Crushing, Screening & Conveying

Crushing, Screening & Conveying 2017-04-04T06:57:13+00:00
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Gyratory Crusher Design (2 replies)

8 months ago
vshastri 8 months ago

When designing a crusher for a mine which experiences a transition from soft to hard rock ores, how can you ensure the crusher will be able to optimally crush both ores for processing during the LOM production?

In addition, what metrics from the rock are integrated into crusher design? For example, is the uniaxial compressive strength (UCS) of a rock factored into the design of a crusher?

8 months ago
anjanisail 8 months ago

During the design of the Crushing Plant all the factors of the rock which may affect the design of the crusher have to be incorporated. As we know mine will experience a transition from soft to hard rock we have to design the crusher for hardest ore.

Characteristics of the rock which are important are;

  1. Crushing index
  2. Moisture
  3. Abrasiveness
  4. Shape
  5. Size
  6. % fines fraction
Paul Morrow
8 months ago
Paul Morrow 8 months ago

Designs are often based on the harder rock but it truly depends on your hardness variability. If you have an extremely hard rock but sampling has it representing only 5-10% of the pit; you may not want to design/oversize your crusher by 100% just for 7.5% of your reserve. It all depends on the geo-variability or geometallurgy as well as your risk tolerance. 

Compression test of rock types is a well established procedure for determining strength of materials. Compression tests for determining the crushability of rocks in dynamic mechanical apparatus have not been universally accepted.

A great article on crushing work index is

Determining the power requirement of rocks it not difficult. Which rock you design/size your crusher with is where failures are.

Others are: 

Rock crushability index is a useful relationship, analogous to the Bond work index, for determining crushing energy for various crusher feed and products. If it is known what size feed is to be fed to a crusher, one can either predict the crushing energy for a particular crusher product size, or the crusher product size, P80, can be predicted for various crushing energies.

Apart from ore hardness, the selection of the primary crusher is then made, based on the feed opening (maximum size of pieces the crusher will accept for reduction), the crusher setting, and the rated capacity of the machine (frequently the published capacity in the manufacturer's bulletin).  

Most operations I have been at have had crusher capacity problems not because the ore was hard but rather because it was large.

Obviously, fines in the feed make a difference in the machine capacity.

Considering the most primary crushers are sized conservatively and that certain conditions of feed can cause the machine to produce more than the anticipated tonnage, it is easy to understand why primary crushers so frequently run idle.

I hope others more knowledgeable members can add to this topic.

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