Noura Dawass

6 130 S OLUBILITY OF G ASES IN M ONOETHYLENE G LYCOL Table 6.4: Henry coefficients of CH 4 , H 2 S and N 2 in MEG obtained from experiments and MC sim- ulation. Experimental values are taken from Refs. [225] , and [177] for CH 4 , and H 2 S, respectively. H i , j , bar/(mol i /mol EG) Solute Experimental MC Simulations CH 4 5673 4504 ± 165 H 2 S–TraPPE 227.4 302 ± 14 H 2 S–KL 227.4 173 ± 5 N 2 – 10815 ± 248 Table 6.5: Ideal selectivities of CO 2 , CH 4 , H 2 S and N 2 in MEG computed using Henry coeffi- cients from experiments and MC simulation at T =373.15 K. Experimental values are taken from Refs. [225] , and [177] for CH 4 , and H 2 S, respectively. S i , j Separation Experimental MC Simulations CO 2 /CH 4 6.73 6.17 CO 2 /H 2 S–TraPPE 0.27 0.41 CO 2 /H 2 S–KL 0.27 0.24 CO 2 /N 2 – 14.81 6.4. C ONCLUSIONS In this chapter, we predict the absorption of CO 2 , CH 4 , H 2 S, and N 2 in MEG us- ing MC simulations in the osmotic ensemble. The CFCMC method was used to facilitate insertions/deletions of molecules into the solvent. The TraPPE force field was used to model all species. For H 2 S, two force fields were compared, i.e. H 2 S-TraPPE and H 2 S-KL. The solubility of CO 2 in MEG was measured at the fol- lowing temperatures: 333.15 K, 353.15 K, and 373.15 K. From experiments and MC simulations, CO 2 was found to be better absorbed at lower temperatures. At T = 373.15 K, CO 2 and H 2 S were found to have higher solubilities in MEG than CH 4 and N 2 . Solubilities predicted by MC simulations are in reasonable agreement with experimental data. For all the solutes studied in this work, de- viations between MC simulations and experiments were found to increase with pressure. For the solubility of H 2 S, predictions from the H 2 S-KL force field were closer to experimental measurements than H 2 S-TraPPE. Other than absorption isotherms, Henry coefficients were also computed. The order of solubilities of the gases in MEG at 373.15 K was found to be as follows: H 2 S > CO 2 > CH 4 > N 2 . The average difference between Henry coefficients from experiments and Henry coefficients from MC simulations is ca. 20%. These results can be regarded sat-