Steam Power 1

[cleng07]

A vendor quoted a steam turbine generator that will take 29,900 lb/h of saturated steam (300 psia/417°F) inlet & 40 psia/267°F saturated steam exhaust yielding between 700-800 kW electricity. My calcs only yield 290 kW (from steam tables)... what am I doing wrong?

 

[rmw]

Is it a straight extraction turbine or is there some condensing?

rmw

 

[cleng07]

Thank you for responding, rmw. I figured it out; the exhaust vapor fraction was less than one (yes, some condensing) which yeilded a greater delta ethalpy than I originally calculated when I assumed all vapor exiting. This is a back pressure turbine generator and after realizing that there was some condensing, I was wondering how a non-condensing turbine can have condensing take place. Thanks again.

 

[MJCronin]

See page #2.....

http://www1.eere.energy.gov/industry/bestpractices/pdfs/steam22_backpressure.pdf

I still do not understand how this can be "kind of" a condensing turbine.....????

Can you explain

Is there a true condenser, with a hotwell, pumps etc on the tail end of this machine ? Where does the discharge go ?

Or are you just in the thermodynamic range of condensate..?

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-MJC

 

[cleng07]

MJC,

I am assuming the latter, no condensers, a skid unit to replace a PCV would consist of following: Single Stage Steam Turbine, Synchronous Generator (1,800 rpm rated @ 700 kW), Speed Reduction Gear, High & Low Speed Couplings.

We produce approx 29,900 lb/h of 285 psig saturated steam that is knocked down to 25 psig via a PCV. This vendor is stating he can replace the PCV & power our plant, so I am just now learning/researching the application. I thank you for the link.

Another concern is how the unit performs w/ significant fluctuation in the inlet flow rate (lb/h HP steam) with or without a VFD.

 

[rmw]

I can't picture a VFD in this equation. If your steam flow is fluctuating, your ability to produce power will fluctuate. Your generator (unless your plant is an 'island') will run synchronous speed with the grid speed so the torque produced by the turbine to generate power will be a function of the steam available to spin it.

Is there anything else that you can drive with this steam?

rmw

 

[cleng07]

Such as? A pump? I don't believe so, everything is electric here. We use the LP (25 psig) steam to heat our buildings in the winter, in the summer we only condense it. Perhaps you are suggesting that I consider other applications (i.e. pump) instead of a generator(?)... interesting.

cls

 

[dcasto]

You will control the system with a by-pass valve around the turbine. If you don't need the energy, you just bty-pass some steam. The by pass will sense the turbine inlet pressur and if the turbine has cut back, that pressure will rise and the bypass valve will dump steam to keep things in control.

the tricky part will be a load sharing system for when your power demands exceed you power production.