Question about scavenged oxygen system in boilers
Question about scavenged oxygen system in boilers
(OP)
I have a water tubed boiler at our steam facility. The boiler feed water is oxygen scavenged by a DEHA system. 98% of the oxygen is taken out of the system. Then Phosphate is used to take out the other 2% of oxygen out of the boiler feed water. The way the plant operates the boiler is not what the manufacturer operation suggest. Basically we go from a hot stand by to a cold stand by mode. Cold standby is basically letting the boiler cool down to atmosphere. So during the transition of hot stand by to cold standby the superheated steam in the boiler condenses to condensate and sits in the superheater tubes. If oxygen is scavenged out of the system how does it get back into the system during condensing??? There was severe damage of oxygen pitting in the superheater tubes. So oxygen was in the system. we have weekly reports of DEHA (excess scavenged oxygen residual). Reports are above the recommeneded levels. Any help would be appreciative.





RE: Question about scavenged oxygen system in boilers
Oxygen Scavengers
Good luck,
Latexman
RE: Question about scavenged oxygen system in boilers
rmw
RE: Question about scavenged oxygen system in boilers
Did I understand you right rmw??
RE: Question about scavenged oxygen system in boilers
rmw
RE: Question about scavenged oxygen system in boilers
RE: Question about scavenged oxygen system in boilers
RE: Question about scavenged oxygen system in boilers
RE: Question about scavenged oxygen system in boilers
Nitrogen blanket is easy and cheap, a nitrogen cylinder, regulator with 1 PSIG setting, a check valve so that when the boiler is fired steam will not wreck the nitrogen regulator. Another option is to draw a high vacuum on the boiler continuously with a vacuum pump, this also works but you have to get the proper vacuum pump, liquid ring and oil filled pumps are not appropriate, use a dry vacuum pump capable of hig vacuum.
RE: Question about scavenged oxygen system in boilers
I think you would need to add a leakage relief valve on the LP pipe system if the only other protection is a check valve.
RE: Question about scavenged oxygen system in boilers
RE: Question about scavenged oxygen system in boilers
The deaerator will admit air/oxygen when it cools down.
Also, you state: "...the superheated steam in the boiler condenses to condensate and sits in the superheater tubes."
Your boiler internal design is not the best....Most modern superheater boiler designs call for a fully draining tubes.