Steam Turbine Fouling 1

[Falcon03]

The frequency of our FCCU Wet Gas Compressor turbine fouling has increased sharply this year. We have conducted an online cleaning three times this year compared to two times last year. Please note that in Year 2001 we only cleaned it ONE time.

Does any body has/ had experience such a problem and what the action that has been taken to avoid such problem. It is really hearting us by reducing feed and severity for two shifts which then will impact on our profitability.

I appreciate your assistance and help in this matter. Tks

 

[TD2K]

What's causing the fouling, if you know?

 

[tkdhwjd]

My Hypothesis...

Online cleaning should be fairly effective if steam temperature was lowered controllably. You surely do not want to condense the steam since it will wreck the turbine, but at certain temperature, silicate and other minerals should dissolve and wash away. This is very delicate procedure and most compressor manufacturers do not recommend it.

Also, I believe there is a specially designed nozzle that atomizes water when injecting into turbine. I heard this works well.

 

[Falcon03]

Td2k,

Based on the nalysis we have it seems to me it is related to steam quality !!!

We have consulted Nalco to do steam quality study and try to foucus in the WGCT.

 

[TD2K]

Based on the nalysis we have it seems to me it is related to steam quality !!!

What does this mean? Do you have any hard data to post here? Have you looked at the control levels of impurities back in your steam generation units versus what they should be? There's no details here for anyone to really help you out.

It's like saying 'I have a problem with my computer' and expecting a solution.

 

[25362]

Try to locate the Hydrocarbon Processing issue of December 1972, just 31 years ago. It carries an article by John S. Sohre titled Causes and cures for silica deposits in steam turbines. It may be of help.

 

[abdullah]

I wonder how could you have scales if your steam quality is ok!
I recommend you to do the following tests: -
1- Check conductivity and Total dissolve salts (TDS) and (TSS) in your steam condensate.
2- Cl- content.
3- Basic cations

If got any of those high (above 10 ppm) then you should treat the DM water feed to the boilers. There shouldn’t be any treating at the turbine side.

 

[Falcon03]

Thank you all for your feed back,

Ok let me give you some history, sorry if I wasn't so clear well.

As I mentioned above that three years ago the Turbine post pressure (presure indication located on the third turbine stage) start increasing gradually which means that there is some deposit is taking place on the turbine blades especially the last three. Keep in mid our Turbine consists of five stages..

Therefore, we tried an on line cleaning of the turbine blades by using condensate water injected in the superheated high pressure steam ( 42 barg and 400 °C) and we monitor the condensate quality on the exhaust steam (LP steam) for conductivity. The whole washing process is about 12 hours. During the process we slightly reduce Feed rate and severity.

Compressor manufactures DO not recommend the washing at ALL but we did it !!!

How we know that we have a good wash? is by measuring the condensate conductivity. at the beginning of the wash the conductivity will shoot up as high as 3000 to as low as 10 mic.

One time we washed the turbine one month later after the first wash, which raised a flange what could be the possible reasons .. is it steam quality issue ..??

Now anybody has such experience on this issue ??? I hope it is clear now. Thanks