Thermodynamic and kinetic properties of NH3-K2CO3-CO2-H2O system for carbon capture applications

An innovative solvent based on the quaternary system CO2-NH3-K2CO3-H2O is reported and characterized in terms of its thermodynamic properties and rate of CO2 absorption. Thermodynamic properties of the solvent such as vapor-liquid equilibrium, solid-liquid equilibrium, and the heat of desorption were modelled with the Extended UNIQUAC thermodynamic model. The kinetics of CO2 absorption in the solvent were studied experimentally with a wetted wall column set-up. The absorption rate was investigated with respect to temperature, ammonia concentration, potassium carbonate concentration, and CO2 loading, under the typical operating conditions of a capture plant. Globally, the solvent has a number of interesting properties for CO2 capture applications. Indeed, adding K2CO3 to the ammonia solvent reduced both the ammonia slip and the heat of desorption. Experimental analysis showed that the kinetics of absorption were mainly influenced by the reaction between free ammonia and CO2. Hence, the overall mass transfer coefficient decreased when increasing the K2CO3 content of the solvent.