Particle size distribution measurement method

Abstract

To provide a method capable of accurately calculating the whole mass distribution of a mixed grain size deposited body conveyed in a deposited state on a belt conveyor.SOLUTION: The present invention comprises: steps ST11-ST13 of measuring a total mass distribution of a reference mixed particle size deposit using a sieve, calculating a total number distribution, and calculating a surface number distribution; a step ST14 of assuming a first particle size distribution of a single particle size sample using an unknown constant; a step ST15 of calculating a second particle size distribution of the reference mixed particle size deposit based on a range image of the reference mixed particle size deposit conveyed in a state of being deposited on a belt conveyor BC; a step ST16 of calculating the first particle size distribution by determining the unknown constant such that the second particle size distribution is approximated by a linear sum of the first particle size distribution with a surface-number ratio of the surface-number distribution as a coefficient; and steps ST21-ST24 of calculating a total mass distribution of a target mixed particle size deposit conveyed in a state of being deposited on the belt conveyor BC using the calculated first particle size distribution.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for measuring the particle size distribution of particles such as coke, sintered ore, etc. In particular, the present invention relates to a particle size distribution measuring method capable of accurately calculating the particle size distribution of a mixed particle size deposit (deposited particle group) containing particles belonging to a plurality of particle size classes (classifications determined by particle size, which is an index of particle size) that are piled up and transported on a belt conveyor, i.e., the overall mass distribution, which is the relationship between the particle size classes and the mass ratio of the whole particles in each particle size class of the mixed particle size deposit. [Background technology]

[0002] Blast furnace raw materials such as coke and sintered ore are transported in a piled state on a belt conveyor and charged into a blast furnace. It is known that the particle size (an index showing the degree of particle size) of the particles that make up the raw materials affects the productivity of blast furnace operation. For this reason, it is desirable to continuously measure the particle size distribution of the raw materials during the raw material transportation process to maintain quality.

[0003] The particle size of blast furnace raw materials is generally measured by taking samples (sampling) from a belt conveyor at regular intervals, dividing the samples every 4 or 8 hours, and then sieving them. Therefore, even if the particle size distribution of the raw materials changes in a short period of time due to variations in the quality of the raw materials or malfunctions of the production equipment, the time intervals are too long when measuring intermittently using a sieve after sampling, so the temporal fluctuations in the particle size distribution cannot be accurately captured.

[0004] As a method capable of continuously measuring particle diameters in a non-contact manner, for example, a method described in Non-Patent Document 1 has been proposed. The method described in Non-Patent Document 1 is a measurement method using a light-section type 3D camera in which a laser light source that emits linear laser light is integrated with an area scan camera. In the method described in Non-Patent Document 1, by using a moving distance detection means such as a rotary encoder in contact with a belt conveyor, every time the belt conveyor advances a certain distance, the position of the upper edge of the cross-section of the particles deposited on the belt conveyor is measured by a 3D camera, thereby generating a distance image (sometimes referred to as a 3D image or depth image) in which the pixel value of each pixel indicates the distance from the reference position (for example, the distance from the 3D camera). In the vicinity of the boundary of the stacked particles, since the irradiated laser light is interrupted and becomes dark, and the step of the unevenness of the particles becomes large, in the distance image, the pixel value of the pixel region corresponding to the vicinity of the boundary of the particles is likely to be a value different from the pixel values of other pixel regions. In the method described in Non-Patent Document 1, this characteristic is utilized to determine the boundary of the particles and identify each particle, and calculate the particle size of each particle. Among the stacked particles, the size of the particles having a portion hidden by other particles is smaller than the actual size. For this reason, in the method described in Non-Patent Document 1, using the height information (height from the bottom of the belt conveyor) of each particle that can be calculated by the 3D camera, the surface layer particles (hereinafter, appropriately referred to as "surface layer particles") are preferentially extracted, and the minor axis diameter when each surface layer particle in the distance image is regarded as an ellipse is used as the particle size.

[0005] As a method capable of continuously and non-contact measuring the particle size, methods described in Non-Patent Document 2 and Patent Document 1 using a 3D camera, similar to the method described in Non-Patent Document 1, have also been proposed. Non-Patent Document 2 and Patent Document 1 describe in detail an edge detection method for identifying each particle and an image processing method for recognizing surface layer particles. In particular, Patent Document 1 also describes a method for making the measurement faster.

[0006] In the method described in Non-Patent Document 2, image processing is performed on the distance image acquired for the deposited particles, surface particles in the surface layer with little overlap are extracted, the particle size of each surface particle is sorted into particle size categories determined by the mesh size of the sieve, and the number distribution of surface particles (surface number distribution) which is the relationship between the particle size category and the number of surface particles for each particle size category is calculated. In addition, in the method described in Non-Patent Document 2, the number distribution of the entire deposited particles, including not only surface particles but also hidden particles, is estimated using a surface probability model which is a model that represents the degree of appearance and visibility in the surface layer according to the particle size, that is, a model that estimates the number distribution of the entire deposited particles (total number distribution) from the number distribution of surface particles. Furthermore, in the method described in Non-Patent Document 2, the volume ratio (or mass ratio) for each particle size category is used to estimate the distribution of the mass ratio of the entire deposited particles (total mass distribution).

[0007] The inventors applied the method described in Non-Patent Document 2 to a mixed-grain deposit in which particles (coke particles) belonging to multiple grain size classes are mixed in a predetermined mass ratio and deposited, and conducted a confirmation test to determine whether the overall mass distribution can be accurately estimated. As a result of this confirmation test, it was found that even if the sample was a single-grained sample consisting of only particles with the same grain size, in the case of amorphous particles such as coke and sintered ore, the grain size distribution of the single-grained sample would be wider than the grain size distribution because the grain size of the surface layer particles varies depending on the particle's posture. Therefore, it was found that simply dividing the grain sizes of the surface layer particles measured with a 3D camera into grain size distributions determined by a sieve, counting the number of surface layer particles for each grain size distribution, and applying the method described in Non-Patent Document 2 would result in a blurred grain size distribution (total mass distribution) that would not accurately match the results measured using a sieve.

