16 replies to this topic

[ramsingh_mech]

Dear Professionals,

 

What is the best configuration for GT Exhaust ?

 

I have seen many GTs Exhaust connections are vertical and then its connected to HRSG with one more bend  connection. if this exhaust duct connection is Horizantal (Directly connect to HRSG with Expansion bellow with out bend routing) there will be less press drop and maintains good energy level in the gas.

 

Any one experience the difference , pls explain.

 

Regards

RAM

 

 

 

 

 

[thorium90]

Those GT's I have seen in power plants are all horizontal. Perhaps you can share where you saw the vertical GT?

It seems odd to have the GT vertical, then have the HRSG at an elevation higher than the GT and then all the steam drums on top of the HRSG... That would all be pretty tall..... And all that weight sitting on one set of bearings, and the amount of support for the GT. It would be better for the GT to be horizontal and the gas to exit the GT horizontally rather than towards the sky before going to the HRSG

 

Unless of course, you are actually referring to horizontal and vertical HRSG and not the orientation of the GT and the direction of the GT exhaust?

Edited by thorium90, 21 March 2013 - 11:07 AM.

[ramsingh_mech]

Thorium,

I am speaking about GT orientation only , for better understanding, i am attaching a sketch.

SKETCH: the offerd arrangement by manufacture is vertical exhaust and the Red one explians my doubt.

 

Pls refer any good link or book on the GT Exhaust subject.

 

Thanks..

 

Regards

RAM

 

Attached Files

•  GT-Exhaust.pdf   139.09KB   24 downloads

[thorium90]

Ram, I think the purpose of your gas turbine and HRSG is not clear to you, thats why you have this question as to which is better. Just to confirm, could you clarify the purpose of your GT and HRSG? Could you label your diagram more clearly too, its very bare.

[Art Montemayor]

I don’t know enough about the experience level of either of the two participants in this thread up to now, but some working, field knowledge is essential to address the basic query:  “What is the best configuration for GT Exhaust?”

 

To me the answer is very simple and composed of two components:

• What are the required needs of the end-user and owner as well as the available space/volume in the field;
• What is the recommended configuration of the designer / fabricator;

The “best” configuration from an engineering and practical point of view is the result agreed to by the engineering contractor/designer and the owner.  The engineering contractor/designer often has the responsibility for the ultimate performance of the installed gas turbine - and so, often has the last or stronger legal word in the matter – making that the “best” configuration.  The decision often has a lot of more factors involved than just “likes”, opinions, thermodynamics, and beliefs.  It has a LOT to do with legal liability and profit margins.

[thorium90]

The reason I ask is that if the GT is used for power generation, it would typically be horizontal so that the generator would be on the same shaft to turn the generator to produce electricity (otherwise the generator would be pointing to the sky and be very high up!) . The GT can also be used to drive compressors instead of generators and could therefore be vertical and not necessarily horizontal (the compressor could be below it). The HRSG downstream is just a consequence because the GT exhaust is still hot and it is economical to use the heat to produce steam.

 

Whether it goes to the HRSG horizontally or vertically therefore depends on the purpose of the GT. It does not depend on pressure drop since the exhaust is huge. Just look at aircraft turbine engines and the size of their exhaust and imagine a large ducting connecting the exhaust to a huge chamber with lots of steam boiler tubes. The duct is so huge, the pressure drop is pretty negligible whether it goes straight or upwards to the HRSG.

Edited by thorium90, 23 March 2013 - 09:44 PM.

[ramsingh_mech]

Thorium,

 

GT is used for power generation as well as steam generation also(where shaft connects to the genrator will produce power & exhaust gases routed to HRSG to produce steam) . how you could imagine that , GT itself will arranged vertically and generator pointing to the sky????? I asked question about GT Exhust duct configuration ,not complete GT Configuration., GT & Generator will be coupled to same horizantal shaft  as shown in my sketch ,

 

Art ,

 

I request you to go through my sketch and my question , i think ,the solution for my question definitely economical and meet comfortable requirements for the owners & contractors.

 

 In my three years experience , i have handled a 3 projects ,Steam power plant ,Gas turbine power plant&  Solar Powe plant.and did spent 1 year in the field services. that is the reason i have raised a doubt .....Definitely i need help from your professionals to increase my learnig and knowledge levels.

 

I am attaching a detailed revised sketch , My question is explained in green markings.

 

Regards

RAM.

