Start-up and Control of an Autothermal Reforming (ATR) Reactor

Transcription

1 Start-up and Control of an Autothermal Reforming ATR Reactor Donald J. Chmielewski and Yongyou u Department of Chemical & Environmental Engineering, Chicago, IL Dennis Papadias Chemical Engineering Division Argonne National Laboratory, Argonne, IL Presented at the Annual Meeting of the AIChE: November 005

2 Outline Introduction / Motivation Reactor Modeling and Analysis 1-D Transport and Kinetic Model Model Validation Controller Design 0-D Model and Temperature Regulation Start-up Transition Control Route to Predictive Control

3 Fuel Cell System Electric Power Conditioner Air Fuel Air Fuel Processor Fuel Cell Stack Spent-Fuel Burner Exhaust O CO Thermal & Water Management

4 ydrogen Storage vs. On-Board Reforming Transportation Applications ydrogen Storage Tank PEMFC Liquid Fuel Storage Tank C m n CO Reformer O CO PEMFC

5 ydrogen Storage vs. On-Board Reforming Transportation Applications ydrogen Storage Tank PEMFC Liquid Fuel Storage Tank C m n CO Reformer O CO PEMFC

6 PEMFC and CO Poisoning

7 Fuel Processing Reactors Reformer Water- Gas Shift WGS Preferential Oxidation PrOx PEMFC ydrocarbon Feed Large ydrocarbons Cracked: CO levels down to ~ 10 ppm Low to CO ratio Most CO converted to CO : ~ 1% CO remaining

8 Fuel Processing Reactors Reformer Water- Gas Shift WGS Preferential Oxidation PrOx PEMFC ydrocarbon Feed Large ydrocarbons Cracked: CO levels down to ~ 10 ppm Low to CO ratio Most CO converted to CO : ~ 1% CO remaining

9 Partial Oxidation Total Oxidation: C m n/ O mco n/ m n C m O mco m n/ Steam Reforming: m n CO Water Gas Shift: O CO O ydrocarbon Fuel Air at a substoichiometric rate PO Reactor O CO CO

10 Partial Oxidation Oxidation: C m n/ O mco n/ m n C m O mco m n/ Steam Reforming: m n CO Water Gas Shift: O CO O ydrocarbon Fuel Air at a substoichiometric rate PO Reactor O CO CO

11 Partial Oxidation Oxidation: C m n/ O mco n/ m n C m O mco m n/ Steam Reforming: m n CO Water Gas Shift: O CO O ydrocarbon Fuel Air at a substoichiometric rate PO Reactor O CO CO

12 Water Gas Shift Reaction At igh temperatures equilibrium favors: CO O CO At Low temperatures equilibrium favors: CO O CO More O in the feed will also favor the forward direction

13 Autothermal Reforming Oxidation: C C m n/ O mco n/ m n m O mco m n/ Steam Reforming: m n CO Water Gas Shift: O CO O Steam ydrocarbon Fuel Air at a substoichiometric rate ATR Reactor O CO CO

14 Autothermal Reforming Oxidation: C C m n/ O mco n/ m n m O mco m n/ Steam Reforming: m n CO O CO Water Gas Shift: O ydrocarbon Fuel Air at a substoichiometric rate Steam ATR Reactor CO, O,, CO More Less CO

15 Outline Introduction / Motivation Reactor Modeling and Analysis 1-D Transport and Kinetic Model Model Validation Controller Design 0-D Model and Temperature Regulation Start-up Transition Control Route to Predictive Control

16 PrOx1 PrOx PrOx3 WG1 WG WG3 WG4 Fuel Processor System at Argonne Water Air Fuel ATR Water Air

17 ATR Reactor at Argonne Liquid water Vaporized gasoline, Steam Nozzle ot air igh Space Velocity GSV ~ 50,000/h Catalyst bed eater rod Thermocouple 7 mm Noble Metal Catalyst Metal wall thickness=1.7 mm 1 mm Rh on a Gd-CeO substrate. 1 mm Operating Temperature 96 mm ~ o C Air 5 C eat exchanger

18 Reactor Model Axially Dependent, Nonlinear Dynamic Version, 0 s j g j g j c c c g j g k A x m N i i ij j g j s j g j c r M k 1, 0 ˆ 0 s g g c c c g g p g T T h A x T c m ˆ w s w w w w p w T T x h t T S c Mass Balances: Catalyst Phase: Gas Phase: Energy Balances: Gas Phase: n 1 i c eat transfer to reactor wall,... 1 ˆ i i s g c c s w w w s ax e s s p s r T T h T T x h x T x t T c Solid Phase: Reactor Wall:

19 Model of Reaction Kinetics 1 Total Oxidation Reaction : C m n/ O mco n/ m n O Rate Expression: 1 A s 1 y s fuel y O r where A 1 Oxidation rate is Fuel Diffusion Limited.

