Design Slides Final

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    CRUDE DISTILLATION UNIT

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    INTRODUCTION

    Crude distillation unit involves complex stream interactions

    with various sections of the main column that is

    supplemented with secondary columns.

    A simple block diagram is as shown :

    2

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    Designations (Help file)

    Box with a green background designates the derived data

    Box with a blue background designates the calculated data

    Box with a red background designates the final data

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    Problem 1 :

    For the Ecudaor crude stream whose TBP, sulfur

    and API assay are presented below, determine theTBP of the products emanating from the CDU unit

    using the concept of ASTM gaps.

    4

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    5

    Cumulative volume

    %

    TBP oF oAPI Sulfur content (wt

    %)

    0 -30

    1 30

    1.5 602 90 100 0.035

    3 120 85 0.035

    4 150 80 0.04

    6.5 180 72 0.04

    9 210 64 0.045

    11.5 240 60 0.045

    14 270 55 0.05

    17.5 310 50 0.055

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    6

    19 330 48 0.06

    21 350 46 0.07

    22.5 370 45 0.08

    24.5 390 43 0.10

    26 410 42 0.1228 430 41 0.16

    30 450 40 0.19

    32 470 38 0.25

    34 490 37 0.3

    36 520 36 0.36

    38.5 540 34 0.43

    39.5 560 33 0.48

    42.5 580 32 0.57

    44.5 600 31 0.63

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    7

    47 620 30 0.71

    49 640 29.5 0.77

    52 660 29 0.80

    55 680 28 0.85

    57 700 27 0.8759 720 26.5 0.89

    61 740 26 0.91

    62.5 760 25.5 0.93

    63.8 780 25 0.96

    64.5 24.5 0.98

    66 24 1.02

    68 23.5 1.06

    70 23 1.14

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    Assume the following cut range of the products on the

    crude TBP

    Naphtha: -30 to 310 oF Kerosene: 310 to 475 oF

    LGO: 475 to 585 oF

    HGO: 585 to 680o

    F

    8

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    Solution 1

    Naphtha product ASTM & TBP Data

    Firstly, we evaluate the TBP data of Naphtha cut. For

    this we use end point correlation and TBP 50 % of theNaphtha cut to obtain ASTM 50 % and ASTM 100 %

    data. Using these two data points and using end point

    correlation, the ASTM data of naphtha cut is obtained.

    Once again using Edmister correlation we obtain theASTM of the naphtha product. The hierarchy of these

    steps along with obtained data are presented as follows.

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    TBP data of naphtha cut

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    Cumulative volume % Differential volume % TBP oF

    0 0 -30

    1 5.714 301.5 8.571 60

    2 11.428 90

    3 17.143 120

    4 22.857 150

    6.5 37.142 1809 51.428 210

    11.5 65.714 240

    14 80 270

    17.5 100 310

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    11

    TBP 50 % of the Naphtha cut on the crude assay = 208 oF.

    From Edmister correlation, ASTM 50 % = 215 oF

    Naphtha cut end point = 310 oF. From end point correlation,ASTM end point = 310 1 = 309 oF

    From Probability chart and Edmister correlation, the naphtha

    product ASTM and TBP are obtained as follows:

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    12

    Cumulative volume % TBP oF

    0 15210 178

    30 198

    50 215

    70 230

    90 255

    100 309

    ASTM data of Naphtha

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    Product TBP (from Edmister correlation)

    Vol % DTASTM(0F) DTTBP (

    0F) TTBP(0F)

    0 26 49 92

    10 20 37 141

    30 17 30 178

    50 NR NR 208

    70 15 24 239

    90 25 34 273

    100 54 60 333

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    Kerosene product TBP & ASTM data

    ASTM gap of naphthakerosene = 25 oF

    From ASTM data of Naphtha product, ASTM 95 % of

    naphtha = 295 oF

    Therefore, ASTM 5 % of kerosene = 295 + 25 = 320 oF

    Kerosene product end point on the crude = 385 oF. Forthis value from end point correlation, ASTM end point of

    kerosene cut = 456 oF

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    15

    Vol % TASTM(0F)

    0 305

    10 330

    30 350

    50 367

    70 380

    90 405

    100 456

    From Probability chart and Edmister correlation, the kerosene

    product ASTM and TBP are obtained as follows:

    ASTM data of kerosene product

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    16

    Vol % DTASTM(0F) DTTBP (

    0F) TTBP(0F)

    0 25 48 249

    10 20 38 297

    30 17 30 335

    50 13 NR 36570 13 22 387

    90 25 34 421

    100 51.5 57 478

    Kerosene product TBP

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    LGO product TBP & ASTM data

    ASTM gap of keroseneLGO = -10 oF

    From ASTM data of Kerosene product, ASTM 95 % ofKerosene = 445 oF

    Therefore, ASTM 5 % of LGO = 44510 = 435 oF

    LGO product end point on the crude = 585

    o

    F. For thisvalue from end point correlation, ASTM end point of

    LGO product = 58510 = 575 oF.

