Process Systems Engineering Group

Process systems engineering deals with the overall system behaviour and how the individual units should be combined to achieve optimal overall performance. Important topics are multi-scale process modelling, operation and control, design and synthesis, and simulation, statistics and optimization.

The group
The group presently consists of more than 20 people, in addition to about 6 Diploma and project students. The group closely cooperates with other systems-oriented departments at the university, including Engineering Cybernetics, Energy and Process Engineering, and Industrial Ecology, and also with SINTEF. The process systems engineering activity at NTNU (PROST) holds high international standards and was already in 1994 recognized as a strong-point center, both by NTNU and SINTEF.

At present, the main activities in the group are within process control and process modelling including efficient thermodynamic calculations. A new area from 2008 is systems biology, where Nadi Bar started as Associate professor in January 2008.

Process control
Industrial use of advanced process control increases rapidly, and candidates who combine process knowledge and control expertise are in high demand in industry. Control is an enabling technology, thus basic for any industry-based society. The use of advanced control is transforming industries previously regarded as "lowtech" into "high-tech". In process control (Skogestad, Preisig), the objective of the research is to develop simple yet rigorous tools to solve problems significant to industrial applications (of engineering significance).

Plantwide control
Up to now, the design of the overall "plant-wide" control structure has been based on engineering experience and intuition, whilst the aim has been to develop rigorous techniques. The concept of "self-optimizing control" provides a basis for linking economic optimization and control (Skogestad). For example, for a marathon runner, the heart rate may be a good "self-optimizing" variable that may be kept constant in spite of uncertainty. Control is done in a hierarchical construct. At the bottom of the hierarchy, the main issue is to "stabilize" the operation and follow the setpoints provided by the layer above. Further up in the hierarchy one finds optimising control co-ordinating the control of units and plants. A special case is sequential control, which is used to implement recipes in batch operations but also is the basics of handling start-up and shut-down as well as all fault and emergency handling. Another important concept is controllability, which links control and design. Here the main focus is on applications, which currently include reactor and recycle processes, distillation columns, gas processing plants, cooling cycles including liquefied natural gas (LNG) plants, low-temperature polymer fuel cells and anti-slug control.

Other control activites
Small-scale experimental rigs have been built to study anti-slug control and novel distillation arrangements. In most cases, control is an "add-on" to enable and improve operation, but the anti-slug rig demonstrates how control in some cases can be used to operate the system in a completely different manner. 10 The Kaibel distillation column (see picture) is 6 meter high and 5 cm in diameter and can be used to study "thermally coupled" columns, including the threeproduct Petlyuk column and the four-product Kaibel column. The research in this area will be strengthened in 2008, through a grant from the research council where 2 new PhD students will be hired. Dr. Ivar Halvorsen from SINTEF and Sigurd Skogestad manage this integrated distillation project. The group also has an automatic drink mixer, which is used for demonstration purposes and to study sequence control based on automata theory (Preisig).

Process modelling
Small-scale experimental rigs have been built to study anti-slug control and novel distillation arrangements. In most cases, control is an "add-on" to enable and improve operation, but the anti-slug rig demonstrates how control in some cases can be used to operate the system in a completely different manner. 10 The Kaibel distillation column (see picture) is 6 meter high and 5 cm in diameter and can be used to study "thermally coupled" columns, including the threeproduct Petlyuk column and the four-product Kaibel column. The research in this area will be strengthened in 2008, through a grant from the research council where 2 new PhD students will be hired. Dr. Ivar Halvorsen from SINTEF and Sigurd Skogestad manage this integrated distillation project. The group also has an automatic drink mixer, which is used for demonstration purposes and to study sequence control based on automata theory (Preisig).

The fourth generation of a high-level modelling tool is presently being developed (Preisig), which we aim to apply to large-scale plants, including the Mongstad refinery. It incorporates object-oriented tools for efficient thermodynamic modelling, which extend into the efficient computation of thermodynamic information. Rather than a traditional implementation of activity or fugacity coefficients, emphasis is put on the use of structured equation sets governed by thermodynamic consistency rules (Haug-Warberg). The thermodynamic models are implemented in symbolic form with automatic differentiation capabilities and serves as the basis of several industrial strength simulations (YASIM, CADAS) and energy accounting tools (HERE) in cooperation with Norsk Hydro and Yara. A primary aspect of thermodynamic (and other physics) modelling is the required consistency of physical units. We have a procedure to obtain self-consistent models, including automatic generation of gradients. This technique has so far been tested up to sixth order gradients, which are needed for higher-order critical point calculations.

Statistics
The model generally needs to be fitted to experimental data, and the group has always has a strong focus on statistical methods and experimental design (Hertzberg). Although Terje retired as professor in 2007, he is still active in this area, and in particular, in teaching. Unfortunately, professor Kim Esbensen had to discontinue his service as Adjunct Professor (professor II) because of heavy work load.

Systems Biology and Bioinformatics
The group (Skjøndal-Bar) is part of the new Systems biology Center in the Faculty of Natural Science (NT) at NTNU. The group research area includes (1) modeling and analysis of whole body growth of vertebrates, including adipose cells, muscle growth, nutrition pathways and metabolic models. This project is applied in aquaculture sciences, with a dynamic model that predicts body mass and composition in Atlantic salmon. (2) Modeling, analysis and control of the process of gene expression in Eukaryotic and prokaryotic cells, including translational initiation regulation, elongation and transcription. This project has many applications, from controlling production of proteins with medical and industrial importance to cancer research. (3) Mathematical (dynamic) model of Recombinant protein expression that predicts cellular network response. The center for systems biology (http://www.ntnu.edu/biotechnology/systembio) is a new strategic unit of the Faculty of Natural Science and Technology, integrating three professors from different departments (Biology, Biotechnology and Chemical Engineering), allowing efficient multi-disciplinary work (data mining, structuring, modeling, analysis and control in biology).

Funding
Comes from the Norwegian Research Council, the Gas Technology Center at NTNU and SINTEF, from industry (Statoil, Gassco, Hydro) and from the EU (Promatch program).

Contact information

Illustrasjonsbilde/FOTO

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