超重力分步分离废弃电路板中各类有价金属的基础研究

After crushing and separation of waste printed circuit boards (WPCBs), a mixture of metallic particles (MMP) is obtained. The MMP is of great value to be recycled, since it contains many valuable metals, such as copper, tin, lead, aluminum, gold, silver, platinum and palladium. However, how to separate the different metals in MMP cleanly and efficiently is still an urgent issue to be solved. In this project, based on the difference in melting points of metals, a new method is proposed for stepwise separation of various metals in MMP by super-gravity technology. To solve the basic theoretical problems of this new method, the experimental study on the stepwise separation of valuable metals in MMP in super-gravity separation and liquation processes will be conducted. Firstly, on the basis of the investigation on the composition and structure of MMP, the MMP analogue consisted of different pure metals and real MMPs in WPCBs will be utilized to study the mechanism of super-gravity separation of different metals and the enrichment behavior of noble metals in the super-gravity separation process. The behavior of interfacial reaction of different metals will be investigated. The optimum conditions and adjustment measures will also be determined. After the super-gravity separation process, pure metals or alloys are obtained. The study on the behavior of alloys in the super-gravity liquation process will be conducted in order to obtain the key kinetic data on the nucleation, growth and enrichment of the valuable metal enriched phase. Finally, the fundamental theory and process model of the stepwise separation of various metals in WPCBs by super-gravity technology will be established in this project. The research will promote the clean and efficient utilization of WPCBs in China.

废弃电路板经破碎分选后，得到多金属富集体，富含铜、锡、铅、铝及金、银、铂、钯等有价金属，回收意义重大。但如何清洁、高效的分离各类金属仍是一个亟待解决的问题。本项目依据废弃电路板中各金属熔点差异，提出一种利用超重力技术分步分离富集其中各类金属的新方法。针对该方法关键环节的基础理论问题，开展超重力分步熔融分离及熔析提纯多金属富集体中各类金属的实验研究。在多金属富集体物性结构研究的基础上，从简单纯金属颗粒模拟物逐渐过渡到多金属富集体，系统研究各金属在超重力环境下的熔融分离机制，明晰贵金属在分离过程中的富集行为，探析金属间界面反应规律，优化工艺参数和调控措施；研究分离出的合金相在超重力条件下的熔析行为规律，获取超重力环境下有价金属富集相的形核、长大及富集行为等关键信息；建立超重力分步分离富集废弃电路板中有价金属的理论基础及工艺模型。本项目的成果必将会对我国废弃电路板清洁高效利用起到积极的推动作用。

本项目提出了一种超重力分步分离废弃电路板中各类有价金属的新方法，系统研究了废弃电路板多金属富集体物性结构，熔融分离过程中金属间界面反应行为，各金属在超重力环境下的熔融分离机制与关键工艺参数对分离效率的影响，贵金属在分离过程中的富集行为，以及超重力熔析过程中有价金属富集相的定向迁移规律。主要结论如下：（1）电路板主要金属元素为Cu、Zn、Pb和Sn，主要以金属单质和少量合金的形式存在的，贵金属Au、Ag、Pt和Pd以团聚体的形式分散在多金属富集体颗粒中。（2）熔融分离过程中，界面反应主要发生在Pb-Sn、Cu-Sn与Cu-Zn间，较小粒径和不规则形状不利于各类金属的分离和回收。（3）基于各金属熔点不同，建立了三步分离废弃电路板中有价金属的工艺流程。提高重力系数有利于增加各金属分离效率，而加热温度是控制合金成分的关键因素。在重力系数1000、分离时间5min以及分离温度410℃、800℃和1300℃下，分别获得Pb-Sn合金、Cu-Sn合金和Cu-Zn合金，Cu、Zn、Pb和Sn的总回收率分别为98.8%、87.0%、98.3%和92.6%。（4）贵金属Au、Ag和Pd主要富集在Cu-Zn合金和残渣中，与原料相比，Au、Ag、Pd在Cu-Zn合金中的含量分别提高了2.05、1.65、1.54倍，在残渣中分别提高了1.02、0.63、2.62倍。降低冷速有利于合金中金属元素的析出和富集，在冷却速率为2℃/min时，贵金属随Pb和Sn富集在合金的下部。（5）经超重力熔析处理后，Pb-Sn合金进一步分离为先析出富Pb相和Pb-Sn共晶相，Cu-Sn合金进一步分离为Cu-Zn-Sn相和Cu-Sn相，金属品位的提高大大提升了后续提纯处理的经济与环境效益。（6）对电子废弃物中有价金属超重力选择性分离工业装置进行了概念设计及原理验证，为新工艺的工程化应用提供依据。

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