Comminution is the reduction of
solid
Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structura ...
material
Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geolo ...
s from one average
particle size to a smaller average particle size, by
crushing,
grinding,
cutting
Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force.
Implements commonly used for cutting are the knife and saw, or in medicine and science the scalpel and ...
,
vibrating, or other processes.
In
geology
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ea ...
, it occurs naturally during
faulting in the upper part of the
Earth's crust
Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
.
In
industry, it is an important
unit operation in
mineral processing
In the field of extractive metallurgy, mineral processing, also known as ore dressing, is the process of separating commercially valuable minerals from their ores.
History
Before the advent of heavy machinery the raw ore was broken up using ...
,
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelai ...
s,
electronics
The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
, and other fields, accomplished with many types of
mill
Mill may refer to:
Science and technology
*
* Mill (grinding)
* Milling (machining)
* Millwork
* Textile manufacturing, Textile mill
* Steel mill, a factory for the manufacture of steel
* List of types of mill
* Mill, the arithmetic unit of the A ...
. In
dentistry
Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions ...
, it is the result of
mastication of food. In general medicine, it is one of the most traumatic forms of
bone fracture
A bone fracture (abbreviated FRX or Fx, Fx, or #) is a medical condition in which there is a partial or complete break in the continuity of any bone in the body. In more severe cases, the bone may be broken into several fragments, known as a '' ...
.
Within industrial uses, the purpose of comminution is to reduce the size and to increase the surface area of solids. It is also used to free useful materials from
matrix
Matrix most commonly refers to:
* ''The Matrix'' (franchise), an American media franchise
** '' The Matrix'', a 1999 science-fiction action film
** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...
materials in which they are embedded, and to concentrate minerals.
Energy requirements
The comminution of solid materials consumes energy, which is being used to break up the solid into smaller pieces. The comminution energy can be estimated by:
*
Rittinger's law, which assumes that the energy consumed is proportional to the newly generated surface area;
*
Kick's law, which related the energy to the sizes of the feed particles and the product particles;
*
Bond's law, which assumes that the total work useful in breakage is inversely proportional to the square root of the diameter of the product particles,
mplyingtheoretically that the work input varies as the length of the new cracks made in breakage.
[Bond, F.C. The third theory of comminution.Trans. AIME, vol. 193, 1952.
pp. 484–494.]
*
Holmes's law, which modifies Bond's law by substituting the square root with an exponent that depends on the material.
Forces
There are three forces which typically are used to effect the comminution of particles:
impact,
shear, and
compression.
Methods
There are several methods of comminution. Comminution of solid materials requires different types of
crushers and
mills depending on the feed properties such as hardness at various size ranges and application requirements such as throughput and maintenance. The most common machines for the comminution of coarse feed material (primary crushers) are the
jaw crusher (1m > P
80 > 100 mm),
cone crusher (P
80 > 20 mm) and
hammer crusher. Primary crusher product in intermediate feed particle size ranges (100mm > P80 > 20mm) can be ground in
autogenous (AG) or
semi-autogenous (SAG) mills depending on feed properties and application requirements. For comminution of finer particle size ranges (20mm > P
80 > 30 μm) machines like the ball mill, vertical roller mill, hammer mill, roller press or high compression roller mill, vibration mill, jet mill and others are used. For yet finer grind sizes (sometimes referred to as "ultrafine grinding"), specialist mills such as the
IsaMill
The IsaMill is an energy-efficient mineral industry grinding mill that was jointly developed in the 1990s by Mount Isa Mines Limited ("MIM", a subsidiary of MIM Holdings Limited and now part of the Glencore Xstrata group of companies) and Netzsch F ...
are used.
Trituration, for instance, is comminution (or substance breakdown) by rubbing. Trituration can further be described as levigation (trituration of a powder with a non-solvent liquid), or pulverization by intervention, which is trituration with a solvent that can be easily removed after the substance has been broken down.
See also
*
*
*
References
{{Extractive metallurgy
Industrial processes