Neutralizing Amine

Neutralizing amine is a chemical used in water treatment systems, especially in steam and condensate systems (boiler feedwater systems), to control corrosion due to acidity produced by dissolved gases such as carbon dioxide (CO₂).

Main Functions

The main purpose of using neutralizing amine is to increase the pH of condensate water by neutralizing carbonic acid (H₂CO₃) formed from the dissolution of CO₂ in water:

CO2+H2O→H2CO3→H++HCO3-CO₂+H₂O\rightarrow H₂CO₃\rightarrowH⁺+HCO₃-CO2+H2O→H2CO3→H++HCO3-.

Amines react with H⁺ ions (acid) to neutralize the pH:

RNH2+H+→RNH3+RNH₂+H⁺\rightarrowRNH₃⁺RNH2+H+→RNH3+

Thus, amines help prevent corrosion of pipes, pumps, and metal equipment in steam systems.

Types of Neutralizing Amine

1. Morpholine

   • Medium volatility

   • Suitable for medium-scale steam systems

   • Provides protection up to the condensate system end

2. Cyclohexylamine

   • High volatility

   • Suitable for long systems (long vapor distribution distances)

3. Diethylaminoethanol (DEAE)

   • Medium volatility, often used with other amines

4. Blended Amines

   • Combination of several types of amines to customize system characteristics.

   • Example: morpholine + cyclohexylamine blend

Applications in Boiler Systems

Neutralizing amines are usually introduced to the feedwater system or directly to the steam header. Dosage depends on:

• target pH (typically 8.3-9.2 for condensate),

• system pressure,

• length of the steam distribution system,

• CO₂ content resulting from alkalinity decomposition.

Main objective: keep the pH of the condensate from being too acidic, thus avoiding pitting corrosion and thinning of the pipeline.

Things to Watch Out For

• Excessive dosing can cause the pH to be too high, which can lead to alkaline attack on copper metals.

• Should be adjusted according to metal type, system length, and operating conditions.

• Combination with film-forming amines can further enhance protection against corrosion.

Conclusion

Neutralizing amine is an important volatile pH control agent for corrosion prevention in steam systems. Proper selection of amine type and dosage is key to the success of an effective and safe boiler water treatment program.