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Magnesite processing in the metallurgical plant


The raw magnesite is mined selectively according to customer requirements and temporarily stored in the plant in Oberdorf. By different treatment processes and specific combustion process, the individual qualities (caustic) are produced.

So far, the calcination of magnesite has been provided in a fluidized bed furnace at about 970°C (=soft burned caustic). Through this burning process the produced magnesia (MgO) has a very high reactivity.

In the combustion process, the magnesite bodies are destroyed by elimination of the carbon dioxide and magnesium oxide in fine form is separated. The burned magnesium oxide is deposited over a primary cyclone and receives physical post-treatment for the requested quality. By means of pneumatic conveyance, the caustic calcined magnesite reaches one of 30 intermediate silos (each 80 tons). Depending on the quality of the desired end product and the respective customer requirement, the material from the intermediate silos is mixed and ground individually. The products are delivered in bulk or big bags (50 or 25 kg bags). The Quality control is parallel to the entire production process, starting with the matte validation in mining prior to the recovery after extraction of the coarse metal, after burning, after mixing and/or milling and after packaging.

The investigations are performed by the own, well-equipped laboratory with the best trained staff. The results are each documented and retain samples are formed.

In the newly constructed multiple hearth furnace the calcinations of magnesite takes place in a similar process. The baking process also takes place about 790°C. The rough stone is abandoned, frosted and burned in 7 floors with a total of 13 burners. Both, the combustion temperature and the burning rate can be controlled individually, whereby special chemical and physical properties of magnesite can be controlled. About 75% of the produced caustic magnesite in the multiple hearth furnace is a granular (granular) product. This is currently available in bulk or big bags.

25% of the causter produced in the multiple hearth furnace have a very fine (but not powdery) grain size. This fine, in the multiple hearth furnace roasted causter has, due to the selection during the baking, significantly higher MgO values (up to 93% MgO).

The feeding of the rough stones in the multiple hearth furnace is made by 2 separate matte silos. This allows a targeted, selective matte feeding. The temporary storage of the causter obtained in the multiple hearth furnace is in 2 newly built silos.

These in turn are connected by a pneumatic conveyor with the existing silo building, which has 30 silos of 80 tons each. From there also the granular material, produced in the multiple hearth furnace, can be aligned and mixed with the dust-like material from the fluidized bed furnace.

An additional improvement of the final product quality is the separation of the material. This increases the MgO content and a reduction of FE203 is obtained.

The plan is a highly efficient magnetic separation, both in terms of the matte and in terms of the caustic in the level of the intermediate (before mixing).


For more information, click here: quality assurance and management