Project memo - Inside Mines

INTEROFFICE MEMORANDUM
TO:
NEW ENGINEER
FROM:
I.M. ANOLDGUY
SUBJECT: ANALYSIS OF CRUDE COMPLEX – DESCRIPTON OF SIDE STRIPPERS CORRECTED
DATE:
NOVEMBER 17, 2014
We are looking to make a change to our crude unit feed in the near future. Your assignment is to
analyze the current crude unit operation and determine the impact of any proposed changes.
Depending on the magnitude of these changes we may need to make capital expenditures, so we
need to start planning as soon as possible.
The report describing the expected operational changes will be due to me no later than 6:00 PM
on Thursday, December 11, 2014. I expect a memo report consisting of:
 A one-page Executive Summary describing the problem and summarizing the results.
 An Appendix with any tables, charts, and descriptions of the assumptions made in the
simulations to support these results.
In addition, please turn in the following with your report:
 Any simulation files used to generate the values in your report (HYSYS files in HSC
format or Aspen Plus files in BKP format).
As mentioned you should start looking at this as soon as possible. I’m planning on a 3-week
vacation to Bora Bora right as your deadline is approaching. I will have no ability to answer
questions after December 6th. Please plan your time wisely.
EXISTING OPERATIONS
Q
W
DEC4
Q
LPGS
HX-DEC4
Q
S-NAP
Q
Q
NAPHTHA
Q
Q
Q
VACOVHD
KERO
VACCOL
Q
DIESEL
LVGO
Q
AGO
HVGO
MIX-VAC
SLOPWAX
ATMRESID
COILSTM
VACSTM
VACRESID
You have been using something similar to the existing crude oil operations as a sample problem
in your Petroleum Refining class. The preceding figure shows the arrangement of the crude oil
separation train: a crude preheat train leading to the Atmospheric Distillation Column with
Unstabilized Naphtha, Kerosene, Diesel, and Atmospheric Gas Oil (AGO) products; the
Atmospheric Resid is fed to the Vacuum Distillation Column with Light Vacuum Gas Oil
(LVGO), Heavy Vacuum Gas Oil (HVGO), Slop Wax, and Vacuum Resid products; the
Unstabilized Naphtha is fed to a Debutanizer with LPG & Stabilize Naphtha products.
The existing 101,000 bpd crude charge is made up of an equal mix of light, medium, & heavy
crude oils. The attached Tables 1, 2, & 3 give assay data for these oils.
The following table gives the important specifications on the products from these distillation
columns. Check these specifications carefully; they may be different than what you’ve set up
previously.
Column
Product
Quality Specification
Adjust
Atmospheric
Unstabilized Naphtha
410°F 95% D86 (dry, vol% basis)
Distillate Draw Rate
Kerosene
525°F 95% D86 (dry, vol% basis)
Kerosene Draw Rate
Diesel
645°F 95% D86 (dry, vol% basis)
Diesel Draw Rate
AGO
750°F 95% D86 (dry, vol% basis)
AGO Draw Rate
LVGO
915°F 95% TBP (dry, vol% basis)
LVGO Draw Rate
HVGO
1050°F 95% TBP (dry, vol% basis)
HVGO Draw Rate
Atmospheric Resid
Vacuum
Slop Wax
Vacuum Resid
Debutanizer
LPG
Stabilized Naphtha
The following tables give current operating parameters for these distillation columns. Note that
the available steam is at 150 psig & 500°F.
Operation
Type Operating Parameter
Operating Parameter
Crude Oil
Preheat
Crude Oil & Entrained Water
101,000 sbpd (dry)
500 bpd water
Outlet
450°F & 260 psig
2
Column
Type Operating Parameter
Operating Parameter
Atmospheric
Trays & Efficiencies
50 trays. Numbering from top:
Trays 1 to 6: 80%
Trays 7 to 10: 50%
Trays 11 to 16: 70%
Trays 17 to 30: 50%
Trays 31 to 39: 30%
Tray 40: 100%
Trays 41 to 50: 30%
Condenser
Total with water draw
Bubble point conditions for liquid; 130°F (est.)
Reboiler Type
No reboiler, steam feed to bottom stage
Distillate Rate
30,200 sbdp (est) (Unstabilized Naphtha)
Pressures
4 psig Condenser
12 psig Top Tray
22 psig Bottom Tray
Feed Stages
Preheated Crude Oil to Tray #40 (10 above
bottom, through furnace)
20,000 lb/hr steam to Tray #50 (bottom)
Feed Preheater
Feed Furnace, 635°F & 25 psig outlet
Kerosene Side Stripper
Liquid from Tray #10, vapor to Tray #6;
8,800 sbpd (est.)
