What Is a Sieve Analysis?

Sieve analysis, referred to as sieve analysis, refers to the sieving work to determine the particle size composition of loose solid materials, that is, the method of sieving to divide the material into several levels of particle size analysis method.

Sieve analysis is one of the oldest particle size analysis methods, and it is also the most widely used particle size analysis method in experimental research and production practice. In essence, this method is to let materials (samples) of known quality continuously pass through a set of sieves that are reduced layer by layer in order to divide the materials into different particle sizes.

Generally speaking, the sieve analysis of mineral materials with a particle size greater than 6 mm belongs to the sieve analysis of coarse-grained materials, and a hand sieve made of steel plate punching or steel wire mesh is used as a sieve analysis tool. That is, a set of sieves with different sieve sizes is used to screen the minerals. The ore is divided into several grades, and then the weight of each grade of ore is weighed separately and recorded in a list. If raw ore mud and fine-grained grades adhere to large ore, they should be washed off. Otherwise it will affect the accuracy of the screening results.

The purpose of sieve analysis is to find the weight percentage of each grade of material, so as to determine their particle size composition. The weight of a grain size divided by the total weight of the screened material is the yield (or sieve balance) of the grain size material. Cumulative sieve percentage. It means the percentage of the material that is larger than a certain sieve hole to the total weight of the screened material; and the cumulative percentage under the sieve is the percentage of the material that is smaller than a certain sieve hole to the total weight of the screened material, or the percentage of throughput. ^[1]

Screening analysis Depending on the size range of the material to be analyzed, different screening tools can be used. For coarse-grained materials, hand sieving is often used for manual screening analysis; for materials with a particle size of several millimeters or less, a standard sieve needs to be used for screening analysis on a shaker.

A hand sieve is a sieve formed by fixing a sieve on a sieve frame. This sieve can be processed at any time according to needs. The standard sieve is a set of sieve with a certain proportion of sieve hole size, sieve hole size and wire diameter. When using a standard sieve, it is necessary to arrange the sieves in order from the top to the bottom of the screen. At this time, the order of the levels of each sieve is called the sieve order; in the stacked sieve order, two adjacent sieve The ratio of the sieve opening size is called the sieve ratio.

There is no uniform standard for the manufacture of standard sleeve screens and the screen ratios used in the world. In the United States, Britain, Canada and other countries, the screen ratio is 1.414; in France and the former Soviet Union, 71.259 is used as the public screen ratio. In order to promote technical exchanges between countries,

When using a standard sieve to analyze the particle size of the material, depending on the specific situation, a dry sieve can be used, or a combination of a dry sieve and a wet sieve can be used. When the material contains less water and mud, and the requirements for the analysis results are not strict, dry sieving can be directly performed; but when the material is severely bonded and the requirements for the analysis results are more stringent, dry and wet sieving must be used Screening in a combined manner.

Dry sieve in

When the mass loss of the material in the sieve analysis process does not exceed 1%, the sum of the masses of each size can be calculated as 100%. On this basis, the results obtained by the sieving analysis using the tabular method or the curve method can be processed.

The so-called table method, as the name implies, is to fill the screening results into the prescribed form. The commonly used form of the form is shown in Figure 1.

figure 1

The first column in Figure 1 is the particle size, that is, the size of the sieve holes of each two adjacent sieves used in the screening analysis test; the second column is the mass of each particle size obtained by sieving; the third column Is the yield of each grade, that is, the mass fraction of a certain grade in the material being screened; the fourth column is the cumulative yield (or positive cumulative yield) on the screen, which is the particle size of the screened material The mass fraction of the part that is larger than a certain sieve size, as indicated by 80.00% in the fourth row, the mass fraction of the particle size greater than 2mm in the screened material is 80.00%, and the mass fraction of less than 2mm is 20.00%. The fifth column is the cumulative yield under the sieve (or negative cumulative yield), that is, the mass fraction of the part of the material being sieved that has a particle size smaller than a certain sieve hole size.

The curve method is to draw the sieve analysis results into a curve in order to fully reflect their meaning and function. The curve drawn according to the sieve analysis result is called the particle size characteristic curve, which intuitively reflects the relationship between the yield of any particle size and the particle size of the material being screened.

When drawing the particle size characteristic curve, the material size is usually expressed on the abscissa and the cumulative yield is expressed on the ordinate. The rectangular coordinate system used can be arithmetic, semi-logarithmic, or full logarithmic. ^[3]