Capacity Upgrade Requirements

[zizzuu]

Hi,
l am interested in the plant areas that would need to be investigated/modified in order to upgrade the capacity of a large coal fired turbo-generator.
Thanks in advance

 

[byrdj]

Improved turbine steam paths

 

[metengr]

For a study of this kind, I believe the first question you need to answer is if the current boiler output is limited by the turbine/generator or is the turbine/generator output limited by the boiler?

Once this question is answered, one can develop a punch list of modifications to either increase boiler output or perform steam path uprates to increase output of the turbine up to the maximum rated value of the generator.

Increase boiler output -
reducing slag build-up or gas path fouling
steam circuit modifications
fuel delivery into the boiler or fuel changes
evaluate feedwater flow into the boiler

Increase turbine output -
as mentioned above, turbine steam path modifications

 

[davefitz]

Nearly every part of the plant was designed to max out at the original design capacity , plus sufficient margin to offset any risk to the plant designer. Even if the boiler, mills, fans,pumps, steam turbine , generator, transformer, T+D were upgraded or deemed adequate for a 10% increase, you will still need to ensure the condenser, thermal discharge, emissions limts, etc. are met. In other words, you would need to execute a complete audit of the plant , including such fungible items as emmission permit levels and whether new regulations would kick into effect as a result of the upgrade.

In modern western countries that need to respect emmission levels, the likely means of upgrading capacity of an old coal fired unit include:

a) steam turbine blade path upgrade. Not only does one restore the original efficiency lost due to SPE solid partical erosion of HP inlet blades, but modern 3D CFD techniques to design trans critical blade geometries and numerically control the blade shaping tools has led to dramatic improvements in stage efficiencies- espescially LP L-1 blades. The efficiency improvement forestalls the need upgrade other upstream components ( boiler, mills, fans,pumps)and also lowers the specific emission levels of pollutants ( ton pollutant / MWe-hr).

b) mill upgrade- convert to dynamic rotating classifiers- for improved coal fineness and mill capacity. The improved fineness reduces furnace slagging and improves unburned carbon levels while increasing mill capacity, espescially when using lo nox burners.

c) furnace water deslaggers- if furnace slagging is limiting max output of the unit , converting wall blowers to water deslaggers with modern spray nozzle control logic will protect the tubes from thermal shocks while improvig the deslagging ability.

d) convert to a parrallel powered combined cycle - install gas fired gas turbines at site and use gas turbine exhuast heat to heat boiler feedwater- both the coal fired boiler and the gas truibne are used at teh same time. This is espescially useful on coal fired boilers that were de-rated due to excessive NOx or furnace slagging.

 

[EdStainless]

As you look at upgradeing the feedwater/steam side don't overlook your feedwater heaters and condensers. Switching metallurgy can have a big impact.
When you want to talk details let me know.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[byrdj]

advancements in steam path design allows increased output with same balance of plant. (Generator and transformer must have margin) besides LP, there has been significant HP improvements. GE, Hitachi, Alstrom offer such upgrades, no matter what the original.

Inteesting point, after replacing HP section and getting 50MW increase with same coal compumtion, EPA wanted to re-evaulate and implied "boiler" was modified and needed to comply with new regulations

 

[zizzuu]

Thanks Everyone,
At this stage I am only focusing on modifying the turbine and condensate cycle as the boiler is deemed to be at maximum output capacity.
The new turbine components and improved sealing have been addressed and along with pump and feedwater heater rerating. I was more interested in the finer points that if left unaddressed may catch me out once we fire the beast up.