Meng-Hui Li

Calculation of equilibrium solubility of carbon dioxide in aqueous mixtures of monoethanolamine with methyldiethanolamine

Abstract Li M.H. and Shen K.-P., 1993. Calculation of equilibrium solubility of carbon dioxide in aqueous mixtures of monoethanolamine with methyldiethanolamme. Fluid Phase Equilibria, 85: 129-140. The equilibrium solubility of carbon dioxide in aqueous mixtures of monoethanolamine (MEA) with methyldiethanolamine (MDEA) has been correlated on the basis of the model of Kent and Eisenberg. The chemical equilibrium constants involving alkanolamines are expressed as functions of temperature, amine concentration and carbon dioxide loading. The constants in the model were determined by fitting to the solubility data of carbon dioxide in aqueous MEA/MDEA solutions for temperatures ranging from 40 to 100°C and for partial pressures of carbon dioxide up to 2000 kPa. Satisfactory results were obtained for calculations of the solubility of carbon dioxide in aqueous MEA/MDEA solutions for the systems tested. When performing the solubility calculations for the systems which are not included in the database, the model predicts reasonably well the solubility of carbon dioxide in aqueous MEA/MDEA solutions.

Heat capacity of aqueous mixtures of diethanolamine with 2-amino-2-methyl-l-propanol

Heat capacities of aqueous mixtures of monoethanolamine with 2-amino-2-methyl-l-propanol were measured from 30 °C to 80 °C with a differential scanning calorimeter (DSC). The heat capacities of 2-amino-2-methyl-l-propanol, 2-amino-2-methyl-l-propanol + water, and monoethanolamine + 2-amino-2-methyl-l-propanol were also studied. Eight binary systems and sixteen ternary systems were studied. The estimated uncertainty of the measured heat capacities is ±2%. An excess molar heat capacity expression using the Redlich−Kister equation for the composition dependence is used to represent the measured Cp of aqueous alkanolamine solutions. The results (AAD %, the average absolute percentage deviation) for the calculation of the excess molar heat capacities are 3.6% and 13.2% for the binary and ternary systems, respectively. The heat capacities of aqueous mixtures of monoethanolamine with 2-amino-2-methyl-l-propanol presented in this study are, in general, of sufficient accuracy for most engineering-design calculations.

Application of generalized van der Waals theory and approximations of radial distribution functions to the development of mixing rules

Abstract Li, M.-H. and Huang, F.-N., 1994. Application of generalized van der Waals theory and approximations of radial distribution functions to the development of mixing rules. Fluid Phase Equilibria , 96: 155-172. Based on generalized van der Waals partition function theory and approximations of radial distribution functions, mixing rules for the attractive part of an equation of state have been presented for extension of an augmented hard-core equation of state to mixtures. Two approximations, the van der Waals one-fluid approximation and the mean density approximation, are applied in this study. Within the framework of the conformal solution theory, the properties of a hypothetical fluid were calculated from the attractive part of an augmented hard-core equation of state. As a preliminary test of the method, an augmented hard-sphere equation of state has been applied. For polar systems in which components do not differ appreciably in size, both the MDA and the VDW models yield satisfactory results for the vapor-liquid equilibrium calculations. However, for strongly non-ideal fluid systems, the MDA is superior to the VDW. Adopting the mixing rules for the repulsive hard-core mixtures to describe structure effects, the proposed method can, in principle, be used to extend any accurate augmented hard-core equation of state to mixtures.

Application of approximations to mixture radial distribution functions to the development of mixing rules

Abstract Li M.-H. and Wang Y.-L., 1992. Application of approximations to mixture radial distribution functions to the development of mixing rules. Fluid Phase Equilibria, 72: 89-110. The mixing rules utilizing the approximations for mixture radial distribution functions have been presented for extension of an equation of state of polar fluids to mixtures. The van der Waals one-fluid approximation and the mean density approximation (MDA) for radial distribution functions in a mixture have been applied to derive mixing rule models. To investigate further the composition dependence of the MDA, the composition-dependent cross-interaction energy parameter is also introduced; the resulting model is referred to as the modified mean density approximation (MMDA). In calculations of the vapor-liquid equilibria for non-ideal fluid mixtures, satisfactory results were obtained by the MMDA. When performing the vapor-liquid equilibrium calculations for systems with data over a wide range of temperatures, the MMDA also yielded reasonable results. Furthermore, the proposed method can be used to extend any existing accurate corresponding-states-type pure-fluid equation of state to mixtures.

Heat Capacities of Aqueous Ternary Mixtures of 2-Amino-2-Methyl-1, 3-Propanediol + Piperazine or Lithium Bromide

In this work, we reported the molar heat capacities, CP, of aqueous solutions of the sterically hindered amines 2-amino-2-methyl-1, 3-propanediol (AMPD), and its aqueous ternaries containing piperazine (PZ) or lithium bromide (LiBr). Measurements were performed in the temperature range 303.15 K to 353.15 K and atmospheric pressure by heat flow differential scanning calorimetry. The excess molar heat capacities, CP E , of the binary solutions were determined, and the data were represented as function of temperature and composition using a RedlichKister-type equation. The CP of the ternary mixtures was correlated with temperature and amine concentration using the Sohnel and Novotny equation. Results showed that the calculated data agree very well with experimental CP values at average absolute deviation values of less than 0.2%.