Abstract

Computer-Aided Chemical Engineering is reviewed from its beginnings in the 1950s to the present state in which virtually all chemical engineering is computer-aided. Over 200 computer-based computations routinely undertaken by chemical engineers are listed. Computer-aids are used at every stage from deciding what chemical species to make, through the conceptual design of the processes, the detailed design, the on-line control, optimization and retrofit design, up to the decommissioning. Computer-aids are important for assessing and minimizing environmental impacts and hazards. This chapter does not discuss any of these topics in detail. It concentrates on the design of reliable software and the correct use of software supplied by third parties. Guidance is given for designing software that properly meets the technical requirements of the end users. The program structure and test procedures necessary to validate the software are described. Methods for ensuring that the program properly incorporates the physical models on which it is based are outlined including emphasis on dimensionally consistent programming. The importance of data validation is emphasized. It is further emphasized that these design guidelines apply equally to models written in special-purpose modeling systems as they do to models written in general-purpose computer-programming languages. The elements of numerical analysis are introduced and illustrated with common examples from chemical engineering. Even simple computations, such as log–mean temperature difference, can be grossly in error if the numerical limitations of computers are ignored. Reliable, easily solved models should be near-linear and explicit, and steps to achieve such models are included. The treatment is designed to be adequate for engineers writing small programs, or small parts of larger programs. References are introduced to enable professional engineering programmers to pursue the topics in greater depth.

End-users of chemical engineering software have responsibility for the decisions taken based on computed results. They must ensure that the software is adequate for its purpose, that all data is properly validated, and that the computed results are properly interpreted. They are also responsible for scoping the uncertainties in the computation and assessing their impact on the decisions taken. This chapter describes the steps that should be taken to ensure that computer aids are properly used and decisions are properly reached. It gives further reading for engineers likely to manage projects in which extensive use is made of computer tools.

A brief introduction is given to some of the rapidly advancing areas of computer-aided chemical engineering.