China Nonferrous Metallurgy

In industry, molybdenum concentrate is generally treated by oxidation roasting-ammonia leaching process. Sintering often occurs in the process of molybdenum concentrate oxidation roasting in multi-hearth furnace, which causes the the furnace bed thickening and seriously affects the production. In view of this problem, this paper takes the thickening material at the bottom of the multi-hearth furnace bed of a company s as the research object, carries out detection of sample in vertical direction, and analyzes the phase composition and microstructure of the sample. The results show that the bottom layer is formed by impurity elements such as CaMoO₄, CaMoO₄ CuSO₄ and CaSO₄, as well as the phase composition of MoO₃ and MoO₂ the middle layer is mainly composed of MoO₃ and a small amount of Mo4O11, MoO₂ and CaSO₄; the top layer is mainly composed of MoO₃ and a very small amount of Mo₄O₁₁ and MoO₂. The analysis shows that a large number of impurity elements are enriched on the surface of the bottom material (SiO₂) at the initial stage of the bottom thickening material, forming the low melting point compound; as the production progresses, the low melting point compounds and molybdenum oxides are further deposited on the bottom layer to form the top layer of the bottom thickening material. With production going on, the thickening material at the bottom of the furnace is continuously deposited and thickened. By controlling the type and content of impurity elements in raw materials, roasting temperature, material stirring strength, roasting time, material thickness and other measures, the thickening speed of furnace bottom material can be reduced, the maintenance of multi-hearth furnace bed can be reduced, and the production cost can be saved.