Boiler Alkalinity Breakdown

Definition

The heat- and pressure-driven breakdown of feedwater alkalinity inside a boiler, where bicarbonate forms carbonate, water, and CO2, and carbonate can further hydrolyze to hydroxide and more CO2.

Boilers are closed systems where carbonate enters with makeup water as bicarbonate alkalinity, and heat takes over as the lever. Thermal decomposition follows 2HCO3- to CO3 2- plus H2O plus CO2, and at high pressure carbonate hydrolyzes by CO3 2- plus H2O to 2OH- plus CO2. The released CO2 cannot stay dissolved under boiler conditions and volatilizes with steam, while the resulting carbonate causes any calcium present to precipitate on heat-transfer surfaces.

Related concepts

CO2 Generation Rule of Thumb · Inverse Solubility of Calcium Carbonate · Boiler Makeup Softening

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Part of The Blueprint of Water · 🧪 chemistry