The present work focuses on the co-processing and resource recycling of solid wastes with various valuable metallic resources generated by the steel-making process. The carbon-containing pellets were prepared using zinc-bearing dust and chromium-containing sludge as the main raw materials. Then the pellets were reduced in a tube furnace with different roasting temperatures (800–1300 °C), roasting time (10–60 min), and carbon contents (9–17 wt%). The reduction mechanism of the carbothermic reduction was characterized based on thermodynamic analysis and XRD. In addition, based on the non-isothermal thermogravimetric method, the kinetics of the reducing process was investigated at heating rates of 15, 20, and 25 °C/min. The results show that mixture pellets composed of zinc-bearing dust and chromium-containing sludge can contribute to a fine integrated system. The ZnFe₂O₄ and FeCr₂O₄ phases can effectively be decomposed into iron oxide and chromium oxide at 1000 °C. As the temperature rises, iron oxide followed the law of stepwise reduction and was reduced to pure iron. Compared with iron oxide, chromium oxide can be reduced to pure chromium at a higher temperature. The kinetics results show that the reaction process can be divided into five stages and the main three stages follow the three-dimensional diffusion model. This study provides a new method and insight into the feasibility of the co-processing of various wastes with different valuable resources.

Graphical Abstract

中文翻译：

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含碳颗粒的碳热动力学和反应机理：含铬污泥和含锌粉尘的联合处理

目前的工作重点是炼钢过程中产生的各种有价值的金属资源与固体废物的协同处理和资源化利用。以含锌粉尘和含铬污泥为主要原料制备含碳球团。然后在不同焙烧温度（800-1300 °C）、焙烧时间（10-60 分钟）和碳含量（9-17 wt%）的管式炉中还原球团。基于热力学分析和XRD表征了碳热还原的还原机理。此外，基于非等温热重法，在15、20和25°C / min的加热速率下研究了还原过程的动力学。结果表明，由含锌粉尘和含铬污泥组成的混合颗粒有助于形成精细的集成系统。锌铁₂ O ₄和FeCr ₂ O ₄相在1000℃时能有效地分解成氧化铁和氧化铬。随着温度的升高，氧化铁遵循逐步还原的规律，被还原为纯铁。与氧化铁相比，氧化铬在较高温度下可还原为纯铬。动力学结果表明，反应过程可分为五个阶段，主要三个阶段遵循三维扩散模型。本研究提供了一种新方法，并深入了解了利用不同有价值资源协同处理各种废物的可行性。

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