Development of a thermodynamic database, evaluation of experimental enthalpy departure data, and modeling phase behavior in weak aqueous electrolyte mixtures.

摘要

This study includes two primary objectives: (1) development and organization of a thermodynamic database including an evaluation of the quality of experimental enthalpy departure data, and (2) extension and continued development of a weak electrolyte phase and chemical equilibrium model.; The thermodynamic database is organized into a user-friendly relational database model using Microsoft Access. Statistical analysis of enthalpy departure data compared to equation-of-state predictions allows assessment of data point quality. Over 13,000 enthalpy departure data are evaluated. The analysis identifies less than 1% of all data as being of questionable quality, with a small portion marked as possible outliers. The Peng-Robinson EOS calculates enthalpy departure within 6 Btu/lb for all data, with discernable trends based on types of components. Pure paraffins and binary mixtures of paraffins are more accurately modeled (3.5 Btu/lb) compared to cyclic components and mixtures containing aromatic and/or napthene components (6 Btu/lb). For heterogeneous compounds, both pure components and binary mixtures show wider variations; predictions of enthalpy departures are within 8 Btu/lb of the experimental data.; The improvements to a weak electrolyte equilibrium model have been incorporated into a phase behavior-modeling framework. Regression of EOS coefficients from binary electrolyte-water mixtures leads to data correlations within experimental uncertainty. Equilibrium predictions for mixtures of a weak electrolyte and strong electrolytes are accurate to ionic strengths up to 12 molar for the weak electrolytes carbon dioxide, hydrogen sulfide, sulfur dioxide, ammonia, and hydrogen cyanide. Less accurate predictions are obtained for mixed weak electrolytes, without the introduction of additional model parameters. (Abstract shortened by UMI.)