ALUMINA PRODUCTION

Alumina Production



Alumina Production

Introduction

Alumina is called crystalline alumina and it is the main raw material for aluminum. Aluminium is produced from alumina by electrolysis (Bayer, 1985). Alumina is also used in other industries (such as bleaching paper, the production of special grades of cement, zeolite-absorbing substances certain kind of molecules in the presence of other molecules, etc.). Additionally, sometimes in the cost-effective production of alumina include the production of rare metals in the aluminum ore related (such as gallium, vanadium, etc.). Alumina is produced from ore containing rock - bauxite. Bauxite are complex chemical and mineralogical composition (Harris & McLachlan, 1998). The main part of their useful and various modifications are hydroxide (hydroxide), aluminum (A l (OH) 3, AlO OH, etc.). The composition typically includes bauxite, iron oxides, silica, in a small amount - of sulfur, titanium, gallium, chromium, vanadium, etc., as well as calcium carbonate, magnesium, iron, organic compound (remnants of ancient plant and animal), etc.

History There are over seven thousand years ago, the potters of Persia manufactured earthen vessels with aluminum oxide (currently known as alumina), and thirty centuries more later, the Egyptians and Babylonians used another compound similar in their cosmetics and medicinal products. However, the actual existence and functionality of the aluminum still were unknown. The rumors were that aluminum was from collisions of atoms hydrogen during the formation of the solar system (Edwards & Frary, 1930).

Process for obtaining aluminum Bauxite to alumina is removed by means of the reduction process is transformed aluminum. The production is composed of a series of chemical reactions. Even bauxite is formed by a natural chemical process, from the infiltration of water decomposition in alkaline rocks. This ore can be found near the surface with an average thickness of 4.5 meters (Bayer, 1985). Its extraction is usually held in the open with the aid of backhoe loaders. Before starting bauxite mining, it is necessary to take care to remove the earth on the fertile fields along with the vegetation and book it for the future work rearrangement of terrain. This work, which happens after extraction, is very important for the preservation of the environment (Habashi, 1973). Once mined, bauxite is transported to the factory, where it arrives still in its natural state. There begins the first of many chemical reactions. The bauxite is crushed and added to a solution of caustic soda, which transforms it into folder. And heated under pressure receiving new amounts of caustic soda, this mass dissolves and forms a solution that passes through sedimentation and filtration processes. In this step, all impurities are eliminated and the remaining solution is ready for it is extracted alumina. This brochure covers the basics of the production of alumina from bauxite by the Bayer process and is intended for workers and technicians alumina industry, but may be useful for engineering personnel without chemical engineering training in the production of alumina. To facilitate the acquisition of specialized terminology alumina production (part of it is only used in the ...