[0008] Therefore, the present inventors have proposed a method described in Patent Document 2, which is capable of calculating the grain size distribution of a mixed grain size deposit with high accuracy. In the method described in Patent Document 2, for a plurality of particle size categories to which the particles constituting the mixed particle size deposit belong, single particle size samples (samples consisting only of particles having the same particle size within a particle size category) are prepared respectively, and for each single particle size sample, the particle size of the surface layer particles is measured, thereby calculating a first particle size distribution showing the relationship between the particle size and the number (or area or volume) of the surface layer particles of the single particle size sample. Further, for the mixed particle size deposit in which the particles belonging to the plurality of particle size categories are blended, the particle size of the surface layer particles is measured, thereby calculating a second particle size distribution showing the relationship between the particle size and the number (or area or volume) of the surface layer particles of the mixed particle size deposit. Furthermore, the calculated second particle size distribution is approximated by the linear sum of the calculated first particle size distributions, and each coefficient of this linear sum is regarded as the number ratio of different particle size categories of the surface layer particles of the mixed particle size deposit when the mixed particle size deposit is considered to be composed of a combination of single particle size samples of a plurality of particle size categories. And thereafter, by calculating the overall mass distribution in the same procedure as the method described in Non-Patent Document 2 using the coefficient, it is possible to perform a highly accurate calculation that well matches the result measured using a sieve. However, Patent Document 2 mainly evaluates the accuracy in the case of using a single particle size sample and a mixed particle size deposit in a deposited state in a tray. According to the study by the present inventors, when using a single particle size sample and a mixed particle size deposit that are conveyed in a deposited state on a belt conveyor, as described below, it has been found that in some cases, the method described in Patent Document 2 cannot calculate the particle size distribution (overall mass distribution) with sufficient accuracy.

[0009] First, the present inventors calculated the particle size distribution of a single particle size sample that is conveyed in a deposited state on a belt conveyor. Figure 1 shows an example of the results of calculating the first particle size distribution of a single-particle-size sample that is piled up and transported on a belt conveyor. Specifically, the results shown in Figure 1 show a single-particle-size sample in particle size category 1 consisting only of particles (coke particles) that pass through a sieve with a mesh size of 38 mm but not a sieve with a mesh size of 25 mm (i.e., 25 mm<particle size≦38 mm), a single-particle-size sample in particle size category 2 consisting only of particles (coke particles) that pass through a sieve with a mesh size of 50 mm but not a sieve with a mesh size of 38 mm (i.e., 38 mm<particle size≦50 mm), and a single-particle-size sample in particle size category 3 consisting only of particles (coke particles) that pass through a sieve with a mesh size of 75 mm but not a sieve with a mesh size of 50 mm. A certain amount of mass of single-grain size samples of grain size category 3 consisting only of particles (coke) that do not pass through the sieve (i.e., 50mm<grain size≦75mm) were piled on a belt conveyor, and images of each were taken with a 3D camera (a 3D camera using a light-cutting method with linear laser light) placed above the belt conveyor. The first grain size distribution (relationship between grain size and number of surface layer particles of the single-grain size sample) calculated based on the acquired distance images is summarized and illustrated. The first grain size distribution was calculated by counting the number of surface layer particles for each grain size range at 5mm intervals. In addition, although the results are not shown in the figures, the inventors also calculated a second particle size distribution for each of a number of mixed particle size deposits, which were transported in a piled-up state on a conveyor belt, based on distance images acquired by a 3D camera positioned above the conveyor belt, in a similar manner for a number of mixed particle size deposits, in which particles (coke particles) belonging to each of particle size divisions 1 to 3 were mixed in different predetermined mass ratios and were transported in a piled-up state on a conveyor belt. The inventors then used the calculated first particle size distribution shown in FIG. 1 and the calculated second particle size distribution to calculate the total mass distribution of each mixed grain size deposit by applying the method described in Patent Document 2.

[0010] Figures 2 and 3 show examples of the results of calculating the overall mass distribution of a mixed-grain-size deposit transported in a piled-up state on a belt conveyor. Figure 2(a) shows the results obtained for a mixed-grain-size deposit containing 19.2% particles in grain size division 1, 44.4% particles in grain size division 2, and 36.4% particles in grain size division 3 (hereinafter referred to as "mixed-grain-size deposit No. 1") by mass. Figure 2(b) shows the results obtained for a mixed-grain-size deposit containing 17.4% particles in grain size division 1, 42.8% particles in grain size division 2, and 39.8% particles in grain size division 3 (hereinafter referred to as "mixed-grain-size deposit No. 2") by mass. Figure 2(c) shows the results obtained for a mixed-grain sediment with a mass ratio of 21.6% particles in size division 1, 48.7% particles in size division 2, and 29.7% particles in size division 3 (hereinafter referred to as "mixed-grain sediment No. 3"). Figure 2(d) shows the results obtained for a mixed-grain sediment with a mass ratio of 11.2% particles in size division 1, 46.0% particles in size division 2, and 42.7% particles in size division 3 (hereinafter referred to as "mixed-grain sediment No. 4"). Figure 3(a) shows the results obtained for a mixed-grain sediment with a mass ratio of 2.3% particles in size division 1, 36.1% particles in size division 2, and 61.6% particles in size division 3 (hereinafter referred to as "mixed-grain sediment No. 5"). Figure 3(b) shows the results obtained for a mixed-grain-size deposit (hereinafter referred to as "Mixed-grain-size deposit No. 6") containing 2.2% particles in grain size category 1, 30.8% particles in grain size category 2, and 67.1% particles in grain size category 3 by mass. In Figures 2 and 3, the graphs marked "Sieve" show data measured using a sieve on samples taken from the mixed-grain-size deposit (mass ratios reflecting the actual state of the particles), and the graphs marked "3D" show data calculated by the method described in Patent Document 2 using a 3D camera.

[0011] As shown in Fig. 3, for mixed-grain-size deposits No. 5 and No. 6, which have a large mass ratio of large particles, the overall mass distribution of the mixed-grain-size deposit calculated by the method described in Patent Document 2 is relatively consistent with the result measured by sieving. However, as shown in Fig. 2, for mixed-grain-size deposits No. 1 to No. 4, which have a large mass ratio of small particles (the mass ratio is a mountain-shaped mass ratio with the largest mass ratio of grain size class 2), the overall mass distribution of the mixed-grain-size deposit calculated by the method described in Patent Document 2 is not sufficiently consistent with the result measured by sieving. The inventors consider that this is because the mixture of particles of different grain sizes is not uniform on the belt conveyor, and grain size segregation occurs in the height (bulk height) direction of the mixed-grain-size deposit, causing more large grains to appear on the surface layer of the mixed-grain-size deposit than estimated by the surface probability model.

[0012] As described above, it has been found that for mixed-grain deposits that are piled up and transported on a conveyor belt, the method described in Patent Document 2 may not be able to calculate the grain size distribution (total mass distribution) with sufficient accuracy. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2019-174155 A [Patent Document 2] Patent Publication No. 2022-172620 [Non-patent literature]

[0014] [Non-Patent Document 1] MJ Thurley, "Automated, On-line, Calibration-Free, Particle Size Measurement using 3D Profile Data", Measurement and Analysis of Blast Fragmentation: Workshop Hosted by FRAGBLAST 10 - The 10th International Symposium on Rock Fragmentation by Blasting, 2013, pp.23-32 [Non-Patent Document 2] MJ Thurley, "Three Dimensional Data Analysis for the Separation and Sizing of Rock Piles in Mining", Ph.D. Thesis, Monash University, December 2002, chapter 4, pp.27-60 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention aims to provide a particle size distribution measuring method capable of accurately calculating the particle size distribution, i.e., the overall mass distribution, which is the relationship between the particle size classes and the total mass proportion of particles in each particle size class of a mixed particle size deposit body, which is a mixture of particles belonging to multiple particle size classes and is transported in a piled-up state on a conveyor belt. [Means for solving the problem]

