Why the steam lowers the pH in the process of expansion in turbine equipment? Could someone show me some literature that best explains this phenomenon?
I never heard anything about expansion affecting ph.
There may be volatile additives which maintain basic condensate/feed system ph and are carried through the entire loop - boiler to condensate and feed and back to boiler.
there are no measurements for steam pH so assuming for the moment you are describing some point in the condensate return system, just where are you taking the condensate sample and what is the sample temperature.
you also need to be specific regarding the the boiler pressure and the sort of water treatment program you have in place.
Where, I worked the last year, after being expanded in the turbine condensing, the superheated steam's condensate generates a pH of about 3 and to be reused in the process needs to have its pH adjusted to about 8. This is done with the use of amine (usually morpholine). I would like to understand what explains this decrease in pH of the condensate in the expansion of the steam in the turbine.
Is the condensate being used to scrub the exhaust? Dunno how else you'd get enough exposure to CO2 (which wouldn't explain a pH of 3) or other acid compounds (NOx, SOx).
That said, typical condensation systems are not exactly designed to produce pure water, and may contain biologicals as well as inorganic contaminants. A pH of 3, which is pretty acidic, would suggest a fairly substantial contamination with ions.
TTFN
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Or it could be an artifact of the measurement.
Most pH probes are better thermometers than they are selective ion measuring tools.
The temperature compensation setting on the meter does not compensate for what is happening in the sample or probe, only the meter.
Between temp errors and the volatilizing of the amine I can see a downward shift.
I don't know what's happening exactly, but the reduction of the pH in expansion of the turbine is a fact! No doubt about it!Perhaps a physical-chemical phenomenon? Perhaps an imbalance of ions H+ caused by the expansion of the steam turbine?
Contamination with ions or error read's interpretation of the pH probes? I'm not sure about that! Actually, I don't believe that! I still believe on phenomenon physical-chemical.
Chicopee's assumption is apparently correct. Carbon dioxide is a normal by-product of the breakdown of boiler water alkalinity, and occurs in most boilers to varying degrees.
A link on this subject:
Do you already heard about: Kp = equilibrium constant in terms of partial pressure and its relationship with Kc = equilibrium constant in terms of concentration? { Kp = Kc.(RT)^n} ... Then, I think it can explain what I'm telling!
Let's not forget the mentioned link speaks about atmospheric CO[sub]2[/sub], with a concentration quite different from that expected in the water of a turbine condenser.
fantastic response given the incomplete description of the problem actually being encountered, pretty soon we can add solar neutrinos and global warming!