Catalyzed sulfite and bisulfite oxygen scavengers u2014 sodium sulfite, sodium bisulfite, and ammonium bisulfite u2014 for removing dissolved oxygen from boiler feedwater and deaerator effluent.
Oxygen scavengers are reducing agents added to boiler feedwater to remove thendissolved oxygen that mechanical deaeration leaves behind, preventing oxygen pitting ofnfeedwater piping, the deaerator, and boiler tubes. Sulfite-based scavengers reactnwith dissolved oxygen to form sulfate; catalyzed grades, accelerated with a trace of cobalt,nreact fast enough to scavenge oxygen in the few seconds of contact time a feedwater linenallows. Dose to a small measured residual rather than to a fixed rate.
nnSodium sulfite, sodium bisulfite, and ammonium bisulfite cover most low- andnmedium-pressure boilers. They are inexpensive and fast, but each reaction adds dissolvednsolids to the boiler water, which raises blowdown and the heat lost with it. Sulfite chemistrynalso has a ceiling: above roughly 900 psi it can break down to corrosive sulfur dioxide andnhydrogen sulfide that carry into the steam. Keep sulfite programs within the pressure range thenboiler maker allows.
nnAbove that range, plants switch to volatile organic scavengers such as DEHA orncarbohydrazide, which add no dissolved solids and carry forward to passivate the condensatensystem. RawSource currently sources the sulfite-based scavengers rather than the organic ones,nso for high-pressure service confirm the chemistry and grade against your boiler's pressurenrating before specifying. Ammonium bisulfite suits oilfield and pipeline water but releasesnammonia, which is incompatible with copper alloys.
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