Milling is a core step in the mining process that determines resource utilization and operating costs; the suitability of grinding technology directly impacts more than 30% of a mine’s economic benefits. Traditional grinding solutions generally suffer from high energy consumption, severe over-grinding, and poor equipment compatibility. This latest milling process guide for 2026 provides a comprehensive explanation from the perspectives of process definition, core objectives, equipment, and process steps, helping mining companies quickly master grinding solutions suitable for their needs and achieve cost reduction and efficiency improvement.
The milling process is a flow that involves crushing, grinding, and classifying ores to achieve the full liberation of valuable minerals. Properly selecting open/closed-circuit processes and single/multi-stage milling schemes can save energy and is suitable for the beneficiation of most ores, including gold, iron, and lithium.
What is Milling Process in Mining?
Definition:
Milling process (grinding process) refers to the process in mineral processing where small pieces of ore, after being crushed, are further ground to a micron-level particle size using the impact and grinding action of grinding equipment. It is not an isolated process; it is typically closely connected to the crushing process upstream, responsible for processing ore smaller than 25mm into the required fineness, and connected downstream to separation processes such as flotation and magnetic separation. Therefore, milling is a necessary preliminary step for achieving the liberation of valuable minerals and gangue.
Crushing Vs. Milling Process
The core difference between crushing and milling process lies primarily in the range of particle sizes processed. Crushing mainly reduces ore from large pieces (tens of centimeters) to millimeters, while milling further refines it to the micrometer or even nanometer scale. However, in actual mining production, the principle of “more crushing, less milling” is particularly important, meaning reducing ore particle size as much as possible during the crushing stage to reduce grinding energy consumption and optimize production costs.
Types Of Milling Process
- Open-circuit milling lacks a classification and return step, making it suitable only for small, simple beneficiation plants or scenarios with low requirements for product particle size.
- Closed-circuit milling, combined with classification equipment, recycles coarse particles and is currently the mainstream beneficiation solution.
- Single-stage milling is suitable for processing small, easily grindable, coarse-grained disseminated ores.
- Multi-stage milling is suitable for precious and non-ferrous metal ores with fine disseminated particle size and high hardness, such as gold mines containing quartz veins.
The ultimate goal of milling process
Particle Size Control
If the grinding fineness is insufficient, valuable minerals will not be fully liberated, directly reducing the recovery rate in subsequent beneficiation stages and wasting valuable mineral resources. Over-grinding not only significantly increases electricity and steel consumption costs in the milling process, but excessively fine slime can also interfere with subsequent beneficiation operations. Therefore, different minerals have an optimal grinding fineness range. For example, gold beneficiation typically requires grinding below 200 mesh, while the flotation of certain rare minerals may require even finer grinding.
Maximizing Liberation
The purpose of grinding is not only to crush the ore, but also to fully release valuable mineral particles from the gangue, forming independent particles. For example, sufficient liberation of copper sulfide in copper ore makes the flotation process more efficient, thereby improving the concentrate grade. Conversely, if liberation is incomplete, even if the ore is ground very finely, the target mineral cannot be economically recovered.
Energy Consumption Optimization
Simply pursuing the highest degree of liberation and the finest grinding particle size will significantly increase operating costs, ultimately compressing overall profit margins. Since grinding often accounts for more than 40% of the total energy consumption in mineral processing, finding a balance between high grinding efficiency and low operating costs is crucial to the profitability of the entire mine. By adapting a reasonable milling process and adjusting parameters such as the steel ball gradation and rotation speed of the mill, energy and steel consumption can be significantly reduced while ensuring grinding quality, and the overall operating cost of the milling process can be minimized as much as possible.
What Types of Milling Equipment Are Available?
(1) Ball Mill
Ball mills are currently the most widely used general-purpose grinding equipment in the industry. They rely on rolling steel balls inside the cylinder to impact and grind the ore, adapting to the medium-fine particle size (-0.074mm) grinding needs of various hardness ores. Wet grinding produces less dust pollution and is suitable for most metal ore beneficiation scenarios, such as gold, copper, lithium, chromium, manganese, and iron ore. Dry grinding is more suitable for processing materials that are sensitive to water, such as cement and kaolin, and can be flexibly selected as needed.
(2) Rod Mill
Rod mills use steel rods as the grinding media, suitable for the coarse grinding stage (1-5mm), reducing over-grinding. Their unique line contact grinding method results in more uniform product particle size and is often used as a pre-grinding device for ball mills, especially suitable for easily mud-forming ores such as gold and tungsten ore.
(3) SAG/AG Mill
Autogenous grinding mills (AG) rely on the mutual impact and grinding of the ore itself; semi-autogenous grinding mills (SAG) add a small amount of steel balls to assist grinding. Both have the ability to directly process large pieces of ore larger than 100mm, which can greatly simplify the crushing process and reduce the load on the crushing process. They are the mainstream grinding technology choice for large-scale concentrators with a capacity of thousands of tons or more.
4 Core Steps Of Milling Process In Mining
1. Crushing
The mined raw ore is first gradually crushed using a combination of coarse, medium, or fine crushing equipment, such as jaw crushers and cone crushers. Then, it is classified by a vibrating screen. Only ore with a particle size ≤25mm can enter the grinding equipment.
2. Milling
After the ore is fed into the ball mill, operating parameters must be matched according to its hardness and embedding characteristics. For example, for hard ore, the proportion of large-diameter steel balls should be increased, and the slurry concentration should be controlled at around 70%-75%. For grinding soft ore, the average diameter of the steel balls should be reduced, and the slurry concentration should be appropriately lowered. Parameter matching directly determines grinding efficiency and product quality, and is a core aspect of daily grinding process control.
3. Classification
The ground slurry is first fed into classification equipment. Spiral classifiers are suitable for coarse grinding scenarios, while hydrocyclones are more suitable for fine grinding scenarios. Slurry that meets the fineness requirements enters the next stage, while coarse particles that do not meet the requirements are returned to the mill for grinding, forming a closed-loop cycle. This process ensures uniform product particle size while reducing over-grinding, making it a core component of current mainstream closed-circuit grinding processes.
4. Mineral Processing
The slurry meeting the particle size requirements is pumped to gravity separation, flotation, leaching, and other processes via a slurry pump.
Conclusion
The milling process (grinding process) is a core step in mineral processing, lying between crushing and separation (such as flotation and magnetic separation), undertaking the crucial task of mineral liberation. It directly determines mineral recovery rate and overall economic benefits. JXSC Mine Machinery Factory‘s beneficiation process covers the milling needs of mines of different sizes and ore types. Whether it’s gold, copper, or iron ore, proper particle size control can liberate the target mineral while avoiding energy waste.
Selecting a mill requires comprehensive consideration of ore hardness, capacity, and energy consumption. For small and medium-sized concentrators and fine grinding scenarios, wear-resistant ball mills are preferred; for coarse milling scenarios and brittle ores, rod mills are recommended. Simultaneously, the mill’s design capacity must be matched, and the equipment purchase cost, long-term energy consumption, and maintenance costs must be comprehensively calculated to make your mineral processing solutions more efficient and profitable.