GTG-HRSG Startup 1

[norzul]

Hi,

In 4 to 6 months time we are planning to commission 4 GTGs (F5 size) and 4 HRSGs (95 t/h with supplementary firing). Our gas turbine is closed coupled with the HRSG without the bypass stack i.e. if GTG down, HRSG will also down, vice versa.

I was informed that due to not having a bypass stack, it will take longer time for the GTG to reach its full rated capacity. For cold standby it will take 7 hours. For hot standby it will take 3 hours. The reason is to reduce the thermal shock on the HRSG tube. Is that really the case? I just feel this is too long and my understanding is that GTG is always a fast response machine.

Thanks

norzul

 

[toothless]

We have 3 Frame 6 GT's in the same configuration as you. For a cold start-up, we bring the GT up to full-speed/no-load and sit there for 30-45 minutes. Then we synch the generator and raise the load about 5 MW every 5-10 minutes. I don't see why your start-up time would be as long as you've stated. Contact the HRSG manufacturer regarding this since its the HRSG that is the limiting factor.

 

[rmw]

You asked a question in another thread about a bypass stack. The value of this is that your GTG can be brought up to full load with the exhaust flow diverted to the bypass stack. Then the exhaust can be diverted little by little to the HRSG until it is up to temperature.

If you have the capital to spend and the need for power to justify it, you ought to do it. There are companies who build diverter dampers specifically for this service, and I have seen them used on Frame 5's quite a lot.

Try

http://www.effox.com

for a starter. I think you will find some examples of what you are looking for on their site.

rmw