A particle grading method and a particle gradation method

Abstract

The present invention relates to a particle classification method and a particle gradation method. In the present invention, by introducing a boundary indentation value, the particle size range of the theoretically screened particles of the screening equipment during classification is expanded, thereby greatly reducing the classification mixing rate of the finely classified material after screening by the traditional screening method. In addition, the particle classification method of the present invention can continue to utilize the existing traditional screening equipment, and has the characteristics of convenience, quickness, simplicity, science, high accuracy, strong rationality, wide adaptability, low cost, etc., and has a profound impact on improving the performance and quality of products prepared by finely classified materials in the future.

Description

Technical Field

[0001] The present invention relates to the field of ore dressing, and relates to a method for reasonably reducing the classification mixing rate of fine classified materials and a particle size distribution method. Background Art

[0002] In many industrial production and manufacturing industries, there are relatively clear requirements and regulations for the particle size distribution of raw materials, because the particle size distribution of raw material particles will affect the related properties and quality of the later finished products. For example, there are certain requirements for the particle size of raw materials when preparing special mortar; in the construction industry, the strength of cement mortar is significantly affected by the types of raw material particles and the different particle size ranges of raw material particles. Scholars such as S. Tsivilis have clearly proposed that the particles with a particle size less than 3 microns in cement should be as small as possible less than 10%, the particles with a particle size between 3 and 30 microns should be above 65%, and the particles with a particle size greater than 60 microns and less than 1 micron should be less. In fact, this is the requirement for the particle size distribution of clinker particles proposed from the aspects of the hydration rate and hydration degree of cement. The influence of cement particle size distribution on strength is mainly reflected in: 1) the original packing density of cement particles; 2) the hydration rate and hydration degree, which ultimately reflect the influence on the porosity of cement stone. A higher original packing density of particles and a higher degree of cement hydration will result in a smaller porosity of cement stone.

[0003] However, the current continuous screening method in the industry is to use an industrial multi-frequency vibrating screen and install sieves with corresponding mesh numbers according to the requirements for the particle size of the sieved particles. Similar traditional solutions will inevitably result in a large mixing rate of the sieved particles, making it difficult to meet the classification requirements, which will likely lead to the particle size of the sieved particles not reaching the ideal particle size for preparing the product, and this will also inevitably lead to the product performance prepared later not meeting the standards of related industries. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] The object of the present invention is to solve the problem that the fine classified materials after screening by the traditional sand and stone screening method have a large classification mixing rate, and provide a method that is simple, scientific, low-cost, and can continue to use the existing traditional screening equipment to reasonably reduce the classification mixing rate of the fine classified materials after screening by the traditional screening method, so as to achieve the control of the classification mixing rate of the fine classified materials and effectively solve the problem of the classification mixing rate of the fine classified material particles after screening by the traditional screening method.

[0006] Solutions for Solving the Problems

[0007] [1] The present invention provides a particle classification method, characterized in that it includes the following steps:

[0008] Determine the boundary particle size value a of the initial target particle size range, with the unit of mm, from large to small as a1, a2, a3, ……, a n-1 、a n , thus obtaining the initial target particle size ranges as (a1, a2), (a2, a3), ……, (a n-1 , a n );

[0009] Set the boundary indentation value b, where 0.1 ≤ b ≤ 0.4;

[0010] Determine the boundary values c of the new particle size range, with the unit of mm, from large to small as c1, c2, c3, c4, c5, c6, c7, ……;

[0011] Take the new boundary value c as the screening size scale, and make the particles pass through sieves with apertures of c1, c2, c3, c4, c5, c6, c7 …… from top to bottom in turn, so as to obtain two series of particle classification discharges of particles with particle size ranges of (c1, c2), (c3, c4), (c5, c6), …… and particles with particle size ranges of (c2, c3), (c4, c5), ……, or obtain three series of particle classification discharges of particles with particle size ranges of (c1, c2), (c4, c5), ……, particles with particle size ranges of (c2, c3), (c5, c6), …… and particles with particle size ranges of (c3, c4), (c6, c7), ……

[0012] [2] According to the particle classification method described in [1] above, when the range of the boundary indentation value b is 0.1 ≤ b < 0.2, c1 = (1 - b) × a1 + b × a2, c2 = 0.5 × a1 + 0.5 × a2, c3 = b × a1 + (1 - b) × a2, c4 = (1 - b) × a2 + b × a3, c5 = 0.5 × a2 + 0.5 × a3, c6 = b × a2 + (1 - b) × a3, ……, c 3n-5 = (1 - b) × a n-1 + b × a n , c 3n-4 = 0.5 × a n-1 + 0.5 × a n , c 3n-3 = b × a n-1 + (1 - b) × a n .

