Distillation Column Flooding Predictor Texas Technology Showcase Galveston, Texas 2006 George E. Dzyacky 2ndpoint LLC
Developer George E. Dzyacky (da ZA key) Background in Refining Operations 28 years Petroleum Refining –FCC and Vapor Recovery Received Amoco Whiting Refinery highest recognition award three times for advanced process control innovations, totaling $6.8MM (US) /year Patent holder Twice awarded U. S. Department of Energy grant on Flooding Predictor Copyright 2006 2ndpoint, LLC
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Technology description Flooding Predictor was developed as a diagnostic tool to predict and avoid chronic flooding in FCC absorber columns –evolved into A/C strategy Exploits patterns of behavior that column variables undergo as liquid begins to hold-up Highly repeatable patterns were discovered to precede flooding events When pre-flood conditions are detected, the strategy generates a warning of impending flood or a discrete output to temporarily reduce operating severity 98%-plus accuracy increased confidence in the methodology and Flooding Predictor evolved from “ advisory”to “ closed-loop”application The Flooding Predictor integrates with Multivariable Predictive Control (MPC) or can be commissioned as a stand-alone application
Copyright 2006 2ndpoint, LLC
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Technology benefits Inexpensive software alternative for diagnosing flooding problems and increasing column throughput by 3 - 7% Estimated ROI for original Amoco project in 2006 dollars; $10,000,000/year for $80,000 investment –100% payback in 3 days Virtually eliminates flooding events and the negative consequences associated with them: Throughput reduction Environmental excursions Equipment damage Risk to personal safety Increase energy efficiency Low installation and maintenance costs
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Technology basis Flooding Predictor recognizes unique patterns of behavior among process variables as the column approaches flood Patterns are based on derivative values (rate of change) of column variables: reboiler temperature, levels, flows, delta temperature, and delta pressure Variables are chosen based on observation and analysis of their derivative values as the column approaches and enters flood When enabled, the Flooding Predictor compares current derivative values against critical derivative limits identified during step-tests When the critical limits are met, the Flooding Predictor warns of imminent flood or in closed-loop form momentarily reduces column operating severity by a predetermined value Copyright 2006 2ndpoint, LLC
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Pre-flood patterns Comprised of changes in column variables, which occur well within normal alarm limits.
Temporary change in Overhead Flow 40 MSQFD 0 MSQFD 1 Hr.
0 Hr.
Temporary change in Delta Pressure 100 psig 0 psig 1 Hr.
0 Hr.
Temporary change in Bottom Temperature 400 deg 0 deg 1 Hr.
0 Hr.
Temporary change in Level or Bottom Flow 100% 0% 1 Hr.
0 Hr.
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Pre-flood pattern identification Temporary change in Overhead Flow
Changes are subtle, transient and simultaneous
40 MSQFD 0 MSQFD
Changes in raw variables are virtually indistinguishable from normal process noise
1 Hr.
0 Hr.
Temporary change in Delta Pressure 100 psig
Pre-flood patterns are well within normal alarm limits Individual derivatives exceed their critical values frequently Simultaneous behavior present only at pre-flood conditions Pre-flood patterns occur up to 60 minutes in advance of flood event
0 psig 1 Hr.
0 Hr.
Temporary change in Bottom Temperature 400 deg 0 deg 1 Hr.
0 Hr.
Temporary change in Level or Bottom Flow 100% 0% 1 Hr.
0 Hr.
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Motiva commercial demonstration Motiva Enterprise Inc., Norco, Louisiana
Actual test data of flood prediction on Motiva depropanizer; Norco, Louisiana USA
Copyright 2006 2ndpoint, LLC
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Pre-flood modeling 400 deg
100 psig
Temporary increase in Delta Pressure,
0 psig 1 Hr.
0 Hr.
1 Hr.
0 Hr.
400 deg
0 deg 1 Hr.
Change in engineering units/time, i.e., 0.56 degrees F/minute
0 Hr.
Temporary increase in Bottom Temp.
0 deg
100%
Temporary decrease in Level or Flow,
0% 1 Hr.
