Study On Arsenic Removal And Iron Reduction From Copper Slag By Pyrometallurgy

In the process of copper smelting,a large number of complex components of copper slag are produced.On the one hand,there are many kinds of valuable metals such as copper,lead,zinc,iron,etc.,which have high recovery value.On the other hand,there are harmful elements arsenic,which are difficult to be removed directly in the process of valuable metal recovery.Therefore,the removal of arsenic has become a key factor affecting the effective recovery and utilization of copper slag.In this paper,the copper slag from the pyrometallurgical process is used as the raw material to carry out the experiments of arsenic removal by roasting in oxidation atmosphere and iron extraction by direct reduction.The effects of different roasting atmosphere,roasting temperature and roasting time on the arsenic removal rate are studied,and the effects of CaCl₂ addition on the copper removal rate are explored.The effects of different carbon oxygen ratio,reduction temperature and alkalinity on the iron metallization rate in the reduction process are analyzed.The results show that:The iron content of copper slag is 45.67%,as content is 0.18%.The main phases are olivine（Fe₂SiO₄）and magnetite.The arsenic oxides include As O,AsO₂,As₂O₃ and As₂O₅（s）in the oxidation atmosphere of 0～1200℃.The process of arsenic removal by oxidative roasting is in accordance with the shrinking nuclear membrane type of gas-solid reaction.The apparent activation energy is 8.8k J,and the limiting link is the interface reaction of arsenic removal by oxidation.Under the reducing atmosphere,the metal Fe is reduced when the reaction temperature is over 716.7℃,and the metal Zn is returned to the original when the reduction temperature is over 985.3℃.The best removal conditions of arsenic in copper slag are as follows:oxygen volume fraction is 10%,calcination temperature is 650℃,holding time is 75 minutes,the removal rate of arsenic is 87.58%,and the residual rate is only 0.022%.The further oxidation of iron peridotite phase and the increase of the size of oxidation products are not conducive to the removal of arsenic.Considering the effects of C/O ratio,temperature and basicity on the metallization rate,the best metallization rate of iron in this paper is 61.99%when the C/O ratio is 1.4,the reduction temperature is 1200℃,and the reduction time is 30minutes.When CaO is not added,the main phases of the reduction products are ferruginous olivine and metallic iron.When CaO is added,the iron olivine phase disappears and calcium silicate（CaSiO₃）phase appears.