Dehydration is the process of removing water vapor from the gas stream. It can be accomplished by several methods, but the process we are using is called glycol absorption. In this process, a hygroscopic liquid (glycol) is used to remove the water vapor from the gas in the tower.
Diethylene (DEG) and Triethylene (TEG) glycols are the two liquids normally used for gas dehydration. TEG is a liquid desiccant, a solvent that attracts and retains water at low temperatures but releases the water at high temperatures in the regen reboiler. Using TEG has following advantages:
TEG is more easily regenerated to a 98-99.5% solution in an atmospheric stripper because of its high boiling point and other physical properties. This permits high dew point depressions in the range of 80-140F.
Solid Desiccant Dehydration
Solid-desiccant dehydration is the primary form of dehydrating natural gas using adsorption and usually consists of two or more adsorption towers, which are filled with a solid desiccant. Typical desiccants include activated alumina, silica gel, and molecular sieve.