Condensate Return System 2

[Hogweed]

I have designed a fuel oil heating system using 15 bar superheated (190°C) with coils inside two 4000 m³ tanks. My questios is how i can design my condensate return system. May I direct the condensate right through the deaerator or I have to include some collection/pumping system??

Thanks

 

[TD2K]

You shouldn't need a pumping system. If you have a header extending to the deareator or its feed line, the pressure back at the tank is the deareator pressure plus the line losses through the condensate system. I can't see you having a problem with 15 bar steam not having enough pressure to get back.

Remember to size your return header for two phase flow if your steam trap on the heating coils will remove the condensate at saturated conditions since it will flash in the header. Armstrong and Spirac Sarco have some good booklets on steam trapping you might want to look at on their websites. Armstrong and Spirac both recommend sizing the return header based solely on the flash steam (since it's the major component on a volumetric basis) and gives you some velocity guidelines, I believe around a maximum of 7000 feet/min.

Coils inside tanks are typically sloped so that the condensate runs to the low outlet point. From there, you will have a steam trap that will discharge the condensate as it's formed to your return header and then back to your deareastor.

 

[Hogweed]

You´re absolutely great TD2K!!!.
Impossible to find more information in such small message...

Thanks a lot.

 

[TBP]

Just a note on the superheated steam aspect of your project - you very much do not want superheat for a heat exchange application. Superheat is sensible heat, and you need to get past it, to get to the latent heat, which is where all of the action is. Your heat exchanger will very much behave as if it is airbound until the superheat is gone. Normally, the little bit of superheat you get downstream of a control valve is not an issue, but if you have superheated steam being fed to a control valve, you may have some heat exchange problems.

 

[steam4]

I agree with all that has been posted. But...if you have a temperature control valve involved, the condensate cannot be raised, and a condensate pump will be required.

Dave

 

[abcmex]

steam4,
Your comments regarding temperature control and condensate pump are well intended. Many times this issue is not known.I think may depend on the operational temperature of the fuel oil. If the fuel oil is kept below 100 deg you may experience problems.It also depend on the return line characteristics.

Hogweed,
there are some new trap designs that can even overcome the problem mentioned by steam4 due to the fact that they include a integrated pump (Spiraxsarco et al).

kind regards

 

[MJCronin]

Hog,

In my opinion, the above comments are accurate and helpful...

I agree with TBP, the use of superheated steam in, what seems to me to be a saturated steam application, should be discussed.

I believe that control of tank heating will be a problem, and at 190C you may risk the "char" the fuel oil ( Is it #6 fuel oil ?) on the heating coils.

Have you considered the use of a "desuperheater" in your system ? Saturated steam is more "potent" and a lot easier to control. You will need a source of water at ~ 16 bar to make a desuperheater work.

For more desuperheater info, try

http://www.dezurik.com/MNSD_desuperheaters.htm

http://www.komax.com/Default.htm

This system sounds a lot like the emergency fuel source in a power plant application, is it ?

My opinion only.....


MJC