Foundational Study On Separating Technique Of Copper, Tin And Other Elements From Iron By Slagging Method In Metal Recycling

Iron and steel is still the most widely used material in modern human-being society, although various engineering materials have been continuously developing and become diversified day by day. Up to date steel products account for more than 90% in all metal materials that have been consumed. With the rapid depletion of the ore resource in the earth, scrap must become the main source of raw materials in steel making. With this reason it is necessary to establish step by step the iron and steel production system based on scrap. This is also an inevitable requirement and an important and indispensable part of foundations for a sustainable society.The importance of scrap steel recycling in whole circular economy and its key role in iron and steel production were discussed and reviewed in this dissertation The author definitely pointed out unprecedented the negative respect of present way to recycle scrap with dilution method, which belong to still the linear economy ideas. This kind of style based on the only principle of lowest-cost can never meet the requirement of circular economy.It was approved both by the theory and by practice that the quality of steel and its service life were greatly affected by the purity of steel. Steel production would have qualitative change when the content of impurity in steel reduced to certain level. To maintain and keep the purity of matrix materials is critical important in the metal recycling. The value of scrap steel will be mainly decided by the content of harmful residual elements within scrap in the near future.The basic principle of the slagging method to separate ferrous and non-ferrous elements technology was discussed and analyzed. The dissolve behavior of copper and tin in FeO-rich slag was investigated. The copper content in the pure FeO slag was 2.04% as the slag was equilibrium with metal copper under the temperature of 1873K. The copper content in slag went down gradually with the increase of CaO content in the slag. Activity coefficient γCuO0.5 was calculated based on the results of experiments. The relationship between γCuO0.5 and CaO content in slag was deduced by fitting the experimental curve:γCuO0.5 = 3.95 - 2.31 exp(-(CaO%)/16.63)The tin content in the pure FeO slag reached 8.07% as the slag is equilibrium with metal tin under the temperature of 1873K. The tin content in slag went down slightly with the increase of CaO content. The dissolve of tin in slag tended to bemore affectively by oxygen partial pressure. The relationship between γSnO and CaO content in slag was deduced by fitting the experimental curve:γSnO= 1.37-0.021(CaO%)The distribution behavior of copper and tin between FeO-rich slag and metal were studied with the chemical equilibrium method. The results indicated that within the temperature range of 1823-1923K, the relationship between temperature and (Cu%) was expressed as follows:(Cu%) = -1.18 + 8×10-4T, while [Cu] = 10%; (Cu%) = -0.75 + 5×10-4T, while [Cu] = 1.96%The influence of temperature to the distribution of tin between the slag and metal was quite slight while [Sn] = 0.71%. The distribution ratio of copper between slag and metal went up with the raise of temperature. But its influence to the distribution ratio at low copper concentrate was more obvious than at higher copper concentrate. And the increment of increase became plainness as [Cu] content was higher.The distribution ratio of copper between FeO-rich slag and metal was investigated in terms of chemical equilibrium. The relationship between (CuO0.5%) and [Cu%], as [Cu%] is less than 20%, showed:(CuO0.5%)=(0.06922exp(-0.1055[Cu%]) + 0.0216}[Cu%] And as [Cu%] is more than 20%, the expression as follow is more simplification:(Cu%) = 0.01924[Cu%] +0.11804 The relationship of LCu and [Cu] content was.LCu= 0.09exp(-[Cu]/2.30241) + 0.1128exp(-[Cu]/43.300) + 0.01888The composition of the FeO-rich slag influences greatly on the distribution ratio of copper between slag and metal. And proper CaO content in slag may reduce the dissolve of copper in the slag. With the increase of CaO content in slag, the copper content in slag will decrease when the copper content in metal is the same. The influence of CaO content was relatively smaller while [Cu] content was lower and it became greater with the [Cu] content increasing, it reached the maximum as the solution was metal copper. The increment of SiO2 content in the slag made the copper dissolve to be larger under the given experiment conditionsUnder the condition of an induction furnace, the slagging experiments of scrap steel molten were carried out. The results showed that the difference of oxygen blowing had some influence on copper and tin content in the slag The copper content in the FeO-rich slag gained by the measure of the under-surface...