Kinetic study of magnesite decomposition under different CO2 pressure conditions and its application in CFD modeling

Abstract

By systematically investigating the effect of CO₂ on magnesite decomposition, it can provide a more accurate reference for the equipment design of magnesite calcination. In this work, thermogravimetric experiments of magnesite pyrolysis in atmospheres with varying CO₂ pressures, P(CO₂), were performed, and the behavior and kinetic parameters were investigated. A CFD model of the magnesite flash calciner coupled with the kinetic result was then developed. The results of iso-conversional analysis show that the apparent activation energy, E, is significantly increased from 194.49 kJ/mol in N₂ to 305.42 kJ/mol in the atmosphere with P(CO₂)= 50 kPa, demonstrating the inhibition effect of CO₂. The variation in E also suggests that the conventional method struggles to provide a universal kinetic description across different P(CO₂). Therefore, an accommodation function should be introduced to parameterize the effect of the pressure term. The modified kinetic analysis yields a universal kinetic equation with E = 255.77 kJ/mol, kinetic model function f(α)= 1-α, and pressure term h(P)= (P₀/P)^0.355·[1-(P/P_eq)^1.849]. The parameters obtained from thermogravimetric (TG) and micro fluidized bed reaction analyzer (MFBRA) were integrated into the CFD model, yielding accurate results. This study is expected to provide tools and scientific reference for design and optimization of magnesite calcining equipment.