hello for every body:

in our plant there are two gas turbine 100 MW GE frame 9 working as combine cycle. some time it observed yellow smoke from chimney of one of the unit where as there is nothing in other unit. all the gas source is the same for the same units. any one have explanation for that phenomena.

thanks

 

Does either unit have DLN (Dry Low NOx) combustors?

Does either unit have Water- or Steam Injection for NOx reduction?

 

Please every shutdown we have white smoke only one unit in the plant and other are normal no smoking during shutdown.

 

Sent,

When did this problem start?

What have you done to try to resolve the problem?

Have you used the manual selector valve at the Liquid Fuel Flow divider to monitor the fuel pressures of each combustor/nozzle during operation and during shutdown?

Your shutdown fuel "curve" may need adjusting, or there may be a problem with the atomizing air supply during shutdown, or the fuel nozzles may not be clean, or the fuel may need to be shut off sooner than it is being shut off during shutdown.

There are too many variables and you haven't provided nearly enough information to be any more specific.

 

look at your gas control valve positions and emission reading, you do not say what set up you have i.e. diffusion burners or premix, pilot control for flame stability ?

 

This problem present when the Gas Turbine shutdown. I doubt with atomizing air system. The manual valve of fuel flow divider can not check because Turbine Trip with Accessory or Turbine Compartment Door Open.

 

We understand the smoking is coming when the turbine is being shutdown (STOP active).

If you can't enter the Accessory Compartment to check the fuel pressures without tripping the turbine you're going to have some difficulty troubleshooting the problem.

You didn't answer the question of when this problem began.

Smoking (white smoke) during shutdown is usually the result of loss of flame in one or more combustors, so you should be able to monitor exhaust temperature spreads and if they increase shortly before the smoking is visible then flame is indeed being lost in one more combustors during shutdown. (The unburned fuel is being heated as it mixes with hot combustion gases and vaporizes (turns to white vapor, "smoke").

Unburned fuel can also accumulate in the compressor discharge casing and the exhaust plenum, and should be visible draining out of the "False Start" drains. So, this would be still another indication of loss of flame.

What causes the loss of flame in one or more combustors? Inadequate atomizing air flow to one or more combustors. Liquid fuel nozzle passages out of tolerance. Incorrectly adjusted liquid fuel shutdown reference. Problems with liquid fuel check valves (not maintaining the desired "cracking" pressure). Problems with atomizing air check valves (leaking).

If the Atomizing Air check valves are leaking, you would see flow coming out of the Tell-tale Leak-off drain. See the Piping Schematic drawings (P&IDs) and Piping Arrangement drawings to locate the Tell-tale Leak-off.

But, if you could check the individual fuel nozzle pressures using the selector valve (by temporarily forcing the logic if the safety procedures at your site permit this for troubleshooting purposes), then you could more easily pinpoint potential problems with individual check valves or fuel nozzles. If not, your task will be more difficult.

 

I have made a serious ass-umption here: That the smoking is occurring during the fired shutdown from FSNL while the unit is operating on liquid fuel.

If the unit is operating on gas fuel, then something is seriously amiss as white smoke rarely comes from a gas turbine exhaust while operating on gas fuel (loaded, unloaded, starting or shutting down).

I think it was a safe ass-umption since Sent did say access to the liquid fuel selector valve would result in a unit trip (which sounds very unusual by itself, but some areas of the world are becoming extremely, and overly, safety conscious), but Sent has never told us what fuel is being burned or exactly when the smoking occurs, except that it occurs "during shutdown".

So, apologies if the ass-umption was incorrect.

 

You can go for pre mix stage and you will get the NOx < 20 ppm and this is can be done if you have primary and secondary firing in other hand may the Natural Gas having H2S

 

HELLO CSA

i face nearly the same problem,during shutdown at TNH=80% THE UNIT TRIP(LOS OF FLAME).

this unit (gt f6b mk5)during start up at firing the alarm (failure to ignite) come.

we checked that:
two spark plug ok
atomizing air ok
pressure at selector nearly 8bar
we pas this alarm (failure to ignite) by change over from gas to liquid at loud 15mw

THE QUESTION:
IS THERE A RELATION BETWEEN TWO ALARM:
(LOSS OF FLAME) DURING SHUTDOWN AND (FAILURE TO IGNITE) DURING START UP.

 

>i face nearly the same problem,during
>shutdown at TNH=80% THE UNIT TRIP(LOSS OF
>FLAME).

The same problem as what? Yellow smoke?

>THE QUESTION:
>IS THERE A RELATION BETWEEN TWO ALARM:
>(LOSS OF FLAME) DURING SHUTDOWN AND
>(FAILURE TO IGNITE) DURING START UP.

It seems, Kahlid, you are trying to say that when you try to start on liquid fuel that you have a failure to ignite and the by starting on gas fuel that you have more luck and are able to get up to load and then transfer from gas- to liquid fuel to run on liquid fuel.

Then, you seem to be saying that during shutdown you trip on loss of flame at about 80% speed.

You didn't say when these problems started; and no, I don't think they're related except to say that it would seem that some "tuning" of start-up and shutdown Control Constants needs to be done.

I'm very surprised about the tripping on loss of flame during shutdown, unless if you mean you get the alarm, "CHAMBER FLAMED OUT DURING SHUTDOWN" and not "LOSS OF FLAME TRIP". These two alarms are NOT the same, and it's pretty hard to get a loss of flame trip during shutdown; the more common alarm is the "CHAMBER FLAMED OUT DURING SHUTDOWN."

So, I still don't know how any of this is related to the original posting of this thread, or even any of the subsequent postings.

And, I don't really know if I've interpreted what you were trying to say properly. If I have, I would also say it would be extremely difficult to provide enough help to solve your problems via this forum.

Please have someone knowledgeable in GE-design heavy duty gas turbine operation come to site and review the problems, perform an analysis, make some recommendations, and do some tuning to resolve the problems.

Best of luck with your problems.