Any gas turbine experts out there ?

[Jim_gsxr1000]

At work we have 6 gas turbines 4 Sulzer type 1's a TB500 and a Tornado, they all run from our fuel gas suply, however if that fails we can run out TB500 and Tornado, on Deisel however to do this the pilot burners use LPG (propane) to get going before the main fuel pump starts to inject Deisel around 5.6 BAR.

The problem is in sunny scotland is that the propane bottle (47KG) struggles to produce more than 4 BAR of dynamic pressure at abbiant temperature without bottle heaters, so this either does 1 of 2 things when the main Deisel pump comes on it will blow out the pilot burners or the telemitry wont let the machine get through it start sequance,

My question is why do they use propane for start up if it can only provide 4 bar dynamic take off pressure in out climate, would it not make sense to used compressed methane which will suply the higher pressure (the volume required isnt massive its more about the constant pressure or reduce the the Desil injection pressure and use larger injectors to compensate for the reduction in pressure ?

Any thoughts would be appreciated

 

[AndyStobbs]

I'm no turbine fitter, and can't even comment on the gas side of things - apart from agreeing with what you say regards pressure.
With the injectors though, do they have what you would call a 'spray pattern' or is it literally a valve on a tube?
If they have a spray pattern then that could be a factor in them requiring the pressure that they do. Perhaps at lower pressures the atomization required could not be acheived.

 

[Jim_gsxr1000]

im not entirely sure, we never strip the injectors or pilot burners, siemens normaly overhall them on an exchange basis

 

[AndyStobbs]

When you say LPG, is the propane being drawn off as liquid or gas? I assume gas given you say 47kg bottle not 46kg as is the case with the dip tube cylinders.

Is the draw off rate low enough to not casue much cooling of the bottle and so a pressure drop that way?

 

[Jim_gsxr1000]

The LPG is being drawen off as a gas, so as soon as you take gas off the pressure droppes, not a problem in Saudi or Egypt, but here in sunny scotland its that cold we need bottle heaters

 

[FranV8]

The problem with methane is storage, to get it as a liquid it needs to be at -160 degrees C.

Can't the propane cylinders be kept in a temperature controlled room/enclosure?

 

[Jim_gsxr1000]

yeh, volume isnt realy a problem, we dont need that much gas its the constant pressure, you get W size BOC bottles charged to 230 bar with methane, we have one but as soon as you start drawing gas off the temp in the bottle drops, youll get 1 attempt to start when the bottle is up to temp, if it doent, takes a couple of hours to get the temp back up

 

[FranV8]

Well, you could look at how many starts it normally takes and have more than one cylinder ready to go (1 per start), or if, say, it took half an hour to go through the start sequence then 5 bottles mean you could go at it constantly. (1 in use, other 4 heating)

Basically though, the units and burners are probably set up and designed for a certain gas type and certain pressure, changing this is probably a job for the turbine supplier, so I guess you'll be needing to look at how you can provide what it wants with a solution on the supply side.

As you can tell, I'm not a gas turbine engineer...

 

[Big Pete]

Methane costs a fortune compared to propane, and its harder to get a reliable supply, IIRC ours comes in from the Netherlands now as there isn't a UK plant that makes it any more. The handling equipment for propane is cheaper as well, even including heaters. Also, I think that methane scores higher in the fuel storage (COMAR?) regs than propane, but this might not be an issue for you.

 

[normspanners]

I am with Andy on this if you run a lpg vehicle you draw off liquid from the cyl through a dip tube if you dont you end up with the same problem as your experiencing the gas cannot be generated in the cyl fast enough, it then goes to a vaporisor which then changes it to gas this allows high discharge from the cyl. But will require the vaporisor being heated to save it freezing
the other idea might to be make up a manifold and run 2 or more cyls to keep up the discharge rate

 

[Jim_gsxr1000]

It just seems such a stupid set up, in this country, its not a problem in the middle east, as there is plenty of sunshine to warm the bottles, BOC do compressed methane, in CAL bottles and also in W size bottles, we have them on site for other purposes so storage shouldent be a problem

 

[Exuptoy]

Jim, I am working on an FPSO off Aberdeen and we have 2 typhoon gas turbines which we run from what we get out of the ground but as we are currently not producing we run them on diesel as well as starting.
Why do yours have to be started on gas pilot, can they not be converted or configured to start on diesel? The biggest issue we have is that due to the fact we don't put much load on ours they run very dirty due to poor burn and if they shut down then if they don't restart them immediately when warm then we have to change out the burners as they will be severely sooted up. The only stipulation for us really is that the gaps are correctly set at 3mm for correct atomisation.

I'm not responsible for maintaining these though as we have turbine techs for that. (Former Siemens guys lol)

 

[captain-destructo]

you could try one or several of these

The T piece go's into the first bottle the reg go's on one side the hose go's on the other side and connects another bottle

Hey presto you have just doubled the surface area of the liquid gas so it takes longer to freeze up as it evaporates




currently on ebay item no 110807730920

WILL CONNECT TWO CALOR PROPANE CYLINDERS TOGETHER TO REDUCE FROSTING OF CYLINDERS

USED ON TWO CYLINDERS GAS CHANGEOVER SYSTEMS TO UPGRADE TO 3 OR 4 CYLINDERS

 

[Wedg1e]

Why do yours have to be started on gas pilot, can they not be converted or configured to start on diesel?

How about kerosene?

 

[Exuptoy]

The only problem out with us is any change from original spec means red lined drawings and change requests to the beach. It'd take years to get stuff finally signed off and modified!

 

[Jim_gsxr1000]

Were the same the fuel gas comes from our Frac plant, the deisel is just as a back up, our machines wont satrt on desiel without the LPG pilots, its also Siemens that maintain ours

 

[normspanners]

how about a lpg transfer pump to increase the pressure, they have to be higher than cyl pressure to transfer to the tank ? you could regulate the pressure to 4-5 bar and that would keep the pressure up but you would still need a vapouriser.

 

[Jim_gsxr1000]

The pilots use gas rather than liquid