[0016] In order to solve the above problems, the present inventors have conducted extensive research to improve the method described in Patent Document 2. First, the inventors have considered measuring the overall mass distribution of a reference mixed-grain-size deposit, which is a mixed-grain-size deposit transported in a piled state on a belt conveyer, using a sieve (i.e., measuring the mass ratio reflecting the actual state of the particles blended in the reference mixed-grain-size deposit), and calculating the surface number distribution of the reference mixed-grain-size deposit (the relationship between the grain size division and the surface number ratio, which is the number ratio of surface layer particles for each grain size division of the reference mixed-grain-size deposit) by performing the reverse procedure of the method described in Patent Document 2 using a surface probability model. On the other hand, we considered assuming a first particle size distribution for a single-grain sample, which is a sample consisting only of particles having a particle size that falls within the same grain size division among the multiple grain size divisions to which the particles mixed in the reference mixed-grain sediment belong, for each of the multiple grain size divisions using an unknown constant. Then, the surface layer of the reference mixed-grain-size deposit body being piled up and transported on a conveyor belt is imaged, and a second particle size distribution of the reference mixed-grain-size deposit body is calculated based on the acquired distance image.Then, an unknown constant for the assumed first particle size distribution is determined so that this second particle size distribution is approximated by a linear sum of the first particle size distributions assumed for multiple particle size divisions, with the surface number ratio for each particle size division as a coefficient, and the first particle size distribution is calculated (determined) for each of the multiple particle size divisions. The inventors have discovered that by using the first particle size distribution calculated as described above for a target mixed-grain size sediment body, which is a mixed-grain size sediment body whose particle size distribution is to be measured, and performing a procedure similar to that described in Patent Document 2, it is possible to calculate an overall mass distribution with high accuracy that closely matches the results measured using a sieve, even for a target mixed-grain size sediment body that is transported in a piled state on a conveyor belt. The present invention has been completed based on the findings of the present inventors.

[0017] That is, in order to solve the above-mentioned problem, the present invention provides a first step of measuring, using a sieve, an overall mass distribution, which is a relationship between the particle size divisions and the mass proportion of the entire particles for each particle size division of the reference mixed particle size deposition body, for a reference mixed particle size deposition body that is a mixed particle size deposition body in which particles belonging to a plurality of particle size divisions are blended and that is transported in a piled-up state on a belt conveyor; and a second step of calculating, based on the overall mass distribution and a volume ratio calculated from the particle size divisions, an overall mass distribution, which is a relationship between the particle size divisions and the number proportion of the entire particles for each particle size division of the reference mixed particle size deposition body, for the reference mixed particle size deposition body. a second step of calculating a number distribution; a third step of calculating a surface number distribution showing a relationship between the grain size divisions and a surface number ratio, which is the number ratio of surface layer particles for each grain size division of the reference mixed-size sediment body, for the reference mixed-size sediment body based on a surface probability model that estimates the number distribution of all deposited particles from the number distribution of surface particles and the overall number distribution; and a third step of calculating a first grain size distribution showing the relationship between the grain size and the number of surface layer particles of a single grain size sample, which is a sample consisting only of particles having a grain size included in the same grain size division among the plurality of grain size divisions, using an unknown constant to estimate a surface number distribution for the plurality of grain size divisions. a fourth step of assuming a particle size distribution for each particle size division; a fifth step of imaging a surface layer of the reference mixed-grain-size deposit body transported in a piled-up state on the belt conveyor, acquiring a distance image showing the distance from a reference position to the surface layer particles, and calculating a second particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the reference mixed-grain-size deposit body based on the distance image; and a fifth step of determining the unknown constant so that the second particle size distribution is approximated by a linear sum of the first particle size distributions assumed for each of the plurality of particle size divisions, with the surface number ratio for each of the particle size divisions as a coefficient, and calculating the first particle size distribution for each of the plurality of particle size divisions. a sixth step of calculating a particle size distribution; a seventh step of imaging a surface layer of a target mixed-grain-size deposit body, which is the mixed-grain-size deposit body to be measured for particle size distribution and which is transported in a piled state on the belt conveyor, acquiring a distance image showing the distance from a reference position to the surface layer particles, and calculating the second particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the target mixed-grain-size deposit body based on the distance image; and an eighth step of approximating the second particle size distribution of the target mixed-grain-size deposit body with a linear sum of the first particle size distributions calculated for each of the multiple particle size divisions, and calculating a coefficient of the linear sum.a ninth step of calculating, from the coefficients of the linear sum using the surface probability model, an overall number distribution for the target mixed-grain size deposit body, which is a relationship between the grain size divisions and the total number ratio of particles for each grain size division of the target mixed-grain size deposit body; and a tenth step of calculating, based on the overall number distribution and the volume ratio calculated from the grain size divisions, an overall mass distribution for the target mixed-grain size deposit body, which is a relationship between the grain size divisions and the total mass ratio of particles for each grain size division of the target mixed-grain size deposit body.

[0018] In the present invention, the "volume ratio" refers to a value obtained by dividing a volume calculated from one particle size fraction by a reference volume, where the volume calculated from another particle size fraction is the reference volume. Moreover, the "surface probability model" is synonymous with the surface probability model described in Non-Patent Document 2, and is a model that expresses the degree of likelihood of appearing on the surface layer or visibility according to particle size. In other words, the surface probability model is a model that relates the number distribution of surface layer particles for each particle size classification to the number distribution of all the deposited particles, and is a model that estimates the number distribution of all the deposited particles from the number distribution of surface layer particles (conversely, it is also possible to estimate the number distribution of surface layer particles from the number distribution of all the deposited particles). Furthermore, the "distance image" means an image in which the pixel value of each pixel indicates the distance from a reference position (for example, the distance from the distance image acquisition means), the "distance image" acquired in the fifth step is an image indicating the distance from the reference position to the surface layer particles of the reference mixed grain size deposit body, and the "distance image" acquired in the seventh step is an image indicating the distance from the reference position to the surface layer particles of the target mixed grain size deposit body. The distance image acquisition means for acquiring the distance image is not particularly limited as long as it is a means capable of acquiring the distance to the target surface layer, but for example, a light-cutting type 3D camera in which a laser light source that emits linear laser light and an area scan camera are integrated can be mentioned. The reference position can be set at any position, and for example, the position of the distance image acquisition means can be set as the reference position. If the "distance image" can be acquired, for example, by using the method described in Non-Patent Document 2 or the like, a calculation device connected to the distance image acquisition means can perform a calculation based on the "distance image" to calculate the particle size and the number of particles.

