Steam generation systems in industrial and utility settings are highly sensitive, depending on various machines to maintain proper function. Among these devices is the deaerator. Though dissolved gases in feedwater are not often the first to come to mind for boiler safety concerns, a boiler’s efficiency and integrity can be compromised over time by aerated feedwater. Thus, the boost to equipment lifespan and function that deaerators provide is well worth understanding.
Why Deaeration Is Vital
Dissolved oxygen and carbon dioxide can cause severe damage to steel, iron and copper pipes, as well as any other equipment aerated water runs through or remains in contact with. Oxygen is well-known for causing iron and steel alloys to rust if not properly treated, but water containing dissolved oxygen amplifies the risk because the oxygen can more readily bind to the metal. Additionally, carbon dioxide dissolved in water forms carbonic acid that also can corrode metals.
How Deaerators Work
Deaerators are designed to reduce the concentration of dissolved oxygen and carbon dioxide in water to safe levels. The deaerator uses a flow of steam to ‘scrub’ feedwater, heating and agitating it to reduce gas solubility and carrying away the released gases. These gases, and a portion of the steam, are vented out of the system, and the treated water flows into a storage tank. In order to maximize the scrubbing effect of the steam, undeaerated water is either input as a fine spray of droplets or allowed to cascade down multiple trays while steam flows upward, depending on the models that the deaerator supplier offers. Many designs pass feedwater through two or more stages of deaeration, ultimately removing all carbon dioxide and reducing the oxygen content to below 10 parts per billion (ppb).
Effective deaerator operation, optionally combined with chemical ‘oxygen scavengers’, can significantly extend the life of boilers and other equipment, reduce operation costs and improve quality of steam output.