9 replies to this topic

[Himanshu Sharma]

Dear All

I am working for an optimization study wherein I have to blend crudes and calculate the properties arising thereafter.

Please share various correlations for predicting various properties of Blended Hydrocarbon streams. Any information and resources will be of great help.

I am particularly interested in

Pour Point
Viscosity (I am using Refutas)
Octane/Cetane Number

[Zauberberg]

I think you need something like Spiral's Crude Manager. I remember that Planning and Optimization group within our refinery has been quite happy with CM's calculation capabilities:

http://www.spiralsof...anguage=English

Other than that, referring to Nelson's classic "Petroleum refinery engineering" might be of some help as well.

Good luck,

[Chellani]

Himanshu,

Few oil companies use octane number and cetane number (of specific components) which they’ve specifically derived for blending and these numbers are different from usual octane & cetane number. These blending RON & MON values along-with volume fractions are used to get property of blend.
I guess these properties are derived from the blending rules that they’ve learnt / derived from their experience and have back-calculated correlations something like given (don’t know the source)

Research Octane Index (ROI) of a component or a stream
ROI=1/(1+EXP(-0.05594*(RON-102.94)))

Similarly Motor Octane Index (MOI) can also be calculated using MON.
ROI and MOI of mixture is summation of ROI / MOI of individual cuts multiplied by volume fractions. Once you know ROI & MOI of blend, using above equation you can calculate RON and MON of mixture.

Similar concept applies to viscosity where viscosity index is used for estimation of viscosity of blend. Haven't seen anything for pour point yet but pretty sure that someone would have published correlation for that as well.

I am sure that you’ll find lot of similar equations and I don’t think any of them would be 100% correct but would not be 100% incorrect as well as they are empirical equations based on experience & experiments.

Hope this would be helpful to you.

Edited by Chellani, 25 November 2010 - 03:36 AM.

[Himanshu Sharma]

Thanks for the kind replies.

I do have access to Crude Manager and infact it works fine but where there is limited data available its a headache because you have to do an assay synthesis.

This RON correlation is widely used as i could remember in the first glance,anyone please provide the similar for pour point calculation (index).

May be if somebody likes to share his fine tuned correlations !!!

[Zauberberg]

You can check the methods given in Nelson's handbook (calculating Pour Point for mixtures) or, even better, try to develop your own based on the laboratory data that is available to you.

[kkala]

As Zauberberg says, Nelson's "Petroleum Refinery Engineering" (1958) can be useful for the case, although Cetane number correlations have not been found. For Pour point, viscosity, octane number of blends, look mainly at Chapter 4 - Evaluation of Oil Stocks ("refutas" for viscosity has not been found).

[ankur2061]

Himanshu,

I am providing an attachment which should provide you an insight of the basic definitions and correlations for crude assay and characterization.

Hope this helps.

Regards,
Ankur.

Attached Files

•  Basic_Definitions_and_Correlations.pdf   303.05KB   260 downloads

[Himanshu Sharma]

Thanks all for this effort !

I treat my Copy of Nelson as a professional 'Bible' and always look through it while having a problem did that this time too.

Still i am blasphemous, Correlations listed in Nelson are quiet old for now and are fine tuned or been replaced by others.Optimization software ASPEN-PIMS has an updated library called ABML that has variety of correlations,i want to know which all are been industrially accepted.(e.g Refutas is widely accepted for viscosity predictions)

[JMW]

I think the other possible calculation is the Wright equation for viscosity.
You might also look at ASTM D341 which provides methods for calculating the viscosity of blends.
It is becoming increasingly the practise to use feedback control for blending e.g. using density and viscosity sensors to regulate the blend . You may find some more information from Jiskoot.
http://www.jiskoot.c...d/59/UK/UK.html

[kkala]

Correlations listed in Nelson are quiet old for now and are fine tuned or been replaced by others.Optimization software ASPEN-PIMS has an updated library called ABML that has variety of correlations,i want to know which all are been industrially accepted.(e.g Refutas is widely accepted for viscosity predictions)

Well, this may be true for Nelson, yet does it affect an optimization study? However you may need more data.
A lot of data in Nelson's book is in diagrams, I had to express part of it algebraically to use in a spreadsheet. This is a disadvantage in our computer age.
But the patient and zeal of Nelson (and other authors of his time) in writing a book is badly needed nowadays.

Edited by kkala, 27 November 2010 - 09:43 AM.