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

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 (NTNU), Trondheim Norway 2) SINTEF ICT, Applied Cybernetics, Trondheim Norway Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

2 Outline • 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 Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

3 Introduction Distillation is energy intensive process. • Exergetic analysis requires minimizing irreversibilities: • mixing effect - large Δ T 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) Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

4 Kaibel Arrangement * A A AB Sharp B/C Split in Prefractionator AB B B ABCD ABCD C C CD 4-Product Separation in CD single shell D D * Kaibel. G (1987) Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

5 Extended Petlyuk Arrangement * A AB A AB C31 Non-Sharp B/C Split in Prefractionator ABC C21 B ABC B BC ABCD ABCD BC C1 C32 C C C22 BCD BCD C33 CD CD D D *Petlyuk, F.B. et al (1965) Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

6 Outline • 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 Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

7 Previous works 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 on operation of 4-product column * Strandberg, J. et. al (2006) ** Ghadrdan, M. et. al (2010) *** Kverland M. et. Al (2010) Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

8 Outline • 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 Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

9 Control Structure (Ordinary Distillation) V> V min V= V min D D L L TC F F TC V V TC B B Single point control Two point control can stabilize the can stabilize profiles column profiles Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

10 Control Structure (Kaibel Column) V=Vmin V>Vmin Rv Loop can be added 4-point • when V=Vmin, 2 temperature temperatures may control with one needed in temperature in prefractionator prefractionator • or, as DOF for any other economic objective Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

11 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 Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

12 Outline • 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 Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

13 Experimental Set up 4 products • Atmospheric pressure • A Packed Column • (Methanol) Magnetic funnel-liquid split & • Product valves Vapor split: Rack and Pinion • B Number of theoretical stages • Feed (Ethanol) (experimentally determined): ABCD Total stages in Prefractionator = 17 – C Total Stages in main column = 21 – High Purity is impossible with (Propanol) – given number of stages and flooding limitation Labview interface • D (Butanol) Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

14 Experimental Set up (Labview Interface)… Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

15 Steady Profiles with 4 temperature loops TEMPERATURES Output 0.45 R/l Loop 81 Output T, C 0.4 80 0 50 100 0 50 100 70 D/l Loop 0.95 T, C 69 0.9 68 0.85 0 50 100 0 50 100 88 1 S1 Loop T, C 87 0.9 86 0.8 0 50 100 0 50 100 111 S2 Loop 0.8 T, C 0.7 110 0 50 100 0 50 100 time, min time, min Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

16 Steady Profiles with 4 temperature loops.. Liquid Split Loop -2 C TEMPERATURES Output 85 R/l Loop 0.45 Output T,C 0.4 0.35 80 0 10 20 30 40 0 10 20 30 40 1 69.5 D/l Loop T,C 69 0.95 0.9 68.5 0 10 20 30 40 0 10 20 30 40 88 S1 Loop 0.9 T,C 87 0.8 0.7 86 0 10 20 30 40 0 10 20 30 40 113 1 S2 Loop T,C 112 0.5 111 0 0 10 20 30 40 0 10 20 30 40 time, min time, min Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

17 Steady Profiles with 4 temperature loops.. Distillate Loop ±1 C TEMPERATURES Output 83 0.45 R/l Loop Output T,C 82 0.4 0.35 81 0 10 20 30 40 0 10 20 30 40 72 0.9 D/l Loop T,C 70 0.8 0.7 68 0 10 20 30 40 0 10 20 30 40 88 S1 Loop 0.9 T,C 87 0.8 0.7 86 0 10 20 30 40 0 10 20 30 40 113 1 S2 Loop T,C 112 0.5 111 0 0 10 20 30 40 0 10 20 30 40 time, min time, min Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

18 Steady Profiles with 4 temperature loops.. S1 Loop ± 1 C TEMPERATURES Output 82.5 0.4 R/l Loop Output T ,C 82 0.38 81.5 0.36 0 10 20 30 0 10 20 30 1 69.5 D/l Loop T ,C 69 0.95 68.5 0.9 0 10 20 30 0 10 20 30 90 0.9 S1 Loop T ,C 88 0.8 0.7 86 0 10 20 30 0 10 20 30 112.5 0.7 S2 Loop T,C 112 0.6 111.5 0.5 0 10 20 30 0 10 20 30 time, min time, min Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

19 Steady Profiles with 4 temperature loops.. S2 Loop ± 1 C TEMPERATURES Output 82.5 0.42 R/l Loop Output T ,C 0.4 82 81.5 0.38 0 10 20 30 0 10 20 30 69.5 1 D/l Loop T ,C 69 0.95 0.9 68.5 0 10 20 30 0 10 20 30 87.5 1 S1 Loop T ,C 87 0.9 86.5 0.8 0 10 20 30 0 10 20 30 113 1 S2 Loop T ,C 112 0.5 111 0 0 10 20 30 0 10 20 30 time, min time, min Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

20 Steady Profiles with 4 temperature loops.. All Loops ± 1 C TEMPERATURES Output 84 0.45 R/l Loop Output T ,C 82 0.4 0.35 80 0 10 20 30 40 0 10 20 30 40 72 1 D/l Loop T ,C 0.8 70 0.6 68 0 10 20 30 40 0 10 20 30 40 90 0.9 S1 Loop T ,C 88 0.8 0.7 86 0 10 20 30 40 0 10 20 30 40 114 1 S2 Loop T ,C 112 0.5 110 0 0 10 20 30 40 0 10 20 30 40 time, min time, min Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns

21 Outline • 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 Control Structure Design for Optimal Operation of Thermally Coupled 16/03/2011 Columns Distillation Columns