Muffle furnace
A muffle furnace is a furnace in which the heat source is separated from the firing chamber by a heat-resistant insert - a muffle. The muffle usually consists of fireclay and can have built-in steel components.
Areas of application
Muffles are used in laboratories to protect the feedstock from flames or direct Heizelementstrahlung or to the electric heating elements before gases to protect, run out of the feedstock. Muffle furnaces are used for ashing and annealing as well as for the thermal treatment of workpieces (e.g. hardening of steel, ceramic test firings or coking, etc.). Muffle furnaces are used for various gravimetric processes in chemical analysis in order to bring small quantities of a substance into the weighing mold and to prevent foreign entry.
In soil science and geomorphology , muffle furnaces are used to determine the organic matter and carbon content in soils by burning up. Temperatures around 430 ° C are required for this.
The combustion chamber of a crematorium (for details see also cremation ) is also called a muffle furnace. It is lined with fireclay , which was heated to a temperature of around 900 ° C before cremation. The first phase of cremation (burning of the coffin) takes place exclusively with the heat stored in this way; no additional energy is supplied by gas burners during this cremation phase. An optimal and environmentally friendly cremation is achieved through a balanced relationship between temperature and the atmospheric oxygen supplied by a fan. These parameters are optimally controlled by a computer via sensors in the muffle furnace. During the cremation, temperatures of up to 1000 ° C can arise, also due to the cremation of the coffin.
Since the 18th century, a furnace specially designed for the color firing of ceramic overglaze paints has also been referred to as a muffle furnace or muffle , in which the combustion gases ("smoke") and the ashes from the combustion chamber cannot come into contact with the ceramic , but outside , along the sealed walls of a separate incendiary chamber and finally through a fume cupboard. This chamber is heated through the walls to up to 800 ° C, so that the onglaze colors - also called muffle colors - sink into the glaze of the ceramic. A separate hood on the top allows the vapors of the dyes and solvents to escape from this chamber.
Zinc muffle furnace
As early as the middle of the 19th century, special muffle furnaces with horizontal muffles were used to extract zinc in so-called zinc smelters .
See also
literature
- Bruno Kerl: Th. Bodemann's instructions for the mining and smelting art of tasting. Second edition, Verlag der Grossesche Buchhandlung, Clausthal 1857 ( online in the Google book search)
Web links
Individual evidence
- ↑ Grouch in Duden
- ^ S. Ebel and HJ Roth (editors): Lexikon der Pharmazie , Georg Thieme Verlag, 1987, p. 449, ISBN 3-13-672201-9 .
- ^ Walter Wittenberger: Chemische Laboratoriumstechnik , Springer-Verlag, Vienna, New York, 7th edition, 1973, pp. 149–150, ISBN 3-211-81116-8 .
- Jumpers , H. (1977): Field and laboratory methods of geomorphology. Berlin.