Abstract—In this work new experimental data on the rate of absorption of CO 2 into PZ activated concentrated aqueous AMP in the temperature range of (323–333) K are presented. Rate activator PZ is used with a concentration of (2–8) wt%, keeping the total amine concentration in the solution at 50 wt%. The vapour-liquid equilibrium (VLE) of CO 2 into aqueous solutions of (AMP+PZ) have also been measured and modeled in order to determine the liquid phase speciation of (AMP+PZ+CO 2 +H 2 O) system and equilibrium CO 2 loading. The theoretical absorption-rate model used to interpret the experimental kinetic data is based on all possible chemical reactions in the liquid phase. The average absolute deviation between the experimental and model results is about 6.8 %. Index Terms—CO 2 capture, 2-Amino-2-methyl-1-propanol, piperazine, diffusion-reaction model. I. INTRODUCTION Growing environmental concerns today for global warming have motivated extensive research activities towards developing more efficient and cost effective processes for CO 2 capture from large point sources of CO 2 , such as power plants, steel plants, etc, since fossil fuel will continue to hold the major role in meeting the global energy demand, which is projected to rise up to 55% by 2030. Amine based regenerative chemical absorption processes have been widely practiced for several years for CO 2 removal from natural gas and synthesis gas streams. But, the major challenges for CO 2 capture from the flue gas of coal based power plants are the large volumetric flow rates of flue gas at essentially atmospheric pressure with large amount of CO 2 at low partial pressures. A common industrial choice is to use 15–30 wt% aqueous mono ethanol amines (MEA) for regenerative absorption of CO 2 . However, this process is very energy intensive due to the high regeneration energy requirement. Besides, high degradation rate and high corrosiveness of MEA contribute further to the increase in the cost of electricity by about 70–80% if MEA based absorption process is implemented for CO 2 capture in a power plant. Thus, improved cost effective processes with lower energy penalty for CO 2 capture from flue gas streams of coal based power plants is essential today in order to implement CO 2 capture in power plants. There is a recent interest in using activated alkanolamine solvents by employing a reaction rate accelerator e.g., piperazine (PZ), a Manuscript received October 18, 2012; revised January 23, 2013. The authors are with the Cryogenic Engineering Centre, Indian Institute of Technology Kharagpur, Kharagpur-721302. India (e-mail: sukantakdash@gmail.com; ssbandyo@hijli.iitkgp.ernet.in) cyclic secondary diamine, in the aqueous alkanolamine solutions. Piperazine activated aqueous sterically hindered amine 2-amino-2-methyl-1-propanol (AMP) for CO 2 capture takes advantage of the high rate of reaction of CO 2 with the rate activator PZ and the high CO 2 loading capacity and lower regeneration energy requirement of AMP. The ability of a solvent for CO 2 capture is governed primarily by the equilibrium solubility of CO 2 in the solvent as well as mass transfer and chemical kinetics characteristics. Increasing the concentration of solvent allows for increased solvent capacity, higher rate of removal of CO 2 and lower circulation rate. Experimental and theoretical investigation of absorption of CO 2 into PZ activated concentrated aqueous AMP is presented here. The rates of absorption of CO 2 into aqueous solutions of (AMP + PZ) have been measured in a wetted wall contactor over the temperature range of (303–333) K. PZ, as an activator, has been used with a concentration of 2–8 wt%, while the concentration of AMP has been kept 42–48 wt% keeping the total amine concentration in the solution at 50 wt%. In keeping with the flue gas condition, the CO 2 partial pressure has been kept in the range (5-15) kPa, while the total pressure for the absorption measurements has been 100kPa. The VLE of CO 2 into aqueous solutions of (AMP+PZ) has also been measured using an equilibrium cell over the temperature range of (303–323) K. The partial pressures of CO 2 for VLE studies were in the range of (0.1–140) kPa. The ENRTL model [1] has been used to determine the CO 2 partial pressure over aqueous concentrated (AMP+PZ) and the liquid bulk concentrations of all chemical species present in the solution at equilibrium. The ENRTL model has been incorporated in the mass transfer-reaction kinetics model, which is capable of predicting gas absorption rates and enhancement factors for absorption of CO 2 into activated amine solvents. II. REACTION SCHEME AND MATHEMATICAL MODEL A. Reaction Scheme The diffusion-reaction model to describe the rates of mass transfer of CO 2 in aqueous blends of PZ and AMP is based on several complex parallel reversible reactions in the liquid phase. When CO 2 is absorbed into an aqueous mixed amine solution of AMP and PZ, the following reactions may take place in the liquid phase [2]. 1 21 2 2 3 CO AMP HO AMPH HCO Κ ,k - + + + ←⎯⎯⎯→ + (1) + + - ⎯ ⎯ ⎯ → ← + + O H PZCOO , O H PZ CO 3 22 2 2 2 k K (2) Carbon Dioxide Capture: Absorption of Carbon Dioxide in Piperazine Activated Concentrated Aqueous 2-Amino-2-Methyl-1-Propanol Sukanta K. Dash and Syamalendu S. Bandyopadhyay 184 DOI: 10.7763/JOCET.2013.V1.42 Journal of Clean Energy Technologies, Vol. 1, No. 3, July 2013