Determination of ore moisture and hardness

Determination of hardness coefficient (f value):

The hardness of the ore directly affects the production capacity of the crusher . To determine the hardness of ores often need measured hardness coefficient (i.e. f-number) for reference when beneficiation plant design and selection crusher mill.

The method of determining the f value is as follows:

Ores and rock specimens are made into standard test pieces with the following specifications: cylinder diameter 5 cm, height equal to diameter; cube 5X5X5 cm. Polish the test piece, place the test piece in the center of the pressure bearing plate in the order (note that the pressure bearing plate is parallel to the pressure receiving surface of the test piece), and start the motor at a speed of 5~10 kg/cm per second. The damage load is recorded until the test piece is destroyed. The calculation formula is as follows:

R=P/ab

Where: R-test piece compressive strength (kg / cm 2);

P-test piece damage load (kg);

A-the length of the pressure receiving surface of the test piece (cm);

b-The width (cm) of the pressure receiving surface of the test piece.

f=R/100

Where: f-hardness coefficient (kg / cm 2).

In order to obtain a more accurate value of f, the following questions should be noted: (1) The selected ore or rock specimen should be sufficiently representative;

(2) In view of the difference in compressive strength on different surfaces of the ore, the same specimen should generally be selected in three pieces in order to separately determine the f value of each surface and then take the average value;

(3) Each group of specimens should take 3~5 samples and take the average f value.

Determination of moisture:

They often divide the water into:

(1) External moisture, that is, surface moisture, covers the surface of the particles. When stored in the dry place, this part of the water gradually evaporates until the air is "air-dried".

(2) Analysis of moisture or sorption of water It is contained in the pores and cracks of the particles. The total water content is related to the pressure of water vapor and the relative humidity of the air.

(3) Combined water or crystal water.

In the ore dressing test, the first two items need to be measured. The sum of these two moistures is called total moisture or free water.

The moisture of ore and products will affect the process and equipment selection of washing, crushing, sieving, storage, dehydration, etc. It is more decisive for judging whether minerals may adopt wind power selection or dry magnetic separation.

Determination of moisture: In the laboratory, generally take 25 grams of wet sample pulverized to 1 metre, 50 grams of water can be taken, placed in a glass bowl of about 100 ml, covered with a frosted glass cover (also It can be weighed with a covered iron basin) to the nearest 0.01 gram. Then place the glass bowl in the oven (drying box), let the lid slant open, dry at 105~110 °C (drying time is not less than 8 hours), then move it to the dryer for cooling (about half Hours), quickly close the lid after cooling, and take out the weighing from the dryer. Finally calculate the moisture by the following formula:

W=(G1-G)/G *100%

In the formula;

W-moisture content (%);

G-dry sample weight (referring to drying sample) (g);

G1-wet sample weight (g).

The above determination requires at least two parallel samples, taking the arithmetic mean, and taking two decimal places as a percentage.

Pay attention to the following problems in the measurement:

(1) The process samples for the optional test are usually placed in the laboratory for a long time, so the external moisture has gradually dried, so the sorbed water content is generally measured.

(2) In order to determine the external moisture or total moisture, it must be sampled in time and measured in time. The bulk material can only be measured on the ground by first measuring the wet weight, then measuring the dry weight of the wind (drying for several days to night) and finally measuring the weight. External moisture and total moisture can be calculated in turn.

(3) If the sample has a large particle size; if the sample size is large, the external moisture can be measured in time at the sampling site, and then the air-dried test is broken and a small number of representative samples are taken to determine the sorption water.