VERFAHREN ZUR HERSTELLUNG VON REINEM ALUMINIUMOXID

摘要

In the process for the preparation of pure aluminum oxide by the steps of hydrochloric acid decomposition of mechanically or thermally activated clay or alumina containing minerals, separating the insoluble residue, removing the iron from the solution, crystallizing the aluminum chloride in the iron-free solution, thermally decomposing the crystallizate to aluminum oxide and recovering the hydrochloric acid from the decomposition gases, the improvement comprising effecting the process by the steps of mechanically pretreating the clay, drying the pretreated clay, thermally or mechanically activating the clay, subjecting the activated clay to circulating leaching, separating the leached material into an SiO2 containing residue and an AlCl3 solution, extracting the AlCl3 solution to an evaporating crystallization and thermally decomposing the crystals to produce alpha -Al2O3. All of the stages are interrelated one to the other for maximum recovery of byproducts, heat, acid and the like. The alpha -Al2O3 is directly produced in a form of high purity suitable for most applications.