What are the commonly used processes for crushing ore

There are many types of crushing processes, but based on the configuration conditions of pre-screening and check screening, as well as the actual feed particle size and final crushing particle size range in production, the most commonly used crushing processes are divided into four types: two-stage open-circuit process, two-stage one-closed-circuit process, three-stage open-circuit process, and three-stage one-closed-circuit process.  

1. Two-stage crushing process

Two-stage open-circuit crushing process and two-stage closed-circuit crushing process

The two-stage open-circuit crushing process produces coarse crushed products and is only used in simple small-scale mineral processing plants or industrial pilot plants. The first stage may not require pre-screening. When the original ore contains high levels of clay and water, small-scale mineral processing plants may also adopt this process to ensure normal production.     

The two-stage closed-circuit process is suitable for small-scale mineral processing plants handling ore with relatively small particle sizes from underground mining. The second stage typically uses crushing equipment with a higher crushing ratio, such as impact crushers.

2. Three-stage crushing process

Three-stage open-circuit crushing process, three-stage closed-circuit crushing process

The three-stage closed-circuit crushing process, as a preparatory operation for grinding, has gained widespread application. Whether the ore is from underground or open-pit mining, as long as the clay content is not too high, it can effectively adapt, making it suitable for mineral processing plants of various scales.  

Compared to the three-stage closed-circuit process, the three-stage open-circuit crushing process produces coarser product particle sizes, but it simplifies the equipment configuration in the crushing workshop and reduces capital investment. Therefore, when the feed particle size requirements for grinding are not stringent, or when rod mills are used for coarse grinding, or when processing high-moisture clay-like ores and under terrain-constrained conditions, the three-stage open-circuit process can be adopted. When processing ore with high clay and moisture content, it does not easily cause screen and crushing chamber blockages like the three-stage closed-circuit process. The three-stage open-circuit crushing plus rod milling process does not require complex closed-circuit screening and return product transportation operations. Additionally, the rod mill is less affected by feed particle size, producing uniform discharge particle size, ensuring stable operation of the subsequent grinding process; simultaneously, the production process generates less dust. This process can be adopted when the grinding product requires a coarser particle size (for gravity separation) or when processing brittle, high-density minerals.

3. Four-stage crushing process

Only when processing extremely hard ore and in very large-scale mineral processing plants, to reduce the crushing ratio of each stage or increase the total crushing ratio, is the four-stage crushing process considered.     

4. Crushing process with washing operations  

When the original ore contains more than 5–10% clay (-3 mm) and has a moisture content exceeding 5–8%, fine particles tend to agglomerate, deteriorating production conditions in the crushing process. This can lead to blockages in the crushing chamber of the crusher and the screen openings of the screen, causing equipment accidents, as well as blockages and leaks in storage and transportation equipment, severely disrupting production. In such cases, washing facilities should be added to the crushing process. Adding washing facilities not only fully utilises equipment potential to ensure normal production and improves working conditions but also enhances the recovery rate of useful metals and expands resource utilisation. 

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