AU2019204680B1 - Sieving instrument and sieving method for detecting reliability of particle size distribution characteristics of granular material - Google Patents
Sieving instrument and sieving method for detecting reliability of particle size distribution characteristics of granular material Download PDFInfo
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Abstract
The present invention discloses a sieving instrument and a sieving method for detecting the
reliability of particle size distribution characteristics of granular material. The sieving
instrument comprises a base plate, an elastic vibration module, an upright column, a frame
beam, a vibration table mounted on the elastic vibration module, and the sieve box is
arranged on the vibration table; the elastic vibration module, the upright column and the
frame beam are mounted on the base plate; a feeding box is fixedly mounted at the upper
part of the frame beam, and an outlet of the feeding box extends into the sieve box; carrying
platform are mounted on the upright column, a plurality of storage boxes are arranged on the
carrying platform; the sieve box is divided into a plurality of grids from bottom to top by a
plurality of sieve pore plates arranged horizontally, and one storage box is correspondingly
arranged at the discharge port of each grid, and the discharge port of each grid is aligned
with the feeding port of the corresponding storage box; and the vibration table tilts on one
side. The sieving instrument is quick and convenient to use, and reliable in accuracy.
Description
Sieving instrument and sieving method for detecting reliability of particle size distribution characteristics of granular material
Field of the Invention
[0001] The present invention relates to a sieving instrument and a sieving method for detecting the reliability of particle size distribution characteristics of granular material, in particular to a sieving instrument capable of intelligently tracking and analysing the granularity and the reliability of particle size distribution characteristics of the granular sample.
Background of the Invention
[0002] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
[0003] Granular materials are widely found in nature, daily life, and in the fields of production and technology, e.g., sand and soil in nature, grains, sugar, salt and drugs in daily life, and various building materials such as ore, coal, lime and fly ash in the fields of production and technology are all granular materials.
[0004] The bulk phase properties of the granular materials mainly include size, shape and surface area of granules, as well as magnetic, electrical and optical properties of granules, etc. The sizes of granules are an important basis for classifying granular materials, and also have a significant impact on various physical and chemical characteristics and chemical reaction characteristics of the granular materials. For granular material, its granularity and particle size distribution characteristics largely determine the nature and efficiency of the granule processing technology, and are the basis for selecting and evaluating the preparation method or technology and for controlling the process. Taking various soil granular materials in civil engineering as an example, the particle size distribution characteristics of granular are the main indexes for classifying various soils such as sand, gravel and block stone, and determine the physical mechanics and engineering properties of the soils. In construction activities of buildings, railways, large earth-rock dams, airports and the like, the particle size distribution characteristics of the soil on site should be made clear, and then the soil is classified according to the particle size distribution characteristics and other relevant indexes to further study the mechanical and engineering properties of the soil, such as strength, deformation and bearing capacity. Therefore, in face of a large number of granular material with wide-range and irregular size distribution, how to accurately, quickly and efficiently obtain the granularity and particle size distribution characteristics of overall granular material becomes an important issue and a technical problem to each scientific research and engineering technical person.
[0005] At present, the conventional method for determining the granularity and particle size distribution characteristics of granular material is to randomly extract samples of a number of masses from overall granular material, obtain the granularity and particle size distribution characteristics of the sample through a sieving test, and further utilize the granularity and particle size distribution characteristics of a granular sample to represent the particle size distribution characteristics of the overall granular material by an averaging method. In this process, it is necessary to ensure that the selected granular samples are thoroughly representative. Therefore, the sampling amount, sampling method and the like of the samples have an important influence on the reliability of the test results. For example, when the number of overall granular material is large and the size distribution is wide, if the sampling amount is insufficient, the granularity and the particle size distribution characteristics determined after the sieving test cannot represent the particle size distribution characteristic of the overall granular material; when the sampling amount is excessive, it means that the engineering quantity is gradually increasing, which not only causes excessive materials in the sieve box to reduce the sieving efficiency, but also causes a lot of waste of manpower and material resources in the sieving test; Meanwhile, related researches also show that when the number of sample reaches a certain limit, it produces little effect on improving the accuracy of test results by continuing increasing the number of sample.
[0006] Finally, the national regulations and the industry norms have not yet clearly stated and relevant scientific researches have rarely reported how many samples should be taken for the sieving test to objectively and accurately reflect the particle size distribution characteristics of the overall granular material.
Summary of the Invention
[0007] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
[0008] The present invention in at least one embodiment is intended to provide a sieving instrument and a sieving method for detecting the reliability of particle size distribution characteristics of granular material. The sieving instrument is quick and convenient to use, and high in accuracy. Particularly in face of wide size distribution range, high gradation complexity and huge number of the overall granular material often involved in the professional fields, such as chemical industry, mining, civil engineering and pharmaceuticals, the intelligent sieving instrument and sieving method in the present application have wide application prospect and important innovative significance.
