Flowsheets Bayer process

In the flowsheet of alumina production by the Bayer process, aluminum is precipitated from an aqueous solution as aluminum hydroxide. The hydroxide is dried in rotary furnaces. In recent times, fluidized-bed reactors have been deployed which yield practically nonhygroscopic alumina. The dissociation of aluminum hydroxide occurs in steps,... 

Figure 6.25 Flowsheets for Al extraction stream 1 Bayer process, 2 Alcoa process, 3 Toth process, 4 Alcan process.

The Alcoa (Aluminum Company of America) process involves the electrolysis of aluminum chloride which is carried out in a molten bath of the composition 50% sodium chloride, 45% lithium chloride and 5% aluminum chloride, maintained at 700 °C. The Bayer process, which involves the production of pure alumina by the dissolution of bauxite with caustic soda and which has been described in the chapter on hydrometallurgy, must be taken into account while presenting a complete picture of the aluminum extraction flowsheet. It... 

Ores containing essentially pure gibbsite may be digested at temperatures of ]50 C while boehmilic ores require temperatures in rbe range of 230-250 C. These temperatures reflect the differences in the solubilities of the various hydrated aluminum minerals, Figure 9.2-4 illustrates a typical Bayer process flowsheet. 

The alkali process uses sodium hydroxide and is well known as Bayer s process. It involves relatively simple inorganic and physical chemistry and the entire flowsheet can be divided into caustic digestion, clarification, precipitation and calcination. Although mineral assemblage in bauxites is extensive, processing conditions are primarily influenced by the relative proportions of alumina minerals (gibbsite and boehmite), the iron minerals (goethite and hematite), and the silica minerals (quartz and clays-usually as kaolinite). 

Bayer, B., Marquardt, W., Weidenhaupt, K., Jarke, M. A flowsheet centered architecture for conceptual design. In Gani, R., Jprgensen, S.B. (eds.) Proceedings of the European Symposium on Computer Aided Process Engineering - ESCAPE 11, pp. 345-350. Elsevier, Amsterdam (2001)... 

Whereas the AES approach considers the AspenPlus model as the core information, from which other model representations are derived, we consider the flowsheet of a process as the relevant piece of information that is used as a starting point for model development (Bayer et al., 2001b). This permits an extensible architecture which can... 

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