 

 

 

Attached Files

•  GT-Exhaust.pdf   215.68KB   17 downloads

[thorium90]

It is not labelled in your drawing the axis of the GT. I dont see the green, and the red words are too blurry.
The gas flow of the gt is axially, therefore if the gt shaft is horizontal to the ground the generator which will be on the same shaft will be horizontal and therefore the gas exiting from the gt will also be on the same axis as the gt shaft. So your question about the orientation of the gt exhaust where it should point is moot since the gt exhaust will always be on the same axis as the gt. Thats why i asked in my previous post if you are actually referring to the hrsg and not the gt. Theres no need to decide the direction of the gt exhaust since it is definitely in the same direction as the gt!!!
Due to the torque of the gt, the generator will always be on the same shaft, therefore if the gt is vertical, the generator will obviously be vertical too and it will be on the other side since one side is the gt exhaust and o iit will have to be pointing to the sky!
Also, the gt does not produce steam contrary to what you think. Its the hot exhaust gases from the gt that goes to the hrsg that produces the steam. Furthermore what do you mean by good energy level in the gas? Energy level is very vague, do clarify.

Edited by thorium90, 28 March 2013 - 03:48 AM.

[ramsingh_mech]

Dear friend,

 

Its difficult to understand sketch without having experience with G.T...i understand that you do not have experience with gas turbines.. How could you say that (the gt does not produce steam contrary to what you think).. I am working with this project , the turbine is producing 25 MW power as well as 560 deg C flue gas to produce steam in HRSG...However thanks for your response i will get the solution soon.

 

Regards

RAM.

[thorium90]

Ram, i work with gt's and st's everyday and i can tell you that a gt does not produce steam. A steam boiler produces steam. It is the hot gas from the gt that is used in the hrsg to make the steam. 25MW is a very small power plant. Also, contrary to what you think, the gt doesnt generate power, the generator does.
I already gave you the correct answer in my post above. It is up to you to put down your pride and seek to understand what i am telling you.
Theres alot more i can tell you about power plant equipment but its evident you already have your own opinion.

Edited by thorium90, 28 March 2013 - 04:34 AM.

[ramsingh_mech]

Thorium,

 

GT does not produce steam(everybody knows that) , why you are telling me that .iam repeatedlly telling that , flue gases are routing to HRSG to produce steam. my question is about the connected duct between GT and HRSG.I am trying to make you understand ,my intention is not to hurt you thorium.Better leave this hot discusstion.

 

Regards

RAM.

[thorium90]

And i've already told you why the orientation of the duct connection is a fixed parameter and has nothing to do with energy loss.
There, i think i have said enough.

 

Ahh, it would appear my mobile cant see the green boxes and any of the other boxes you put in. I see your point about the bend. I assume the bend is up and over the generator? Your proposal is to have the ducting at the side, as per my rough drawing? It would then appear to be some kind of site constraints. Is there anything on the side of the GT? If there are already equipment built there and the back of the generator is empty land, then evidently one has to rout the exhaust up and over the generator unit.

 

Although, conventionally, the side with the generator is at the air filter side, so the gt exhaust is straight to the hrsg.

Attached Files

•  ram gt.jpg   27.32KB   1 downloads

Edited by thorium90, 28 March 2013 - 07:05 AM.

[ramsingh_mech]

Thorium,

 

At last , you got my point. please try to see in laptop or computer, i have added some lines and Notes on the sheet. There is no site constrains. anyhow i have taken up this point with my GM -Engineering , He understand my point. we sent a mail to manufacturer the same. ....will see further.

 

RAM.

[thorium90]

Im curious, is the manufacturer of your gt aware of all this? As in that there will be a HRSG connected to their GT? Perhaps they thought all they were designing was an open cycle plant, although that would be pretty silly. They should be able to understand this very well. It is pretty unconventional to have the generator on the side of the exhaust, care to explain why this is so? There is a reason why in diagrams of a CCPP, the generator is always shown to be at the compressor side.

 

I have a nice book, "Combined - Cycle Gas & Steam Turbine Power Plants" by Rolf Kehlhofer, its a good read. It will answer alot of your questions on CCPP's

 

http://www.zeroco2.n...sskraftverk.jpg

 

http://ars.els-cdn.c...4004633-gr1.gif

Attached Files

•  CCPP.jpg   106.55KB   8 downloads

Edited by thorium90, 28 March 2013 - 10:54 AM.

[ramsingh_mech]

Dear Thorium,

 

I am very sorry, would have come in detail. ,it is not CCPP. yes its an open cycle for CPP&UP (Captive power plant & utility plant) for refinery , there are 4 no of Gas turbines (4 X 25 MW) which are connected to generators , and waste heat is routed to 4 no of HRSGs(each 80TPH) to produce steam which is used for refinery utilities not for run the steam turbine.

 

Thanks for sharing nice books.

 

Regards 

RAM.

[thorium90]

Ahh, I had a hunch on that. 25MW is too small to be a commercial power plant. Are all 4 GT identical, as in having the same configuration and layout?

 

Are all your threads related? The 58barg and 12barg steam, the cement plant, the PH gas, the feasibility stage of the plant design?

Edited by thorium90, 28 March 2013 - 11:05 AM.

[ramsingh_mech]

No , no that project is different , these steam pressures related to refinery project only. Generally in Cement plants there is no any steam requirement.

 

Regards 

RAM.