Amine Treating System - Working Principle

An amine treating system, or gas sweetening unit, removes H₂S and CO₂ from sour gas by circulating an aqueous amine solution in a continuous absorption-regeneration loop. The process absorbs acid gases into the solvent (lean-to-rich) in a contactor, followed by thermal regeneration (rich-to-lean) to release the impurities and reuse the amine, effectively creating a closed-loop system.

This video provides an overview of how an amine scrubbing system works:

Core Working Principles

The system operates through two primary steps:

• Absorption (Contactor/Absorber): Sour gas enters the bottom of a contactor column, while "lean" (clean) amine solution is fed into the top. As the gas rises, it flows upward through trays or packing, making intimate contact with the downward-flowing amine. The amine chemically absorbs the H2S and CO2 and "sweet" (treated) gas exits the top.
• Regeneration (Stripper/Regenerator): The "rich" amine (containing the absorbed acid gases) is sent to a regenerator column. It is heated (typically to 225°F or 105 - 125°C) in a reboiler, breaking the chemical bonds and releasing the H₂S and CO₂ as top gas, which are then sent to a sulfur recovery unit or flare. The regenerated "lean" amine is cooled and pumped back to the absorber.

Key Components of an Amine System

• Inlet Separator: Removes solids and liquids (hydrocarbons/water) from the sour gas to prevent foaming.
• Absorber (Contactor): A trayed or packed tower where the absorption process occurs.
• Regenerator (Stripper): A tower where heat reverses the absorption process.
• Reboiler: Provides the heat to strip acid gases from the rich amine.
• Heat Exchangers & Pump: Cools the lean amine and pumps it back into the absorber.

Common Amines Used

• MEA (Monoethanolamine): High reactivity, often used for total acid gas removal.
• DEA (Diethanolamine): Often used in gas plants.
• MDEA (Methyldiethanolamine): High selectivity for H₂S over CO₂

Why It Is Used

• Safety: H₂S is highly toxic and lethal even at low concentrations.
• Corrosion Prevention: Acid gases in the presence of water form acids that can corrode pipelines and equipment.
• Efficiency: The closed-loop design minimizes chemical waste and operational costs.

The Process Cycle

The system is a closed-loop process consisting of two primary stages:

• 1. Absorber (Contactor) Stage

• Inlet: Sour gas enters at the bottom, and "Lean Amine" (clean solvent) is sprayed from the top.
• Contact: As they pass each other over trays or packing, the amine absorbs the and H₂S  and CO₂
• Outlet: Purified "Sweet Gas" exits the top, while "Rich Amine" (loaded with acid gas) collects at the bottom.

• 2. Stripping (Regenerator) Stage

• Pre-heating: The rich amine passes through a heat exchanger to gain heat from the hot lean amine returning from the regenerator.
• Stripping: In the regenerator column, a reboiler heats the solution, creating steam that "strips" the acid gases out of the amine.
• Cooling: The now-lean amine is cooled and pumped back to the absorber to start the cycle again.