[0009] In one aspect, the technical solution adopted by the present invention is:
[0010] a sieving instrument for detecting the reliability of particle size distribution characteristics of granular material, comprises a base plate, an elastic vibration module, an upright column, a frame beam, a vibration table, and a sieve box. The elastic vibration module, the upright column and the frame beam are mounted on the base plate, the vibration table is mounted on the elastic vibration module, the sieve box is arranged on the vibration table;
[0011] a feeding box is fixedly mounted at the upper part of the frame beam, and an outlet of the feeding box extends into the sieve box; a carrying platform is mounted on the upright column, a plurality of storage boxes are arranged on the carrying platform;
[0012] the sieve box is divided into a plurality of grids from bottom to top by a plurality of sieve pore plates arranged horizontally, the sieve pore diameter of the upper layer of sieve pore plate is greater than that of the lower layer of sieve pore plate, and the storage box is correspondingly arranged at the discharge port of each grid, and the discharge port of each grid is aligned with the feeding port of the corresponding storage box;
[0013] the vibration table tilts on one side, the feeding box is located on the higher side of the vibration table, and the storage boxes are located on the lower side of the vibration table.
[0014] According to the embodiments of the present invention, the present invention may be further optimised. The following shows technical solutions after optimisation:
[0015] Preferably, the elastic vibration module comprises a plurality of piers arranged on the base plate, compression springs mounted between the tops of the piers and the vibration table, and a vibration motor mounted on the vibration table;
[0016] preferably, the vibration motor is a centrifugal vibration motor;
[0017] preferably, rubber spacers are arranged between the compression springs and the vibration table, and between the compression springs and the piers.
[0018] In order to facilitate the control of the vibration frequency and the vibration amplitude, the vibration motor is electrically connected with a frequency converter.
[0019] Preferably, two adjacent grids of each sieve box are fixed together and locked by a fixing lock, and the bottom grid is fixed on the vibration table by a fastening clamp; preferably, the side wall of each grid is provided with an observation window; preferably, a dust cover is mounted at the top of the sieve box.
[0020] Preferably, the tilt angle of the vibration table is 0°-5° relative to the horizontal plane.
[0021] Further, the present invention further comprises a computer, a programmable logic controller, an operation controller and a data acquisition instrument; weighing sensors are arranged between the carrying platform and the storage boxes; the computer communicates with the operation controller, the operation controller communicates with the programmable logic controller, the programmable logic controller is electrically connected with the data acquisition instrument, and the data acquisition instrument is electrically connected with the weighing sensor.
[0022] In order to facilitate the adjustment of the height of the frame beam and/or the upright column, preferably, the frame beam is a height adjustable scalable beam, and/or the upright column is a height adjustable scalable column.
[0023] Based on the same inventive concept, in another aspect the present invention also provides a method for sieving granular material by using a sieving instrument for detecting the reliability of particle size distribution characteristics of granular material, wherein the sieving instrument for detecting the reliability of particle size distribution characteristics of granular material, comprises a base plate, an elastic vibration module, an upright column, a frame beam, a vibration table, and a sieve box; the elastic vibration module, the upright column and the frame beam are mounted on the base plate, the vibration table is mounted on the elastic vibration module, the sieve box is arranged on the vibration table; a feeding box is fixedly mounted at the upper part of the frame beam, and an outlet of the feeding box extends into the sieve box; and a carrying platform is mounted on the upright column, a plurality of storage boxes are arranged on the carrying platform. The sieve box is divided into a plurality of grids from bottom to top by a plurality of sieve pore plates arranged horizontally, a sieve pore diameter of the upper layer of sieve pore plate is greater than that of the lower layer of sieve pore plate, and the storage box is correspondingly arranged at a discharge port of each grid, and the discharge port of each grid is aligned with a feeding port of the corresponding storage box. The vibration table tilts to one side, the feeding box is located on the higher side of the vibration table, and the storage boxes are located on the lower side of the vibration table. The method comprises the following steps:
[0024] S1, determining the average density of the overall granular material to be measured, and fixing the sieve box on the vibration table;
[0025] S2, weighing a granular sample and putting the same into the feeding box, and starting the elastic vibration module, so that the granular sample flows into the sieve box under the action of self-weight and moves towards the discharge ports until flowing into the storage box; and
[0026] S3, after all the granular sample flows into the corresponding storage box, stopping the elastic vibration module, and weighing the granular sample collected in the storage boxes.
[0027] Further, this aspect of the present invention further comprises step S4: inputting signals about the densities of granule sample and the mass and sieve pore diameter of each layer of granules acquired in step S3 from an input port of the programmable logic controller,
and calculating the number ' of granules in each storage box, a median granule diameter
A and particle size distribution characteristics PSDI of granular sample; and
[0028] calculating, by the programmable logic controller, the median granule diameter 1
obtained by the current sieving test, comparing the median granule diameter 1 with 1 -1 (D. +D ) , wherein if A1 ; -(D. +D. it indicates that the mass of granular 2 2 sample meets the accuracy requirement, that is, the particle size distribution characteristics of granular sample obtained by the current test can represent the particle size distribution of - 1 the overall granular material, and if D, > -(De +D.), it indicates that the mass of 2 granular sample is insufficient, and the particle size distribution characteristics of granular sample obtained by the sieving test cannot represent the particle size distribution of the overall granular material, and the median granule diameter A exceed a set accuracy range.
[0029] The mass of the granular sample to be weighed in the current sieving test is preferably determined by the last sieving test, and steps S1-S4 are repeated, and the current sieving test ends until the median granule diameter of the granular sample of the (k+1)th
sieving test satisfies that Dk+1 - k is within the range of -0.5 to 0.5mm after the operation of the programmable logic controller, that is, if the calculated mass of granular sample of the next sieving test begins to be smaller than the mass of the granular sample of the current sieving test or the calculated mass of granular sample of the next sieving test begins to be convergent to the mass of the granular sample of the current sieving test, the particle size distribution characteristics of the granular sample obtained by the current sieving test can represent the particle size distribution characteristics of overall granular material, and the
error meets the requirement and the test is ended, wherein Dk denotes the median granule
diameter of the kth granular sample, Dk+1 denotes the median granule diameter of the (k+1)th
granular sample, k denotes the kthsieving test, andDk+1 -Dk denotes the difference between the median granule diameters of the granular sample obtained by the kth sieving test and the median granule diameter of the granular sample obtained by the (k+1)th sieving test.
