A Triethylene Glycol-Water System: A Study of the TEG Regeneration Processes in Natural Gas Dehydration Plants

Natural gas pipeline transportation requires very low water content in the gas stream in order to avoid condensation or hydrate formation. To reach this goal, when triethylene glycol is used to dehydrate natural gas, after the absorption step, triethylene glycol must be regenerated to levels substantially above 98.5-99.0% by weight available from atmospheric distillation of glycol-water mixtures. In order to regenerate triethylene glycol to higher purity levels, some of the methods used require a stripping gas, a solvent, or to perform the distillation under vacuum. Another method to perform a further dehydration of triethylene glycol is the use of a water exhauster, known as Coldfinger, where the vapor in equilibrium with the liquid to be dehydrated is continuously condensed and removed. In the first part of this work, measurements of boiling temperatures are reported for binary mixtures of triethylene glycol and water at pressures of 50, 100, 200, and 400 mmHg. The experimental data obtained were correlated by employing the NRTL model, with temperature-dependent parameters, to express activities in the liquid phase. The fitted NRTL parameters were then used in the Hysys process simulator to perform a process simulation of a natural gas dehydration plant, provided both with a Coldfinger water exhauster and a conventional stripping column for triethylene glycol regeneration.