TABLE OF CONTENTS One of the most important engineering problems encountered in modeling chemical and petroleum processes is the multiphase flash problem. The present flash algorithm can be used to calculate phase equilibria for multicomponent systems with three coexisting phases (water, oil, and gas) at equilibrium with both simplicity and accuracy (Mokhatab, 2003).
This three-hase flash algorithm is based on the thermodynamic condition of equal fugacities for each component in each phase. The resulting phase compositions then provide better values for updating the distribution coefficients using an equation of state (EOS). Equations of state have been used successfully to describe the phase behavior of reservoir crude and gas condensates, but the phase behavior of water/reservoir crude oil has not yet been predicted successfully by an EOS. In this study, it is demonstrated that using the present algorithm with the Shinta and Firoozabadi (1995) association model provides reliable and better results in comparison with experimental data for three-phase flash calculation in the vapor-liquid-liquid region.
A generalized model of a three-phase equilibrium system is shown in Figure A1-1. The phases are assumed to be in thermodynamic equilibrium with each other and any component can appear in all three phases.
The overall and component material balance around the flash tank gives
where F is total moles of feed, lbmole; L A is total moles of hydrocarbonrich liquid, lbmole; L B is total moles of water-rich liquid, lbmole; V is total moles of...
