Problem with investigate HCl removal column

[andrejkucma]

Hi, Im asking for helping me with investigation ofHCl removal column with 70 etages (condenser is 1st). Column have two feeds. 1st gaseous on 28th etage( m=10-14 tones/hour, t=10-20°C, mass comp: HCl 0,66; EDC 0,06; VCM 0,24) and second liquidus on 32rd etage (ˇm=26-30 tones/hour; t=50°C, comp w/w HCl 0,07, EDC 0,62, VCM 0,31). column have 70 etages, , total condenser (P=916 kPa), limits: 20 ppm VCM , operating temperature is about -34,5°C.From condenser goes 2 streams, 1st gaseous, and 2nd liq (2tones/hour) Total Reboiler has P=986kPa, limits for HCl 1 ppm,usualy works in 83-85°C. I ussualy work with PR thermodynamics. I ll be thankfull for any help. Does exist any reason, why its never works in flowsheeting document?

[jasper]

It is hard to say anything about why it will not work without the entire set of inputs you are using. Could be an improper specification, could be that the purity specification is too high for the column you are using and the thermo that you are using (which may or may not be a reasonable choice, but even that is hard to say anything about without knowing what is EDC, VCM and which other compounds may be present).

Can you include the fsd file?

[andrejkucma]

Max file allowed is 512 kb. my file have more than 1mb. can I send it via mail?

[jasper]

A typical file containing only thermo, a few streams and a column is not that large. If there are other items in the file, remove them before posting? Also, clear the log before saving.

[andrejkucma]

here is flowsheet of cleaning VCM section after cracking reactor. Column for HCl removal is only fiction column now.

[jasper]

I was expecting you would send a flowsheet containing only a column that does not work. Instead I see a flowsheet for which I suspect the column you have trouble with is not there, and the flowsheet solves ok.

Would it be possible to instead post an fsd file containing the problematic column?

[andrejkucma]

yes,please wait a minute. in this flowsheet is prolematic colm only fictional. There i use compound splitter, some heat exchanger, etc.all this is in black line. now I ll send you only the streams what are going into and out of column,

[jasper]

Please also include the column, so that I can see your intent

[andrejkucma]

preferable temperature on top is cca 240K, on bottom cca 359K. upper both streams can contain max 20 ppm w/w VCM, no EDC, bottom stream 10 ppm HCl. liquid side stream is solve from pumparound 1->2.

[jasper]

You have a top specification of HCl purity, as well as a bottom specification of HCl purity. Clearly they cannot both contain a mole fraction of 1e-5 HCl.