What’s an ore crushing plant ?
Ore crushing plant is used for crushing and grinding ores in order to get size reduction. This crushing plant mainly includes crushing, grinding and screening. It can be replaced the first three stages of ore processing or ore dressing. Maybe you will ask what ore processing is.
Selection of ore crushers
Knowing the number of crushing stages we can now start to select the correct crusher for each reduction stage. Depending on operating conditions, feed size, capacity, hardness etc, there are always some options.
1. Primary ore crusher
For soft feed (below Mohs5) a horizontal shaft impactor(HSI) is normally the first option if capacity is not too high. For harder feed there is a choice between a gyratory crusher also named cone crusher or a jaw crusher .
Rule 1: Always use a jaw crusher if you can, being the most cost effective alternative.
Rule 2: For low capacity use jaw crusher and hydraulic hammer for oversize
Rule 3: For high capacities use jaw crusher with big intake opening
Rule 4: For very high capacities use gyratory crusher also named cone crusher.
2. Secondary ore crusher
In a rock crushing circuit, the second stage normally starts to be of importance for control of size and shape. Because of this the jaw crusher, in most cases, is disqualified as secondary crusher. Instead the cone crusher is used more frequently. Also in comminution (crushing and grinding) circuits for ore and minerals the cone crusher is frequently used as the secondary stage.
Compared to other crushers the cone crusher has some advantages making them very suitable for size reduction and shaping downstream a crushing circuit. Reason is the crushing chamber and the possibilities to change feed and discharge openings during operation.
3. Final crusher or tertiary crusher
For many rock and gravel crushing circuits the final crushing stage is of special interest. The final sizing and shaping will take place in this stage influencing the value of the final product. For hard rock circuits there are only two options, cone crushers or vertical shaft impact crusher (VSI).
Ore grinding process
Grinding is a powdering or pulverizing process using the rock mechanical forces of impaction, compression, shearing and attrition. Main machines in ore grinding process are ore mill equipment . The most common ore mills in mining are ball mill , Raymond mill and high pressure suspension mill. The selection of is according to customers’ requirements and the nature of the minerals.
The ore mill grinds the materials into fine powder by means of knocking and abrasion between the medium (steel balls, steel bars, gravel) and ore. The purpose is to dissemble the ore and achieve the proper size for the next ore processing. Ore grinding can be divided into grinding with media and without (self-grinding). It can also be divided into dry grinding and wet grinding. If the minerals with the unsuitable size return to the mill for re-grinding, it is called closed-circuit grinding. If the minerals is not returned to the mill or transferred to other mill for re-grinding, it is called open-circuit grinding.
Big ores are fed to the jaw crusher evenly and gradually by vibrating feeder through a hopper for primary crushing. After first crush, the material will transferred to other crusher by belt conveyor for secondary crush; the crushed materials will then transferred to vibrating screen for separating. Then, the materials will be transferred into the ball mill evenly for ore grinding.
After ball mill grinding, the ore fine material into the next process: classification. Because of the weight of solid particles is different, the speed of precipitate in liquid is different, according to this principle, spiral classifier can washed and classified the mixture ore. After classifying, ore particles are sent to flotation machines, depending on the mineral characteristics with different chemicals, making the needed ores and other materials to be separated.
Ore crushing plant working process
Generally, the whole ore production line consists of jaw crusher, ball mill, classifier, magnetic separator, flotation machines, thickener, dryers and other major equipment, with feeder , bucket elevator and conveyor can be composed of a complete ore production line. This production line feature with high efficiency, low energy, high capacity, economical and so on.