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High Sodium/phosphate Ratio In RG Boilers

High Sodium/phosphate Ratio In RG Boilers

(OP)
Dear Experts,

In our complex we are currently facing higher sodium to phophate ratios problem in all our Boilers.

We have an integrated BFW system where interconnected de-aerators which are common for both HP BFW pumps and KP BFW pumps are installed. BFW is supplied to both the Ammonia trains which have high pressure boilers operating at about 120 Bar g pressure and four utility boilers which operate at 46 bar gauge pressure. Each Ammonia plant has a separate steam drum connected to its RG Boiler, Syn boiler and shift converter Boiler.

The problem started due to leakage in Urea HP STRIPPER. Urea train2 stripper started leaking and the steam network of urea plant has got contaminated. Subsequently Urea process condensate was being sent to DM water tanks bypassing the polishing units. This has resulted in very high PH upto 10.5 to 10.8 in the BFW network.

The Ammonia plant CBD conductivity has gone beyond 110 to 120 mmho and 120 bar pressure steam conductivity also increased upto around 50 mmho. PH remained around 10.5. All other utility Boilers also have similar parameters.

All the Boliers Sodium phosphate ratios remain higher side and particularly ammonia boilers at 120 bar have still higher ratios. We have been operating like this for about 15 days now. Is it safe to continue like this for other one or two months? Our only concern is if we stop urea plant can we detect the leak or not as urea stripper exit steam conductivity is at about 2000 mmho.

Ours is exclusive Triple sodium phosphate based BFW treatment with hydrazine and ammonia for O2 and PH control. Direct AMMONIA dosing has been stopped from first day of problem. We have never dosed DSP or MSP till to date only TSP is dosed so far in last ten years. We used to maintain Na/PO4 ratio within the range of 2.8 to 3.2.

Ammonia Boilers PH conductivity sodium/ phosphate ratios are hovering around 10.5, 75 to 100, and 9 to 11 respectively at the moment with higher CBD and frequent two hourly IBDs.

Please provide your advice and suggestions that can we continue like this and if so for how long.
With Kind Regards

RE: High Sodium/phosphate Ratio In RG Boilers

Presume you are allowing the stripper steam condensate to bypass the condensate polishing unit to prevent it from overloading.
What type of heat exchanger do you have in this train 2 HP urea stripper ? Do you have a spare bundle which you can change out quickly to minimise shutdown time?
Am not a urea plant-steam expert so hope fully some other folks can help with some temporary remedy for this..

RE: High Sodium/phosphate Ratio In RG Boilers

(OP)
Actually my concern is whether operating under this Na/PO4 and such PH and Conductivity will harm our RG boilers in ammonia plants in the short run or not?
Those boilers are operating under 120 Barg. Is there any chance for any kind of corrosion or boilers failure?

"Ammonia Boilers PH conductivity sodium/ phosphate ratios are hovering around 10.5, 75 to 100, and 9 to 11 respectively at the moment with higher CBD and frequent two hourly IBDs."

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