Amine Corrosion

General Information

Removal of acidic compounds (H₂S, CO₂, COS etc.) from hydrocarbon streams, both liquid and gaseous, is a critical aspect of refinery operations. The purification of hydrocarbon streams from acidic compounds is commonly achieved through the absorption-desorption process, employing various alkanolamine-based solvents.

Figure 1 illustrates a typical amine unit configuration with a simple absorber/contactor – regenerator setup. However, variations of this arrangement are also possible, depending on factors such as treatment type, the solvent used, or the type/concentration of acid compounds.

The following are four amine solvents predominantely used in sweetening units:

It’s important to mention that, in addition to standard solvents, there exists a diverse range of proprietary amine mixtures and physical solvents. These formulations are typically constructed using conventional solvents or their mixtures, incorporating proprietary additives or newly developed chemicals to achieve specific absorption/selectivity/stability properties of the final solvent. However, solvents of this specialized nature are beyond the scope of this chapter.

Each amine possesses specific properties for the selective absorption of CO₂, H₂S and other gas contaminants like COS or CS₂. In general, the overall process is based on a reversible reaction between the amine (base) and the respective acidic species, as illustrated in simplified Equation 1-4.

These and other reactions have implications for the corrosiveness of the amine solution. For example, increasing the amine concentration and CO₂ gas loading will inevitably lead to a higher concentration of HCO₃^-, which triggers the corrosion reaction, as illustrated in the example Equation 5.

Since the equilibrium of reversible reactions is dependent on temperature and concentrations of individual species (with pressure playing a negligible role in the given system), it is imperative to maintain specific process temperatures, amine concentrations, and acid gas loadings to minimize solvent corrosiveness. Table 1 provides examples of widely used solvents, along with their typical maximum loads for rich and lean streams.

Table 1 Popular solvents, typical concentration ranges, max loads and other information. ^{3 4 5 6}

To find out more information about Amine Corrosion and impact of various parameters register for free or buy a subscription.

Tools

Below are our corrosion models and integrity tools to estimate amine corrosion of carbon steel and selected CRAs.⁸

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Amine-Corrology®

Amine-Corrology® is designed to provide rapid corrosion rate estimates for carbon steel and stainless steel in amine service. It comprises a dedicated flow modelling engine, which allows you to evaluate the impact of flow parameters like Wall Shear Stress (WSS) on corrosion rates.

Note: Calculation results are currently hidden. Register for Free Trial to unlock Corrosion Rate and Service Life Results.

Integrity Risk Indicator (IRI-Corrology®: Amine)

The Challenge: Moving Beyond Linear Estimates

In amine service, traditional linear corrosion tracking may not capture the rapid transition to accelerated damage. As wall thickness decreases and degradation margins narrow, integrity concern can increase non-linearly. Small changes in amine concentration, HSAS levels, flow, or temperature can rapidly shift equipment from a stable operating window into a severe corrosion regime.

The Solution: The Integrity Risk Indicator (IRI-Corrology®: Amine)

The IRI-Corrology®: Amine provides a comparative integrity and corrosion susceptibility indicator using corrosion rate, wall thickness, remaining life, inspection, and process condition context through a margin-aware, API 581-inspired engine. This tool functions as a sensitivity analysis engine, allowing you to evaluate how variations in amine unit operating conditions - including amine type, concentration, temperature, heat stable amine salts (HSAS) levels, flow, and inspection findings - influence asset integrity.

The susceptibility score presented by the IRI model should be interpreted as an integrity and corrosion susceptibility indicator. It is not a complete API RBI risk result because consequence-of-failure, formal inspection planning, and complete RBI assessment are outside the scope of this score.

The Advantage

Access a high-speed, agile modeling engine designed to support rapid, defensible engineering decisions:

• Non-Linear Integrity Scaling: Reflects increasing integrity concern as corrosion severity, wall thickness margin, and uncertainty combine in late-life degradation states.

• Inspection Evidence Quality: Enter the Inspection Effectiveness class (A-E) to represent the quality of available inspection evidence. For amine cracking, use the applicable cracking-specific evidence basis. Inspection evidence remains distinct from monitoring credit; uncertainty-reduction actions do not add monitoring or inspection credit.

• Precision Structural Floors: Take control of your model by setting the Manual t_min structural floor to match your equipment’s justified component-specific limit.

• API 581-Inspired Risk Bands: Status and score-pill color reflect API 581-inspired integrity bands rather than the numeric score alone. If cracks are observed and remain unrepaired, the integrity and remaining life results are withheld. The User is informed about necessity of an appropriate Fitness-for-Service (FFS) assessment before the equipment is returned to service. This amine cracking option applies to carbon steel; it is not applied to stainless steel material.

Note: The Integrity Risk Indicator (IRI-Corrology®: Amine) shown below is a static preview of our Advanced engine. Upgrade to Advanced to unlock full access to IRI-Corrology®: Amine.

References

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• ^{i- Parameters like max loading and concentration will depend on several factors like presence of H2S, inhibitors etc.}
• ^{ii - Aminoethoxy ethanol known by trade names DGA® or Diglycolamine® which are registered trademarks of Huntsman Corporation.}