Classification of Mineral Processing as Unit Operations or Unit Processes
In the classical concept, mineral processing consists entirely of unit operations because it
involves only the physical liberation and separation of minerals without chemical reaction. Mineral
processing focuses on the physical treatment of ores to liberate and separate valuable minerals
from gangue; therefore, processes such as crushing and grinding, screening and classification,
gravity concentration, magnetic and electrostatic separation, flotation (surface property
separation), thickening, filtration, and dewatering are all classified under unit operations.
According to Meloy, T. P., in the study entitled “Analysis and Optimization of Mineral
Processing and Coal-Cleaning Circuits — Circuit Analysis,” mineral processing circuits are
composed of distinct unit operations, including crushing, grinding, sizing (separation), and
physical separation methods such as heavy media separation and flotation. The study analyzes how
these physical steps function within a processing circuit and explains how each unit operation
influences the overall performance, efficiency, and separation outcomes of mineral feeds.
Similarly, Wills, B. A., in “Comminution in the Minerals Industry: An Overview,”
emphasizes that comminution, which includes crushing and grinding, is the most energy-intensive
and fundamental unit operation in mineral processing. The article highlights that comminution is
essential for the liberation of valuable minerals from gangue and serves as the backbone of mineral
beneficiation circuits, reinforcing the importance of physical processing steps in achieving
effective mineral separation.
While mineral processing is traditionally classified under unit operations, a process may
be considered a unit process when it involves a chemical reaction that results in a change in
chemical composition, molecular structure, or chemical phase of the material. Unit processes are
characterized by reactions such as oxidation, reduction, dissolution, precipitation, and thermal
decomposition, where new chemical substances are formed. Examples include leaching, roasting,
calcination, bioleaching, and chemical precipitation, which are commonly associated with
extractive metallurgy rather than classical mineral processing. In contrast, operations such as
crushing, grinding, flotation, magnetic separation, thickening, and filtration remain classified as
unit operations because they only alter the physical characteristics and distribution of particles.
Therefore, mineral processing is considered a unit process only when chemical reactions are
intentionally employed to transform or extract minerals.