Coal density distribution and particle size distribution measuring system and method

Abstract

The invention discloses a coal density distribution and particle size distribution measuring system and method, and relates to the field of coal washing, and the system comprises a computer, an X-ray source, a detector, a rack, a rotating platform, a guide rail, a sample barrel and a coal sample screening device; a coal sample is contained in the sample barrel; the coal sample screening device is used for screening coal samples into large-particle coal samples and small-particle coal samples; the guide rail drives the rotating platform to move in the horizontal direction, the rotating platform drives the sample barrel to rotate, an X-ray beam emitted by the X-ray source irradiates in the horizontal direction, penetrates through the cross section of the sample barrel and reaches the detector, the detector sends collected coal sample X-rays and position information of the rotating platform to the computer for image reconstruction, and a coal sample CT image is obtained; and the computer is also used for calculating density distribution and particle size distribution of the coal sample according to the coal sample CT image. According to the invention, the accuracy and speed of density distribution and particle size distribution measurement can be improved.

Description

Technical Field

[0001] This application relates to the field of coal washing and beneficiation, and in particular to a coal density distribution and particle size distribution measurement system and method. Background Technology

[0002] Coal mined from coal mines, after undergoing simple processes such as crushing and screening, is called "raw coal." This raw coal is then fed into washing and beneficiation equipment for the separation of coal and gangue. During this process, it is necessary to understand the density and particle size distribution of the ore in the raw coal. Based on these two distributions, the parameters of the washing and beneficiation equipment are determined, and it is determined whether the washing and beneficiation yield has reached its optimal level. Therefore, measuring the density distribution (the percentage of ore of various densities by mass in the total) and particle size distribution (the percentage of ore of various particle sizes by mass in the total) of the raw coal is crucial for the washing and beneficiation process.

[0003] The traditional method for measuring density distribution is called the "buoyancy test." The coal buoyancy test is a core experimental method for evaluating coal washability, determining separation density, and optimizing washing processes. Its principle is based on the differences in buoyancy behavior of coal particles of different densities in heavy liquids. By placing coal samples in heavy liquids of different densities (such as zinc chloride solutions) to separate them into layers, products of different density grades are separated, thereby analyzing the density composition of the coal.

[0004] The process of coal float-sink test is very complex, including: 1) coal sample preparation, including sieving and weighing; 2) equipment and reagent preparation, preparation of heavy liquids of different densities and preparation of tools; (3) coal sample pretreatment: including washing coal slime and coal slime recovery; 4) stratification and sorting, including immersion buffer, time control and removal of floating objects; 5) layer-by-layer sorting, transferring the sediment to the next density level heavy liquid and then stratifying and sorting again; 6) coal sample cleaning, drying and weighing; 7) calculation and verification of data validity. The whole process usually takes 40 minutes to 2.5 hours.

[0005] Traditional coal float-and-sink tests are labor-intensive, time-consuming, and unable to quickly guide coal washing and processing. To address this, some companies have developed automated float-and-sink test devices. The basic idea is to replace the manual aspects of traditional tests with electronically controlled automation, thus saving labor costs. However, these devices still require the operation of each step of the traditional test, and the time lag is not significantly reduced. Furthermore, these automated systems have complex mechanical actuators and numerous control components, making them prone to malfunctions.

[0006] Coal particles can cover a wide range of sizes. When measuring these particles simultaneously, not only can small particles not be distinguished, but clustered small coal particles can also cause interference in the image, affecting the identification of large coal particles. Summary of the Invention

[0007] The purpose of this application is to provide a coal density distribution and particle size distribution measurement system and method, which can improve the accuracy and speed of density distribution and particle size distribution measurement.

[0008] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a coal density distribution and particle size distribution measurement system, including: a computer, an X-ray source, a detector, a frame, a rotating platform, a guide rail, and a sample container; The frame is mounted at both ends of the guide rail and is used to fix the X-ray source and the detector; the rotating platform is movably mounted on the guide rail and the sample container is placed on the rotating platform; the sample container contains a coal sample. The guide rail drives the rotating platform to move horizontally, the rotating platform drives the sample barrel to rotate, the X-ray beam emitted by the X-ray source irradiates horizontally and passes through the cross-section of the sample barrel, and reaches the detector. The detector sends the collected coal sample X-ray and the position information of the rotating platform to the computer for image reconstruction to obtain a coal sample CT image. The computer is also used to calculate the density distribution and particle size distribution of the coal sample based on the CT image of the coal sample.

