1 Research Review Meeting, Austin, 10-11/I-2008 Thermal measurements: Heat of absorption of CO 2 and Vapour-Liquid Equilibria in alkanolamine-water solutions Inna Kim and Hallvard F. Svendsen Norwegian University of Science and Technology (NTNU) Trondheim, NORWAY

2 Research Review Meeting, Austin, 10-11/I-2008 Outline Heat of absorption –Background –Experimental set-up –Results Vapour-Liquid Equilibria –Experimental set-up –Results Summary Further work

3 Research Review Meeting, Austin, 10-11/I-2008 Heat of absorption, ∆H abs

4 Research Review Meeting, Austin, 10-11/I-2008 Integral vs differential ∆H abs Calculated using Gibbs-Helmholz equation : f CO2 – fugacity of CO 2 x CO2 – mole fraction of CO 2 Integrated over some loading interval (direct measurement)  Assumption:  Disadvantage: differentiation Isothermal flow calorimeter [ Background

5 Research Review Meeting, Austin, 10-11/I-2008 Differential ∆H abs data from solubility measurements 1 VLE data: ln(p CO2 ) vs 1/T: a)Fitted with a line, b)Fitted with a 2 nd order polynomial a b 1 [Hoff K.A., Mejdell T., Svendsen H.., 2005] Background

6 Research Review Meeting, Austin, 10-11/I-2008 Impact of temperature and loading on ∆H abs 2 Temperature profile for the Dome 5 North Caroline plant 2 Background “The increase in heat of absorption of up to 20% from the absorber to the stripper temperature may cause a deficient duty calculation with the reboiler if a constant heat of absorption at the lower value is used” 2 2 [Jerry A. Bullin et al., Bryan Research & Engineering Inc. Bryan, TX, GPA 2007]

7 Research Review Meeting, Austin, 10-11/I-2008 Experimental set-up CPA122 (ChemiSens AB, Sweden) 1 - Calorimeter 2a,2b - CO 2 storage cylinders 3 - Vacuum pump 4 - Feed bottle

8 Research Review Meeting, Austin, 10-11/I-2008 Semi-differential ∆H abs (an example of on-line data)

9 Research Review Meeting, Austin, 10-11/I wt% Monoethanolamine (MEA) Results

10 Research Review Meeting, Austin, 10-11/I wt% N-methyldiethanolamine (MDEA) Results

11 Research Review Meeting, Austin, 10-11/I and 50 wt% MDEA Results

12 Research Review Meeting, Austin, 10-11/I M Diethylenetriamine (DETA) Results

13 Research Review Meeting, Austin, 10-11/I M DETA + 1.5M H 2 SO 4 Results

14 Research Review Meeting, Austin, 10-11/I-2008 ∆H abs with different amines at 40 o C Results

15 Research Review Meeting, Austin, 10-11/I-2008 ∆H abs with different amines at 120 o C Results

16 Research Review Meeting, Austin, 10-11/I-2008 VLE measurements

17 Research Review Meeting, Austin, 10-11/I-2008 Experimental set-up 1.Ebulliometer 2.Pressure controller 3.Thermocouples 4.Cold trap 5.Buffer vessel 6.Vacuum pump

18 Research Review Meeting, Austin, 10-11/I-2008 Validation of the experiments: vapour pressure of pure water

19 Research Review Meeting, Austin, 10-11/I-2008 MEA (1) - H 2 O (2) Results

20 Research Review Meeting, Austin, 10-11/I-2008 P-xy diagram: MEA(1)-H 2 O(2) ○ this work (40, 60,80,100 o C) * Nath et al., 1983 (60, 78, 92 o C) — Wilson equation Wilson parameters º º º Results

21 Research Review Meeting, Austin, 10-11/I-2008 Activity coefficients: MEA(1)-H 2 O(2) ○ this work (40, 60,80,100 o C) * Nath et al., 1983 (60, 78, 92 o C) — Wilson equation Results

22 Research Review Meeting, Austin, 10-11/I-2008 MDEA (1) - H 2 O (2) Results

23 Research Review Meeting, Austin, 10-11/I-2008 P-xy diagram: MDEA(1)-H 2 O(2) ○ this work (40, 60, 80, 100 o C) — Wilson equation Wilson parameters 40ºC ºC ºC ºC Results

24 Research Review Meeting, Austin, 10-11/I-2008 Activity coefficients: MDEA(1)-H 2 O(2) ○ this work (40, 60, 80, 100 o C) — Wilson equation Results

25 Research Review Meeting, Austin, 10-11/I-2008 Ternary mixture: MEA(1)-MDEA(2)-H 2 O(3) Results

26 Research Review Meeting, Austin, 10-11/I-2008 Activity coefficients: MEA(1)-MDEA(2)-H 2 O(3) Results

27 Research Review Meeting, Austin, 10-11/I-2008 Thermodynamic consistency test Results 3 [Van Ness H.C. et al, Am.Inst.Chem. Eng.J.19 (1973) ] 4 [Van Ness H.C., Pure & Appl. Chem., Vol. 67, No.6, pp , 1995] Point to point test 3 Area test 3

28 Research Review Meeting, Austin, 10-11/I-2008 Summary A method proposed for measuring the enthalpy of absorption differential in temperature and semi-differential in loading Amine concentration and experimental pressure found to have less effect on the heat of absorption data (within the experimental range of this work) than temperature and loading The ebulliometer enables very accurate determination of the vapour-liquid equilibrium of pure components and mixtures Experimental activity coefficients of amines and water can be calculated The accuracy of the results obtained is limited only by the purity of the substances used and by the precision of the analytical methods used for the sample

29 Research Review Meeting, Austin, 10-11/I-2008 Further work Fitting the heat of absorption data using K-values and temperature dependent activity coefficients Fitting VLE data with UNIFAC equation of state Improvement of the thermodynamic models of the acid gas- alkanolamine-water systems using the data measured in this work, along with the other experimental data taken from the literature

30 Research Review Meeting, Austin, 10-11/I-2008 THANK YOU for your attention!