Teaching Fundamentals of Process Dynamics and Control Using Dynamic Simulator of an Integrated Gasification Combined Cycle (IGCC) plant with CO 2 Capture Debangsu Bhattacharyya 1,2, Richard Turton 1,2 and Stephen E. Zitney 1 1 AVESTAR Center, NETL, Morgantown, WV 2 West Virginia University, Morgantown, WV 1
Objectives Use IGCC dynamic simulator and operator training system (OTS) to: o o o o o Demonstrate real life applications of control theory Show students where current course work fits into the process and power plant Demonstrate crucial role that control system plays Demonstrate interactions between different equipment, systems, and variables Provide students with a big picture view, as well as finer details as much as tractable and applicable in about 4 hours of simulator time 2
Dynamics and Controls Course at a Glance Course focuses on dynamics and control of chemical processes. Senior year course for Chemical Engineering undergraduates. Currently there are 42 students in this class. Only course to date for the undergraduates concentrating on both process dynamics and control. Linear single input single output (SISO) systems are mostly studied. The control software environment used is in the class is Matlab/Simulink from The Mathworks. The OTS demonstrations make use of DYNSIM dynamic simulation software and InTouch human-machine interface (HMI) software, both from Invensys Operations Management. 3
www.netl.doe.gov/avestar
AVESTAR TM Center Advanced Virtual Energy Simulation Training And Research Mission: Comprehensive training, education, and R&D on the efficient, safe, and reliable operation of clean energy systems Tools: Dynamic Simulators with Operator Training Systems (OTS) 3D virtual Immersive Training Systems (ITS) Simulators: IGCC w/ CO 2 capture (OTS March 2011, ITS Nov. 2011) Facilities: NETL, WVU/NRCCE in Morgantown, WV Key Partners: Customers: Utilities, E&Cs, Equipment vendors (Engineers, Operators, Trainers, Managers) Universities (Researchers, Students)
IGCC Power Plant with CO2 Capture Dynamic Simulator and Operator Training System
IGCC with CO 2 Capture Dynamic Simulator Reference Plant (2 Trains) Plant Section Gasification Description Entrained-flow Gasifier Air Separation Elevated-P Cryogenic ASU (95% vol O 2 ) H 2 S Separation Sulfur Recovery CO 2 Separation CO 2 Compression Gas Turbines Steam Cycle Power Output Physical Solvent AGR 1 st Stage Claus Plant Physical Solvent AGR 2 nd Stage Four stage (2200 psia) Adv. F Class (232 MW output each) Subcritical (1,800 psig/1,000ºf/1,000ºf) 746 MW gross (556 MW net) References IGCC Case #2, Cost and Performance Baseline for Fossil Energy Power Plants Study, Volume 1: Bituminous Coal and Natural Gas to Electricity, National Energy Technology Laboratory, www.netl.doe.gov, DOE/NETL 2010/1397, November 2010.
IGCC Dynamic Simulator/OTS Capabilities and Features Simulator Scope Gasification with CO 2 Capture Combined Cycle Electrical System Fuel Switching and Co firing Coal, Petcoke, Biomass High Fidelity Dynamic Model Mulitzonal kinetic reactor models Normal base load operations Startup, shutdown, load following Model Performance Slow (0.5X), real time, fast (2.5X) Multiple dynamic engines running in parallel Operator Features Human-Machine Interface (HMI) Variable and Group Trends Audible and Visual Alarms Instructor Features Initial Condition (IC) and Scenario management Remote Functions (RFs) Malfunctions (Default/Programmed) Trainee Performance Monitor Controls DCS control emulation Regulatory PID control loops Coordinated control Gasifier and Gas turbine lead Partner: Invensys Operations Management; Software: Dynsim, InTouch
IGCC Immersive Training System/ITS Capabilities and Features 3D Virtual Plant Model 3D computer aided design (CAD) 3D visualization model Plant photos for photorealism IGCC Puertollano, Spain IGCC Wabash River, IN Coal to Ammonia Coffeyville, KS 3D Immersive Interaction Avatar represents field operator Navigation using game pad Single operator 3D visor with head tracking Multiple operators Projectors/screens (10 ) or 3D LCDs (65 ) with 3D glasses Partner: Invensys Operations Management; Software: EYESim
IGCC Dynamic Simulator/OTS and ITS Software Invensys Operations Management Dynsim TM Gasification and CO 2 capture through gas turbine Process controls Dynsim Power TM Steam cycle InTouch TM Human machine interface (HMI) Look and feel of plant DCS operator interface EYESim TM Virtual engines for ITS Sim4Me Executive for integration of dynamic engines Distribution of engines across CPUs for real time performance
Demonstration Outlines Course can be broadly divided into two strongly coupled sections: Process Dynamics Process Control OTS will be utilized for better understanding of each of these sections Process Dynamics examples shown here: First principles dynamic model Implementation of ideal forcing functions Time-delay systems Process Control examples shown here: Open-loop unstable systems Closed-loop stability: Proportional gain for stability limits Feedback-augmented feedforward control Cascade control 11
Process Dynamics Example 12
First Principles Dynamic Model Due to class time constraints, only simple, first principles dynamic models (e.g., CSTR, jacketed vessel, single flash vessel, etc.) can be developed Thus, more complex and interesting process dynamics cannot be captured as these equipment significantly interact with themselves and other equipment in the plant When these equipment items are shown in the dynamic simulator/ots model, students can better understand how these equipment fit into a real plant and how they interact Big picture view as well as smaller details Quick view of plant design, P&ID, and dynamic simulation. Show flowsheet level view followed by equipment level details Example: Gasifier feed and cooling section of an IGCC plant (PFD not shown here due to brevity) 13
Gasifier Feed and Cooling Section in IGCC Plant Steady-state process model in PRO/II TM 14
Gasifier Feed and Cooling Section in IGCC Plant Process & Instrumentation Diagram Reference DOE/NETL IGCC Dynamic Simulator Research and Training Center, Volume 2: IGCC Process Descriptions, DOE/NETL 2008/1324, June 2008.
