Crushing and grinding operations are undoubtedly crucial links in the entire mineral processing plant process. They not only foreshadow the mineral processing process but also crucially determine the plant’s technical and economic indicators, energy consumption, and ultimate profitability. Crushing and grinding plants continuously supply qualified material for subsequent separation operations (such as flotation, magnetic separation, and gravity separation). Failure of crushing and grinding operations can paralyze the entire production line. Below, we provide a comprehensive, detailed, and in-depth introduction to the crushing and grinding equipment selection guide.
Crushing & Grinding Core Role and "More Crushing, Less Grinding" Principle
In mineral processing and beneficiation, crushing and grinding are key steps in separating useful minerals from gangue, directly impacting beneficiation efficiency, energy consumption, and economic benefits. The fundamental purpose of crushing and grinding is to reduce the size of mined ore to a suitable particle size through mechanical force, thereby separating useful minerals from gangue. Because grinding consumes significantly more energy than crushing, the industry has adopted the optimization principle of “More Crushing, Less Grinding” to improve energy efficiency and reduce production costs.
Energy Consumption: Major Consumption
Crushing and grinding are the most energy-intensive processes in a mineral processing plant, typically accounting for over 65% of the plant’s total energy consumption. Consumption of media such as steel balls accounts for over 99% of the plant’s total energy consumption. Therefore, optimizing crushing and grinding processes and equipment selection is crucial for energy conservation, consumption reduction, and cost control in mineral processing plants.
The “Foundation” of Subsequent Operations
The uniformity and quality of the ground product particle size directly impact the recovery rate and concentrate grade of subsequent separation operations. Too coarse particle size prevents sufficient separation of useful minerals from gangue, resulting in a lower concentrate grade. Too fine a particle size easily generates slime, disrupting the separation process, causing loss of useful minerals, and resulting in significant energy waste.
More Crushing, Less Grinding Golden Rule
Given their critical role in the process and their significant cost contribution, the selection of crushing and grinding equipment is significant. The industry generally adheres to the golden rule of “more crushing, less grinding.” This is because crushing consumes less energy and is more efficient than grinding. Therefore, in the design of mineral processing technology, crushing operations should be used to reduce the ore particle size as much as possible, providing a finer feed for grinding and thereby reducing the total cost of the entire crushing and grinding system.
“More crushing, less grinding” is the core strategy for energy conservation and efficiency improvement in mineral processing. By optimizing the crushing process, strengthening pre-crushing, and reducing the particle size of the grinding feed, economic benefits can be significantly improved. Future technological developments will enable crushing to replace more grinding operations, achieving more energy-efficient mineral processing.
Crushing Equipment Selection Guide
Crushing operations are typically divided into three stages: coarse crushing, secondary crushing, and fine crushing, depending on the particle size. Different crusher types are required for each stage.
| Crushing Stage | Common Device Types | Working Principles | Advantages | Disadvantages | Application Scenarios |
| Coarse Crushing | Jaw Crusher | Bending extrusion | Simple structure, reliable operation, high crushing ratio, and large feed opening. | Crushing is intermittent, resulting in unproductive power consumption, poor finished product shape, and a high content of needle-like flakes. | It is the most widely used coarse crushing equipment for primary crushing of ores of various hardnesses. |
| Secondary Crushing | Cone Crusher | Laminated crushing | High crushing force, high efficiency, uniform product size, long wear part life, and a high degree of automation. | Complex structure and high price make it unsuitable for crushing sticky ores. | It is the absolute mainstay of secondary crushing, crushing various hard and abrasive ores. |
| Fine Crushing | Impact Crusher | Impact crushing | It offers a high crushing ratio, produces fine-quality product (mostly cubic), and boasts a relatively simple structure. | The hammer and impact plate wear quickly, making it unsuitable for crushing hard and abrasive ores. | It is suitable for crushing medium-to-low-hardness, brittle materials such as limestone and is widely used in the production of high-quality aggregates. |
Crushing Equipment Selection Tips
- For hard stone, use “extrusion”:For processing high-hardness materials such as granite and iron ore, a jaw crusher and cone crusher combination is preferred, utilizing the principles of extrusion and lamination for efficient crushing.
