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Control Structure Design for Optimal Operation of 4-Product - - PowerPoint PPT Presentation

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1 Control Structure Design for Optimal Operation of 4-Product Thermally Coupled Columns Deeptanshu Dwivedi 1 , Ivar J. Halvorsen 2 , Sigurd Skogestad 1 1) Department of Chemical Engineering, Norwegian University of Science & Technology

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Control Structure Design for Optimal Operation of 4-Product Thermally Coupled Columns

Deeptanshu Dwivedi1, Ivar J. Halvorsen2, Sigurd Skogestad1

1) Department of Chemical Engineering, Norwegian University of Science & Technology (NTNU), Trondheim Norway 2) SINTEF ICT, Applied Cybernetics, Trondheim Norway

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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Introduction

  • Distillation is energy intensive process.
  • Exergetic analysis requires minimizing irreversibilities:
  • mixing effect
  • large ΔT across column
  • This leads to Complex distillation arrangement:
  • Kaibel Arrangement
  • Petlyuk Arrangement
  • intermediate Reboilers & Coolers etc
  • HIDIC distillation
  • Potential Energy Savings up to ~50 % for 4 product extended

Petlyuk & up to ~30 % in Kaibel Arrangement*

* Halvorsen et. al. (2003)

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Kaibel Arrangement *

* Kaibel. G (1987)

D ABCD CD A B C AB ABCD AB CD D A B C

4-Product Separation in single shell Sharp B/C Split in Prefractionator

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Extended Petlyuk Arrangement *

D ABCD BCD A B C ABC AB BC CD

*Petlyuk, F.B. et al (1965)

Non-Sharp B/C Split in Prefractionator

C31 C32 C33 ABCD ABC BCD D A B C C22 C1 AB CD BC C21

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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Simulation based studies carried with a plant wide perspective – Stabilizing operation of a 4-product Kaibel column *

  • Close 4 temperature loops for stabilization &

Inventory Control – Optimal steady-state solutions for operating under economic objectives** – Model predictive control of the 4-product kaibel column *** Thus there is an incentive to carry out experimental studies

  • n operation of 4-product column

* Strandberg, J. et. al (2006) ** Ghadrdan, M. et. al (2010) *** Kverland M. et. Al (2010)

Previous works

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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B TC L F D V

V> V min Single point control can stabilize the profiles

Control Structure (Ordinary Distillation)

L F D V

V= V min

TC TC

Two point control can stabilize column profiles

B

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4-point temperature control with one temperature in prefractionator

V>Vmin

Rv Loop can be added

  • when V=Vmin, 2

temperatures may needed in prefractionator

  • or, as DOF for any
  • ther economic
  • bjective

V=Vmin

Control Structure (Kaibel Column)

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Control Structure (As used in experiments)

  • Decentralized Control with 4 PI Controllers
  • 4 temperature sections 2, 3, 5, 7 in

regulatory layer with R/l, D, S1 & S2

  • V=Vmax, Vapor Split (Rv) not part of

regulatory layer

Next couple of slides summarize experimental validation

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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Experimental Set up

  • 4 products
  • Atmospheric pressure
  • Packed Column
  • Magnetic funnel-liquid split &

Product valves

  • Vapor split: Rack and Pinion
  • Number of theoretical stages

(experimentally determined):

– Total stages in Prefractionator = 17 – Total Stages in main column = 21 – High Purity is impossible with given number of stages and flooding limitation

  • Labview interface

Feed ABCD A (Methanol) B (Ethanol) C (Propanol) D (Butanol)

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Experimental Set up (Labview Interface)…

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Steady Profiles with 4 temperature loops

50 100 80 81 T, C 50 100 0.4 0.45 50 100 68 69 70 T, C 50 100 0.85 0.9 0.95 50 100 86 87 88 T, C 50 100 0.8 0.9 1 50 100 110 111 time, min T, C 50 100 0.7 0.8 time, min

R/l Loop D/l Loop S1 Loop S2 Loop Output

TEMPERATURES Output

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Liquid Split Loop -2 C

Steady Profiles with 4 temperature loops..

10 20 30 40 80 85 T,C 10 20 30 40 0.35 0.4 0.45 10 20 30 40 68.5 69 69.5 T,C 10 20 30 40 0.9 0.95 1 10 20 30 40 86 87 88 T,C 10 20 30 40 0.7 0.8 0.9 10 20 30 40 111 112 113 time, min T,C 10 20 30 40 0.5 1 time, min

R/l Loop D/l Loop S1 Loop S2 Loop Output

TEMPERATURES Output

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Distillate Loop ±1 C

Steady Profiles with 4 temperature loops..

10 20 30 40 81 82 83 T,C 10 20 30 40 0.35 0.4 0.45 10 20 30 40 68 70 72 T,C 10 20 30 40 0.7 0.8 0.9 10 20 30 40 86 87 88 T,C 10 20 30 40 0.7 0.8 0.9 10 20 30 40 111 112 113 time, min T,C 10 20 30 40 0.5 1 time, min

R/l Loop D/l Loop S1 Loop S2 Loop Output

TEMPERATURES Output

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18 10 20 30 81.5 82 82.5 T ,C 10 20 30 0.36 0.38 0.4 10 20 30 68.5 69 69.5 T ,C 10 20 30 0.9 0.95 1 10 20 30 86 88 90 T ,C 10 20 30 0.7 0.8 0.9 10 20 30 111.5 112 112.5 time, min T,C 10 20 30 0.5 0.6 0.7 time, min

R/l Loop D/l Loop S1 Loop S2 Loop Output

S1 Loop ± 1 C

Steady Profiles with 4 temperature loops..

