What You Need to Know About Deaerators

Steam boilers do exactly as their name implies, they produce steam; however, many factors must be considered and managed to do this, including corrosion, scale, water minimization, fuel efficiency, safety, and Total Cost of Operation. Boiler feedwater often contains dissolved gases, such as oxygen, carbon dioxide, and ammonia. These dissolved gases are problematic for the boiler system because they may cause corrosion, leading to equipment failures (e.g., carbon dioxide can form carbonic acid in boiler condensate, lowering the pH, and corroding the condensate piping). To minimize corrosion, the dissolved gases must be removed or neutralized. This can be achieved through the use of deaerators, which work to remove such dissolved gases to low levels reducing the amount of follow-up neutralization required (e.g., sulfite-based oxygen scavenging).

“Where a choice is available, the reduction or removal of objectionable constituents by pretreatment external to the boiler is always preferable to, and more reliable than, management of these constituents within the boiler by internal chemical treatment.”  ASME Consensus on Operating Practices for the Control of Feedwater and Boiler Water Chemistry in Modern Industrial Boilers

What is Deaeration?
Undesirable dissolved gases, such as oxygen, carbon dioxide, and ammonia, have reduced solubility at higher temperatures (see Figure 1). Deaeration uses mechanical equipment to not only increase the temperature of the water but to increase the surface area of the water for more efficient heat and dissolved gas transfer.

Deaeration Equipment
Deaerators are typically designed with two sections.  In the first section, unwanted dissolved gases are removed from feedwater. The second section stores the deaerated boiler feedwater, where additional boiler chemistries may be applied prior to the water being introduced to the higher-pressure boiler system. Two primary deaerator designs include tray-type and spray-type systems.

Tray-Type Design
Water is distributed into the deaeration space flowing down trays to create droplets, thus increasing the water’s surface area.  Low-pressure steam is supplied to increase the temperature of the water and drive off the undesirable dissolved gases. The deaerated water then flows into a storage section.

Spray-Type Design
In a spray-type deaerator, the process functions similarly to a tray-type deaerator, except water is broken into droplets by spray nozzles instead of trays.

Venting in Deaeration
The dissolved gases removed from boiler feedwater through deaeration must go somewhere. Hence, the need for venting. Deaerators are designed with vent piping directed to the atmosphere. There will be a visible plume of steam leaving the vent, particularly on colder days. The required amount of venting will depend upon the efficiency and maintenance of the deaerator equipment, but general rules of thumb include:

  • 15 to 30 inches of actively moving plume
  • An invisible area between the vent exit and the plume

Ultimately, determining how much venting is actually needed will require testing for the removal of the objectionable dissolved gas (e.g., dissolved oxygen testing in the boiler feedwater using a meter or reagent-based test kit)

Understanding Deaerator Benefits
Operating an efficient steam boiler system involves more than just producing steam. It involves controlling fuel usage, managing water consumption, preventing scale, minimizing corrosion, operating safely, and reducing the Total Cost of Operation. Deaerators are a key component in boiler systems to help minimize equipment-damaging, maintenance-cost-increasing corrosion. The minimum amount of steam seen leaving the deaerator vent (if properly controlled) is not a waste but an investment in protecting the boiler water system instead.

As a global leader in custom-designed water treatment programs, Chem-Aqua has the experience, knowledge, and technology to effectively help manage your deaerator and complete boiler system. Since 1919, our success has been built upon our Total System Approach providing solutions for water treatment problems and improving water system efficiencies. To learn more, contact Chem-Aqua today!

Figure 1:  Maximum Solubility of Oxygen in Water

Follow us on social media for the latest updates in B2B!

Image

Latest

future of healthcare
Leading Through Change: Dr. Kevin Stevenson on Workforce, Innovation, and the Future of Healthcare
October 1, 2025

Healthcare is at a critical turning point, where staffing pressures, shrinking reimbursements, and rising patient expectations are reshaping the future of healthcare. According to the AACN Nursing Workforce Fact Sheet, the federal government projects more than 203,000 new registered nurse positions will be created annually from 2021 to 2031, reflecting high demand from an…

Read More
Non-traditional students
Holistic Support in Higher Ed: Why Non-Traditional Students Need More Than Just Financial Aid
October 1, 2025

Non-traditional students—adult learners, student parents, veterans, and first-generation college-goers—are carrying heavier burdens than ever. Upswing’s 2024 Ana Insights Report found that nearly nine in ten students intended to complete a FAFSA application, while many also sought help with essentials like food, housing, and bill payments. Perhaps most concerning, students expressed declining confidence in higher…

Read More
EAA AirVenture
From Ground to Sky: How Icom Radios Connect Crews, Docks, and Air Traffic at AirVenture 2025
October 1, 2025

Nestled in the shaded quiet of Oshkosh’s Seaplane Base, there exists a side of EAA AirVenture that many attendees never see. Unlike the bustling main grounds, the Seaplane Base operates for just one week each year, transforming from an unused shoreline into a hub of aviation activity. It takes hundreds of volunteers and days…

Read More
Seaplanes
Clear Signals, Safe Waters: Why Icom Radios are Key to Seamless Seaplane Operations at AirVenture 2025
October 1, 2025

At the heart of EAA AirVenture 2025, the Seaplane Base offers a unique glimpse into aviation’s most delicate dance—where water and air meet. Unlike traditional runways, this floating airfield demands a constant balance of precision, coordination, and communication. Here, pilots don’t just rely on their own skill; they depend on an entire team of…

Read More