Hydrocarbon Processing - May 2021 - 20
Maintenance and Reliability
To stack
PI1
findings are indications that slop products produced from the
cracking units may have caused foulants on the trays and, therefore, an increase in the pressure drop. Another reason for the
fouling might be asphaltene precipitation. Light opportunity
crudes are blended with heavy opportunity crudes, making the
processed blend prone to asphaltene precipitation, which can
lead to fouling on trays.
Preparation and application. The aim was to minimize down-
time for the CDU with the highest crude processing. The maintenance history of the preflash column shows that the mechanical
cleaning takes at least 10 d, with many hours needed for blinding,
access opening, cleaning, steam-out, etc. The heated cutter stock
circulation was considered for removing and dissolving foulants
on the tray and for minimizing the downtime of the unit. Lightcycle gasoil, a product of fluid catalytic cracking unit (FCCU),
was used as cutter stock because of its solvent properties.
Air cooler
19,000
0.33
Flare
Cooling
water
Feed to
preflash
Preflash
reboiler furnace
O/H reflux
drum
0.28
17,000
0.23
16,000
To
debutanizer
PI2
Preflash
column
Reboiler
furnace pump
18,000
Offgas
Crude oil feed flow, m3/d
Crude
feed
Crude oil feed flow
Shutdown
0.18
15,000
Preflash column pressure drop
14,000
O/H reflux Debutanizer
pump
feed pump
New
pipeline
Fuel oil
Main column
furnace pump
0.08
13,000
To furnace
Heat
exchangers
0.13
Preflash column pressure drop, kg/cm2
high amounts of naphtha did not cause a high pressure drop in
the column, contrary to what had been experienced before. FIG.
1 represents the relation between pressure drop along the column and debutaniser feed volume.
In June 2019, when the incident occurred for the first time, a
high amount of slop (6% of the feed rate) was processed, including cracked products formed during the startup of the cracking
units, which had undergone a turnaround the previous month.
The slop included coker products, especially coker naphtha,
which may have been responsible for the rapid fouling in the
preflash column due to its molecular structure. The amount of
slop processed and the change in pressure drop through the preflash column are shown in FIG. 2.
In a similar way, the increase in the pressure drop through
the column had been observed after processing the slop products formed by the cracking units in 2015 and 2017. All these
0.03
12,000
12/5/2019
12/10/2019
12/15/2019
12/20/2019
12/25/2019
FIG. 5. Pressure drop of preflash column vs. crude oil feed flow before
and after cleaning.
FIG. 3. Preflash column process flow diagram.
3,000
0.33
Before and after the cleaning
0.28
Debutanizer feed flow, m3/d
2,600
Debutanizer feed flow
0.23
2,400
2,200
0.18
Shutdown
2,000
Preflash column pressure drop
0.13
1,800
Preflash column pressure drop, kg/cm2
2,800
0.08
1,600
1,400
12/5/2019
12/10/2019
12/15/2019
12/20/2019
0.03
12/25/2019
FIG. 6. Pressure drop of preflash column vs. debutanizer feed flow
before and after cleaning.
FIG. 4. Clean and dirty cutter stock samples after four circulations.
TABLE 1. Cutter stock sample results
Tests
Clean cutter ctock
First circulation
Second circulation
Third circulation
Fourth circulation
Asphaltenes, % m/m
0
0.12
0.041
0.033
0.01
Carbon residue, % m/m
0
0.42
0.12
0.48
0.02
API
24.4
25.5
24.8
28.1
32.9
Viscosity, mm2/s
1.597
1.785
1.627
1.697
1.822
20
MAY 2021 | HydrocarbonProcessing.com
http://www.HydrocarbonProcessing.com
Hydrocarbon Processing - May 2021
Table of Contents for the Digital Edition of Hydrocarbon Processing - May 2021
Contents
Hydrocarbon Processing - May 2021 - Intro
Hydrocarbon Processing - May 2021 - Cover1
Hydrocarbon Processing - May 2021 - Cover2
Hydrocarbon Processing - May 2021 - Contents
Hydrocarbon Processing - May 2021 - 4
Hydrocarbon Processing - May 2021 - 5
Hydrocarbon Processing - May 2021 - 6
Hydrocarbon Processing - May 2021 - 7
Hydrocarbon Processing - May 2021 - 8
Hydrocarbon Processing - May 2021 - 9
Hydrocarbon Processing - May 2021 - 10
Hydrocarbon Processing - May 2021 - 11
Hydrocarbon Processing - May 2021 - 12
Hydrocarbon Processing - May 2021 - 13
Hydrocarbon Processing - May 2021 - 14
