Triethylene Glycol (TEG) Gas Dehydration Calculator
GPSA / Bukacek engineering modeling for natural gas contactor towers and reboiler regeneration systems.
1. Natural Gas Feed Conditions
2. Moisture & Target Dew Point
3. Glycol Circulation & Hydraulics
Engineering Output & Regeneration Profile
Inlet & Outlet Stream Details
Closed-Loop TEG Dehydration & Regeneration P&ID Visualizer
Interactive schematic of high-pressure absorption contactor, rich glycol flash separator, plate heat exchanger, and 204 deg C reboiler still column.
5 Fatal Traps & Industrial Engineering Pitfalls
1. Heavy Hydrocarbon & BTEX Foaming in Contactor
When feed natural gas drops below its hydrocarbon dew point prior to entering the contactor, liquid condensates (C6+ and aromatic BTEX compounds) enter the glycol stream. Hydrocarbons dissolve into triethylene glycol and drastically reduce surface tension, causing violent foaming in the contactor. Gas velocities fluidize the foam, carrying hundreds of gallons of glycol out the top into the dry gas line within minutes, causing sudden pressure spikes and emergency pipeline shutdown.
2. Thermal Overheating & Glycol Pyrolysis at >206 deg C
Triethylene glycol decomposes rapidly above 206.7 deg C (404 deg F). If the reboiler burner tube experiences local hot spots or if scale/salt deposits insulate the firetube, localized film temperatures exceed 230 deg C. Thermal pyrolysis produces corrosive organic acids (formic and acetic acid) and heavy polymeric tar. The system pH plummets from 8.0 to below 5.0, resulting in rapid acid pitting of carbon steel vessels and clogging of heat exchanger plates.
3. Feed Gas Ingress Temperature Below Glycol Temperature
Lean glycol must enter the top of the contactor 3 to 6 deg C (5 to 10 deg F) warmer than the overhead exit gas. If lean glycol enters colder than the gas, heavy hydrocarbons in the gas will condense directly into the top liquid distributor trays, causing instant foaming and ruining the water absorption mass transfer. Conversely, if glycol is more than 15 deg C hotter than the gas, excessive glycol vaporizes into the treated gas, escalating chemical consumption costs.
4. Stripping Gas Condensation in Still Column Vent
When stripping gas is introduced into the regenerator to achieve >99.5% purity, the water vapor and hydrocarbon off-gas must vent freely at atmospheric pressure. If the still column overhead temperature drops below 100 deg C due to excessive reflux cooling or ambient winter winds, water condenses in the still packing and runs back into the reboiler. The reboiler becomes water-logged, causing thermal surging, steam explosions, and failure to regenerate the glycol.
5. Inadequate Flash Tank Residence Time for Liquid Skimming
Rich glycol leaving the high-pressure contactor (50 to 90 barg) carries dissolved methane and entrained condensate. The rich glycol flash separator (operating at 3 to 5 barg) must provide at least 15 to 20 minutes of liquid retention time to allow liquid hydrocarbon condensate to gravity-separate and float on top of the heavier glycol (specific gravity 1.12). If the flash tank is undersized, liquid hydrocarbon carries directly into the reboiler firetube, creating explosive vapor surges in the atmospheric still.
Gas Dehydration Thermodynamic Equations & Hydraulic Sizing
The saturated water content $W_{in}$ of sweet natural gas is calculated via the Bukacek empirical relation:
Where $P_{H2O}^0$ is water vapor pressure in psia and $P$ is absolute operating pressure in psia.
The required lean glycol circulation rate $L_{TEG}$ in gallons per minute (GPM) is:
Where $R_{circ}$ is the circulation ratio (typically $2.5 - 4.0 ext{ gal TEG / lb H}_2 ext{O}$).
Contactor internal diameter $D_c$ is determined by the Souders-Brown flooding correlation:
The total reboiler heat duty $Q_{reb}$ accounts for sensible heating of glycol, heat of vaporization of water ($2260 ext{ kJ/kg}$), and still reflux cooling: