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Process Gas Dehyration

Glycol dehydration is commonly used to remove water from natural gas and natural gas liquids through physical absorption. Glycol, such as triethylene glycol, absorbs water from the gas stream in an absorber column. The water-laden glycol is then heated and dried in a stripper column to regenerate the lean glycol for reuse. This process lowers the hydrate formation point of the gas to prevent freezing or plugging in downstream pipelines and equipment.

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79 views2 pages

Process Gas Dehyration

Glycol dehydration is commonly used to remove water from natural gas and natural gas liquids through physical absorption. Glycol, such as triethylene glycol, absorbs water from the gas stream in an absorber column. The water-laden glycol is then heated and dried in a stripper column to regenerate the lean glycol for reuse. This process lowers the hydrate formation point of the gas to prevent freezing or plugging in downstream pipelines and equipment.

Uploaded by

Satish Shinde
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Glycol dehydration

1) Glycol dehydration is a liquid desiccant system for the removal of water from natural
gas and natural gas liquids (NGL). It is the most common and economical means of
water removal from these streams.
2) Glycols typically seen in industry include triethylene glycol (TEG), diethylene
glycol (DEG), ethylene glycol (MEG), and tetraethylene glycol (TREG).

3) Gas produced from a reservoir, natural gas usually contains a large amount of water
and is typically completely saturated or at the water dew point. This water can cause
several problems for downstream processes and equipment.
a. At low temperatures the water can either freeze in piping.
b. More commonly the case, form hydrates with CO2 and hydrocarbons (mainly
methane hydrates). Depending on composition, these hydrates can form at
relatively high temperatures plugging equipment and piping.
c. Glycol dehydration units depress the hydrate formation point of the gas
through water removal.
4) This free water phase will often contain some portions of acid gas (such as H2S and
CO2) and can cause corrosion.

Process Description:
1) Lean, water-free glycol (purity >99%) is fed to the top of an absorber (also known as
a "glycol contactor") where it is contacted with the wet natural gas stream. The glycol
removes water from the natural gas by physical absorption and is carried out the
bottom of the column.
2) Upon exiting the absorber the glycol stream is often referred to as "rich glycol". The
dry natural gas leaves the top of the absorption column and is fed either to a pipeline
system or to a gas plant. Glycol absorbers can be either tray columns or packed
columns.
3) After leaving the absorber, the rich glycol is fed to a flash vessel where hydrocarbon
vapors are removed and any liquid hydrocarbons are skimmed from the glycol. This
step is necessary as the absorber is typically operated at high pressure and the pressure
must be reduced before the regeneration step. Due to the composition of the rich
glycol, a vapor phase having a high hydrocarbon content will form when the pressure
is lowered.
4) After leaving the flash vessel, the rich glycol is heated in a cross-exchanger and fed to
the stripper (also known as a regenerator). The glycol stripper consists of a column, an
overhead condenser, and a reboiler. The glycol is thermally regenerated to remove
excess water and regain the high glycol purity.
5) The hot, lean glycol is cooled by cross-exchange with rich glycol entering the
stripper. It is then fed to a lean pump where its pressure is elevated to that of the
glycol absorber. The lean solvent is cooled again with a trim cooler before being fed
back into the absorber. This trim cooler can either be a cross-exchanger with the dry
gas leaving the absorber or an air-cooled exchanger.
6)

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