Thermal Decomposition of Sodium Hydrogen Carbonate and Textural Features of Its Calcines

Abstract

The decomposition rate of sodium hydrogen carbonate (NaHCO3) into carbonate (Na2CO3) was determined as weight loss at ambient pressure and elevated temperatures up to 230 °C. A particularly slow increasing-temperature procedure and small samples of fine powders were employed to minimize heat and mass transfer intrusions. Efficient removal of the gaseous products eliminated possible equilibrium constraints. A near-first-order reaction rate equation has been presented for the decomposition reaction and also verified by the data collected by experiment in a constant-temperature mode. This correlation makes it possible to predict the reaction rate as a function of temperature and the extent of decomposition. In combination with its integrated form, it can readily be used, for example, in modeling or design of the decomposition process. Experimental measurements show that the porosity of parent (precursor) solids persists during the calcination process. It is believed that such a highly alkaline porous reactan...