Upflow in vertical condensate pipe 1

[Phagwa]

How feasible is an upflow in a vertical condensate pipe, without using a pressurized (flash) tank?

Please assume modulating steam consumption.

 

[Phagwa]

Note: assume ~10% flash steam!

 

[katmar]

Two-phase (gas liquid) flow in the upwards direction is probably the least troublesome situation you can have with two-phase flow because the bouyancy and pumping directions are the same. Provided that you size the pipe for the degree of flash you expect I cannot see any problems.

You said you do not have a pressurised flash tank, but I assume you have a tank of some sort to allow separation of the two phases or you could have some entrainment of the liquid with the vapor.


Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Phagwa]

Katmar, thanks for your answer.

Actually I do not have any kind of tank downstream of the steam trap. The condensate from the heat exchanger passes an isolation valve, a drain point, the steam trap and a check valve. Then is goes upward, 10 feet. I suspect the designer of the installation has overlook somethings...

Please your thoughts on the current condensate return system.

 

[katmar]

Yes, I think something has been overlooked!

During the early stages of process development you often see lines on flowsheets that end with arrow heads and are labelled something like "to safe disposal" or "to return header". As the design is tightened up these lines get developed into proper designs, but it sounds like yours escaped the net.

Apart from going nowhere, it sounds like a reasonable design.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[25362]

To avoid hammering by imploding steam bubbles these shouldn't meet colder condensate in the overhead return line.

 

[Joesteam]

As stated, going up is no problem as long as there is enough pressure to push it. Be very careful if you have a modulating control valve on the steam inlet to the heat exchanger. During periods of low steam needs, the control valves modulates closed reducing also the pressure of the steam in the exchanger and lowering the available pressure to push your condensate upwards, even 10 feet up is about 5 psig.
This is a common problem, often called 'Stall'. This will cause the water to back-up in the heat exchanger, possible water hammer, and poor process performance.