5 replies to this topic

[Achilles@6]

Hello everyone,

                           I am a 2nd year student and I am doing an internship. I am currently facing some difficulties in finding solutions to the problem i am assigned to rectify. The problem is with a distillation column in the plant which is used to recover the pure solvent after being used in another unit in the plant.The solvent to be purified can have a wide variety of impurities like turmeric traces in acetone etc ( Its a spice extraction industry) The distillation column( metallic structured packing) had a collection rate of almost 175 kg/hr in the beginning year of its operation( 2012) which decreased gradually to almost 150 kg/hr of present collection. Nowadays, when tried to increase the collection by increasing the reboiler duty, the pressure drop was found to increase ( increased earlier also, but at a higher reboiler duty) due to which the impurities were triggered upwards and reached the reflux tank( Must be flooding). This implies that, the velocity at which flooding occured decreased as time passed. My questions are:

 

1) What are the possible reasons that flooding occured at a lower velocity thereby reducing collection                indirectly?  (Is fowling the reason?) and what are the possible solutions?

 

2) Have only limited data like reboiler temperature and pressure, pressure at top and bottom of the column ,      height and diameter of column. I know to use Aspen Plus, but don't know what all I can do with Aspen           with  these limited data to increase collection.

 

3) The concentration of impurities is always very less compared to that of solvent. So are there alternatives      to distillation ( Like large scale     chromatography? )

[curious_cat]

Fouling of column packing? Physical packing damage? Corrossion? 

 

I'm not even convinced whether what you are seeing is indeed flooding. 

 

Alternatives: Adsorption? 

[popo]

Fouling of the packing seems the most likely to me too. But it wouldnt hurt to check for :

 

- fouling in the boiler (heating ) ?

- Too much reflux ?

[curious_cat]

 

- Too much reflux ?

 

If packing efficiency has gradually gone down operators may be compensating by increasing the reflux. 

[Achilles@6]

Is fouling a prominent phenomenon in distillation columns? The column is only 1 year old and the column is cleaned each time once the recovery of solvent is done as the next solvent to extract may be different. Therefore can the reason be fouling??

[Subhash29]

Pen down the data you have, so that we can elaborate the thinking of what might be the case?