Thermodynamics and Kinetics of Aqueous Piperazine with Potassium Carbonate for Carbon Dioxide Absorption. Topical Report, January 1, 2005-March 31, 2005.
This work proposes an innovative blend of potassium carbonate (K(sub 2)CO(sub 3)) and piperazine (PZ) as a solvent for CO(sub 2) removal from combustion flue gas in an absorber/stripper. The equilibrium partial pressure and the rate of absorption of CO(sub 2) were measured in a wetted-wall column in 0.0 to 6.2 m K(sup +) and 0.6 to 3.6 m PZ at 25 to 110 C. The equilibrium speciation of the solution was determined by (sup 1)H NMR under similar conditions. A rigorous thermodynamic model, based on electrolyte non-random two-liquid (ENRTL) theory, was developed to represent equilibrium behavior. A rate model was developed to describe the absorption rate by integration of eddy diffusivity theory with complex kinetics. Both models were used to explain behavior in terms of equilibrium constants, activity coefficients, and rate constants. The addition of potassium to the amine increases the concentration of CO(sub 3)(sup 2-)/HCO(sub 3)(sup -) in solution.