Areas of interest and related main topics

The Process Systems Engineering Group at ISR-Porto recognizes its work in a number of clusters of interest:

Current projects

For the 3-year period of 1999-2001, eight projects or topics of work are in progress. They involve the development of theory, of methods and of tools, within a frame of postgraduate education and training, with a concern of cooperation at international level and with industrial partners. The following most relevant aspects should be mentioned (project codes as in the official report of ISR):

The academic research area for developing models, methods and basic technologies for representing and processing knowledge and for building intelligent knowledge-based systems, is called knowledge engineering. This is seen by a school of thought ( Kasabov, 1996; Kosko, 1992) as a part of the AI area, directed more towards applications. Knowledge Engineering includes both symbolic and numerical frameworks as well as both structured and unstructured forms of knowledge representation.

The objective in this project is to develop and apply hybrid networks, concerning numerical frameworks (fuzzy and neural network solutions) in conjunction with classical forms of knowledge representation (based on the so-called 'first-principles methodologies), to the modelling, optimisation and control of chemical and biochemical processes. It is known that 'first-principles' knowledge alone cannot model all existing knowledge of a process and it is believed that through hybrid structures significant improvement can be achieved in process knowledge representation.

From a theoretical point of view, the group will focus on problems of controllability and stability, and on how to define adaptive (dynamic) hybrid systems.

From the applications point of view, hybrid structures will be applied to the modeling and operation of both chemical (crystallisation) and biochemical (fermentations) industrial processes.

The following is relevant literature concerning this line of work -

1. Kasabov, N.K., Foundations of Neural Networks, Fuzzy Systems and Knowledge Engineering, The MIT Press, Cambridge, London, 1996
2. Kosko, B., Neural Networks and Fuzzy Systems - a Dynamical Systems Approach to Machine Intelligence, Prentice Hall, Englewood Cliffs, NJ, USA, 1992
3. Thomson, M.L., M.A. Kramer, Modeling chemical processes using prior knowledge and neural networks. AIChE J., 40, pp. 1328 - 1340, 1994
4. Schubert, J., R. Simutis, M. Dors, I. Havlik, A. L�bbert, Hybrid Modelling of Yeast Production Processes – Combination of a priori knowledge on Different levels of Sophistication. Chem Eng. Technol., 17, pp. 10-20, 1994
5. Simutis, R., R. Oliveira, M. Manikowski, S. Feyo de Azevedo, A. L�bbert, How to increase the performance of models for process control and optimization. J. Biotechnol., 59, pp. 73-89, 1997
6. Feyo de Azevedo, S., B. Dahm, F.R. Oliveira, Hybrid Modelling of Biochemical Processes: A comparison with the conventional approach. Computers chem. Engn, 21, Suppl., pp. 751-756, 1997

This is a long term cooperation between the two scientific responsibles, which aims at detailed characterisation of basic mechanisms of crystallisation processes. It further includes the most valuable cooperation of Dr. Marie Noelle Pons, from ENSIC-Nancy. Specifically, the characterisation of nucleation and growth rates and the degree of agglomeration represent major scientific information with direct application to the understanding of industrial operation. The work includes a significant experimental component (at laboratory level) and a complex step of data interpretation through image analysis.

An automated method is being developed for the morphology classification of crystals. It combines the analysis of images obtained from an optical microscope and the analysis of the resulting shape descriptors by a discriminant factorial method. Most relevant is the information concerning the influence of impurities on kinetic rates.

The method is being applied to such industrial processes as sugar crystallisation and dicalcium phosphate production.

This is essentially a background action, rather than a scientific project, which is being developed since 1991. The group has developed a process simulator which can run synchronised with real-time, including A/D and D/A interfacing with the environment. The simulator is physically connected to external control systems, serving as a process laboratory for R&D developments in process control. A model-bank keeps being constructed by adding new case-studies. Throughout the years this tool has proved most useful in several M.Sc. and Ph.D theses concluded and in training of control systems.

The simulation and optimisation of complex industrial processes is a subject where a great research effort has been made. During the project, which will clearly extend beyond the three year period, we intend to develop tools for equation oriented optimization, where the decision variables are automatically chosen, removing much of the burden from the designer. Such will require interfacing robust MINLP solvers developed within our research group (the MSGA and MSIMPSA algorithms) with appropriate tearing-partitioning algorithms. Interfacing of these solvers with the ASPEN sequential modular simulator is also a possibility. We will apply these tools to biotechnology processes, whereby the system topology of an industrially important process will be optimised through a MINLP formulation. We will also study the optimum synthesis of reactive distillation columns, whereby the number of theoretical trays and feed location (reaction zones) will be optimised together with the continuous variables. It is expected that this work will result in a viable MINLP simulator/optimiser package that will have a wide field of applicability in the chemical process industries.

The objective of this work is to develop numerically optimized optimized geometries for reverse-flow cyclones with recirculation capabilities, that may be used both for dedusting and acid gas cleaning. A reverse-flow cyclone numerically designed to retain very small particles (< 2 �m), which has been subject to a European Patent Pending process (PT B01D045/12, PE No 99670006 - High Efficiency Ciclones) will receive dry injection of an adequate sorbent (Ca(OH)2), which will react with HCl to produce innocuous solid residues (A.M. Fonseca, J.M. �rf�o and R.L. Salcedo, "Kinetic modeling of the reaction of HCl with solid lime at low temperatures", Ind. Eng. Chem. Res., 37(12), 4570-4576, 1998). The very high collection efficiencies coupled with an adequate residence time of the reacting particles within the gas stream can in principle be achieved by the adoption of a recirculating scheme with the use of a venturi/straight-through secondary cyclone. The experimental laboratory-scale facility will be designed to promote a smooth transition towards a pilot-scale unit for testing under typical industrial conditions. The recirculating cyclones have been recently subject of a Portuguese Patent Pending Process 102392M dated 99.12.13.

This is a project of chemical engineering, resulting from the group's long-standing cooperation with RAR sugar refinery in Porto. It is essentially a detailed experimental work where the process sensitivity to basically all its input variables will be tested and characterised.

This activity corresponds to a well defined contract work with an industrial company. It is to be developed in cooperation with the Control Systems and Technology Group of the Institute for Systems and Robotics-Porto. The main objectives are the development and implementation (on the industrial ovens) of a robust control strategy for multivariable systems based on a state-space representation of the process. Of no less importance are the developments concerning off-line and on-line model identification algorithms.