page_title: Deaerator
section_title: Spray cum tray-type deaerator
hierarchical_section_title: Deaerator / Types / Spray cum tray-type deaerator
caption_attribution_description: I am the author and I drew this myself using Microsoft's Paint program. It is intended for the en:Deaerator article in Wikipedia and anywhere else it may be useful. Suggested caption: Diagram of boiler feed water deaerator (with vertical, domed aeration section and horizontal water storage section) - mbeychok 15:32, 31 May 2007 (UTC)
context_page_description: A deaerator is a device that removes oxygen and other dissolved gases from liquids. Deaerators are commonly used to remove dissolved gases in feedwater for steam-generating boilers. Dissolved oxygen in feedwater will cause serious corrosion damage in a boiler by attaching to the walls of metal piping and other equipment and forming oxides. Dissolved carbon dioxide combines with water to form carbonic acid that may cause further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight or less, as well as essentially eliminating carbon dioxide. The deaerators in the steam generating systems of most thermal power plants use low pressure steam obtained from an extraction point in their steam turbine system. However, the steam generators in many large industrial facilities such as petroleum refineries may use whatever low-pressure steam is available.
context_section_description: The typical spray & tray-type deaerator in Figure 1 has a vertical domed deaeration section mounted above a horizontal boiler feedwater storage vessel. Boiler feedwater enters the vertical deaeration  section through spray valves above the perforated trays and then flows downward through the perforations. Low-pressure deaeration steam enters below the perforated trays and flows upward through the perforations. Combined action of spray valves & trays guarantees very high performance because of longer contact time between steam and water. Some designs use various types of packed beds, rather than perforated trays, to provide good contact and mixing between the steam and the boiler feed water.
  The steam strips the dissolved gas from the boiler feedwater and exits via the vent valve at the top of the domed section. Should this vent valve not be opened sufficiently the deaerator will not work properly, causing high oxygen content in the feed water going to the boilers. Should the boiler not have an oxygen-content analyser, a high level in the boiler chlorides may indicate the vent valve not being far enough open. Some designs may include a vent condenser to trap and recover any water entrained in the vented gas. The vent line usually includes a valve and just enough steam is allowed to escape with the vented gases to provide a small visible telltale plume of steam.
  The deaerated water flows down into the horizontal storage vessel from where it is pumped to the steam generating boiler system. Low-pressure heating steam, which enters the horizontal vessel through a sparge pipe in the bottom of the vessel, is provided to keep the stored boiler feedwater warm. External insulation of the vessel is typically provided to minimize heat loss.
caption: Figure 1: A schematic diagram of a typical tray-type deaerator.
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