Oxygen Scavenger

Definition

A chemical added to feedwater that reacts with the residual dissolved oxygen that mechanical deaeration leaves behind. It is insurance, not a substitute for deaeration.

For low-pressure boilers below roughly 900 psi the most common scavenger is sodium sulfite, which reacts with oxygen to form sodium sulfate. For high-pressure boilers above 900 psi sulfite thermally decomposes into corrosive sulfur dioxide and hydrogen sulfide, so the industry uses carbohydrazide, DEHA, erythorbate, and formerly hydrazine. When the mechanical side fails, no amount of scavenger can compensate.

Related concepts

Deaeration · Sodium Sulfite · Dissolved Oxygen

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Part of The Blueprint of Water · 🧪 chemistry