Look at the frame 9E FACT sheet from OEM ...actually look at the heat balance and eficiency for both mode, you will have an answer for this questionIn which Mode Frame 9e heavy duty Gas turbine fuel consumption is more for a given part load assuming other parameters constant? Is it simple cycle mode or Combine cycle mode?
Thank you for your response.Look at the frame 9E FACT sheet from OEM ...actually look at the heat balance and eficiency for both mode, you will have an answer for this question
Thanks for these clarifications..Thank you for your response.
In fact sheet, all data mentioned are for base load condition and in case of Combined cycle all data are about net effciency.
Since at base load IGV will be in fully opened condition so turbine efficiency will be same in both case (excluding HRSG). I am seeking information regarding fuel consumption at part load condition in simple cycle and combine cycle. In which case ther will be more fuel consumption.
Reason for seeking this information:
I am working in power plant at one of the Refinery of IOCl. Some times in our plant there is execess generation of Refinery Flue gas. This excess RFG is wasted in Flare. In order to utilize excess RFG, my idea is to operate gas turbine with IGV modulation off condition at certain load where HRSG temp can be maintained through extra FG consumption. So I just wanted to know, with IGV modulation off whether gas turbine will require less fuel or more for a given part load compare to IGV modulation on.
aksm238,
When operating at Part Load in Combined Cycle mode at a particular load the fuel consumption will be slightly higher than when the turbine is being operated at the same load in Simple Cycle mode. That’s because the air flow is being restricted by closing the IGVs to increase the exhaust temperature which reduces the mass flow through the gas turbine so to achieve the same load as when the IGVs are not being closed to increase exhaust temperature more fuel is required.
The above presumes the back pressure on the gas turbine exhaust is not significantly different when operating in either Combined- or Simple Cycle modes, and the inlet air temperature is the same and the inlet air filter differential pressure is the same and the IGVs and axial compressor are equally clean (or dirty). AND the fuels being burned have the same BTU content.
You need to factor in any difference in heating values between the two fuels. There are process plants that burn waste gas, often by mixing it with natural gas, but the analysis of fuel nozzle orifice sizing and fuel control valve sizing and required or maximum flow-rates and fuel pressures should be done by the OEM or a firm with similar combustion knowledge and capabilities. It’s not just as simple as connecting a pipe from the flare to the turbine and opening a valve.
And there’s also the maximum available quantity available for burning.
I have seen refineries that use an electric motor-driven compressor to raise the waste gas pressure and store it in suitable vessel until there is a sufficient quantity to burn for a period of time. But that requires energy (for the compressor), and a storage vessel for combustible gas, and a delivery/regulating system. All of which require money and engineering and space.
Doing this kind of analysis is not too difficult if a few presumptions are made, but the devil is in the details, as they say.
Hope this helps! Good on you, though for the initiative to be thinking of how to use waste gas and reduce emissions and be more efficient.
Thanks alot James for the information. I will surely check it out.Have a study on the FCP (fuel charged to Power) ...there is formula explained on OEM GER-3574G document , and other inetresting informations regarding fuel consumption ...
Depending on type of HRSG ( supplementary fired "like duct burner type"/unfired)...
Do not hesitate to share here your opinion..
James
I am so sorry for not able to put my facts clearly.aksm238,
Something about your query has been bothering me, and I might have discovered why.
You want to turn IGV Temp Control OFF to reduce fuel consumption which will reduce exhaust temperature for a given load, and then add RFG to raise the exhaust temperature back to what it was. Is that correct?
I don’t understand how the exhaust temperature will be controlled and limited while injecting RFG. And injecting RFG will also cause the load to increase. So if the idea is to maintain a constant load then the natural gas flow will have to be reduced even further.
Whereas when IGV Temp Control is turned ON and the load setpoint is constant the natural gas flow will have to increase (slightly) to maintain load. When IGV Temp Control is ON the exhaust temperature doesn’t increase much because the fuel flow increases, the exhaust temperature increases because the air flow through the turbine decreases—which decreases the mass flow through the machine which makes the power decrease but in order to maintain the same load as when IGV Temp Control is OFF the fuel flow has to increase.
If you want to burn RFG to reduce natural gas flow (and I’m presuming the unit burns natural gas—you’ve never said what the primary fuel is) you don’t have to do anything to IGV Temp Control—just start adding RFG and the turbine control system will do it’s thing, maintaining exhaust temperature and the load setpoint while reducing primary fuel flow. No extra steps would be required.
That sounds simple, and from a exhaust temperature and load control setpoint it is. But there’s a lot more to it. RFG probably also has some undesirable constituents which may not always be in the same proportions and which may cause problems with combustion and/or turbine hardware. This is yet another reason why the OEM or someone similar needs to review the fuel constituents and make sure it is safe to burn in the unit. And then devise a suitable method to introduce RFG to the combustion system.
