E-PPR78: A proper cubic EoS for modelling fluids involved in the design and operation of carbon dioxide capture and storage (CCS) processes

Abstract

Considering the broad range of operating conditions that typically characterize carbon dioxide capture and storage (CCS) processes, on the one side, and the high number of species that compose the processed streams, on the other, it becomes evident the necessity of disposing of suitable equations of state being able to flexibly represent the complexity of all these thermodynamic systems. To address the growing industrial need for predictive, sufficiently accurate and simple thermodynamic models, the Enhanced-Predictive-PR78 (E-PPR78) equation of state is proposed here as a suitable model for CCS fluids. Currently, the application of the E-PPR78 model is limited to CCS mixtures of CO2, CH4, N2, O2, Ar, H2, H2S, SO2, NO, CO and H2O. The main objective of this work is the extension of the modelling capability of E-PPR78 to mixtures that, besides the mentioned species, could also contain COS, NH3, NO2, N2O4 and N2O. This result is achieved by introducing, with this paper, four new molecular groups for the E-PPR78 model, namely, “COS” (group 28), “NH3” (group 29), “NO2/N2O4” (group 30) and “N2O” (group 31). More specifically, the paper presents, at first, a review of all the available experimental vapor-liquid-equilibrium (VLE) and enthalpy changes on mixing (hM) data for binary systems containing 2 of the following compounds: CO2, CH4, N2, O2, Ar, H2, H2S, COS, SO2, NH3, NO, NO2, N2O4, N2O, CO and H2O. Secondly, the E-PPR78 model is parameterized over these data: not only new group-interaction parameters are determined for the 4 groups added in this study but many parameters are updated over newly available data. Modelling results are analyzed accounting for the complexity of each system, evaluated according to the classification scheme of Van Konynenburg and Scott. Moreover, the capacity of the model to predict ternary data is meticulously discussed. This research thus provides a predictive equation of state, the E-PPR78, being applicable to most of the currently treated CCS fluids, and discusses its strengths and limitations.