Triethylene glycol regeneration in natural gas dehydration plants: a study on the Coldfinger process

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 (TEG)
is used to dehydrate natural gas, after the absorption step TEG 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 TEG to higher purity levels some of the
methods used require a stripping gas, a solvent or to perform the distillation under vacuum. A
simpler method to perform a further dehydration of TEG is the use of a water exhauster,
known as Coldfinger, where the vapour in equilibrium with the liquid to be dehydrated is
continuously condensed and removed. In this work, the Coldfinger apparatus was modelled
and a study on the most relevant operating parameters was carried out. A process simulation
of a natural gas dehydration plant, provided with a Coldfinger water exhauster for TEG
regeneration, was performed on a case study. It was shown that the dehydration process
with Coldfinger unit is capable of reaching current water content specifications in a simple
and economic way.