water wash of HRSG - remove fuel oil sulphate deposits ?

[davefitz]

Does anyone have experience with water washing of horizontal HRSG's ( heat recovery steam genderators) finned tube harps, to remove deposits of ammonium sulphate and bisulphate ?

We have a HRSG which is designed only for natural gas firing , but expect the need to fire ultra low kerosene ( 0.01% S) in the next few years due to possible natural gas shortages / curtailments. The sulphur will eventually form SO3, which will form ammonium bisulphate after combining with ammonia slip and deposit on the fins in the downstream Harps. It will cause high gas back pressure and foul the surfaces.

Q1: can one water wash if the finned tubes are staggered and not in-line?
Q2: How many rows deep can high pressure water wash penetrate?
Q3: Any idea of subcontractors in the Florida USA area?

 

[FM9779]

Am not sure what you are talking about, but I met people in Germany few months ago. I think they can help you with what you want. go to

http://www.skwsystem.com,

and grap the e-mail address from there and e-mail them. this company has done mericals to us and other huge companies in different things.

I hope you can find all you answers over there

 

[andros45]

Yes i have great experience with similar problems in cleaning fined waste heat economisers and marine boilers.
first of all washing with pure fresh water you produce very aggresive acid water which corrode very hard your boilers..
Some simple chemicals are necessary together with the washing water and propable some modifications your gasses to have temperature higher than your gasses dew point..

In case your are interested for such an assistance please revert..
Rgrds
JPCHEMICAL

jpchemical@yahoo.com

 

[threeS]

My company has two vertical HRSG with internal insulation. We are going to carry out the water washing. According to the supplier's recommendation, we need to add alkali chemical into the washing water to neutralize the acidic deposit on the HRSG tube surface. The we need to use another chemical to rinse. pH value of the second chemical is slightly less than 7.

During washing, we will cover the HRSG interior with plastic sheets. However, the water leakage into the internal insulation is expected unavoidable.

Anyone has similar experience in water washing?

 

[andros45]

I AGREE WITH ERICWANG GENERALLY..
HOWEVER IN CASE OF HARD SULPHATE DEPOSITS, THE MENTIONED WASHING PROCEDURE IS NOT SUFFICIENT..
THERFORE IN CASE OF INTERESTING, KINDLY REVERT TO ME.
RGRDS
JOHN

 

[andros45]

I AGREE WITH ERICWANG GENERALLY..
HOWEVER IN CASE OF HARD SULPHATE DEPOSITS, THE MENTIONED WASHING PROCEDURE IS NOT SUFFICIENT..
THERFORE IN CASE OF INTERESTING, KINDLY REVERT TO ME.
RGRDS
JOHN

 

[threeS]

John

You have water washing experience? Can you share with us?

 

[andros45]

THANKS ERICWANG..
REVERTING AFTER A FEW DAYS
Rgrds
JOHN

 

[hrsgguru]

I would like to suggest that there may be a better alternative to water washing for this application. Several contractors are available that can do CO2 blasting - high pressure dry ice pellets. The ice pellets are very effective at removing the deposits and you are left with non-hazardous, powder-form ammonium bisulfate instead of barrels and barrels of disposal headaches.

With a staggered tube arrangement, the blast is done at angles and can typically reach 5 to 8 rows back into the tube bank, depending on the type of stagger. You'll have to work from both sides of the banks - hopefully your HRSG supplier included access lanes/doors between tube banks.

I don't know of any specific contractors in the Florida area - you could check the online Thomas Register for more info, though.

 

[davefitz]

Thnaks to all for input.

We will likely use CO2 pellet cleaning method. Also, we are going to depend on the following measures to reduce the effects of ammonium sulphate:

a) use a low conversion efficiency SCR catalyst- lower the SO2==>SO3 conversion efficiency to less than 1%

b) use low sulphur kerosene ( 0.01% S) today and convert over to 15 ppm S no 2 fuel oil in 2006 , when the ultra low sulphur oil becomes available.

c) the CTG's are 501FD2 machines, which are not fond of operating on fuel oil. We will upgrade the fuel oil fed system to be the lates "bidirectional" purge to eliminate the coking problem.

 

[joeh2o]

We are considering using the "dry ice blasting" method to clean the LP side of our HRSG. Does anyone have information on vendors that are capable of doing this. I am looking to get pricing information.