[0009] Secondly, this application provides a method for measuring the density distribution and particle size distribution of coal, the method being applied to the aforementioned coal density distribution and particle size distribution measurement system, the method comprising: Acquire CT images of coal samples; The density map is obtained by calculating the density of each pixel in the coal sample based on the gray value of each pixel in the CT image of the coal sample. Identify the particles in the density map and calculate the average density and particle size of each particle; The density and particle size distribution of the coal sample are determined based on the average density and particle size of each particle.

[0010] Thirdly, this application provides a method for measuring the density distribution and particle size distribution of coal, the method being applied to the aforementioned coal density distribution and particle size distribution measurement system, the method comprising: Acquire CT images of coal samples; Calculate the density of each pixel in the coal sample based on the gray value of each pixel in the CT image of the coal sample; Pixels with a density less than the density threshold are identified as gaps or dust, and pixels with a density greater than the density threshold are discarded. The density scale of the coal sample is determined based on the density of the retained pixels, and a density map is obtained. The particles in the density map are identified, and the particle size of each particle is calculated to obtain the particle size distribution of the coal sample.

[0011] According to the specific embodiments provided in this application, this application has the following technical effects: 1. This application utilizes X-ray CT imaging technology to scan and measure collected coal samples (i.e., coal specimens) to obtain CT images of the coal samples. The grayscale values ​​of these CT images are correlated with the density at corresponding points; that is, the density distribution and particle size distribution of the coal sample can be determined based on the grayscale values ​​of the CT images. The above process is simple and easy to operate, and can improve the accuracy and speed of density and particle size distribution measurements.

[0012] 2. A coal sample screening device is used to distinguish between large and small particles in the coal sample, enabling the measurement of coal samples with two different particle sizes and achieving full particle size coverage measurement of the coal sample. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic front view of a coal density distribution and particle size distribution measurement system provided in an embodiment of this application; Figure 2 A schematic flowchart illustrating a method for measuring coal density distribution and particle size distribution according to an embodiment of this application; Figure 3 This is a flowchart illustrating a method for measuring coal density distribution and particle size distribution, provided in another embodiment of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Example 1 like Figure 1As shown in the figure, this embodiment provides a coal density distribution and particle size distribution measurement system, including: a computer (not shown in the figure), an X-ray source 1, a detector 2, a frame 3, a rotating platform 4, a guide rail 5, and a sample container 6.

[0018] The frame 3 is disposed at both ends of the guide rail 5, and the frame 3 is used to fix the X-ray source 1 and the detector 2; the rotating platform 4 is movably disposed on the guide rail 5, and the sample bucket 6 is placed on the rotating platform 4; the sample bucket 6 contains a coal sample.

[0019] The guide rail 5 drives the rotating platform 4 to move horizontally, and the rotating platform 4 drives the sample barrel 6 to rotate. The X-ray beam emitted by the X-ray source 1 irradiates the sample barrel 6 horizontally and passes through the cross-section of the sample barrel 6, reaching the detector 2. The detector 2 sends the collected coal sample X-ray and the position information of the rotating platform 4 to the computer for image reconstruction to obtain a coal sample CT image.

[0020] The computer is also used to calculate the density distribution and particle size distribution of the coal sample based on the CT image of the coal sample.

[0021] In this embodiment, the X-ray source, detector, frame, rotating platform, guide rail, and sample container are all housed within an X-ray shielding housing 7. An automatically opening and closing sample inlet door (not shown in the figure) is installed on the housing 7. The sample inlet door opens when the sample container 6 is inserted or removed, and closes when the coal sample is being measured.

[0022] In this embodiment, the system further includes a coal sample screening device.

