Research On The New Technology Of Copper And Iron Extraction From Copper Slag And The Migration Mechanism Of Hazardous Elements In The Process

The recovery of valuable elements from copper smelting slag and the environmental risks caused by hazardous elements are two main topics in the process of disposal and utilization.The recovery of copper from smelting slag directly affects economic benefits,and is the primary task of copper smelting slag recovery and disposal.After copper recovery,the tailings with environmental risks and a large amount of stockpiling should be further melting modified to solve the problem that it is difficult to absorb on a large scale and realize the full utilization of iron resources in the same time.In order to achieve high efficiency recovery of copper from slag,control and enrichment of hazardous elements,a method of"predeprivation of hazardous elements by gas injection-reduction smelting" was proposed to recover copper from slag;In order to realize the large-scale consumption of refractory tailings and the recovery of iron resources,a technical scheme of "copper tailings-steel slag combined smelting reforming and iron separation" with a small blast furnace was further proposed.Through experiment,the removal rule of volatile hazardous elements in copper smelting slag and the mechanism of gas reaction under different gas injection were analyzed.The use of oxidizing gas CO2 can promote the removal of As and Sb,reduce their content in matte and slag,and enrich them in dust.The removal of arsenic by CO2 mainly occurred in the matte inclusion,while the removal of arsenic by CO was mainly related to the arsenic oxide in the slag.Although reducing gas injection can significantly reduce the content of hazardous elements in silicate,but the content of hazardous elements in matte increases sharply,which was not conducive to achieving the goal of lower circulation.In the follow-up process design,it was proposed to use oxidizing gas(CO2)as the removal gas for injection.After high-temperature operation and deep blowing to remove impurities,the reduction smelting process was carried out,which was expected to achieve the goal of lower circulation,lower emissions and dust enrichment.The "predeprivation-reduction smelting" method was tested and verified by pilot scale experiment,and compared with other methods.On the basis of achieving a copper recovery rate over 90%,a horizontal comparison was made on the migration of hazardous elements,the embedding characteristics in ore phases,the occurrence form of hazardous elements and the environmental risks of tailings from different recovery processes.The "predeprivation-reduction smelting" process had obvious advantages in achieving lower circulation,lower emissions,dust enrichment and reducing the environmental risk of As in tailings.In the experiment of comparing the leaching toxicity of tailings,the arsenic concentration in the tailings leaching solution from flotation tailings exceeded the specified safety range.Although the tailings after reduction smelting do not show high leaching toxicity,massive accumulation does not represent absolute safety.The environmental risk of tailings after reduction smelting can be almost ignored,and the applicability of subsequent utilization is stronger.The environmental risk of flotation tailings is much higher than that of reduction smelting slag.It is necessary to further reform the flotation tailings.On the basis of copper recovery,taking the copper extraction tailings as raw materials,the process of combined reforming and iron extraction from copper slag and steel slag were explored through laboratory experiments.Sinter and pellets were prepared by rational design,and the reducibility of artificial ores was tested and evaluated.The reasons for the undesirable reducibility of artificial ores are discussed from the perspective of morphology and elements distribution.The characteristic behavior of sinter and pellets in the cohesive and dripping zone was investigated through the dropping experiment.To extract iron from solid waste,a higher smelting temperature was required to ensure the separation of slag and iron.The heat of slag accounts for most of the heat consumption.Furthermore,the migration behavior and reaction mechanism of hazardous elements in the process of iron recovery from tailings reforming were preliminarily discussed by means of calculation and characterization.The change of occurrence form of hazardous elements was discussed,and the environmental risk of tailings was assessed.The migration of Pb and Zn are obviously different from As and Sb.In each process of iron extraction,As and Sb show the characteristics of iron affinity in the process,and the volatilization is not obvious.Although safe tailings can be obtained through the iron extraction process,a large amount of As and Sb residues dissolved in molten iron may not be conducive to further utilization in the subsequent process.This paper explores and verifies the scientific problems in the process of"predeprivation-reduction smelting" copper extraction and "copper tailings-steel slag combined smelting reforming and iron separation",and deeply discusses the migration and transformation of hazardous elements in the process,the environmental risks of tailings and other related issues.It revealed the internal correlation between the recovery process,the migration of hazardous elements and environmental risks.It provided a theoretical basis and technical support for realizing the resource utilization and harmless disposal of copper slag.