Charts Using P and T Only

Several such Charts have been developed in the past [Scheibel and Jenny, 1945 Winn (Hadden, 1953) DePriester, 1953]. They give the K values for several light hydrocarbons as functions of the temperature and pressure of the system only. The other components of the mature - and its composition - are not involved. Some average effect is included in the K values, however, since experimental data were used in their construction. In addition, considering the similarity of the compounds involved and the low pressures covered in the Charts, the effect of mixture composition should not be very significant away, of course, from its critical point. 

Since Charts cannot be used with computer calculations, a corresponding states type approach is developed here (Program KVALUE, Appendix E)  

The reference compound, designated with the superscript is n-butane, and values for the parameters in Eqs 14.5.3 and 14.5.5 are presented in Table 14.1. Methane cannot be successfully predicted by Eq. 14.5.1 rather Eqs 14.5.2 and 14.5.3 should be used with the a,-, bf x, c, i and values presented also in Table 14.1. 

and the special expression for methane, provide reasonable estimates of K values for the Cj to Cg hydrocarbons (alkanes and alkenes) in hydrocarbon mixtures - away from the critical point - in the  

Under these limitations the obtained K values are typically to within 5% of those obtained from the DePriester charts or of those for relevant binary systems given by Knapp et al, 1982 (see Problem 14.57). 

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