铜渣一步还原回收铁水与铜锍的基础研究

The low efficiency of copper recovery and separation of copper from iron are the two main factors restricting the copper slag recycle. In this study, the one–step carbonthermic reduction method will be adopt to process copper slag, and mineral reduction as well as vulcanization process are completed simultaneously. Thus, the iron exists in the form of metallic phase, and copper in the form of sulphide, finally, the separation between copper and iron and comprehensive recovery of metal elements are realized. The reduction, vulcanization as well as carburization process of minerals in copper slag will be studied to discuss the reaction mechanism and control step, to realize the precise control on mineral composition, which supplies theory basis for the separation among iron, copper matte and slag. The research on the equilibrium of iron-matte and slag-matte is proceeded to reveal the enrichment effect of matte on minor elements. The effect of CaS, as the desulfurization product, on the properties of matte and slag phases is going to discuss, to reveal the distribution law between slag and matte. On this basis, the effect of sulfide additives on minor elements distribution among three phases is exploring to determine the adding process and content of sulfides. Finally, the separation process of slag-iron and iron-matte will be studied through the confocal laser scanning microscope (CLSM) observation, and mechanism as well as conditions of iron-matte-slag three-phase separation is to be discussed, and a new concept based on triphase metallurgy will be put forward.

铜的回收效率低下以及铜、铁的分离问题是制约铜渣回收利用的两个主要因素，本项目拟采取碳热一步还原法处理铜渣，同步实现矿物的还原及硫化过程，使铁以金属形态存在，铜及其它微量元素以硫化物的形态富集，实现铜、铁分离的同时，起到对金属元素综合回收的效果。拟通过研究矿物的还原、硫化及渗碳过程，探讨各自的反应机理及控速环节，实现对铜渣还原、硫化与渗碳过程的精确控制，为渣、铁、锍的分离奠定理论基础；研究铁-锍、渣-锍的两相平衡，揭示锍相对微量元素的富集规律；探讨脱硫产物CaS对锍相和渣相性质的影响，揭示CaS在渣-锍两相间的分配规律，在此基础上，探讨硫化物添加剂对微量元素在铁-锍-渣三相间分配的影响，确定硫化物的添加工艺和含量；最后，通过激光共聚焦扫描显微镜（CLSM）观察研究渣-铁、铁-锍两相的分离过程，探讨铁-锍-渣三相的分层机理和条件，提出一种基于渣-锍-铁三相冶金的新概念。

通过化学分析和扫描电镜及微区能谱分析，考察了铜渣的矿物组成及微观形态，结合铜渣的高温特性研究，探讨了渣、铁、锍三相分离工艺处理铜渣的必要性，在此基础上，研究了Cu在渣、铁、锍三相之间的转化和富集规律，针对影响铜、铁分离的各因素及相应机理进行了重点研究。研究结果表明，三相体系下铜以硫化铜的形态富集于锍相和铁水中，铁-锍两相平衡过程决定铜的最终分配状态，而铁水渗碳含量、锍相量以及锍相成分均对铁、锍平衡产生显著影响。锍铁比低于0.1的范围内铜在锍、铁之间的分配比随锍相量逐渐增大，CaS和Na2S均能提高锍相活性，但CaS的影响与其在锍相的溶解度有关。熔融还原渗碳阶段Fe2+含量与粒铁渗碳含量处于化学动态平衡，主要受熔渣成分的影响，渣、铁分离阶段的渗碳过程决定最终铁的物理渗碳极限。当固定碳存在的情况下，CaO或Na2CO3均能与FeS发生反应，且CaS在锍相中是简单的溶解过程，Na2S与锍相形成复合硫化物NaFeS2。铜渣的三相分层过程中渣、锍存在两次分离过程，熔分初期渣相中FeO和锍相中FeS发生相互转移，完成渣相与锍相的初次分离；之后渣相FeO被气相空间的还原气氛还原为金属铁并通过界面张力保持在渣相顶部，FeS在渣相溶解度降低与金属铁形成新的锍相，完成渣与锍相的二次分离，锍相发生分层现象；最后，上下部锍相汇集，并完成铁、锍两相分离过程。铜渣复合球团中，以石灰为熔剂控制碱度在0.4～0.6或碳酸钠加入量高于铜渣质量的10%，锍相量为铜渣质量的4%可以满足铜、铁分离要求。