[0019] The present invention has seventh to tenth steps as a process for actually measuring the particle size distribution of a target mixed-grain-size sediment body that is the subject of particle size distribution (total mass distribution) measurement. In addition, as a preparatory process prior to the above, the present invention has first to third and fifth steps performed using a reference mixed-grain-size sediment body, a fourth step for assuming a first particle size distribution of the single-grain-size sample, and a sixth step for calculating (determining) the first particle size distribution of the single-grain-size sample. Steps seven to ten are the same procedure as the method described in Patent Document 2, but steps one to six are different from the method described in Patent Document 2. According to the present invention, by using the first particle size distribution of the single-grain-size sample calculated by executing the first to sixth steps and executing the seventh to tenth steps similar to the method described in Patent Document 2, it is possible to calculate an overall mass distribution with good accuracy that closely matches the results measured using a sieve, even for a target mixed-grain-size sediment body transported in a piled state on a belt conveyer, as found by the inventors above. Furthermore, according to the present invention, since the first particle size distribution of the single-grain-size sample is assumed in the fourth step and the first particle size distribution of the single-grain-size sample is calculated (determined) in the sixth step, unlike the method described in Patent Document 2, it is not necessarily necessary to obtain a distance image of the single-grain-size sample, and the overall mass distribution of the target mixed-grain-size sediment body can be easily calculated.

[0020] In the present invention, the first to tenth steps do not necessarily have to be performed in this order, and various modes can be adopted in which the first to sixth steps, which are preparatory steps, are performed before the seventh to tenth steps, which are steps for measuring the grain size distribution of the target mixed-grain-size deposit body. For example, the fourth step may be performed before any of the first to third steps, or after the fifth step, as long as it is performed before the sixth step. Also, for example, the fifth step may be performed before any of the first to fourth steps, as long as it is performed before the sixth step.

[0021] In the fourth, fifth and seventh steps of the present invention described above, particle size distributions (first particle size distribution and second particle size distribution) that indicate the relationship between the particle size and the number of surface layer particles are assumed or calculated. However, according to the knowledge of the present inventors, one parameter of the relationship indicated by the particle size distribution is not necessarily limited to the number of surface layer particles, and instead, the total mass distribution of the target mixed-grain sediment body can be calculated with high accuracy even if a particle size distribution that indicates the relationship between the particle size and the area or volume of the surface layer particles is used. Therefore, in the fourth step, instead of a first particle size distribution showing the relationship between the particle size and number of the surface particles of the single-grain-size sample, a first particle size distribution showing the relationship between the particle size and area of ​​the surface particles of the single-grain-size sample is assumed, in the fifth step, instead of a second particle size distribution showing the relationship between the particle size and number of the surface particles of the reference mixed sediment body, a second particle size distribution showing the relationship between the particle size and area of ​​the surface particles of the reference mixed sediment body is calculated, and in the seventh step, instead of a second particle size distribution showing the relationship between the particle size and number of the surface particles of the target mixed sediment body, a second particle size distribution showing the relationship between the particle size and area of ​​the surface particles of the target mixed sediment body is calculated. Alternatively, in the fourth step, instead of a first particle size distribution showing the relationship between the particle size and the number of the surface particles of the single-particle-size sample, a first particle size distribution showing the relationship between the particle size and the volume of the surface particles of the single-particle-size sample is assumed, in the fifth step, instead of a second particle size distribution showing the relationship between the particle size and the number of the surface particles of the reference mixed sediment body, a second particle size distribution showing the relationship between the particle size and the volume of the surface particles of the reference mixed sediment body is calculated, and in the seventh step, instead of a second particle size distribution showing the relationship between the particle size and the number of the surface particles of the target mixed sediment body, a second particle size distribution showing the relationship between the particle size and the volume of the surface particles of the target mixed sediment body is calculated. Effect of the Invention

[0022] According to the present invention, it is possible to accurately calculate the particle size distribution, i.e., the overall mass distribution, which is the relationship between the particle size classes and the total mass proportion of particles in each particle size class of the mixed particle size deposit, for a mixed particle size deposit containing particles belonging to multiple particle size classes that are transported in a piled-up state on a conveyor belt. [Brief description of the drawings]

[0023] [Figure 1] An example of the results of calculating the first particle size distribution of a single particle size sample transported in a piled state on a belt conveyor is shown. [Diagram 2] An example of the results of calculating the overall mass distribution of a mixed grain size pile transported in a piled state on a belt conveyor is shown. [Diagram 3] An example of the results of calculating the overall mass distribution of a mixed grain size pile transported in a piled state on a belt conveyor is shown. [Figure 4] FIG. 1 is a diagram illustrating a schematic configuration of an apparatus for carrying out a particle size distribution measuring method according to an embodiment of the present invention. [Diagram 5] FIG. 1 is a flow diagram showing steps of a particle size distribution measuring method according to one embodiment of the present invention. [Figure 6] 6 is a flow chart showing steps included in a preparation process ST1 shown in FIG. 5. [Figure 7] FIG. 6 is an explanatory diagram for illustrating a preparation step ST1 shown in FIG. 5. [Figure 8] FIG. 6 is a flow diagram showing steps included in a particle size distribution measuring step ST2 shown in FIG. [Figure 9] 4 shows the second grain size distribution of the reference mixed grain size deposit used in Example 1 and the calculated first grain size distribution. [Figure 10] In Example 1, the results of calculating the overall mass distribution of mixed grain size deposit bodies No. 1 to No. 4 are shown. [Figure 11] In Example 1, the results of calculating the overall mass distribution of mixed grain size deposits No. 5 and No. 6 are shown. [Figure 12] 1 shows the first particle size distribution of the single particle size samples calculated in Examples 2 and 3. [Figure 13] The results of evaluating the root mean square error between the overall mass distribution of mixed-grain-size deposit bodies No. 1 to No. 6 calculated in Examples 1 to 7 and the overall mass distribution of mixed-grain-size deposit bodies No. 1 to No. 6 measured in step ST11 shown in Figure 6 are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 4 is a diagram showing a schematic diagram of an apparatus for carrying out the particle size distribution measuring method according to the present embodiment. Fig. 5 is a flow diagram showing the steps of the particle size distribution measuring method according to the present embodiment. Fig. 6 is a flow diagram showing the steps of the preparation step ST1 shown in Fig. 5. Fig. 7 is an explanatory diagram for explaining the preparation step ST1 shown in Fig. 5. As shown in Fig. 4, when blast furnace raw materials such as coke and sintered ore are charged into the blast furnace BF, a sample in which single-particle-size samples consisting of only particles having the same particle size classification are mixed at a predetermined mass ratio and stored in a hopper H is discharged from the hopper H onto a belt conveyor BC, and a mixed-particle-size deposit M in which the single-particle-size samples are mixed and deposited at a predetermined mass ratio is transported by the belt conveyor BC and charged into the blast furnace BF. The particle size distribution measuring method according to this embodiment is performed using a 3D camera 1 (a 3D camera using a light-cutting method using a linear laser light L) as a distance image acquisition means arranged above the belt conveyor BC, and a calculation device 2 connected to the 3D camera 1.

