Blowdown tanks are used as an alternative system for cooling the bottom boiler blowdown. These large tanks retain the blowdown water volume from one blow after the flash steam has been vented to the atmosphere and allow the water to cool down by natural convection over 6-12 hour period. The cooled water will be below 140° Farhrenheit when it is displaced by the next blowdown and forced out of the overflow drainpipe.
These heavy steel tanks receive the bottom blowdown water from a boiler and cool it down using the flash steam principle, along with convection cooling over several hours for the retained hot water. The tank is designed to breakup the blowdown flow by impacting the high pressure hot water on the steel centrifugal impact plate. The water droplets give up heat as flash steam is formed. The flash steam is vented from the top of the tank to the atmosphere. Retained water displaces cooled water from the previous blowdown, and is retained in the tank until it cools to the statute limts.