EPCON Multi-Phase Flash™ application allows for the estimation of vapor-liquid equilibria (VLE) or vapor-liquid-liquid equilibria (VLLE) and associated phase properties for mixtures of pure and/or pseudo-components. Properties of pure or pseudo-components and their mixtures are computed with the AIChE DIPPR® and API® database and associated correlations (the DIPPR® Pure Component Database is used for pure component data). The three-phase flash engine enables the user to predict phase splits involving a vapor and two liquid phases, where the second liquid phase (if present) is an aqueous phase. The graphical image on the main screen automatically changes from a vertical to horizontal drum for a 3-phase flash.
The EPCON Multi-Phase Flash™ application interface provides a visual representation of the feed and flash drum for entry of data. When feed conditions are entered they are copied by default as the flash conditions that can be updated by the user. Selection of either Pure or Pseudo components can be made at the bottom of the screen that allows for logical selection and entry of this information. Entry of the mole or mass percent of each pure and pseudo component allows for the flash calculations to be performed. A databank of accurate SRK and NRTL parameters are included that are automatically selected for component pairs -providing high quality 2-phase and 3-phase flash results.
The normal boiling point, specific gravity, and molecular weight of a pseudo component is computed as follows. First the TBP curve is fitted to a cubic spline equation. Volume percent is then computed for each petroleum fraction cut at the beginning and end temperature to determine the amount of material in each cut. The normal boiling point for each cut is also computed from the interval beginning and end temperatures. The specific gravity of each cut is computed from the normal boiling point and the Watson K (assumed constant). The molecular weight is computed from a correlation using normal boiling point and specific gravity. The API gravity is computed directly from specific gravity.