Thermodynamic Analysis of Vacuum Carbothermal Reduction for Synthesis of Ferrosilicon Alloy from Pickling Sludge

In the process of silicon steel sheet production, the hydrochloric acid pickling process was employed to remove the oxides on the surface of the silicon steel sheet. In this process, a lot of pickling sludgePickling sludge was generated and suspended in the acid, which could seriously block the effect of the pickling process, so it must be removed from the acid. However, silicon is not used effectively, which results in a waste of resources. In this study, a new utilization method, synthesis of ferrosilicon alloyFerrosilicon alloys from pickling sludgePickling sludge by vacuum carbothermal reductionVacuum carbothermal reduction, has been proposed. The Gibbs free energies of reductions and the reduction sequence had been calculated. The results showed that it obeyed the step-by-step reduction process, and the formation temperature of ferrosilicon alloyFerrosilicon alloys decreased with the gas pressure drop. The appropriate reaction conditions were ascertained, which can be employed in the experiments.