Oxygen Scavenger is a catalysed liquid solution of Hydrazine and diethylhydroxylamine (DEHA). Its volatile properties ensure distribution throughout the boiler and condensate system, and hence protects against oxygen corrosion in all parts of the system. The product also provides the required conditions for the establishment of a passivating layer of magnetite on all inner surfaces. It is a low toxicity product, suitable for high, medium and low pressure boiler systems.
Residual dissolved oxygen in the boiler promotes pitting-type corrosion that is an insidious, highly localized form of attack. If left unchecked, the propagation of the pit ultimately leads to tube failure. Boiler makeup can contain up to 10 ppm dissolved oxygen depending on the temperature. The remaining oxygen is removed by chemical scavengers fed to the feedwater storage section of the deaerator.
Sodium sulfite Na2SO3 is the most commonly used and fastest acting oxygen scavenger. Available as a 90% active powder or less-concentrated liquid, sodium sulfite reacts rapidly with residual dissolved oxygen to form harmless sodium sulfate. Although very effective as an oxygen scavenger, sulfite does not readily react with boiler metal to promote the formation of a protective black iron magnetite surface. Black iron magnetite is a more passive (corrosion resistant) form of iron as compared to red iron hematite.
Hydrazine is often used as an oxygen scavenger in higher pressure boilers since it does not add dissolved solids to the boiler water. It also has the advantage of converting red iron oxide (hematite) into black iron oxide (magnetite).
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