Using models in different stages of process life-cycle

The use of models in different stages of a process life-cycle is described. These stages are partly overlapping and have feedback between them. The sc ope may range from calculation of mass and energy balances of a single unit operation to large flow sheet simulation and optimization. The novelty of the case at hand or an innovative approach taken may require the developmen t of tailor-made, detailed new models. Sub-problems include choices between competitive theories, mechanistic and empirical approach and the proper de gree of details. The same models should be applicable at different stages a nd for different tasks, such as simulation, optimization, design, experimen t planning etc. Development of the melamine and hydrogen peroxide productio n processes are used as examples. (C) 2000 Elsevier Science Ltd. All rights reserved.