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 structural ...
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
Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles ('' bubbles''). The notion of particle size applies to particles in colloids, in ecology, in ...
to a smaller average particle size, by
crushing,
grinding
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
,
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 wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
,
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 geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
in the upper part of the
Earth's crust.
In
industry
Industry may refer to:
Economics
* Industry (economics), a generally categorized branch of economic activity
* Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery
* The wider industrial sector ...
, it is an important
unit operation
In chemical engineering and related fields, a unit operation is a basic step in a process. Unit operations involve a physical change or chemical transformation such as separation, crystallization, evaporation, filtration, polymerization, isomeriza ...
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, porcelain ...
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 mill
* Steel mill, a factory for the manufacture of steel
* List of types of mill
* Mill, the arithmetic unit of the Analytical Engine early ...
. In
dentistry, it is the result of
mastication of food. In general medicine, it is one of the most traumatic forms of
bone fracture.
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 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
Compression may refer to:
Physical science
*Compression (physics), size reduction due to forces
*Compression member, a structural element such as a column
*Compressibility, susceptibility to compression
* Gas compression
*Compression ratio, of a ...
.
Methods
There are several methods of comminution. Comminution of solid materials requires different types of
crushers and
mills
Mills is the plural form of mill, but may also refer to:
As a name
* Mills (surname), a common family name of English or Gaelic origin
* Mills (given name)
*Mills, a fictional British secret agent in a trilogy by writer Manning O'Brine
Places Uni ...
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 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