[0013] [3] According to the particle classification method described in [1] above, when the range of the boundary indentation value b is 0.2 ≤ b ≤ 0.3, c1 = (1 - b) × a1 + b × a2, c2 = b × a1 + (1 - b) × a2, c3 = (1 - b) × a2 + b × a3, c4 = b × a2 + (1 - b) × a3, ……, c2n-3 =(1 - b)×a n-1 +b×a n , c 2n-2 =b×a n-1 +(1 - b)×a n 。

[0014] [4] According to the particle classification method described in the above [1], when the range of the boundary indentation value b is 0.3 < b ≤ 0.4, c1 = a1, c2 = (1 - b)×a1 + b×a2, c3 = b×a1 + (1 - b)×a2, c4 = a2, c5 = (1 - b)×a2 + b×a3, c6 = b×a2 + (1 - b)×a3, ……, c 3n-5 =a n-1 , c 3n-4 =(1 - b)×a n-1 +b×a n , c 3n-3 =b×a n-1 +(1 - b)×a n , c 3n-2 =a n 。

[0015] [5] According to the particle classification method described in any one of the above [1]-[4], the mixing rate of the classified discharge of the particles is less than 10%, preferably less than 5%

[0016] [6] A particle gradation method, characterized in that it includes:

[0017] grading the particles by the particle classification method described in any one of the above [1]-[4] to obtain the step of classified discharge of the particles; and

[0018] the step of remixing the classified discharge of the particles.

[0019] Effects of the Invention

[0020] The beneficial effects of the present invention are:

[0021] 1) By introducing the boundary indentation value, the particle size range of the theoretically screened particles of the screening equipment during classification is expanded, effectively solving the problem of excessive mixing rate of the classified particles after the traditional continuous screening method at the present stage, so as to achieve the goal of reasonably reducing the mixing rate of the fine classified material;

[0022] 2) The method of the present invention has the characteristics of being convenient, fast, simple, high in accuracy, strong in rationality, wide in adaptability, etc., and has a profound impact on improving the performance and quality of products prepared from fine classified materials in the future. Specific Embodiments

[0023] The embodiments of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various changes can be made within the scope of the claimed invention. Embodiments obtained by appropriately combining different embodiments and appropriately combining the technical means disclosed in the respective examples are also included in the technical scope of the present invention. In addition, all the documents described in this specification are incorporated herein by reference as references.

[0024] Unless otherwise defined, the technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0025] In this specification, the numerical range expressed by "numerical value A to numerical value B" means a range including the end point numerical values A and B.

[0026] In this specification, the term "mixed grade rate" refers to the ratio of the number of particles with actual particle sizes outside the specified particle size range to the total number of particles falling within the specified particle size range during actual screening.

[0027] Unless otherwise stated, the "many", "multiple", "several" in "many", "multiple kinds", "several" etc. mean a numerical value of 2 or more.

[0028] In this specification, unless otherwise specified, "%" all represent mass percentage.

[0029] In this specification, the "some / certain / preferred embodiments", "embodiments", etc. mentioned refer to that the specific elements (for example, features, structures, properties, and / or characteristics) related to the embodiment are included in at least one of the embodiments described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0030] The present invention expands the particle size range of the theoretically screened particles of the screening equipment during classification by introducing an adjustment value, so that the classification mixed grade rate of the fine classification material after screening by the traditional screening method can be reasonably reduced on the basis of continuing to use the existing traditional screening equipment.

[0031] The method for reasonably reducing the classification mixed grade rate of the fine classification material of the present invention includes the following steps: 1) determining the initial target particle size range; 2) setting the boundary indentation value; 3) obtaining the boundary values of the new particle size range through calculation; 4) enabling the particles to pass through the sieves of each stage with apertures near the new boundary values from top to bottom, so as to obtain two-way discharge or three-way discharge, or even more-way discharge. The following will explain each step in detail.

