HR: 1330h
AN: A13A-12    [Abstracts]
TI: Computational Methods for Multi-phase Multi-reaction Thermodynamical Equilibrium Problems
AU: * Caboussat, A
EM: caboussat@math.uh.edu
AF: University of Houston, Department of Mathematics,, 4800 Calhoun Rd, Houston, TX 77204-3008
AU: Amundson, N R
EM: amundson@uh.edu
AF: University of Houston, Department of Mathematics,, 4800 Calhoun Rd, Houston, TX 77204-3008
AU: He, J
EM: jiwenhe@math.uh.edu
AF: University of Houston, Department of Mathematics,, 4800 Calhoun Rd, Houston, TX 77204-3008
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AU: Yoo, K
EM: kyyoo@snut.ac.kr
AF: Department of Chemical Engineering, Seoul National University of Technology, Seoul, Korea,
AB: The computation of phase and chemical equilibria of aqueous organic electrolytes mixtures is of significant interest in atmospheric aerosol modeling. The presence of organic species in solution may substantially influence the phase transitions of the deliquescence and efflorescence of salts with changes in relative humidity. Dissolved electrolytes can have appreciable effects on the solubility of organic components in solution. We present here some computational methods for the prediction of the physical state of atmospheric particles. In the case of inorganic aerosols, an Extended UNIQUAC model is used to compute the excess of Gibbs Free energy. Our method is derived from the minimization of the total Gibbs energy. The computational difficulty is to identify the solid phases existing at the equilibrium. Our algorithm is based on a primal-dual active sets-Newton method for the solution of the Karush-Kuhn-Tucker (KKT) conditions. The inequality constraints are tracked at each iteration so that possible solid salts remain sub-saturated. The corresponding inequality constraint becomes active when the saturation is reached. In the case of organic aerosols, liquid-liquid and liquid-solid equilibria as well as phase stability and separation are considered. The UNIFAC model is used for the calculation of activity coefficients for aqueous organic mixtures. We propose a primal-dual interior-point Newton method to solve the KKT conditions of a relaxed minimization problem. We present numerical results for both inorganic and organic problems to show the ability of our approach, in the prediction of aerosol phases in the atmospheric particles.
DE: 0305 Aerosols and particles (0345, 4801)
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly