Deaeration and Boiler Feedwater Systems

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Questions and Answers

What is the main purpose of using deaerators in boiler feedwater systems?

  • To reduce the temperature of water in boilers
  • To remove dissolved gases from the feedwater (correct)
  • To prevent the formation of steam in the boiler
  • To increase the solubility of dissolved gases in water

How does an increase in temperature affect the solubility of dissolved gases in water?

  • It changes the type of dissolved gases in water
  • It increases the solubility of dissolved gases
  • It decreases the solubility of dissolved gases (correct)
  • It has no effect on the solubility of dissolved gases

What role does steam flow play in deaerator operation?

  • It ensures efficient mixing to support gas scrubbing (correct)
  • It increases the solubility of dissolved gases in water
  • It reduces the surface area of the water
  • It decreases the residence time of water in the deaerator

How does the use of trays contribute to the efficiency of a deaerator?

<p>It increases the surface area of the water (A)</p> Signup and view all the answers

What happens to dissolved gases when water is heated to just below its saturation temperature in a deaerator?

<p>They come out of solution and are vented (C)</p> Signup and view all the answers

What is the main problem caused by dissolved gases coming out of solution at high temperatures in boilers?

<p>Corrosion (D)</p> Signup and view all the answers

What are the two basic deaerator configurations mentioned in the text?

<p>Tray type and spray type (C)</p> Signup and view all the answers

What is the purpose of cascading water down several trays in a deaerator?

<p>To increase the surface area of the water and promote greater water-steam contact (B)</p> Signup and view all the answers

What is the function of spray nozzles in a spray-type deaerator?

<p>To break up the inlet water into small particles to promote water-steam contact (C)</p> Signup and view all the answers

In a tray-type deaerator, how is the water flow broken up for the deaeration process?

<p>By trickling down over a series of trays (D)</p> Signup and view all the answers

What is the purpose of a safety valve in a deaerator?

<p>To release excess pressure from the system (B)</p> Signup and view all the answers

What happens to the released gases and remaining steam in a tray-type deaerator?

<p>They pass to the internal vent condenser where most of the steam is condensed and gases are vented to atmosphere (C)</p> Signup and view all the answers

What is a bubbling tray deaerator designed to achieve?

<p>Agitation and intimate contact between steam and water for deaeration (D)</p> Signup and view all the answers

What is unique about a combination deaerator?

<p>It combines both spray and tray principles in the deaeration process (B)</p> Signup and view all the answers

How does a combination deaerator handle released gases and remaining steam?

<p>They pass through the incoming water spray on their way to the vent opening, causing most of the steam that is being carried with the gases to condense. (B)</p> Signup and view all the answers

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