12 replies to this topic

[ram13]

Hi,
 
This is M.Ramachandra Reddy from Hyderabad, India.
I am a Chemical Engineer working for a Pharma company. I was given with a task to calculate the number of theoritical stages ,minimun reflux raton ,diameter & height of the packed column to separate DMF(DImethyl formamide) from DMF+Water mixture in continuous mode
 
I need design of packed column in excel sheet for separating DMF from DMF+Water mixture for the continuous size of 1500 Lit/h. with below feed and distillate compositions.

continuous  size: 1500 Lit/h.
Composition of Feed: 1 w/w% Water, 99 w/w% DMF
Composition of Distillate: 99.9w/w% Water, 0.1 w/w % DMF
Composition of Bottoms: 99.8w/w % Water, 0.2 w/w% DMF
Type of Packing: Structured packing

 

here we are using vacuum distillation to separate dmf ,Please clearly explain from relative volatility to mccabe thiele graphical analysis

Please help.  Looking forward for your reply.

ramachandra reddy

[Bobby Strain]

No one is going to do your work for you. You might want to consult with your DMF supplier who might help you.

 

Bobby

[ram13]

No one is going to do your work for you. You might want to consult with your DMF supplier who might help you.

 

Bobby

ok sir tell me relative volatility of dmf+water under vacuum distillation at 85 - 90 degrees Centigrade

    

ramachandra reddy

[MrShorty]

Is there a specific part of getting relative volatilities for DMF/H2O that you have trouble with? What VLE model do you want to use? Do you have binary interaction parameters for that model?

 

If you don't have a model chosen, I note that both DMF and H2O are their own individual groups in UNIFAC's model. Assuming you are already familiar with gamma-phi models and the UNIFAC equations for estimating activity coefficients.

 

If you are not familiar with UNIFAC, there are several resources. The text The Properties of Liquids and Gases has a fairly thorough discussion of the method. Wikipedia has a page: https://en.wikipedia.org/wiki/UNIFACYou might search through this site's file library, because I believe there is a spreadsheet in that collection that can calculate activity coefficients using UNIFAC (I also think there is a spreadsheet that can use the Wilson equation, if you prefer Wilson's activity coefficient model).

 

I have not evaluated how well UNIFAC replicates experimental data for this system, but it might give you a good starting estimate for the relative volatility.

[ankitamdavane011]

I need design of packed column in excel sheet for separating DMF from DMF+Water mixture for the batch size of 1000 Lit. with below feed and distillate compositions.

Batch size: 1000Lit.
Composition of Feed: 10w/w% Water, 90 w/w% DMF
Composition of Distillate: 99.80 w/w% Water, 0.2 w/w % DMF
Composition of Bottoms: 0.2 w/w % Water, 99.80 w/w% DMF

so,how can i calculate

please reply me

[breizh]

Hi ,

Let you consider Google or other search engine . People are talking about liquid liquid extraction . Hope I put you on the right path .

 

Breizh

[ankitamdavane011]

which entrainer is used for the separation of DMF and water??

[MrShorty]

I am probably revealing my ignorance more than anything by responding, but I would ask back to you -- is an entrainer commonly used for this separation? From what I understand, entrainers are commonly used to "break" an azeotrope or otherwise make "difficult to separate" systems (where the relative volatility is close to 1 without a clear definition of what 'close to 1' means). Using a couple of different UNIFAC calculators, UNIFAC predicts activity coefficients near 1 for the dmf+water system, so the relative volatilities should be near the ratio of the vapor pressures (about 5 in the 50 to 100 C range). It seems at least possible to me that an entrainer would not be necessary to separate these two.

[deepak.vibhandik@gmail.com]

Hi,

I have designed it many years back, it azotrope distillation.
You need to take antonies coefficient of both components
You need to plot boiling point and dew point graph
Then you have plot vapor pressure graph for both vs temp based on vapor pressure and boiling Pont you get relative volatility
Then you need to plot x vs y vapor equilibrium curve
Plot no of stages
Calculate column dia
Get vendor data stages and length and HETP
then you can have good design.
Remember purity of Dmf is depends on layer separation after primary condenser collector, subcooler is good to separate

[ankitamdavane011]

hi

can anyone tell me.how to separate n-phenyl formamide and formamide

[MrShorty]

My mentor did not like these kinds of open ended questions. He strongly preferred that I present some kind of proposal or suggestion that he could critique rather than this kind of open ended question. In this spirit, I will simply ask the same question right back to you. What separation operations do you know about (this thread has been all about distillation, so I assume you are at least somewhat familiar with at least one separation operation)? Any first impressions you have about these different separation techniques as they might apply to your formamides?

[ankitamdavane011]

sir,

there are many separation techniques like distillation,filtration,crystallization,centrifugation,extraction etc.but which method i will apply for the separation of n-phenyl formamide and formamide.

[MrShorty]

I'm not sure there is a "magic" answer for this kind of question. You take what you know about the desired separation and the available technologies and determine which technologies seem like good candidates for the separation.

 

For example, you mention filtration. Off the top of my head, if I am going to consider filtration for a given separation, I would expect to look for a system where:

1) there is a solid component (at separation conditions) and a liquid component (at separation conditions). In other words, the melting points probably need to be sufficiently different.

2) the solubility of the solid (at separation conditions) probably needs to be low.

 

I would look up or estimate those properties and determine if filtration seems like a good candidate technology for this separation.

 

It seems to me that choosing a separation technology is about matching the properties of the system/mixture/solution (which means you need some ways of estimating or looking up those properties) with the properties that make each separation technology "work".