[0030] In the present invention, specific definition can be made according to the characteristics of granular sample in actual sieving, the range of -0.5 to 0.5mm is taken as an example here, and generally speaking, a smaller defined value means a more accurate test result and more frequent circulation of the test.
[0031] The logic analysis steps and design ideas of the sieving instrument for detecting the reliability of particle size distribution characteristics of granular material according to the present invention are as follows:
1. Determination of the number of sample
[0032] From the perspective of probability, if a certain amount of granular sample is selected from overall granular material, the probability that each granule in the overall granular material is selected is equal, which is actually a simple random sampling process. If the number of overall granular material is M (approaching to infinity), in order to obtain the particle size distribution characteristics of the overall granular material, the granular sample to be tested can be divided into two classes according to whether they are within a specified granule group interval. Each tested granule is defined as follows:
1, ith granule belongs to the specified granule group(i=1,2,...,M) '0, ith granule does not belong to the specified granule group(i=1,2,...,M)
[0033] In the formula, 1 is the assignment of the lh granule in the overall granular
material; if the diameter of theih granule belongs to the specified granule group, the assignment is 1; otherwise, the assignment is 0. Grouping by the size of particle is called granule group, that is, the range of variation of a certain level of granule size.
[0034] Based on the above assignment definition of granules, in the overall granular material, if the granular has M, granules having the diameters of thefhgranulegroup=1,
2,3... A; A is the number of granule group), the number percentage of granules of thefh granule group is:
M1 1M" =- =F (2) M M j1
[0035] In the formula, P is the percentage of granules of the fh granule group in the
overall granular material, and F is an average of the cumulative number of granules of the jh granule group in the overall granular material.
[0036] Then, in the sieving test of the granular material, for a sample having m,, granules
to be tested, if the number of granules of the h granule group (=1, 2, 3...A; A is the number of granule group) is m1 , the number percentage of granules of the specified hgranulegroup
in the granular sample is:
m 1 M'11 P. - - il f (3)
[0037] In the formula, pj is the percentage of granules of the fh granule group in the
granular sample, and is an average of the cumulative number of granules of the h
granule group in the granular sample.
[0038] Randomly taking a certain number of granules from the overall granular material for the sieving test is a simple random sampling method in mathematics. Therefore, the percentage pj of granules of the fh granule group obtained from the sample is an unbiased
estimate of the percentage P of granules of thefh granule group in the overall granular
material. After mathematical calculation, a variance can be obtained:
1 M-m #(p )f f) m M'S 2 (4)
[0039] In the formula, (p ) and (f) are both statistical variances of thefhgranule
group in the granular sample, and S 2 is a variance of the granule diameter distribution of the overall granular material and is calculated as follows:
S2= M - P ) (5) M-1
[0040] It can be known in combination with the mathematical knowledge of probability statistics that in simple random sampling, the error between the parameter estimation value p obtained from the sample and the overall actual value P can be controlled within a specified limit, and is quantitatively determined by two indexes including confidence coefficient 1-a and absolute error limit d
P1f -F < d =1-a (6)
[0041] Further, it can be known according to the definition of a bilaterally quantile u in
probability statistics that:
2 1],(7)
[0042] In the formula, (f) is a statistical variance of the fh granule group in the granular
sample.
[0043] Further, it can be obtained in combination with formula (4), formula (6) and formula (7) that:
u2 1- 1S2
m- (8) -+d2 _ M M
[0044] It can be seen from formula (8), the number of granules in the hgranulegroupin
the sample depends on three indexes: the number M of the overall granular material, accuracy control indexes (confidence coefficient 1-a and absolute error limit d ), and variance S2 of the size distribution of the overall granular material. That is, if the number M of the overall granular material is larger, the accuracy required for the sieving results is higher, the granule diameter distribution of the overall granular material is wider, and more granular samples are required for the sieving test. In engineering practice activities, the number M of the overall granular material approaches to infinity. Thus, formula (8) can be further simplified in combination with formula (5):
upP,(1-P,) mi d2 (9)
[0045] So far, the number of samples required for the hgranulegroupisdetermined.
Further, in order to determine the particle size distribution range of A granule groups in the sieving test, the total number mal of required granular sample is calculated as follows:
mail = mi+m 2+m 3 +--- +m2 = - P ( P =2 1 +P (10)
[0046] Because 0 ! P. 1, it can be known from the basic inequality that:
A- 1 2+P P+ P+...±A =1 (1
[0047] Thus, an extreme value of the total number of granular sample for the sieving test in formula (10) is obtained as follows:
2 U
d2 (12)
[0048] It is known from experience that under certain conditions, if more granular samples participate n e in st, the test results are closer to the true particle size distribution characteristics of the overall granular material. Therefore, the conservative value m, can be
the maximum value determined in formula (12), i.e.
dau= (13)
[0049] It can be seen from formula (13) that the number of granular samples selected for a sieving test can be jointly determined by the accuracy control inesndthseving test, including the confidence coefficient -a and absolute error limit d . For example, in a sieving test, if the confidence coefficient 1-a of the initial design test result is 95%, that is,
the absolute error limit d is 7.07% (or d2 is 0.005), the minimum number of granular samples required for calculation is 768, that is, as long as 768 granules are randomly taken out from the overall granular material as granular sample in a sieving test, it is possible to ensure that the error between the granule diameter and the particle size distribution characteristics of the granular sample obtained after the sieving test and those of the overall granular material is controlled within ±7.07%.
