CHARACTERIZATION OF FISCHER-TROPSCH LIQUIDS FOR VAPOR-LIQUID-EQUILIBRIA CALCULATIONS

K-value formulations are developed for use in performing vapor-liquid equilibria (VLE) calculations on Fischer-Tropsch (F-T) systems. Carbon -number-based pseudocomponents are defined with the aid of the Anderso n-Schulz-Flory (ASF) molecular weight distribution. Proper selection o f the number and types of pseudocomponents enables the trade-off which exists between accuracy and computing time to be adequately addressed . The properties of a pseudocomponent are based on a hypothetical 'mod el' component in each carbon-number cut. Solubilities of gases and lig ht hydrocarbons in the liquid phase are calculated from correlations f or the individual solutes in pure n-paraffin solvents, using average c arbon numbers of the liquid phase. Comparisons are made with data for several different F-T reactor compositions and with predictions from l iterature models. The VLE model developed accurately predicts product phase splits, and is superior to other formulations. (C) 1997 Elsevier Science B.V.