Boiler Water Treatment
Oxygen scavengers are chemical additives fed to the boiler feed water or condensate return to remove residual dissolved oxygen. Corrosion and its deleterious effects cause numerous difficulties with materials being exposed to adverse effects. Hydrazine is generally used as an oxygen scavenger for corrosion control in thermal power plants. Although hydrazine is very effective in this application, it is genotoxic and carcinogen in nature.
Hydrazine Hydrate is a colorless liquid which boils at 113°C and is highly soluble in water. It is not a naturally occurring substance and is a powerful reducing agent, reducing itself to form nitrogen and water. Hydrazine also reacts with soft haematite layers on the boiler tubes and forms a hard magnetite layer, which subsequently protects the boiler tubes from further corrosion, forming an important component in boiler water treatment.
Hydrazine has been used in high purity and high pressure systems (greater than 900 psig), where sulphite compounds in the steam could otherwise foul a catalyst, or where feed water is used for steam attemperation. Hydrazine reacts with dissolved oxygen, and after analyzing the content of dissolved oxygen, it can be added directly in the aerator of the boiler systems. The reaction is slow at ambient temperatures but increases with temperature and pH. Significant amount of ammonia is formed when hydrazine decomposes and this ammonia can attack copper and Cu-alloys in the condensate and feed-water system.
Key Features and Benefits:
Removes dissolved oxygen
Prevents oxidative corrosion
Causes mild steel passivation
Does not add to the TDS of boiler water
Completely volatile in nature, hence non-residual