7 replies to this topic

[mohsan]

Hello Everyone

We are facing low pH (9.0~9.2) problem in our both boilers CBD samples since past month. We have one Auxiliary boiler operating at 50~70 ton/hr and one HRSG at 92ton/hr both producing steam at pressure of 39 Kg/cm2 (both boilers are water tube). Demineralized water is being used as fresh make up along with condensate return from Urea and DAP plants as boiler feed water after passing from tray type Deaerator. Amine treatment (ammonia solution) to control pH and Tri-sodium phosphate is being used as scale inhibiter. All other parameters remained normal along with pH of Demin. Water (7.0~7.5), condensate returns (10.1~10.2) and steam produced in boilers (10.1~10.2). There is not any leakage reported from process plants and all four types of condensate returns are none contaminated. Can anyone tell the possible cause and proposed solution of this problem? Thanks in advance.

[thorium90]

Is your make up rate still the same?

[breizh]

hi ,

To support your work.

Good luck

Breizh

[P.K.Rao]

Please increase TSP dosage.

[mohsan]

The make up rate is 30~40 m3/h higher but amine and TSP dosing rate also increased accordingly which maintained the pH of steam (10.1~10.2) and PO4 contents (~25ppm) in boilers CBD within the limits.  The main problem is low pH of boilers CBD.

Mr. P. K. Roy how much we can increase the TSP, we did it previously (about 35~40ppm) but no improvements observed. Is there is any signs of phosphate hide out in our system.

[thorium90]

Its possible then that the higher makeup rate could be causing the low pH. Try bringing your blowdown phosphate to about 35ppm with more TSP dosing. If the conductivity is still ok, you can increase ammonia dosage too.

 

Perhaps you might want to find out why the makeup rate is now higher. Was it sudden? Could there be a tube leak, or some passing valves?

Edited by thorium90, 26 July 2015 - 07:28 AM.

[P.K.Rao]

Keep a check on sodium to phosphate mol ratio while increasing dosage of TSP. A value recommended by a few authors is 2.6 to 2.8..Excess of phosphate may cause phosphate hide-out. Keep a watch on boiler drum TDS. Please refer to ASME recommendations on TDS.

[breizh]

Hi ,

As per P.K Rao recommendations .

 

You may find assistance from the vendor of chemicals for your boiler . Tube leak ?

 

Hope this helps .

 

Breizh