No abstract

A technical equation of state (EoS), according to the perturbed chain statistical associating fluid theory (PC-SAFT), is developed for solvent blends composed of polyethylene glycol dimethylethers (PEGDMEs/glymes), that is, CH 3 O[CH 2 CH 2 O] n CH 3 with n = 3, ..., 9. These solvent blends are employed in industry under the commercial names Selexol or Genosorb, primarily for the physical absorption of H 2 S and CO 2 from acid gases. The molecular parameters for the EoSs of the pure fluids comprising the solvent, notably for the n = 3 and 4 members of the homologous series, are obtained by fitting the PC-SAFT EoS to published vapor pressure and liquid density data. Because of the limited availability of experimental data for the glymes with n ≥ 5, PC-SAFT is used as a predictive tool to determine the molecular parameters for the n = 5, ..., 9 members of the homologous series. To exploit the extrapolative capabilities of PC-SAFT, the n = 1 and 2 members of the homologous series are included in this study. The mixture of glymes is modeled using the van der Waals one-fluid mixing rules with the Lorentz− Berthelot combining rules, whereby the binary interaction parameters k ij among the members of the homologous series are all set to zero. The performance of the mixture EoS is assessed by a comparison of predicted properties with experimental data. The thermodynamic model is also briefly applied to describe the vapor−liquid equilibrium behavior of glymes and their blends with CO 2 . The comparison with available experimental data shows that the resulting model provides a description of the thermodynamic behavior of this system suitable for engineering purposes.

Closed Brayton gas and supercritical cycles operating with mixtures of carbon dioxide and hydrocarbons, in particular mixture with a low content (5–15%) of benzene, were studied. Totally, supercritical cycles and condensation cycles were looked at and a comparison was made with pure carbon dioxide cycles with a minimal temperature around 40–50C (typical minimum temperatures of air cooled radiators). First and second law cycle efficiencies were considered and analysed. Critical point calculations of several mixtures were performed by means of an accurate model for the thermo- dynamic properties and compared with experimental data from literature. For the cycle calculations, a simpler model with classical mixing rules was used because the results were in sufficient agreement. The cycles operating with mixtures showed lower maximum pressures and higher cycle efficiencies compared to the pure carbon dioxide cycles. Taken into account, the high global warming potential of fluorinated fluids and the high flammability and high volume expansion ratios of comparable Rankine toluene cycles, mixtures of carbon dioxides and hydrocarbons exposed promising features

This paper presents the development of a system model for a pre-combustion CO 2 capture process as part of an integrated gasification combined cycle power plant. This process entails the modelling of highly non-ideal, two-phase multi-component mixtures which are currently not supported by available Modelica media libraries or interfaces.Therefore, an interface prototype was developed and tested for the modelling and simulation of the CO 2 capture process. Limitations concerning the modelling approach and improvements targeting the computational efficiency are discussed. Recommendations about the design of a library for the use of external property estimation code in Modelica conclude the treatment.