微波诱导电炉粉尘有价组元定向迁移与分离的基础研究

Electric arc furnace (EAF) dust is an important secondary resource containing multiple valuable metallic elements. Its recycling has remarkable economic and environmental benefits. As the dominant technology for treatment of EAF dust, pyrometallurgical processing still suffers from several problems, such as relatively low metal recovery, high energy consumption, and large environmental load. According to the strong microwave absorption characteristics of the components with the spinel structure, the present program proposes the concept of intensifying carbothermic reduction of EAF dust by integrating the effects of biochar, chemical additive and microwave field for induction of directional migration and separation of the contained valuable components, including iron, zinc, lead, chromium and manganese. Besides using biochar as the efficient and clean reducing agent, the program combines the advantages of microwave volumetric heating and the lattice-distorting effect of chemical additive. It will design an optimal composite system of EAF dust and biochar based on the theory of granularity and principle of microwave penetration depth matching for full exertion of the “lens effect” of the irradiated composite system to induce the transformation of spinel structure for directional migration and efficient separation of the valuable components. By coupling the effects of biochar, additive and microwave in transforming spinel structure, the program will build fundamentals of microwave-induced directional migration and separation of valuable components in EAF dust and corresponding technological prototype for their efficient separation. This program is expected to support the development of theory and technology for national clean and efficient sustainable recycling of EAF dust.

电炉粉尘是一种含有多种有价金属的重要二次资源，其回收利用具有显著经济和环境效益。火法工艺是目前电炉粉尘处理的主流工艺，但仍面临金属回收率较低、能耗较高、环境负荷较大等问题。本项目根据电炉粉尘中具有尖晶石结构的有价组分的优良吸波能力，提出微波外场协同生物炭与添加剂作用促进电炉粉尘碳热还原，诱导电炉粉尘有价组元（铁、锌、铅、铬、锰）定向迁移与分离的技术思路。其利用生物炭作为高效洁净还原剂，结合微波体积加热优势和添加剂诱导晶格畸变作用，基于级配和微波穿透深度匹配原则，优化构建电炉粉尘/生物炭复合体系，充分发挥微波辐射体系内的“透镜效应”，诱导尖晶石结构转变，实现有价组元定向迁移与高效分离回收。项目通过耦合生物炭、添加剂与微波在诱导尖晶石结构转变中的作用，构建微波诱导电炉粉尘有价组元定向迁移与分离的理论基础以及高效还原与分离回收技术原型，为我国电炉粉尘的清洁高效可持续资源化利用提供理论和技术支撑。

电炉粉尘是一种含多有价金属的重要二次资源，其回收利用具有显著经济和环境效益。本项目提出微波外场协同生物炭与添加剂作用促进电炉粉尘碳热还原，诱导电炉粉尘有价组元（铁、锌、铅、铬、锰）定向迁移与分离的技术思路。项目首先查明了电炉粉尘中主要物相为磁铁矿和锌铁尖晶石，铬和锰含量较低且主要以铬铁尖晶石以及锰铁尖晶石的形式存在。生物炭具有发达的孔隙结构和较大的比表面积，有助于提高反应速率。其次，本项目查明了尖晶石结构矿物、生物炭、尖晶石结构矿物/生物炭复合体系的吸波性能和高温电磁响应行为。研究表明，当微波频率为2.45 GHz时，与单一尖晶石结构矿物相比，尖晶石结构矿物/生物炭复合体系具有更好的吸波性能。随着温度的升高，尖晶石结构矿物/生物炭复合体系的微波生热机制由介电损耗和磁损耗逐渐转变为导电损耗。此外，本项目通过计算建立了电炉粉尘中有价金属组分的还原反应热力学基础，阐明了尖晶石结构矿物的还原行为。以锰铁尖晶石为例，微波还原过程中锰铁尖晶石中锰和铁元素发生了明显的定向迁移。Na2CO3作为添加剂可降低锰铁尖晶石的初始还原温度，强化碳的气化反应，进一步促进还原。最后，本项目构建了电炉粉尘中有价金属组分综合回收的技术原型。在生物炭配比为0.25，还原温度为1050 ℃，升温速率为25 ℃/min，保温时间为15 min，Na2CO3用量为2 wt.%，气氛为氮气的条件下，电炉粉尘还原产物的铁金属化率为95.13%，锌和铅的挥发率分别达到99.7%和97%。当矿浆浓度为50%，磨矿粒度D(90)为67.93 μm，磁场强度为800 Gs时，还原产物磁选产品的全铁品位为88.57%，铁、铬和锰的回收率分别达到95.89%、79.46%和87.48%，可作为一种良好的炼钢炉料。