RESEARCH OF ALUMINA MANUFACTURING FROM CLAY MATERIALS
Aluminum oxide or alumina, is basic initial material for the production of aluminum. It’s also used in other kinds of manufacturing: ceramics, different sorts of glass, corrosion-resistant coats and other.
Aluminum has high chemical activity and that’s why in nature meets only in the tied-up state in the form of different minerals and mountain rocks. About 250 different minerals contain aluminum. However bauxite(approximately 95% of alumina world production) serves as basic raw material for the production of alumina. It is explained by the fact that aluminum oxide content in bauxite is higher and silicate is lower than in other aluminum ores. Raw supplies are limited in the world, and in Ukraine there are no industrial supplies of these minerals.
A lot of types of unbauxite raw materials advantageously differ from bauxite because they contain other useful elements, such as sodium and potassium in nefelins, alkaline metals and sulphur in alumstone and other. That is why industrial processing of these ores to produce alumina is fully expedient and advantageous in the case of complex processing using not only aluminum oxide, but also other components. For example, in the production of alumina from clay raw material it is possible to get soda, potash and cement. It’s a very actual question for Donetsk region, which is rich in clay deposits with high content of A1203, e.g. special clay from Chasov-Yar which contains 35% of A1203.
Discovered in 1899 by Bayer, a hydrochemic method of alumina production is a basic one in world aluminum industry until nowadays. This method is effective and simple, but it can be used only, with high-quality, lowsiliconic bauxites with small content of admixtures. The worlds supplies of such materials are limited.
A method of caking, which has widely been spead is more expensive, but more universal, because one may use low quality nefelins, alumstones, clay raw material, kaolinits, coal ash, aluminosilicatic rocks which supplies are practically inexhaustible. That is why processing of this raw material by the method of caking to produse alumina in spite of low countent of aluminum oxide is fully expedient and advantageous because besides alumina useful by-products appear to be available.
An addition classic methods of alumina production there are other technological schemes of alumina production: parallel and consistently combined methods of Bayer-caking for lowsiliconic and highsiliconic bauxites processing, alkaline restoration method for alumstone processing.
In this work it has been the investigated possibility to produce by alumina by clay material caking, deposite of which in the Donetsk region are large enough.
Chasov-Yar special clay was taken as an object of investigation, which has the following chemical composition: 35% A1203, 4% Na20,K2O, 50% SiO2, 0,5% Fe203 and 1% ÑaÎ (the masses. %).
In laboratory terms there have been made mixtures birth clay as a fase for caking with carbonate rocks (chalk). The chalk is entered a charge in according to molar correlation CaO:SiO2, which equals to 2,0 ± 0,03, to produce littlesoluble calcium ortosilicate (2CaO•SiO2).
Original materials were preliminary crushed, measured out and mixed up carefully. Charge was caked at 1200 °C with endurance during 30 minutes and in a muffle electric furnace. This stage is armed at fastening silicate oxide and converting of aluminum oxide to water-soluble compound. This process is characterized by the following general chemical reaction:
Crashed baked, material is lixiviating for dissociating aluminates of alkaline metals from other baked. Material lixiviating has been make by the hot saturated alkaline compound . After that it is necessary to get silica out which is solution state compound for upgrading alumina. Desilication was made in two stages. On the first stage there are terms created for most complete crystallizing of sodium hydroaluminiumsilicate. The second stage is the stage of full desilication. Desilication was made by long boiling of a compound on a hotplate.
The extraction of hydrate aluminum was carried out carbonization: carbon dioxide was slowly skipped through compound at 80oC for 5 hours. Thus sodium and kaliy compound have converted in hydrocarbons. That causes a fall-out the aluminum hydrate. The process has three following reactions:
On the final stage hydrate was filtered.
Previous laboratory researches demonstrated that it is possible to withdraw approximately 80% aluminum oxide which is contained in clay. Subsequent researches are needed to provide efficiency of extraction of alumina and to optimize the ethnology.