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Wednesday, 14 March 2018

Oxygen Scavenger Chemicals for Boiler Feed Water

Oxygen Scavengers

Ø  Oxygen scavengers are mainly used for food and pharmaceutical applications, but can also be used for any product that needs a low oxygen storage atmosphere.
Ø  Essentially, oxygen scavengers are so named because they preferentially absorb oxygen within the environment, thus, preventing the oxygen from reacting with the product.
Ø  Many other terms have been used to describe oxygen scavengers, which include the following: antioxidants, interceptors, controllers, and absorbers.
Ø  Oxygen scavengers or oxygen absorbers are added to enclosed packaging to help remove or decrease the level of oxygen in the package. They are used to help maintain product safety and extend shelf life.

Boiler Oxygen Scavenger

  • Ø  Boiler Oxygen Scavenger is a catalyzed oxygen scavenger in a liquid form based on catalyzed sodium bisulfite. It helps to instantly remove oxygen from the boiler feed water by converting itself to sodium bisulfate and also reduces alkalinity.

Ø  Boiler water treatment is considered as a part of industrial water treatment that specially focuses on the removal or chemical modification of substances potentially posing as a damaging threat to the boiler. 

Key Feature and Benefits of Oxygen Scavenger

Ø  Catalyzed Oxygen Scavenger for instant oxygen removal
Ø  Minimizer or eliminates oxidation corrosion (corrosion due to the presence of oxygen)
Ø  Concentrated powder product
Ø  Buffers pH
Ø  Imparts power saving
Ø  Corrosion is a major problem in steam systems with high consumption of make-up water. Freshwater contains dissolved oxygen. Oxygen together with high temperature is highly corrosive for the carbon steel piping used in steam systems.
Ø  To avoid corrosion the oxygen in the make-up water for saturated steam production should be removed by using some kind of oxygen absorbers scavenger chemicals and/or deaeration towers.

Scavenger Chemicals
Some commonly used scavenger chemicals are:
Ø  Sodium Sulfite - common in low and medium pressure systems
Ø  Hydrazine - common in high-pressure systems
Ø  Sodium erythorbate

Sodium Sulfite
Ø  Sodium Sulfite is a white crystalline or powder soluble in water. Sodium Sulfite decomposes on heating and is prepared from sulfur dioxide and sodium carbonate or caustic soda.
Ø  Sodium Sulfite is an effective oxygen scavenger for use in systems operating below 1000 psi. For pressures above 1000 psi breakdowns may form corrosive Hydrogen Sulfide and/or Sulfur Dioxide.
Ø  Sodium Sulfite may also increase the number of dissolved solids and the conductivity of the boiler water. 

Ø  Hydrazine efficiently eliminates the residual oxygen by reacting with the oxygen forming water and gaseous nitrogen.
Ø  Since hydrazine is a toxic chemical it must not be used in steam plants supporting food processing systems.

Sodium Erythorbate
Ø  Erythorbic acid and its sodium salt can replace Sodium sulfite and Hydrazine as oxygen scavengers.
Ø  Sodium Erythorbate is a nontoxic oxygen scavenger that can also be used in food processing systems.

Adding Scavenger Chemicals
Ø  For best performance the chemical should be added to the storage tank before the feed tank.
Ø  The efficiency of a scavenger is increased with longer reaction time. Adding directly to the make-up water feed line is not recommended due to short reaction time.