Diesel Side Stripper
Liquid from Tray #20, vapor to Tray #16;
10,240 sbpd (est.)
Side Strippers
AGO Side Stripper
Liquid from Tray #30, vapor to Tray #26;
3,850 sbpd (est.)
Kerosene Pumparound
Draw from Tray #10, returned to Tray #7
25,000 bpd flow, 200°F return temperature
Diesel Pumparound
Draw from Tray #20, returned to Tray #17
15,000 bpd flow, 250°F return temperature
Pumparounds
AGO Pumparound
Draw from Tray #30, returned to Tray #27
10,000 bpd flow, 350°F return temperature
3
Column
Type Operating Parameter
Operating Parameter
Kerosene Side
Stripper
Trays & Efficiencies
10 @ 30% efficiency
Pressures
Feed Stages
Liquid from Atm Column Tray #10 to Top
2,500 lb/hr steam to Bottom Tray
Column
Type Operating Parameter
Operating Parameter
Diesel Side
Stripper
Trays & Efficiencies
10 @ 30% efficiency
Pressures
Feed Stages
Liquid from Atm Column Tray #20 to Top
2,500 lb/hr steam to Bottom Tray
Column
Type Operating Parameter
Operating Parameter
AGO Side
Stripper
Trays & Efficiencies
10 @ 30% efficiency
Pressures
Liquid from Atm Column Tray #30 to Top
2,500 lb/hr steam to Bottom Tray
Feed Stages
Column
Type Operating Parameter
Operating Parameter
Debutanizer
Trays & Efficiencies
45 @ 80% efficiency
Condenser
Total condenser with water draw
1.5 reflux ratio
Reboiler
Kettle reboiler
Distillate Rate
5,500 sbdp (LPG)
Pressures
150 psig Condenser
150 psig Top Tray
160 psig Bottom Tray
160 psig Reboiler
Feed Trays
Unstabilized Naphtha to Tray #22
Naphtha pressurized to 250 psig & preheated to
250°F
Liquid Draws
None
Side Strippers
None
Pumparounds
None
4
Column
Type Operating Parameter
Operating Parameter
Vacuum
Trays & Efficiencies
14 “trays”. Numbering from top:
Tray 1: 100%
Trays 2 to 11: 50%
Tray 12: 100%
Trays 13 to 14: 30%
Condenser Type
None, LVGO pumparound liquid return to top
Reboiler Type
No reboiler, steam feed to bottom stage
Pressures
50 mmHg Top
62 mmHg Bottom Stage
Feed Stages
Atm Resid from Heater to Tray #12
20,000 lb/hr steam to Tray #14 (bottom)
Feed Preheater
Feed Furnace, 780°F & 180 mmHg outlet
20,000 lb/hr vac coil steam added upstream
Liquid Draws
LVGO from Tray #4; 5,000 bpd (est.)
HVGO from Tray #8; 21,000 bpd (est.)
Slop Wax from Tray #11; 1,000 bpd
LVGO Pumparound
Draw from Tray #4, returned to Tray #1
22,300 bpd flow, outlet temperature adjusted to
control top temperature of tower to 180°F; (85°F
return, 40 MMBtu/hr cooling est.)
Pumparounds
HVGO Pumparound
Draw from Tray #8, returned to Tray #5
50,000 bpd flow, 150°F cooling (400°F return, 40
MMBtu/hr cooling est.)
ANALYSIS OF EXISTING OPERATIONS
We would like to determine the current operations as determined from these operating
conditions. Please use the following table as a guideline for tabulating the results:
Stream
Rate
[bpd dry]
API
Gravity
Sulfur Content
[wt%]
LPG
Stabilized Naphtha
Unstabilized Naphtha
Kerosene
Diesel
AGO
LVGO
HVGO
Vacuum Resid
Vacuum Tower Overhead




























5
T5
[°F]
TBP
TBP
TBP
TBP
TBP
TBP
T95
[°F]
D86 & TBP
D86 & TBP
D86 & TBP
D86 & TBP
D86 & TBP
TBP
TBP
In addition I’d like the calculated cut points using the T5 & T95 TBP values for the following
adjacent streams: Unstabilized Naphtha/Kerosene, Kerosene/Diesel, Diesel/AGO, AGO/LVGO,
LVGO/HVGO, & HVGO/Vac Resid.
