Sour gas is a corrosion and compliance problem before it is a sales problem: the hydrogen sulfide and carbon dioxide in a raw stream eat pipe and fail spec. Amine gas sweetening is the standard fix, and the part that decides both your operating cost and your corrosion rate is not the process, which is settled, but which amine you run. This page covers how sweetening works and how to pick and source the treating amine.
How amine sweetening works
A water solution of an alkanolamine contacts the sour gas in an absorber. The amine, a weak base, reacts with the acidic H2S and CO2 to form soluble salts, pulling them out of the gas. The rich amine then goes to a stripper where heat reverses the reaction, releasing concentrated acid gas and regenerating the lean amine, which recirculates. The chemistry is reversible by design; the amine is a reusable working fluid, and what you buy on an ongoing basis is makeup amine to replace solution losses. The basicity that drives the absorption is the same property covered on how amines act as bases.
Choosing the treating amine — the decision that sets your cost
| Amine | Type | Strength | Buy it when | Watch for |
|---|---|---|---|---|
| MEA | primary | high capacity, lowest cost, non-selective (removes CO2 + H2S) | low-pressure bulk acid-gas removal, CO2-dominant streams | most corrosive; highest regeneration energy |
| DEA | secondary | moderate capacity, less corrosive than MEA | refinery streams, moderate H2S/CO2 | lower capacity than MEA |
| MDEA | tertiary | selective for H2S over CO2, low corrosivity, low regeneration energy, runs at high concentration | selective H2S removal, energy-sensitive units; the modern default | slower on CO2 unless activated/formulated |
| DGA | primary | works at low circulation and in cold climates; removes some COS/mercaptans | remote/cold sites, low-rate units | degradation management |
The reason this is a real decision and not a default: MEA’s cheap pound is the most expensive amine to run. Its high capacity and low price are offset by corrosion and a high reboiler duty, while MDEA costs more to buy but selectively slips CO2, lowers regeneration energy, and is gentler on equipment. Formulated/activated MDEA blends let you tune CO2 pickup. Recommendation: select to your gas analysis (H2S vs CO2 ratio) and your energy budget, not to price per pound — the lifecycle cost lives in the reboiler and the corrosion coupons.
The trade-off worth stating plainly
Every treating amine trades capacity against corrosivity and energy. The small, reactive MEA molecule that grabs the most acid gas per pound is the same molecule that attacks carbon steel and demands the most stripping heat. MDEA buys selectivity and lower operating cost at a higher purchase price and slower CO2 kinetics. There is no universally best treating amine; there is the one matched to your stream and your utilities.
Sourcing treating amine — and the makeup volumes
A sweetening unit is a recurring, container-scale buy: an initial fill plus steady makeup amine against losses, ordered by the tote, drum, or bulk load. RawSource is a sourcing company — we don’t hold stock, we find and qualify treating-grade amine and source it to your specification, matched to your unit and gas analysis, with the certificate of analysis. Tell us the amine (MEA, DEA, MDEA, DGA, or a formulated MDEA), the grade, and your fill plus makeup volume, and we source it to spec. This is an oil & gas sourcing line.
Frequently asked questions
Which amine removes H2S, and which removes CO2? MEA and DEA remove both H2S and CO2 (non-selective). MDEA is selective — it preferentially removes H2S and can be tuned for CO2 with activators. The choice depends on your gas’s H2S-to-CO2 ratio and your treated-gas spec.
Why choose MDEA over MEA if MEA is cheaper? MEA costs less per pound but is the most corrosive and the most energy-intensive to regenerate. MDEA’s higher purchase price is often offset by lower corrosion, lower reboiler duty, and H2S selectivity — so the cheaper amine can be the more expensive unit to run.
How much amine does a unit consume? A unit holds a working charge and consumes makeup amine to replace losses (vaporization, entrainment, degradation). It is a recurring bulk purchase; size the makeup order to your observed loss rate.
Where an amine unit calls for a silicone-based antifoam to manage foam in the contactor or regenerator, RawSource supplies Silicone Antifoam Emulsion in bulk for makeup dosing trials.
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