Ceramic Manufacturing Industry - Best Available Techniques
This is a reference document on Best Available Techniques in the Ceramic Manufacturing Industry.
Generally the term ‘ceramics’ (ceramic products) is used for inorganic materials (with possibly
some organic content), made up of non-metallic compounds and made permanent by a firing
process. In addition to clay based materials, today ceramics include a multitude of products with
a small fraction of clay or none at all. Ceramics can be glazed or unglazed, porous or vitrified.
Firing of ceramic bodies induces time-temperature transformation of the constituent minerals,
usually into a mixture of new minerals and glassy phases. Characteristic properties of ceramic
products include high strength, wear resistance, long service life, chemical inertness and nontoxicity,
resistance to heat and fire, (usually) electrical resistance and sometimes also a specific porosity.
APPLIED PROCESSES AND TECHNIQUES
The manufacture of ceramic products takes place in different types of kilns, with a wide range
of raw materials and in numerous shapes, sizes and colours. The general process of
manufacturing ceramic products, however, is rather uniform, besides the fact that for the
manufacture of wall and floor tiles, household ceramics, sanitaryware and technical ceramics
often a multiple stage firing process is used.
In general, raw materials are mixed and cast, pressed or extruded into shape. Water is regularly
used for a thorough mixing and shaping. This water is evaporated in dryers and the products are
either placed by hand in the kiln – especially in the case of periodically operated shuttle kilns –
or placed onto carriages that are transferred through continuously operated tunnel or roller
hearth kilns. For the manufacture of expanded clay aggregates, rotary kilns are used.
During firing a very accurate temperature gradient is necessary to ensure that the products
obtain the right treatment. Afterwards controlled cooling is necessary, so that the products
release their heat gradually and preserve their ceramic structure. Then the products are packaged
and stored for delivery.
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