1. GSU – Gas Sweetening Unit
Purpose: Removes acidic impurities (H₂S and CO₂) from natural gas.
Specification:
-
H₂S ≤ 4 ppmV (parts per million by volume)
-
CO₂ ≤ 4 vol% (volume percent)
Explanation:
Natural gas from wells often contains hydrogen sulfide (H₂S) and carbon dioxide (CO₂).
The GSU uses amine-based absorption (commonly MEA, DEA, or MDEA) to remove these gases.
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H₂S is highly toxic and corrosive. Reducing it to 4 ppmV ensures safety and meets pipeline/sales gas standards.
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CO₂ reduces heating value and can form carbonic acid with water, so it’s limited to 4 vol%.
End result: The gas leaving GSU is “sweet gas”, safe for downstream processing and sale.
2. GDU – Gas Dehydration Unit
Purpose: Removes moisture (H₂O) from the gas.
Specification:
- Moisture content ≤ 112 kg/MMSCM (kilograms per million standard cubic meters of gas)
Explanation:
Moisture in natural gas can form hydrates and cause pipeline blockages under high pressure.
The GDU usually uses triethylene glycol (TEG) dehydration to absorb water vapor.
Reducing water content to this level ensures gas is dry enough for transportation and storage without freezing or corrosion issues.
3. DPDU – Dew Point Depression Unit
Purpose: Removes heavier hydrocarbons (C₅⁺) to control the gas dew point.
Specification:
- Dew Point: -3°C at 100 bar
Explanation:
At high pressure, heavier components (like pentanes, hexanes) condense into liquids, which can damage pipelines and compressors.
The DPDU cools the gas and separates these condensables to achieve a dew point of -3°C at 100 bar — meaning the gas won’t form liquids under normal pipeline conditions.
Summary
| Unit | Full Form | Function | Key Specification | Purpose |
|---|---|---|---|---|
| GSU | Gas Sweetening Unit | Removes H₂S & CO₂ | 4 ppmV H₂S, 4 vol% CO₂ | To meet safety & pipeline specs |
| GDU | Gas Dehydration Unit | Removes moisture | 112 kg/MMSCM | Prevent hydrate formation |
| DPDU | Dew Point Depression Unit | Removes heavy hydrocarbons | -3°C at 100 bar | Prevent condensation in pipelines |
