火法炼锌铅银渣提银工艺探索

Exploration of silver extraction process from lead-silver slag from pyrometallurgical zinc smelting

云南某冶炼厂在冶炼高铁高铟闪锌矿时产出铅银渣,该渣金属含量高,具有回收价值。目前针对此类型铅银渣的大部分处理工艺以火法挥发为主,存在有价金属回收率低、能耗高、污染环境等问题。该冶炼厂采用湿法对此铅银渣进行了银和有价金属回收的试验,分别探索了硝酸体系和硫酸体系的酸度、浸出剂氨水和亚硫酸钠用量对银和有价金属回收率的影响,最终确定采用铅银渣预处理-氧化焙烧-硫酸浸出-氨水络合-水合肼还原提银-海绵银熔铸工艺流程处理铅银渣。在较优的工艺参数下,生产指标可以达到如下效果:银浸出率>96%,银综合回收率>98%,铜浸出率达到99%以上,铟浸出率为80%以上,提银后终渣Pb含量高达45%,可作为下一步铅冶炼的优质原料。该工艺流程具有设备投资低、工艺控制简单、银回收率高的优点,而且可附加回收的伴生金属多,可为火法炼锌企业进行铅银渣综合回收银提供参考。

Lead-silver slag is produced during smelting of sphalerite with high Fe and In contents in a smelter in Yunnan.This slag contains a high content of metals that are worthy of recovery.At present,the treatment process of such a type of lead-silver slag is dominated by pyrometallurgical volatilization which has shortcomings such as low recovery rate of valuable metals,high energy consumption and environmental pollution.This smelter conducts hydrometallurgical tests about silver and valuable metal recovery,and explores the influence on recovery rates of silver and valuable metals by acidity of nitric acid system and sulfuric acid system and consumption of leaching agents,including ammonia water and sodium sulfite.The final process flow for lead-silver slag treatment is determined as pretreatment-oxidizing roasting-two-stage acid leaching-complexation by ammonia water-silver reduction and extraction by hydrazine hydrate-sponge silver casting.With preferable process parameters,production indicators can be:silver leaching rate>96%;comprehensive silver recovery rate>98%;copper leaching rate>99%;indium leaching rate>80%.After silver extraction,the Pb content in final residue is up to 45%and can serve as desirable raw material for lead smelting in the next step.This process flow is characterized by low equipment costs,simple process control,high silver recovery rate and a great number of recoverable valuable metals,providing reference for pyrometallurgical zinc smelting companies that conduct comprehensive silver recovery from lead-silver slag.