Influence of sand return on grinding effect and calculation

The amount of sand return and the thickness of the grain size are not only related to the quality of the classification process, but also directly affect the production capacity and working conditions of the mill. Because the returning sand still needs to be returned to the grinding machine for treatment, it is often referred to as the "total ore" of the grinding machine. Since the flotation machine backing sand accounts for a considerable proportion (even the majority) of the total ore, the grain size of the reclaimed sand plays a relatively stable role in determining the particle size characteristics of the total ore, when the ore and the ore are given. When fluctuations occur in a short period of time, the impact on the mill is small. It can be seen that maintaining a certain amount of sand returning can make the working condition of the grinding machine relatively stable, so that the ore discharge and the size of the ore discharge of the grinding machine are relatively stable.

If the amount of sand returned is increased, the speed of the ore passing through the grinding machine can be increased and the ore can be shortened in the grinding machine without destroying the process balance (that is, the total amount of ore and the amount of ore discharged per unit time). Stay time. It is beneficial to reduce the over-grinding phenomenon and improve the production capacity of the grinding machine. However, if the amount of sand returned is too high, the mill will “swell” because the total ore supply exceeds the ore discharge capacity of the mill, or The amount exceeds the ability of the classifier to transport sand back, and the phenomenon of overflowing “running rough” and returning to the sand tank occurs.

The various beneficiation plant optimum return sand ratio to be determined by experiment. In actual operation, the sand return ratio is usually 150-600% (i.e., 1.5-6 times the original ore amount).

Screening is commonly used in production to determine the sand return ratio. During the measurement, the three products from the mine discharging machine, the sand returning and the overflowing of the classifier are separately sampled, and the sieve analysis is respectively carried out to obtain the particle size characteristic data of each product, and then according to the “material balance” (giving into the classifier) The amount of a certain fraction is equal to the amount of the fraction contained in the product discharged from the classifier.

In the closed-circuit grinding operation, the grader that returns to the grinding machine for re-grinding is called sand returning. The ratio of the amount of sand returned to the original ore amount of the mill is called the return sand ratio and can be expressed as a percentage.

Its calculation formula is as follows:

In the middle

C—return ratio, %;

α - the yield of a specified fraction in the ore discharge, %;

Î’-classifier overflow in the above specified fraction of the yield, %;

ν - the yield of the above specified fractions in the sand returning machine, %.

From the ore discharge of the grinding machine, the sand returning from the classifier and the overflow sampling and analysis, the values ​​of α, β, ν are obtained. The returning sand ratio can be calculated according to the above formula.

Double Girder Gantry Crane

The double girder Gantry Crane is commonly employed to handle large wokring pieces outdoors, which has strong hoisting capacity, large span, good stability, etc. Double girder gantry crane self-weight is larger than that of Single Girder Gantry Crane even for the same hoisting capacity weight, and the cost is also higher. According to the main girder structure, double girder gantry crane can be divided into 2 types: box girder and truss girder. Generally the box-type girder is the most commonly seen type.