Boiler Treatment Chemicals

Boiler feed water contains dissolved gasses viz., Oxygen, Carbon dioxide and hydrozen sulphide.
These gasses are removed through degasser. Oxygen in particular is removed through de-aerator.
The presence of Oxygen causes pitting corrosion.
The presence of CO2 causes grooving corrosion.
The presence of CO2 generally occur in post boiler section where it is neutralized with the help of amines.
Oxygen is removed with the addition of Hydrazine or Sulphites.
Sulphites are used in boilers having operating pressure upto 600psi. Above 600psi sulphites will decompose and loose their properties.
Above 600psi boilers hydrazine is used for removing oxygen.
Apart from removing oxygen, hydrazine forms a magnatite film over the metal surfaces in boiler system.
Also it contributes to the increase of pH.
Demerits of hydrazine are: 1. It is carcinogenic. 2. It reacts very slow.
To enhance the reaction rate it is supplemented with a catalyst.