[0025] As shown in Fig. 5, the particle size distribution measuring method according to this embodiment includes a preparation step ST1 and a particle size distribution measuring step ST2. As shown in Fig. 6, the preparation step ST1 includes steps ST11 to ST16. Hereinafter, each of the steps ST11 to ST16 included in the preparation step ST1 will be described in order. Note that in this embodiment, an example will be described in which a particle size distribution (total mass distribution) of a mixed particle size laminate (target mixed particle size deposit) containing particles belonging to three particle size divisions as a plurality of particle size divisions is measured, but the present invention is not limited thereto, and can also be applied to a mixed particle size laminate containing particles belonging to two particle size divisions or four or more particle size divisions.

[0026] [Preparation process ST1] <Step ST11> In step ST11 (corresponding to the first step of the present invention), for a reference mixed-grain-size deposit M, which is a mixed-grain-size deposit containing particles belonging to multiple grain-size classes (in this embodiment, three grain-size classes: grain-size class 1 of 25 mm<grain size≦38 mm, grain-size class 2 of 38 mm<grain size≦50 mm, and grain-size class 3 of 50 mm<grain size≦75 mm) transported in a piled-up state on the belt conveyor BC, a total mass distribution, which is a relationship between the grain-size classes and the total mass proportion of particles for each grain-size class of the reference mixed-grain-size deposit, is measured using a sieve. Specifically, for example, a sample obtained by sampling a portion of the mixed-grain-size deposit M transported on the belt conveyor BC is used to measure the total mass distribution.

[0027] <Step ST12> In steps ST12 and ST13 described later, the procedure is reversed from that of the method described in Patent Document 2. In step ST12 (corresponding to the second step of the present invention), based on the overall mass distribution measured in step ST11 and the volume ratio calculated from the particle size divisions, an overall number distribution, which is the relationship between the particle size divisions and the total number ratio of particles for each particle size division of the reference mixed particle size deposit, is calculated for the reference mixed particle size deposit. Table 1 shows the median grain size D corresponding to grain size category i (i = 1 to 3). i , area ratio A i and volume ratio V i Shows. [Table 1] The median value D of the grain size of grain size class i i means the average value of the upper limit and the lower limit of the particle size division i, and in this embodiment, D 1 =(25+38) / 2=31.5mm, D 2 =(38+50) / 2=44mm, D 3 =(50+75) / 2=62.5mm. Area ratio A of grain size class i i means a value obtained by dividing an area calculated from one particle size division by the reference area when the area calculated from the other particle size division is set as the reference area. In this embodiment, the area ratio A iThe area of ​​grain size category 1 is set to 1 (i.e., the area ratio A 1 = 1) i It is expressed as the ratio of the squares of Volume ratio V of particle size class i i means a value obtained by dividing a volume calculated from one particle size division by the reference volume when the volume calculated from the other particle size division is set as the reference volume. In this embodiment, the volume ratio V i The volume of grain size category 1 is set to 1 (i.e., the volume ratio V 1 = 1) i It is expressed as the ratio of the cube of . The number ratio N of all particles in each grain size class i in the total number distribution of the reference mixed grain size sediment i is the mass ratio of all particles for each particle size class i in the total mass distribution measured in step ST11. i Then, it can be calculated using the following formula (1).

number

[0028] <Step ST13> In step ST13 (corresponding to the third step of the present invention), a surface number distribution showing the relationship between the grain size class i and the surface number ratio, which is the number ratio of surface layer particles for each grain size class i of the reference mixed grain size deposit body, is calculated for the reference mixed grain size deposit body based on a surface probability model that estimates the number distribution of all deposited particles from the number distribution of surface layer particles and the total number distribution calculated in step ST12. The surface probability model used in step ST13 is the same as the surface probability model described in Patent Document 2. Specifically, in step ST13, the surface number distribution of the reference mixed-grain-size deposit body is calculated using a surface probability model expressed by the following equation (2).

number

[0029] The surface probability P in Eq. i is expressed by the following formula (3), and more specifically, by the following formulas (4) to (7).

number

number

number

number

number

[0030] In step ST13, the above-mentioned formulas (2) to (7) and the ratio N of the number of all particles for each particle size class i in the total number distribution calculated in step ST12 are calculated. i Based on this, the grain size class i of the reference mixed grain sediment and the surface number ratio E(X i ) is calculated. In the example shown in FIG. 7(a), the surface number distribution showing the relationship between the surface number ratio E(X i ) to k i The surface number ratio of grain size class 1 is k 1 , surface number ratio k of grain size category 2 2 , surface number ratio k of grain size category 3 3 has been calculated.

[0031] <Step ST14> In step ST14 (corresponding to the fourth step of the present invention), a first particle size distribution showing the relationship between the particle size and the number of surface particles in a single-particle-size sample, which is a sample consisting only of particles having a particle size included in the same particle size division i out of multiple (three) particle size divisions i, is assumed for each of the multiple (three) particle size divisions i using an unknown constant. Specifically, the first particle size distribution f i As for (x) (x is particle size), a Gaussian distribution function represented by the following formula (8a) or a Cauchy distribution function represented by the following formula (8b) as shown in FIG. 7(b) is assumed. Alternatively, when the first particle size distribution of a single particle size sample as shown in FIG. 1 is actually measured using a 3D camera 1 and a calculation device 2, the actually measured first particle size distribution g i (x) with unknown constant a i In equations (8a) and (8b), the unknown constant is a i , b i , c i Therefore, the first particle size distribution f i (x) to f i (x,a i ,b i ,c i In equation (8c), the unknown constant is a iTherefore, the first particle size distribution f i (x) to f i (x,a i ) is used.

number

[0032] <Step ST15> In step ST15 (corresponding to the fifth step of the present invention), the surface layer of the reference mixed-grain size deposit body transported in a piled state on the belt conveyor BC is imaged by the 3D camera 1, a distance image showing the distance from the reference position to the surface layer particles is obtained, and the calculation device 2 measures the particle sizes of the surface layer particles of the reference mixed-grain size deposit body based on the distance image. This calculates a second particle size distribution G(x) showing the relationship between the particle size and the number of the surface layer particles of the reference mixed-grain size deposit body, as shown by the solid line in Figure 7(c).