IIl. Determination of the mass of sample
[0050] Further, the number of granular sample is often not used as a control index during the sieving test, but the mass of granular sample is used as a control standard, so that before the sieving test, the average density p of the granular material is obtained by a density test, and the required mass of granular sample is calculated as follows:
1 -3 CO = m'1p -rcD (14) 6
[0051] In the formula, co is the mass of granular sample, D is the median granule
diameter of the granular sample, and the median granule diameter D is defined as the mass equivalent diameter of the overall granular sample according to A granule groups and the number mi of granules in each granule group interval designed for the sieving test and
calculated as follows:
m cp (Dj I D (15) 61
[0052] In the formula, D is the median granule diameter of thefh granule group, i.e., the
average of the upper and lower limit diameters of thefh granule group; and P is the average density of the granular material.
[0053] In engineering practice, there are only three relationships between the median
granule diameter D of the particle size distribution characteristics curve of the granular
material and I(Din+L) (D, is the maximum granule diameter of the granular 2 sample; D. is the minimum granule diameter of the granular sample). The three
relationships are discussed below to determine the mass of granular sample required for the sieving test.
[0054] When D= (D +D),the mass of sample required to analyse the particle size 2 distribution characteristics can be obtained in combination with formula (14) for calculating the sample mass: co-mrp- "" ±D (16) aiiP6 y 2 (16)
[0055] At the same time, if the maximum granule diameter D of granular materials is
much greater than the minimum granule diameter D. , the influence of the minimum
granule diameter D . in formula (16) is basically negligible, and formula (16) for calculating
the mass of sample can be further simplified as:
CO = m'1p -7r n (17) 6 (2
-1
[0056] When D< -(D +D.), it indicates that most of the granular material are fine 2 granules and few of the granular material are coarse granules, and the median granule diameter of the overall granular material is small. However, in the same case, it can be seen from formula (14) that if the median granule diameter of the overall granular material is larger, the required mass of sample is larger, and the sieving results of the granular sample are closer to the particle size distribution characteristics of the overall granular material, indicating that in this case, the mass of granular sample calculated according to formula (14) is conservative, and it can be ensured that the error between the particle size distribution characteristics of granular sample after sieving and the particle size distribution characteristics of the overall granular material is controlled within the accuracy range.
- 1 D > -(Dn +DA.)
[0057] When 2 , it indicates that few of the granular material are fine granules and most of the granular material are coarse granules, and the median granule diameter of the overall granular material is large. If the sample mass required for the test is still directly determined using formula (14), a large test error may be caused. Thus, for this case, a loop iteration method can be used to determine the required granular sample mass to ensure the reliability of the sieving test results. This method is to first measure a sample of certain mass and perform the first sieving test to obtain the particle size distribution characteristics PSDI of the granular sample. It is assumed that the particle size distribution
characteristics PSDI does not meet the reliability requirement at this time, the median
granule diameter D of the sample can be calculated from the particle size distribution characteristics PSDI in combination with formula (15), then 1 is substituted into formula
(14) to obtain the mass of a granular sample to be weighed for the second sieving test,
PSD 2 and D2 for the second sieving test are further obtained, and so on, until the median
granule diameter of the granular sample of the (k+1)th sieving testsatisfies thatDk.1-- k is
within the range of -0.5 to 0.5mm after the operation of the programmable logic controller, that is, when the calculated mass of granular sample of the next sieving test begins to be smaller than the mass of the granular sample of the current sieving test or the mass of granular sample of the next sieving test begins to be convergent to the mass of the granular sample of the current sieving test, indicating that the particle size distribution characteristics of the granular sample obtained by the current sieving test can represent the particle size distribution characteristics of the overall granular material, and the error meets the
requirement and the test is ended, wherein Dk denotes the median granule diameter of the
kth granular sample, Dk+I denotes the median granule diameter of the (k+1)thgranular
sample, k denotes the kth sieving test, andDk+1- Dk denotes the difference between the median granule diameter of the granular sample obtained by the kth sieving test and the median granule diameter of the granular sample obtained by the (k+1)th sieving test, and the
range ofDk+- Dk can be defined according to the feature of the granule, the range of -0.5 to 0.5mm is taken as an example here, and generally speaking, a smaller defined value means a more accurate test result and more frequent circulation of the test.
[0058] Compared with the prior art, the present invention has the following advantages:
[0059] 1. The sieving test of a plurality of granular materials can be carried out by using the instrument of the present invention to obtain the granularity and particle size distribution characteristics of granular material, which lays a foundation for further classifying the granular materials and studying related physical, mechanical and chemical properties. The vibratory sieving system of the invention patent adopts tilting rectangular sieve box, the granular sample to be tested is loaded from the higher side of the top grid of the sieve box, and the granules can freely jump and be sieved along the longest path of the sieve box, so that the sieving efficiency is improved. At the same time, the rectangular sieve box is provided with observation windows, which is beneficial to directly observing the sieving situation of granules in each layer of grid.
