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Why the steam lowers the pH in the process of expansion in turbine equipment? 1
- Thread starter Espcex92
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If you are using organic oxygen scavengers or organic amines then they ultimately breakdown into CO2 , which forms carbonic acid in the pre-condensate film on the condenser tubes.
The chemicals added in the DA have to end up somewhere- what goes in must go out. As the feedwater enters the steam drum some chemicals remain in the boiler water and are blown down to the flash tank via the continuous blowdown line. The high iron content of the boiler water acts as a catalyst to breakdown some of the chemicals The fraction that passes into the steam phase are sometimes thermally cracked in the superheater ( espescially in duct fired HRSG's) and CO2 and hydrocarbons are the end result.
Once the steam finalyy arrives at the condenser , there occurs another split of chemicals- some passes to the precondensate ddroplets , and some chemical amines escape with the noncondensibles to the SJAE or vacuum pump vent. The CO2 forms carbonic acid, and the pH at teh interface between setam and pre-condensate has a lower pH - this leads to FAC of the ACC CS tubes. See papers by Barry Dooley on this issue.
"Whom the gods would destroy, they first make mad "
The chemicals added in the DA have to end up somewhere- what goes in must go out. As the feedwater enters the steam drum some chemicals remain in the boiler water and are blown down to the flash tank via the continuous blowdown line. The high iron content of the boiler water acts as a catalyst to breakdown some of the chemicals The fraction that passes into the steam phase are sometimes thermally cracked in the superheater ( espescially in duct fired HRSG's) and CO2 and hydrocarbons are the end result.
Once the steam finalyy arrives at the condenser , there occurs another split of chemicals- some passes to the precondensate ddroplets , and some chemical amines escape with the noncondensibles to the SJAE or vacuum pump vent. The CO2 forms carbonic acid, and the pH at teh interface between setam and pre-condensate has a lower pH - this leads to FAC of the ACC CS tubes. See papers by Barry Dooley on this issue.
"Whom the gods would destroy, they first make mad "
I worked in a plant where we used weak acid cation dealkalizers ahead of the water softeners, for boiler make-up.
Naturally occurring bicarbonate alkalinity in boiler make-up water breaks down into CO2 under boiler conditions. This CO2 is carried out of the boiler harmlessly - until the steam condenses. The CO2 dissolves in the condensate, resulting in a pH of about the same as soda pop.
The requirement for dealkalizers, and whether they are installed before or after the softeners is totally dependent upon local water conditions.
Naturally occurring bicarbonate alkalinity in boiler make-up water breaks down into CO2 under boiler conditions. This CO2 is carried out of the boiler harmlessly - until the steam condenses. The CO2 dissolves in the condensate, resulting in a pH of about the same as soda pop.
The requirement for dealkalizers, and whether they are installed before or after the softeners is totally dependent upon local water conditions.
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