Acid Gas Amine Sweetening Contactor & Reboiler Calculator
Design natural gas and refinery amine treating units (MEA, DEA, MDEA, DGA). Calculate solvent circulation rates, acid gas loading (mol/mol), contactor column diameter via Souders-Brown flooding, stripper reboiler duty, and pump power.
1. Sour Gas Feed Conditions
2. Amine Solvent & Design Loading
Treating Sizing & Equipment Specs
Acid Gas Mole Balance & Loading
Reboiler Energy Breakdown (kW)
-- kW
-- kW
-- kW
Interactive Amine Treating Unit (ATU) Process Flow Diagram
Complete animated schematic showing high-pressure Contactor, Flash Tank, Lean/Rich Exchanger, Stripper Regenerator, Reboiler, Reflux Drum, and High-Pressure Charge Pump.
In-Depth Process Chemistry: Amine Gas Treating Principles
Alkanolamines remove acid gases ($H_2S$ and $CO_2$) via reversible exothermic chemical reactions. The choice of amine class dictates kinetics, loading limits, and regenerator energy consumption:
Fast reaction kinetics forming stable carbamates: $2 RNH_2 + CO_2 \rightleftharpoons RNHCOO^- + RNH_3^+$. Stoichiometrically limited to $0.5 \text{ mol } CO_2 / \text{mol amine}$. High heat of reaction ($\sim 1,900 \text{ kJ/kg } CO_2$) requires immense reboiler steam.
Moderate kinetics, carbamate formation with lower stability. Can reach loadings of 0.35 to 0.42 mol/mol without excessive corrosion. Standard for refinery sour gas.
Cannot form carbamates. Reacts with $CO_2$ via base-catalyzed hydration: $R_3N + CO_2 + H_2O \rightleftharpoons R_3NH^+ + HCO_3^-$. Theoretical loading reaches $1.0 \text{ mol/mol}$. Lower heat of reaction ($\sim 1,150 \text{ kJ/kg}$) saves up to 40% in reboiler energy.
Solvent Circulation Rate Derivation
The required molar flow rate of pure amine is governed by the total acid gas absorption demand divided by net operating loading differential ($\Delta \alpha = \alpha_{rich} - \alpha_{lean}$):
$$L_{solution} = \frac{\dot{m}_{amine}}{\text{wt}\% \times \rho_{solution}}$$
Souders-Brown Contactor Column Diameter
The absorber column diameter is sized to prevent vapor flooding, entrainment, and liquid carryover. The maximum allowable gas superficial velocity ($v_{max}$) is computed using the classic Souders-Brown equation:
$$D_{col} = \sqrt{\frac{4 \, Q_{gas,actual}}{\pi \, v_{design}}}$$
5 Fatal Engineering Pitfalls in Amine Gas Sweetening Plants
Carbon steel in contact with hot rich amine ($> 70^\circ\text{C}$) is intensely susceptible to alkaline stress corrosion cracking along welded seams. To prevent catastrophic vessel rupture, all piping and vessels handling rich amine above 65°C must undergo full Post-Weld Heat Treatment (PWHT) per NACE SP0296, with maximum rich loading strictly limited to 0.40–0.45 mol/mol.
If entering lean amine temperature drops below the feed sour gas dew point ($T_{amine} < T_{gas} + 3^\circ\text{C}$), heavy hydrocarbons ($C_5+$) condense directly into the amine liquid. Liquid hydrocarbons drastically lower surface tension, causing violent column foaming, massive liquid carryover into downstream pipelines, and immediate contactor differential pressure collapse.
Oxygen ingress or trace organosulfur contaminants form non-regenerable Heat Stable Salts (formates, acetates, thiosulfates). When HSS exceeds 2.0 wt% of total amine, active solvent capacity plummets, corrosion rates increase tenfold, and reboiler heat duty escalates. An online slipstream ion exchange or vacuum reclaim unit is mandatory once HSS surpasses 1.5 wt%.
Steam supplied to the regenerator reboiler must not exceed 150°C (typical heating steam pressure limited to 3.5–4.5 bar g). Exceeding a 125°C bulk amine reboiler temperature or exposing tubes to high steam skin temperatures triggers irreversible thermal degradation of alkanolamines into corrosive oxazolidones, producing corrosive off-gases and destroying millions of dollars of solvent.
In the overhead stripper condenser, concentrated wet $H_2S$ and $CO_2$ vapors condense alongside traces of stripped ammonia and cyanides. This creates an extremely corrosive acidic condensate environment. Carbon steel condenser tubes fail within months; 316L stainless steel, titanium, or duplex alloy tubes are essential, paired with continuous water wash injection to prevent salt deposition.