A continuous blowdown line is located:

The continuous blowdown line is designed to remove impurities and sediment from the boiler water, ensuring that the water quality remains within safe operational limits. This line is typically located in the steam and water drum, well below the nowl (the part of the boiler where water and steam separate).

Being placed in this position allows for efficient removal of concentrated impurities that settle at the bottom of the drum. The continuous nature of the blowdown minimizes the risk of boiler scale and corrosion, promoting the longevity and safe operation of the boiler. By removing contaminants directly from this area, the system maintains higher quality water in the boiler, reducing the likelihood of overheating and potential failure.

Other locations listed, such as being above the steam drum or near the feedwater inlet, would not facilitate proper blowdown functionality. The blowdown needs to occur at the lowest point in the boiler system to effectively remove the settling impurities that naturally accumulate. Thus, placement in the steam and water drum below the nowl is crucial for optimal operation.