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Polyester Production Distillation Efficiency

polyester reaction efficiency distillation polyol polyester

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#1 Tolgahan

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Posted 01 September 2022 - 08:01 AM

Hi everyone,

I need your help: I would like to know how to improve vacuum distillation process regarding polyester production. The reaction is carried out at 220-230 degrees Celsius and bottom of the column at 110-120 degrees C and at these conditions much of the DEG and MEG is distilled off when removing the water produced by polycondensation mainly when working under vacuum distillation

If someone here has experience on this kind of process, please, help me with tips/tricks to improve my process decreasing the amount of glycol that is distilled off.

The reactor is charged with Adipic Acid, MEG and DEG.

 

I want to improve reaction efficiency.

.

Thank you all,



#2 breizh

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Posted 01 September 2022 - 11:23 PM

Hi ,

 BP of MEG and DEG  are very high compared to water. Separation should be easy.

Questions :

What type of packing to you use for this separation?

Do you have any reflux in place on your column?

How is managed the operation of the column, especially during start up? 

 

 

Breizh 



#3 Tolgahan

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Posted 07 September 2022 - 03:58 AM

Hi thank you for reply,
 
Let me explain current situation;
 
there is a packed coloumb which there are raschig rings inside the coloumb, also there is a condensder after the coloum. What comes out of the condenser is collected in the decanter.
 
cooling system temp  between 30-60 degrees. During the reaction cooling system temp is increasing. 
 
I think the biggest problem is the high temperatures in the cooling system.
 
There is a possibility that the system parameters cannot be controlled during the reaction. such as the positioning of column cooling valves.
 
What do I need to control in the system as a priority?
 
Do you have any resources you can recommend regarding distillation?
 

 

 

Hi ,

 BP of MEG and DEG  are very high compared to water. Separation should be easy.

Questions :

What type of packing to you use for this separation?

Do you have any reflux in place on your column?

How is managed the operation of the column, especially during start up? 

 

 

Breizh 



#4 breizh

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Posted 07 September 2022 - 04:58 AM

Hi,

You did not reply to me about the reflux? Do you have one in place?

Is it a batch process or continuous process?

What type of equipment do you use for the vacuum (ejector, Vacuum pump)?

How stable is the vacuum during the operation? 

What are the actual performances of the unit and what do you expect?

 

Can you provide a PFD of your process? reactor + column +decanter 

 

A general document about distillation/separation is attached.

Good luck

Breizh 

 



#5 Tolgahan

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Posted 07 September 2022 - 08:43 AM

Hi again,

 

there is not reflux on the system.

batch process

we are using vacuum pump

vacuum pump is working continuously at the set value

I want to increase the efficiency of the system. I think the system losing glycol while producing. therefore reaction time getting longer and reaction eff. drops.

 

 

 

Hi,

You did not reply to me about the reflux? Do you have one in place?

Is it a batch process or continuous process?

What type of equipment do you use for the vacuum (ejector, Vacuum pump)?

How stable is the vacuum during the operation? 

What are the actual performances of the unit and what do you expect?

 

Can you provide a PFD of your process? reactor + column +decanter 

 

A general document about distillation/separation is attached.

Good luck

Breizh 



#6 latexman

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Posted 07 September 2022 - 10:24 AM

No reflux?  Please confirm, is it just a single stage flash separation?



#7 breizh

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Posted 07 September 2022 - 08:48 PM

Hi,

You did not supply much information about your process (no figures, no schematic). What is the purpose of the decanter? Do you have a way to recycle Glycol accumulated back to your process?

It seems to me you are operating a still pot; you should have a reflux in place to minimize the carry-over of material to the decanter.

BTW you need to consider the whole cycle time of your operation together with a mass balance. 

Regarding your existing set up, you should have a temperature probe on the top of the column which should indicate whether the quality of the vapor is adequate. This temperature associated with the pressure is the BP of the light component i.e. water.

 

Breizh



#8 Tolgahan

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Posted 08 September 2022 - 02:06 AM

hi,

 

it seems there is a reflux line but they dont use this. decantor is a conderser drum. there is a pump for reflux from decantor and ıt goes to top of coloumn to sprink.

No reflux?  Please confirm, is it just a single stage flash separation?



#9 Tolgahan

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Posted 08 September 2022 - 02:23 AM

hi,

 

I am learning btw the process. I have find out there is a reflux line on the system bu they dont use it. decantor is a condenser drum. there is a pump belong decantor which works for reflux. It goes to top of coloumn to sprink. They said that they didn't use it because they thought it was not useful. now I have a shematic about the system. 

 

process flows like; glycol and water vapor goes to coloumn with packed raschig rings and then It goes to condenser and dacantor. 

 

there are many temp probe on the column and condenser.

 

 

Hi,

You did not supply much information about your process (no figures, no schematic). What is the purpose of the decanter? Do you have a way to recycle Glycol accumulated back to your process?

It seems to me you are operating a still pot; you should have a reflux in place to minimize the carry-over of material to the decanter.

BTW you need to consider the whole cycle time of your operation together with a mass balance. 

Regarding your existing set up, you should have a temperature probe on the top of the column which should indicate whether the quality of the vapor is adequate. This temperature associated with the pressure is the BP of the light component i.e. water.

 

Breizh



#10 Tolgahan

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Posted 08 September 2022 - 02:26 AM

https://resimlink.com/6lJuIx



#11 breizh

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Posted 08 September 2022 - 02:53 AM

Hi,

access denied to your attachment on my computer, please use the edit option button in this forum, use full editor, choose file, attach file to upload your document. submit the modified post.

 

 

Note: you should find out the process book, if any, in your facility or contact knowledgeable / senior managers to explain the process. I'm very much worried with your comments on operation and their understanding.

Prior to consider process improvement make sure you understand the process in depth including the function of each piece of equipment, starting with the naming, decanter should be receiver, right?

 

One way to learn is also to understand the safety matrix and interlocks /alarms sheets.

Good luck.

Breizh 



#12 Tolgahan

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Posted 09 September 2022 - 12:48 AM

I could't tell the problem as clear, sorry about that. I will share what I learned in the future. I have attached the process diagram.

I should understand princeble of the packed system distillation. If you have any doc. about wthylen glycol and water distillation please share with me.

 

Attached Files



#13 breizh

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Posted 09 September 2022 - 01:37 AM

Hi,

Your set up makes sense and reflux should be in place to prevent the losses of Glycol.

So far you don't share information about the performance of your current process and your expectation.

Good luck. 

Breizh 






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