A mathematical model of multistage and multiphase reactions in flash smelting furnace, which based on the description of chemical reactions and reaction rate, is presented. In this model, main components of copper concentrate are represented as FeS 2 and CuFeS based on experiment, intermediate products are assumed to be S 2 and FeS, and the final products are assumed as FeS, FeO, SO 2, Cu 2S, FeO and FeO(SiO 2) 2. The model incorporates the transport of momentum, heat and mass, reaction kinetics between gas and particles, and reactions between gas and gas. The k-ε model is used to describe gas phase turbulence. The model uses the Eulerian approach for the gas flow equations and the Lagrangian approach for the particles. The coupling of gas and particle equations is performed through the particle source in cell(PSIC) method. Comparison between the model predictions and the plant measurements shows that the model has high reliability and accuracy. A mathematical model of multistage and multiphase reactions in flash smelting furnace, which based on the description of chemical reactions and reaction rate, was presented. In this model, the main components of copper concentrate are represented as FeS 2 and CuFeS based on experiment, intermediate products are assumed to be S2 and FeS, and the final products are assumed as FeS, FeO, SO2, Cu2S, FeO and FeO (SiO2) 2. The model incorporates the transport of momentum, heat and mass, reaction kinetics between The k-ε model is used to describe gas phase turbulence. The model uses the Eulerian approach for the gas flow equations and the Lagrangian approach for the particles. The coupling of gas and particle equations is performed through the particle source in cell (PSIC) method. Comparison between the model predictions and the plant measurements shows that the model has high reliability and accuracy.