Drum: It is a cylindrical vessel in natural circulation and multiple forced circulation boilers that receives feedwater from the economizer, connects the circulation circuit, and delivers saturated steam to the superheater. The drum body is made of high-quality thick steel plates and is one of the heaviest components in the boiler.

The main functions of the drum are to store water, perform steam-water separation, and discharge brine and sludge from the boiler water during operation to prevent boiler water with high concentrations of salts and impurities from entering the superheater and steam turbine along with the steam. If these salts and impurities cause scaling, salt deposition, and corrosion in the superheater tubes and steam turbine passages, they can affect the economic and safe operation of the equipment. The steam at the boiler outlet generally meets certain quality standards. The internal devices of the drum include steam-water separation and steam washing devices, feedwater distribution pipes, blowdown and chemical dosing equipment, etc. The steam-water separation device separates saturated steam from the water coming from the water-cooled walls and minimizes the fine water droplets carried in the steam. Medium and low-pressure boilers commonly use baffles and gap baffles as coarse separation elements. In boilers above medium pressure, various types of cyclone separators are widely used for coarse separation, followed by further separation using louvers, wire mesh, or steam distribution plates. With advancements in water treatment technology, steam separation devices tend to be simplified and standardized. Blowdown devices (including continuous and periodic blowdown) can discharge a portion of boiler water containing higher salts and sludge during boiler operation. The drum is also equipped with monitoring and protection facilities such as water level gauges and safety valves.