- For soft stone, use “impact”: For processing medium-to-low-hardness materials such as limestone, if high particle shape is required, use an impact crusher, which typically produces cubic products and offers high economic benefits.
- Process Matching: Ore concentrators typically use a two-stage or three-stage crushing process. Small and medium-sized concentrators or those processing ores with moderate particle sizes often use a two-stage, closed-circuit process consisting of a jaw crusher and a cone crusher. Large concentrators or those processing large, hard ores use a three-stage, closed-circuit process consisting of a jaw crusher, a standard cone crusher, and a short-head cone crusher to achieve a higher crushing ratio.
Grinding Equipment Selection Guide
| Grinding Stage | Grinding media | Working Characteristics | Advantages | Disadvantages | Application Scenarios |
| Ball Mill | Steel Balls | Point contact between the media and the material. | High production capacity, strong material adaptability, and the ability to produce very fine product particle sizes. | Over-grinding is prone to occur, resulting in high steel ball consumption. | This is the most widely used grinding equipment, suitable for fine grinding and regrinding of a variety of materials. |
| Rod Mill | Steel Bars | The media is in “line contact” with the material. | The product particle size is uniform, with minimal over-crushing, making it suitable for coarse grinding or preventing over-crushing. | The processing capacity is relatively low, making it unsuitable for fine grinding. | It is commonly used in gravity separation or magnetic separation processes for rare metal ores such as tungsten and tin, or as the first coarse grinding stage in secondary grinding. |
| Autogenous mill/SAG mill | Ore itself (or with a small amount of steel balls added) | Utilizing large ore chunks as the grinding medium. | The high crushing ratio eliminates the need for secondary and fine crushing, simplifying the process, reducing capital investment, and reducing dust and noise. | This grinding mill has stringent requirements for ore properties, making it difficult to handle stubborn ore (refractory ore chunks) and challenging to control energy consumption. | This mill is suitable for applications with large feed size variations and ore that exhibits good impact toughness. |
Grinding Equipment Selection Tips
- Fine Grinding with Ball Mills: When ore needs to be ground to a very fine particle size for optimal disaggregation, a ball mill is the preferred choice.
- Use Rod Mills for Uniform Coarse Grinding:If subsequent separation processes (such as gravity separation) require high particle size uniformity and excessive slime generation is undesirable, rod mills are the ideal choice.
- Simplify the Process with Autogenous Grinding: For ores with specific properties, autogenous or semi-autogenous grinding can significantly simplify the crushing process and significantly reduce initial investment, but thorough ore selectivity testing is required.
- Closed-circuit Grinding is Key: Modern mineral processing plants almost always operate in a closed-circuit system with a classifier. Classifiers (such as spiral classifiers or hydrocyclones) separate the qualified fraction of the ground product, while the unqualified coarse fraction is returned to the mill for further grinding. This effectively avoids over-grinding and improves grinding efficiency.
Future Trends in Crushing and Grinding
With technological advancements, crushing and grinding in mineral processing plants are constantly evolving, showing the following trends:
- Large-Scale and Energy-Efficient: Equipment is becoming larger to increase processing capacity per unit and reduce energy consumption and floor space per unit of product.
- Intelligent and Automated: Integrated intelligent monitoring systems enable remote monitoring, automatic adjustment of discharge openings, fault diagnosis, and optimized operation, thereby improving efficiency, reducing labor costs, and reducing the risk of downtime.
- Mobility and Flexibility: The rise of mobile crushing and screening plants addresses the space limitations and high construction costs of fixed production lines, making them particularly suitable for projects with dispersed mining areas or frequent site relocations.
- Systematic Simulation Design: Utilizing professional crushing and grinding process simulation software, through precise testing of ore properties and process simulation calculations, equipment selection and process optimization can be more scientifically optimized, providing the optimal crushing and grinding solution for the mineral processing plant.
Selecting the right crushing and grinding equipment for a mineral processing plant is a complex system that requires comprehensive consideration of multiple factors, including ore properties, processing capacity, product particle size requirements, investment budget, and operating costs. Only by deeply understanding the principle of “more crushing and less grinding”, accurately grasping the performance characteristics and applicable scope of various equipment, and actively embracing the latest industry technologies can you create a powerful, efficient and energy-saving crushing and grinding system for your mineral processing plant, laying a solid foundation for the long-term development of the enterprise.