Why is condensate deaeration important? How is it done in ship steam plant?
Dissolved air is dangerous for a steam system because of following reasons:
- Air contains both carbon dioxide and oxygen along with nitrogen and other gases. Carbon dioxide will lower the pH of the water. The CO2 combines with H2O (water) to form H2CO3 (Carbonic acid) that will lower the pH and contribute to corrosion problems in the steam system.
- Hot water is a good solvent. The oxygen in the condensate that makes condensate a strong oxidizing agent that can attack metals.
- Carbon seal faces can be attacked by high oxygen levels in the condensate.
- The more gases entrained in the condensate, the more likely the feed pump will experience cavitation problems.
- The condensate temperature determines the amount of dissolved oxygen.
- The average level detected in condensate receivers is 3 ppm. This is amount is enough to induce pitting corrosion.
De-aerate the condensate by:
- heating the condensate with steam in a deaerating tank/ hot well.
- adding oxygen scavenging chemical to a hot well as part of the water treatment program
