Repost: 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.
Please suggest for remedy, as chemical consumption and heat loss ( through CBD & IBD) has increased?

 

[mxmaciek]

Try to replace the TSP with caustic soda. In some cases, the CT (caustic treatment) can be viable alternative to the TSP. As I remember, EPRI issued some papers for that.

 

[plumberet]

Could there be something in the BFW / BW which is "eating" up the pH ? Organic acid ?

We managed to increase the boiler water pH via increasing the morpholine injection. Increase further on your morpholine ?

On PO4, sometimes we see higher pH with higher PO4 and sometimes not. So difficult to advise here. Your PO4 is on the high side.

Analyse the boiler water and see what is in there which causes the lower pH ?

Good luck !