Experimental Research On Modification By Direct Reduction Of Copper Slag

Rapid development of iron and steel industry, leading to the serious shortage of supply of domestic iron ore resources, the dependence on foreign of iron ore is more and more high. On the other hand, the iron has not been effectively recycled which content is about 40% in copper slag. Therefore, it has important significance to recovery iron from copper slag, which reduce the environmental pollution caused by large amount of copper slag heaping, and alleviate iron resources tense situation.The mineralogical study of copper slag shows that iron mainly exists in the form of fayalite, its melting point is low, and the reduction is difficult. Iron and copper is fine-grained dissemination, uniform distribution, a variety of mineral parcels together each other in slag, which make the structure compact, hard, and the chemical properties more stable. In order to effectively recover valuable metal like iron in copper slag and separate iron and silicon, the copper slag must conduct modification treatment, and construct the enrichment phase of iron and silicon. Therefore, the carbon-containing pellets-rotary hearth furnace process to recover iron is put forward. The influence of reduction temperature, reduction time, C/O, copper slag size, coal particle size, Al₂O₃ ratio, magnetite and other factors on metallization and the mineral phase structure changes in direct reduction process of copper slag are systemly studied.The results show that temperature, time, carbon-content, coal powder and copper slag particle size are the main factors which effect the direct reduction process of copper slag. The reduction temperature rises, the metallization rate and the volatilization rate of zinc increase. The reaction time and carbon-content increase, the size of copper slag and coal powder reduce, the metallization rate and the volatilization rate of zinc first increase and then decrease. The addition of Ca O destroy the combination of Si O2 and Fe O, increase the activity of Fe O, and promot the reduction of iron olivine. The addition of Al₂O₃ adjust the composition of the slag, the melting temperature and viscosity of slag. The addition of magnetite increase the quantity of iron core in slag, and promot the aggregation and growth of iron grains.The diffraction analysis of the reduction products shows that the copper slag gradually change from amorphous to crystalline in direct reduction process, meanwhile, the iron olivine in the slag is gradually reduced. the main phase of the reduction product is Fe and Si O2. After adding Ca O and Al₂O₃, the composition of the reduction product is Fe and Si O2, and gradually transformed into Fe, Si O2, Ca Si O3, Mg Al2O4, Fe+2Al2O4, the phase composition of the copper slag has been changed, the slag composition is gradually transformed from Fe O-Si O2-Ca O to Si O2-Ca O-Al₂O₃.The optimum parameters are that the reduction temperature is 1200?, the reduction time is 30 minutes, C/O is 1.4, the copper slag size is 100¹50 mesh, the coal particle size is 150²00 mesh, the alkalinity is 0.4, the magnetite ratio is 20%, Al₂O₃ ratio is 13%. In this case, the metallization rate of copper slag is up to 87.59%, the volatilization rate of zinc is 94.61%.