Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
(OP)
I am currently loking at increasing the ramp rate of a Gas Turbine on a CCGT system, and have a temperature gradient limit.
Can people please just give me what sort of concerns / advice / look outs / issues I should be on the look for as I am not experienced at this.
the only concern I can think of is:
- the HRSG units associated to it
- temperature cycling and low cycle corroison fatigue
any comment will be greatly appreciated
Can people please just give me what sort of concerns / advice / look outs / issues I should be on the look for as I am not experienced at this.
the only concern I can think of is:
- the HRSG units associated to it
- temperature cycling and low cycle corroison fatigue
any comment will be greatly appreciated





RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
Further improvements are available in the design phase, by minimizing drum wall thickness and SH/RH header thickness, full penetration welds at tube stube to header welds ( superheater and reheater), and properly desing spray atemporators ( wide range spray nozzles + long straight run of downstream piping to allow 0.15 sec steam residence time before downstream bend or header.
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
Best of luck!
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
Basically you can increase the speed ramp rate but it puts additional stress on the GT hot gas parts. The OEM should be consulted and they will give the maximum allowed speed ramp, with probably an addition to the operating hours which, in turn, will shorten the time between inspection and overhauls. The HRSG may be an issue also, but this may be warmed in advance, depending on your configuration.
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
Please do drop more information or knowledge you have on this subject they will all be taken in and appreciated.
David O.
Mechanical Engineer
Graduate as of: 2007
Oil, Gas & Power
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
That is to name a few but it covers most bases. Now you want to change it. I think you should get an opinion from each OEM with parts affected by the ramp rate change and then make up your mind if they are all on board and if you have met all their requirements.
rmw
RE: Changing/Increasing GT Ramp Rate for warm start of a CCGT Powerstation
For a large frame gas turbine in simple cycle mode, a cold start to full load is feasible within about 15-20 minutes. So the CTG limits are more or less defined by the simple cycle ramp rate lmitations.
For a drum type HRSG with a 4" thick HP steam drum and 1.5" thk P91 SH outlet header and no concerns regarding downstream equipment ramp rates, full HRSG load could theoretically be reached within 1 hr.
When the CTg's and HRSG's are mated to a 200 MWE x 2000 psig STG without a final attemporator, one has a typical startup time from cold to 50% MCR load in about 4 hrs, on a very good day.Most environmental permits for these units are also predicated on achieving this load within 4 hrs.
This 4 hr plant cold startup period could theoretically be reduced to about 2 hr if a final attemporator were provided, and HRSG thermal stress limits were monitored by a BSA boiler stress analyzer. STG prewarming system and aux boiler would help also.