Thermodynamic Study of the Corrosion of Refractories by Sodium Carbonate.

The corrosion of refractories by sodium salts in waste liquid at high temperature has become a serious problem. This paper focuses on the thermodynamic characterization of sodium carbonate (Na₂CO₃) corrosion of six refractories by FactSage modelling in combination with X-ray diffraction (XRD). Three of the refractories are oxides (Fe₂O₃, Al₂O₃, and Cr₂O₃), and the other three are synthetics spinels (magnesium chromium, MgO·Cr₂O₃; magnesioferrite, MgO·Fe₂O₃; and, magnesium aluminium, MgO·Al₂O₃). First, thermodynamic simulations were carried out with the FactSage thermodynamics model using the reaction package to predict the direction of the Na₂CO₃ corrosion reaction in terms of the Gibbs free energy. Then, the reactions between the six refractories and Na₂CO₃ were conducted through a series of refractories/Na₂CO₃ reaction tests. The XRD analytical method was used to describe and understand the chemistry and interpret mineral matter transformation. The products of the tests were also determined by X-ray diffraction and the experimental observations were compared with the results of the thermodynamic simulations. Furthermore, the strength of sodium corrosion of the refractory materials was comprehensively discussed. The results show that MgO·Al₂O₃ has the best thermal stability and it is hard to corrode by Na₂CO₃, while the chrome-containing refractory reacts easily with Na₂CO₃ with a considerably high amount of corrosion product at a temperature of 600 °C. These experimental results are in agreement with the thermodynamic calculations.