Gas turbine's stability

[gaillee]

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?

 

[GTstartup]

Typical time between minor inspections is about 4000 equivalent operating hours which is a combination of running time, starts, trips etc. I know of some plants that run for several months between shutdowns. Consult your GT supplier for details. Minor inspections can be done in 2-3 days including cool down time. Major inspections can take up to 30 days. You can't avoid disturbances due to the down time during inspection unless you can provide power from somewhere else (other GT or utility supply for example)

Best solution is to contact GE, Westinghouse, Alstom etc.

 

[EEJaime]

Time between maintenance intervals vary from manufacturer to manufacturer and between differing technologies. One solution we have used on a 12MW co-generation system we have operating is to utilize design schemes with multiple generation units running in parallel. In our case we have an N+1 design wherein we have one unit more than necessary to meet the demand for our 100% output. Our preliminary cost analyses concluded that the added expense of installing this unit was compensated for by our ability to maintain the full output capability of the plant at all times. Rotating scheduled and on rare occasions, unscheduled maintenance and/or repairs provides us with the ability to run at full capacity almost non-stop. If we have a unit down for maintenance and were to have a second fail, we would lose some capacity, but still run at 80% output.

Just another option for your review. Good luck.

 

[BOCAJRS]

As mentioned before, the maintenance varies from plant to plant. We have a LM2500+ generating 28MW in our plant. It runs day and night and we only check internals every six months during a shutdown. It takes an 8hour shut to do that and replace parts on our annual shut. Annual shut is for 4 to 5 days.

 

[gaillee]

Thanks very much.

If our gas turbine and steam turbine can run for six months stablely, Everything is OK.
Now we already selected GE 9FA, the whole output is 280MW, so we can't use an N+1 design. Perhaps we should use an syngas-based boiler to supply the steam and power.

Another question is that 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?

 

[ahung]

For W501D5 100 MW Gas Turbines we have three types of maintenance according with Siemens Westinghouse standards considering base load running condition:

Combustor Inspection: Each 8000 EOH (Equivalent Operating Hours)The outage is complete between 3 or 4 days working with one shift of 12 hours. One time for year

Hot Gas Path Inspection: Each 24000 EOH. The outage is complete around 22 or 25 days working with two shifts of 12 hours each one. One time every three years.

Major Overhaul: Each 48000 EOH. The outage is complete around 30 or 32 days working with two shifts of 12 hours each one. One time every six years

You need to calculate the EOH using an equation. The formula consider full load trips, fuels: natural gas or oil etc. Normally each OEM (Original Equipment Manufacturer)has his own equations and formulas.

In our plant we have five Gas turbines model W501D5. One of our machines its running continuosly at base load condition for 93 days (3 months)

Recently SW inform to us that they have a new design gas turbines components more reliable for extend the time between every type of maintenance from 8000 EOH to 16000 EOH in others words you can run the machines more time because you don´t need to shutdown the gas turbines for do the preventive maintenance every 8000 EOH

Regards

Alberto J. Hung C
Caracas Venezuela