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

Commerce media
A Look at the Rise of Commerce Media Networks: How Nift Helps Brands Own How Their Message Shows Up
July 2, 2025

As traditional digital advertising struggles to retain consumer trust, brands are exploring new, more authentic ways to connect with shoppers. Platforms like commerce media networks, which weave together commerce, content, and data, are emerging as powerful tools in this shift. Research from MG2 Advisory reveals that only about 37% of consumers feel brands genuinely…

Read More
Hospitality leadership
Heart-First Hospitality Leadership: How Saying ‘Yes’ Transforms Guest Experiences, Boosts Staff Morale, and Drives Business Results
July 2, 2025

As the hospitality industry emerges from years of pandemic-driven upheaval, hospitality leadership is evolving to meet new challenges. Leaders are looking for new ways to retain staff, elevate guest satisfaction, and drive revenue without burning out their teams. One trend gaining traction is the power of “Yes”: empowering employees to say yes more often,…

Read More
civic leadership
Mayor Gerard Hudspeth’s Civic Leadership Journey: What Politics Teaches About People
July 2, 2025

What does a mayor learn about human nature? In this episode of Professional Quotient: Conversations that Build Equity, host Jason Winningham sits down with Gerard Hudspeth, longtime mayor of Denton, Texas, and a respected figure in civic leadership. Drawing from his years in public service, Hudspeth explores how leading a city reveals the core…

Read More
sepsis
Debunking Sepsis Myths – Episode 1
July 1, 2025

In the first episode of The Michael Rothman podcast, we address misconceptions about sepsis in healthcare. Although it’s often claimed that sepsis accounts for nearly a third of hospital deaths, many of these deaths are linked to chronic conditions with sepsis as a secondary factor. The frequently cited statistic that delays in treating sepsis increase…

Read More