Eldridge Research Group Melissa Donahue Bailee Roach Jeff Weinfeld Colton Andrews Johannes Voggerneiter 1
Modeling of Multiphase Contactors with Computational Fluid Dynamics
Dividing Wall Distillation 3
Control of a Dividing Wall Distillation Column Melissa Donahue, Bailee Roach, Michael Baldea, and R. Bruce Eldridge October 18 th, 2016 1
Agenda DWC Overview Pilot Plant Results Feed System #1 Feed System #2 Future Work 2
Motivation Dividing Wall Column (DWC) Benefits: Reduce reboiler duty Lower environmental impact Minimize irreversible mixing Reduce capital investment Assumptions: Ideal vapor Ideal liquid No pressure losses No wall heat transfer Constant relative volatilities % of Traditional Reboiler Duty 50% α a = 1.21 α b = 1.10 α c = 1.00 A:30 B:40 C:30 Source: R. Agrawal R and ZT Fidkowski 80% 90% 60% 70% 60% 70% 80% 90% 3
Traditional Distillation A B A B C B C C 4
DWC Operation A A B C B C 5
DWC Operation A A A B A B C B A B C B B B C [1] I. J. Halvorsen and S. Skogestad, Optimal Operation of Petlyuk Distillation: Steady-State Behavior, Journal Of Process Control, no. 9, pp. 407 424, 1999. C C 6
DWC Pilot Plant Rectifying Section Upper DW Section Lower DW Section Stripping Section 7
Process Flow Diagram Top Product Top of Wall Tank Feed Heater Side Product Product & Feed Tanks Steam 8
Feed System #1 DB/LSV Chemical α ic α ij A 6.66 B 1.66 C 1.00 4.01 1.66 D Distillate Flow B Bottoms Flow L Reflux S Side Draw Flow V Vapor Boilup Ling, H.; Luyben, W. Temperature Control of the BTX Divided-Wall Column. Industrial and Engineering Chemistry Research 2010, 49, 189. 9
Temperature ( F) Feed System #1 220 200 180 160 140 120 100 6:57:36 PM 7:55:12 PM 8:52:48 PM 9:50:24 PM Time Top Temp SP Top Temp PV Upper Prefrac Temp SP Upper Prefrac Temp PV Lower Mainfrac Temp SP Lower Mainfrac PV 10
Temperature ( F) Feed System #1 220 200 180 160 140 Location Purity (mole % A/B/C) Bottoms Product 0/8/92 Side Product 12/81/7 Top of Wall 83/16/1 Distillate Product 100/0/0 120 100 6:43:12 PM 7:40:48 PM 8:38:24 PM 9:36:00 PM Time Top Temp SP Upper Prefrac Temp SP Lower Mainfrac Temp SP Top Temp PV Upper Prefrac Temp PV Lower Mainfrac PV 11
Temperature ( F) Steam Flow (lb/hr) Feed System #1 240 220 200 170 150 130 110 180 160 140 120 Steam Flow 90 70 50 30 10 100 4:04:48 PM 4:26:24 PM 4:48:00 PM 5:09:36 PM 5:31:12 PM Time -10 Top Temp SP Top Temp PV Mainfrac Temp SP Mainfrac Temp PV Stripping Temp SP Stripping Temp PV Steam 12
Model Predictive Control Control Variables Top Temp Prefrac Temp Mainfrac Temp Bottom Temp Manipulated Variables Reflux Wall Split Side Draw Ratio Steam Flow FY o MPC run through DeltaV PredictPro o Model identified using pseudorandom binary sequence testing process o Four hour testing time FY 13
Temperature ( F) Feed System #1 220.00 Temperature Control using MPC 200.00 180.00 160.00 140.00 Rectifying Temp SP Rectifying Temp PV Prefrac Temp SP Prefrac Temp PV Mainfrac temp SP Mainfrac Temp PV 120.00 100.00 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM Time 14