Hydrocarbon Processing - May 2021 - 15
Hydrocarbon Processing - May 2021 - 16
Hydrocarbon Processing - May 2021 - 17
Hydrocarbon Processing - May 2021 - 18
Hydrocarbon Processing - May 2021 - 19
Hydrocarbon Processing - May 2021 - 20
Hydrocarbon Processing - May 2021 - 21
Hydrocarbon Processing - May 2021 - 22
Hydrocarbon Processing - May 2021 - 23
Hydrocarbon Processing - May 2021 - 24
Hydrocarbon Processing - May 2021 - 25
Hydrocarbon Processing - May 2021 - 26
Hydrocarbon Processing - May 2021 - 27
Hydrocarbon Processing - May 2021 - 28
Hydrocarbon Processing - May 2021 - 29
Hydrocarbon Processing - May 2021 - 30
Hydrocarbon Processing - May 2021 - 31
Hydrocarbon Processing - May 2021 - 32
Hydrocarbon Processing - May 2021 - 33
Hydrocarbon Processing - May 2021 - 34
Hydrocarbon Processing - May 2021 - 35
Hydrocarbon Processing - May 2021 - 36
Hydrocarbon Processing - May 2021 - 37
Hydrocarbon Processing - May 2021 - 38
Hydrocarbon Processing - May 2021 - 39
Hydrocarbon Processing - May 2021 - 40
Hydrocarbon Processing - May 2021 - 41
Hydrocarbon Processing - May 2021 - 42
Hydrocarbon Processing - May 2021 - 43
Hydrocarbon Processing - May 2021 - 44
Hydrocarbon Processing - May 2021 - 45
Hydrocarbon Processing - May 2021 - 46
Hydrocarbon Processing - May 2021 - 47
Hydrocarbon Processing - May 2021 - 48
Hydrocarbon Processing - May 2021 - 49
Hydrocarbon Processing - May 2021 - 50
Hydrocarbon Processing - May 2021 - 51
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Hydrocarbon Processing - May 2021 - 53
Hydrocarbon Processing - May 2021 - 54
Hydrocarbon Processing - May 2021 - 55
Hydrocarbon Processing - May 2021 - 56
Hydrocarbon Processing - May 2021 - 57
Hydrocarbon Processing - May 2021 - 58
Hydrocarbon Processing - May 2021 - 59
Hydrocarbon Processing - May 2021 - 60
Hydrocarbon Processing - May 2021 - 61
Hydrocarbon Processing - May 2021 - 62
Hydrocarbon Processing - May 2021 - 63
Hydrocarbon Processing - May 2021 - 64
Hydrocarbon Processing - May 2021 - 65
Hydrocarbon Processing - May 2021 - 66
Hydrocarbon Processing - May 2021 - 67
Hydrocarbon Processing - May 2021 - 68
Hydrocarbon Processing - May 2021 - 69
Hydrocarbon Processing - May 2021 - 70
Hydrocarbon Processing - May 2021 - 71
Hydrocarbon Processing - May 2021 - 72
Hydrocarbon Processing - May 2021 - 73
Hydrocarbon Processing - May 2021 - 74
Hydrocarbon Processing - May 2021 - 75
Hydrocarbon Processing - May 2021 - 76
Hydrocarbon Processing - May 2021 - 77
Hydrocarbon Processing - May 2021 - 78
Hydrocarbon Processing - May 2021 - 79
Hydrocarbon Processing - May 2021 - 80
Hydrocarbon Processing - May 2021 - 81
Hydrocarbon Processing - May 2021 - 82
Hydrocarbon Processing - May 2021 - 83
Hydrocarbon Processing - May 2021 - 84
Hydrocarbon Processing - May 2021 - 85
Hydrocarbon Processing - May 2021 - 86
Hydrocarbon Processing - May 2021 - 87
Hydrocarbon Processing - May 2021 - 88
Hydrocarbon Processing - May 2021 - 89
Hydrocarbon Processing - May 2021 - 90
Hydrocarbon Processing - May 2021 - Cover3
Hydrocarbon Processing - May 2021 - Cover4
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https://www.nxtbook.com/nxtbooks/gulfpub/refining_processes_handbook_2020
https://www.nxtbook.com/nxtbooks/gulfpub/refining_processes_handbook_2020_v2
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https://www.nxtbook.com/nxtbooks/gulfpub/hp_201912
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201911
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2020_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2020
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201910
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https://www.nxtbook.com/nxtbooks/gulfpub/hp_201902
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201901
https://www.nxtbook.com/nxtbooks/gulfpub/petrochemical_2018_v2
https://www.nxtbook.com/nxtbooks/gulfpub/petrochemical_2018
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201812
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2019_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2019
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201811
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