Recovering heat from the boiler blowdown process can boost energy efficiency and reduce operating costs. There are numerous techniques for recovering heat during boiler blowdown, which is the process of removing accumulated sludge, silt, and contaminants from the boiler in order to keep it running efficiently.
Here are some common methods:
Blowdown heat recovery system:
This involves using a heat exchanger to transfer heat from the hot blowdown water to the incoming feed-water. The heat exchanger can be designed to utilise either the sensible heat or the latent heat of the blowdown water, depending on the design and operating conditions of the boiler. Sensible heat recovery involves transferring the heat from the hot blowdown water to the cooler feed-water without changing the phase of the water, while latent heat recovery involves transferring the heat associated with the change in phase of the blowdown water from liquid to vapour.
Flash tank or blowdown separator:
This method involves allowing the hot blowdown water to flash into steam in a lower pressure vessel, such as a flash tank or blowdown separator. The steam generated can be used for various purposes, such as preheating feedwater.Heat pump systems:
Heat pump systems can be used to recover heat from the boiler blowdown process by utilising the heat from the hot blowdown water to drive a heat pump, which can then upgrade the heat to a higher temperature for use in other applications, such as space heating or process heating.Condensing economiser:
This method involves using a condensing economiser, which is a heat exchanger that is specifically designed to recover heat from the flue gas of a boiler. The blowdown water can be used as the coolant in the condensing economiser, allowing the heat from the blowdown water and the flue gas to be transferred to the incoming feedwater.Thermal storage systems:
Thermal storage systems can be used to recover heat from the blowdown process by storing the excess heat during periods of low demand and releasing it during periods of high demand. This can help improve the overall efficiency of the boiler system by utilising the excess heat that would otherwise be wasted during the blowdown process.Heat pipe technology:
Heat pipe technology involves using a passive heat transfer device called a heat pipe, which can transfer heat from the hot blowdown water to the cooler feed-water through a vaporisation-condensation process. Heat pipes can be used in various configurations to recover heat from the boiler blowdown process, depending on the specific requirements of the boiler system.
It's important to consider the specific design and operating conditions of your boiler system, as well as the cost and feasibility of implementing these heat recovery methods, to determine the most suitable option for your application.