The apparatus for the unit concentration process comprises an evaporator and a heat exchanger. The evaporator can be a flash evaporator. The material of the evaporator can be made of an alkali resistant metal such as iron, iron alloys (Fe-Cralloy, Fe-Cr-N alloy, etc.), nickel and nickel alloys (Ni-Cu alloy, Ni-Fe alloy, Ni-Cr alloy etc.)....

Unitary process describes a simple transformation involving heat, mass and momentum transference, or any combination of the same, that can be separated from the whole.
In this case the concentration of the ore is made up of individual unitary processes.
Unitary processes to be found when concentrating are for example; flotation, cyclones, water extractors, heat transference, phase transformers, sludge extractors, blowers, sieves, driers, evaporators, vaacum generators, etc.

The correct expression would be "Unitary processes used in the concentration stage of ore treatment" however this is too long and the shorter phrase is the better option.