Dynamics Seminar Section 3 Process Control John Edwards, P&I Design Ltd August, 2014 www.chemstations.com 1

PROCESS CONTROL SYSTEMS COURSE OBJECTIVES REVIEW Session Objectives are to study Feedback Control and Control Loop Structure Multiple Control Loops Appreciation of Basic Instrumentation Controller Equations and Control Modes Control Loop Behavior Control Valve Flowsheet Integration Control Loop Dynamics - Dead Time – Capacity – Resistance Appreciation of Behavior of Common Control Loops CHEMCAD Control Models Dynamic Vessel Control Loop Tuning SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk

PROCESS CONTROL FEEDBACK CONTROL INCREASES IMBALANCE CONTROL RUNAWAY RESTORES BALANCE CONTROL STABILITY PROCESS CONTROLLER Set Point (r) Manipulated Variable (m) Controlled Variable (c) Error (e) POSITIVE FEEDBACK NEGATIVE FEEDBACK SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk

PROCESS CONTROL CONTROL LOOP ACTION As level increases above Set Point Inlet valve must close so control signal decreases Increasing Input - Decreasing Output REVERSE ACTION Signal to Open Set Point Signal to Open As level increases above SP Outlet valve must open so control signal increases Increasing Input - Increasing Output DIRECT ACTION SIMULATION SUITE CHEMCAD SOFTWARE Signal to Open Fail Closed Valve Signal to Close Fail Open Valve www.chemstations.com www.chemcad.co.uk

PROCESS CONTROL CONTROL LOOP CONFIGURATION FUNCTIONS & SIGNALS LOCATIONS & TAGGING LOOP SCHEMATIC CONTROL CONVERT MEASURE CONTROL DEVICE Thermocouple mV Resistance bulb Ω Transmitter 4-20 mA Transmitter 0.2-1.0 bar Characterise Measurement Linear 4-20 mA Signal 4-20 mA Signal Thermocouple Curve (mV/I) Square Root Extraction (√) Pneumatic to Current (I/P) Valve Actuator 4-20 mA I/P 4-20 mA to 0.2-1 bar Valve Actuator 0.2-1 bar Positioner 0.2-1 bar XY TT 01 CV XIC Field Mounted Equipment Room Control Room c 4-20 mA XIC r e Measurement Transmitter 0 - 100ºC Control Valve Thyristor TT 01 CV m XY Signal Converter Controller SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk

PROCESS CONTROL MULTIPLE CONTROL LOOP STRUCTURE Tx XIC CV Single Primary Cascade Ch6, p154 Secondary FT RatioCh6, p160 Ratio RR FIC Split Range Valves Single Valve Auto SelectCh6, p167 Squeaky wheel gets the grease Auto selection of controlled variable < or > Hi Lo Select Ratio of controlled flow to wild flow Wild Controlled Secondary Primary AdaptiveCh6, p170 PID Adjust Adapts - models needs of process SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL CONTROL MODES & RELATIONSHIP CRYOGENIC BATCH REACTOR OPTIMISATION Proportional (P) P = PB % b =output bias m = b for e = 0 Proportional + Integral (PI) R = integral time (min) dm/dt = e/R P↓ Gain↑ Decreasing P Increases ∆m R↓ dm/dt↑ Never set R faster than process τ + τd www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL CONTROL MODES & RELATIONSHIP CRYOGENIC BATCH REACTOR OPTIMISATION Proportional + Derivative (PD) D =derivative time (min) Note D↑ dm/dt↑ Use D when sustained error End point control: pH – target temperature Proportional + Integral + Derivative (PID) 3Mode Never D on noisy processes: Flow – Level – Liquid Pressure Low R on fast processes: Flow – Liquid Pressure High R on slow processes: Batch reactor temperature www.chemstations.com www.chemstations.net www.chemcad.co.uk

PROCESS CONTROL COMMON LOOP PROPERTIES www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com PROCESS CONTROL COMMON LOOP PROPERTIES Section 3 page 49 COMMON LOOP CHARACTERISTICS & TUNING PARAMETER RANGES Ch3, Table 3.3 PARAMETER CHARACTERISTIC P (%) I (min) D (min) FLOW FAST - NOISY 50 - 500 0.05 - 2 NO PRESSURE (LIQUID) FAST - NOISY 50 - 200 COMPOSITION (GAS) 50 – 500 0.05 – 2 LEVEL SLOW→FAST - NOISY 5 – 100 SOMETIMES TEMPERATURE SLOW - STEADY 10 – 100 2 – 120 I/4 < D > I/2 COMPOSITION (LIQUID) 10 - 200 PRESSURE (GAS) 1 - 5 UNNECCESSARY VAPOR PRESSURE 10 - 100 2 - 120 CONTROL MODES P (%) Ti (min) Td (min) P 2 Pu P + I 2.2 Pu Tu / 1.2 P + I + D 1.6 Pu Tu / 2.0 Tu / 8.0 = Ti /4 Pu measurement starts to oscillate at constant amplitude Tu for small SP changes

