What is the most economical method for removing dissolved gases from boiler feedwater?

Steam deaeration is the most economical method for removing dissolved gases from boiler feedwater due to its effectiveness and efficiency. This process involves passing steam through the water, which encourages the conversion of dissolved gases, such as oxygen and carbon dioxide, into a gaseous form that can be vented off. The main advantage of steam deaeration is that it not only removes these unwanted gases but also preheats the water, which reduces fuel costs during the boiler operation.

In contrast, the other options involve additional chemicals or technologies that can incur higher operational costs. For instance, while condensate polishing with ion exchange resin can help in treating feedwater, it requires initial setup and ongoing maintenance costs which might be higher compared to the one-time installation and operation of a deaerator. The addition of sodium sulfite or catalyzed hydrazine serves to scavenge oxygen in the feedwater but does not remove gases; rather, it simply addresses their presence, ultimately leading to ongoing chemical costs and potential issues related to dosage and chemical handling. Steam deaeration, meanwhile, effectively removes the gases without introducing chemicals, making it a more sustainable and cost-effective choice in the long term.