In this work, the local equilibrium modeling method of a non-equilibrium multi-phase reaction system in the top-blowing melting process of electronic waste was studied. The automatic judgment mechanism of phase transformation and the improvement of the trace component solving algorithm were explored to build the mathematical model of the element migration and transformation. Secondly, to determine the distribution mechanism of various elements in top-blowing smelting of electronic waste, the thermodynamic digital simulation system was developed according to the software platform of metallurgical process calculation. On this basis, combined with the industrial production practice, the coupling simulation experiment was carried out to investigate the influence of oxygen:feed ratio, oxygen concentration, amount of additive iron powder and CaO:SiO₂ ratio of the slag on the smelting process. In addition, the direct yields of metals in the slag were Cu 90.69 wt%, Au 98.57 wt%, Ag 94.84 wt%, and Pd 97.87 wt% under the optimum conditions. Finally, the simulated values were consistent with industrial data, which can provide theoretical guidance for the industrial production practice of the top-blowing smelting of electronic waste.

In the present study, the local equilibrium modeling and division method of the multiphase non-equilibrium for the top-blowing smelting process of electronic waste was investigated based on the local equilibrium hypothesis. And the mathematical description of the multi-phase equilibrium of each local area and the correlation method between the local areas were studied by analysis of relationships among the valence state, phase, composition, and Gibbs free energy of each element. Afterward, the reaction characteristic data such as melting material, product phase, composition, temperature, atmosphere, etc. were obtained via industrial measurement experiments. Based on these, a mathematical model of local equilibrium for the top-blowing smelting process of electronic waste was established. Finally, the thermodynamic digital simulation system was developed via the calculation of metallurgical process and online control platform MetCal Desk (v7.00, MetCal, Ganzhou, China), which can investigate the element distribution behavior during the smelting process and provide theoretical guidance for the industrial production practice.

To address the critical challenges in pyrometallurgical recycling processes—such as poor feedstock adaptability, high energy consumption during roasting conversion, and the low added value of rare earth products—this study systematically investigated the mechanism and process optimization of ammonium bifluoride (NH₄HF₂) roasting for the recovery of neodymium–iron–boron (NdFeB) waste. Thermodynamic analysis confirmed the feasibility of the conversion reaction between NH₄HF₂ and the rare earth components in NdFeB waste. Single-factor experiments were conducted to examine the effects of roasting temperature, reaction time, and NH₄HF₂ dosage on rare earth recovery. The optimal conditions were a roasting temperature of 600 °C, a reaction time of 120 min, and a NH₄HF₂ dosage of 75 wt%, achieving a rare earth recovery rate of 98.81%. Furthermore, the response surface methodology (RSM) was employed to establish a quantitative model correlating process parameters with recovery efficiency. Variance analysis demonstrated that the model was highly significant (F = 136.94, p < 0.0001), with excellent agreement between actual and predicted values (R² = 0.9944). Factor contribution analysis revealed that NH₄HF₂ dosage had the most pronounced impact on rare earth fluorination, followed by roasting temperature and reaction time. Under optimized conditions, the purified rare earth fluoride obtained after acid leaching reached a purity of 99.43%, providing high-quality raw material for producing high-value-added rare earth products.