Process modelling and simulation have emerged as important tools for detailed study and analysis of chemical processes. In activities such as design, optimization and control of processes, realistic process models, which incorporate physics and chemistry of the process in adequate detail, are becoming almost indispensable. Simulation studies also provide guidance in the development of new processes and can reduce both time and capital investment. A difficulty with process models is that they are based on the state of knowledge and simulation objectives defined at the time of their formulation. In addition, it is not easy to modify process models to incorporate new knowledge as it becomes available and as new needs arise. There IS need, therefore, to use advanced modelling and simulation strategies such that refinements and additional capabilities can be incorporated in the model without disproportionate additional effort. This work presents the framework of one such multipurpose process simulator, MPROSIM, an object-oriented process modelling and simulation environment. Though considerable literature IS vailable on process modelling from a subjective or theoretical viewpoint, very little has been published on application of these ideas on complex industrial-scale processes. This being the focus of the paper, a case study of an object-oriented model for automatic generation of a fluid catalytic cracking unit (FCCU) reactor/regenerator is presented. The utility of the framework is illustrated by demonstrating how the model for FCCU could be fine-tuned both structurally and parametrically to represent the behaviour under changing process operating conditions.