Ore Characteristics

Each ore has specific grindability index. While some ores can be crushed easily, others require higher energy for grinding. The physical structure of the product obtained after crushing may change. The ore can be crushed into powder or large chunks. Each ore abrades the crusher liners to some extent during crushing.

Size reduction tests carried out in a laboratory are essential to select the right crusher for duty. There are three important values for grindability: rock’s chemical analysis, abrasion index (Ai) and work index (Wi). These can be easily obtained through laboratory tests.

The characteristics of the ore to be crushed should be taken into account when selecting the right crusher model. The grindability characteristics of the same ore may vary within certain ranges. To make a good selection, the size of the ore, the size to which it will be reduced, and feed capacity must be known. When choosing a crusher type, the crushing stages and the potential factors that may arise at each stage should be taken into consideration.

Work index (Wi) of ores is the primary measure of grindability. Ores with a low work index are easy to crush and require a low amount of energy for size reduction. Ores with a high work index require more powerful crusher with bigger motors.

Impact crushers are not suited to crush ores with a high abrasion index, such as quartzite. Quickly wearing parts increase operational costs and downtime during wear parts changes.

Aggregates for construction need to be free of internal stresses. Even though jaw crushers are used as primary crushers, impact crushers should be employed as secondary crushers to reduce internal stress in the final product.

Double-toggle jaw crushers are known to have a high effectiveness in crushing ores with an Ai value above 0.7. Gyratory crushers and cone crushers operate like jaw crushers and are known as low-abrasion crushers.

Crushing rate of impact crushers is higher than that of jaw and cone crushers and they require fewer crushing stages in the size reduction operations. However, impact crushers are not recommended for crushing of ores with an abrasion index above 0.15, as they result in excessive abrasion.