CONDENSATE 1

[svv]

Hi,

I was wondering if anybody would be able to help me with this problem?

I need to calculate the amount of condensate formed in a pipeline after shutdown?

Initial parameters:
Steam flow = 250 kg/hr
Pressure = 45 bar
Temperature = 260oC

I tried to do this in hysys. I put in a stream with the initial conditions and then put in a pipe segment to obtain the amount of condensate that has formed.

Is this approach right? Can this be modelled in dynamic simulation? Can this be done in depressurisation utility in hysys? Any suggestions would be helpful.

Thanks

svv

 

[Joesteam]

I am sorry but do not know hysys, however the problem is fairly straight forward.

Take the diameter of pipe and length of run to get a total volume. Take the volume of steam at your working pressure based on the steam tables. This will give you the weight of steam which will be weight of condensate.

 

[TD2K]

Joesteam is exactly right.

This is an example trying to use a computer simulation program like Hysys for a simple calculation is way overkill.

 

[quark]

Joesteam is right. Check the volume of piping. This is the volume of the steam at atmospheric pressure. Multiply it with 46.01 and divide it by 1.01 and you will get volume of steam at 45Bar pressrue. Check specific volume of steam at saturation temperature. (actually the saturation temperature is around 255[sup]0[/sup]C). Check the mass of steam and that is mass of your condensate. (volume of 1 kg of condensate is 1 liter).

You should be careful about not letting the steam condense in the pipeline because the volume of fluid inside reduces by approximately 44 times, and this may damage the pipe over a period of time. It is better to let the steam drained off.

 

[25362]

All answers are right. If, as I pressume, the line is thermally well insulated, it will take some time to get full condensation as estimated above.

 

[svv]

Thank you all for your responses. I have taken your advice and have calculated the amt of condensate that will build up in the pipeline during shutdown and it was estimated to be around 1 litre.

How do I now calculate the amt of condensate (excess) that will form in the pipeline during startup (assuming 20 mins), when the pipeline is cold and when the same steam is pushed through the pipeline.

Can anyone point me in the right direction?

Thanks

svv

 

[poetix99]

A rough answer might be enough for your purposes:

Ignore the steady state heat loss throught the pipe insulation (I assume that your pipe IS insulated; if not, this approximate solution will be less correct).

You can then say (approximately) that the "excess" condensate formed at start-up is equal to the energy required to heat the mass of pipe from room temp. to the saturation temp. at 45 Bar (~255deg.C).

Calculate the mass of the piping in question
(handbook information is available for standard pipe sizes)
Add some extra for heavy valves and fittings, if they comprise a significant amount of the pipe run.

The amount of condensate = [(mass of pipe)*(thermal conductivity of pipe)*((255 - 25) deg.C)] / (latent heat of vaporization of steam at 45 bar)

 

[quark]

http://www.armstrong.be/pdf/N_101.pdf

This is the best source to know about condensate and traps.