DE872787C - Process for the extraction of alumina - Google Patents

Description

Methods of Extraction of Alumina In, of late are one Series of processes for the production of alumina have been developed, mainly starting from raw materials containing silica and alumina as starting material. One of these methods is e.g. B. clay first in a known manner with sulfuric acid open minded. The resulting decomposition liquor, which is essentially with Iron sulphate is contaminated aluminum sulphate solution, with the addition of Sodium sulphate and reducing soles brought to dryness, whereupon the dry residue is burned in the rotary kiln to sodium uminate. The Allumin: at is known in Way by defoliation, separation of red mud and further processing on alumina hydrate worked up. The sulfuric acid escaping in the exhaust gases from the rotary kiln becomes processed according to the Konntaktverfa # hren on sulfuric acid, some of which again for the digestion of clay, the other part is used for other purposes Available. In this process, clay and sodium sulphate are used as starting materials Alumina hydrate, sulfuric acid and soda are produced as end products.

The procedure described below is based on the same raw materials off like the known procedure-. However, it avoids the evaporation of the digestion clay produced with sulfuric acid, earth sulfate, eye. The new way of working exists in the following: Calcined clay is digested in a known manner with sulfuric acid. The egg-containing substances obtained after separation of the insoluble silicon-containing substance Aluminum sulphate solution is with; the equivalent amount of alkali sulfate added, in such a way that: to 1 mole of A1203 1 mole of A1kaqi: sulfate is applied.

This solution is now, with oxidizing agents; z. B. H N O 3 or 112 02, 'to convert all dissolved iron into the trivalent form. Then the lye is .in a stirred autoclave, the pressure heating to about 150 to 250 ° below = threw. The largest dough in the clay separates as a basic alka) li@al.aun as well as: the iron as a basic sulphate.

The -basic APkaliaum; .the z. B. in the case of "the application of: Potassium sulfate has the composition 335% A] 203, 39, o% S03 ,, ii, 5% K20, is with at least the amount of alkali metal sulfate necessary for the formation of alkali metal aluminate added, and 'this mixture is with the addition of reducing agents in .known Way at temperatures, from about 100 to 100 ° or above: to alkali aluminate reduced. The be.i. The S 02r-containing gases escaping from the reduction become sulfuric acid processed, some of which is used to digest new quantities of raw materials, and some for other purposes Purposes can be used .; -The further processing of the aluminate clinker too Alumina and soda or potash proceeds according to known processes.

The mother liquor that occurs during autoclave treatment and digestion In addition to converted alkali metal, it contains alkali metal sulfate: and free sulfuric acid. In According to Zugalbe, this lye finds new amounts of sulfuric acid resulting from: the processing the rotary kiln gases can originate, a further digestion of new raw material quantities' instead. After supplementation: that carried away with the solid hydrolyzate during the previous digestion Alkali sulphate quantities by adding the appropriate amount to the digestion liquor this in the same way as the previous batch of autoclave treatment subject. The further processing of the resulting products takes place in the way described above. So it is nowhere in this circular process necessary to evaporate water; while with your known method on i t A1203 \ practical 8 to 9 tons of water have to be evaporated.

When using raw materials containing alkali, such as B. Leucite, Nep'helin or Phonolith., in which the clay is soluble in a known manner by heating has made, the additional introduction of alkali sulfates in the is superfluous Process. In these cases, therefore, I do not receive any additional Schlvefelsäure, because Apart from the clay, the only by-product that falls is soda or potash or both together.

Claims (2)

PATENT CLAIMS: i. Process for the production of alumina from alumina and containing silica. Raw materials: About digestion with sulfuric acid, characterized in that: the digestion solutions separated from the insoluble matter are mixed with at least the amount of alkali metal required for alum digestion, the dissolved iron compounds are converted into the trivalent form and this solution: then in an autoclave heated with stirring to about 150 to 25o °, which separates the d'a.`with obtained solid hydrolysis products from the mother liquor, mixed with the minimum amount of Alhalisulfate necessary for the formation of aluminate and finally glows under reducing conditions to AlkaJi.al:u-:minat, which is processed in a known manner on alumina and alkali carbonate. 2. The method according to claim i, characterized in that one in the hydrolysis resulting mother liquors as well as; the sulfuric acid obtained in the aluminate process for the purpose of opening up further quantities of raw materials.