Flash Steam from Blowdown 1

[ksjm019]

Does boiler blowdown contain vapor? I always thought it was just hot condensate (liquid state) but when I keep hearing the “amount of vapor and liquid” in the blowdown line from steam drum going into the blowdown drum to recover the flash steam, it just confuses me. Can someone please explain? Why mention vapor in blowdown when all it is just hot condensate (in liquid state)?

 

[Shmulik]

Flash steam is generated once the pressure of water blowdown is reduced. Water temp. of boiler's vapor pressure is higher than of the new situation. It causes some of blowdown water to vaporize.
Percentage of flash steam formed can be easily calculated:

http://www.spiraxsarco.com/resources/calculators/flash-steam/saturated-condensate.asp

Commonly, steam boiler's water blowdown drained to a flash tank that should be properly designed for this purpose:

http://www.pennseparator.com/pbs6.htm

This topic has been widely discussed here on the forums:

thread794-184415
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