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Why Should Plants Use a Deaerator for Boiler Feed Water?

Why Should Plants Use a Deaerator for Boiler Feed Water?

Deaerators are large, tank-car-shaped, pressure vessels designed to produce preheated boiler feed water and bolster the efficiency of the boiler's operation. In addition to preheating the feedwater, deaerators remove oxygen and carbon dioxide. These vital pieces of equipment are available in a variety of shapes, sizes, steam pressure ratings, and capacities. Continue reading to learn more about how a deaerator for boiler feed water can bolster performance and efficiency.

Why Should Plants Utilize a Deaerator?

Depending on the design and size of your plant, the amount of feed water required can be small or exceptionally large. Certain applications allow the steam condensate to be recycled back into the boiler and be used as a component of the feed water. The rest of the water comes in as makeup or fresh water.

Whether the makeup water is sourced from a water well or your local utility, it will usually be cold, contain a lot of oxygen, as well as other dissolved gases. Regardless of the amount of condensate returns you produce, the makeup water must be appropriately conditioned before it is processed as feedwater.

Goals of a Deaerator

Chemical and mechanical deaeration are both integral parts of modern boiler water protection. When mechanical deaeration is coupled with other external treatment aspects (chemical deaeration), it provides the highest quality feed water for boiler use. According to the 2015 ASHRAE handbook on water treatment, this conditioning process looks to achieve four different goals:

  1. Heat the cold water to prevent thermal shock to boiler.

  2. Remove dissolved oxygen to reduce the need for other water treatment chemicals.

  3. Remove other dissolved gas to prevent carbonic acid corrosion and oxygen pitting.

  4. Remove non-condensable gases to bolster steam potential and efficiency.

Deaerator Design

A mechanical deaerator is specifically designed to achieve three of the goals mentioned above. The equipment is usually elevated to generate additional pressure on pumps that are situated at a lower level. This setup allows the hotter water to be pumped without locking up in the event steam enters the pump. Deaerators are commonly a combination of two different vessels:

  • One vessel for scrubbing or removing non-condensable gasses and oxygen.
  • A second vessel for holding hot feedwater.

This two vessel design provides superior efficiency and results - in comparison to only having a single steam heated feed water tank. The first vessel effectively scrubs the water and breaks it up into tiny droplets, so dissolved gases and oxygen are removed.

After being removed, the gases are vented out before being fed through to the storage section. As a result of the process, higher quality feed water is produced with lower concentrations of non-condensable gases and dissolved oxygen. This leads to superior steam quality and reduced operating costs.

Benefits of Deaerators for Boiler Feed Water

Deaerators for boiler feed water offer a long list of benefits to virtually any steam-plant system. Some of the key benefits include:

  • Removal of carbon dioxide (CO2) and oxygen (O2) from feed water to reduce corrosion.
  • Serves as a surge collection source for condensate return from the process.
  • ​Increases efficiency from preheating feed water.
  • ​Blends cold makeup water and hot condensate.
  • ​Provides a location for blending and feeding chemicals and testing protocol.
  • ​Store treated water in a reserve storage for load change.
  • ​Provides a convenient location for feedwater test data and instrument controls.
  • Delivers a continual, pressurized supply of water to boiler feed pumps
  • Helps to ensure precise pressure inside of the boiler and drum water level.

Boiler Efficiency and Deaerator Performance

Deaerators for boiler feed water are a vital component to a reliable feed water system. At the same time, it can be the heart of your thermal-energy and boiler mass-flow database used to identify energy-saving opportunities and critique plant operations.

Whether you're operating a smaller 300-hp firetube unit or a larger 80,000-pph watertube boiler system, failure to effectively monitor feed water system performance can lead to significant energy loss. If boiler efficiency is not at peak performance, a critique of the feedwater system and implementation of a deaerator for boiler feed water can be revealing.

Contact ATI of New York

The removal of dissolved gases from boiler from feedwater is a key process in an efficient system. If oxygen and other gases are left untreated, it will lead to rapid localized corrosion throughout the boiler tubes. In addition, carbon dioxide would dissolve in the water and cause a drop in pH levels, which would produce corrosive carbonic acid.

Although low pH levels and dissolved gases in the feedwater can be removed or mitigated through the use of chemicals, it's often more thermally efficient and economical to remove the gases through mechanical deaeration. In the end, deaeration will bolster the life and production of the steam system.

Contact Applied Technologies of New York today to learn more about how our deaerators can bolster the performance of your equipment.

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