The manufacturing technological process of alumina
From;    Author:Stand originally
From ore extraction alumina has a variety of methods, for example: Agglomeration of? of a kind of reed of  of ā of Zhan Dai of doubt of  of thorium of ⒓ of ā of  of a kind of reed combines a law to wait. The law that do obeisance to ear is the main method that produces alumina all the time, its crop occupies the 95 % left and right sides of total output of whole world alumina about. Since 70 time, already had greater progress to the research of acerbity law, but have not apply on industry.

Do obeisance to ear law

Department Austria does obeisance to ear (K.J.Bayer) invented 1888. Its principle is to use caustic soda (NaOH) solution adds Wen Rong to give the alumina in bauxite, receive solution of aluminous acerbity natrium. Solution and residual (bare mud) after depart, drop temperature, join hydroted alumina to make brilliant plant, classics is long agitate, aluminous acerbity natrium decomposes separate out hydroted alumina, abluent, and in 950 ~ 1200 ℃ temperature issues to calcine, get alumina finished product. The solution after separate out hydroted alumina calls mother liquor, evaporate the loop after condensing is used.

The brief chemistry of the law that do obeisance to ear reacts as follows:
    
Because 3 water aluminous stone, one water is soft aluminous Shi Heyi the crystallization construction of water duralumin stone is different, they have very big difference in the deliquescent function in caustic soda solution, want to offer different dissolve to give a condition so, basically be different dissolve give temperature. 3 water aluminous stone bauxite can be below 140 ℃ of 125 ~ dissolve goes out, stone of one water duralumin bauxite should be in 260 ℃ of 240 ~ add lime (7 % of 3 ~ ) the dissolve below the condition goes out.

Contemporary the main progress of the law that do obeisance to ear depends on: Of ① equipment large change and operate continuously; ② produces the automation of the process; ③ saves energy, high-pressured aggrandizement dissolve goes out and shed voice to change roast for example; Alumina of ④ birth arenaceous certificate electroanalysises with satisfying aluminium and flue gas works the need that type purifies. The technological process of the law that do obeisance to ear sees a picture 1.
    
The advantage of the law that do obeisance to ear basically is flow province of simple, investment and specific power consumption are inferior, lowest person the specific power consumption of every tons of alumina only 106 kilocalorie of 3 × are controlled, alkaline bad news is controlled for 100 kilograms commonly (with Na2CO3 plan) .

The economic result that the law that do obeisance to ear produces decides the quality at bauxite, basically be the SiO2 content in ore, compare with the aluminous silicon of ore normally, namely the weight of the Al2O3 in ore and SiO2 content expresses than coming. In because doing obeisance to the dissolve of ear law,giving a course, stone of natrium of SiO2 change set prescription natrium of hydration aluminous silicon acid (NH2O) of · of 1.7SiO2 of · of Na2O · Al2O3, eduction of mud of be accompanying bare. Every kilograms of SiO2 in ore should cause 1 kilogram of Al2O3 and 0.8 kilograms of losses of NaOH about. The aluminous silicon of bauxite is lower than jumping over, the economic effect of the law that do obeisance to ear is poorer. Till 70 time later period, the aluminous silicon that is in the bauxite of manage compares place of the law that do obeisance to ear to all be more than 7 ~ 8. As a result of high grade drop off of resource of 3 water aluminous stone bauxite, how to use the issue such as the natural resources of low grade aluminous ore of other type and energy-saving new technology, already was the important way of research, development.
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