[0060] 2. The vibration energy of the vibratory sieving system of the present invention is continuously controllable. According to the flow and runout of the granules in each layer of grid, the intensity, frequency and amplitude of the vibration force of the vibration motor can be flexibly adjusted by the frequency converter, so that the sieving test is completed accurately, quickly and efficiently, and the optimal sieving efficiency is achieved.
[0061] 3. The vibratory sieving system of the present invention is efficiently combined with the full-automatic collection system to realise rapid recovery of the granular material in the sieve box, and the granule mass in each group interval is measured by the weighing sensor at the lower part of each storage box.
[0062] 4. Based on the random sampling reliability theory in probability statistics, the present invention generally meets the design requirements for intelligent tracking and analysis of the reliability of particle size distribution characteristics of a granular sample. A mathematical model established based on the reliability theory for determining the number and mass of granular sample and judging the magnitude of the error between the granular sample particle size distribution characteristics and the overall granular material particle size distribution characteristics is programmatically stored in the programmable logic controller, and the hardware facilities such as sensors, collectors, a computer and a programmable logic controller are further combined into the "nerve center" of the intelligent sieving instrument, thereby quantitatively tracking and analysing the sieving results of the granular sample, and finally obtaining the optimal sampling mass and the particle size distribution characteristics meeting the control accuracy requirements.
[0063] Based on the reliability theory of sampling analysis, it is found by researches that the total content of the granular material, the granularity distribution range and the accuracy control index are three important influencing factors that determine the granular sample size selected for the sieving test, and a sieving instrument capable of intelligently tracking and analysing the diameter and distribution characteristics of the granular sample is further designed based on the reliability theory. The specified accuracy index is input to the control interface of the computer before the test to obtain the optimal sample size required for meeting the control accuracy requirements for the granularity and particle size distribution characteristics of the overall granular material. Therefore, the intelligent sieving instrument not only accurately, quickly and efficiently acquires the particle size distribution characteristics of the granular material, but also highlights the green, energy-saving and environment-friendly design concept, and its design theory has an important significance of methodology for guiding the development of relevant scientific research and engineering practice.
[0064] In addition, the intelligent sieving instrument of the present invention has the advantages of simple structure, convenient installation and flexible test operation, conforms to the green, energy-saving and environment-friendly design concept, and meets the requirements of sieving tests for a plurality of different granular materials.
[0065] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".
Brief Description of the Drawings
[0066] Fig. 1 is a structure diagram of an intelligent sieving instrument according to an embodiment of the present invention;
[0067] Fig. 2 is a flow diagram of a program for tracking and analysing granular sample test results by the sieving instrument according to the present invention;
[0068] Fig. 3 shows three typical particle size distribution characteristic curves of the granular material.
[0069] In which:
[0070] 1-base plate, 2-frame beam, 3-vibration table, 4-rigid pier, 5-compression spring, 6 centrifugal vibration motor, 7-frequency inverter, 8-acceleration sensor, 9-telescopic upright column, 10-feeding box, 11-steel hoop, 12-horizontal blocking partition plate, 13-dust cover, 14-rectangular sieve box, 15-fixing lock, 16-sieve pore plate, 17-discharge vertical partition plate, 18-discharge pipe and tip thereof, 19-storage box, 20-storage box outlet, 21-weighing sensor, 22-carrying platform, 23-data acquisition instrument, 24-programmable logic controller, 25-operation controller, 26-computer, 27-fastening clamp, 28-observation window, 29-rubber spacer.
Detailed Description of the Embodiments
[0071] A sieving instrument for intelligently detecting the reliability of particle size distribution characteristics of granular material, as shown in Fig. 1, includes hardware facilities such as a vibratory sieving system, a full-automatic collection system, a data acquisition module, a programmable logic controller and a computer 26.
[0072] In the present embodiment, the vibratory sieving system includes a support frame structure, an elastic vibration module, rectangular sieve box 14, feeding and discharge devices, etc. The support frame structure includes a base plate 1, a telescopic frame beam 2, Foma wheels, etc. The base plate 1 is made of steel, and its processing thickness should be strictly controlled. Because the equipment needs to undergo long-term dynamic load during use, the base plate 1 should have sufficient rigidity, strength, stability and durability. The Foma wheels are mounted at four corners of the bottom surface of the base plate 1 to realise flexible movement of the vibratory sieving system. The elastic vibration module is mounted at the upper part of the base plate 1.
[0073] In the present embodiment, the elastic vibration module mainly includes a tilting vibration table 3, compression springs 5, a vibration motor 6 and other components. The tilting vibration table 3 is designed to tilt on one side, generally tilt about 0°-5°, and its main function is to realise runout of the granular material while they are sieved in the rectangular sieve box 14 along the long edge during the sieving test, ensure the maximum sieving path of granules, facilitate automatic collection of the granular material in each layer of grid of the sieve box 14, and reduce the granule loss in the sieving process. At the same time, a fastening clamp 27 for fixing the bottom grid of the rectangular sieve box 14 is mounted at the upper part of the tilting vibration table 3, and functions to prevent structurally natural vibration of the sieve box 14 in the vibratory sieving process, and to transfer the vibration energy upward to each layer of grid of the rectangular sieve box 14 in maximal degree..