20 Model of Reaction Kinetics Water-Gas Shift Reaction: CO Rate Expression: O CO E 3 s s y y RT s s CO r 3 A3e y ; 10 COyO K e Ke Parameters Adapted from: T Wheeler, Jhalani, Klein, Tummala, Schmidt, J. Catal. 004.

21 Model of Reaction Kinetics 3 Steam Reforming Reaction: C m n m O mco m n/ Rate Expression: r A e E RT Activation Energies from: y s fuel y s O 1 K e RT y s fuel Dubien, Schweich, Mabilon, Martin, Prigent, Chem. Eng. Sci A and K : Fit to Experimental Data:

22 , CO molar fraction dry CO molar fraction dry, CO molar fraction dry CO molar fraction dry Micro-Reactor Tests Steady-State Analysis CO CO O/C= O /C ratio CO CO O /C= O/C ratio -

23 Reactor Start-up: A Step Procedure Partial Oxidation Mode to quickly increase temperature ydrocarbon Fuel Air PO Reactor ATR Mode for greater CO conversion Steam ydrocarbon Fuel Air ATR Reactor

24 Temperature C Reactor Start-Up: CPOX Mode mm 19 mm Inlet temperature 100 Experimental Data Simulation Time s

25 Temperature C Reactor Start-Up: ATR Mode 7 mm 19 mm Inlet temperature Experimental Data Simulation Time s

26 Molar fraction dry - Molar fraction dry - Exit Concentrations CPOX Mode: ATR Mode: reactor GC Experiment Experiment CO Simulation Simuation CO CO Simulation Simulation CO Experimental Experimental Time s Time s

27 Molar fractions wet - Molar fractions wet - Steady-State Axial Profiles CPOX Mode: ATR Mode: CO CO O O CO Fuel 0.05 CO Dimensionless x-axis x/l O Fuel Dimensionless x-axis x/l

28 Outline Introduction / Motivation Reactor Modeling and Analysis 1-D Transport and Kinetic Model Model Validation Controller Design 0-D Model and Temperature Regulation Start-up Transition Control Route to Predictive Control

29 Need for Temperature Regulation Vaporized gasoline, Steam Nozzle Liquid water ot air Inlet Air Temperature deg C Primary Disturbance: Inlet Temperature Catalyst bed 500 Inlet Air Temperature Trajectory eater rod Thermocouple 7 mm Metal wall thickness=1.7 mm 1 mm mm mm 100 Air 5 C eat exchanger time sec

30 Open-Loop System Inlet Air Flow Inlet Steam Flow Inlet Air Temperature T 1 T ATR System T 3 T 4 T 5 } Unmeasured but simulated } Measured and simulated Step Tests Performed Using the 1-D Nonlinear Model CPOX and ATR Modes Simulated

31 ATR Temperature o C ATR Temperature o C ATR Temperature o C First Order Plus Dead Time Modeling CPOX Mode Air Flow Rate Inlet Temperature Steam Flow Rate T T T T T 3 T time sec T 5 is Ti K ie FAir, in i s T T 3 T time sec T 5 is Ti K ie TAir, in i s T time sec F T T 5 T 4 T i Steam in is Kie, is 1

32 ATR Temperature o C ATR Temperature o C ATR Temperature o C First Order Plus Dead Time Modeling ATR Mode Air Flow Rate Inlet Temperature Steam Flow Rate T 1 T T 3 T 4 T time sec is Ti K ie FAir, in i s 1 T T 1 T 3 T T 4 T time sec is Ti K ie TAir, in i s T 3 T 1 T 4 T T time sec F T i Steam in is Kie, is 1

33 Feedback Control Temperature Fluctuations in Reactor T 3, set point Inlet Air Temperature T PI Control Inlet Air Flow ATR Reactor T T 4 T 5 T 3, measured T 3 Sensor Noise

34 Feedback Control Disturbances Temperature Fluctuations in Reactor T 3, set point Inlet Air Temperature T 1 Manipulated Variable + - PI Control Inlet Air Flow ATR Reactor T T 4 T 5 T 3, measured T 3 Sensor Noise Control Variable

