Basic Research On Reduction And Depletion Of Oxygen-enriched Top-blown Copper Smelting Slag And Slag Shape Contro

The oxygen-enriched top-blown bath smelting technology of copper concentrate realizes the efficient production of matte,which is in line with the development direction of modern nonferrous metal smelting.However,due to the wide source of copper concentrate,the increasingly complex composition and the high oxygen potential in the smelting process,the slag type of the produced copper slag is unreasonable and a large amount of high-melting Fe₃O₄ exists,resulting in high slag viscosity and high copper content in the slag.Therefore,oxygen-enriched top-blown copper slag needs to be cleaned in the slag cleaning furnace,aiming to reduce Fe₃O₄ in the slag to Fe O by adding reductant,thus forming Fe₂Si O₄ phase with low melting point,and regulating Ca O,Si O₂and other slag components content to optimize the slag type,so as to improve the physical and chemical properties of copper slag,promote the effective separation of slag and matte,reduce the copper content in slag and increase the recovery of matte.When the oxygen-enriched top-blown slag is cleaned in the slag cleaning furnace,aiming at the problems of the non-renewable and expensive traditional fossil reductant diesel oil,and the unclear influence of Ca O,Si O₂ and other slag components on the copper content in the slag,this paper proposes to use renewable rubber seed oil and cheap waste motor oil to replace diesel oil for copper slag cleaning,the influence mechanism of slag components on the physical and chemical properties of copper slag,phase transformation and copper content in slag,the matte settling behavior and key factors affecting matte settling,and the kinetics mechanism of reduction process of Fe₃O₄ in slag and carbon reductant are systematically investigated.The specific research results are as follows:The settling behavior of matte in copper slag,and the key factors affecting the settling of matte and copper content in copper slag were clarified.The matte particles in the upper layer of the copper slag are spherical,and the shape of the matte particles in the middle layer and lower layer of the copper slag are droplet.The average diameters and settling velocity of matte particles in the upper,middle and lower layers increase gradually,which are 23μm,38μm,60μm and 3.28×10^-6 m/s,4.80×10^-5 m/s,1.19×10^-4m/s.The settling behavior of matte particles in slag is a process of aggregation and growth,and the matte layer is formed by enrichment at the bottom of the slag.With an increase in settling time and system temperature,the foaming slag disappears,and the copper content in the slag decrease,which is conducive to the recovery of matte from the slag.Add an appropriate amount of anthracite（≤0.67 wt.%）to 60 g of copper slag,Fe₃O₄ in the copper slag is reduced to Fe O,the slag viscosity and copper content are decreased,which is conducive to the settling and enrichment of matte.When excessive anthracite is added（>0.67 wt.%）,Fe₃O₄ is excessively reduced,Fe-Cu alloy phase with a high melting point is formed in the copper slag,which deteriorates the fluidity of the slag,hinders the separation of slag and matte,increases the copper content of the slag,and produces foaming slag.In the research on the process of rubber seed oil and waste motor oil to clean oxygen-enriched top-blown slag,the cracking characteristics of rubber seed oil and waste motor oil at high temperature are investigated,the feasibility and application prospects of using rubber seed oil and waste motor oil as reductant for the cleaning of copper slag are verified.The products by rubber seed oil and waste motor oil cracking at high temperature are mainly C,H₂,CO and other reducing substances.When the temperature is raised,the total amount of gases generated from the oil cracking is elevated.When rubber seed oil and waste motor oil are used to clean copper slag,increasing oil amount,reduction temperature and settling time are beneficial to lower the Fe₃O₄ concent and copper content in the slag.Under such conditions（300 g copper slag,the temperature of 1250℃,the rubber seed oil amount of 4 m L or the waste motor oil amount of 1.4 m L,and the settling time of not less than 1.5 h）,the Fe₃O₄ content of copper slag is reduced to less than 5 wt.%,the copper content in the slag is found to be less than 0.57 wt.%,meeting the industrially discardable criteria for slag,which realizes the effective recovery of matte in the cleaning process.Compared with traditional fossil reductant diesel oil,the process of using rubber seed oil or waste motor oil to clean copper slag can reduce the production cost,which is more in line with the concept of sustainable development of China’s copper metallurgy industry and the requirements of environmental protection,and has good application prospects.When studying the kinetic mechanism of the reduction of Fe₃O₄ in copper slag by carbon reductant graphite rod,the limiting step of reduction process is studied,and the kinetic parameters such as reaction order and activation energy are revealed.When graphite rod is used as reductant to reduce Fe₃O₄ in copper slag,with the increase of temperature and reduction time,the Fe₃O₄ content and copper content in slag decrease,the thickness of fayalite slag layer increases,and the foaming slag gradually disappears.Within the temperature range of 1250-1325℃,the reduction reaction of Fe₃O₄ in slag by the graphite rod is the second order reaction,the apparent reaction rate constant gradually increases with the increase of reduction temperature,the apparent activation energy is 610 k J/mol and the limiting step is the Boudouard reaction.In the basic research on the slag type regulation of oxygen-enriched top-blown slag,the effects of Ca O,Si O₂ and other slag components on the physical and chemical properties of copper slag,the copper content of copper slag and the phase transformation are explored,and the slag composition with low copper content is obtained.With the increase of Ca O content in the slag,kirschsteinite,calcium ferrite and Ca O will be formed successively in the slag,the slag viscosity,melting temperature and copper content in the slag first increase,then decrease,and finally increase again.With the increase of Mg O content,high melting point hortonolite and pleonaste will be formed successively in the slag,the viscosity and melting temperature increase,the silicate structure of copper slag tends to be complex,the matte settling and enrichment environment worsens,and the copper content increases.With the increase of Al₂O₃content,high melting point hercynite and almandine will be formed successively in the slag,the slag viscosity and copper content in the slag first decrease and then increase rapidly.As the content of Zn O,Fe O and Si O₂ in the slag increases,the fluidity of copper slag and slag-matte separation environment are improved,foaming slag disappears,and the slag viscosity and copper content gradually decrease.When the slag composition is Ca O 2.02 wt.%,Si O₂20.12 wt.%,Mg O 1.86 wt.%,Zn O 1.74 wt.%,Fe O 28.10 wt.%,Al₂O₃3.77 wt.%,the copper content of the slag decreases to 0.48 wt.%,meeting the industrially discardable criteria for slag.This study solves the problems of non-renewable and expensive reductant resources in the traditional copper slag electric furnace cleaning process,and provides a theoretical basis for optimizing the slag composition,improving the physical and chemical properties of copper slag,and reducing the copper content of slag during the slag type regulation of the oxygen-enriched top-blown slag cleaning process.