[0032] Step 1)

[0033] First, determine the boundary particle size values a of the initial target particle size range, with the unit of mm. From large to small, they are a1, a2, a3, ……, a n-1 、a n , and thus the initial target particle size ranges are obtained as (a1, a2), (a2, a3), ……, (a n-1 , a n ).

[0034] Generally, when determining the initial boundary particle size values, they are determined according to the commonly used sieve pore sizes. Currently, the grading test device for manufactured sand usually uses a screening device including seven grades of sieve pore sizes. The pore sizes of these seven grades of sieves can usually be 4.75 mm, 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, 0.15 mm, and 0.075 mm respectively. Therefore, when screening sand and gravel particles, the initial boundary particle size value a can be set near these pore size values. For example, when n is 7, a1, a2, a3, a4, a5, a6, a7 can be 5 mm, 2.5 mm, 1 mm, 0.5 mm, 0.25 mm, 0.1 mm, 0.05 mm, etc. respectively.

[0035] Step 2)

[0036] In this step, set the boundary indentation value b. In the present invention, the value of b is limited to 0.1 - 0.4. For example, the value of b can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, etc.

[0037] In the present invention, by introducing the boundary indentation value b, the particle size range of the theoretically screened particles of the screening equipment during classification can be expanded, so that the screened particles in one original series can be divided into two series or three series, thereby reducing the mixing rate.

[0038] Step 3)

[0039] In this step, the boundary values c of the new particle size range can be obtained through calculation, with the unit of mm. From large to small, they are c1, c2, c3, c4, c5, c6, c7, …….

[0040] When the range of the boundary indentation value b is 0.1 ≤ b < 0.2, c1 = (1 - b) × a1 + b × a2, c2 = 0.5 × a1 + 0.5 × a2, c3 = b × a1 + (1 - b) × a2, c4 = (1 - b) × a2 + b × a3, c5 = 0.5 × a2 + 0.5 × a3, c6 = b × a2 + (1 - b) × a3, ……, c 3n-5 = (1 - b) × a n-1 + b × a n , c 3n-4 = 0.5 × a n-1+0.5×a n ,c 3n-3 = b×a n-1 +(1 - b)×a n 。

[0041] When the range of the boundary indentation value b is 0.2 ≤ b ≤ 0.3, c1 = (1 - b)×a1 + b×a2, c2 = b×a1 + (1 - b)×a2, c3 = (1 - b)×a2 + b×a3, c4 = b×a2 + (1 - b)×a3,..., c 2n-3 = (1 - b)×a n-1 + b×a n ,c 2n-2 = b×a n-1 +(1 - b)×a n 。

[0042] When the range of the boundary indentation value b is 0.3 < b ≤ 0.4, c1 = a1, c2 = (1 - b)×a1 + b×a2, c3 = b×a1 + (1 - b)×a2, c4 = a2, c5 = (1 - b)×a2 + b×a3, c6 = b×a2 + (1 - b)×a3,..., c 3n-5 = a n-1 ,c 3n-4 = (1 - b)×a n-1 + b×a n ,c 3n-3 = b×a n-1 +(1 - b)×a n ,c 3n-2 = a n 。

[0043] Step 4)

[0044] Take the new boundary value c as the screening size scale, so that the particles pass through the sieves with apertures of c1, c2, c3, c4, c5, c6,... from top to bottom in turn, thereby obtaining two series of particle classification discharges of particles with particle size ranges of (c1, c2), (c3, c4), (c5, c6),... and particles with particle size ranges of (c2, c3), (c4, c5),..., or obtaining three series of particle classification discharges of particles with particle size ranges of (c1, c2), (c4, c5),..., particles with particle size ranges of (c2, c3), (c5, c6),... and particles with particle size ranges of (c3, c4), (c6, c7),...

[0045] It should be noted that the sieve hole sizes of the actual sieve mesh are non - continuous values. Therefore, in actual operation, the sieve hole size of the sieve mesh is the nearest neighbor value of c. For the sake of convenient expression, c is still used as the sieve hole size of the sieve mesh in this specification.

[0046] Specifically, using the series of values of c as the sieve pore sizes of the series of sieves, screening is carried out by a vibrating screen, and the particle size grades and product series are determined according to the following method for each stage of screening.

