Simplified Estimation of Regeneration Energy of 30 wt % Sodium Glycinate Solution for Carbon Dioxide Absorption

Abstract

A simple method for estimating the regeneration energy of CO2 absorption was devised. The regeneration energy of a 30 wt % sodium glycinate (SG) solution was calculated by the summation of the enthalpy of reaction, the sensible heat and the heat of vaporization. Each form of heat energy was determined experimentally. Solubilities of carbon dioxide in the SG solution was determined by gas chromatography (GC) analysis for the gas phase with the help of a virial equation for the liquid phase in the temperature range of 40−120 °C. Heat capacity of the solution was measured by a differential scanning calorimeter (DSC) and was used to calculate sensible heat. The heat of vaporization was evaluated by applying the Clausius−Clapeyron equation to 20 data points of vapor pressure. All of the experiments were carried out with either a 30 wt % aqueous solution of SG or the same concentration of monoethanolamine (MEA). Regeneration energy of the SG solution was found to be higher than that of the MEA solution by about 1000 kJ/kg of CO2. From the CO2 solubility data it was observed that SG had a higher capacity to absorb carbon dioxide than MEA even at the regeneration temperature (120 °C). In addition, the 30 wt % basis SG demonstrated a reduction in cyclic capacity at this regeneration temperature. So, our main effort is to establish a reasonable method for estimating CO2 absorbent regeneration energy along with the regeneration energy of 30 wt % aqueous solutions of SG.