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[Edinburgh]

Hi there,

I have been tasked with designing a methanol separation process as part of my final year project. The two units I am designing are a condenser and a single stage separator remove the light gas impurities and a distillation column to purify the water/methanol mixture.

I am unsure however how to start the condenser design. I am setting two variables: the pressure of the separator and the composition of the distillate. Which leaves the temperature to be calculated from this.

My feed stream consists of:
H2,CO,CO2,CH4, Methanol and Water

Ideally I need the water/methanol mixture to come off the bottom more or less pure and the other gases to come off the top. I understand that I have to get the partial pressures of each component via the equation:

pi = P*yi

which allows the vapour pressure to be calculated by:

pi^* = xi*pi

I am then using Antoines equation for using the methanol vapour pressure and its Antoine coefficients to find the temperature that it should be running at. Since the methanol will be the heavy key component in this situation. However this is giving me a operating temperature of 210K (using 1 atm and 99.98% of methanol and water coming out in the bottoms).

This is not really what I was expecting as I know that at room temperature H2,CO,CO2 and CH4 are gases and CH3OH and H2O are liquid, so I think I really should be operating above 273 at least. As i have never dealt with anything with this many varied components I may be on the wrong track and using the wrong equations. The main thing I would like to know is if I am on the right track?

Any feedback would be much appreciated, once I can get the operating temperature and partial pressures the rest of the design should be straight forward.

Attached Files

•  Condenser Problem.xls   229KB   23 downloads

Edited by Edinburgh, 12 February 2010 - 10:15 AM.