in the previous adjacent sampling cycle is calculated to obtain the change in height difference between adjacent sampling cycles. Similarly, the change in flow velocity difference between adjacent sampling cycles is obtained.

[0063] When the change in height difference is positive and the change in velocity difference is negative, it indicates that the cross-section of the flow is narrowed due to the accumulation of coal slime, the flow capacity of the weir decreases, the slurry level is forced to rise, and the overflow velocity decreases due to increased resistance. When the change in height difference is negative and the change in velocity difference is positive, it indicates that the coal slime is washed away, the flow capacity of the weir recovers, the slurry level drops, and the overflow velocity is recovering.

[0064] To filter out transient interference and ensure the reliability of the judgment, the number of adjacent acquisition cycles in which the change in height difference is positive and the change in velocity difference is negative is counted as the first quantity; the number of adjacent acquisition cycles in which the change in height difference is negative and the change in velocity difference is positive is counted as the second quantity.

[0065] To simplify the description, the next monitoring point among adjacent monitoring points is referred to as the "later monitoring point". The following judgment is performed on each adjacent monitoring point: When the first quantity is greater than half of the total number of adjacent periods within the calculation window, it indicates that the narrowing of the flow section, the decrease in the weir flow capacity, the forced rise of the slurry level, and the decrease in the overflow velocity due to increased resistance caused by coal slime accumulation are not caused by instantaneous interference. Therefore, it is determined that the coal slime accumulation at the later monitoring point is aggravated. When the second quantity is greater than half of the total number of adjacent periods within the calculation window, it indicates that the coal slime is being washed away, the weir flow capacity is recovering, the slurry level is falling, and the overflow velocity is recovering. This is not caused by instantaneous interference. Therefore, it is determined that the coal slime accumulation at the later monitoring point is weakening. Otherwise, it is determined that the coal slime accumulation at the later monitoring point remains unchanged.

[0066] Subsequently, the differences in liquid level and flow velocity within the same section were used as the corresponding outflow difference sequences for each section. The outflow difference sequences of the three sections were then summarized to obtain the outflow difference sequence of the overflow weir.

[0067] After obtaining the outflow difference sequence and coal slime accumulation location along the overflow weir, the overflow weir opening needs to be adjusted to restore the overflow weir to a uniform outflow state, ensuring the quality of magnetic heavy medium recovery. Before adjusting the overflow weir opening through the lifting actuator, the final control opening needs to be determined. The specific determination process is as follows: After excluding the first monitoring point in each section, the remaining monitoring points are numbered sequentially according to the direction of slurry flow. The sum of the numbers of the remaining monitoring points is calculated, and the number of each monitoring point is divided by the sum to obtain the weight of each monitoring point.

[0068] The numerical values ​​of the monitoring points reflect their order of distance from the starting point of the section along the direction of slurry flow. A larger number indicates a monitoring point closer to the downstream, where the slurry level and overflow velocity accumulate the influence of the upstream, better representing the outflow state of the slurry after it has fully developed. Therefore, the weight of each monitoring point is determined using this method, so that monitoring points closer to the downstream are assigned a higher weight, thus ensuring that subsequent calculations reflect the actual situation.

[0069] To ensure the timeliness of the control, within the calculation window corresponding to the discharge period of the magnetic separator, the liquid level height difference between each adjacent monitoring point corresponding to the last collection cycle is divided by the reference liquid level height of the corresponding subsequent monitoring point to obtain the relative deviation of the liquid level at each subsequent monitoring point; the flow velocity difference between each adjacent monitoring point corresponding to the last collection cycle is divided by the reference flow velocity of the corresponding subsequent monitoring point to obtain the relative deviation of the flow velocity at each subsequent monitoring point.

[0070] Next, the relative deviation of the liquid level and the relative deviation of the flow velocity are added together and multiplied by their corresponding weights to obtain the weighted deviation components of each subsequent monitoring point. All weighted deviation components are summed to obtain the friction deviation. The friction deviation reflects the overall deviation of the overflow weir's outflow state relative to the baseline state.