But turning IGV Temperature Control ON or OFF isn’t the way to achieve what you seem to be aiming to do—reduce primary fuel flow by burning RFG while maintaining exhaust temperature and load. Just “supplement” the primary fuel flow with RFG and leave everything else alone to do its jobs.
That’s if I understand what you’re trying to do.
Best of luck!
Also, I will save some quantity of Naptha. That is the reason I was interested to quantify the differential fuel in part load with IGV Control On and OFF Mode.I am so sorry for not able to put my facts clearly.
We have 03 nos. of Frame 9e Gas turbine with HRSG.
Gas Turbine Capacity: 103 MW (Primary fuel Naptha and start up fuel Diesel
HRSG capacity : 220 TPH with supplymentry firing. (Available fuels for supplymentry firing are RFG, Diesel,NAPTHA)
Presently we operate GT with IGV Control On at partial load(mostly 70-80 MW)
"You want to turn IGV Temp Control OFF to reduce fuel consumption which will reduce exhaust temperature for a given load, and then add RFG to raise the exhaust temperature back to what it was. Is that correct? " It's partially correct.
I want to turn off IGV Temp Control to reduce fuel consumption in Gas turbine and to compensate reduced exhaust temperature additional RFG will be added in HRSG as supplymentry fuel. There by I can control exhaust temp and save the RFG from forced flaring.
Thank you.
I presumed you understood my query and as per your suggestion I went through the said documents.Thats why I mentionned/asked on my last post ,if there was supplementary firing see following elements below :
Have a study on the FCP (fuel charged to Power) ...there is formula explained on OEM GER-3574G document , and other inetresting informations regarding fuel consumption ...
Depending on type of HRSG ( supplementary fired "like duct burner type"/unfired)...
Do not hesitate to share here your opinion..
James
So now you jsut come and reply you got such HRSG....
My friend be more/better reactive otherwise i cannot participate more on this thread!
I am sure that you can understand my position.
James
For some strange reason, I didn't see that last paragraph when I read the askm238's response this morning. And, to the moderators, I don't know how to capture it because when I first read the thread I don't know something's missing (like the last paragraph, sometimes two). This isn't a one-off experience for me is what I'm trying to say. It happened more when I use an Android phone, and lately I've been switching web browsers on my desktops/laptops trying to find one browser I want to stick with (I've been trying out Brave, Edge, and my old fave Firefox, as well as Google Chrome--but I tend to think Google already knows too much about all of us!!!). ALL have LOTS of different configuration/choices for trying to limit pop-ups and tracking and that's all I'm really trying to do. But, choices and configurations even change with different versions of the same browser (I know--it's an "improvement"). Changing browsers shouldn't be a problem, but I have seen it both on Android phones and on Windows-based PCs.Okay Aksm238 Thanks for clarifying the situation
The original poster Aksm238, idea is to use RFG for HRSG duct burners/supplementary firing.... Not on GT combustion chamber....
Aksm238 got a original idea but the way it is presented is little bit chaotic.. But no problem I understood what he's intending to do..
Csa,For some strange reason, I didn't see that last paragraph when I read the askm238's response this morning. And, to the moderators, I don't know how to capture it because when I first read the thread I don't know something's missing (like the last paragraph, sometimes two). This isn't a one-off experience for me is what I'm trying to say. It happened more when I use an Android phone, and lately I've been switching web browsers on my desktops/laptops trying to find one browser I want to stick with (I've been trying out Brave, Edge, and my old fave Firefox, as well as Google Chrome--but I tend to think Google already knows too much about all of us!!!). ALL have LOTS of different configuration/choices for trying to limit pop-ups and tracking and that's all I'm really trying to do. But, choices and configurations even change with different versions of the same browser (I know--it's an "improvement"). Changing browsers shouldn't be a problem, but I have seen it both on Android phones and on Windows-based PCs.
MOST HRSG auxiliary firing systems I have seen would not allow firing unless the GT was at Base Load--not all, but most. I think it has something to do with the available oxygen, which is high to begin with, but I'm told with some burner designs it needs to be as high as possible.
ControlsGuy25, working with/for GE Belfort as much as you seem to have has apparently allowed you to be better at deducing and understanding whacko ideas and schemes. I understand how askm238's scheme might work now, but I think it's iffy at best. I wonder if the auxiliary burners are really capable of burning RFG at this time, and if so, why hasn't his scheme been tried? He could monitor GT fuel flow with IGV Temp Control ON and then OFF (allow time for internal GT temps to stabilize!) to see how much fuel flow changes. That could even be done at any time. Real world data is so much better than computer-generated graphs and curves.
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