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 (Na(2)CO(3)) corrosion of six refractories by FactSage modelling in combination with X-ray diffraction (XRD). Three of the refractories are oxides (Fe(2)O(3), Al(2)O(3), and Cr(2)O(3)), and the other three are synthetics spinels (magnesium chromium, MgO·Cr(2)O(3); magnesioferrite, MgO·Fe(2)O(3); and, magnesium aluminium, MgO·Al(2)O(3)). First, thermodynamic simulations were carried out with the FactSage thermodynamics model using the reaction package to predict the direction of the Na(2)CO(3) corrosion reaction in terms of the Gibbs free energy. Then, the reactions between the six refractories and Na(2)CO(3) were conducted through a series of refractories/Na(2)CO(3) 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·Al(2)O(3) has the best thermal stability and it is hard to corrode by Na(2)CO(3), while the chrome-containing refractory reacts easily with Na(2)CO(3) with a considerably high amount of corrosion product at a temperature of 600 °C. These experimental results are in agreement with the thermodynamic calculations.