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

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 degrees C, 330-370 degrees C and 430-480 degrees 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.