Wax Solubility in Gaseous System: Thermodynamic Consistency Test of Experimental Data

Wax deposition from natural gas can cause severe problems in production, transmission and processing operations. Accurate knowledge of wax solubility in natural gas system is required to avoid operating problems. Unfortunately, experimental measurements of solubilities of these compounds in gaseous systems are quite challenging. This is partly because concentrations of these solid substances in the gas phase are extremely low; this generally may result in generation of highly uncertain experimental data. In this paper, we present a thermodynamic consistency test based on the Gibbs−Duhem equation to determine the reliability of experimental solubility data of paraffin waxes (n-C24H50 to n-C33H68) available in the open literature. This test uses the Peng−Robinson equation of state and two-fluid van der Waals (vdW2) mixing rules to represent the solubilities of solid waxy compounds in supercritical CO2 and ethane. The results show that all the investigated experimental data that are well represented by the applied thermodynamic model seem to be thermodynamically consistent.