We have two Westinghouse W251B11A gas turbines running HBTU+LBTU blended fuel. These machines remain on base load through out the year. Evaporative coolers were installed during the commissioning of these turbines back in 1999. Now we are planning to install wet compression technology for power gain. It has been reported that other Westinghouse machines have gained as much as 7MW by this method.
I was wondering if any of the members have experience of wet compression on their turbines. We are specially concerned about our compressor blades. Though they have additional coating but still injecting de-mineralized water directly into the compressor may cause some pitting or corrosion. What other things should i be concerned about?

 

This technology does increase the power output as well as the life of the GTs'.You may refer to "Sprint Technology" for GE gas turbines.

Your concern about corrosion is true, that is why water injected should be chemically treated to adjust PH to permissible levels as well as decontaminating the water (achieved through the demineralisation stage).

The demineralised water injection should strictly follow operation conditions for proper performance, hence needs additional controls/logic added.

Hope that gives you a vague idea to start with.

This technology is widely being used in today's combined-cycle and co-gen GT based power plants, achieving efficiency up to 47%.

 

Ahem,

> This technology is widely being used in today's combined-cycle and co-gen GT
> based power plants, achieving efficiency up to 47%.

It's not being used as widely as George would have us believe. For the reasons he cited: Water (it's cost to obtain); it's treatment (essentially it needs to be boiler-quality water, with an adjusted pH--which also costs money); and the fact that the expensive, treated water is lost when it goes out the stack (it's not recoverable). So all of that money spent to obtain and treat that water is lost and gone when it goes up the stack and into the atmosphere. This must be factored into the payback (which might be advantageous when peak demand is high, but not so much at other times of the day/year).

The water also seems to have an effect on HRSG components which varies with application and any secondary type of emissions reduction in use.

There are other considerations which must be taken into account, as well. Some load couplings (the coupling that connects the gas turbine shaft to the generator rotor) must be sized and capable of transmitting the additional torque expected to be produced by the prime mover. The generator cooling system must be capable of removing the extra heat generated by the additional current flowing in the generator stator--and rotor. And the excitation system must be capable of sustained operation at elevated outputs expected to be experienced by the increase in power output. Finally, auxiliaries including main step-up transformers and transmission lines must be capable of the extra amperes which are expected to flow as a result of the increased prime mover output.

The increase in output can be substantial, so its effects on other components of the system need to be anticipated and understood for reliable operation.

It's a promising technology, but it's not ubiquitous--not by any stretch of the imagination. It may be that it's use is being considered and designed into new turbines and plants.

 

can anyone explain how electrostatic charge is build up in generator rotor coupled with gas turbine having wet compression system?