Studies on computer aided modelling, simulation and optimization in process development

This paper is based on eight publications on computer aided modelling, simulation and optimization in process development. Modelling, simulation and optimization of whole process plants are discussed. The methods by which opponent requirements in the plant are taken into account are reviewed. Similarly the subject of process synthesis is covered and its importance in process development emphasized. The methods by which process synthesis can be included in optimization problems are discussed. In the process development phase it is common to create many alternative process schemes. Thus there is a need for fast evaluation of the investment costs of these alternatives. It is desirable to use the same tool, a flowsheeting program, to create the process material and energy balances and to carry out the economical evaluation. A comparative study with computer code implementations of investment cost estimation methods was done. Normally such things as process safety, controllability and economics can not be expressed in exact numbers. Therefore to model and to simulate such systems the qualitative variables must be quantisized. One promising method is to use fuzzy sets together with linguistic variables. This paper includes a review article on the use of fuzzy sets and linguistic variables to handle data and knowledge of uncertain and/or qualitative nature. The computer program IFTHEN for modelling of such systems is described. An application demonstrates this methodology and the use of the computer program IFTHEN along with other software on the control and safety system of high pressure polyethene production. Often one of the important issues in the use of modern computer programs developed for plant design is the selection of the most suitable thermodynamic models for the problem in hand. This area is discussed on the basis of the classes of the needed properties. The modelling of slurry polymerization of propene is discussed. A model for the polymerization kinetics was developed. This kinetic model was indicated in a slurry polymerization model of a continuous stirred tank reactor system. This was transferred to a module into a general purpose flowsheeting program. The flowsheeting program has optimization capabilities which were used in this study to find out the most promising starting values for test runs at a full scale plant. The advantages of this kind of modelling, simulation and optimization are reviewed.