[0023] The coal sample screening device is used to screen coal samples into large-particle coal samples and small-particle coal samples; the large-particle coal samples are those with particles larger than a preset particle size value, and the small-particle coal samples are those with particles smaller than the preset particle size value. The sample container 6 includes a large sample container and a small sample container; the large sample container is used to hold the large-particle coal samples, and the small sample container is used to hold the small-particle coal samples.

[0024] Due to the spatial resolution limitations of CT measurements, it is impossible to achieve full coverage identification of particles in a coal sample from largest to smallest in a single measurement. Therefore, this embodiment involves two measurements, with different placement of the sample containers of different sizes in the two measurements, resulting in different spatial resolutions of the images. This allows for the measurement of materials with a wider particle size distribution.

[0025] The coal sample screening device must ensure that the lower limit of the size of large coal particles is greater than or equal to the spatial distribution rate when measuring large sample bins using CT images.

[0026] In this embodiment, the system further includes a coal sample collection device and a coal sample delivery device.

[0027] The coal sampling device is used to obtain coal samples. Specifically, the coal sampling device collects a representative coal sample from the main conveyor belt or other locations, processes the coal sample, and places it into sample container 6.

[0028] The coal sample taking and delivering device may be, but is not limited to, a mechanical gripper, used to deliver the sample bucket 6 containing the sample to the rotating platform 4. After the measurement is completed, the sample bucket 6 is taken out, the coal sample in the sample bucket 6 is poured out, and the sample bucket 6 is put back into the coal sample receiving position.

[0029] In this embodiment, the computer is also used to control the coal sample collection device, the coal sample delivery device, and the X-ray source 1 to turn on or off.

[0030] The working process of the system provided in this embodiment is as follows: The coal sampling device collects a representative coal sample from the main conveyor belt or other locations. The collected coal sample is then sieved into large and small particles by a coal sample screening device and placed into sample containers 6. The coal sample delivery device sends the sample containers 6 onto the rotating platform 4 of the measurement system. The rotating platform 4 holds the sample containers 6 in place. The guide rail 5 moves the rotating platform 4 to a suitable position, ensuring that the X-ray beam emitted by the X-ray source can completely cover the cross-section of the sample container, at which point the measurement can begin.

[0031] When measuring small coal particles in a small sample container, the guide rail 5 drives the rotating platform 4 to move the sample container 6 closer to the X-ray source 1. This allows for a higher magnification CT image, enabling the resolution of even smaller particles. When measuring large coal particles in a large sample container, the guide rail 5 drives the rotating platform 4 to move the sample container 6 further away from the X-ray source 1. Although the image magnification is lower, this ensures that the fan-shaped X-ray beam covers the cross-section of the sample container 6, meeting the measurement requirements even with larger coal particle sizes. Through the coordinated operation of the guide rail 5, rotating platform 4, and sample container 6, the position of the sample container 6 can be flexibly and stably adjusted, optimizing the imaging effect and ensuring appropriate measurement results for both small and large coal particles.

[0032] During the measurement, the sample container 6 is vertically fixed on the rotating platform 4. The fan-shaped X-ray beam emitted by the X-ray source 1 irradiates the sample container horizontally and passes through the cross-section of the sample container, reaching the detector 2. The sample container 6 rotates with the rotating platform 4. The data collected by the detector 2 and the position information of the rotating platform 4 are sent to the computer in real time. The computer analyzes the cross-sectional CT image of the coal sample in the sample container 6.

[0033] In an optional embodiment, the system further includes a lifting device. The lifting device is mounted on the rotating platform 4, and the sample container 6 is placed on the lifting device. The lifting device allows the sample container 6 to be positioned at different heights, enabling the generation of CT images of cross-sections at different heights of the sample container 6. Based on these 2D images, 3D images are generated, and then particle size is identified, which can improve the accuracy of density distribution calculation.

[0034] In an alternative embodiment, the X-ray source 1 emits a cone beam, and the detector 2 is a 2D flat panel detector, so that the rotating platform 4 is at the same height, and can simultaneously scan CT images of the cross-section of multiple sample barrels, thereby improving the measurement speed.

