Recovery of Iron from Copper Slag Using Coal-Based Direct Reduction: Reduction Characteristics and Kinetics

Hanquan Zhang,Chaojie Hu,Wangjie Gao,Manman Lu

doi:10.3390/min10110973

Hanquan Zhang, Chaojie Hu + Show 2 more

Open Access

https://doi.org/10.3390/min10110973

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Journal: Minerals	Publication Date: Oct 31, 2020
Citations: 16	License type: CC BY 4.0

Affiliation: Wuhan Institute of Technology, Central South University

Abstract

The Fe3O4 and Fe2SiO4 in copper slag were successfully reduced to metallic iron by coal-based direct reduction. Under the best reduction conditions of 1300 °C reduction temperature, 30 min reduction time, 35 wt.% coal dosage, and 20 wt.% CaO dosage (0.75 binary basicity), the Fe grade of obtained iron concentration achieved 91.55%, and the Fe recovery was 98.13%. The kinetic studies on reduction indicated that the reduction of copper slag was controlled by the interfacial reaction and carbon gasification at 1050 °C. When at a higher reduction temperature, the copper slag reduction was controlled by the diffusion of the gas. The integral kinetics model research illustrated that the reaction activation energy increased as the reduction of copper slag proceeded. The early reduction of Fe3O4 needed a low reaction activation energy. The subsequent reduction of Fe2SiO4 needed higher reaction activation energy compared with that of Fe3O4 reduction.

Highlights

In China’s copper industry, pyrometallurgy technology is presently the primary process for crude copper production [1,2]
The kinetics of direct reduction was clarified by kinetic model calculations
The pellets with diameters of 8–16 mm were sifted out as the qualified the pellets were dried in an air-dry oven at 105 ◦ C

Summary

Introduction

In China’s copper industry, pyrometallurgy technology is presently the primary process for crude copper production [1,2]. Many researchers have published studies on the utilization of copper slag, for example, as a cement additive [12], for preparing abrasive tools [13], for pavement materials [14], and for preparing glasses [15] These processes could utilize the copper slag at low cost. These crude utilization methods neglect the recovery of valuable metals in copper slag, resulting in a waste of resources. The iron concentration with 73.20 wt.% iron grade and 95.56% recovery rate was obtained under a reduction temperature of 1300 ◦ C [31] For these reasons, Fe resources contained in copper slag can be recycled efficiently by the direct reduction method. The kinetics of direct reduction was clarified by kinetic model calculations

Materials

Experimental Methods

Reduction Kinetic Models

Thermomechanical Analysis

The Effects of Reduction Temperature and Time

The Direct Reduction Kinetic Model Analysis

Conclusions