0 Hr.
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Original closed-loop applications
FCC Vapor recovery
Feed Target Feed Rate
Effect of flooding events on unit throughput
Effect of eliminating flooding and operating column at or near its hydraulic limit
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Why is this technique beneficial? Shifts control objective from conventional delta-pressure to the true hydraulic limit
Hydraulic limit
Column dP
Capacity
Upper dP limit
6%+ capacity increase proven in research at the University of Texas at Austin
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University of Texas finite reflux test DISTILLATION COLUMN 18" TRAY SPACING
Conventional distillation column operated at finite reflux, serviced by a kettle reboiler and horizontal condenser
FC203
condenser
T20710
accumulator
Overhead reflux in top tray temperature control
FC200
LT203
T2073 PDT251
feed tank FC204
Steam reboiler in pressure compensated temperature control
FC201
LT600
T2071
Independent feed flow control reboiler
Bottoms level control Column pressure control with N2
Condensate
LT204
reflux pump
bottoms pump feed pump
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University of Texas finite reflux test runs
COMPOSITION (C6) RUN
PREDICTOR
FLOOD
FEED RATE PRESS DRP REFLUX RATIO (gpm)
(in H2O)
FEED
TOP
BOT
(%)
(%)
(%)
1
no
no
7.02
28.00
0.96
23.12
53.87
14.49
2
no
no
7.03
26.50
0.68
25.06
53.22
14.29
3
no
no
7.00
27.55
0.76
25.42
53.53
13.48
4
no
yes
7.11
60.40
0.72
24.68
49.75
13.55
5
yes
no
7.11
34.10
0.92
22.79
53.97
14.87
6
yes
no
7.25
36.58
0.89
21.27
54.25
15.59
7
yes
no
7.24
38.26
0.85
21.75
53.39
15.16
8
yes
no
7.25
29.62
0.77
23.68
53.00
14.72
9
yes
no
7.35
38.83
0.78
22.77
53.06
14.93
10
yes
no
7.44
40.34
0.89
21.94
52.79
14.66
11
yes
yes
7.55
49.10
0.96
20.35
51.55
15.73
Copyright 2006 2ndpoint, LLC
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University of Texas finite reflux test runs
COMPOSITION (C6) RUN
PREDICTOR
FLOOD
FEED RATE PRESS DRP REFLUX RATIO (gpm)
(in H2O)
FEED
TOP
BOT
(%)
(%)
(%)
1
no
no
7.02
28.00
0.96
23.12
53.87
14.49
2
no
no
7.03
26.50
0.68
25.06
53.22
14.29
3
no
no
7.00
27.55
0.76
25.42
53.53
13.48
4
no
yes
7.11
60.40
0.72
24.68
49.75
13.55
5
yes
no
7.11
34.10
0.92
22.79
53.97
14.87
6
yes
no
7.25
36.58
0.89
21.27
54.25
15.59
7
yes
no
7.24
38.26
0.85
21.75
53.39
15.16
8
yes
no
7.25
29.62
0.77
23.68
53.00
14.72
9
yes
no
7.35
38.83
0.78
22.77
53.06
14.93
10
yes
no
7.44
40.34
0.89
21.94
52.79
14.66
11
yes
yes
7.55
49.10
0.96
20.35
51.55
15.73
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Conclusions; Separation Research Program, University of Texas at Austin “ The Flooding Predictor works on a variety of columns.” “ The Flooding Predictor controls the column very close to the flood point, where the highest efficiency and highest capacity occur.” “ The Flooding Predictor can be installed on nearly any process control computer.” “ Thorough testing at the SRP conclusively indicate DCFP can increase throughput and prevent flooding… while maintaining efficiency. This equates to a 6.22% improvement in sustainable feed rate.”
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Typical demonstration plan Favorable licensing agreement for commercial-scale demonstration site Identification criteria for demonstration column Establish consensus on measure of success Meet with unit personal Conduct a preliminary assessment of column Determine demonstration test objectives Early analysis point building and derivative data collection Pre-commission phase Commissioning phase Post-commissioning and Performance data collection
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