Work

Recovery of iron from iron tailings by co-pyrolysis with coal gangue: process optimization and economic evaluation

Year: 2025

Type: article

Abstract: Iron tailings and coal gangue are voluminous solid waste byproducts. However, traditional disposal methods and conventional reduction roasting often are hindered by high costs and a reliance on external fossil fuels as reductants. To overcome these challenges, this study introduces a novel co-pyrolysis process utilizing coal gangue as the sole reductant source for recovering iron from tailings. Key process parameters, including co-pyrolysis temperature (600 – 900 °C), co-pyrolysis time (20 – 60 min), coal gangue ratio (10 – 50 wt%), and magnetic separation intensity (60 – 140 mT), were optimized. In optimal conditions (800 °C, 30 min, 20% wt%, 100 mT), an iron concentrate with 59.10% total Fe (TFe) and 75.4% recovery rate was obtained. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) revealed that the pyrolysis of coal gangue generated reducing gases (CO, H 2 , CH 4 ) and fixed carbon. These reductants were capable of converting the weakly magnetic hematite (Fe 2 O 3 ) to the strongly magnetic magnetite (Fe 3 O 4 ), facilitating efficient low-intensity magnetic separation. An economic evaluation of a production scale of 250,000 t/y showed a net cost of 86.79 USD/t after accounting for byproduct revenue. Importantly, aiming for a zero-waste process, the residual waste was successfully transformed into high-strength non-fired bricks, providing a technically viable and economically superior closed-loop solution compared to existing single-stream utilization methods.

Source: Scientific Reports

DOI: 10.1038/s41598-025-32505-w

Authors: Zheng Liu, Fengxing Zhang, Guanling Zheng

Institutions: Xiamen University of Technology, Xiamen University

Language: English

Topic: Iron and Steelmaking Processes

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Responsible consumption and production, Affordable and clean energy, Climate action

Open Access status: gold

Estimated APC paid: $2,690