Department of Chemical Engineering, Iitd

PETROLEUM REFINERY ENGINEERING (CHL 794)

DEPARTMENT OF CHEMICAL ENGINEERING, IITD

TUTORIAL SHEET -5

A petroleum cut has the following ASTM D86 distillation data:

Volume% / 0 / 10 / 30 / 50 / 70 / 90 / 95
Temperature(deg.C) / 36.5 / 54 / 77 / 101.5 / 131 / 171 / 186.5

Table 1.1 gives the a and b constants in the interconversion equation (TBP = a(ASTM D86)b) referred to in the API method and table 1.2 gives the constants for Daubert’s distillation curves(∆Tiꞌ = Ai ((∆Ti)Bi) where T and Tꞌ stand for ASTM D86 and TBP temperatures respectively, both in deg.F.Convert these data to TBP data using the API method of Riazi and Daubert and Daubert’s method. Plot the results and compare.

Table 1.1. Constants for the equation of the API method

Volume % distilled / a / b
0 / 0.9167 / 1.0019
10 / 0.5277 / 1.0900
30 / 0.7429 / 1.0425
50 / 0.8920 / 1.0176
70 / 0.8705 / 1.0226
90 / 0.9490 / 1.0110
95 / 0.8008 / 1.0355

Table 1.2 Constants for Daubert’s distillation curves for interconversion

Index number i / Ai / Bi
1 / 7.4012 / 0.6024
2 / 4.9004 / 0.7164
3 / 3.0305 / 0.8008
4 / 0.8718 / 1.0258
5 / 2.5282 / 0.8200
6 / 3.0419 / 0.7750
7 / 0.1180 / 1.6606

Also, calculate the MeABP of the petroleum fraction. If the API gravity of this fraction is 62, calculate the Watson’s characterization factor. Also, divide the TBP curve of the petroleum cut as calculated from API method into pseudo-components. Calculate the liquid volume percentage of each pseudo-component.

Consider the Kuwait export crude with the following TBP-vol% data:

Table 2.1: TBP-vol%

volume % / TBP(0C)
5 / 40
10 / 85
30 / 215
50 / 340
70 / 495

Determine the volumetric yield, average boiling point, molecular weight and specific gravity for the products shown in the table 2 below.

Table 2.2: Typical CDU products and their end boiling points

Cut # / Product / End point (0C)
1 / Off gas / 10
2 / Light straight run naphtha / 70
3 / Naphtha / 180
4 / Kerosene / 240
5 / Light diesel / 290
6 / Heavy diesel / 340
7 / Atm. Gas oil / 370
8 / Vacuum gas oil / 390
9 / Vac. distillate / 550
10 / Vac. residue / -

For the Kuwait export crude (API 31.5) given in the above problem. Perform a material balance for a CDU using HYSYS for 100,000 BPCD of 29 API crude with the following assay.

Table 3.1 Crude Assay

volume % / TBP(0C)
0 / -9.44
4.5 / 32.22
9 / 73.89
14.5 / 115.56
20 / 154.44
30 / 223.89
40 / 273.33
50 / 326.67
60 / 393.33
70 / 473.89
76 / 520.56
80 / 546.11

The crude is fed to a pre-flash separator operating at 4500 F and 75 psia. The vapour from this separator bypasses the crude furnace and is remixed with the hot (6500F) liquid leaving the furnace. The combined stream is then fed to the distillation column. The column operates with a total condenser, three side strippers and three pump around.

4. With 100000 BPD of the following crude (API=36), Estimate the products of the atmospheric distillation column. If the atmospheric residue of the crude is taken at 650+0F.It enters in a vacuum distillation tower to give three products: light vacuum gas oil (650 to 8500F), heavy vacuum gas oil(850-10500F) and vacuum residue (1050+0F).Calculate the mass flow rate of these products. Then, calculate the sulphur content (lb/hr) for each product.

ASTM D86(0F) / vol% / cum vol% / SG
86 / 0 / 0 / __
122 / 0.5 / 0.5 / 0.67
167 / 1.2 / 1.7 / 0.675
212 / 1.6 / 3.3 / 0.722
257 / 2.7 / 6 / 0.748
302 / 3.1 / 9.1 / 0.765
347 / 3.9 / 13 / 0.778
392 / 4.7 / 17.7 / 0.789
437 / 5.7 / 23.4 / 0.801
482 / 8 / 31.4 / 0.814
527 / 10.7 / 42.1 / 0.825
584 / 5 / 47.1 / 0.845
636 / 10 / 57.1 / 0.854
689 / 7.8 / 64.9 / 0.863
742 / 7 / 71.9 / 0.864
794 / 6.5 / 78.4 / 0.889
__ / 20.8 / 99.2 / 0.931