Which chemical should be added to boiler feedwater to prevent oxidation of the boiler drum and tubes?

Sodium sulfite is commonly used in boiler systems to prevent oxidation of the boiler drum and tubes. When added to the feedwater, sodium sulfite acts as an oxygen scavenger, effectively reacting with dissolved oxygen in the water to form sodium sulfate. This reaction reduces the amount of free oxygen present in the boiler system, which is a primary contributor to corrosion and oxidation of the metal surfaces.

Using sodium sulfite is particularly important in high-pressure boilers, as the high temperatures and pressures can exacerbate corrosion issues. By controlling the oxygen levels, sodium sulfite helps maintain the integrity and longevity of the boiler components, ensuring safe and efficient operation.

Other chemicals listed, such as calcium sulfate, caustic soda, and potassium bicarbonate, do not have the same oxygen scavenging properties and are used for different purposes in water treatment. Calcium sulfate is typically associated with hardness control, caustic soda is often used to maintain pH levels, and potassium bicarbonate might be used for buffering or adjusting alkalinity, but none of these effectively target the prevention of oxidation like sodium sulfite does.