Gas turbine's stabilty
Gas turbine's stabilty
(OP)
Hello, Everyone.
We want to build a big methanol production plant based coal.
We want to use an integrated coal gasification combined cycles plant to provide steam and power for this plant,this idea of coproduction of power and chemicals.
But somebody said a gas turbine have to stop for check the combustor and the blades of turbine every month. This will
disturb the stable production of chemicals.
But i find the such concept is very popular now. And ISAB plant in Italy use IGCC to provide steam and power for chemical plant, this plant can output 522MW power and run very well.
So I just want to ask several questions:
1)the longest time of continuous run of gas turbine;
2)how to avoid the disturb to the chemical plant;
3)If the IGCC have to stop very frequently, the concept of coproduction may be not feasible. But this concept of polygeneration is very popular, such as DOE's EECP, some chemical plants. What are their solutions?
4)we extract some high pressure air to the air separation unit for supplying oxygen to the gasifier, if the gas turbine shut down, the gasififer must be down. Then if we want to start the plant, it will last a long time. Can anyone do me a favor that how a igcc plant solve this problem?
We want to build a big methanol production plant based coal.
We want to use an integrated coal gasification combined cycles plant to provide steam and power for this plant,this idea of coproduction of power and chemicals.
But somebody said a gas turbine have to stop for check the combustor and the blades of turbine every month. This will
disturb the stable production of chemicals.
But i find the such concept is very popular now. And ISAB plant in Italy use IGCC to provide steam and power for chemical plant, this plant can output 522MW power and run very well.
So I just want to ask several questions:
1)the longest time of continuous run of gas turbine;
2)how to avoid the disturb to the chemical plant;
3)If the IGCC have to stop very frequently, the concept of coproduction may be not feasible. But this concept of polygeneration is very popular, such as DOE's EECP, some chemical plants. What are their solutions?
4)we extract some high pressure air to the air separation unit for supplying oxygen to the gasifier, if the gas turbine shut down, the gasififer must be down. Then if we want to start the plant, it will last a long time. Can anyone do me a favor that how a igcc plant solve this problem?





RE: Gas turbine's stabilty
Of course, every machine must have maintenance, but turbines are among the least demanding in that respect with proper planning. If you cannot afford a redundant turbine for zero outages, SOLAR has been known to stock spares with a contracted minimum downtime replacement.
So essentially, it is a concern that should be addressed, but it is also a common guarantee of turbine power generation sales and service.
RE: Gas turbine's stabilty
Major inspections requiring longer outages occur every 6 years or so.
RE: Gas turbine's stabilty
If the cryo plant and gasifier has a turndown abililty , to perhaps 60% load, then supplying 2 x 60% gas turbines may be an answer.
RE: Gas turbine's stabilty
Talking about IGCC (integrated gasification combine cycle), just remember that we did feasibility study several months ago. The objective of the study was to find out whether should we proceed with the IGCC+Cogen or just proceed with the cogen. The result proved that it is not feasibile to proceed with the IGCC at this point of time. Yu can refer to my new technical blog to see the process flow of IGCC and its relationship with Cogen.
http://technical2005.blogspot.com/
Anyway regarding the gas turbine downtime, based on my knowledge there are 4 kinds of inspection required:
1) Boroscope inspection
2) Combustion inspection
3) Hot gas path inspection (HGPI)
4) Major inspection
The frequency/interval of inspections may vary from one machine to another. It also varies according to the manufacturer. Just to share our experience, we evaluated 3 manufacturers for the 25MW gas turbine range.
1) GE/NP - Frame5 (PG 5371PA)
a) Boroscope : annually (1day)
b) Combustion : 12,000 hrs (5days)
c) HGPI : 24,000 hrs (13days)
d) Major : 48,000 hrs (36days)
2) Hitachi - H25
a) Boroscope/Combustion : 16,000 hrs (5days)
b) HGPI : 32,000 hrs (18days)
c) Major : 64,000 hrs (27days)
3) Simens - GT10B
a) Boroscope/Combustion : 10,000 hrs (3days)
b) HGPI : 20,000 hrs (10days)
c) Major : 40,000 hrs (21days)
This is based on the proposal and for 25MW machine, however the more accurate info need to be sourced from the supplier himself.
Thanks
norzul
RE: Gas turbine's stabilty
Scheduled downtime is per turbine manufacturer warrentee. If power generation is electrity, multiple package type units are required with extra capacity, or purchased backup utility power. Steam requirements can be supplemented by direct firing the steam generation unit. There is alot of experience readily available to assist in these evaluations.
best wishes,
sshep
RE: Gas turbine's stabilty
The shortest time interval for maintenance of any of the three listed is 10,000 hours. That still means constant uptime, without interruption of over one year! (24 x 365 = 8760 hours) Even then, the maintenance time required appears proportional to the maintenance period. For example, the shortest interval - 10K hours - requires only a single day of downtime. One requires 5 days downtime, but the interval is 16,000 hours, effectively two years' worth of 24/7 uptime.
Those are almost magical periods of constant uptime for any machine, period.
Sshep has echoed my original suggestion, too - the uptime is negotiable and is part of the turbine warranty. Also, as he repeats, "There is a lot of experience readily available to assist in these evaluations." Good comments from both.
RE: Gas turbine's stabilty
However, based on my discussion with NP, for frame 5 GT, the offline interval could be 4-6 months. The whole activities will take about 1 day (from stop to start).
The online washing interval could be each month but yu don't have to shutdown the turbine.
RE: Gas turbine's stabilty
Most gasifier reactors are thick refractory lines vessels, over 1.5 ft thick ,and to avoid excessive thermal stresses could need a 2 day warmup period to reach full operating temperature. The exception may be the Shell design , which uses a steam cooled or water cooled vessel with a thinner reractory inner liner.
I understand that typical max operating periods for the refractory lined vessels is 9 months- they would require an inspection to determine the degree of high temp corrosive damage to the refractory after 9 mos. So a major outage that would allow inspection of the gasifiers would be scheduled at least once per 9 mos.
If the committment for product gases is for 365 days per year without scheduled outages, or if one cannot tolerate a forced outage, it would seem practical to design the plant as 2 x 50% or 2 x 60% trains for those pieces of equipment that requrie maintainence outages or have low availabilyt, sych as gasifier trains, hot filters, gas turbines, etc.
Another annoying issue associated with the IGCC's need to operate 24/7 is that there must be a corresponding firm consumer of the product gas on a 24/7 basis. This works if the consumer is a chemical plant, but a power generating gas turbine is usually schedueld to shutdown at nightime to allow the base loaded coal fired plants and nuclear plants to maximize their output during nightime electric demand minimas.
RE: Gas turbine's stabilty
Thanks very much.
RE: Gas turbine's stabilty
The frequent inspection interval is probably due to the use of the syn-gas (CO, H2, +crap, etc). Turbines can burn just about anything, as long as it is clean. If you ONLY ran the turbine on the methanol, you'd have a much better shot at improving your maintenance intervals than if the unit is switched back and forth between different fuels.