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NGE Lectures 21

This document provides an overview of natural gas dehydration using triethylene glycol (TEG). It describes the TEG process which involves removing water from natural gas in an absorber column using TEG, then regenerating the glycol in a stripping column/reboiler to remove water and produce dry natural gas. Key steps include contacting the gas and glycol counter-currently in the absorber, heating the water-laden glycol in the stripper's reboiler, and recycling the regenerated lean TEG.

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23 views8 pages

NGE Lectures 21

This document provides an overview of natural gas dehydration using triethylene glycol (TEG). It describes the TEG process which involves removing water from natural gas in an absorber column using TEG, then regenerating the glycol in a stripping column/reboiler to remove water and produce dry natural gas. Key steps include contacting the gas and glycol counter-currently in the absorber, heating the water-laden glycol in the stripper's reboiler, and recycling the regenerated lean TEG.

Uploaded by

Zain Gillani
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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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Natural Gas Engineering

(CHE-484)
Lecture 21:

Dehydration

1
Dehydration by Absorption
• Water vapor is removed from the gas by intimate
contact with a hygroscopic liquid desiccant
• The contact is usually achieved in packed or trayed
towers
• Liquid desiccants: Glycols (ethylene glycol,
diethylene glycol, triethylene glycol)
• Single type of pure glycol or blend
• TEG: most cost effective
• Glycol derivative has a chemical affinity for water
and removes water from the gas stream.
Dehydration by Absorption (Cont’d)
• Most desirable properties of the liquid desiccant to
use for commercial dehydration purposes
1. High absorption efficiency
2. Relatively easy and economic regeneration
3. No interaction with the hydrocarbon portion of
the gas, and no contamination by acid gases
4. Noncorrosive and nontoxic
5. No operational problems when used in high
concentrations
Triethylene glycol process
• Wet natural gas enters an inlet separator
‒ to remove all liquid hydrocarbon derivatives from
the gas stream

• Gas flows to an absorber


‒ Dry glycol is injected onto the top tray
‒ Glycol flows across each tray and down through a
downcomer pipe onto the next tray
‒ Wet gas is introduced to the bottom of the
contactor
‒ Wet natural gas is contacted countercurrently
and dried by the lean triethylene glycol
Triethylene glycol process
• Dry natural gas exiting the absorber passes through
a gas/glycol heat exchanger
‒ Outlet dry gas cools the hot regenerated glycol
‒ Dry natural gas leaves the unit
• Wet or rich triethylene glycol exiting the absorber
‒ flows through a coil in the accumulator where it
is preheated by hot lean glycol
Triethylene glycol process
• Stripping Column/Reboiler:
‒ Rich glycol enters the stripping column and flows
down the packed bed section into the reboiler
‒ Glycol is heated to 350 - 400 °F to remove
enough water vapor to reconcentrate it to 99.5%
or higher
‒ Steam generated in the reboiler strips absorbed
water and VOCs out of the glycol as it rises up the
packed bed
‒ Water vapor and desorbed natural gas are vented
from the top of the stripper
Triethylene glycol process
• The hot regenerated lean triethylene glycol flows
out of the reboiler into the accumulator
‒ Cooled via cross exchange with returning rich
glycol
‒ Lean triethylene glycol is pumped to a glycol/gas
heat exchanger and back to the top of the
absorber
• Wet gas is dehydrated in the absorber
• The stripping column regenerates the water-free
triethylene glycol

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