By Marcus Hilliard Gary T. Rochelle The University of Texas at Austin A Predictive Thermodynamic Model for an Aqueous Blend of Potassium Carbonate, Piperazine, and Monoethanolamine for Carbon Dioxide Capture from Flue Gas By Marcus Hilliard Gary T. Rochelle The University of Texas at Austin

This research addresses the use of carbon capture from coal fired power plants to reduce factors contributing to global warming Our aim is to understand the fundamental thermodynamic behavior associated with the post-combustion chemical absorption process Chemical Solvents Monoethanolamine (MEA) Increase in capacity, faster rates, robustness MEA/Piperazine (PZ) K2CO3/PZ background – carbon capture technologies

process - aqueous absorption Cooler 2-4 mol H2O/mol CO2 Clean Gas 1% CO2 process - aqueous absorption Absorber 40–60oC 1 atm Stripper 100–120oC 1-2 atm Rich Solvent Lean Solvent Flue Gas 10% CO2 Reboiler

needs for thermodynamics Mass Transfer Driving force Capacity Speciation [amine]  kinetics Calorimetry Cp DHabs Volatility Amine P* …with solvent characterization through rigorous modeling

research objective Development of a rigorous thermodynamic model for the H2O-K2CO3-MEA-PZ-CO2 sub-component base systems Cullinane (2005) Tosh et al. (1959) Numerous Authors UNIFAC Bishnoi (2000) Perez-Salado Kamps et al. (2003) Derks et al. (2005) Jou et al. (1995) Dang (2001) and Okoye (2005)

aqueous chemistry Complex Mass Transfer with Chemical Reactions CO2 Solubility Liquid Phase Vapor Phase Amine Volatility aqueous chemistry NMR Speciation Specific Heat

aspen plus 2006.5 framework Enthalpy Phase Equilibrium ─ Aqueous Chemistry

elecNRTL model Activity coefficient model in Aspen Plus 2006.5 Rigorously represents liquid and vapor phases Reference state convention: Inf. Dil. Aqu. phase for molecular solutes (i.e. CO2) and ions Pure liquid for molecular solvents (i.e. H2O and MEA) By adjusting binary interaction parameters Through sequential non-linear regressions with multiple, independent data sets

international collaboration Apparatus at NTNU High P CO2 Solubility (100 – 120 oC) Calorimeter  (40 – 120 oC) Measured by Inna Kim (NTNU) Apparatus at UT ATM P Reactor (30 – 70 oC) (multi-component vapor phase analysis reactor) Differential Scanning Calorimeter: Specific Heat Capacity & PZ Solubility NMR Speciation (Chem dept.) Measured by Steve Sorey and Jim Wallin X-ray Diffraction (Chem dept.) Crystallization Identification Measured by Vince Lynch

experimental design - overall 52 Systems 9,757 data points

sequential regression

CO2 Solubility in 7m MEA at 40 oC Austgen (1989) Freguia (2002) Jou et al. (1995) This work Lee et al. (1976) - corrected

CO2 Solubility in 2 and 5 m PZ at 40 - 60 oC Solid Pt & Curves : 2 m PZ Open Pt & Curves : 5 m PZ

CO2 Solubility in 5 m K+/2.5 m PZ 60 40 oC 80 oC 60 40

MEA Volatility in 7 m MEA at 40oC 64 ppmv Austgen (1989) This work

MEA Volatility at 40oC ~15 % 5 m K+ + 7 m MEA ~50 ppmv 7 m MEA + 2 m PZ 7 m MEA 5 m K+ + 7 m MEA + 2 m PZ

PZ Volatility in 2 m PZ at 40oC Hilliard (2005) 25 ppmv This work

PZ Volatility at 40oC ~30 % 2 m PZ ~20 ppmv 5 m K+ + 2 m PZ 7 m MEA + 2 m PZ 5 m K+ + 7 m MEA + 2 m PZ

CO2 Solubility in 7m MEA at 60oC Differential Capacity Austgen (1989) Freguia (2002) Jou et al. (1995) Differential Capacity This work Lee et al. (1976) - corrected

Differential Capacity wrt PCO2 (0.01 – 1.0 kPa) at 60oC H2O-MEA-CO2 H2O-MEA-PZ-CO2 H2O-K2CO3-MEA-PZ-CO2 H2O-K2CO3-PZ-CO2 H2O-K2CO3-MEA-CO2 H2O-PZ-CO2

C13 NMR Speciation for 7 m MEA at 40oC MEA + MEAH+ MEACOO-1 MEA HCO3-1 + CO3-2 Solid Pt: Poplsteinovo (2004) Open Pt: This work Solid Curves: This work

H1 NMR Speciation for 1.5 m PZ at 40oC PZ + PZH+1 H+1PZCOO-1 + PZCOO-1 PZ PZ(COO-1)2 Points: Ermatchkov et al. (2003) Curves: This work

Enthalpy of CO2 Absorption in 7 m MEA at 40 and 120oC Kim and Svendsen (2007) 40oC This Work

Enthalpy of CO2 Absorption in 2.4 m PZ at 40 and 120oC Kim (2007) 40oC This Work

Enthalpy of CO2 Absorption Predictions at 40 and 120oC 7 m MEA 2.4 m PZ 6 m K+ + 1.2 m PZ 5 m K+ + 2.5 m PZ

Specific Heat Capacity Results for loaded 7 m MEA H2O a = 0.0 a = 0.139 a = 0.358 a = 0.541 MEA

Specific Heat Capacity Refinement for loaded 7 m MEA

Specific Heat Capacity Refinement for loaded 2 m PZ

SLE Results for Mixtures of H2O-PZ using DSC Liquid Solution Bishnoi (2002) 10 m PZ PZ (s) 25 m PZ This work 20 m PZ PZ∙6H2O (s)

unit cell of K2PZ(COO)2 COO- complex SEM image PZ Crystal Size: 0.43 x 0.33 x 0.08 mm K

SLE Results for K+ + PZ Solutions KHCO3 (s) K2PZ(COO)2 (s) 5 m K+ + 3.6 m PZ 5 m K+ + 2.5 m PZ 6 m K+ + 1.2 m PZ

Systems Exhibiting SLE Behavior for K+ + PZ Solutions 6 m K+ + 1.2 m PZ 5 m K+ + 3.6 m PZ 5 m K+ + 2.5 m PZ

In this work: Developed a new VLE apparatus = PCO2, PAmine, PH2O At typical lean absorber conditions: PMEA = 64 ppmv PPZ = 25 ppmv Amine blends illustrate an enhanced capacity over MEA Enthalpy of CO2 absorption increased in temperature Successfully measured Cp in loaded solutions between 40 and 120oC  Cp of CO2 may be negligible in loaded MEA and PZ Inferred a possible operating region for CO2 capture utilizing aqueous PZ. Identified and determine the solubility of K2PZ(COO)2 present in K+/PZ solutions Created a consistent rigorous thermodynamic model that adequately predicts solubility, volatility, speciation, and calorimetry in the base sub-component H2O-K2CO3-MEA-PZ-CO2 systems within Aspen Plus® 2006.5 summary

This concludes my presentation… Thank you for your attention.