steam recovery suggestions?

[kyhan]

hey guys i've a sizable amount of steam coming out of the atmospheric flash drums and its thought that recovering the steam might be profitable. Aside from passing the steam through a heat exchanger... any other options? The heat exchanger isn't an attractive option is because of its impact on the other heat exchangers down the line. there's quite a bit of steam to condensate -- 20,000lbs/hr!

 

[katmar]

If you are generating your steam at a higher pressure than you are using it at, you could use a thermocompressor (Ejector) to pump up the waste steam to a higher level.

 

[bewdley]

Or compress steam via centrifugal compressor to reach some 2 bar abs - assuming you have a use for that. For 20k#/h you should use some 400 kW.

 

[Joesteam]

There is not much use for atmospheric steam, so if the processes can handle a back pressure, you can get a pressurized flash tank and use the low pressure steam. A common use is in a dearator if you are near the boiler room.
Here in NYC we do grab some BTU's out of an atmospheric flash tank by running coils through them to preheat cold water. Here it is not really a heat exchanger but rather a designed flash tank with coils, so it does not effect the backpressure on the condensate.
Hope this helps.

 

[sshep]

The dearator is a great sink. If you have distillation columns with low temperature bottoms or waste water steam strippers, then these are good candidates to soak up low level heat. Lowering the pressure of an existing column to use LP steam could be a big win. LiBr chillers can soak up some low level heat, but chillers will ultimately need to reject heat to a cold utility.

Even better is to insure that heat utilization at higher temperatures is close to the minimum energy requirements (i.e. pinch analysis), and that useful waste heat is recovered before letdown to atmospheric pressure. This will insure minimum flash steam generation.

best wishes, sshep

 

[kyhan]

Thanks guys. I learnt quite a bit form your suggestions. The reason why we flash it to the atm. is that we want to get rid of the salts and what not in the flashing water. The atm. flashing should not be changed. Right now i'm working on to see if we could connect the vent to a packing/tray tower and try to recover as much clean steam as possible. Maybe that'll work, hopefully there's enough pressure for the steam to go through the tower.