[0033] <Step ST16> In step ST16 (corresponding to the sixth step of the present invention), as shown in FIG. 7(c), the second particle size distribution G(x) calculated in step ST15 is calculated based on the surface number ratio for each particle size division i calculated in step ST13 (k i ) is the coefficient of the first particle size distribution f i (x) (in the example shown in FIG. 7(c), the first particle size distribution f i (x,a i ,b i ,c i ) to be approximated by F(x), which is a linear sum ofi ,b i ,c i , and k i and f i (x,a i ,b i ,c i ) and determine the unknown constant p) multiplied by the linear sum of the products of the two, and obtain the first particle size distribution f for each of the multiple (three) particle size classes i. i Calculate (determine) (x). Specifically, for example, when all of the mixed-grain-size deposit bodies No. 1 to No. 6 described with reference to FIG. 2 and FIG. 3 are used as reference mixed-grain-size deposit bodies, in step ST13, the surface number ratio k for each grain size division i for each reference mixed-grain-size deposit body No. j (j=1 to 6) is calculated. i is calculated, so we call this k ji In addition, the constant p for the reference mixed grain size sediment No. j is p j Furthermore, the first grain size distribution f i Let F be the linear sum of (x). j (x). In this case, the first particle size distribution f i (x) is f i (x,a i ,b i ,c i ), then the linear sum F j (x) is expressed by the following equation (9).

number

[0034] In addition, the first particle size distribution f i As the reference mixed-grain-size sediment body used to calculate (determine) (x), it is not necessarily necessary to use a plurality of mixed-grain-size sediment bodies (mixed-grain-size sediment bodies No. 1 to No. 6) as described above, and it is also possible to use a single mixed-grain-size sediment body. Also, for example, the first grain size distribution f can be determined by using one reference mixed-grain-size sediment body selected from the mixed-grain-size sediment bodies (mixed-grain-size sediment bodies No. 1 to No. 4) having a large mass ratio of small grains as shown in FIG. 2 and one reference mixed-grain-size sediment body selected from the mixed-grain-size sediment bodies (mixed-grain-size sediment bodies No. 5 and No. 6) having a large mass ratio of large grains as shown in FIG. 3. i In this way, by using mixed-grain-size sediment bodies having different grain-size distribution tendencies as reference mixed-grain-size sediment bodies, it is expected that the measurement accuracy of the grain-size distribution (total mass distribution) of the target mixed-grain-size sediment body measured in the grain-size distribution measurement step ST2 described later can be improved.

[0035] By the above-described preparation step ST1 (steps ST11 to ST16), the first particle size distribution f of the single particle size sample is obtained for each of the plurality (three) particle size divisions i. i (x) is calculated, and this first particle size distribution f i (x) is used in the particle size distribution measuring step ST2 described below.

[0036] [Particle size distribution measurement process ST2] FIG. 8 is a flow diagram showing steps included in the particle size distribution measuring step ST2 shown in FIG. 8, the particle size distribution measuring step ST2 includes steps ST21 to ST24. Each of steps ST21 to ST24 included in the particle size distribution measuring step ST2 will be described below in order.

[0037] <Step ST21> In step ST21 (corresponding to the seventh step of the present invention), the surface layer of the target mixed-grain-size deposit body, which is the mixed deposit body M to be measured for particle-size distribution and which is transported in a piled state on the belt conveyor BC, is imaged by the 3D camera 1, a distance image showing the distance from a reference position to the surface layer particles is obtained, and the calculation device 2 measures the particle sizes of the surface layer particles of the target mixed-grain-size deposit body based on the distance image. This calculates a second particle size distribution showing the relationship between the particle size and the number of surface layer particles of the target mixed-grain-size deposit body.

[0038] <Step ST22> In step ST22 (corresponding to the eighth step of the present invention), the second grain size distribution of the target mixed grain size sediment body calculated in step ST21 is compared with the first grain size distribution f calculated for each of the plurality of grain size divisions i in step ST16. i Approximate with a linear sum of (x) and calculate the coefficient of the linear sum.

[0039] <Step ST23> In step ST23 (corresponding to step 9 of the present invention), a surface probability model is used to calculate an overall number distribution, which is a relationship between the grain size division i and the overall number ratio of particles for each grain size division i of the target mixed-grain size deposit body, for the target mixed-grain size deposit body from the coefficients of the linear sum calculated in step ST22. The surface probability model used in step ST23 is also the same as the surface probability model described in Patent Document 2.

[0040] <Step ST24> In step ST24 (corresponding to step 10 of the present invention), the total number distribution calculated in step ST23 and the volume ratio V calculated from the particle size division i are i Based on the above, a total mass distribution is calculated for the target mixed-grain-size sediment body, which is the relationship between the grain size division i and the total mass ratio of particles for each grain size division i of the target mixed-grain-size sediment body.

[0041] The particle size distribution measurement step ST2 (steps ST21 to ST24) described above is carried out by measuring the first particle size distribution f i Except for the use of (x), the method is similar to the method described in Patent Document 2, and therefore further detailed description will be omitted.

[0042] According to the particle size distribution measuring method of the present embodiment, the first particle size distribution f of the single particle size sample is calculated by performing the preparation step ST1. i By executing the particle size distribution measurement step ST2 similar to the method described in Patent Document 2 using (x), it is possible to calculate an overall mass distribution with good accuracy that closely matches the result of measurement using a sieve, even for the target mixed particle size deposit transported in a piled state on the belt conveyor BC. Also, according to the particle size distribution measurement method of this embodiment, the first particle size distribution f of the single particle size sample is calculated in step ST14. i Assuming (x), the first particle size distribution f of the single particle size sample is calculated in step ST16. i Unlike the method described in Patent Document 2, in order to calculate (determine) (x), it is not necessary to acquire a distance image of a single grain size sample, and it is possible to easily calculate the overall mass distribution of the target mixed grain size deposit.

[0043] In this embodiment, in steps ST14, ST15, and ST21, particle size distributions (first particle size distribution and second particle size distribution) showing the relationship between the particle size and the number of surface layer particles are assumed or calculated. However, the present invention is not limited to this. Although the explanation of the results is omitted, according to the knowledge of the inventors, one parameter of the relationship shown by the particle size distribution is not necessarily limited to the number of surface layer particles, and instead, even if a particle size distribution showing the relationship between the particle size of the surface layer particles and the area or volume is used, the overall mass distribution of the target mixed-grain sediment body can be calculated with high accuracy.

[0044] [Example] Hereinafter, as an example, an example of the results of calculating the total mass distribution by the particle size distribution measuring method according to this embodiment will be described.

[0045] <Example 1> In Example 1, a Sick "Ruler E1200" (area scan camera pixel count: 1024 x 512, measurement speed: 10,000 cross sections / second) was used as the 3D camera 1, and the height from the belt conveyor BC to the 3D camera 1 was adjusted so that the 1200 mm width of the belt conveyor BC on which the coke particles had accumulated was within the field of view. In addition, the travel distance was detected by a rotary encoder installed on the belt conveyor BC, and the belt conveyor BC was set to acquire one distance image every time it traveled 3.3 m.