[0035] Example 2 like Figure 2 As shown, the coal density distribution and particle size distribution measurement method provided in this embodiment includes the following steps: S201: Acquire CT images of coal samples.

[0036] S202: Calculate the density of each pixel in the coal sample based on the gray value of each pixel in the CT image of the coal sample to obtain a density map.

[0037] S203: Identify the particles in the density map and calculate the average density and particle size of each particle.

[0038] S204: Determine the density and particle size distribution of the coal sample based on the average density and particle size of each particle.

[0039] In this embodiment, X-ray CT imaging technology is used to scan and measure the collected coal sample, obtaining CT images of multiple cross-sections of the coal. The gray values ​​of the CT images are correlated with the density at corresponding points; that is, the density can be calculated based on the gray values ​​of the CT images, thus obtaining a density map. Then, traditional image pattern recognition algorithms (such as Canny edge detection) or AI image recognition methods (such as U-Net and watershed algorithms) are used to identify blocks in each density map, segmenting each particle of different sizes. The average density and particle size of each particle are then calculated, and statistical analysis yields the density distribution and particle size distribution of the coal sample.

[0040] Because each particle exists as a whole during the sorting process, its overall density determines its washing characteristics. Therefore, it is necessary to calculate its overall density, rather than the density of each individual particle, thus requiring particle identification.

[0041] Example 3 like Figure 3 As shown, the coal density distribution and particle size distribution measurement method provided in this embodiment includes the following steps: S301: Acquire CT images of coal samples.

[0042] S302: Calculate the density of each pixel in the coal sample based on the gray value of each pixel in the CT image of the coal sample.

[0043] S303: Pixels with a density less than the density threshold are identified as voids or dust and discarded, while pixels with a density greater than the density threshold are retained.

[0044] S304: Determine the density scale of the coal sample based on the density of the retained pixels to obtain a density map.

[0045] S305: Identify the particles in the density map and calculate the particle size of each particle to obtain the particle size distribution of the coal sample.

[0046] In this embodiment, based on the numerical value of each point in the CT image, the density corresponding to that point in the coal sample is determined. According to a pre-set density threshold, data below the threshold are identified as voids or dust particles smaller than the detection spatial resolution, and these are left unprocessed. Points above the threshold are retained and used to reconstruct the density map, obtaining the density distribution. Image analysis is performed on the density map to identify individual particles, and the particle size of each particle is calculated to obtain the particle size distribution.

[0047] Example 2 involves first identifying particles, analyzing their density, and then statistically analyzing their density distribution. Example 3 directly performs density distribution statistics. The data provided in Example 2 offers more accurate guidance for adjusting the coal washing process, while Example 3 is simpler to implement.

[0048] In Examples 2 and 3 above, the weight ratio of the two different large-particle coal samples and the small-particle coal samples is measured to determine the particle size and density distribution of the coal samples in the large and small sample containers. Then, based on the weight ratio of the two different particle sizes, the particle size distribution and density distribution of the coal samples before sieving are calculated.

[0049] The methods provided in Embodiments 2 and 3 above further include: calibrating the CT image of the coal sample.

[0050] The sample container holding the coal sample has its wall material as either a single-density material or two different-density materials. When the sample container's wall material is a single-density material, the CT image of the coal sample is corrected using a single-point correction method based on the CT value at the container wall location and the density of the container wall. When the sample container's wall material is two different-density materials, the CT image of the coal sample is corrected using a two-point linear correction method based on the CT value at the container wall location and the density of the container wall.

[0051] In another embodiment, to further improve the accuracy of particle size classification, multi-energy X-ray imaging technology can be used to calculate the ash content scan image based on the scanning images of high and low energy X-rays. Combining the density and ash content scan images can improve the accuracy of particle identification, thereby improving the measurement accuracy of density distribution and particle size distribution.

