Study On The Process Of Recycling Alumina From Secondary Aluminum Dross

Aluminum dross is a by-product of the aluminum industry.As the world’s largest producer of primary aluminum,China produces a huge amount of aluminum dross every year.Aluminum dross,which is not treated with innocuous treatment,will cause harm to the water,atmosphere and soil.Aluminum dross is listed in"National Catelogue of Hazardous Waste（2016 Revision）".The traditional secondary aluminum dross recovery process has the disadvantages of small scale,low product value and high cost.In this paper,aluminum oxide was obtained from secondary aluminum dross including the processes of milling,screening,gas producing at medium temperature,aluminum oxide dissolution in alkaline solution at high temperature,seeded precipitation,and calcination at high temperature.The process has the advantages of simple flow,low cost and easy operation.The process not only realizes the recovery and reuse of the gases,but also obtains product of aluminum oxide with better quality.The effects of solid-liquid ratio,concentration of alkaline solution,reaction time and reaction temperature on the dissolution rate of aluminum oxide in secondary aluminum dross were investigated in this paper.When the solid-liquid ratio is 0.08,the concentration of Na₂O_K is 248 g/L,the reaction temperature is 250℃,the reaction time is 3 h and the stirring speed is 400 r/min,the maximum dissolution rate of aluminum oxide from secondary aluminum dross is 98.6%.The main components of filter residue are cancrinite andα-alumina.When the alumina concentration in sodium aluminate solution is 102.1 g/L,the amount of seed is 468.5 g/L,the precipitation temperature is 25℃,the stirring speed is 160 r/min and the precipitation time is 72 h,the maximum seed precipitation rate is60.1%.The aluminum hydroxide after seeded precipitation is calcined at 1200℃for 1h to obtain the product of aluminum oxide that meets the grade 3 standard in"YST803-2012 metallurgical grade aluminum oxide".The life cycle assessment of aluminum oxide production process from secondary aluminum dross was compared with the life cycle assessment of aluminum oxide production process from bauxite.The results showed that production of aluminum oxide from aluminum dross has a 34.6%reduction in environmental impact and a62.9%reduction in economic costs as compared to the production of aluminum oxide from bauxite.The process of producing aluminum oxide from aluminum dross has better environmental and economic performance than the process of producing aluminum oxide from bauxite.