Dynamic Process Model in Dynsim TM
Detailed GasifierModel 17
Details of Kinetic Model for One Zone of Multizonal Gasifier Model 18
Gasifier Feed and Cooling Section at HMI level
Implementation of Ideal Forcing Functions Ideal forcing functions (step, ramp, etc.) are widely discussed and utilized in introductory process dynamics and control classes. Can they be realized in actual plant? If yes, how? Lean solvent flow control valve is stepped up and the flow is monitored. 20
Time Delay Systems Show how time-delay occurs in an actual plant Use step response data for identifying process model Coal feed to plant is step decreased Transient response in CO 2 composition at inlet of H 2 S absorber is recorded 21
Coal feed/syngas Flow Path Gasifier 22
Syngas Flow Path Syngas Scrubber 23
Syngas Flow Path Shift Reactors 24
Syngas Flow Path Syngas Cooling 25
Syngas Flow Path Mercury Removal 26
CO 2 Concentration at CO 2 Absorber Inlet 27
Process Control Example 28
Open Loop Unstable Systems Case 1: Closed-loop system Case 2: Open-loop system, emergency controller takes over Case 3: Open-loop system, No emergency controller, plant shuts down Demonstration example: Radiant Syngas Cooler (RSC) steam generator 29
Case 1: Closed loop system : Coal feed-flow is step increased : Demonstrate control loop performance for disturbance rejection : Demonstrate how different systems interact in an actual plant 30
Transient Response of RSC Steam Drum Pressure 31
Interaction of RSC Steam Drum with Other Systems Main HP Steam Generation System 32
HP Steam Header Interaction of RSC Steam Drum with Other Systems 33
Case 2: Open-loop system; emergency controller takes over : Plant still operates normally with loss of efficiency : Demonstrate necessity of good design for which dynamic consideration is crucial 34
Case 3: Open-loop system; No emergency controller; plant shuts down : Drum level decreases to very low level triggering plant shutdown : Demonstrate other lines of defense - emergency shutdown system 35
Closed-loop stability: Proportional Gain for Stability Limits Students carry out closed-loop stability analysis (by Routh stability analysis, direct substitution, etc.) to determine limiting proportional gain for stability of closed-loop system. Demonstration of theory with RSC pressure control by slowly modifying proportional gain. K c =1 K c =3 K c =1 K c =1 K c =3 K c =1 36
Feedback augmented Feed Forward Control Demonstrate role of feedforward compensator in improved disturbance rejection characteristics Vary magnitude of disturbance Demonstration example: H 2 S/SO 2 ratio control at inlet of 1 st Claus Reactor; Feedforward H 2 S flow in inlet feed 37
Feedback loop: H 2 S/SO 2 ratio at inlet of 1 st Claus Reactor 38
Cascade Control Demonstrate role of cascade control for disturbance rejection Modify tuning of inner loop and demonstrate its effect on control loop performance Demonstration example: Selexol Unit Stripper 39
Additional Teaching Points Show role of inventory/thermal hold-up in dynamic response, especially its role during plant startup/shutdown Identify typical candidate first order/second order processes from step response data and then analyze them. Carry out stability analysis on identified model. For example, students can calculate required proportional gain based on identified process model and then test on actual process. Determine appropriate tuning parameters based on identified model and then test its performance Demostrate startup/shutdown dynamics and control challenges and many more 40
Practical Control Test A few sample questions: 1. Choose any arbitrary flowsheet and any arbitrary controller. What are the input and output of the controller that you have selected? What are the inputs and outputs of the process that you have selected? 2. Draw a block diagram of the closed loop system. 3. Is this system open-loop stable? Why or why not? [Note: you can answer this question theoretically or by carrying out an experiment] 4. What are the disturbance variables(s) for this system? 5. Check the controller performance for servo control. How did you check it? What will you do to improve its performance for servo control further? 6. Check the controller performance for regulatory control. How did you check it? What will you do to improve its performance for regulatory control further? 7. Please note any loop interaction that you have observed while testing the regulatory control. 41
Conclusions State-of-the-art, high-fidelity, real-time dynamic simulator and operator training system is used for teaching process dynamics and control to undergraduate chemical engineering students. A few examples are cited. Many other possibilities are being explored. Suggestions are welcome. 42