What Is Blow-Down Heat Recovery for Boilers?

Using a heat exchanger blowdown waste heat can be recovered. It requires lowering the pressure in a flash tank to allow a portion of the blowdown to be turned into low-pressure steam. The use of this low-pressure steam is most typically seen in deaerators. The drain water from the flash tank then routs into the heat exchanger. Cooling the blowdown serves as an additional advantage.

To produce steam in the boiler, it requires feed water. Feed water is actually a mixture of returned condensate and treated make-up water. No matter how much economically justifiable efforts of treating feed water there, a small amount of dissolved solids (TDS) is always there in the feed water. The TDS accumulate in the boiler as the water gets evaporated to produce steam.

Generally, a small amount of water from the boiler steam drum is discharged or released. This process reduces the dissolved solids level and mitigates deposits of solids in the steam drum. 

Many boilers allow for constant water discharge (blowdown) of water. This manages the dissolved solids levels. The blowdown heat recovery rate can be between less than 1% at the time of using extremely high-quality feed water and greater than 20% in a system that has a deficient quality of feed water. Makeup water has inside it a substantial percentage of the total heat input for the boiler. In many cases, the water and its heat content go directly to the drain. This leads to the wasting of energy and water. For safe TDS level maintenance, the quantity of blow-down should be controlled and experts recommend recovery of heat from blowdown water.

O’Brien Boiler Services Pty Ltd is assisting businesses to carry out better everyday industrial activity by engineering boiler energy solutions with steam, hot water, combustion and process heating systems.