Backpressure steam turbine drives 1

[joejoe23]

I have little experience with steam turbines, and I was hoping someone can shed some light on the best way to condense the steam exhaust and recover the condensate. I have a 5psig backpressure turbine at 17,350lbs/hr exhaust. Are there mfrs who make pre-packaged condensers for such an application? Also, am I right to conclude that I would need enough river water flow to remove the latent heat of vaporization to go from saturated steam to saturated liquid, or 960btu/lb at 5lb?
Thanks for any help you can be.

 

[Montemayor]

Joe:

One way to conserve cooling water when condensing back pressure steam from a turbine is to run the exhaust through an air-cooled, finfan tube bundle and let the atmospheric air be the heat sink.

Yes, there are a lot of suppliers of this type of equipment. If you are contemplating using river water as the cooling fluid, then you will indeed need what you estimate to remove the latent heat of condensation - assuming you will maintain the condenser with the 5 psig of vapor pressure, and not flash down to atmospheric pressure.

 

[joejoe23]

Thanks Montemayor. Do you have some mfr's in mind that provide backpressure turbine condensing units? I searched the internet, and only seen applications for condensing turbines with large scale condensers for power plants...not for smaller turbine drives powering air compressors. Thanks again.

 

[dcasto]

google air cooled steam condensor here's the first one

http://www.geihamon.com/Air-Cooled-Vaccum-Steam-Condensers.html

 

[rmw]

What dictates that your turbine back pressure is 5 psig? Do you have a low pressure steam system that the turbine exhausts into?

What type of plant is this? Is there the need to heat anything with low grade heat? For example, the sugar industry uses 5-15 psig back pressure turbine steam exhaust to boil sugar juice to concentrate it. Do you have something to heat.

If not, why can't you exhaust into a vacuum? If you can you can reduce your water rate on the turbine. If you can't then any condenser manufacturer can make a positive pressure condensing unit. Try

http://www.graham-mfg.com

for a start. There is also a website

http://www.vacuum-guide.com

that has lots of links.

That you have this backpressure to deal with is curious to me.

rmw

 

[joejoe23]

rmw, thanks very much for your reply. I will check to see why we are setup with backpressure turbines. As far as I can tell, they only have perhaps a winter time space heat load for the waste heat, but this shouldn't be very much to forego the added turbine efficiency of exhausting into a vacuum. I believe we would save about 1/3 of the steam load with the condensing turbine. Thanks very much for your insight.

 

[joejoe23]

Thanks dcasto for the link!

 

[MJCronin]

jojo...

I have had experience with older BPSTs and they are almost impossible to reuse from another application.

You must undersatnd that "back pressure steam turbines" (BPSTs)are constructed differently than "condensing steam turbines".

BPSTs are much smaller and do not include the longer (and much more expensive) last stage blades that provide most of the shaft power delivered by the condensing steam units.

BPSTs are commonly found in large process plants with continuous steam demand.

BPSTs are designed to thermally "fit" within an existing steam distribution system. The operation of the BPST must be integrated with the operation of the entire steam distribution system. They can be cost effective when they replace a pressure reducing valve.

http://www1.eere.energy.gov/industry/bestpractices/pdfs/steam20_turbogenerators.pdf

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

http://www.snm.co.jp/product/inner2_1_2.html

http://njchp.rutgers.edu/files/Steam_Turbines.pdf

Was this BPST used in another application where there was a 5 psig distribution header ? If so, the condensing and steam usage requirements of the LP steam system controls the BPST operating requirements

My opinion only

-MJC

 

[rmw]

MJCronin's post reminds me that in a reverse situation once where a university campus utility plant wanted to change their operation from a LP (15 psig) extraction/deep vacuum condensing machine to just a straight extraction machine (by condensing a small amount of bypass steam at the extraction pressure) had to remove several rows of the last stages to make it work.

rmw