Study On The Modification Of Copper Slag With Calcium Borate Additives And The Reduction Of Copper Content In The Slag

With the gradual growth of copper production in China,high-grade copper mines are increasingly exhausted,and the exploitable grade of copper ores has been reduced to less than 0.2%.As a by-product of copper smelting industry,the copper content of copper slag is as high as 0.7-2.3%,However,most copper slag was treated as waste slag,Copper slag pyrometallurgical cleaning technology has become one of the most commonly used slag cleaning methods because of its advantages of less exhaust gas and excellent melt temperature control.In order to obtain better slag cleaning effect,the effect of CaB₂O₃ on Pyrometallurgical dilution of copper slag was studied by using converter copper slag produced by a copper smelting company in Yunnan as raw material and CaB₂O₃ as modifier.The purpose of this study is to explore the effect of CaB₂O₃ on copper slag system,improve slag type and improve the pyrometallurgical slag dilution effect.Firstly,mineralogical studies on copper slag samples were carried out.The results show that copper mainly exists in the form of crude copper in the slag,with copper content of 4.49%;iron mainly exists in the form of magnetite and fayalite in the slag,with iron content of 44.91 wt.%in the slag and magnetite phase content of 34.1 wt.%.Secondly,the experiments of modifying copper slag with CaB₂O₃ additive and reducing copper content in slag were carried out.The results show that with the increase of CaB₂O₃ content in slag,the complex silicate structure in slag tends to simplify,the viscosity of slag decreases,the liquidus temperature decreases,and the fluidity increases.CaB₂O₃ can effectively promote the aggregation and sedimentation of copper in slag.Under the condition of no reductant at 1250?,when the addition of CaB₂O₃ increases from 0 to 6wt.%,the sedimentation effect of copper in slag can be increased by about60%.When ditch oil is used as reductant and CaB₂O₃ was used as modifier,with the addition of CaB₂O₃ increasing from 0 to 6wt.%,the copper content in slag can be reduced from 1.47 wt.%to 0.89 wt.%.CaB₂O₃ has no obvious effect on the reduction reaction between ditch oil and magnetic iron.With the increase of CaB₂O₃ content in slag,the magnetic iron content in slag almost unchanged.In order to further study the influence mechanism of CaB₂O₃ on copper slag,the effect of B₂O₃,the decomposition product of CaB₂O₃,on copper slag system was investigated.The results show that with the increase of B₂O₃ content in slag,the viscosity of copper slag decreases,the activation energy of viscous flow decreases,the micro-morphology of iron olivine phase in slag changes from dendritic to granular,the diffraction peak of iron olivine phase in XRD pattern decreases,B₂O₃ can combine with free CaO and MgO in slag to form low melting point eutectics such as CaB₂O₄,CaB₄O₇and MgB₄O₇,which can reduce liquidus temperature of copper slag.