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gas solubilty in coco!!!
Posted: 10 December 2013, 06:34
by shoaibjadoon
i have been facing problem in finding the saturation solubility of Carbon dioxide in water, at different temperatures. can somebody help me in this regard???
secondly, when i am inserting a feed stream having carbon dioxide dissolved in water, my distillation column( chemsep UO) can not be solved. it gives me an error that my physical property settings are not appropriate!!!
can you please help me in this regard? Mr. JASPER!!!
muhammad shoaib
from pakistan ( UET Peshawar)
Re: gas solubilty in coco!!!
Posted: 12 December 2013, 01:36
by jasper
Predicting the CO2 solubility accurately is not an easy task; this requires an electrolyte model that predicts properly the reactions between water and CO2 (the formation of H2CO2, HCO3- and the auto-dissociation of water). Such a model is not present in TEA and requires a more advanced, or even custom implementation. Especially in case also other chemicals are involved that change the water chemistry.
If there are just water and CO2 involved, you could use a simple model that uses a Henry coefficient or solubility constant for CO2 in water. This might work if the CO2 partial pressures are low enough. Here is a source that would help with such a model:
http://www.nist.gov/data/PDFfiles/jpcrd427.pdf
But again this is not a standard model TEA implements, so some programming is required. The simple thermo package example of CO-LaN could be a useful starting point.
Re: gas solubilty in coco!!!
Posted: 12 December 2013, 13:07
by shoaibjadoon
thanks a lot dear sir,
i really have gained so much of a help from your expertise and have a tremendous regard for helping and replying me with so much authenticity and practicability.
lots of regards!!!
Muhammad Shoaib
from
UET Peshawar
Pakistan.
Re: gas solubilty in coco!!!
Posted: 14 January 2014, 13:46
by shoaibjadoon
dear sir (Mr.Jasper),
i have been asked repeatedly by my supervisor to find out solubility of CO2 in water OR CO2 in ethanol-water mixture without considering electrolyte effect with henry's coefficient?
but i do not know how can it be done ?
can you please give me a clue of of any possible solution to this problem???
regards!!!
Re: gas solubilty in coco!!!
Posted: 14 January 2014, 14:00
by jasper
Re: gas solubilty in coco!!!
Posted: 15 January 2014, 08:58
by shoaibjadoon
dear sir,
i am facing a problem of handling a stream fed to chem sep UO column as a feed having co2 in it as a component of that stream. the problem is that COCO always asks me to check physical properties of co2 which seem OK. can you please help me out of this problem???
i am attaching a flowsheet of my case study as well where i am handling this problem in solution process!!!
the problem asks me to have CO2 mixed with water and ethanol up to its saturation solubility in the mixture and then separate the mixture using two columns , first is the beer column and second is rectification column. both are to be designed in such a way that the heat integration saves heat input by half of that required by utilizing heat duty of condenser of rectification column to operate the beer column. the first column separates co2 as a top product and the second column gives azeotropic composition of ethanol water mixture that can be recycled as feed to first column.
Re: gas solubilty in coco!!!
Posted: 15 January 2014, 15:34
by jasper
The issues with this flowsheet have nothing at all to do with the warning to check the CO2 properties. You can in fact turn this warning off by changing the CAPE-OPEN options of the unit (not to show warnings).
Ross Taylor, ChemSep Author:
The first and most serious problem with this flowsheet is that the thermodynamic model selected is not appropriate for determining the Henry's law solubility of CO2 in water (much less that of solving the more difficult problem of determining the solubility in a mixed solvent of ethanol and water).
This problem needs Henry's law which is not available in COCO. It IS available in ChemSep but then you also need Henry's law coefficients for CO2 in ethanol which are NOT available (I do not know sources for Henry's law for CO2 in ethanol).
The second issue with this flowsheet is that (even assuming that the a proper thermodynamic model was selected (in ChemSep) the product specifications for the column are chosen in such a way that there is no chance of ever obtaining a converged solution. It does not make sense to ask a column to separate what is mainly a mixture of ethanol and water to obtain a top product that is 50% ethanol and a bottom product that is 50% ethanol. This is simply not possible. better specifications should be selected.
Note that even with appropriate specifications the results obtained for the column will be wrong because the thermodynamic model is not capable of properly representing this system.
Re: gas solubilty in coco!!!
Posted: 16 January 2014, 13:32
by shoaibjadoon
thanks in bundles sir!!!!
i really appreciate the commitment shown by your team for letting me know these points!!!