13 replies to this topic

[lnbsak]

In my study I am finding my optimized solution giving me 180 trays which I believe high. Is it?

 

So what is the practical limit of column height?

 

I would slit into two? Any reference?

 

Thank you!

Edited by lnbsak, 05 August 2021 - 02:40 PM.

[Bobby Strain]

So, what are you separating?

 

Bobby

[latexman]

That’s a lot of trays! Are you separating isomers?

[lnbsak]

So, what are you separating?

 

Bobby

1.7 mol % Ethylene Oxide, from water

[Pilesar]

Two columns might be better. There are transportation issues getting such a large column to the plant site and you should consider sway due to wind causing the trays to be unlevel, and civil problems getting a good foundation. You have an awful lot of trays for what is normally an easy separation between EO and water. I have only seen so many trays for very closely boiling components such as separating ethane from ethylene with high purity products. Unless you must make drinking quality water, consider recycling the contaminated water back to the EO absorber and not trying to get it any purer than it already is.

[breizh]

hi, 

Consider the link attached where you can find hints  ( thermo model NRTL , operating conditions )

http://www.owlnet.ri...r2599/EOweb.htm

 

Good luck

Breizh 

[Bobby Strain]

Something is wrong with your analysis. There is no separation in EO production so difficult. This sounds like an academic exercise gone wrong.

 

Bobby

[lnbsak]

Something is wrong with your analysis. There is no separation in EO production so difficult. This sounds like an academic exercise gone wrong.

 

Bobby

Sorry sir I forgot to add, this height(180trays) is just one of the optimized point. With 100-110 trays we found are enough but the reflux ratio (reboiler & condenser duty) was high. With 180 stages it (reboiler & condenser duty was high) was really low. The overall annualized cost was about 1% less for 180 number of tray.

Edited by lnbsak, 07 August 2021 - 01:58 PM.

[Pilesar]

If 180 trays is your final answer, then you are asking the wrong question. It may be possible that the constraints of the academic problem you are trying to solve require such a column, but your analysis is highly suspect. Maybe your thermo is wrong, maybe you have chosen a bad column pressure, maybe your product specifications are unreasonable. You have not supplied much info to us, but even your economic evaluation is likely not accounting for the costs correctly. If you had come up with 30 trays in your design, perhaps no one would have commented, but your 180 tray design is waving a flag saying 'something is very wrong here.' The answer just does not look correct and the flaws are hidden somewhere that you have not revealed.

[breizh]

Hi,

To support your work and considering your feedback , you need to understand 180 trays means a column over 50 meters high  (30 cm between each tray).As others pointed out , a lot of constrains attached to your design ( construction, erection, civil engineering , transport from the manufacturer to the site ,...) .

 

 

http://seperationtec...ay-selection-1/

 

let you think as an engineer and you should understand that something is wrong with your design ( Thermo model, operation condition,...) 

 

Attach your work for us to review it.

 

 

Good luck .

Breizh 

[latexman]

What relative volatility of EO to water is your study using? What are the top and bottom purity specs?

[horatorres]

 !80 trays is not a practical solution for a separation process. If is not feasible

 

 

Horacio

[lnbsak]

What relative volatility of EO to water is your study using? What are the top and bottom purity specs?

Sorry of being late

 

Relative volatility form the simulator ranges from 10-22 from top trays  to the bottom trays. With K of EO 1.2-22 anf k for Water 0.1-1.

 

Thank you!

[latexman]

With relative volatility of 10-22, it is inconceivable why 180 trays are needed. Something is wrong somewhere.