Condensate Flow Through a Vertical Riser

[Mike4chemic]

Hello,
Does anyone have experience with this? Here's my situation:
We design a power facility which utilizes geothermal steam, which contains about 23% w. of non-condensable gases (mostly CO2). Steam enters to a kettle reboiler and condensed. The two-phase flow of condensate + steam/NCG at the kettle reboiler outlet is separated into a two-phase separator, when condensate is fed to a condensate preheater(see attached sketch). At the reboiler outlet conditions (pressure and temperature) condensate is at equilibrium with non-condensable gases (NCG),based on my estimation, the condensate contains about 0.15% w. of NCG , which is completely soluble into condensate. Due to the layout limitations we have to design the condensate pipeline to the preheater as a vertical riser(elevation about 5 m). As results of the elevation/friction losses, the condensate is flashed along the pipeline and part of the NCG is released. Based on my estimation, the concentration of the "free" NCG/Steam into the condensate pipeline is about 5%vol.
My question is: Should I be concerned from any flow problems(vapor locks, flow restriction and pipe vibration) through the vertical condensate pipeline, which contains about 5%vol. of free gas?
Thanks in advance, Mike

 

[BigInch]

5% by volume will not be a constant as % of gas volumes can vary considerably with actual pressure at the point. You might not experience difficulties when it is flowing at 5% normal conditions, but startup, or recovery from upsets might be more difficult than you are expecting.

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[georgeverghese]

a) Check the operation of this vertical riser for low flow operation when there may be flow instabilities. These intermittent gas slugs at low flow may affect the operation of the downstream condensate preheater.
b) This condensate - NCG mix appears to be cooled from 134 to 85degC from your simulation map at the condensate preheater. To enable proper operation of this preheater, noncondensibles should be vented off to prevent accumulation in this unit. No details posted on how this condensate preheater is configured.
c) Sounds like this steam- NCG mix is on the tubeside of this kettle reboiler. Why not on the shellside-that way, you avoid the need for this phase separator ?

 

[Mike4chemic]

Gentlemen,
Thank you for your answers.
Is it possible to estimate the minimum condensate velocity (low operation mode) through the vertical riser so that gas bubbles will be swept out?

Thanks, Mike

 

[LittleInch]

Yes. Try this.

https://www.google.co.uk/url?sa=t&s...UVuS3EnLAvJbVGGmg&sig2=PKLqwbPhUqpX4rEwSE7l1g

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

If it's a vertical riser flowing UP, then the bubble are going up even if the velocity is zero. Otherwise 2 to 3ft/sec usually works. You should generally never plan on operating anything at less than 3ft/sec anyway.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[georgeverghese]

Figure 6-29 in Perry Chem Engg Handbook 7th edition gives a rough indication of the flow ranges at which you can expect slug flow in vertical upflow co current gas-liquid streams.