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Page 1
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• About You:- Your name?- Your job role?- How you currently use modeling tools?- Your experience with UniSim Design?- The one thing that you want to take away from this course?
• About Me?- My Name- My Experience
Page 2
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• UniSim® Design can bring the steady state and dynamic worlds together
- with Integrated Modeling:
a steady state case can easily be converted to a dynamic one you can use the same program for both steady state and dynamicsimulationssteady state cases do not have to be rebuilt in order to create the dynamic simulation
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Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• Course Materials – this is your own copy to keep
• Introduction to course area- Location of Washrooms- Coffee/Tea and refreshments- Arrangements for lunch- Use of Cellular phones, please be considerate.
• Timing Issues- 9:00 – 17:00- Lunch: 12:00 – 13:00- If we return from breaks on time, we should be able to stay
on track for a 17:00 finish.
Page 6
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
Day One
Day Two
Day Three
Page 9
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
• Every Fluid Package needs a component list and a property package.
• The Peng-Robinson EOS has been optimized for use with most “Oil & Gas” applications in UniSim Design.
• It is very important the right property package is chosen. The accuracy of the model depends on this choice.
• The “Master” component list is a superset of all components in the other lists. It can not be selected as the component list for use in a fluid package.
• Fluid Packages can be exported and shared with colleagues.
Page 13
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• There are four methods for adding objects- Flowsheet Menu, - F11 or F12,- Object Palette,- Workbook
• Streams can also be added by typing their name into the connections page for a unit operation. - Use this option carefully as a simple typo will result in a
undesired connection.
• To connect objects, use the drop-down lists or the PFD attach mode
• Hold down the Ctrl key to quick access this mode
Page 14
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (Reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
Page 16
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• The Dynamic Solver in UniSim® Design is not the same as the Steady State Solver
• In Dynamics UniSim Design uses a hybrid solver:- Integrates numerically over time- Solves simultaneous equations for pressure-flow network- + Sequential modular solution of
Energy BalancesControl / Logic CalculationsComposition
• Integration of pressures-flow network, enthalpies and composition
- Four different time step sizes:- Pressure-flow network ← smallest time step- Control & Logic ← smallest time step- Enthalpy balances ← intermediate time step- Composition calculations ← largest time step
(tend to changemore gradually)
• Integration Method- Fully Implicit Euler integration method- Has characteristics of being stable and fast
• One P or F spec must be made on every boundary streams (feeds/product):- Use P Specs on boundary streams attached to valves and other
resistance equation operations- Use F Specs on boundary streams attached to all other operations
• Before a dynamic simulation can be run, a pressure gradient must be established through the entire flowsheet
• UniSim® Design will use the defined pressure-flow specifications and the pressure-flow equations from the unit operations to solve the pressure-flow network
• A very important point to remember: - Pay attention to the pressure gradient in your flow sheet:
No Pressure Gradient = NO FLOWPositive Pressure Gradient = INVERSE OR NEGATIVE FLOW
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
• Learning Objectives- Size equipment- Define pressure-flow specifications- Add Controllers- Add Strip Charts- Run a simple dynamic simulation and observe the role of the
various controllers
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Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• Cascade control is a common control technique loop that uses two controllers within one feedback loop
• The two controllers are not independent, but linked together with the ‘primary’ controller setting the SP for the ‘secondary’controller
• Cascade controller can improve the dynamic response and controllability of a process that has considerable dead time, orwhere the time response of the primary loop is very large
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix
• Default nozzle settings:- Nozzle location as percentage
of vessel height:Vapour product 100%Feed 50%Liquid product 0%
- Nozzle diameter: 5% of vessel height/diameter
• Outlet product vapour phase is determined by phase level in nozzle
Vapour product nozzle with 50% liquid coverage will have VF=0.5Heavy liquid product nozzle with 50% light liquid coverage will have VF=0 but liquid will be 50% light liquid
• Nozzles are always in the vessel side wall
What if the real vessel has nozzles in the bottom surface?
Model the nozzle at 0% height with very small diameter
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Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
High purity condensersColumn sumpsGas (N2, fuel gas) blanket pressure control
• Nozzle EfficiencyControls the amount of feed which takes part in equilibrium flashTypically only vapour value is changedFeed nozzle used with forward flowProduct nozzle used with reverse flow
Page 41
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
- Add unit operations and controllers in Dynamics mode- Make necessary P-F Specs for the system- Implement appropriate control strategies- Install a relief valve
Page 43
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• Digital Point Operation- Translates PV into Boolean input- Or connects Boolean output to
valve opening On/Off ControllerOptional input and output to model equipmentManual or Automatic modesOutput can be pulse (pulse On or pulse Off) or latchedOptional dead band (above and/or below threshold)
- NB Use valve Actuator Digital Position as OP
Page 46
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• Enable Liquid ServiceSolves the valve opening simultaneously with pressure and flow.Provides greater stability for liquid service and fast transient vapour systems
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
Page 50
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
• Its easiest to model the column in steady state first…
• Hence 2 choices:
• 1. Convert the whole model from dynamics back to steady state- Issues/Concerns:
Steady state and dynamic solvers are different, need to change the dynamic model to prepare it for steady stateNot generally the best idea if working with a very large dynamic model
• 2. Create a new steady state case and build the column there, then copy/paste into dyn model- Issues/Concerns:
Do not need to make any changes to the dynamic model
Page 55
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Start with a lined out dynamic model2. Add TEG to the component list3. Export the fluid package4. Create a new case using the exported Fluid
Package5. Create a copy of the column feed stream in the
new case• Will have to manually copy the temperature, pressure, flow and
composition
6. Build the column and sump in the new case• Build the column in steady state and then copy?• Build the column in steady state, convert to dynamics and then
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (Reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
Page 60
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
• Combination of Inputs cause Outputs to be triggered- This example duplicates the functionality of the Event Scheduler Module- X = Cause Output to Trip when Input goes to 0- R = Reset Output when Input goes to 1
- 0 = Tripped, 1 = Healthy
- Set Trip, High and Invert options
Page 61
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use
1. Getting Started in Steady State2. Pressure Flow Solver and Dynamic Concepts3. Transitioning from Steady State to Dynamics4. Control Theory Review (reading only)5. Dynamic Details6. Expanding the Model7. Compressor8. TEG Dehydration Tower9. Event Scheduler10.Cause and Effect Matrix11.Building a Fired Heater
Page 62
Dynamic Modeling using UniSim® Design4528 (UDS-310)Slides for student use