6 replies to this topic

[engeng]

Hello to ALL

I would like to do simulation by Aspen hysys for Vacuum distillation unit of reduced crude (RCR), I have the analysis of RCR, the analysis is GC acc. to EN15199-2. My question is : can I use this analysis of RCR as TBP to do simulation, or what can I do ?

 

 

[StealthProg]

TBP WT is the best option. None of the high temperature simdist or gc type methods will give you a full distillation to the residue endpoint. So ideally you should know how much of the sample was not vaporised and extrapolate the curve to the final boiling point of choice.

Edited by StealthProg, 11 February 2021 - 05:56 PM.

[Pilesar]

Your analysis is meant to substitute for TBP. Make sure you enter it as weight basis or volume basis according to how it is reported to you. Accuracy is improved if you recombine product stream analysis to reconstruct the feed. 

[StealthProg]

Also its better not to use hypocomponents boiling above ~850C.

[engeng]

Thank you very much. I get the hypocomponents boiling point up to 850 C (>99.9 %), so if I am going ahead with simulation is there any big deviations in the result. ?

[SilverShaded]

Thank you very much. I get the hypocomponents boiling point up to 850 C (>99.9 %), so if I am going ahead with simulation is there any big deviations in the result. ?

It depends, personally i dont trust GC methods for residues.  They don't analyse the pitch portion which is non-volatile and there is undoubtedly some cracking takes place which may skew the results slighlty.  However this is a typical type of analysis that's given recently so we often have to make use of it.  A small amount over 850 isn't a problem, the issue with using quasi-components over 850 is that the fundamential thermodynaics above that point is a total fantasy, none of the characterisation correlations were devoloped for that a high a boiling point and secondly the pitch portion doesn't boil at any temperature anyway even under a near full vacuum, so assigning components to it at very high boiling temperatures is pointless and you find the thermodynamics fails to converge.

 

[engeng]

Thank you very much