DYNAMIC SIMULATION INDIRECT FLOW REGULATION www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com DYNAMIC SIMULATION INDIRECT FLOW REGULATION CVAL can control flow directly ONLY following CVAL inside a flowsheet indirect flow regulation is required CVAL calculates flow from: Pressure drop(dp)-Valve position(%)-Valve characteristic(Equal%-Linear) CVAL inside a flowsheet it cannot maintain a mass balance!! CVAL calculated flow is passed to an upstream UnitOp, to force the inlet valve flow to match the calculated (outlet) flow. UnitOps suitable: Divider - Dynamic Vessel & Column - Batch Reactor – Stream Reference CORRECTLY SIZED VALVE CRITICAL TO SUCCESS OF SIMULATION

DYNAMIC SIMULATION INDIRECT FLOW DIVIDER www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com DYNAMIC SIMULATION INDIRECT FLOW DIVIDER Indirect Flow Divider D3.03 page 63 Divider Output to Stream 7 is referred to Output Stream 2 (Numbering form top) for Control Valve feedback variable Output 1 Output 2

DYNAMIC SIMULATION INDIRECT FLOW REGULATION www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com DYNAMIC SIMULATION INDIRECT FLOW REGULATION

DYNAMIC SIMULATION CONTROLLER SET UP www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com DYNAMIC SIMULATION CONTROLLER SET UP MEASUREMENT LINEAR 0 to 50000 kg/h SIGNAL 4.0 to 20 mA INC FLOW ↑ INC SIGNAL ↑ CONTROLLER ACTION REVERSE INC FLOW ↑ DEC OUTPUT ↓ FOR FAIL CLOSED VALVE SIGNAL TO OPEN (S/O) IF FAIL OPEN VALVE (S/C) INC FLOW ↑ DEC OUTPUT ↑

DYNAMIC SIMULATION 3 WAY FLOW DIVERTING www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com DYNAMIC SIMULATION 3 WAY FLOW DIVERTING Indirect Flow Divider 2 D 3.03-1 page 65

DYNAMIC VESSEL LEVEL CONTROL INLET FLOW CONTROL www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com DYNAMIC VESSEL LEVEL CONTROL INLET FLOW CONTROL Section 3 page 67 D3.04 page 67 Control liquid level at 2m, initial state, in vessel 3(D 1.2m H 4.8m) Constant supply of water 4000 kg/h Variable demand of water on outlet controlled by Ramp 5 Draw from scratch

