Comminution

Comminution is one of the four main groups of mechanical processing and describes the movement of the particle size distribution (grains, drops, bubbles) into a range of finer particle sizes (The other groups are agglomeration, separation and mixing).

Comminution can be found in daily life in activities such as cutting, crushing, powder metallurgy, grinding and rasping in the preparation of different foods.

Industrial applications are found in biomass processing, preprocessing of cellulosic material to facilitate ethanol production, mineral processing (extraction of raw materials), chemical and ceramic industries, cement production, production of food, processing of waste.

In most of the cases the word comminution is used in referral to solids. Depending on the particle size it is distinguished between crushing (coarse feed material, bigger than appr. 50 to 100 mm) and grinding. Machines used for comminution are jaw crusher, cone and gyratory crushers, roller crusher, impact crusher, tube mills (e.g. ball mills or autogenous mills), vertical roller mills, and roller presses.

Mining
Comminution refers to a series of mineral processing techniques used in extractive metallurgy to reduce particle sizes of rocks and ores. Comminution processes are used to crush rocks into powder in preparation for subsequent processing methods which generally require finer particle sizes. A particle is liberated when the mineral of interest is physically free from any other minerals present (the gangue).

The machinery used for comminution can be divided into classes based on the size of the fragments they produce. Devices that produce coarse chunks are called crushers and those that produce finer particles are called grinders.

Waste management
Comminution is also used in the mechanical shredding or pulverizing of waste; a process found in solid and water waste treatment.

Medical
The term "comminution" is also used in medicine when referring to certain types of fracture. Usually, an impact will cause one fracture, thus breaking the bone into two pieces. But when the magnitude of the impact is such that it causes a bone to break in more than one place, it will produce several (i.e. more than two) fragments of bone. This is termed a "comminuted fracture".