[0047] 1) When the range of the boundary indentation value b is 0.2 ≤ b < 0.3,

[0048] After the particles pass through the sieves c1, c2, ……, c 2n-2 at each stage respectively, the particles that pass through c1 and are retained by c2, i.e., (c1, c2), are taken as the particles corresponding to the original target particle size range (a1, a2), the particles that pass through c3 and are retained by c4, i.e., (c3, c4), are taken as the particles corresponding to the original target particle size range (a2, a3), and so on. The particles that pass through c 2n-3 and are retained by c 2n-2 ), i.e., the particles that pass through c 2n-3 and are retained by c 2n-2 are taken as the particles corresponding to the original target particle size range (a n-1 , a n ), thus forming a continuous particle size distribution with particle sizes in the range of a1 - a n . By compounding, the particle size distribution with the required fineness modulus can be obtained.

[0049] Similarly, for the other particle size ranges separated out, i.e., (c2, c3), (c4, c5), ……, (c 2n-4 and are retained by c 2n-3 ), the particles respectively correspond to the original particle size ranges (0.5×a1 + 0.5×a2, 0.5×a2 + 0.5×a3), (0.5×a2 + 0.5×a3, 0.5×a3 + 0.5×a4), ……, (0.5×a n-2 + 0.5×a n-1 , 0.5×a n-1 + 0.5×a n ). Thus, a continuous particle size distribution with particle sizes in the range of (0.5×a1 + 0.5×a2) to (0.5×a n-1 + 0.5×a n ) is also formed. By compounding, the particle size distribution with the required fineness modulus can be obtained.

[0050] In this way, through the design of the outlets with different particle sizes of the screen, two-way discharging can be achieved, that is, discharging corresponding to (a1, a2), (a2, a3), ……, (a n-1 , a n ) and (0.5×a1 + 0.5×a2, 0.5×a2 + 0.5×a3), (0.5×a2 + 0.5×a3, 0.5×a3 + 0.5×a4), ……, (0.5×a n-2 + 0.5×a n-1 , 0.5×an-1 +0.5×a n ) Two series of granular classified discharge.

[0051] 2) When the range of the boundary indentation value b is 0.1 ≤ b < 0.2, two-way discharge can be carried out similarly to the above, or three-way discharge can be carried out as follows.

[0052] The particles pass through c1, c2,..., c 3n-3 After each sieve, take (c1, c2), that is, the particles under the c1 sieve and above the c2 sieve, as the particles corresponding to the original target particle size range (a1, 1×a1 / 6 + 5×a2 / 6), take (c4, c5), that is, the particles under the c4 sieve and above the c5 sieve, as the particles corresponding to the original target particle size range (1×a1 / 6 + 5×a2 / 6, 1×a2 / 6 + 5×a3 / 6), and so on, take (c 3n-5 , c 3n-4 ) That is, c 3n-5 The particles under the sieve and above the c 3n-4 Sieve are taken as the particles corresponding to the original target particle size range (1×a n-2 / 6 + 5×a n-1 / 6, 1×a n-1 / 6 + 5×a n / 6). Thus, a continuous particle size distribution with a particle size in the range of a1 to 1×a n-1 / 6 + 5×a n / 6 is formed. Through compounding, the particle size distribution with the required fineness modulus can be obtained.

[0053] The other particle size ranges (c2, c3), (c5, c6),..., (c 3n-7 , c 3n-6 ), (c 3n-4 , c 3n-3 ) of the sieved particles respectively correspond to the particle size ranges (5×a1 / 6 + 1×a2 / 6, 5×a2 / 6 + 1×a3 / 6), (5×a2 / 6 + 1×a3 / 6, 5×a3 / 6 + 1×a4 / 6),..., (5×a n-2 / 6 + 1×a n-1 / 6, 5×a n-1 / 6 + 1×a n / 6), (5×a n-1 / 6 + 1×a n / 6, a n ) of the particles. Thus, a continuous particle size distribution with a particle size in the range of 5×a1 / 6 + 1×a2 / 6 to a n is also formed. Through compounding, the particle size distribution with the required fineness modulus can be obtained.

[0054] The other particle size ranges (c3, c4), (c6, c7),..., (c3n -6, c 3n A series of particles of (-5) respectively correspond to the particle size ranges (0.5×a1 + 0.5×a2, 0.5×a2 + 0.5×a3), (0.5×a2 + 0.5×a3, 0.5×a3 + 0.5×a4), ……, (0.5×a n-2 + 0.5×a n-1 , 0.5×a n-1 + 0.5×a n ). Thus, a continuous particle size distribution with a particle size in the range of 0.5×a1 + 0.5×a2 to 0.5×a n-1 + 0.5×a n is formed. By compounding, the particle size distribution with the required fineness modulus can be obtained.

