Mineral Processing

How to Identify and Analyze Mineral Particle Size?

What is mineral particle analytics, and why it is necessary?

In the mineral processing process, it is often necessary to understand the particle size composition of the material. In order to accurately identify the particle size composition of minerals, sieving analysis must be carried out to know how much each coarse and fine particle occupies in the mineral material. Therefore, sieving analysis is the most basic test in the beneficiation process. Through this experiment, learn to sieve analysis test technology and organize relevant experimental data.

 

The principle of mining and mineral particle analyze

 

The particle size analysis method that uses the sieving method to divide the material into several levels according to the particle size is called sieving analysis.

 

(1) Screening analysis of coarse-grained materials

 

In beneficiation tests, the particle size of the samples generally encountered is less than 100 mm. For materials less than 100 mm but greater than 0.045 mm, the particle size composition is usually determined by sieve analysis. Among them, the sieve analysis of 100 mm to 6 mm materials belongs to the sieve analysis of coarse-grained materials. It is carried out by a hand sieve made of steel plate punching or barbed wire. The method is to use a set of sieves with different sieve sizes. The ore is divided into several grades, and then each grade is weighed separately. If the original ore contains slime and high water content, and a large amount of slime and fine-grained ore adhere to the bulk ore, they should be cleaned so as not to affect the accuracy of the screening analysis.

 

(2) Sieve analysis of fine-grained materials

 

For materials in the particle size range of 6mm to 0.045mm, sieving analysis is usually carried out in the laboratory using standard test sieves.

 

Dry sieving is to first set the standard sieves in order, pour the sample into the upper sieve surface, cover the upper cover, put it on the vibrating sieve machine and sieve for 10-15 minutes, then remove the lower sieve, use Check and sieve by hand on a blanket or glossy paper. If the material under the sieve is less than 0.1-1% of the material on the sieve within one minute (there is no unified national standard for this value in my country, but it is related to the nature of the ore. The requirements for brittle materials should not be too high), it is considered that the sieving analysis has been completed, otherwise the sieving analysis will continue.

 

When the sample contains a lot of water and mud, and the materials are sticky to each other, the dry-wet combined sieving method should be used. First, pour the sample into a fine-mesh sieve (such as a 75 μm sieve), and sieve it in a water basin. Change the water in the basin every 1-2 minutes until the water in the basin is no longer cloudy. Dry and weigh the material on the sieve, and calculate the weight of the washed fine mud according to the difference between the weighed weight and the original weight. Then, the dried material on the screen is sieved by dry method. At this time, the amount of material under the screen at the bottom of the screen should be combined with the amount of fine mud washed out during wet screening. After the sieve analysis, weigh the materials of each grade with an industrial balance (accuracy 0.01g). The difference between the total weight of each grade and the weight of the original sample should not exceed 1% of the weight of the original sample, otherwise, it should be redone.

 

The minimum weight of the sample required for sieving analysis also depends on the particle size of the largest block in the sample, which can be calculated according to the sample size formula. The weight of the sample fed into the standard sieve each time is 25-150g. If it exceeds a lot, it should be carried out several times. When sieving directly with a 75μm sieve, the sample should not exceed 50g each time to avoid damage to the sieve.

 

The basic requirements when doing mineral analysis experimental

  1. Correctly take out the sample size for sieving and analysis, and sieve with a standard sieve and weigh out the weight of each grade;
  2. Fill in the data obtained from the test in the record sheet and make relevant calculations;
  3. Record the test of sieving analysis on the arithmetic graph paper and draw a curve of “particle size-weight percentage”.

 

Mineral analysis experimental equipment, utensils, and sample requirement

 

  1. Equipment: vibrating screen machine
  2. Utensils: standard sieve, balance, brush, stopwatch, white paper, etc.
  3. Sample: material with a particle size of -2.0mm.

 

Experimental steps and how to calculate the results

  • Steps:
  1. Take a sample of 200 grams.
  2. Arrange the standard sets of sieves from top to bottom in the order of decreasing sieve holes. The bottom layer is set with a sieve bottom, so don’t mess up the order.
  3. Pour the weighed sample into the top sieve, and then cover the sieve cover.
  4. Install the sieve on the vibrating screen machine, and then vibrate for 10~15 minutes.
  5. Remove the cover sieve, take out the bottom sieve, shake for one minute, if the weight of the product under the sieve is less than 1% of the product on the sieve, it is considered that the end point of the sieve analysis has been reached, otherwise, the sieve analysis must be continued.
  6. Weigh and record the materials of each particle size in the sieve analysis respectively.
  7. Compared with the weight of the original ore sample after sieving and analysis, the sum of the weight of each particle grade should not exceed 1%.

  • Calculate the results:

Error = (raw ore sample weight – the sum of the weight of each particle size after sieving analysis) ÷ raw ore sample weight × 100%

  1. Calculate the items listed in the above table and attach the table to the test report.
  2. According to the data in the table above, draw the curves of “particle size-cumulative weight percentage on the sieve” and “particle size-cumulative weight percentage under the sieve” on the arithmetic graph paper.
  3. At the end of the experiment, the ore samples are recovered, and the experimental equipment and site are cleaned.