Teach you to determine the most reasonable size of the mined product

The large ore from the stope is subjected to crushing operations to obtain a product with a smaller particle size, which provides a certain granularity for the grinding operation. This is the task of crushing ore.

For the crushing operation, the larger the particle size of crushed mineral, the higher the productivity of the crusher, the lower the cost of crushing. However, for grinding operations, the production capacity of the grinding machine will decrease with the increase of the ore size. Conversely, if the ore size is reduced, the production capacity of the grinding machine will be improved and the grinding cost can be reduced.

In general, in conventional crushing and grinding processes, the energy consumption of crushed ore is small, while the energy consumption of grinding is much greater.

According to statistics, crushed ore is only 12%-25% of the energy consumption of grinding, and the efficiency of crushed ore is higher than that of grinding.

Therefore, in the crushing system, the particle size of the mineral product should be reduced as much as possible, and the crushing effect should be fully utilized to improve the processing capacity of the grinding machine, which is called “multi-breaking and less grinding”.

Due to the reduction of the particle size of the crushed ore product, the diameter of the steel ball as the grinding medium can also be reduced, thereby increasing the grinding and stripping effect, increasing the production capacity of the grinding machine, and the steel ball consumption can also be reduced.

The final crushing granularity of the size and scale beneficiation plants have a great relationship, see Table 2-1

Table 2-1 The production capacity of the concentrator and the reasonable size range of the ball mill feed

Production capacity of ore dressing / (ton / day) The most reasonable grain size of the ball mill (the largest size of the nugget) / mm Production capacity of ore dressing / (ton / day) The most reasonable grain size of the ball mill (the largest size of the nugget) / mm
500 1000 10~15 6~12 2500 4000 5~10 4~8

The larger the size of the ore dressing plant, the more significant the economic effect of reducing the grain size of the grinding ore. For example, it is calculated that for a concentrating plant with a scale of 10 million tons/year, when the final particle size of the crushed ore is reduced from 20 to 0 mm to 12 to 0 mm, although the crushing capacity is reduced by 1/3, the ball mill is The capacity can be increased by 16%, the equipment investment can save 10.51 million yuan, the installed power is 3855 kW, and the power consumption per section is 3058. 5 kWh, accounting for about 10% of the whole plant's electricity consumption.

Of course, the data in Table 2-1 cannot be used mechanically, and other factors must be considered. For example, equipment factor, if the last section is a short-head cone crusher , the final particle size of the crushed product can not be less than 6~8 mm. In order to avoid the difficulties that occur during closed circuit work, the final ore size of the ore is often set at 8, 10 mm, or even larger, sometimes to 10 to 15 mm. If you install a roll machine, you can get a final grain size of 4 to 5 mm, but consider configuration and management issues. During the design, it should be ensured that the discharge port of each section of the crusher is appropriate and must not exceed the minimum allowable discharge port width. In order to obtain the smallest crushed product granularity under the condition that the equipment can work normally.

The optimum particle size of the crushed ore product has a great relationship with the crushing process, see Table 2-2.

Table 2-2 Appropriate particle size of the crushed product when crushing medium friable ore by different crushing processes

Serial number

Process name

Plant size

Suitable for open pit mining

Suitable particle size / mm

Suitable for underground mining

Suitable particle size / mm

Last break

Type of crusher

1

2

3

4

5

Two-stage open process

Two-stage closed circuit

Three-stage open process

Three-stage closed circuit process

Four-stage closed circuit process

Small

Medium

Medium

Medium and large

Large

-

-

25~30

8~15

3~6

25~30

10~15

20~25

8~10

——

Standard type

Short or standard

Short head

Short head

Roller

In summary, when determining the most reasonable size of the crushed ore, it is mainly related to the size of the ore dressing plant, the crushing equipment used, and the crushing process used. According to the principle of “multiple crushing and less grinding”, it is advisable to obtain the smallest crushing size.

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