Rigorous Dynamic Simulation Research Articles

The use of different modelling approaches and tools to support research activities: An industrial example

The use of mathematical modelling to support and interpretate the results of a research project has become an essential part of the engineering activities in an R&D company. As a consequence different approaches and tools have to be developed and used in order to achieve better understanding of the phenomena involved and correctly address the experimental and design activities. The availability of oversimplified or rigorous models, steady-state or dynamic simulation, numerical fluid dynamics or finite-element codes increase the number of tools to be chosen, depending on the scope of the research phase involved. Therefore the engineering group of an R&D company, developing the knowledge for using all these approaches, would be able to choose step by step the most appropriate to achieve the goal. An interesting and exhaustive example of this strategy, a research project on the development of Solid Oxide Fuel Cells (SOFC), will be used to illustrate such concepts.

Control Strategy for Heat Integration in Heterogeneous Azeotropic Distillation

The separation of azeotropic mixtures via heterogeneous distillation poses one of the most challenging process control problems. With the help of rigorous dynamic simulations, it has been possible to determine a suitable control strategy which enabled heat integration. First, new steady states for both columns were determined so as to allow operation under revamping conditions. Then, the energy recovery scheme was incorporated and tested. As no integration policy is feasible without proper regulation, the changes in the control policy were ascertained. Finally, the economic benefits were assessed by means of a cash flow analysis.

Analysis of Process Dynamics Using Steady State Flowsheeting Tools

A short-cut method for generating approximate plant-wide dynamic models using flowsheeting data is used in the diagnosis of potential control problems in a reactor-seperator-recycle process. Simplified analysis enables the positive feedback problem and its causes to be identified, and a systematic testing of alternative control configurations to be carried out, without resorting to rigorous dynamic simulation.

Rigorous Dynamic Simulation of Distillation Columns Based on UV-Flash

The paper demonstrates that a rigorous dynamic simulation for distillation columns, including varying pressure and vapor holdup is feasible using a UV-flash approach. A strategy is presented for calculating this flash efficiently when used in dynamic simulation. The paper also considers use of local thermodynamic models combined with look-up tables, where all variables are continuous in time. The results are illustrated on a propane-butane fractionator where the vapor holdup is considerable and should not be neglected.

Dynamic simulation as a tool to integrate process design and process control

Dynamic simulation provides the process design and process control engineer with a highly effective tool to analyze process transients. When applied in the conceptual phase of a new process design, dynamic simualtion can be used to determine the optimum design of a proces by simultaneously considering steady-state economics and plant-wide controllability. A methodology is shown how rigorous dynamic process simulation can be used as a tool to effectively integrate the process design and process control disciplines. Illustration on extractive distillation systems demonstrate that this analysis leads to an optimum economic process design with a robust simple single-input single-output regulatory control scheme that meets process operability requirements.

MODELING, SIMULATION AND CONTROL OF CRUDE TOWERS

Crude towers are one of the most energy consuming, complex distillation columns in a refinery. A mathematical model for the rigorous dynamic simulation of a crude tower is presented. Because of the large dimension, large stiffness and non-linearity of the model, dynamic simulation of a crude tower has proven to be very difficult. In this paper, the Sum of Rates algorithm is shown to be suitable for obtaining the steady states of a crude tower. Once a steady state is approached, the dynamic responses of a crude tower can be simulated by the Bubble Point algorithm. The dynamic simulation predicts strong, one-way interaction among the product streams. Through dynamic simulation, it is shown that the interaction can be eliminated by a decoupler.

Dynamic structural transformations for distillation control configurations

AbstractA control structure transformation is presented that includes the effects of inventory control system dynamics and internal flow dynamics on flows and compositions. This new transformation can be used to predict column dynamic operation for any alternative control structure from the open‐loop model (inventory control only) obtained for a particular control structure (LV). New types of inverse responses are predicted using this technique and verified both by rigorous dynamic simulation and by experimental studies on a pilot‐scale distillation column. These features also can be shown theoretically using a simplified transfer function model.