4 replies to this topic

[Hazem Hawwash]

Hi all,

 

I am currently designing a two feed distillation column separating methanol and water, at 1 bar, for an MTBE third year design project. I have derived the operating lines, in terms of both feeds, and have set up a spreadsheet for a Mccabe thiele diagram. I am however confused and lost as to how to calculate the reflux ratio. Once I find out how to caclulate the reflux ratio, I believe I can use lewis matherson and lewis sorrel methods as well.

 

I would be very grateful if somebody could shed some light on this and how to calulate the reflux ratio with two feeds. 

 

Kind regards,

 

hazoomeh

[breizh]

https://escholarship...96n0xv#page-256

 

Consider the resource above, you may find pointers to support your work.

Good luck

 

Breizh

[Bobby Strain]

And, pray tell, why does one need more than one feed to distill methanol-water mixtures? Especially in the MTBE process where all the stream comes from the wash tower.

 

Bobby

[Hazem Hawwash]

Thankyou Breizh, I shall check that out.

 

Hi Bobby, there is a flash drum before the distillation column. The intention was to put the vapour stream (in liquid phase) as the feed to the distillation column, however, the liquid stream out of the flash drum does not meet the specification required. Therefore, I have designed it as a two feed distillation column. The pressure of the flash drum feed is at 8 bar and I intend to reduce it to 1bar, I thought that I could take advantage of the separation in a flash drum as well as pressure reduction. I am thinking that If I use a flash drum, the size and number of stages in the column will be smaller and hence cheaper.  If I am wrong, please feel free to correct me, feedback is much appreciated.

 

Kind Regards, 

 

Hazem 

Edited by Hazem Hawwash, 25 June 2016 - 12:25 AM.

[Bobby Strain]

You are definitely wrong to separate vapor and liquid before feeding the column. You can get free software (ChemSep) from the internet. With this you can simulate the operations. Good luck.

 

Bobby