[0074] In the present embodiment, the loading source of the elastic vibration module is a centrifugal vibration motor 6, which is fixed in the center of the bottom surface of the tilting vibration table 3 to furthest reduce the horizontal vibration force component generated in the loading process of the vibration motor 6 by means of the structural self-weight of the elastic vibration module, and a balance weight is fixed on the bottom surface of the tilting vibration table 3 if necessary. Further, a frequency inverter 7 is mounted between the centrifugal vibration motor 6 and an input power source to change the vibration intensity by adjusting the input frequency of the vibration motor 6. At the same time, an acceleration sensor 8 is mounted at a suitable position on the bottom surface of the tilting vibration table 3 near the vibration motor 6, and an output port of the acceleration sensor 8 is connected with the hardware facilities such as a data acquisition instrument 23 and the computer 26 to monitor the output vibration intensity of the vibration motor 6 during the sieving test in real time.
[0075] Further, the tilting vibration table 3 is fixed to the top of four groups of compression springs 5, totally eight compression springs 5. In the present invention, the eight compression springs 5 are fixed to the tops of the four rigid piers 4, and rubber spacers having the thickness of about 10-20 mm are mounted between the compression springs 5 and the tilting vibration table 3 and between the compression springs 5 and the rigid piers 4 to reduce noise. Further, the eight compression springs 5 of the same ex-factory batch and the same specification should be used to ensure the consistency of basic indexes such as size and rigidity coefficient to the greatest extent, which is beneficial to maintaining the overall stability and coordination of the upper vibration system during the test.
[0076] In the present embodiment, the telescopic frame beam 2 is fixed to one side of the base plate 1, and is at a suitable distance from the vibration module. A feeding box 10 is fixed to the upper part of the frame beam 2 by steel hoops 11, and the height of the frame beam 2 is flexibly adjusted to a suitable height according to the number of grid of the sieve box 14 required for the test of the granular material to facilitate the loading of samples of the granular material to be sieved from a feed port. Horizontal blocking partition plates 12 are mounted at the lower part of the funnel-shaped structure of the feeding box 10 to flexibly adjust the amount of granules entering the sieve box 14, thereby preventing excessive granular sample from flowing into the top grid of the sieve box 14 at one time, and preventing reduction of the accuracy and quality of the sieving test resulted from excessive granules in each layer of gird of the sieve box 14.
[0077] Fixing locks 15 are mounted at appropriate positions on the rectangular sieve box 14 along the long edges to tightly fix every two grids in the vertical direction during the sieving test, thereby preventing the granular sample from escaping from the joint of the upper and lower grid of the sieve box 14, and ensuring the sieving efficiency. In the present embodiment, rectangular observation windows 28 for observing the flow of granules in the sieve box 14 in the sieving process are made at appropriate positions of the long edges of the rectangular sieve box 14, and the rectangular observation windows 28 are sealed with transparent organic glass from the inner side. Further, a dust cover 13 is mounted at the upper part of the top grid of the rectangular sieve box 14 (i.e., with the largest sieve pore diameter), and the four sides of the dust cover are tightly sealed. At the same time, each rectangular sieve box 14 with a discharge pipe machined on the side edge should be uniformly placed on the lower side of the tilting vibration table 3, and a discharge vertical partition plate 17 is simultaneously designed at the root of the discharge pipe to prevent the granular material in the sieve box 14 from flowing out of the discharge pipe too early in the sieving process to affect the set sieving time and reduce the sieving accuracy.
[0078] In the present embodiment, the automatic collection system is innovatively used to track and collect the granule mass timely within the range of each granule group. The full automatic collection system consists of storage box 19, weighing sensors 21, a telescopic upright column 9, etc. According to the number of grids of the rectangular sieve box 14 used, the tip of the discharge pipe of each grid is aligned with the feeding port of the storage box 19, and the discharge vertical partition plates are opened to automatically collect granular sample in the sieve box 14. A weighing sensor 21 is horizontally mounted at the lower part of each storage box, the weighing sensor 21 is further fixed on a carrying platform 22, and each carrying platform 22 is horizontally fixed to the telescopic upright column 9 by steel hoops, thereby flexibly adjusting the relative positions of the tip of the discharge pipe of the sieve box 14 and the feed port of the storage box 19, and collecting all the residual granular material in each layer of grid of the sieve box 14 to the greatest extent. The weighing sensor 21 automatically acquire the granule mass in different granule groups, and the granule mass is input into the programmable logic controller 24 through the data acquisition instrument 23, thereby further intelligently tracking, analysing and judging the reliability between the particle size distribution characteristics of the granular sample and the particle size distribution characteristics of the overall granular material.
[0079] The above content is the theoretical basis for the development of a sieving instrument for intelligently analysing the reliability of particle size distribution characteristics of the granular sample. The sieving instrument has the advantages of high degree of automation, wide application range and the like, and can be used for intelligent sieving tests on granular materials such as gravels, soil, grains, sugar, salt, drugs, ore, coal, lime, fly ash and the like of various particle size distribution characteristics.
[0080] The following further illustrates how to implement a method for intelligently tracking and analysing the reliability of particle size distribution characteristics of granular sample in face of an unknown granular material, in combination with the features and using method of the instrument. As shown in Fig. 2, the specific steps are as follows:
[0081] 1) First, the average density of the overall granular material to be measured is determined. The density of the material is obtained by the density test, inputted and determined on the control interface of the computer 26, and control accuracy index values of the sieving test are inputted to the control interface of the computer 26, i.e., the values of confidence coefficient 1-a and absolute error limit d inthe theory of intelligently analysing the sample mass are determined and calculated.