[0052] By employing multi-energy detectors or using two or more X-ray source tube voltages to scan the sample multiple times, scanning images under different energy X-rays can be obtained. Using multiple images from the same plane, the ash distribution of the coal sample can be calculated. This allows us to obtain the coal sample's density, particle size, and ash distribution. This data can be used for heavy media coal washing. Given the density of the heavy media, the washing effect can be calculated based on the coal sample's density, particle size, and ash distribution, i.e., the yield of clean coal and its ash content can be predicted. This solves the long-standing pain point of closed-loop control in automated coal washing.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A coal density distribution and particle size distribution measurement system, characterized in that, include: Computer, X-ray source, detector, gantry, rotating platform, guide rails, and sample container; The frame is mounted at both ends of the guide rail and is used to fix the X-ray source and the detector; the rotating platform is movably mounted on the guide rail and the sample container is placed on the rotating platform; the sample container contains a coal sample. The guide rail drives the rotating platform to move horizontally, the rotating platform drives the sample barrel to rotate, the X-ray beam emitted by the X-ray source irradiates horizontally and passes through the cross-section of the sample barrel, and reaches the detector. The detector sends the collected coal sample X-ray and the position information of the rotating platform to the computer for image reconstruction to obtain a coal sample CT image. The computer is also used to calculate the density distribution and particle size distribution of the coal sample based on the CT image of the coal sample.

2. The coal density distribution and particle size distribution measurement system according to claim 1, characterized in that, The system also includes an X-ray shielding housing, in which the X-ray source, detector, frame, rotating platform, guide rail, and sample container are all housed.

3. The coal density distribution and particle size distribution measurement system according to claim 1, characterized in that, The system also includes a coal sample screening device, which is used to screen the coal sample into large-particle coal samples and small-particle coal samples; the large-particle coal samples are coal samples with particles larger than a preset particle size value, and the small-particle coal samples are coal samples with particles smaller than the preset particle size value. The sample container includes a large sample container and a small sample container. The large sample container is used to hold large-particle coal samples, and the small sample container is used to hold small-particle coal samples.

4. The coal density distribution and particle size distribution measurement system according to claim 1, characterized in that, The system also includes: A coal sampling device used to obtain coal samples.

5. The coal density distribution and particle size distribution measurement system according to claim 1, characterized in that, The system also includes: A coal sample delivery device is used to deliver a sample bucket containing a coal sample to the rotating platform and to remove the sample bucket from the rotating platform.

6. The coal density distribution and particle size distribution measurement system according to claim 1, characterized in that, The system also includes a lifting device, which is mounted on the rotating platform, and the sample container is placed on the lifting device.

7. A method for measuring the density distribution and particle size distribution of coal, characterized in that, The method is applied to the coal density distribution and particle size distribution measurement system according to any one of claims 1-6, and the method includes: Acquire CT images of coal samples; The density map is obtained by calculating the density of each pixel in the coal sample based on the gray value of each pixel in the CT image of the coal sample. Identify the particles in the density map and calculate the average density and particle size of each particle; The density and particle size distribution of the coal sample are determined based on the average density and particle size of each particle.

8. The method for measuring coal density distribution and particle size distribution according to claim 7, characterized in that, The particles in the density map are identified using image pattern recognition algorithms or AI image recognition methods.

9. The method for measuring coal density distribution and particle size distribution according to claim 7, characterized in that, The method further includes: correcting the CT image of the coal sample; When the sample container containing the coal sample has a single-density wall material, the CT image of the coal sample is corrected using a single-point correction method based on the CT value at the location of the container wall and the density of the container wall. When the sample container containing the coal sample has two different densities in its wall material, the CT image of the coal sample is corrected using a two-point linear correction method based on the CT value at the location of the container wall and the density of the container wall.

10. A method for measuring the density distribution and particle size distribution of coal, characterized in that, The method is applied to the coal density distribution and particle size distribution measurement system according to any one of claims 1-6, and the method includes: Acquire CT images of coal samples; Calculate the density of each pixel in the coal sample based on the gray value of each pixel in the CT image of the coal sample; Pixels with a density less than the density threshold are identified as gaps or dust and are removed, while pixels with a density greater than the density threshold are retained. The density scale of the coal sample is determined based on the density of the retained pixels, and a density map is obtained. The particles in the density map are identified, and the particle size of each particle is calculated to obtain the particle size distribution of the coal sample.

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