[0071] Then, the rated design opening is read from the equipment technical parameter table, and the feed slurry flow rate is read in real time from the electromagnetic flowmeter on the feed pipe. The feed slurry flow rate is divided by the rated flow rate to obtain the flow ratio coefficient. The flow ratio coefficient is subtracted by 1 to obtain the relative deviation ratio of the feed slurry flow rate relative to the rated flow rate. The relative deviation ratio is multiplied by the design opening to obtain the flow feedforward value. The flow feedforward value represents the feedforward adjustment caused by the deviation of the feed slurry flow rate from the rated flow rate. Through flow feedforward adjustment, the slurry level and overflow velocity are pre-adjusted before visible deviations occur due to changes in the feed slurry flow rate, shortening the lag time. The friction deviation is multiplied by the rated design opening to obtain the friction opening deviation. The friction opening deviation is superimposed on the flow feedforward value to obtain the basic control opening.

[0072] It should be noted that the flow feedforward value is calculated in real time based on the deviation between the feed flow rate and the rated flow rate, and is used to adjust in advance before the liquid level and flow velocity change; the deviation of the opening along the flow path is calculated based on the actual slurry liquid level height and overflow velocity collected at the monitoring point, thereby correcting the outflow imbalance residual that the flow feedforward value failed to eliminate, as well as the deviation along the flow path caused by non-flow factors such as coal slime accumulation.

[0073] Step S3: Summarize the coal slime accumulation locations in each section to obtain the overall coal slime accumulation distribution, and generate the opening compensation amount at the same time; superimpose the basic control opening amount and the opening compensation amount to obtain the final control opening amount.

[0074] The coal slime accumulation locations determined in step S2 are classified according to their respective feeding section, middle section, or discharge section to obtain a set of coal slime accumulation locations for each section. The coal slime accumulation location sets of the three sections are then combined to obtain the overall coal slime accumulation distribution.

[0075] The total number of coal slime accumulation locations in the entire area is counted and recorded as the total number of accumulations; the number of coal slime accumulation locations in each section is counted and the maximum value is extracted and recorded as the maximum accumulation number.

[0076] Next, the minimum execution step length is read from the technical parameter table of the lifting actuator of the overflow weir. The total accumulation is multiplied by the minimum execution step length to obtain the basic compensation amount. The maximum accumulation is divided by the sum of the total accumulation and one to obtain the concentration. The value one is used to prevent division by zero. The higher the concentration, the more concentrated the coal slime accumulation is in a certain section.

[0077] Multiply the basic compensation amount by the concentration degree, and add the resulting product to the basic compensation amount to obtain the opening compensation amount. The opening compensation amount represents the additional compensation applied to the opening of the overflow weir in response to the impact of local coal slime accumulation on the overflow weir's flow capacity.

[0078] Finally, the basic control opening degree and the opening compensation amount are superimposed to obtain the final control opening degree.

[0079] Step S4: Adjust the overflow height of the overflow weir according to the final control opening. At the same time, determine the actual flushing frequency and actual flushing pressure based on the section where the coal slime is located, so as to perform high-pressure flushing.

[0080] After obtaining the final control opening, the control action is executed. Specifically, the controller sends the final control opening obtained in step S3 as the target opening command to the lifting actuator of the overflow weir, and controls the lifting actuator to adjust the opening of the overflow weir (i.e., the overflow height of the overflow weir).

[0081] To avoid frequent adjustments, before sending the target opening command, the controller first reads the current opening (in millimeters) of the overflow weir from the position feedback sensor of the lifting actuator in real time, and calculates the difference between the final controlled opening and the current opening. When the difference is less than the minimum execution step (in millimeters), it indicates that the difference between the final controlled opening and the current opening is small and insufficient to have a substantial impact on the coal slime accumulation state. Therefore, no target opening command is sent, and the current opening remains unchanged. Conversely, when the difference is greater than or equal to the minimum execution step, it indicates that the difference between the current opening and the final controlled opening is large. Adjusting the current opening can effectively improve the coal slime accumulation state. Therefore, a target opening command is sent to adjust the lifting actuator to the final controlled opening.

[0082] Adjusting the overflow weir opening changes the overall flow cross-section of the weir, but it cannot directly strip away the hardened coal slime at the coal slime accumulation site, thus failing to fully restore the flow capacity. Therefore, high-pressure flushing of the coal slime accumulation site is necessary to prevent localized coal slime blockage.

