JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III MINERAL PROCESSING Previous Question Paper (August/September - 2021 - R18)

Mineral processing serves as the critical bridge between raw ore extraction and metallurgical recovery. Its primary scope involves the physical separation of valuable minerals from gangue (waste) material to produce a concentrated product suitable for downstream processing.

Key aspects of its scope include:

• Upgrading Ore Grade: Most ores are low-grade; processing increases the concentration of the target metal, significantly reducing the volume of material that must be transported and treated in expensive chemical or thermal extraction stages.
• Removal of Deleterious Impurities: It removes elements that interfere with smelting or refining processes, such as sulfur, arsenic, or phosphorus, which can cause environmental issues or reduce metal quality.
• Economic Viability: By discarding waste early in the flow sheet, it minimizes energy consumption and reagent usage in subsequent hydrometallurgical or pyrometallurgical operations.
• Resource Conservation: It enables the exploitation of complex, low-grade, or fine-grained deposits that would otherwise be uneconomical to process.

Comminution is the collective term for the reduction of solid materials from a larger particle size to a smaller one through mechanical forces such as crushing, grinding, or milling. It is the fundamental first step in mineral processing, essential for liberating valuable mineral grains from the host rock matrix.

The process is typically divided into two main stages:

• Crushing: Performed on dry ore using compressive forces in equipment like jaw crushers, gyratory crushers, or cone crushers. It reduces run-of-mine ore to a manageable size (typically down to 10-20 mm).
• Grinding: Performed either dry or wet using impact and attrition forces in tumbling mills (ball mills, rod mills, or SAG mills). This stage reduces the particles to the fine sizes required for liberation, often in the range of 10 to 100 micrometers.

Comminution is the most energy-intensive stage in mineral processing, often accounting for a significant portion of a plant's total operating costs. Efficiency is measured by the degree of liberation achieved relative to the energy input, often guided by Bond's Law of Comminution, which relates energy consumption to the change in particle size.