Increased Efficiency and Heat Retention

Boiler blowdown is the removal of water from a boiler drum. Its purpose is to control boiler water parameters within prescribed limits to minimize scale, corrosion, carryover, and other specific problems. Blowdown is also used to remove suspended solids present in the system. Often, blowdown is controlled manually and requires Operations to make frequent trips to field to adjust the flow of the valve based on operating load and water quality measurements. When not adjusted accurately or frequently, excess treated water is dumped which increases costs. 

Continuous blowdown, as the term implies, is the continuous removal of water from the boiler. It offers many advantages not provided by the use of bottom blowdown alone. For instance, water may be removed from the location of the highest dissolved solids in the boiler water. As a result, proper boiler water quality can be maintained at all times. Also, a maximum of dissolved solids may be removed with minimal loss of water and heat from the boiler.

Another major benefit of continuous blowdown is the recovery of a large amount of its heat content through the use of blowdown flash tanks and heat exchangers. Valve settings must be adjusted regularly to increase or decrease the blowdown according to control test results and to maintain close control of boiler water concentrations at all times. When continuous blowdown is used, manual blowdown is usually limited to approximately one short blow per shift to remove suspended solids which may have settled out near the manual blowdown connection.