Effects of microwave heating on the carbothermic reduction of steel plant mill scale using lignocellulosic biomass as the reducing agent

ABSTRACT

The microwave reduction of a biomass-bearing mill scale composite briquette followed by magnetic separation was investigated in this work to explore the feasibility of using microwave heating technology on steel plant mill scale. The activation energy obtained for pyrolysis of biomass by Freeman-Carroll method was 189.3, 103.26 and 89.82 kJ mol⁻¹ at the temperature ranges of 260–300°C, 330–370°C and 430–480°C, respectively. By comparing the two reducing agents with microwave (MW) heating, the iron content in a magnetic product was approximately 97.15% and 96.46%, respectively, using coal and biomass as the reducing agents. The iron recovery only reached 85.15% with coal. In addition, up to 96.12% of the iron was recycled using biomass fuel as the reducing agent. In particular, the contents of carbon, phosphorus and sulphur using biomass as the reducing agent were far below the content of those using coal as the reducing agent.

KEYWORDS:

• Mill scale
• biomass
• reduction
• magnetic separation
• recovery
• microwave heating
• thermodynamics
• kinetics

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors received financial support from the National Natural Science Foundation of China (Nos. 51674139, 51874171) and University of Science and Technology Liaoning Talent Project Grants (No. 601011507-05).