[0082] 2) A plurality of rectangular grids of the sieve box 14 having appropriate sieve pore diameters are selected according to the needs of the sieving test, and the sieve pore diameter values are inputted and determined on the analysis interface of the computer 26. At the same time, the grids of the sieve box 14 are neatly placed on the vibratory sieving system in an ascending order of the sieve pore diameters from bottom to top, the side wall of the bottom sieve box 14 is locked by the fastening clamp 27 on the surface of the tilting vibration table 3, every two grids of the sieve box 14 are sequentially fixed by the fixing locks on the side walls, the top grid of the rectangular sieve box 14 is sealed with the dust cover, and the relative positions of the feed ports of each layer of the storage box and the tips of the discharge pipes of the sieve box 14 are adjusted respectively to ensure that the sieved granules can smoothly enter the storage box from the discharge pipes.
[0083] 3) The diameter of larger granules in the overall granular material is measured by a simple method such as visual inspection or scale measurement. Then, half of the larger granule diameter is inputted into the control interface of the computer 26 as an initial average
granule diameter Do of the first sampling reference. At this time, the mass of a granular sample weighed for the first sieving test is obtained by programming calculation based on formula (14). In addition, the size of the granular sample should roughly conform to the diameter distribution range of the overall granular material as much as possible during weighing. Then, granular sample is placed in the feeding box 10, the vibration motor 6 is started after inspection, and the feeding partition plate is opened such that the material flows into the top grid of the sieve box 14 under the action of self-weight.
[0084] 4) In the sieving process, the flow pattern of granules in each layer of grid of the sieve box 14 is observed through the observation window 28 on the side wall of the rectangular sieve box 14. In order to achieve the best sieving effect, the frequency converter 7 of the vibration motor 6 can be adjusted to change the vibration intensity, frequency and amplitude of the vibratory sieving system, so that the granules can stably and slowly flow to the side of the discharge pipe in each layer of grid of the sieve box 14; and the vertical partition plates of the discharge ports are opened, so that the granules pass through the discharge pipes and are automatically collected by the storage box.
[0085] 5) After all the granules in each layer of grid of the sieve box 14 flow into each layer of storage box, the vibration motor 6 is turned off. At this time, the mass of granular sample in each storage box is acquired by the weighing sensor 21. Signals about the density, the mass of each layer of granules and the sieve pore diameter are further input from the input port of the programmable logic controller. The number mi of granules in each
granule group interval, the median granule diameter 1 of the granular sample, and the particle size distribution characteristics PSDI are obtained by calculation of the above
intelligent sieving program and displayed on the control interface of the computer 26.
[0086] 6) Based on the intelligent sieving test analysis method for determining the mass of
granular sample, the median granule diameter 1 obtained by the current sieving test is
calculated by an algorithm designed by the programmable logic controller, and comparing 1
1 with-(Da+D ). If the influence of the minimum granule diameter Dm is negligible 2
relative to the maximum granule diameter D_ , the median granule diameter 1 can also
be compared with (Dax) when the algorithm is written. When the median granule 2 1 diameter 1 of the current test sample is smaller than or equal to +D.)by 2 calculation, it indicates that the mass of the granular sample weighed in the current sieving test meets the accuracy requirement, that is, the particle size distribution characteristics obtained at this time can represent the particle size distribution of the overall granular - 1 material; when D, > -(D. +D.), it indicates that the mass of granular sample in the 2 current sieving test is insufficient, and the particle size distribution characteristics of the granular sample obtained by the current sieving test cannot represent the particle size distribution of the overall granular material, and exceeded the set accuracy range. Next, the
program of the computer 26 substitutes the median granule diameter 1 obtained by the current sieving test into the program language written based on formula (14) and then calculates the mass of a sample to be weighed for next sieving test, at the same time, the material in the storage box is recovered, and each layer of grid of the rectangular sieve box 14 is cleaned for next sieving test.
[0087] 7) Steps 2) - 6) are repeated according to the mass of the current sample determined by the last sieving test, and the test ends until the median granule diameter of the granular sample of the (k+1)th sieving test satisfies that D.1-- D is within the range of 0.5 to 0.5mm after the operation of the programmable logic controller, that is, when the calculated mass of granular sample of the next sieving test begins to be smaller than the mass of the granular sample of the current sieving test or the mass of granular sample of the next sieving test begins to be convergent to the mass of the granular sample of the current sieving test, indicating that the particle size distribution characteristics of the granular sample obtained by the current sieving test can represent the particle size distribution characteristics of the overall granular material, and the error meets the requirement and the test is ended, wherein Dk denotes the median granule diameter of the kth granularsample, DIi denotes the median granule diameter of the (k+1)th granular sample, k denotes the kth sieving test, and Dk+- Dk denotes the difference between the median granule diameters of the granular sample obtained by the kth sieving test and the median granule diameter of the granular sample obtained by the (k+1)th sieving test, and the range ofDk+1- D can be defined according to the feature of the granule, the range of -0.5 to 0.5mm is taken as an example here, and generally speaking, a smaller defined value means a more accurate test result and more frequent circulation of the test.