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION PROBLEM STATEMENT CRYOGENIC BATCH REACTOR OPTIMISATION Component - Water Thermodynamics - K : Vap, H : Late Initial Feed Flow = 4000 kg/hr, T = 20 C, P = 4 bar Initial Liquid level = 2 m Water demand schedule – 0 –10 minutes at 4000 kg/hr 10 – 15 minutes at 4000 to 0 kg/hr ramped 15 – 20 minutes at 0 kg/hr 20 – 25 minutes at 16000 kg/hr 25 – 40 minutes at 4000 kg/hr www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION PROCESS DEMAND CRYOGENIC BATCH REACTOR OPTIMISATION www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION DVSL CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION Standard Dimensions Initial Conditions Method Vessel Mode Fixed Pressure 3 bar www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL CONTROLLER CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 page 67 D 3.04 page 67 LEVEL MEASUREMENT LINEAR 0.5 to 4.5 metre SIGNAL 4.0 to 20 mA CONTROLLER ACTION DIRECT INC LEVEL ↑ INC OUTPUT ↑ FAIL CLOSED VALVE ON OUTLET (OPENS) FAIL OPEN VALVE ON INLET (CLOSES) Direct Action - Increasing Input gives Increasing Output e = X – Xset Reverse Action - Increasing Input gives Decreasing Output e = Xset – X www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION DVSL CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION Specify Inlet & Outlet Flows Specify Composition & Conditions of initial contents www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION CONTROLLER SET UP CRYOGENIC BATCH REACTOR OPTIMISATION Sensor Measured Object Set Point Desired Value 2m Measurement 1.5m to 3.5 m for 4 to 20 mA signal Control Settings Action Inc Level Inc Output www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION CONTROL VALVE SET UP CRYOGENIC BATCH REACTOR OPTIMISATION Rangeability now typically 30 to 50 Fail Closed Valve Signal to Open www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION SET INITIAL CONDITIONS CRYOGENIC BATCH REACTOR OPTIMISATION Set Feed to T = 20 degC; P = 4 bar; F = 4000 kg/hr Run Control Valve and Controller in Steady State www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION SET DYNAMIC RUN CONDITIONS CRYOGENIC BATCH REACTOR OPTIMISATION Switch to dynamic mode under convergence Set Run Time to 60 minutes with 0.5 minute step size Record desired streams Record desired unit operations Select Run Time plot options Run from Initial State Plot results www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION CONTROLLER TUNING CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 page 57 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL LEVEL CONTROL OUTLET FLOW CONTROL CRYOGENIC BATCH REACTOR OPTIMISATION D3.05 page 73 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION PROBLEM SUMMARY CRYOGENIC BATCH REACTOR OPTIMISATION Component – Water Thermodynamics - K : Vap, H : Late Initial Feed Flow = 4000 kg/hr, T = 20 C, P = 4 bar Initial Liquid Level Empty Water demand schedule – Feed ramped to 16000 kg/hr, held for 10 minutes and then returned to 4000 kg/hr www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION DVSL CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION DVSL CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION Liquid flow out is set by CV 1 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION CONTROLLER CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION Measurement 1 to 5 m for 4 to 20 mA Direct Action Inc - Inc www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION RESIZE CONTROL VALVE CRYOGENIC BATCH REACTOR OPTIMISATION Flowrate = 25000 kg/hr Outlet P = 1.8 bar www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION CONTROL VALVE CONFIGURATION CRYOGENIC BATCH REACTOR OPTIMISATION Note: There is no need to fill in the “Optional mass…” option when valve follows dynamic vessel. www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION DYNAMIC VESSEL SIMULATION PROCESS INPUT SCHEDULE CRYOGENIC BATCH REACTOR OPTIMISATION www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL DEAD TIME CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.07 page 87 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL CAPACITY CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.08 page 88 Run Time min Tank Level m www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL CAPACITY CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.08 page 88 Tank Level m Run Time min Fixed Position 47.5% Flow Change 15 to 20 m3/h Off τ1 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL DISPLACER LEVEL CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.09 page 89 Period is function of wetted surface length Throttling displacer valves reduces amplitude allowing narrower PB www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL TANK BALANCING CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.10 page 90 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL GAS PRESSURE CONTROL CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.11page 91 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL FLOW CONTROL LEVEL CUT BACK CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.12page 92 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL TRAINING SIMULATOR CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.13page 93 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL TRAINING SIMULATOR CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.13page 80 Real Time Step 1.0m Simulation Time 0.1m www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL CONTROLLER TUNING CRYOGENIC BATCH REACTOR OPTIMISATION Section 3 D3.14page 94 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL HEAT EXCHANGER CONTROL CRYOGENIC BATCH REACTOR OPTIMISATION Section 4 D4.01page 99 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL HEAT EXCHANGER CONTROL CRYOGENIC BATCH REACTOR OPTIMISATION Section 4 D4.02page 99 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL SHELL PLATE HEAT EXCHANGER CONTROL CRYOGENIC BATCH REACTOR OPTIMISATION Section 4 D4.03page 100 www.chemstations.com www.chemstations.net www.chemcad.co.uk

CRYOGENIC BATCH REACTOR OPTIMISATION PROCESS CONTROL SHELL PLATE HEAT EXCHANGER CONTROL CRYOGENIC BATCH REACTOR OPTIMISATION Section 4 D4.03page 100 www.chemstations.com www.chemstations.net www.chemcad.co.uk

PROCESS CONTROL SESSION REVIEW www.chemcad.co.uk SIMULATION SUITE CHEMCAD SOFTWARE PROCESS CONTROL SESSION REVIEW Session studied Dynamic Simulation Vessel set up procedure Ramp for Process Input and Demand schedules Control Valve Action and Failure mode Control Valve Flow Characteristic influence Level Control Loop behaviour Level Control Loop tuning Dynamic Results generation www.chemstations.com