Glycol Dehydration

Glycol dehydration is another absorber-regenerator process that lends itself admirably to analysis by rate-based modeling.  The most common dehydration agent is triethylene glycol (TEG) although mono- and di-ethylene glycols are also used from time to time.  Water is removed from the gas in the absorber and the water-laden solvent is stripped of its water content in a reboiled regenerator.

Absorber performance is measured by the water contend of the dried gas (e.g., lb water per MMSCF of gas) and is controlled by the residual moisture in the lean solvent and, because of the extremely low L/G ratio, treating is controlled also by the temperature of the feed gas and not so much by the lean solvent temperature.

Residual moisture content of the lean solvent is determined in the regenerator.  The regenerator is invariably a reboiled column, usually packed with structured packing to minimize pressure drop and maximize exposed area for water removal by evaporation.  Unfortunately, there is little or no diluting species so the ability of a reboiled regenerator to function alone satisfactorily in this application is rather limited.  Sometimes performance is enhanced by using a Stahl column.  We have even proposed using a Stahl column alone, without a reboiled regenerator to produce dried solvent equivalent to what is achieved today using much more costly molecular sieve technology.