The multibore furnace is generally used for molybdenum oxide roasting. Factories have begun to adopt them. Features include: large production capacity, mechanical mixing of materials, good desulfurization effect, high-quality products, high recovery rate, products can meet the requirements of industrial and molybdenum processing. At present, about 96% of all molybdenum used in the factory must be first converted into industrial molybdenum oxide through roasting before further extraction of soluble molybdenum salt.The majority (about 83 %) of molybdenum or its alloys are used in the steel and metallurgical industry.
However, in the process of molybdenum calcining, the phenomenon of dense and hard lumping often occurs. Or the product is firmly stuck to the bottom of the furnace. Sintering on molybdenite oxidation roasting will bring a lot of adverse effects.
Due to sintering, part of the bottom of the molybdenite cannot be completely oxidized. Incomplete oxidation can increase the sulfur content of molybdenum calcine and decrease the product quality. Molybdenum products used in smelting ferromolybdenum or directly used in alloying steelmaking have high requirements for sulfur (generally no more than 0.07 %). Sulfur is a harmful element that affects the mechanical properties of steel.
Moreover, if the sintering phenomenon is dangerous, it will cause significant damage to the rake tooth and rake arm of the multi-chamber furnace, or even create dead heater.This kind of problem will significantly reduce the service life of the multi-chamber furnace and reduce production efficiency, thus affecting the economic benefits.
On the premise of relatively stable quality of molybdenite, many factors are affecting the sintering of molybdenite, such as roasting temperature, impurity species, and impurity solubility, material layer thickness, material mixing speed, roasting time, air pressure and velocity in the furnace, etc. But roasting temperature, impurity type, and solubility are the main factors affecting molybdenite sintering. For this factor, the specific research on molybdenite sintering at home and abroad is few.
Therefore, the sintering phenomenon of molybdenite in the process of oxidizing roasting was studied by using the actual molybdenite under the conditions of different influencing factors. This is very important for how to control the parameters, especially the temperature and impurities, and to ensure the normal operation of equipment and product quality.
(1) the type, content and reaction temperature of additives have an important impact on the occurrence of agglomeration. To reduce the molybdenite roasting process agglomeration phenomenon, an effective method is to reduce the content of impurity elements, especially Mg, Ca, Fe, Pb, Cu, and k. At the same time, reduce the roasting temperature is a good choice.
(2) during roasting, agglomeration occurs due to the formation of low melting point eutectic of MoO3 and some molybdate and local temperature rise.
(3) MgO and CaO have strong sulfur fixation effects. Therefore, to reduce the content of sulfur in the roasted product, it is necessary to control the amount of impurity elements Mg and Ca in molybdenite.
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