[0046] In Example 1, in the preparation step ST1, all of the mixed-grain-size deposit bodies No. 1 to No. 6 described above with reference to Figures 2 and 3 were used as candidates for the reference mixed-grain-size deposit body. Then, for each of the mixed-grain-size deposit bodies No. 1 to No. 6, the total mass distribution was measured in step ST11, the total number distribution was calculated in step ST12, and the surface number distribution was calculated in step ST13. Table 2 shows the measured total mass distribution, calculated total number distribution and surface number distribution for each of mixed-grain-size deposit bodies No. 1 to No. 6. The heights H of mixed-grain-size deposit bodies No. 1 to No. 6 shown in Table 2 were measured (calculated) using distance images acquired by 3D camera 1 and the method described in Patent Document 2, which approximates the cross section of each mixed-grain-size deposit body deposited on the belt conveyor BC as a trapezoid. [Table 2]

[0047] In Example 1, in step ST14, the first particle size distribution f of each particle size division i (i = 1 to 3) of the single particle size sample is i For (x), we assumed the Gaussian distribution function expressed by the above equation (8a).

[0048] In Example 1, in step ST15, the surface layers of the mixed-particle-size deposit bodies No. 1 to No. 6 transported in a piled state on the belt conveyor BC were imaged by the 3D camera 1, and the particle sizes of the surface layer particles were measured based on the distance images by the calculation device 2, and the second particle size distribution G(x) of the mixed-particle-size deposit bodies No. 1 to No. 6 was calculated. The second particle size distribution G(x) was calculated by counting the number of surface layer particles for each particle size range at 5 mm intervals using distance images of a number corresponding to one pile of mixed-particle-size deposit bodies simultaneously charged into the blast furnace BF.

[0049] In the first embodiment, in step ST16, one mixed-grain-size deposit body is selected from the four mixed-grain-size deposit bodies No. 1 to No. 4 that are candidates for the reference mixed-grain-size deposit body, and one mixed-grain-size deposit body is selected from the two mixed-grain-size deposit bodies No. 5 and No. 6 that are candidates for the reference mixed-grain-size deposit body and combined (the combinations of the selected mixed-grain-size deposit bodies are 4×2=8 pairs), and the first grain size distribution f i (x) (In Example 1, f represented by formula (8a) i (x,a i ,b i ,c i Specifically, for each combination, the linear sum F j Calculate (x) and linear sum F for each combination j (x) and second particle size distribution G j (x) Squared sum of differences Σ(F j (x)-G j (x) 2 The first particle size distribution f is minimized by using a nonlinear optimization method. i (x,a i ,b i ,c i ) unknown constant a i , b i , c i and the unknown constant p j It was decided that: In Example 1, the first particle size distribution f i(x) were used to perform the particle size distribution measurement step ST2 to calculate the overall mass distribution of the mixed-grain-size deposit bodies No. 1 to No. 6 (however, in Example 1, since the mixed-grain-size deposit bodies No. 1 to No. 6 were also used as the target mixed-grain-size deposit bodies, step ST21 of the particle size distribution measurement step ST2 was not performed, and the overall mass distribution was calculated directly using the second particle size distribution calculated in step ST15), and the root mean square error between the calculated overall mass distribution of the mixed-grain-size deposit bodies No. 1 to No. 6 and the overall mass distribution of the mixed-grain-size deposit bodies No. 1 to No. 6 measured in step ST11 was evaluated. As a result, the first particle size distribution f i Since the root mean square error was smallest when (x) was used, it was decided to use the mixed-grain-size deposit bodies No. 2 and No. 6 as the reference mixed-grain-size deposit bodies in Example 1. Fig. 9 shows the second grain size distribution and the calculated first grain size distribution of the reference mixed-grain-size deposit body used in Example 1. Fig. 9(a) shows the second grain size distribution of the mixed-grain-size deposit bodies No. 2 and No. 6 used as the reference mixed-grain-size deposit bodies, and Fig. 9(b) shows the first grain size distribution of the single-grain-size sample calculated when the mixed-grain-size deposit bodies No. 2 and No. 6 are used as the reference mixed-grain-size deposit bodies.

[0050] 10 and 11 show the results of calculating the overall mass distribution of mixed-grain-size deposits No. 1 to No. 6 in Example 1. FIG. 10(a) shows the results obtained for mixed-grain-size deposit No. 1. FIG. 10(b) shows the results obtained for mixed-grain-size deposit No. 2. FIG. 10(c) shows the results obtained for mixed-grain-size deposit No. 3. FIG. 10(d) shows the results obtained for mixed-grain-size deposit No. 4. FIG. 11(a) shows the results obtained for mixed-grain-size deposit No. 5. FIG. 11(b) shows the results obtained for mixed-grain-size deposit No. 6. In FIG. 10 and FIG. 11, the graphs indicated by "sieve" are data measured using a sieve for samples sampled from mixed-grain-size deposits No. 1 to No. 6 (mass ratio reflecting the actual state of the blended particles), and the graphs indicated by "3D" are data calculated using the particle size distribution measuring method according to this embodiment using a 3D camera 1. As shown in Figures 10 and 11, the total mass distribution of the mixed-grain-size deposit calculated in Example 1 matched with good accuracy with the results measured using a sieve. As can be seen by comparing Figures 2 and 10, the results matched with sufficient accuracy even for mixed-grain-size deposits Nos. 1 to 4, which have a high mass ratio of small particles and did not match with sufficient accuracy using the method described in Patent Document 2.

[0051] <Example 2> In Example 2, in step ST14 of the preparation process ST1, the first particle size distribution f 1 (x), f 2 Assuming that (x) is the Cauchy distribution function expressed by the above formula (8b), the first particle size distribution f 3 (x) is the actually measured first particle size distribution g represented by the above formula (8c) 3 (x) with unknown constant a 3 The first grain size distribution f was calculated using the mixed grain size deposits No. 2 and No. 6 as the reference mixed grain size deposits in the same manner as in Example 1, except that the first grain size distribution f i (x) is calculated (determined), and this first particle size distribution f i (x) was used to calculate the overall mass distribution of mixed-grain deposits No. 1 to No. 6. FIG. 12(a) shows the first particle size distribution f i (x) is shown.

[0052] <Example 3> In Example 3, in step ST14 of the preparation process ST1, the first particle size distribution f 1 Assuming that the Cauchy distribution function expressed by the above formula (8b) is used as (x), the first particle size distribution f 2 (x), f 3 (x) is the actually measured first particle size distribution g represented by the above formula (8c) 2 (x), g 3 (x) each have an unknown constant a 2 , a 3The first grain size distribution f was calculated using the mixed grain size deposits No. 2 and No. 6 as the reference mixed grain size deposits in the same manner as in Example 1, except that the first grain size distribution f i (x) is calculated (determined), and this first particle size distribution f i (x) was used to calculate the overall mass distribution of mixed-grain deposits No. 1 to No. 6. FIG. 12(b) shows the first particle size distribution f i (x) is shown.

[0053] <Example 4> In Example 4, in step ST14 of the preparation process ST1, the first particle size distribution f of each particle size division i (i = 1 to 3) of the single particle size sample is i (x) is the actually measured first particle size distribution g represented by the above formula (8c) i (x) with unknown constant a i The first grain size distribution f was calculated using the mixed grain size deposits No. 2 and No. 6 as the reference mixed grain size deposits in the same manner as in Example 1, except that the first grain size distribution f i (x) is calculated (determined), and this first particle size distribution f i (x) was used to calculate the overall mass distribution of mixed-grain deposits No. 1 to No. 6.