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    Vol % TASTM(0F)

    0 45810 480

    30 492

    50 505

    70 520

    90 545

    100 575

    ASTM data of LGO (from Probability chart)

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    Vol % DTASTM

    (0F)

    DTTBP

    (0F)

    TTBP(0F)

    0 22 44 407

    10 12 25 451

    30 13 24 476

    50 NR NR 500

    70 15 24 52490 25 34 558

    100 30 34 592

    TBP data of LGO product (from Edmister correlation)

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    HGO product TBP & ASTM data ASTM gap between LGO and HGO products = -35 oF

    From LGO ASTM data, ASTM 95 % of LGO product = 573 oF

    Therefore, ASTM 5 % of the HGO product = 57335 = 538 oF.

    TBP end point of HGO on crude assay = 680 oF. 90% TBP point of HGO on

    the crude assay = 670 oF

    Using the 90% correlation available in the end point correlation data, 90%

    ASTM point = 627 oF.

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    21

    Vol % TASTM(0F)

    0 52210 552

    30 571

    50 575

    70 600

    90 627

    100 675

    From probability chart, HGO product ASTM data is

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    From Edmister correlation, the HGO product TBP is

    Vol % DTASTM

    (0F)

    DTTBP

    (0F)

    TTBP(0F)

    0 29 55 466

    10 19 37 521

    30 4 8 558

    50 - - 566

    70 25 38 60490 27 37 642

    100 48 53 695

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    Problem 2

    Using the product TBPs estimated in Q1, determine the

    average product properties (including residue product)

    such as API, molecular weight, characterization factor.

    Appropriate pseudo-component selection could be made

    on the TBP and API assay of the crude.

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    Solution 2

    For the crude, the following pseudo-component range

    along with mid vol, average API for each pseudo-

    component are summarized based on the TBP and APIassay of the crude oil. Sulfur calculations are ignored in

    this section, as sulfur balance is not going to affect design

    calculations associated to the CDU.

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    Psuedo-

    component

    No.

    TBP range

    on crude

    (oF)

    Mid Boiling

    point on

    crude oF

    Mid vol % on

    crude

    Mid oAPI

    1 60 100 75 2.25 90

    2 100

    140 125 3.25 813 140 180 160 5.25 71

    4 180 220 195 8.25 64

    5 220 250 235 11 58

    6 250 280 265 13.5 53

    7 280 310 295 16.25 52

    8 310 330 320 18.5 52

    9 330 350 340 20.5 46

    10 350 370 360 22.5 45

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    11 370 390 380 24.5 42

    12 390 410 400 26.5 41

    13 410 430 420 28.5 40

    14 430 450 440 30.5 39

    15 450 480 470 32.5 3716 480 -500 490 34.5 37

    17 500 520 510 36.5 36

    18 520 540 530 38.5 34

    19 540 560 550 40.5 33

    20 560 610 595 44 32

    21 610 630 620 47.5 31

    22 630 650 640 49.5 30

    23 650 670 660 51.5 29

    24 670

    700 685 54 27.5

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    Based on product TBPs evaluated previously, the

    corresponding volume % of various pseudo-components

    in product TBPs is obtained graphically. The same is

    summarized in the next table.

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    Psuedo-

    component

    No.

    Naphtha product

    differential vol %

    Kerosene

    product

    differential vol%

    LGO product

    differential

    vol %

    HGO product

    differential vol

    %

    1 1.8

    2 7.2

    3 20

    4 28

    5 19

    6 15 5.5

    7 3 10

    8 3 11

    9 13

    10 14.5

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    29

    11 18

    12 13

    13 7 3

    14 4 5

    15 4 24

    16 17 5

    17 17 4.8

    18 13 8.3

    19 10 14.4

    20 10 40.5

    21 12

    22 7.1

    23 3.9

    24 4

    Total 97* 100 100 100

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    *For the very first comp