Mineral Processing

In minerals processing, unit operations must prepare and classify ores before separating the valuable materials. These processes form valuable minerals.

Necessary unit operations include:

Comminution / Size Reduction

To achieve the goal of recovering valuable materials, the raw ore must be reduced to a reasonable size before separation. This process is called ‘comminution’ or ‘size reduction.’

Comminution may be carried out on either dry materials or slurries. Most mineral processing operations are conducted with water as the medium; this is called wet processing against dry processing.

Crushing, grinding, milling, and vibration (feeding) are examples of comminution processes.

Sizing / Separation

Sizing is the general term for separating minerals according to their size.

The separation methods are based on the variations among the physical properties of different minerals, such as shape, susceptibility to size reduction, specific gravity, surface chemical property, and electromagnetic exposure.

The most straightforward mineral sizing process is screening or passing the particles to be sized through a screen or multiple screens.

Classification of particles by size comprises an essential operation in mineral processing, and it can be accomplished either by screening through sieves or applying forces by the medium, gas, or water.

Concentration

Mineral processing concentration means the increase of the percentage of the valuable mineral in the concentrate. Concentration includes processes that involve the separation of minerals without a change in their structure, chemical composition, or state of aggregation. The results of mineral concentration are two main products: concentrate and tailings.

Dewatering

For economic reasons, dewatering/drying is essential in mineral processing. Removal of the moisture content enables easy and cost-effective handling and transportation of minerals. The water removed during dewatering can be recycled through a mineral processing plant. The main processes used in dewatering/drying include dewatering screens, filtering, sedimentation, and thermal drying.

In all of these operations, the most important considerations are the processes’ economics, which is dictated by the grade and recovery of the final product. To achieve the goal of extracting minerals from ores in their purest form for mineral processing engineers, only the best mineral processing technology suffice. An essential first step in both comminution and sizing operations in mineral processing is particle size analysis.

In the particle size reduction (comminution) process, crushers (jaw crushers, gyratory crushers, cone crushers) and grinders (rod mills, ball mills, impact mills, attrition mills) are primarily used systems.

In the sizing (separation) process, necessary equipment includes:

Screening equipment:

• Grizzly screen
• Bar screen
• Wedge wire screen
• Banana screen
• Vibrating screen
• Multi-deck screens
• Fine screen
• Flip flop screen
• Wire mesh screen

Classification equipment:

• Sorting systems
• Cyclones
• Rotating trommels
• Classifiers
• Scrubbers

In the mineral concentration process, designed to produce a concentrate consisting predominantly of valuable minerals, the following mineral processing equipment is primarily used:

Separation:

• Gravity separators
• Elutriators
• Magnetic separators
• Flotation
• Leaching

Dewatering

• For the removal of the moisture contents from minerals the following equipment is primarily used:
• Presses
• Dewatering screens
• Filters
• Centrifuges
• Dryers