Analysis of Technological Issues, Related to Processing of Alunite at Ganja Alumina Plant (GAP), and Ways of Their Solving

Abstract

In 1965, the Ganja Alumina plant (GAP) started implementing an alkaline reduction technology for processing of alunite ore on an industrial scale. Technological deficiencies, together with design errors, led to unprofitable production. Since the plant was established, studies have been conducted to eliminate deficiencies in the reduction process, through alkaline technology and hardware design. A “reversed” scheme was developed for hydrochemical processing of alunite restored with the conversion of sodium sulphates using a KOH solution. Despite the elimination of several shortcomings in alkaline reduction technology, certain drawbacks remained, in particular- 1) significant emission of gas and dust from the kilns of fluidized bed furnace during roasting and recovery; 2) insufficient time for recovery of alunite powder, which complicates and worsens the technological and economic aspects of the process; 3) passivation of alumina in the roasting and reduction processes; 4) low yield alumina yield in the commercial product (≤ 75%); and 5) a significant amount of solid waste- 5 tonnes of red sludge per 1 tonne of AL2O3, and errors. As a result, the alunite ore processing line ceased production in 1992 and has not operated since. This article is devoted to the development of new technologies and the improvement of a new potash-alkaline method and new soda-alkaline technology for processing alunite ores. The replacement of potash with soda (sodium carbonate), using new soda-alkaline technology, is proposed. Processing of solution from the first leach with sodium sulphate by conversion with KCl leads to production of K2SO4 and NaCl. Use of the soda-alkaline technology allowed us to obtain the same products as with potash-alkaline technology, with an additional product – table salt. The fluidized bed furnace was replaced by a new type of kiln.