Evaluation of properties of crude oil and its fractions. · General Procedure for evaluation of...

$: Evaluation of properties of crude oil and its fractions. · General Procedure for evaluation of crude oil/ fractions 1. From the crude distillation data ... Mean Average Boiling Point$
2/16/2015 NPTEL :: Chemical Engineering Petroleum Refinery Engineering

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Evaluation of properties of crude oil and its fractions. General Procedure for evaluation of crude oil/ fractions1. From the crude distillation data,plot TBP and gravity midpercent curves.2. Select TBP cutpoints of products to be made from atmospheric and vacuum pipe stills.3. From TBP and gravity curves, determine percentages and gravities of fractions.4. Convert volumes percent to weight percents.5. Determine weight of bottoms stream by difference.If the volume of bottom stream is taken

from the TBP curve, then gravity is calculated from weight and volume.6. For crude oils containing significant amounts of sulfur or nitrogen, it is also necessary to make

sulfur and/or nitrogen balances around each unit.

Example: Whole crude TBP Data (API Gravity 36.3)

Table:2.2 Plot TBP, M.W , API AND Wt% CURVES FOR THE CRUDE oil

Volume percent 5 10 20 30 40 50 60

TBP Temperature (oF) 62 144 255 344 437 531 623

Volume percent 70 80 85

TBP Temperature (oF) 717 819 897

CALCULATIONS SP.Gr.For whole crude = 141.5/ (131.5+ API)Sp. Gr. = 0.84 (for the crude oil)VABP for whole crude = (t20+t50 + t 80)/3

==>VABP =[ ( 255+ 531+819)/3 ]= 535 oFTBP Slope =[ (t70 t10)/ 60 ]

= (717144)/60

= [9.6 oF/%]

Correction Factor (from graph ) = 70 oFMean Average Boiling Point ( MABP) = 535 70 = 465 oFCharacterisation Factor Kw = 11.5 (Assumed constant) (From graph)Divide whole crude into various cuts

Basis :100 Barrel of crude oil ( 1bbl= 42 US gallon, 1 US Gallon= 3.78 L)

Basis 100 Barrel of crude oil( Weight of the crude = 100x0.843x 349.7=29500 Lb)

(density of water = 349.7 lb/bbl)

Table:2.3[1,2]

Boiling range(F)

Cumulativevol.%

VABP(F) MABP(F) API M.W Mid

vol%



IBP200 15 110 110 65 78 7.5

200300 25 251 251 15 112 20

300400 46.5 482 482 35 186 41.0

Calculation for weight percent

Table:2.4[1,2]

Vol.%cuts API Sp.Gr Density(lb/bbl) weight Wt.% of

cutsCumulativewt.%

15 65 0.72 251.7 3770 12.8 12.8

1525 51 0.78 272.7 2727 9.2 22.0

2535.5 44 0.81 283.2 2973 10.1 32.8

wt.%,calculated based on total mass of crude (29500 lb)[1,2]



Fig:2.18 wt.%,calculated based on total mass of crude (29500 lb)[1,2]

Exercise

Complete the Table for other fractions (cuts).Plot API vs mid volume, Molecular weight vs MID Volume and weight percent vs mid volume forthese cuts.Calculate 50% ASTM and 50%EFV Boiling temperatures for each fraction and plot. Draw astmand EFV curves for the crude.

Fig:2.19

Crude Oil Assay Example1



Table:2.5

Table:2.6



Table:2.7



50% Boiling Point on ASTM curve :can be calculated from the slope of TBP curve of acrude and its 50% B.P can be estimated

Fig:2.20

Fig:2.21 Different Slope and Interconversion

Table:2.8



Fig:2.22



Fig:2.23

Linearized Distillation Yield Curves


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Fig:2.24 Linearized Distillation Yield Curves

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