Determination of structure and properties of ferriferous sand of aluminous production for search of ways for their processing
Keywords:ferriferous sands, production wastes, phase composition, pigments, cast iron.
The need to involve the production wastes – ferrous sands of the Pavlodar aluminum plant into the processing is associated not only with environmental protection, but also with the necessity to increase alumina production, complex waste utilization and the sintering process normalization. For high-iron bauxites effective using in the early stage of the process, the maximum separation of ferriferous sands from bauxite is carried out. The waste flow of ferriferous sands is 50 t/h, which are 10 % from general flow of feed bauxite. It contains up to 60 % of iron oxide and 17 % of aluminum oxide, which is irretrievably lost, reducing the overall extraction of alumina from bauxite. To involve production wastes in the processing, detailed physicochemical studies of the composition of ferriferous sand by methods as follows: X-ray, optical, thermal, phase and chemical analyzes of the fractions from +1 to -0.15 mm were carried out. It is shown that with the decrease of the fraction, the content of iron oxides (56.3-60.9 %) increases, and the content of aluminum oxide decreases (13.4-10.4 %). X-ray analysis of the averaged sample showed that the main iron-containing components in the ferriferous sands are, %: hematite 29.1; hetite 8.6; magnetite 6.19; siderite 8.14; as well as pyrite and andradite – by 2.58. Aluminum-containing phases are, %: gibbsite 11.6; serpentine 8.94 and kaolinite 7. The composition also includes concomitants, %: quartz 5.8; calcite 8.49 and gypsum 3.7. The performed thermal analysis also confirmed the presence of identified phases. The decomposition and oxidation temperatures of the components that occur with increasing temperature were determined. The obtained data on the phase composition and its transformations are necessary when developing methods for the ferriferous sands utilization. An analysis of the physicochemical data of ferriferous sands’ composition has shown that they can be considered as a potential raw material for pigments and cast iron production. The development of new technical solutions aimed at the involvement of production wastes – ferriferous sands in the process will increase the profitability of the existing alumina production by low-quality high-iron bauxite processing.