35 Inlet Air Temperature o C Disturbance Input Simulated Disturbances 500 Inlet Air Temperature Trajectory 60 Temperature Fluctuations and Sensor Noise time sec time sec

36 Temperature o C Inlet Air Flow Rate slpm Analysis of the Feedback Controller Regulation During Partial Oxidation Mode: 100 CV T 3 Response: Open vs. Closed-loop MV Air Flow Response: Open-loop vs. Closed-loop Open-loop 100 Open-loop Closed-loop 0 Closed-loop time sec time sec

37 Temperature o C Inlet Air Flow Rate slpm Analysis of the Feedback Controller Regulation During ATR Mode: CV T 3 Response: Open- vs. Closed-loop Open-loop MV Air Flow Response: Open vs. Closed-loop 00 Open-loop 150 Closed-loop Closed-loop time sec time sec

38 Outline Introduction / Motivation Reactor Modeling and Analysis 1-D Transport and Kinetic Model Model Validation Controller Design 0-D Model and Temperature Regulation Start-up Transition Control Route to Predictive Control

39 Transition from CPOX to ATR Mode Steam Flow Rate TF w.r.t. Steam T 3, set point + - PI + + Air Flow TF w.r.t. Air Flow + + T 3

40 Reactor Temperature deg C Steam Flow Rate g/min Transition from CPOX to ATR Mode Impact of Steam Injection 800 With Feedback Controller Without Feedback Controller Steam Flow Rate time sec

41 Reactor Temperature deg C Steam Flow Rate g/min Transition from CPOX to ATR Mode Impact of Steam Injection Rate With Feedback Controller Without Feedback Controller 100 Steam Flow Rate time sec 50

42 Feed-forward Control + - T 3, set point Steam Flow Rate Measured PI G ff s + + Air Flow G d s G p s + + T 3 G ff Gd s s s G s p

43 Reactor Temperature deg C Impact of Feed-forward Control Steam Injection: With and Without Feed-forward 900 Feed-forward / Feedback Controller Feedback Controller Only time sec

44 Model Mismatch in Feed-forward Control + - T 3, set point Steam Flow Rate Measured PI G ff s + + Air Flow G d s G p s + + T 3 G ff Gd s s s G s p If the G d s or G p s used to define G ff s are different than the actual plant then mismatch occurs.

45 T 3 Temperature o C T 3 Temperature o C Impact of Model Mismatch Impact of Model Mismatch on Feed-forward Feed-forward With Model Mismatch Feed-forward Without Model Mismatch Impact of Model Mismatch on Feed-forward Feed-forward Without Model Mismatch Feedback Controller Only 600 Feedback Controller Only 400 Feed-forward With Model Mismatch time sec time sec

46 Conclusions Modeling 0-D model sufficient for feedback design. Nonlinear model likely needed for feed-forward design. Feedback Control CPOX and ATR Modes Good performance w.r.t. inlet conditions and sensor noise. Good performance during CPOX to ATR Transition, if transition is slow enough. Feed-forward Control Model mis-match is a major concern

47 Use of Predictive Control for CPOX to ATR Transition MPC can incorporate a nonlinear model during transition. Can enforce explicit bounds on process variables i.e., maximum flow rates and minimum temperatures. owever, fast running model is needed to meet the computational requirements of on-line optimization.

48 Temperature, o C Reduced Order Modeling z = 7 mm 800 z = 19 mm Measured Inlet Temperature Experimental Measurements - "*" igh Order CFD Simulation - Solid Reduced Order Simulation - Dashed Time, s Computational Effort: NLM: ~10 min ROM: ~30 sec

49 Mole Fraction, wet basis Reduced Order Modeling CO CO O igh Order CFD Simulation - Solid Reduced Order Simulation - Dashed Fuel Dimensionless Axial Position, 1 unit =7mm Computational Effort: NLM: ~10 min ROM: ~30 sec

50 Acknowledgements Collaborators Shabbir Ahmed ANL erek Clack IIT Sheldon Lee ANL Jai Prakash IIT Students Funding Kevin Lauzze IIT Argonne National Laboratory Graduate College, IIT Armour College of Engineering, IIT Chemical & Environmental Engineering Dept, IIT

51 Temperature C ATR Reactor Model Partial Oxidation Start-up: Liquid Water Spray at 75 s mm mm Inlet temperature Time s