A kiln is a furnace that generates high temperatures in order to enable the material to be fired to undergo a thermally activated material conversion . It is constructed in different types and used in different areas.
A kiln differs from a kiln in that the primary purpose of the kiln is not the generation of heat, but the targeted thermal treatment of a material that is in the kiln: the material that is to be "fired". The firing process itself takes place continuously or discontinuously.
Some application examples:
- for the production of quick lime from limestone
- for the production of cement
- for the production of building bricks, bricks
- for the production of sand-lime bricks , clinker bricks , roof tiles, etc.
- for the production of materials, which in turn are used for lining furnaces ( fireclay , brick lining )
- for the production of porcelain (round oven), in the porcelain industry, was replaced by the tunnel oven in the 20th century
- for the production of ceramics , in the pottery (firing of the clay , " Schrühbrand ")
- for the production of glazes (glaze firing)
- for melting glass fusing
- for the production of enamel
- for the production of charcoal in a kiln
- for waste treatment ( waste incineration plant )
and many other uses.
A continuous firing process is maintained, the material to be fired runs through the kiln in a continuous flow. A rotary kiln burns according to this principle z. B. cement . A discontinuous firing process requires filling the furnace, heating up, possibly maintaining a defined firing temperature, cooling down and emptying of the firing chamber for each firing batch.
During the firing, the air factor can be used to set different atmospheres with reducing, neutral or oxidizing properties that specifically influence the firing material. Also inertgashaltige- , vacuum or hydrogen-containing atmospheres are utilized industrially.
In this respect, a kiln also differs from a melting furnace : a furnace that simply converts a material into the liquid phase without chemical conversion , but which, after cooling, becomes the original material. A reversible change in the aggregate state takes place here ( casting ). Kilns, on the other hand, operate irreversible processes: their result cannot be reversed at will.