Heat recovery is an important consideration for every steam boiler system. Any waste heat returned to the system helps increase the overall efficiency of the boiler system and lower operating costs. This article specifically looks at the potential for heat recovery from boiler blowdown.
What is boiler blowdown?
During normal operation, evaporation concentrates impurities from the boiler water inside the boiler. Blowdown is the process of removing these impurities by draining some of the water from the boiler. A small amount of water is drained continuously from the surface of the water inside the boiler. Water is also drained periodically from the bottom of the boiler. Due to the level of impurities, bottom blowdown is not used for heat recovery. Cooling water is added to reduce the blowdown water temperature and the cooled water is sent to drain.
Why should I consider blowdown heat recovery?
The boiler water removed during blowdown is full of impurities that must be removed from the boiler system, but it is also full of energy in the form of heat. Systems with higher rates of blowdown will have a greater benefit from blowdown heat recovery and systems with a surface blowdown rate higher than 5% are good candidates. Blowdown heat recovery systems offer the opportunity to recover heat from the blowdown water and use the flash steam for low-pressure applications, such as feedwater deaeration.
What are my options for blowdown heat recovery?
Blowdown heat recovery systems are typically heat exchangers or a flash tank with a heat exchanger. The most common system recommended is the flash tank with a heat exchanger. Using the flash tank with heat exchanger as an example, water from the continuous blowdown enters the tank and separates into flash steam and water. The flash steam can then be sent to a low-pressure process, such as a deaerator. The hot water in the flash tank is then used to heat the cold water makeup supply for the boiler feed or deaerator system. The cooled blowdown water is then sent to the blowdown separator or blowdown tank, where it will require substantially less cooling water before it is sent to drain.
Blowdown Heat Recovery System Flash-Type Heat Recovery System
If your system is a good candidate for blowdown heat recovery, blowdown heat recovery can be an excellent tool to improve overall system efficiency and generate cost savings using heat that would be wasted otherwise. We represent the entire line of Cleaver-Brooks Heat Recovery Solutions. Contact Boiler Supply Co. for system analysis and see if blowdown heat recovery is right for your boiler system.