Dear Mr.Azim Gul Kazi, Its ...

Dear Mr.Azim Gul Kazi,

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. Even with the best pretreatment programs, boiler feedwater often contains some degree of impurities, such as suspended and dissolved solids. The impurities can remain and accumulate inside the boiler as the boiler operation continues. The increasing concentration of dissolved solids may lead to carryover of boiler water into the steam, causing damage to piping, steam traps and even process equipment. The increasing concentration of suspended solids can form sludge, which impairs boiler efficiency and heat transfer capability. In addition to proper blowdown practices, including the use of automatic blowdown control, reducing cost and heat loss associated with boiler blowdown can also be achieved through recovering the heat/energy in the blowdown.

The common impurities in raw water can be classified as follows:  

1. Dissolved solids.
2. Suspended solids  
3. Dissolved gases  
4. Scum forming substances
5. Heat,

Treatment of Boiler Condensate(Blowdown)

1. Gases removed by degaser tower, air supplied to water.
2. Ion exchange Process is the best method
3. Recycle to raw water for further treatment of water if hardness is more.
4. Heat removed by Heat exchanger i.e. BFW preheater, Installation of heat recovery equipment is valuable only when energy from the flash tank or the blowdown water can be recovered and utilized. When an excess supply of exhaust or low-pressure steam is already available, there is little justification for.
5. RO,
6. Hardness removed by pretreatments.