Investigation Of Extracting Iron From Tailings Of Slow Cooling Copper Slag By High-temperature Reduction

In recent years,China has grown rapidly to the largest refined copper producer in the whole world,which accounts for 1/3 of the whole production.At present,China's copper is mainly produced by pyrometallurgical process.In the process of copper pyrometallurgy,1 tons of refined copper concentrates accompanied by 2.2 tons of copper slag,the copper slag emissions will be more than 10 million tons each year.Most of the copper slag is piled in the slag field,not only occupy the land and pollute the surrounding environment,but also cause a huge waste of resources.The valuable composition of copper slag is mainly iron silicate,and the total iron grade is about 40%.The iron is hardly to be concentrated by traditional mineral processing methods as the iron mainly exists in the form of fayalite and fine dissemination.Therefore,it is of great importance to recycle the iron from the copper slag.In this paper,copper tailings of slow cooling slag from Zijin Copper Company were selected for study.The high-temperature reduction-magnetic separation was carried out after mixed with the reductant anthracite and additive calcium oxide.The effects of reduction temperature,reduction time,ratio of anthracite,ratio of calcium oxide have been optimized.Reduction temperature showed a greatest impact on the test,followed by reduction time,ratio of anthracite and ratio of calcium oxide.The rise of reduction temperature and the extension of reduction time are conducive to the improvement of the grade and recovery of iron concentrate.The optimum conditions could be attained under the conditions that the reduction temperature was 1300?,the reduction time was 3h,the ratio of anthracite was 30%and the ratio of calcium was 15%.Under this condition,the grade of iron could be 91.50%and the recovery could be 90.66%.The mineral composition and microstructure of the reduction product have been studied by the EPMA and polarizing microscope.The results showed that the rise of the temperature was good for the accumulation and growth of the metallic iron,and the grown metallic iron particles were separated from the gauge gradually until they were disseminated on the surface of the gangue.Moreover,the extension of the reduction time,which was good for the growth of the iron particle and the rise of the percentage of big iron particles,and which was also good for the iron to precipitate out.The mechanism analysis of extracting iron from tailings of slow cooling copper slag by high-temperature reduction shows that the rise of reduction temperature can reduce the nucleation barrier of metallic iron particles and accelerate the diffusion of the iron particle,which can quicken up the iron particle to nucleate and grow.As the reduction time becomes longer,the diffused distance of iron particle will become larger and the smaller iron particles will become closer to the larger ones which promote the growth of the iron particles.The nucleation of iron particle is composed by reduction nucleation,high-temperature reduction and the coarsening of iron particle.In this paper,coal blending high-temperature reduction-magnetic separation is effective in terms of extracting iron from tailings of slow cooling copper slag,which offers a valuable reference about the utilization of copper slag.