Modeling of the Coldfinger water exhauster for advanced TEG regeneration in natural gas dehydration

The performance of natural gas dehydration using triethylene glycol (TEG) strongly depends on the purity level of TEG in the regeneration unit. Coldfinger is a TEG regeneration technology reported to be capable of increasing TEG purity to levels above 99.8 wt.%, but conceptual models of this equipment appear to be lacking. This work presents a methodology for modeling Coldfinger, where the equipment is represented as two theoretical equilibrium stages operating at different temperatures in the presence of internal vapor recirculation. The key parameters governing the functioning of the equipment are discussed on the basis of a series of simulations carried out for different top temperatures and internal recirculation ratios. The results demonstrate that a regeneration of TEG up to approximately 99.9 wt.% is achievable by injecting smalls amounts of dry gas, considerably lower than conventional enhanced TEG regeneration by gas stripping.