The Extration Process Research Of ?-Alumina In Aluminum Ash Via Sintering Method With Alkali

Aluminum ash is an industrial waste produced during aluminum electrolysis and processing.The annual output of aluminum ash is huge and the composition is complex in China.Untreated aluminum ash has certain pollution to the atmosphere,soil and water resources.Since 2008,it has been listed as the National Hazardous Waste List.At present,some progress has been made in the process of recycling aluminum ash,but many processes also have a series of problems such as high production cost,low added value of products,and low demand for aluminum ash.The?-Al₂O₃ in aluminum ash is difficult to recycle by conventional metallurgical methods,and is mostly used as a paving material,which greatly wastes aluminum resources.In this paper,the aluminum ash is prod uced during the aluminum casting process,and the aluminum resources are mainly in the form of structurally stable?-Al₂O₃.This paper mainly solves the problem that?-Al₂O₃ in aluminum ash is difficult to recover,and realizes the comprehensive recycling of alumina in aluminum ash.The process for recovering alumina in aluminum ash mainly includes six processes of aluminum ash desalination treatment,sodium aluminate clinker preparation,atmospheric pressure dissolution,refined desiliconization,seed crys tal decomposition and high temperature calcination,and the process has simple process,low production costs and good product quality.In this paper,aluminum-ash was used as raw material to dissolve?-Al₂O₃ in aluminum ash by alkali sintering method.At the same time,the ratio of alkali-ash ratio,sintering temperature,sintering time,liquid-solid ratio,dissolution temperature and dissolution time to aluminum ash was investigated.The effect of Al₂O₃ dissolution rate showed that the alkali-ash ratio was 2.0,the sintering temperature was 750°C,the sintering time was 120 min,the liquid-solid ratio was5:1,the dissolution temperature was 100°C,and the dissolution time was 30 min,the dissolution rate of alumina was 93.26%.The main factors affecting the dissolution of alumina were the sintering temperature,alkali-ash ratio and dissolution temperature by orthogonal experiment.Through the desilicication treatment of sodium aluminate solution by adding calcium oxide during the sintering process and re fining process,the desilication mechanism and the composition of the residue phase of calcium oxide added during the sintering process and the refining process were investigated,and the effects of calcium oxide addition,desilication time and desilicatio n temperature on the desilication efficiency of sodium aluminate solution were investigated.The results show that the desilication residue is mainly hydrated garnet with low solubility,and the final desilication efficiency can reach 95.80%,which meets t he requirements of seed crystal decomposition of sodium aluminate solution.The caustic concentration of the sodium aluminate solution was reduced by the addition of calcium oxide and sodium bicarbonate,and the effects of caustic concentration,seeding time,and seed crystal on the decomposition of the seed crystal were investigated.The seed crystal decomposition rate of the sodium aluminate solution after the alkali removal treatment reached 48.73%.The purity of the obtained alumina product was 99.40%by X-ray fluorescence spectroscopy,and the quality of alumina was in line with the second grade of China's metallurgical grade alumina industry standard?YS/T 803-2012?.At the same time,the recycling of the alkali-removing solution and the seed liquor is realized,and the alkali consumption of the whole alumina production process is low,and therefore,the production cost is low.