Catalyzed sulfite and bisulfite oxygen scavengers — sodium sulfite, sodium bisulfite, and ammonium bisulfite — for removing dissolved oxygen from boiler feedwater and deaerator effluent.
Oxygen scavengers are reducing agents added to boiler feedwater to remove the dissolved oxygen that mechanical deaeration leaves behind, preventing oxygen pitting of feedwater piping, the deaerator, and boiler tubes. Sulfite-based scavengers react with dissolved oxygen to form sulfate; catalyzed grades, accelerated with a trace of cobalt, react fast enough to scavenge oxygen in the few seconds of contact time a feedwater line allows. Dose to a small measured residual rather than to a fixed rate.
Sodium sulfite, sodium bisulfite, and ammonium bisulfite cover most low- and medium-pressure boilers. They are inexpensive and fast, but each reaction adds dissolved solids to the boiler water, which raises blowdown and the heat lost with it. Sulfite chemistry also has a ceiling: above roughly 900 psi it can break down to corrosive sulfur dioxide and hydrogen sulfide that carry into the steam. Keep sulfite programs within the pressure range the boiler maker allows.
Above that range, plants switch to volatile organic scavengers such as DEHA or carbohydrazide, which add no dissolved solids and carry forward to passivate the condensate system. RawSource currently sources the sulfite-based scavengers rather than the organic ones, so for high-pressure service confirm the chemistry and grade against your boiler's pressure rating before specifying. Ammonium bisulfite suits oilfield and pipeline water but releases ammonia, which is incompatible with copper alloys.
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