High temperature behavior of Na–Fe oxides in H 2O+CO 2 atmosphere

Abstract

The equilibrium states of sodium ferrates in H 2O+CO 2 environments were calculated by using a user database of the Na–Fe–O–H–C system. Chemical potential diagrams as functions of P(O 2) and P(Na) were constructed by Thermo-Calc. The simulation calculation suggested that NaFeO 2 should be the most stable sodium ferrite together with Na 2CO 3 in the atmosphere while other sodium ferrites such as Na 5FeO 4, Na 3FeO 3, etc., would be no longer stable in equilibrium state even if the pressure of CO 2 is very low. However, experiments showed that the reaction of sodium ferrates with CO 2 was a rate-limiting process and the formation of NaOH at the initial period was actually the dominant process instead of that of Na 2CO 3. It indicates that reaction kinetics plays a great role in chemical behaviors of sodium ferrates in H 2O+CO 2 environments.