CHE 185 – PROCESS CONTROL AND DYNAMICS

1. CHE 185 – PROCESS CONTROL AND DYNAMICS CONTROL OBJECTIVES

2. CATEGORIES OF OBJECTIVES • PROCESS OBJECTIVES • QUANTITY • MEET PRODUCTION TARGETS • OPERATE AT CONSTANT LEVELS • QUALITY • ALL PRODUCT TO MEET MINIMUM CRITERIA • MINIMIZE PRODUCTION OF OFF-SPEC OR BYPRODUCT COMPONENTS

3. CATEGORIES OF OBJECTIVES • PROFITABILITY • MAXIMIZE YIELDS • MINIMIZE UTILITY CONSUMPTION • Products with Reduced Variability • reduced variability products are in high demand and have high value added • Product certification (e.g., ISO 9000) are used to guarantee product quality

4. Example of Improved Control

5. PLANT OPERATIONAL OBJECTIVES • RELIABILITY • ON-STREAM TIME • MINIMIZE UNSCHEDULED OUTAGES • SAFETY - FAIL SAFE OPERATION • OUT-OF-RANGE ALARMS • EMERGENCY SHUTDOWN – PANIC BUTTON • EMERGENCY INTERLOCKS – AUTOMATIC OPERATION

6. SAFETY RELIEF SYSTEMS • STANDARDS AND CODES • ASME (American Society of Mechanical Engineers) Boiler & Pressure Vessel Code, Section VIII Division 1 and Section I • API (American Petroleum Institute) Recommended Practice 520/521, API Standard 2000 et API Standard 526 • ISO 4126 (International Organisation for Standardisation)

7. MODEL DERIVATION • INVENTORY TANK • DESIGN BASES • STEADY STATE FLOWS • DISCHARGE FLOW IS A FUNCTION OF h • CONSTANT AREA A • CONSTANT DENSITY ρ

8. DERIVE EQUATIONS MASS BALANCE ASSUMPTION OF STEADY STATE

9. DERIVE EQUATIONS • VALVE CHARACTERISTICS • LEVEL CHANGES • LINEAR ODE • NONLINEAR ODE

10. MODEL DERIVATION • HEATING TANK • DESIGN BASES • CONSTANT VOLUME • PERFECT MIXING IN VOLUME • PERFECT INSULATION • CONSTANT FLUID PROPERTIES, DENSITY ρ AND HEAT CAPACITY cP

11. DERIVE EQUATIONS MASS BALANCE ENERGY BALANCE

12. DERIVE EQUATIONS • AS INITIAL VALUE PROBLEM • Given • physical properties (r, Cp) • operating conditions (V, w, Ti, Q) • initial conditionT(0) • Integrate model equation to find T(t)

13. MODEL DERIVATION • CSTR • REACTION A → B • DESIGN BASES • Constant volume • FEED IS Pure A • Perfect mixing • INSULATED • Constant FLUID properties (r, Cp, DH, U) • Constant cooling jacket tempERATURE

14. OTHER RELATIONSHIPS • Constitutive relations • Reaction rate/volume • r = kcA= k0exp(-E/RT)cA • Heat transfer rate: • Q = UA(Tc-T)

15. DERIVE EQUATIONS • MASS BALANCE • COMPONENT BALANCE ON A

16. DERIVE EQUATIONS ENERGY BALANCE

17. SOLUTION CONSTRAINTS • EQUATION PROPERTIES • 2 Odes • For dynamic model Time is the independent variable • Nonlinear and coupled • Initial value problem requires numerical solution • Degrees of freedom • 6 unknowns • 2 equations • Must specify 4 variable values

18. MODEL DERIVATION • BIOCHEMICAL REACTOR (GENERAL) • DESIGN BASES • CONTINUOUS OPERATION • Sterile feed • Constant volume • Perfect mixing • Constant REACTION temperature & pH • Single rate limiting nutrient • Constant yields • Negligible cell death

19. DERIVE EQUATIONS • CELL MASS • DEFINITION OF TERMS • VR = reactor volume • F = volumetric flow rate • D = F/VR= dilution rate • Non-trivial steady state: • Washout:

20. DERIVE EQUATIONS • PRODUCT RATE • SUBSTRATE CONCENTRATION • S0= feed concentration of rate limiting substrate • Steady-state:

21. SOLUTION CONSTRAINTS • EQUATION STRUCTURE • State variables: x = [XSP]T • Third-order system • Input variables: u = [DS0]T • Vector form:

22. acetaldehyde/ pyruvate (S4ex) degraded products glucose r7 extracellular J0 J NADH NAD+ acetaldehyde/ pyruvate (S4) glucose (S1) ethanol r4 intracellular ATP (A3) r1 ADP (A2) ATP r3 r5 NAD+ (N1) NADH (N2) ADP NAD+ NADH G3P/DHP (S2) glycerol 1,3-BPG (S3) r6 r2 YEAST METABOLISM • BIOCHEMICAL REACTOR (ETHANOL)

23. MODEL COMPONENTS • Intracellular concentrations • Intermediates: S1, S2, S3, S4 • Reducing capacity (NADH): N2 • Energy capacity (ATP): A3 • Mass action kinetics for r2-r6 • Mass action kinetics and ATPinhibition for r1

