Validation of an Equilibrium-Stage Model of the Coldfinger Water Exhauster for Enhanced Glycol Regeneration in Natural Gas Dehydration

Abstract

A model of the Coldfinger water exhauster for advanced glycol regeneration, based on two-equilibrium stages with internal recirculation of vapor, is proposed and validated on plant data of natural gas dehydration using triethylene glycol (TEG). Optimal operating regions are located for vapor recirculation ratios (𝛼𝛼) above 0.95, gas-to-liquid feed ratios in the order of 10 -4 and top temperatures in the range 50 to 80 °C. The conceptual investigation supports that the Coldfinger unit can enhance TEG purity up to approximately 99.7 wt %. Taking conventional single-stage gas stripping as reference, the model supports the possibility of achieving the same TEG enrichment levels using 10 to 100 times less gas. Non-obvious features are also highlighted, such as multiple steady-states and conditions leading to low or negative efficiency. The model provides a good fit with plant data with optimal values of 𝛼𝛼 (regression parameter) being consistent and bearing sound physical meaning.