TEMPERATURES Output

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Steady Profiles with 4 temperature loops..

S2 Loop ± 1 C

10 20 30 81.5 82 82.5 T ,C 10 20 30 0.38 0.4 0.42 10 20 30 68.5 69 69.5 T ,C 10 20 30 0.9 0.95 1 10 20 30 86.5 87 87.5 T ,C 10 20 30 0.8 0.9 1 10 20 30 111 112 113 time, min T ,C 10 20 30 0.5 1 time, min

R/l Loop D/l Loop S1 Loop S2 Loop Output

TEMPERATURES Output

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Steady Profiles with 4 temperature loops..

10 20 30 40 80 82 84 T ,C 10 20 30 40 0.35 0.4 0.45 10 20 30 40 68 70 72 T ,C 10 20 30 40 0.6 0.8 1 10 20 30 40 86 88 90 T ,C 10 20 30 40 0.7 0.8 0.9 10 20 30 40 110 112 114 time, min T ,C 10 20 30 40 0.5 1 time, min

R/l Loop D/l Loop S1 Loop S2 Loop Output

All Loops ± 1 C

TEMPERATURES Output

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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Vapor Split Experiment

  • Total reflux operation
  • Liquid Split Valve (R/l) in Manual
  • Manipulated valve: Vapor Split Valve V1 & V2
  • Controlled variable: T2-T5
  • Split Range logic

Output Valve Opening 0 50% 100% 100 %

V1 V2

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From top left: Valve in fully open position Top right: Rack and pinion arrangement. Schematic of the vapor split valve

Vapor Split Experiment..

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24 50 100

  • 5

5 T, C 50 100 0.5 1 50 100 70 75 80 T, C 50 100 70 75 80 50 100 5 10 Steps 50 100 5 10 50 100

  • 2

2 time, min Valve o/p 50 100 1.5 2 2.5 time, min KW

T2 R/l Output Reboiler Duty PF Valve MC Valve Rv O/p T7 delT T2-T5

Vapor Split Experimental run (Total Reflux, two component)

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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Petlyuk Arrangement- Model Details

Model Assumptions

  • Ideal vapor liquid equilibria
  • 40 Theoretical stages in each

column

  • The base flows calculated

from the Vmin diagram* which calculated the minimum

C31 C32 C33 ABCD ABC BCD D A B C C22 C1 AB CD BC C21

* Halvosen, I.J. & Skogestad, S. (2003)

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Control Structure: Petlyuk Column

  • Two Liquid Levels & 6

Sensitive Temperatures are CVs in Regulatory layer

  • The loops were closed and

tuned sequentially from left to right

  • All loops tuned by the SIMC

rules

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Close loop results: Petlyuk Column

+10 % Feed Disturbance

500 1000 1500 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1 time Purity Top Purity S1 Purity S2 Purity Bottoms

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  • Introduction
  • System 1: 4- Product Kaibel Column

– Previous Work – Control Structure – Experimental Setup – Experimental Runs- Steady state profiles – Experimental Runs- Vapor Split Experiment

  • System 2: 4- Product Extended Petlyuk Column

– Model Details – Control Structure – Close Loop Results

  • Conclusions

Outline

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Conclusion

  • 4 – Product Kaibel Column

– Experimental Studies Confirm Stable Profiles with 4 point temperature control – A lab scale prototype of vapor split valve effectively controlled vapor flow between prefractionator and main column

  • 4- Product Extended Petlyuk Column

– Simulation studies suggest that 4-product extended petlyuk column can be controlled and operated with 6 point temperature control in the regulatory layer

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Acknowledgements

  • Jens Strandberg for building the column
  • Prof Heinz Presig
  • Dr Mohammad Shamsuzuhha
  • Jon Anta Buljo Hansen
  • Terje Mugaas
  • Filip Voss
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References

  • Halvorsen, I.J.; Skogestad, S; “Minimum Energy Consumption in Multicomponent
  • Distillation. 3.More Than Three Products and Generalized Petlyuk Arrangements”, Ind.
  • Eng. Chem. Res. 2003, 42, 616-629
  • Kaibel, G. Distillation Columns with Vertical Partitions.Chem. Eng. Technol. 1987, 10, 92-

98.

  • Petlyuk, FB. Platonv, VM. Slavinskii, DM. (1965), Thermodynamically Optimal Methods for

Separating Multicomponent Mixtures. Int. Chem. Eng. 1965, 5(3), 555.

  • Strandberg, J., Skogestad, S., Stablizing Operation of a 4-Product Iintegerated Kaibel
  • Column. SYMPOSIUM SERIES NO. 152, Distillation & Absorption
  • Ghadrdan, M., Halvosen I.J., Skogestad, S., Optimal Operation of Kaibel Distillation

Columns, Chemical Engineering Research and Design (2010), doi:10.1016/j.cherd.2011.02.007

  • Kverland M, Halvorsen I.J., Skogestad. S,: Model Predictive Control of a Kaibel Distillation

Column., Proceed. of the 9th Intern. Symp. on Dynam. and Control of Process Systems (DYCOPS 2010)

  • Halvorsen, I.J., Skogestad, S. (2003) Minimum Energy Consumption in Multicomponent
  • Distillation. 1. Vmin Diagram for a Two-Product Column, Ind. Eng. Chem. Res., 2003, 42 (3),

pp 596–604

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Thank you!!