This report deals with the transient behaviour of process systems such as those normally encountered by the chemical engineer. Two competing approaches for the numerical solution of this problem are described. The first is an "equation oriented" approach, and the second is an "equipment oriented11 or "modular" approach. The concept of modularity is discussed, and a brief presentation of its advantages is given. A program DYNSYS-B was written to apply the modular approach to transient studies. The program employs a predictor-corrector technique to solve the system's differential equations in a sequential fashion. The DYNSYS-8 program was applied to a multicomponent liquid-liquid extraction unit with heat effects and reflux, with the object of evaluating the program and gaining some experience with its use. Based on this study. we believe that the program is readily applied to the solutions of many problems. Some suggestions are made for improving the computation efficiency of the program. / Thesis / Master of Engineering (MEngr)

Traditionally the reactor is recognised as the `heart' of a chemical process system and hence the focus on this part of the system is usually quite detailed. Steam reforming, however, due to the `building block' nature of its reaction products is unusual and generally is perceived as a `utility' to other reaction processes and hence the focus is drawn " towards the 'main' reaction processes of the system. Additionally as a `mature' process, steam reforming is often treated as sufficiently defined for the requirements within the overall chemical process. For both primary and secondary steam reformers several models of varying complexity were developed which allowed assessment of issues raised about previous models and model improvements; drawing on the advancements in modelling that have not only allowed the possibility of increasing the scope of simulations but also increased confidence in the simulation results. Despite the complex nature of the steam reforming systems, a surprisingly simplistic model is demonstrated to perform well, however, to improve on existing designs and maximise the capability of current designs it is shown that more complex models are required. After model development the natural course is to optimisation. This is a powerful tool which must be used carefully as significant issues remain around its employment. Despite the remaining concerns, some simple optimisation cases showed the potential of the models developed in this work and although not exhaustive demonstrated the benefits of optimisation.

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