JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II MINERAL PROCESSING Previous Question Paper (October - 2020 - R18)

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

The key roles include:

• Liberation: Reducing the ore size to physically detach valuable mineral grains from the host rock matrix.
• Concentration: Increasing the grade of the desired metal by removing gangue through physical or physicochemical methods like gravity, magnetic, electrostatic, or flotation separation.
• Waste Management: Reducing the volume of material that must be processed in energy-intensive chemical or thermal stages, thereby minimizing environmental impact and operational costs.
• Feed Preparation: Ensuring the physical and chemical characteristics of the concentrate meet the strict requirements of smelting, leaching, or refining processes.

By upgrading the ore, mineral processing significantly improves the efficiency of extraction, reduces energy consumption in furnaces, and enables the economic exploitation of low-grade deposits that would otherwise be considered waste.

Size reduction, or comminution, is influenced by several intrinsic ore properties and operational parameters:

• Hardness and Toughness: The resistance of the mineral to breakage, often measured by the Bond Work Index, directly determines the energy required for grinding.
• Ore Texture and Grain Size: The degree of mineral dissemination dictates the required product size for liberation. Finer grain sizes necessitate more intensive grinding.
• Moisture Content: High moisture levels can cause material to stick to liners or clog screens, significantly reducing the throughput and efficiency of crushers and mills.
• Feed Size Distribution: The initial size range of the ore affects the selection of equipment (e.g., primary vs. secondary crushers) and the overall reduction ratio.
• Equipment Characteristics: The mechanical design, speed, and media type (balls, rods, or autogenous) of the grinding mill influence the breakage mechanism, whether by impact, attrition, or abrasion.
• Circulating Load: Maintaining an optimal circulating load in closed-circuit grinding ensures that only material above the target size is returned for further reduction, preventing over-grinding and improving efficiency.