24. Dynamic Model Equations • Mass balances • Conserved metabolites • MATRIX

25. REVIEW OF OBJECTIVES FOR CONTROL SYSTEMS PLANT OBJECTIVES - OVERALL PRODUCTION FROM THE FACILITY COMPONENT OBJECTIVES -INDIVIDUAL STEPS IN THE PROCESS PROVISION FOR OPERATOR CONTROL OPTIMIZATION OF OPERATIONS

26. PLANT OPERATIONAL OBJECTIVES • ENVIRONMENTAL PROTECTION • MINIMIZE EMISSIONS FROM PROCESS UPSETS • RELIABLE OPERATION OF ALL POLLUTION CONTROL EQUIPMENT • VENTS • FLARES • SCRUBBERS • PRESSURE RELIEF http://www.corrocare.com/air_pollution_control_equipment.html

27. PLANT OPERATIONAL OBJECTIVES • FLEXIBILITY - DYNAMIC RESPONSE • SYSTEM TO ADJUST AUTOMATICALLY TO ANTICIPATED CHANGES IN: • PRODUCTION RATES • QUALITY SPECIFICATIONS • COMPOSITIONS OF FEED • INTERMEDIATE STREAMS

28. PLANT OPERATIONAL OBJECTIVES • USER FRIENDLY OPERATOR INTERFACE • MINIMIZE NUMBER OF VARIABLES NECESSARY TO CONFIRM THE PROCESS STATUS • DESIGN THE SYSTEM SO THE “NATURAL” OPERATOR REACTION TO PROCESS VARIATIONS IS ANTICIPATED • PROVIDE AN INFORMATION INTERFACE FOR OPERATION/ENGINEERING

29. PLANT OPERATIONAL OBJECTIVES • MONITORING AND OPTIMIZATION • DETERMINE THE CONTROL LIMITS FOR THE PROCESS • DETERMINE THE OPTIONS FOR COST REDUCTION

30. PLANT OPERATIONAL OBJECTIVES • STARTUP/SHUTDOWN • ROUTINE START-UP CONTROL • MINIMIZE START-UP TIMES • ROUTINE SHUTDOWN CONTROL • RESPOND TO SHORT TERM SHUTDOWNS WITH MINIMUM RESTART TIME • SAFE EMERGENCY SHUTDOWN

31. PLANT OPERATIONAL OBJECTIVES • EQUIPMENT PROTECTION • INTEGRATE DESIGN SO FAILURE OF ONE PART OF THE FACILITY DOES NOT TRANSFER TO FAILURE IN ANOTHER PART • INTERLOCK SYSTEMS TO PREVENT EQUIPMENT DAMAGE IN THE EVENT OF A PROCESS INTERRUPTION

32. COMPONENT OPERATIONAL OBJECTIVES. • SIMILAR TO PLANT OBJECTIVES • COMPONENT RELIABILITY • MINIMIZE COMPONENT DEGRADATION OR FAILURE. • REDUNDANCY WHEN PRACTICAL. • MINIMAL LOCAL ADJUSTMENT FOR NORMAL PROCESS VARIATIONS

33. COMPONENT OPERATIONAL OBJECTIVES. • SAFE OPERATION - • COMPONENT DESIGNS FOR SAFE OPERATION WITHIN THE ANTICIPATED OPERATING RANGES FOR THE PROCESS • RELIEF SYSTEMS TO AVOID CATASTROPHIC FAILURE IF THE PROCESS EXCEEDS THE SAFE OPERATING RANGES.

34. COMPONENT OPERATIONAL OBJECTIVES. • ENVIRONMENTAL PROTECTION • DESIGNS TO AVOID LEAKS OF PROCESS MEDIA • DESIGNS TO INDICATE LEAKS OF PROCESS MEDIA • DESIGNS TO AVOID SUPERSONIC FLUID CONDITIONS OR OTHER FORMS OF SOUND POLLUTION

35. COMPONENT OPERATIONAL OBJECTIVES. • EASE OF OPERATION • LOCAL OPERATION • REMOTE OPERATION • MONITORS • TO DETERMINE CURRENT STATUS OF COMPONENT • TO DETERMINE THE NEED FOR MAINTENANCE OR REPLACEMENT

36. COMPONENT OPERATIONAL OBJECTIVES. • PROVIDE THE OPERATOR WITH ADEQUATE INFORMATION • FOR ROUTINE START-UP AND SHUTDOWN FROM A REMOTE LOCATION. • FOR LOCAL OPERATION DURING STARTUP OR SHUTDOWN

37. COMPONENT OPERATIONAL OBJECTIVES. • EQUIPMENT PROTECTION • DESIGNS TO INDICATE OUT-OF-RANGE CONDITIONS SO OPERATORS CAN TAKE PROPER ACTION • DESIGNS TO INITIATE AUTOMATIC SHUTDOWN SEQUENCES FOR OUT-OFCONTROL CONDITIONS.

38. TYPES OF CONTROL http://www.controlloopfoundation.com/continuous-chemical-reactor-process.aspx http://www.controlloopfoundation.com/batch-chemical-reactor-workspace.aspx CONTINUOUS BATCH SEMI-CONTINUOUS COMBINATIONS OF THE ABOVE