Papers by Keyword: Gibbsite

Abstract: The characteristics of the Sierra Leone iron ore were studied at laboratory scale by chemical analysis, XRD, SEM-EDS and TG-DSC methods. The Sierra Leone iron ore was a kind of limonite, which was mainly consisted of hematite, goethite and gibbsite. The iron ore lost its crystal water at a fast speed ranging from 200°C to 400°C and the total content of the crystal water was about 8.2 wt.%. The initial melt formation temperature of the iron ore with CaO was stably kept at around 1209°C and the amount of liquid increased with the increasing of CaO content. Its melt formation temperature is higher than Australian limonite. The sintering pot test showed that the yield of sinter decreases from 78.37wt.% to 73.36wt.% and the drum index decreases from 60.5wt.% to 49.63wt.% when the blending ratio of Sierra Leone iron ore increases from 7wt.% to 27.3wt.%.

Abstract: In order to explore the energy saving measures in gibbsite crystallization process for alumina production by Bayer method, industrial experiment was carried out to investigate the solid dispersion in a slight agitation seed precipitation tank for gibbsite crystallization. The experimental results showed that little difference of solid concentration, only 48.19 g·l^-1 is found in the range from 5 meters depth to the tank bottom, which is the most zone of the tank, and there is a somewhat large difference in the top 5 meters zone near the surface that is about 149.66 g·l^-1. Therefore, under the condition of slight agitation, solid content would not concentrate to the tank bottom completely with the normal work flow. It is suggested that the work of production would not be interrupted in less agitation than before, and the electrical energy saving rate is about 34%. The effects of reduced agitation on the yield and the quality of gibbsite crystallization should be studied carefully in subsequent works.

Abstract: Phase structure and micromorphology of gibbsite after hydrothermal treated in different solvents were studied. Results showed that there was a relationship between micromorphology and phase structure of as-synthesized product. The cubic slice-like boehmite microstructure can be obtained in water. The 3D flowerlike boehmite microstructure can be obtained in isopropanol or sodium carbonate solution. The global ammonium aluminum carbonate hydroxide (AACH) architectures assembled by the lathes can be obtained in urea solvent. Gibbsite can transform to boehmite after 12h hydrothermal treatment in water. In isopropanol or sodium carbonate solution, this time decreased to 6h. In urea solution, Aluminum hydroxide turned from gibbsite to the mixture of boehmite, gibbsite and AACH. Finally, AACH is synthesized. This procedure needs 24h.