Claims (12)
1. A method for sieving granular material by using a sieving instrument for detecting the reliability of particle size distribution characteristics of granular material, wherein the sieving instrument for detecting the reliability of particle size distribution characteristics of granular material, comprises a base plate, an elastic vibration module, an upright column, a frame beam, a vibration table, and a sieve box; the elastic vibration module, the upright column and the frame beam are mounted on the base plate, the vibration table is mounted on the elastic vibration module, the sieve box is arranged on the vibration table; a feeding box is fixedly mounted at the upper part of the frame beam, and an outlet of the feeding box extends into the sieve box; a carrying platform is mounted on the upright column, a plurality of storage boxes are arranged on the carrying platform; the sieve box is divided into a plurality of grids from bottom to top by a plurality of sieve pore plates arranged horizontally, a sieve pore diameter of the upper layer of sieve pore plate is greater than that of the lower layer of sieve pore plate, and the storage box is correspondingly arranged at a discharge port of each grid, and the discharge port of each grid is aligned with a feeding port of the corresponding storage box; the vibration table tilts to one side, the feeding box is located on the higher side of the vibration table, and the storage boxes are located on the lower side of the vibration table; the method for sieving granular material comprises the following steps: S1, determining the average density of the overall granular material to be measured, and fixing the sieve box on the vibration table; S2, weighing a granular sample and putting the same into the feeding box, and starting the elastic vibration module, so that the granular sample flows into the sieve box under the action of self-weight and moves towards the discharge ports until flowing into the storage boxes; S3, after all the granular sample flows into the corresponding storage boxes, stopping the elastic vibration module, and weighing the granular sample collected in the storage boxes; and S4, inputting signals about the densities of granular sample and the mass and sieve pore diameter of each layer of granules acquired in step S3 from an input port of the programmable logic controller, and calculating the number mjof granules in each granule
group interval, a median granule diameter D and particle size distribution characteristics PSDI of the granular sample; and calculating, by the programmable logic controller, the median granule diameter 1 obtained by a current sieving test, comparing the median granule diameter 1 with 1 -1 (Dmi +D) wherein if Di:<; -(Dmi +D_) , it indicates that the mass of the weighed 2 2 granular sample meets the accuracy requirement, that is, the particle size distribution characteristics of granular sample obtained by the current sieving test can represent the - 1 particle size distribution of the overall granular material, and if DI > -(Dmin +Dm), it 2 indicates that the mass of the weighed granular sample is insufficient, and the particle size distribution characteristics of granular sample obtained by the current sieving test cannot represent the particle size distribution of the overall granular material, and the median granule diameter 1 exceeds a set accuracy range.
2. The method for sieving granular material according to claim 1, wherein the elastic vibration module comprises a plurality of piers arranged on the base plate, compression springs mounted between the tops of the piers and the vibration table, and a vibration motor mounted on the vibration table.
3. The method for sieving granular material according to claim 2, wherein the vibration motor is a centrifugal vibration motor.
4. The method for sieving granular material according to claim 2 or 3, wherein rubber spacers are arranged between the compression springs and the vibration table, and between the compression springs and the piers.
5. The method for sieving granular material according to any one of claims 2 to 4, wherein the vibration motor is electrically connected with a frequency converter.
6. The method for sieving granular material according to any one of claims 1 to 5, wherein two adjacent grids of sieve box are fixed together and locked by a fixing lock, and the bottom grid is fixed on the vibration table by a fastening clamp.
7. The method for sieving granular material according to claim 6, wherein the side wall of each grid is provided with an observation window.
8. The method for sieving granular material according to claim 6 or 7, wherein a dust cover is mounted at the top of the sieve box.
9. The method for sieving granular material according to any one of the preceding claims, wherein the tilt angle of the vibration table is 0°-5° relative to the horizontal plane.
10. The method for sieving granular material according to any one of claims 1-9, wherein the sieving instrument further comprises a computer, a programmable logic controller, an operation controller and a data acquisition instrument; weighing sensors are arranged between the carrying platform and the storage boxes; the computer communicates with the operation controller, the operation controller communicates with the programmable logic controller, the programmable logic controller is electrically connected with the data acquisition instrument, and the data acquisition instrument is electrically connected with the weighing sensors.
11. The method for sieving granular material according to any one of claims 1-10, wherein the frame beam is a height adjustable telescopic beam, and/or the upright column is a height adjustable telescopic column.
12. The method for sieving granular material according to any one of claims 1 to 11, wherein the mass of the granular sample to be weighed in the current sieving test is determined by a last sieving test, and steps S1-S4 are repeated, and the current sieving test ends until the median granule diameter of the granular sample of a (k+1)th sieving test
satisfies thatDk+- Dk is within the range of -0.5 to 0.5mm after the operation of the programmable logic controller, that is, if the calculated mass of weighed granular sample of the next sieving test begins to be smaller than the mass of the granular sample of the current sieving test or the calculated mass of weighed granular sample of the next sieving test begins to be convergent to the mass of the granular sample of the current sieving test, the particle size distribution characteristics of the granular sample obtained by the current sieving test can represent the particle size distribution characteristics of overall granular material,
and the error meets the requirement and the test is ended, wherein Dk denotes the median
granule diameter of the kth granular sample, Dk+ denotes the median granule diameter of
the (k+1)th granular sample, k denotes a kth sieving test, andDk+- Dk denotes the difference between the median granule diameter of the granular sample obtained by the kth sieving test and the median granule diameter of the granular sample obtained by the (k+1)th sieving test.
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| CN114563300A (en) * | 2022-02-28 | 2022-05-31 | 中冶华天工程技术有限公司 | On-line detection method for granulating effect of drum mixer |
| CN115415170A (en) * | 2022-09-01 | 2022-12-02 | 苏州胤煌精密仪器科技有限公司 | Granularity meter for intelligent particle classification |
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