Noura Dawass

6.3. R ESULTS AND DISCUSSION 6 123 Table 6.2: Properties of pure MEG at different temperatures from experiments and MC simula- tions. Density of pureMEG in kg/m 3 obtained fromexperiments [184] andMC simulations at P = 1 bar. The vapor densities and saturated vapor pressures of MEG are computed from µ ex /( k B T ) (see sectio n 6.3.1) . Experimental saturated vapor pressures are obtained from the NIST database [222] . T /[K] ρ L exp /[kg/m 3 ] ρ L sim /[kg/m 3 ] µ ex / k B /[K] ρ V sim /[kg/m 3 ] P sat sim /[bar] P sat NIST /[bar] 333.15 1085 1029.1 ± 20 − 4125 ± 41 4.2x10 − 6 0.022 0.021 353.15 1070.1 1016.3 ± 0.5 − 3948 ± 25 1.4x10 − 5 0.0068 0.0067 373.15 – 1003.3 ± 0.5 − 3749 ± 27 4.3x10 − 5 0.0019 0.0018 (a) (b) Figure 6.2: (a) Typical snapshot of a simulation of MEG in which CO 2 is absorbed in the osmotic ensemble ( T = 333 K, P = 8 bar, N MEG = 220 molecules, and N CO 2 = 3 molecules), in a simulation box with the dimensions 28 x 28 x 28 Å. (b) The same snapshot as in (a) but only showing CO 2 molecules. Figures were produced using the software package iRASPA [223] . of CO 2 to the number of moles of MEG (i.e. loading) is plotted as a function of pressure. Solubilities fromMC simulations were found to qualitatively agree with experimental measurements. Both experiments and simulations show that for all temperatures studied, the loading is almost linear in this pressure range. Ad- ditionally, both methods report that the absorption of CO 2 in MEG decreases at higher temperatures. Figure 6.3 shows that the quantitative agreement between MC simulations and experiments varies with temperature and pressure. At very low pressures (i.e. < 2 bar), loadings of CO 2 obtained fromMC simulations agree well with experiments. At higher pressures, MC simulations overpredict the ab- sorption of CO 2 when compared to experiments. The deviation between sim- ulations and experiments systematically increases with pressure, and decreases with temperature. The inherent uncertainties of the experimental loadings of CO 2 in MEG are shown with vertical error bars. Uncertainties of experimental values are calculated using the methodology described in the work of Wanderley