[0055] In this way, through the design of the outlets with different particle sizes of the screening machine, three-way discharging can be achieved, that is, (a1, 1×a1 / 6 + 5×a2 / 6), (1×a1 / 6 + 5×a2 / 6, 1×a2 / 6 + 5×a3 / 6), ……, (1×a n-2 / 6 + 5×a n-1 / 6, 1×a n-1 / 6 + 5×a n / 6); (5×a1 / 6 + 1×a2 / 6, 5×a2 / 6 + 1×a3 / 6), (5×a2 / 6 + 1×a3 / 6, 5×a3 / 6 + 1×a4 / 6), ……, (5×a n-2 / 6 + 1×a n-1 / 6, 5×a n-1 / 6 + 1×a n / 6), (5×a n-1 / 6 + 1×a n / 6, a n ) and (0.5×a1 + 0.5×a2, 0.5×a2 + 0.5×a3), (0.5×a2 + 0.5×a3, 0.5×a3 + 0.5×a4), ……, (0.5×a n-2 + 0.5×a n-1 , 0.5×a n-1 + 0.5×a n ) for three series of particles to be discharged in a graded manner.

[0056] 3) When the range of the boundary indentation value b is 0.3 < b ≤ 0.4, two-way discharging can be carried out similarly to the above, or three-way discharging can be carried out as follows.

[0057] The particles pass through c1, c2, ……, c 3n-3After screening at each level, take (c4, c5), that is, the particles passing through the c4 sieve and retained on the c5 sieve, as the particles corresponding to the original target particle size range (1×a1 / 3 + 2×a2 / 3, 1×a2 / 3 + 2×a3 / 3). Take (c7, c8), that is, the particles passing through the c4 sieve and retained on the c5 sieve, as the particles corresponding to the original target particle size range (1×a2 / 3 + 2×a3 / 3, 1×a3 / 3 + 2×a4 / 3), and so on. Take (c 3n-5 , c 3n-4 ) that is, the particles passing through the c 3n-5 sieve and retained on the c 3n-4 sieve as the particles corresponding to the original target particle size range (1×a n-2 / 3 + 2×a n-1 / 3, 1×a n-1 / 3 + 2×a n / 3). Thus, a continuous particle size distribution with particle sizes ranging from a1 to 1×a n-1 / 6 + 5×a n / 6 is formed. Through compounding, the particle size distribution with the required fineness modulus can be obtained.

[0058] The other particle size ranges separated out, namely (c2, c3), (c4, c5), ……, (c 2n-4 , c 2n-3 ), can respectively be used as particles in the particle size ranges (a1, a2), (a2, a3), ……, (a n-1 , a n ). Thus, a continuous particle size distribution with particle sizes ranging from a1 to a n is also formed. Through compounding, the particle size distribution with the required fineness modulus can be obtained.

[0059] The series of particles in the other particle size ranges separated out, (c3, c4), (c6, c7), ……, (c 3n-6 , c 3n - 5), respectively correspond to the particle size ranges (2×a1 / 3 + 1×a2 / 3, 2×a2 / 3 + 1×a3 / 3), (2×a2 / 3 + 1×a3 / 3, 2×a3 / 3 + 1×a4 / 3), ……, (2×a n-2 / 3 + 1×a n-1 / 3, 2×a n-1 / 3 + 1×a n / 3) of particles. Thus, a continuous particle size distribution with particle sizes ranging from 2×a1 / 3 + 1×a2 / 3 to 2×a n-1 / 3 + 1×a n / 3 is also formed. Through compounding, the particle size distribution with the required fineness modulus can be obtained.

[0060] As described above, through the design of the outlets of different particle sizes of the screening machine, three-way discharging can be achieved, that is, (1×a1 / 3 + 2×a2 / 3, 1×a2 / 3 + 2×a3 / 3), (1×a2 / 3 + 2×a3 / 3, 1×a3 / 3 + 2×a4 / 3), ……, (1×a n-2 / 3 + 2×a n-1 / 3, 1×a n-1 / 3 + 2×a n / 3); (a1, a2), (a2, a3), ……, (a n-1 , a n ) and (2×a1 / 3 + 1×a2 / 3, 2×a2 / 3 + 1×a3 / 3), (2×a2 / 3 + 1×a3 / 3, 2×a3 / 3 + 1×a4 / 3), ……, (2×a n-2 / 3 + 1×a n-1 / 3, 2×a n-1 / 3 + 1×a n / 3) for the classified discharging of three series of particles.

