Calcined, Dead Burned & Fused
Environmental, Metal Working, Specialities
Magnesium oxide (MgO) varies in reactivity according to the temperature at which it has been produced.
- Natural magnesite is the raw material used, most commonly for industrial grades of magnesium oxide.
- Magnesite (MgC03) can be calcined to produce highly reactive magnesium oxide which is generally known as caustic calcined magnesite (CCM).
- At higher temperatures the resultant magnesium oxide is considerably less reactive and colloquially known as dead burned magnesite (DBM).
- Electric arc furnaces producing very high temperatures to melt the magnesite create fused magnesite or fused magnesia.
- Another source of magnesium carbonate is sea water brine, from which the magnesium salts are precipitated and then calcined to produce light magnesium oxide.
Calcined magnesite is a cost effective source of chemical grade magnesium oxide – used as an alkali for acid neutralisation in the process and subsequent effluent treatment. A range of purities are available along with a choice of particle size. 90% magnesium oxide is the most cost effective grade, whereas 94% magnesium oxide introduces the lowest unwanted non reactives. Fine particle sizes are more reactive than coarse powder but can be found less easy to handle during processing.
Dead burned magnesite is widely used as a basic refractory material. It is produced in rotary kilns and has purities of 90-95% MgO. It is widely used for gunning/ramming mass for tundish linings and for fettling purposes. Dead burned magnesite can be supplied in lump for users to crush and grade, or in ready-sized form. Common sizings are 5-3mm, 3-1mm, -1mm, -0.5mm and DIN 70.
Fused magnesia is prepared in electric arc furnaces by fusing calcined magnesite. Fused magnesia is a high performance basic refractory becoming more widely used for its durability under extreme conditions.
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