Abstract The advancement in technology has resulted in the development of newer and improved electrical products. The older products are becoming obsolete and are discarded as waste at a continuously increasing trend. Printed circuit board (PCB) is the main focus of electronic waste recycling because of the inherently high value of contained metals such as gold and copper. Hydrometallurgical route, which is often used to recover the metals, does not take into account the non-metallic PCB fractions. These non-metallic fractions may end up in landfills or incinerated which leads to secondary pollution. In this work, the use of the leached PCB waste fraction as reductant in primary metal smelting operations and solid state reduction is investigated. Laboratory-scale experiments and thermodynamic modelling were performed to simulate solid state reduction of hematite (Fe2O3) using various blends of PCB and graphitic carbon. Differential Scanning Calorimeter (DSC) analysis of several samples were performed up to 1200 °C. Thermodynamic modelling was done using FactSage to predict the products of the hematite reduction below 1600 °C. The study showed that PCB residue might be used to partially replace the conventional reductants. The investigations revealed that at temperatures below 1000 °C, PCB reduces hematite to lower forms of iron oxide at a faster rate than that of graphite. The optimal blend contains about 20 wt% PCB residue which has the same reduction degree as graphite. Thermodynamic modelling of iron smelting was also performed using various blends of PCB and coal. The models showed that PCB residue might be used to partially replace the conventional reductants. The study revealed that in iron smelting, the optimal blend contains around 20 wt% PCB residue, with energy savings of 150 kWh/t of ore to achieve the same metal recovery.

中文翻译：

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废PCB浸出渣作为冶炼过程还原剂的研究

摘要 技术的进步导致了更新和改进的电气产品的开发。旧产品正在变得过时，并以不断增加的趋势作为废物丢弃。印刷电路板 (PCB) 是电子废物回收的主要焦点，因为所含金属（例如金和铜）的固有价值很高。通常用于回收金属的湿法冶金路线没有考虑非金属 PCB 部分。这些非金属碎片最终可能会被填埋或焚烧，从而导致二次污染。在这项工作中，研究了浸出的 PCB 废物部分在初级金属冶炼操作和固态还原中作为还原剂的用途。进行了实验室规模的实验和热力学建模，以模拟使用各种 PCB 和石墨碳混合物的赤铁矿 (Fe2O3) 固态还原。几个样品的差示扫描量热仪 (DSC) 分析在高达 1200 °C 的温度下进行。使用 FactSage 进行热力学建模以预测 1600 °C 以下赤铁矿还原的产物。研究表明，PCB 残留物可用于部分替代传统的还原剂。调查显示，在低于 1000 °C 的温度下，PCB 以比石墨更快的速度将赤铁矿还原为更低形式的氧化铁。最佳混合物含有约 20 wt% 的 PCB 残留物，其还原度与石墨相同。还使用 PCB 和煤的各种混合物对炼铁进行了热力学建模。模型表明，PCB 残留物可用于部分替代传统的还原剂。研究表明，在铁冶炼中，最佳混合物含有约 20 wt% 的 PCB 残留物，可节省 150 kWh/t 矿石的能源，以实现相同的金属回收率。