[0083] Specifically, first read the rated flushing pressure from the nameplate of the high-pressure flushing system, and at the same time obtain the minimum operating interval of the high-pressure flushing valve from the product manual of the high-pressure flushing system. Divide the duration of a single pause of the magnetic separator by the minimum operating interval of the high-pressure flushing valve, and take the integer part of the result as the reference flushing frequency. When the result is less than 1, the reference flushing frequency is set to 1.

[0084] For sections with coal slime accumulation, the actual flushing frequency and actual flushing pressure are determined as follows: extract the coal slime accumulation index of the corresponding section, multiply the coal slime accumulation index by the benchmark flushing frequency, and add the product to the benchmark flushing frequency to obtain the actual flushing frequency of the corresponding section.

[0085] The preset proportion of the rated flushing pressure is used as the benchmark pressure; the number of coal slime accumulation locations in each section is divided by the number of monitoring points in the same section to obtain the proportion of accumulation locations; the proportion of accumulation locations is multiplied by the benchmark flushing pressure, and then the product is added to the benchmark pressure to obtain the actual flushing pressure for the corresponding section. Based on industry experience, the preset proportion is specifically set to 0.7 to ensure both a safety margin and effective flushing.

[0086] Subsequently, based on the actual flushing frequency and actual flushing pressure, the controller performs high-pressure flushing on the sections where coal slime accumulates during the magnetic separator discharge period.

[0087] Please see Figure 4 Step S5: Based on the slurry level and overflow velocity at each monitoring point, determine whether the overflow flow field is uniform; if so, lock the overflow weir height and stop high-pressure flushing.

[0088] During the next magnetic separator discharge period after the control action and high-pressure rinsing in step S4, the calculation window is extracted. For each acquisition cycle within the calculation window, the liquid level difference and flow velocity difference at each monitoring point in the same section are recalculated according to the calculation method defined in step S2.

[0089] When, within all acquisition cycles within the calculation window, the difference in slurry level height between all adjacent monitoring points is less than or equal to the reference fluctuation value of the slurry level height, and the difference in flow velocity between all adjacent monitoring points is less than or equal to the reference fluctuation value of the overflow velocity, it indicates that the differences in slurry level height and overflow velocity between adjacent monitoring points have returned to the disturbance range under conditions without coal slime accumulation. There is no backwatering or local slurry level rise caused by coal slime accumulation, nor is there a sudden drop or rise in overflow velocity caused by local narrowing of the flow cross section. Therefore, it is determined that the overflow flow field has been restored to uniformity. Otherwise, it is determined that the overflow flow field has not been restored to uniformity.

[0090] When it is determined that the overflow flow field has returned to uniformity, the controller stops sending new target opening commands to the overflow weir lifting actuator, maintaining the current opening unchanged, thereby locking the overflow weir flow height. At the same time, the controller closes all high-pressure flushing valves, stopping high-pressure flushing.

[0091] If it is determined that the overflow flow field has not returned to uniformity, the outflow difference sequence and coal slime accumulation position along the flow path are obtained again. Then, steps S3 and S4 are executed sequentially to generate a new final control opening and continue to perform control actions and high-pressure flushing. This cycle is repeated until it is determined that the overflow flow field has returned to uniformity.

[0092] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0093] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0094] In addition, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0095] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0096] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the magnetic separation of magnetic heavy media recovery in coal mining, characterized in that, Includes the following steps: The overflow weir was divided into a feeding section, a middle section, and a discharge section along the slurry flow path. Monitoring points were set up in each section to collect the slurry level and overflow velocity during the discharge interval of the magnetic separator, and to determine the location of coal slime accumulation. By comparing the slurry level and overflow velocity at adjacent monitoring points in each section, a flow difference sequence along the flow path is obtained; based on the flow difference sequence along the flow path and the real-time collected feed slurry flow rate, a basic control opening is generated. By summarizing the coal slime accumulation locations in each section, the overall coal slime accumulation distribution is obtained, and the opening compensation amount is generated simultaneously. The final control opening is obtained by superimposing the basic control opening and the opening compensation amount. The overflow height of the overflow weir is adjusted according to the final control opening, and the actual flushing frequency and actual flushing pressure are determined based on the section where the coal slime is located, so as to carry out high-pressure flushing. Based on the slurry level and overflow velocity at each monitoring point, determine whether the overflow flow field has returned to uniformity; if so, lock the overflow weir height and stop high-pressure flushing.

2. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 1, characterized in that, The process of dividing the material into the feeding section, the middle section, and the discharge section includes: Obtain the feed slurry flow rate and the cross-sectional dimensions of the feed pipe. Based on the cross-sectional dimensions, calculate the cross-sectional area of ​​the feed pipe. Divide the feed slurry flow rate by the cross-sectional area of ​​the feed pipe to obtain the impact velocity of the feed slurry. Obtain the density and viscosity of the slurry, as well as the particle size and density of the largest particles in the coal slime, and calculate the settling velocity of the largest particles. Divide the impact velocity by the settling velocity and multiply by the vertical height of the overflow weir to obtain the maximum particle drift distance; determine the division length of the feeding section based on the maximum particle drift distance; Obtain the design overflow velocity and weir width, and calculate the flow Reynolds number. When the flow Reynolds number is less than 1000, take the first multiple of the weir width as the division length of the discharge section. When the flow Reynolds number is greater than or equal to 1000, take the second multiple of the weir width as the division length of the discharge section. Subtract the division lengths of the feeding section and the discharge section from the total length of the overflow weir body to obtain the division length of the middle section; Based on the division length, the overflow weir body is divided into the feeding section, the middle section and the discharge section along the direction of slurry flow.

3. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 1, characterized in that, The process of setting up monitoring points includes: At least three monitoring points are set up along the length of the overflow weir in each section; during the discharge period of the magnetic separator, the slurry liquid level height and overflow velocity are collected at each monitoring point. After the magnetic separator discharge period ends, the last acquisition cycle within the magnetic separator discharge period and several consecutive acquisition cycles adjacent to the last acquisition cycle are extracted as the calculation window. The collection period in which the slurry level in the calculation window is greater than the slurry level in the previous collection period and the overflow velocity is less than the overflow velocity in the previous collection period is recorded as the accumulation period. Subtract the slurry level of the first collection cycle from the slurry level of the last collection cycle within the calculation window to obtain the total increase in slurry level; similarly, obtain the total decrease in overflow velocity. Based on the total rise and fall, and combined with the slurry level height and overflow velocity of each monitoring point in the first collection cycle within the calculation window, the coal slime accumulation index of each section is determined; and the coal slime accumulation location is determined by combining the number of accumulation cycles of each monitoring point within the calculation window. Add the coal slime accumulation index to one to obtain the monitoring intensity of each section; divide the initial value of the collection cycle by the monitoring intensity to obtain the collection cycle of each section in the next magnetic separator discharge period.

4. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 3, characterized in that, The process of obtaining the flow difference sequence along the overflow weir is as follows: The monitoring points in each section are arranged in the order of the slurry flow. Within the same collection period, starting from the second monitoring point in each section, the slurry level height of each monitoring point is subtracted from the slurry level height of the previous adjacent monitoring point to obtain the slurry level height difference between adjacent monitoring points. Similarly, based on the overflow velocity of each monitoring point, the velocity difference between adjacent monitoring points is obtained. For each adjacent monitoring point, the difference between the liquid level height difference in each sampling cycle and the liquid level height difference in the previous adjacent sampling cycle is calculated one by one to obtain the change in height difference between each adjacent sampling cycle. Similarly, the change in flow velocity difference between each adjacent sampling cycle is obtained. By summing up the differences in liquid level and flow velocity, a sequence of outflow differences along the overflow weir is obtained.

5. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 4, characterized in that, After obtaining the flow difference sequence along the overflow weir: The next monitoring point among all adjacent monitoring points is recorded as the next monitoring point; For each adjacent monitoring point, within the calculation window, if the number of adjacent acquisition cycles with positive height difference change and negative velocity difference change is greater than half of the total number of adjacent cycles within the calculation window, then it is determined that the coal slime accumulation at the subsequent monitoring point is aggravated. If the number of adjacent acquisition cycles with negative height difference changes and positive velocity difference changes is greater than half the total number of adjacent cycles within the calculation window, then it is determined that the coal slime accumulation at the monitoring point is weakening.

6. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 5, characterized in that, The process of generating the basic control opening is as follows: After excluding the first monitoring point in each section, the remaining monitoring points are numbered sequentially according to the direction of slurry flow; the sum of the numbers of the remaining monitoring points is calculated, and the number of each monitoring point is divided by the sum to obtain the weight of each monitoring point; Divide the liquid level difference by the reference liquid level height of the monitoring point to obtain the relative deviation of the liquid level at the monitoring point; divide the velocity difference by the reference velocity at the monitoring point to obtain the relative velocity deviation at the monitoring point; add the relative deviation of the liquid level and the relative velocity deviation and multiply by the weight of the corresponding monitoring point to obtain the weighted deviation component; sum all the weighted deviation components to obtain the friction loss. Divide the feed slurry flow rate by the rated design flow rate of the overflow weir to obtain the flow rate ratio coefficient; subtract one from the flow rate ratio coefficient and multiply it by the rated design opening to obtain the flow rate feedforward value. Multiply the friction deviation by the rated design opening to obtain the friction opening deviation; add the friction opening deviation to the flow feedforward value to obtain the basic control opening.

7. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 1, characterized in that, The process of generating the opening compensation amount is as follows: The locations of each coal slime accumulation are classified according to their respective sections to obtain the set of coal slime accumulation locations for each section; the sets of coal slime accumulation locations for each section are then summarized to obtain the overall coal slime accumulation distribution. The total number of coal slime accumulation locations in the overall coal slime accumulation distribution is recorded as the total accumulation count; the number of coal slime accumulation locations in the coal slime accumulation location set of each section is recorded, and the maximum value is extracted and recorded as the maximum accumulation count. Obtain the minimum execution step length of the lifting actuator, multiply the total number of stacked units by the minimum executable step length to obtain the basic compensation amount; Divide the maximum number of stacks by the sum of the total number of stacks and one to obtain the concentration; multiply the basic compensation by the concentration, and then add the resulting product to the basic compensation to obtain the opening compensation.

8. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 1, characterized in that, The process of determining the actual flushing frequency and actual flushing pressure is as follows: Obtain the baseline flushing frequency and rated flushing pressure, and use a preset proportion of the rated flushing pressure as the baseline pressure; For sections where coal slime accumulates, extract the coal slime accumulation index, count the number of coal slime accumulation locations, and then count the number of monitoring points in the corresponding section. Multiply the coal slime accumulation index by the baseline flushing frequency, and add the product to the baseline flushing frequency to obtain the actual flushing frequency for the corresponding section. Divide the number of coal slime accumulation locations by the number of monitoring points to obtain the percentage of accumulation locations. Multiply the percentage of the accumulation location by the reference pressure, and add the product to the reference pressure to obtain the actual flushing pressure of the corresponding section.

9. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 4, characterized in that, The process of determining whether the overflow flow field is uniform is as follows: For each monitoring point, the reference fluctuation values ​​of slurry level height and overflow velocity are determined based on the arithmetic mean of the slurry level height and overflow velocity within the calculation window corresponding to the first magnetic separator discharge period. During the next magnetic separator discharge period after adjusting the overflow weir height and performing high-pressure flushing, the calculation window is extracted; for each acquisition cycle within the calculation window, the liquid level difference and flow velocity difference between adjacent monitoring points in the same section are recalculated. Based on the number of monitoring points with a liquid level difference less than or equal to the reference fluctuation value of the slurry liquid level height in all collection cycles within the calculation window, and the number of monitoring points with a flow velocity difference less than or equal to the reference fluctuation value of the overflow flow velocity, it is determined whether the overflow flow field has returned to uniformity.

10. The magnetic separation control method for recovering magnetic heavy media in coal mining as described in claim 1, characterized in that, The process of locking the overflow height of the overflow weir and stopping high-pressure flushing is as follows: When it is determined that the overflow flow field has returned to uniformity, the current opening of the overflow weir is kept unchanged, thereby locking the overflow height of the overflow weir; at the same time, all high-pressure flushing valves are closed and high-pressure flushing is stopped. When it is determined that the overflow flow field has not returned to uniformity, a new final control opening is generated, the overflow weir height is adjusted and high-pressure flushing is performed.

Images