Can a vacuum system be used in condensate receiver? 2

[lotus7312]

Hi, all,
I am wondering whether a vacuum pump can be used to assist condensate flow back to a condensate receiver. Normally, there is a vent in the receiver to vent the flashed steam generated by high pressure condensate. How can I handle the flashed steam problem if a vacuum is used? What kind of design should be considered in this system?
Thanks

 

[pmureiko]

You can try a vacuum pump to boost the the pressure on the flash steam. Unfortunately the steam is saturated and you will condense some of it in the compression. It may be better to pump the higher pressure condensate back to the boiler feed water system to recover the water and it's heat content.

 

[Montemayor]

lotus7312 (Chemical):

I tried this years ago and ran into the following:

1) Your condensate receiver at the boiler room has to be rated for FV (full vacuum) service; this is not usually the case and requires an expensive re-rate.

2) You are theoretically limited to a maximum pressure assist equal only to the maximum vacuum: 14.6 psi; this is not a large delta P by hydraulic standards.

3) Creating a vacuum at the condensate receiver only makes the NPSHa for the boiler feed pump worse; you may have to revamp the pump's configuration - or maybe change out the pump! This could get expensive.

3) As pmureiko suggests, I found that locating a small centrifugal at the condensate source proved to be more effective and controllable; in fact, I did this on an area-wise principle: I used various similar sources to the same condensate collection system and pumped the condensate back to the power house on level demand. Pumping liquid fluids is much more cost effective than inducing them with vacuum.

I would still do the same today. I hope this experience helps.

Art Montemayor
Spring, TX

 

[saxon]

lotus, Why a vacuum pump? Utilize a self powered pumping trap at the source of condensate generation. Check with either Armstrong Machine Works or Spirax/Sarco. These are standard off the shelf items.

Hope this helps.
saxon

 

[Joesteam]

Vacuum pumps are commonly used in low pressure heating systems. They have two sections, a vacuum section that 'pulls' the condensate and a liquid section that pumps the condensate out. They are sold as a complete unit, and mostly used in building heating with low pressure steam. With higher pressure condensate, I believe it will take a very large pump to establish a vacuum.

 

[lotus7312]

All,
Thank you for your input.

Saxon,
Can you explain the function and principle of powered pumping traps? I never used it before.
Thanks

 

[saxon]

lotus, Instead of taking the time to write up the operational cycles of this type of trap. see the following site:

http://www.armstrong-intl.com/products/condpumps/pdf/bt230c.pdf

saxon

 

[saxon]

lotus, It looks like that URL is case sensitive, try this one:

http://www.armstrong-intl.com

saxon

 

[lotus7312]

Saxon,
Thanks a lot. That is really helpful.
lotus