Properties of the Ore to Be Crushed

Every ore to be crushed has its own crushability characteristics. While some ores are easy to crush, others require more energy to break. The physical structure of the product obtained after crushing can also vary; the crushed ore may turn to dust or may remain in large pieces. Each ore, while being crushed, also wears the crusher liners by a certain amount.

Size reduction tests to be carried out in the laboratory are important for preventing a possible wrong selection from the outset. Three important pieces of data about the breakage properties of ores — the chemical analysis of the rock, the abrasion index Ai and the work index Wi — can easily be determined by laboratory tests.

In crusher selection, the properties of the ore to be crushed are the most important determinant. The breakage properties of the same ore can also vary within certain ranges. For the selection to be made, the size of the ore, the size to which it will be crushed and its quantity must be known. At the crusher selection stage, the decision must be made by evaluating the crushing stages together with the possible factors that may arise at each stage.

The work index Wi value of ores is the most important measure of their crushability. Ores with a low work index are easy to crush and the energy required to break them is low. For ores with a high work index, the necessary crusher settings are kept high so that they do not overload the crusher.

Internal stresses are not desired in aggregates to be used in concrete production. Even if jaw crushers have been used in the first crushing stage, impact crushers should be used in the second stage to reduce the material coming out of the jaw crusher to the size for use.

It has been determined that double-toggle jaw crushers are highly effective in crushing ores with an Ai value higher than 0.7. Gyratory and cone crushers work like double-toggle jaw crushers, and these crushers are considered low-wear crushers.

The reduction ratio of impact crushers is higher than that of jaw and cone crushers, requiring fewer crushing stages in the size reduction process. However, using impact crushers to crush ores with an abrasion index greater than 0.15 is not recommended, as it causes excessive wear.