Finally, calculate the following carryover of certain boiling point material:
 C5+ into the LPG steam.
 1050°F+ into the HVGO & lighter streams
 1050°F- into the Vacuum Resid
MODIFIED OPERATIONS
Once you have the base case we’d like to examine the following changes to the operating
scenarios starting each time with the Base Case:
1. Change the Diesel spec. The spec applied in the base case may result in a diesel stream
that does not make spec. Apply a new spec of 640°F to the 90% volume (D86 basis).
 What is the new cut point between the Diesel/AGO streams?
 What is the change in rates between the Kerosene, Diesel, & AGO streams?
2. Reduce the overhead losses in the Vacuum Column. We’d like to reduce the overhead
losses of hydrocarbons from the Vacuum Tower. Let’s try two ways to do this:
 Increase the LVGO pumparound rate by 50% but keep the same top
temperature.
 Decrease the top temperature to 170°F but keep the same pumparound rate.
Compare the overhead losses. Has either scenario reduced the losses?
3. Reduce the C5+ losses into the LPG stream. We’d like to reduce the C5+ losses in the
Debutanizer to half that of the base case. Let’s try two ways to do this:
 Increase the reflux ratio.
 Decrease the distillate draw ratio.
In either case do not let the C4- content of the Stabilized Naphtha get above 0.1 vol%
(dry basis). Compare the condenser & reboiler duties for the three cases (base & the two
alternates).
6
Table 1. Assay Data Light Crude
TBP Cumulative Yield
Wt% @
°F @ IBP
°F @ EP
IBP
Whole Crude
31
160
0
160
236
5
236
347
10
347
446
20
446
545
30
545
649
40
649
758
50
758
876
60
876
1015
70
1015
1205
80
1205
1350
90
1350
FBP
95
@ Mid
2.5
7.5
15
25
35
45
55
65
75
85
92.5
97.5
Properties
API
Wt%
Gravity
Sulfur
34.17
1.77
74.91
0.019
62.90
0.031
51.09
0.060
43.38
0.379
36.97
1.064
31.37
1.698
25.96
2.159
20.86
2.554
15.45
3.041
8.94
3.838
4.44
4.503
-6.57
6.382
Light Ends Analysis
Ethane
Propane
i-Butane
n-Butane
i-Pentane
n-Pentane
Wt%
0.000
0.146
0.127
0.702
0.654
1.297
Table 2. Assay Data Medium Crude
TBP Cumulative Yield
Wt% @
°F @ IBP
°F @ EP
IBP
Whole Crude
88
180
0
180
267
5
267
395
10
395
504
20
504
611
30
611
721
40
721
840
50
840
974
60
974
1131
70
1131
1328
80
1328
1461
90
1461
FBP
95
@ Mid
2.5
7.5
15
25
35
45
55
65
75
85
92.5
97.5
Properties
API
Wt%
Gravity
Sulfur
28.97
2.83
71.51
0.022
55.69
0.062
47.08
0.297
38.78
1.010
31.67
2.084
26.36
2.777
21.36
3.284
16.15
3.857
10.15
4.706
2.74
5.967
-1.87
6.865
-11.08
8.859
7
Light Ends Analysis
Wt%
Ethane
Propane
i-Butane
n-Butane
i-Pentane
n-Pentane
0.000
0.030
0.089
0.216
0.403
0.876
Table 3. Assay Data Heavy Crude
TBP Cumulative Yield
Properties
Wt% @
API
Wt%
°F @ IBP
°F @ EP
IBP
@ Mid
Gravity
Sulfur
Whole Crude
28.36
2.8
26.8
153.6
0
2.5
74.11
0.005
153.6
255.1
5
7.5
61.40
0.041
255.1
400.5
10
15
46.98
0.341
400.5
523.4
20
25
37.47
1.076
523.4
645
30
35
30.47
1.898
645
769.6
40
45
24.36
2.557
769.6
901.9
50
55
18.65
3.185
901.9
1043.8
60
65
12.95
3.916
1043.8
1198.1
70
75
7.24
4.826
1198.1
1380.5
80
85
0.94
5.990
1380.5
1499.7
90
92.5
-3.07
6.775
1499.7
FBP
95
97.5
-10.78
8.432
8
Light Ends Analysis
Ethane
Propane
i-Butane
n-Butane
i-Pentane
n-Pentane
Wt%
0.039
0.284
0.216
0.637
0.696
1.245

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