[0054] <Example 5> In Example 5, in step ST14 of the preparation process ST1, the first particle size distribution f of each particle size division i (i = 1 to 3) of the single particle size sample is i The first grain size distribution f was calculated using the mixed grain size sediments No. 2 and No. 6 as reference mixed grain size sediments in the same manner as in Example 1, except that the Cauchy distribution function expressed by the above-mentioned formula (8b) was assumed as (x). i (x) is calculated (determined), and this first particle size distribution f i (x) was used to calculate the overall mass distribution of mixed-grain deposits No. 1 to No. 6.

[0055] <Example 6> In Example 6, in step ST14 of the preparation process ST1, the first particle size distribution f 1Assuming that the Cauchy distribution function expressed by the above formula (8b) is used as (x), the first particle size distribution f 2 (x), f 3 The first grain size distribution f was calculated using the mixed grain size deposits No. 2 and No. 6 as reference mixed grain size deposits in the same manner as in Example 1, except that the Gaussian distribution function expressed by the above-mentioned formula (8a) was assumed as (x). i (x) is calculated (determined), and this first particle size distribution f i (x) was used to calculate the overall mass distribution of mixed-grain deposits No. 1 to No. 6.

[0056] <Example 7> In Example 6, in step ST14 of the preparation process ST1, the first particle size distribution f of the particle size classes 1 and 3 of the single particle size sample is 1 (x), f 3 Assuming the Cauchy distribution function expressed by the above formula (8b) as (x), the first particle size distribution f 2 The first grain size distribution f was calculated using the mixed grain size deposits No. 2 and No. 6 as reference mixed grain size deposits in the same manner as in Example 1, except that the Gaussian distribution function expressed by the above-mentioned formula (8a) was assumed as (x). i (x) is calculated (determined), and this first particle size distribution f i (x) was used to calculate the overall mass distribution of mixed-grain deposits No. 1 to No. 6.

[0057] FIG. 13 shows the results of evaluating the root mean square error between the total mass distribution of mixed-grain-size deposit bodies No. 1 to No. 6 calculated in Examples 1 to 7 and the total mass distribution of mixed-grain-size deposit bodies No. 1 to No. 6 measured in step ST11. As shown in FIG. 13, the values ​​of the root mean square error were small for all of Examples 1 to 7, and it was confirmed that the particle size distribution measuring method according to this embodiment can accurately calculate the overall mass distribution of a mixed particle size deposit. [Explanation of symbols]

[0058] 1. 3D camera (means for acquiring distance images) 2...Arithmetic unit BC···Belt conveyor M···Mixed particle size accumulation

Claims

1. a first step of measuring, using a sieve, an overall mass distribution, which is a relationship between the particle size classes and the overall mass ratio of the particles in each particle size class of the reference mixed particle size class, for a reference mixed particle size class, which is a mixed particle size class that is conveyed in a piled-up state on a belt conveyor; a second step of calculating an overall number distribution for the reference mixed grain size deposit body, the overall number distribution being a relationship between the grain size divisions and the overall number ratio of particles for each grain size division of the reference mixed grain size deposit body, based on the overall mass distribution and the volume ratio calculated from the grain size divisions; a third step of calculating a surface number distribution indicating a relationship between the particle size classes and a surface number ratio, which is the number ratio of surface layer particles for each particle size class of the reference mixed-size deposit body, for the reference mixed-size deposit body based on a surface probability model that estimates the number distribution of all deposited particles from the number distribution of surface layer particles and the total number distribution; a fourth step of assuming, for each of the plurality of particle size divisions, a first particle size distribution that indicates a relationship between the particle size and the number of surface layer particles of a single particle size sample, which is a sample consisting of only particles having a particle size included in the same particle size division among the plurality of particle size divisions, using an unknown constant; a fifth step of imaging a surface layer of the reference mixed grain size deposit body transported in a piled state on the belt conveyor, acquiring a distance image showing a distance from a reference position to the surface layer particles, and calculating a second grain size distribution showing a relationship between the grain size and the number of the surface layer particles of the reference mixed grain size deposit body based on the distance image; A sixth step of determining the unknown constant so that the second particle size distribution is approximated by a linear sum of the first particle size distributions assumed for the plurality of particle size divisions, the coefficient of which is the surface number ratio for each of the particle size divisions, and calculating the first particle size distribution for each of the plurality of particle size divisions; a seventh step of imaging a surface layer of a target mixed-grain-size deposit body, which is the mixed-grain-size deposit body to be measured for particle size distribution and which is transported in a piled state on the belt conveyor, acquiring a distance image showing the distance from a reference position to the surface layer particles, and calculating the second particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the target mixed-grain-size deposit body based on the distance image; an eighth step of approximating the second particle size distribution of the target mixed-grain sediment body with a linear sum of the first particle size distributions calculated for each of the plurality of particle size ranges, and calculating a coefficient of the linear sum; a ninth step of calculating an overall number distribution for the target mixed-grain size deposit body, the overall number distribution being a relationship between the grain size divisions and the overall number ratio of particles for each grain size division of the target mixed-grain size deposit body, from the coefficients of the linear sum using the surface probability model; a tenth step of calculating an overall mass distribution of the target mixed-grain size deposit body, the overall mass distribution being a relationship between the grain size divisions and the overall mass ratio of particles in each grain size division of the target mixed-grain size deposit body, based on the overall number distribution and the volume ratio calculated from the grain size divisions; The particle size distribution measuring method according to claim 1,

2. In the fourth step, instead of the first particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the single particle size sample, a second particle size distribution showing the relationship between the particle size and the area of ​​the surface layer particles of the single particle size sample is assumed; In the fifth step, instead of the second particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the reference mixed sediment body, a second particle size distribution showing the relationship between the particle size and the area of ​​the surface layer particles of the reference mixed sediment body is calculated; The particle size distribution measuring method according to claim 1, wherein in the seventh step, a second particle size distribution showing the relationship between the particle size and area of ​​the surface particles of the target mixed sediment body is calculated instead of a second particle size distribution showing the relationship between the particle size and number of the surface particles of the target mixed sediment body.

3. In the fourth step, instead of the first particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the single particle size sample, a second particle size distribution showing the relationship between the particle size and the volume of the surface layer particles of the single particle size sample is assumed; In the fifth step, instead of the second particle size distribution indicating the relationship between the particle size and the number of the surface layer particles of the reference mixed sediment body, a second particle size distribution indicating the relationship between the particle size and the volume of the surface layer particles of the reference mixed sediment body is calculated; The particle size distribution measuring method according to claim 1, wherein in the seventh step, instead of the second particle size distribution showing the relationship between the particle size and the number of the surface layer particles of the target mixed sediment body, a second particle size distribution showing the relationship between the particle size and the volume of the surface layer particles of the target mixed sediment body is calculated.

Images