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Feed Composition Vs Feed Boiling Point

design basis

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#1 Arsal

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Posted 02 November 2015 - 11:19 PM

Are Refinery Unit design based on Feed Composition or Feed Boiling Point ?

As I understand that Feed compsotion and Feed Boiling point (D-86 Distillation) both are same things,if the initial boiling point (IBP) of feed is low it means feed have more lighter components...

 

Furthermore i understand that Feed Compostion is detailed of all present component in the Feed,while D-86 distillation shows the range of components...

 

so please enlighten on this topic specially for design basis for downstream units,like Reformer, Isomeriztion of C5/C6...???


Edited by rao arsalan, 02 November 2015 - 11:21 PM.


#2 P.K.Rao

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Posted 03 November 2015 - 12:15 AM

Distillation unit is designed to fraction-ate the crude into several fractions as per the boiling range required. Composition depends on the type of feed (crude oil) because different crude oils have different compositions. The hydrocarbons present in crude are mainly of four types, paraffins, iso paraffins, naphthenes and aromatics. Different crudes contain different levels of these hydrocarbons even though the boiling range may be same. For example, benzene and cyclohexane have close boiling points (80.1 and 80.7). So in a fraction of boiling range 70 to 90, the composition depends from crude to crude because some crudes may contain more of cyclohexane and some other crudes may contain more of benzene. The composition of fractions depend on the type of crude that is being processed for the same boiling range. 



#3 P.K.Rao

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Posted 03 November 2015 - 12:21 AM

All feeds are not suitable for C5, C6 isomerization because there would be no economics. Feeds containing good quantities of C5 and C6 normal paraffins (n Pentane and N-Hexane) are suitable



#4 Arsal

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Posted 03 November 2015 - 01:15 AM

Thankyou P.K.RAO

 

So design basis would be based on feed composition.??not on boiling point?

 

Boiling point (D-86) distillation define the IBP of Complete feed which also incorporate all the lighter components either benzene or cyclohexane.?


Edited by rao arsalan, 03 November 2015 - 01:16 AM.


#5 PingPong

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Posted 03 November 2015 - 03:45 AM

ASTM D86 distillation is just a very lousy distillation.

 

There are correlations to convert the D86 data into TBP data, but such correlations are not very accurate, so all you get is a lousy TBP distillation curve.

 

For the design basis of an Isom unit or a Reformer you really need a compostion of the feed. That need not be a complete composition of all the molecules, but at least you need a breakdown into parafins, isoparafins, naphthenes and aromatics separate for the C5's, C6's, C7's et cetera



#6 P.K.Rao

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Posted 03 November 2015 - 04:21 AM

Mr Rao Arselan, Please read my post. Distillation is designed to fractionate as per boiling range. Not as per  composition






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