Dehydration and hydrate-control glycols — TEG, MEG, and DEG — plus methanol as a thermodynamic hydrate inhibitor for natural gas and pipeline service.
Dehydration glycols are hygroscopic diols that remove water vapor from natural gas so it meets a pipeline water-content limit, typically around 7 lb of water per MMscf. Triethylene glycol is the standard contactor solvent for this duty. A second, related job is hydrate control: monoethylene glycol injected into wet gas lines depresses the temperature at which gas hydrates form. Match the glycol to the job — TEG for dehydration towers, MEG for hydrate inhibition.
TEG dominates gas dehydration because it regenerates cleanly at the reboiler temperatures a glycol unit can reach. Diethylene glycol is the older, lower-boiling option and still appears where regeneration temperature is limited, though it carries more vaporization loss. Both run as the working fluid of a closed contactor-and-regenerator loop, so makeup volumes are modest once a unit is charged. Specify TEG for new dehydration service and reserve DEG for existing low-temperature units.
For hydrate inhibition the real choice is MEG versus methanol. MEG can be recovered and recycled through a reclamation unit, which favors continuous, high-volume injection on subsea tiebacks and long flowlines. Methanol is cheaper per gallon and effective for startup or intermittent duty, but it is usually lost to the hydrocarbon and water phases and can create downstream specification problems. Choose MEG when injection is continuous and recovery pays back; choose methanol for short, low-volume duty.
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