BOILER DRUM CBD pH PROBLEM

[chemjay]

We have two HRSGs of 80 TPH @ 105 Kg/cm2 & 500 Deg.C, running at 75 TPH. We are facing some problem regarding maintaining of Steam drum pH, Although BFW pH is >8.8 by adding Morpholine. Steam drum pH is not increasing beyond 8.8 ( some times come downs to 8.6) even after dosing TSP in steam drum, and our lab analysis is giving Phosphate > 10 ppm. Also IBD are given frequently and CBD has also increased to maintain Phosphate and conductivity.
But months back in same condition pH were nearly 9.0.
Can anyone suggest for remedy, Please as chemical consumption and heat loss ( through CBD & IBD) has increased?

 

[rngrrix]

Chemjay - Do you have a closed cooling system where glycol mixtures are cooling condensate pumps or water/steam samples? I had a problem where the pH would depress boiler chemistry when a trace amount of glycol leaked into a condensate cooler as it breaks down into an organic acid. As a temporary measure I would add NaOH to your chemical day tanks. Start with about 25mls of 50% NaOH which should help elevate pH and reduce blowdown until you can find source of contamination.

 

[chemjay]

Thanks rngrrix,
But we don't have Glycol system. Also we had CPU (condensate polishing unit) as well as DM plant. Also any contamination is not seems to be there as conductivity is normal.