mole frac mole frac mole frac mole frac Feed System #1 Top Product Top of Wall n-pentane cyclohexane n-heptane n-pentane cyclohexane n-heptane 1 1 0.95 0.95 0.9 0.9 0.85 0.85 0.8 0.8 0.75 0.75 0.7 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM 0.3 0.25 0.2 0.15 0.1 0.05 0 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM Time 0.7 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM 0.3 0.25 0.2 0.15 0.1 0.05 0 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM Time 15
mole frac mole frac mole frac mole frac Feed System #1 Side Product n-pentane cyclohexane n-heptane 1 0.95 0.9 0.85 0.8 0.75 0.7 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM 0.3 0.25 0.2 0.15 0.1 0.05 0 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM Time Bottom Product n-pentane cyclohexane n-heptane 1 0.95 0.9 0.85 0.8 0.75 0.7 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM 0.3 0.25 0.2 0.15 0.1 0.05 0 6:57:36 PM 10:33:36 PM 2:09:36 AM 5:45:36 AM Time 16
Feed System #2 Chemical α ic α ij A 10.81 B 3.69 2.93 Ratio ontroller X C 1.00 3.69 X Ratio Controller FY DB/LSV DB/LV Ling, H.; Luyben, W. Temperature Control of the BTX Divided-Wall Column. Industrial and Engineering Chemistry Research 2010, 49, 189. 17
Feed System #2 F DB/LSV B A C F DB/LV Distillate Composition 99.83/0.17/0.00 99.57/0.43/0.00 Side Composition 0.24/99.49/0.27 0.20/99.30/0.50 Bottoms Composition 0.03/0.40/99.50 0.00/0.30/99.70 Top of Wall Composition 46.82/53.13/0.05 12.4/87.5/0.06 B A C Liquid Split 50/50 26/74 (prefrac/mainfrac) Reflux Ratio 8.55 6.44 Steam Flow 45.33 lb/hr 38.77 lb/hr Column dp 3.62 in H2O 2.41 in H2O Feed Flow 40 lb/hr 50 lb/hr 18
Feed Disturbance (initial vs. final) Mole Percent A B C Starting Feed 8.8 77.7 13.5 Feed Transition 1 14.8 65.6 19.6 Feed Transition 2 28.2 41.4 30.4 19
Feed Disturbance Initial: FY 99.6 mol % A 0.4 mol % B 0.0 mol % C Final: FY 99.46 mol % A 0.54 mol % B 0.0 mol % C FY 24.1 lbm/hr 10.6 lbm/hr 30.2 lbm/hr 3.9 lbm/hr 12.4 mol % A 87.5 mol % B 0.1 mol % C FY 7.2 lbm/hr 18.9 lbm/hr 20.5 lbm/hr 23 lbm/hr 21.7 mol % A 78.2 mol % B 0.1 mol % C 50 lbm/hr 65 lbm/hr 8.8 mol % A 77.7 mol % B 13.5 mol % C 15.5 lbm/hr 38.7 lbm/hr 0.3 mol % A 99.3 mol % B 0.4 mol % C 28.2 mol % A 41.4 mol % B 30.4 mol % C 20.2 lbm/hr 27.7 lbm/hr 1.4 mol % A 98.3 mol % B 0.3 mol % C 39.3 lbm/hr 39.2 lbm/hr 0.0 mol % A 0.3 mol % B 99.7 mol % C 9.8 lbm/hr 0.0 mol % A 0.4 mol % B 99.6 mol % C 26.1 lbm/hr 20
Temperature ( F) Reflux (lb/hr) Feed Disturbance 220 45 215 40 210 35 205 200 30 25 Rectifying temp SP Rectifying temp PV Reflux 195 20 190 15 8:24:00 AM 10:04:48 AM 11:45:36 AM 1:26:24 PM 3:07:12 PM Time 21
Results Summary Multiple Feed Systems Stable Control 4-point, 3-point, and 2-point PID MPC derived using DeltaV Disturbance Testing Decrease in Steam Feed composition & flow Liquid Split Need to determine operating range of liquid split Prefrac temperature isn t always sensitive to liquid split 22
Future Work Refine Model Various Feed Compositions Feed Disturbance Testing Further MPC Testing 23
Thank you SRP Staff Eldridge and Baldea Groups James R. Fair Process Science Technology Center 24
Questions? 25