Natural Gas Condensers for Vapor and Hydrocarbon Recovery

Hydrocarbon and Water Dew Point

Pipeline tariffs commonly set a hydrocarbon dew point and a water content limit, often around 7 lb per MMscf. Meeting the hydrocarbon dew point means cooling well below ambient with mechanical refrigeration or a Joule-Thomson valve, and a gas-to-gas exchanger recovers cold from the outlet gas to cut the refrigeration load. Ethylene glycol injected ahead of the cold section keeps hydrates out.

Send the inlet gas analysis through C7-plus so the condensing curve can be calculated instead of estimated.

Glycol Still Column Overhead

A TEG dehydration unit drives absorbed water out of glycol in a reboiler, and the still column overhead releases water vapor along with BTEX and other aromatics stripped from the gas. Condensing that overhead captures BTEX for disposal or recovery and keeps it out of the air. The vapor is near atmospheric and carries noncondensables, so venting and pressure drop matter more than surface area.

Still column overhead flow is small, but it swings with glycol circulation rate and reboiler temperature. A condenser sized on average flow can let BTEX escape during a high-circulation upset, which is exactly when an emissions permit is most likely to be tested.

Fin Fan or Shell and Tube

A Horizontal Fin Fan is the default on remote sites: no water treatment, no tower, power only for the fans. It is limited by summer ambient, and dew point drifts up on hot afternoons unless the cooler has margin. A Fixed Tubesheet shell and tube condenser gives a closer approach where water or refrigerant is available and handles high-pressure, sour, wet gas in a compact all-welded package.

Sour Service Materials

Gas containing H2S calls for materials that meet NACE MR0175 / ISO 15156 hardness limits, qualified welding and often a corrosion allowance on carbon steel. Wet CO2 adds its own attack.

Where free water condenses alongside H2S and CO2, stainless tubes or a clad tubesheet can outlast carbon steel by years; the call depends on partial pressures, which belong in the inquiry.

Separating NGL, Water and Glycol

The condenser is only as good as the separator after it. Natural gas liquids, water and glycol leave the gas in a three-phase separator, and liquid that stays as mist defeats the dew point. Keep condenser outlet velocity low, and say wether the liquids are sold, stabilized or tanked, since that decides how cold the outlet should run.

Winter Hydrates, Summer Dew Point

Gas volume, composition and ambient temperature all change through the year. An air cooler sized for a design day can overcool in winter and risk hydrates at the outlet. Louvers, variable-speed fans and an outlet temperature controller keep the gas above its hydrate point in cold weather and on its dew point target in hot weather.

Field compressor stations add one more consideration: an air cooler that also serves the compressor jacket water and lube oil shares fans and plot space with the gas sections. Give us all the services on the bay, since a combined unit is sized as one package and every section affects the others.