[0061] According to the two-way or three-way discharging scheme formed according to the above scheme, two or three series of continuous single-sized particles with a low mixing rate can be obtained. In the present invention, the mixing rate of the classified discharging of particles is 15% or less, preferably 10% or less, more preferably 5% or less. For example, the mixing rate can be 15%, 12%, 10%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, etc.

[0062] Theoretically, the larger the boundary indentation value b, the smaller the classification mixing rate of the finally obtained fine classified material. According to specific production requirements, a fine classification technical scheme for multi-way tailing particles with more than three ways can also be used, or a fine classification technical scheme for multi-way tailing particles can be adopted in the coarse particle size range, and another fine classification technical scheme for multi-way tailing particles can be adopted in the fine particle size range. Thus, a fine classification technology that can be flexibly adjusted and combined according to product requirements is truly realized.

[0063] In addition, the present invention also provides a particle grading method, which includes: a step of classifying particles through the particle classification method as described above to obtain classified discharging of particles; and a step of remixing the classified discharging of particles.

[0064] The fine classification technology of the present invention can provide continuous single-sized particles with a very low mixing rate, so the remixing particles obtained through remixing can meet the required particle size and performance.

[0065] Examples

[0066] The present invention will be described in detail below through embodiments. The examples of the embodiments are intended to explain the present invention and should not be construed as limiting the present invention. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the field or according to the product specifications are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchases.

[0067] Comparative Example 1

[0068] In Comparative Example 1, a conventional classification method was used to classify the sand and gravel. Specifically, a multi - frequency vibrating screen equipped with a series of sieves with apertures of 5 mm, 2.5 mm, 1 mm, 0.5 mm, 0.25 mm, and 0.1 mm was used to classify the sand and gravel. The sieved sand obtained in this way is a series with particle size ranges of (5, 2.5), (2.5, 1), (1, 0.5), (0.5, 0.25), (0.25, 0.1) (unit: millimeter).

[0069] The mixed - grade rate of the sand and gravel obtained by the above - mentioned classification method is about 30%.

[0070] Example 1

[0071] In this embodiment, the fine - classification method of the present invention is applied to classify the sand and gravel.

[0072] First, the boundary values a1, a2, a3, a4, a5, a6 of the initial target particle - size range (i.e., n = 6) are set to 5 mm, 2.5 mm, 1 mm, 0.5 mm, 0.25 mm, and 0.1 mm respectively. Then the initial target particle - size range is (5, 2.5), (2.5, 1), (1, 0.5), (0.5, 0.25), (0.25, 0.1) (unit: millimeter).

[0073] Then, the boundary indentation value b is set to 0.25. Then, the boundary values c of the new particle - size range can be obtained by calculation:

[0074] c1=(1 - b)×a1 + b×a2 = 0.75×5+0.25×2.5 = 4.375 mm,

[0075] c2 = b×a1+(1 - b)×a2 = 0.25×5+0.75×2.5 = 3.125 mm,

[0076] And so on, c3, c4, c5, c6, c7, c8, c9, c 10 are 2.125 mm, 1.375 mm, 0.875 mm, 0.625 mm, 0.4375 mm, 0.3125 mm, 0.2125 mm, 0.1375 mm respectively.

[0077] The closest screen numbers corresponding to the above new boundary values c are: 4.5 mm, 3.15 mm, 2.24 mm, 1.4 mm, 0.85 mm, 0.63 mm, 0.425 mm, 0.315 mm, 0.212 mm, 0.14 mm.

[0078] By continuously screening the sand and gravel using a multi - frequency vibratory screen equipped with the above screen, two series of screened sands with particles of (4.375, 3.125), (2.125, 1.375), (0.875, 0.625), (0.4375, 0.3125), (0.2125, 0.1375) (unit: mm) and particles of (3.125, 2.125), (1.375, 0.875), (0.625, 0.4375), (0.3125, 0.2125) (unit: mm) were obtained.

[0079] Among them, the series of (4.375, 3.125), (2.125, 1.375), (0.875, 0.625), (0.4375, 0.3125), (0.2125, 0.1375) corresponds to particles with an original particle - size range of (5, 2.5), (2.5, 1), (1, 0.5), (0.5, 0.25), (0.25, 0.1); the series of (3.125, 2.125), (1.375, 0.875), (0.625, 0.4375), (0.3125, 0.2125) corresponds to particles with a particle - size range of (0.5×a1 + 0.5×a2, 0.5×a2 + 0.5×a3), (0.5×a2 + 0.5×a3, 0.5×a3 + 0.5×a4), ……, (0.5×a n-2 +0.5×a n-1 , 0.5×a n-1 +0.5×a n ), specifically (3.75, 1.75), (1.75, 0.75), (0.75, 0.375), (0.375, 0.1875), (0.1875, 0.09375). The units of the above values are all mm.

[0080] The mixed - grade rate of the screened sand obtained in this embodiment is 5% or less.

[0081] Industrial applicability

[0082] The present invention expands the particle - size range of the theoretically screened particles of the screening equipment during classification by introducing a boundary indentation value, thereby reducing the mixed - grade rate on the basis of using existing screening equipment. Moreover, the method of the present invention is convenient, fast, simple, highly accurate, and widely adaptable, so it can be applied to actual production.

Claims

1. A particle classification method, characterized in that, It includes the following steps: Determine the boundary particle size value a of the initial target particle size range, with the unit of mm. From large to small, they are a1, a2, a3, ……, a n-1 , a n , and thus obtain the initial target particle size ranges as (a1, a2), (a2, a3), ……, (a n-1 , a n ); Set the boundary indentation value b, where 0.1 ≤ b ≤ 0.4; Determine the boundary values c of the new particle size range, with the unit of mm, from large to small as c1, c2, c3, c4, c5, c6, c7, ……; Take the new boundary value c as the screening size scale, and the series values of c as the screen hole sizes of the series of sieves, so that the particles pass through the sieves with apertures of c1, c2, c3, c4, c5, c6, c7, …… levels from top to bottom in sequence, thereby obtaining two series of particle classification discharges of particles with particle size ranges of (c1, c2), (c3, c4), (c5, c6), …… and particles with particle size ranges of (c2, c3), (c4, c5), ……, or obtaining three series of particle classification discharges of particles with particle size ranges of (c1, c2), (c4, c5), ……, particles with particle size ranges of (c2, c3), (c5, c6), …… and particles with particle size ranges of (c3, c4), (c6, c7), …… When the range of the boundary indentation value b is 0.1 ≤ b < 0.2, c1 = (1 - b) × a1 + b × a2, c2 = 0.5 × a1 + 0.5 × a2, c3 = b × a1 + (1 - b) × a2, c4 = (1 - b) × a2 + b × a3, c5 = 0.5 × a2 + 0.5 × a3, c6 = b × a2 + (1 - b) × a3, ……, c 3n-5 = (1 - b) × a n-1 + b × a n , c 3n-4 = 0.5 × a n-1 + 0.5 × a n , c 3n-3 = b × a n-1 + (1 - b) × a n ; When the range of the boundary indentation value b is 0.2 ≤ b ≤ 0.3, c1 = (1 - b) × a1 + b × a2, c2 = b × a1 + (1 - b) × a2, c3 = (1 - b) × a2 + b × a3, c4 = b × a2 + (1 - b) × a3, ……, c 2n-3 = (1 - b) × a n-1 + b × a n , c 2n-2 = b × a n-1 + (1 - b) × a n ; When the range of the boundary indentation value b is 0.3 < b ≤ 0.4, c1 = a1, c2 = (1 - b) × a1 + b × a2, c3 = b × a1 + (1 - b) × a2, c4 = a2, c5 = (1 - b) × a2 + b × a3, c6 = b × a2 + (1 - b) × a3, ……, c 3n-5 = a n-1 , c 3n-4 = (1 - b) × a n-1 + b × a n , c 3n-3 = b × a n-1 + (1 - b) × a n , c 3n-2 = a n .

2. The particle classification method according to claim 1, wherein the misclassification rate of the particle classification discharge is less than 10%.

3. The particle classification method according to claim 1 or 2, wherein the misclassification rate of the particle classification discharge is less than 5%.

4. A particle gradation method, characterized in that, It includes: The step of classifying particles by the particle classification method according to any one of claims 1 - 3 to obtain particle classification discharge; and The step of compounding the particle classification discharge.