โ Scribed by J.W. Oldfield; B. Todd
No coin nor oath required. For personal study only.
The chlorination of sea water has been considered in detail, with particular reference to the oxidation of bromide ions, already present in sea water, to bromine by the chlorine_ It has been shown that under normal conditions of sea vater chlorination the bromide ions vill rapidly be oxidised to bromine. hypobromous acid and hypobromite ion, bromine being the predominant form at pH values of 6 and less. Tht significance of this work to NSF desalination plants is that acid treated plants provide conditions suitable for bromine gas formation in the decarbonator and deaerator. It has been calculated that for such plants operating with residual chlorine levels in the range 0.2 to 0.5 ppm the condensates from the steam that has passed through the deaerator into the vent system could well contain betveen 10-100 ppm Br2; these levels of bromine can cause severe localised corrosion problems with conventional stainless steels. Such corrosion has been observed in practice. Calculations indicate that providing the pU is 6 and the residual chlorine is -=0.2 ppm at the point of entry to the deaerator, the likely bromine level in the condensate in the vent system will be ~10 ppm, and this may well be low enough to prevent corrosion of type 316 stainless steel.
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