Clays calcination process

Aloton Also called Buchner. A process proposed for extracting aluminum from clay. Calcined clay is leached with ammonium hydrogen sulfate solution under pressure, and ammonium alum is crystallized from the liquor. Invented by M. Buchner in Hanover-Kleefeld in 1921 piloted in Germany in the 1920s and in Oregon in 1944. It was never commercialized, but provided the basis for the Nuvalon process which was. 

Aloton Also called Buchner. A process proposed for extracting aluminum from clay. Calcined clay is leached with ammonium hydrogen sulfate solution under pressure, and ammonium alum is... 

PILC are prepared by controlled hydrolysis reactions which can be carried out in solution or in the interlamellar space of the clay (the former allows better control of the nature of the polyoxocations). In addition to the different parameters already mentioned, the calcination process also plays a key role. Three general cases may occur (i) the polyoxocations exit from the clay (no pillaring), (ii) they degrade in situ giving rise to layers of aluminum hydroxide (thick ca. 

The TPD spectra show an increase of the acidity due to the intercalation of Zr, except when the "ex-situ polymerisation" process is run at pH 3.9. In this latter case, the clay calcined either at 400 or 600 C presents almost the same total acidity as the Na-montmorillonite, even if the Zr02 content of the clay is very high. Different hypothesis may explain the increase of acidity of the three other samples. This may be due either to the presence of the pillars, to the accessibility of the internal surface, or to the junction between the pillars and the silica layers. Without additional experiments the comparison of the acidity and acid strength of mixed oxides, studied by Shibata et al. (14) with this system supports the last hypothesis. 

Both the Toth and Alcoa processes provide aluminum chloride for subsequent reduction to aluminum. Pilot-plant tests of these processes have shown difficulties exist in producing aluminum chloride of the purity needed. In the Toth process for the production of aluminum chloride, kaolin [1332-58-7] clay is used as the source of alumina (5). The clay is mixed with sulfur and carbon, and the mixture is ground together, pelletized, and calcined at 700°C. The calcined mixture is chlorinated at 800°C and gaseous aluminum chloride is evolved. The clay used contains considerable amounts of silica, titania, and iron oxides, which chlorinate and must be separated. Silicon tetrachloride and titanium tetrachloride are separated by distillation. Resublimation of aluminum chloride is requited to reduce contamination from iron chloride. 

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). 

Reynolds Metal A process for extracting aluminum from clay by leaching with nitric acid. An essential feature is the pelletizing of the clay by calcination with kaolin in order to pro-... 

Seailles-Dyckerhoff A process for extracting aluminum from clays and other aluminous minerals rich in silica. The ore is calcined with limestone in a rotary kiln. The product is leached with aqueous sodium carbonate, yielding sodium aluminate solution, from which alumina is precipitated by carbon dioxide. Invented by J. C. Seailles and W. R. G. Dyckerhoff in 1938 piloted in Tennessee in 1942, South Carolina in 1945, and Germany during World War II. See also Pedersen. 

Walthal An obsolete process for obtaining alumina from clay. The clay was roasted, extracted with sulfuric acid, and the aluminum sulfate dried and calcined. 

Willhoft A proposed process for making aluminum chloride from the solid waste from paper mills. The waste is mainly a mixture of clay with cellulose. It is dried and calcined in an inert atmosphere, giving a mixture of clay and caibon which chlorinates readily. Conceived by E. M. A. Willhoft and briefly examined by the Research Association for the Paper and Board, Printing and Packaging Industries (PIRA) in England in 1977, but not piloted. 

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