Drum blowdown

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The drum blowdown is usually carried out using a combination of continuous blowdown and periodic blowdown. (1) Continuous drainage is mainly used to discharge the concentrated water from the upper part of the drum, with the aim of preventing excessive salt and sulfur content in the boiler water. The drainage points are usually located where the concentration of water in the drum is highest, that is, at a depth of 200–300 mm below the drum water level. The continuous blowdown rate is usually adjusted based on the water quality analysis parameters of the drum water. (2) Periodic slag discharge, also known as intermittent slag discharge, involves removing the sludge and dirt accumulated at the bottom of the boiler at regular intervals. This is typically done every 8 to 24 hours, with each discharge lasting 0.5 to 1 minute; the discharge rate should be no less than 1%. It is better to carry out intermittent slag discharge frequently and over short periods, as this helps to achieve a uniform concentration of water in the steam drum, thereby improving the quality of the steam.