Simulation
Simulation is used to optimize plant design and control concepts regarding safety, availability and economic efficiency. It allows the analysis of your plant or control concept at the beginning of the design phase. Dynamic simulation models can be used to detect and avoid critical operating states.
Fields of application
- Simulation of processes, for process optimization
- Simulation of control concepts, for control optimization
- Systematic search for critical operating states of a process
- Plant simulation or incident simulation for operator training
Control design and optimization using dynamic simulation
Reliable models of the process allow analysis, simulation, design of the control concept and testing. During the design phase of new plants comprehensive simulation studies are often required by contract.
These studies may be used to compare different process design concepts with regard to process dynamics and critical operating states. They also allow design, testing and optimization of the process control concept.
One purpose of simulation studies is to anticipate critical operating modes possible on the real process. The control concept design allows for these critical modes and tries to find the optimal solution regarding safety, reliability and efficiency. Simulation of the control concept determines system behaviour and controllability of the process. A correct mathematical reproduction of the complex industrial process is required to allow the simulation of a wide range of operation and control concepts.
Simulation model
A fundamental requirement for realistic process simulation is a correct mathematical model of the process. This always demands a compromise between required precision of the simulation and effort for creating and computing the model. The theoretical, highly complex mathematical model must be simplified for use, without unacceptably compromising the quality of the simulation. Analysis of the system operation of process control plants often uses simulation models of the complete machine train, the process and of all control functions.
When designing a dynamic simulation model the complex plant is divided into modules or segments. An extensive library supports modelling with modules for: valves, flaps, pipes, tanks, compressors, steam turbines, gas turbines and generators. The use of macro structures and multiple simulation levels further supports the conversion from plant design to simulation model. Macro structures allow the repeated use of models and subsystems.
Simulation example – FCC plant
An FCC plant cycles catalyst between reactor and regenerator. In the reactor the catalyst accumulates coke. In the regenerator the coke is burned off to flue gas, thus regenerating the catalyst. The flue gas can be used to drive a turbo expander and generator for energy recovery.
The process requires precise pressure control for reactor and regenerator, automatic start-up and shut-down of the turbo expander and load shedding control (switching from grid mode to island mode) under full load for the generator. A complex control concept, covering all operating modes, was designed and tested with a simulation model.
A dynamic simulation model of the complete flue gas system was developed to allow detailed analysis, with special attention to external disturbances (load shedding, expander trip). This model was used to optimize the control concept for highest efficiency, even under worst operating conditions.
The simulation uses the same programming language as the actual control program. Intricate and error prone translation between control software and simulation is not necessary.
Use of the simulation model for an existing FCC plant allowed reduction of down-time for the implementation of a turbo expander to a few hours. Extensive and expensive field tests to optimize the control during commissioning were not required.
Simulation for operator training
In addition to design of process and control concept, simulation can also be used for training. Operators may familiarize themselves with process or machine, using incident simulation to train the correct response to emergencies. The simulation can also be integrated into central control systems (DCS, HMI). The programming tool TurWin includes full support for process simulation, controller programming, process visualisation and open communication interfaces.
Process data recording, or data logging, available for normal process visualisation also works for simulation. This allows recording of all relevant simulation data for extensive analysis.
An integrated play-back function supports the use of recorded data as input signals for simulation. When recorded data of a real machine is available it can be used to re-enact a machine incident, either to optimize the control behaviour or to train operators for the correct response.