Title: Dynamic and Global Optimisation of Processes

Partners

• Slovak University of Technology in Bratislava, Faculty of Chemical and Food Technology, Department of Inform. Eng. and Process Control (M. Fikar, E. Miklovicova, K. Calik, T. Hirmajer, M. Cizniar)
• Institut National Polytechnique de Lorraine (INPL) - Ecole Nationale Supérieure des Industries Chimiques (ENSIC) (M. A. Latifi, M. Daroux, R. Guimaraes, D. Salhi)

Date: 2004-2005

Objectives, project description, background, proposed research

A majority of chemical, pharmaceutical, and biotechnological products are manufactured in processes that operate in an inherently transient manner rather than at some nominal steady-state. Examples include batch and semi-batch processes, and periodic processes that operate at a cyclic steady state, such as pressure swing absorption and reverse flow reactors. The design of these processes is in essence an exercise of optimal process operation. In particular, batch processes are invariably suitable in a large number of applications in pharmaceutical, biotechnological industries, polymerisation, special chemistry and agro chemistry, or in production of electronic materials. Even in product design or formulation, which is the new emerging paradigm in Chemical Engineering, most of the new products will be manufactured in batch processes, i.e. transient in nature. All of these considerations motivate research on design procedures that optimise the performances of inherently transient processes, particularly batch processes. The most important aspects of this research are closely tied to economical competitiveness, environment, and safety of processes. To understand and master these issues, design and optimal operation of dynamic processes is of the utmost importance.

This research project deals with unsteady-state operation of dynamic processes that are described by a detailed mathematic models, typically with non-linear and differential equations. The optimisation of performances of such processes consists in the determination of optimal profiles of decision variables (temperature, pressure, flow, heat, ...) or optimal parameter values of the dynamic model which optimise (minimise, maximise) a given performance index (time of operation, yield, energy consumption,...), over a time horizon, under specified constraints (environment, process physical limits,...). This kind of problems is known as dynamic optimisation (or open-loop optimal control). Some selected problems include determination of optimal control in batch processes, estimation of optimal kinetic parameters in chemical reactions based on experimental data, determination of optimal control trajectory during set-point change, security analysis of processes, model based predictive control based on continuous model, etc.

Cooperation between LSGC (ENSIC-INPL, Nancy) and Slovak University of Technology in Bratislava started several years ago, when several Slovak researchers spent some time in Nancy in the framework of European projects (TEMPUS), post-doctoral programs (CNRS, Elf Aquitaine), or programs for high quality foreign researchers (Ministère de la Recherche, Région de Lorraine).

Work realised during these stays resulted in development of methods and algorithms for dynamic optimisation applied to refinery processes, distillation columns, small size waste-water treatment plants. The development of a for dynamic optimisation software, i.e. DYNO, was started. This software is currently distributed for exclusively academic purposes and it is being used in France, Slovak Republic, India, Malaysia, USA (NASA),...

Objectives of the cooperation are as follows:

• to enrich the knowledge already acquired until now by developing rigorous methods of dynamic and global optimisation of processes. In fact, it is well known for several years that solutions of dynamic optimisation in chemical engineering and control exhibit numerous local optima. Therefore, due to the non-convexity problems in chemical engineering, it is almost impossible to find the true global optimum and the results obtained are only local in nature. This sub-optimality can have serious consequences on economical, environmental operation, safety, and clearly show importance of the development of global optimisation methods.
• to further develop the software DYNO, namely
  • incorporate methods of global optimisation,
  • improve its robustness and speed by incorporating public domain codes for automatic differentiation (Adifor, Tapenade, ...),
  • broaden its application area by testing it on problems from other domains (biotechnology, mechanical engineering, ...).