| Summary: | A library of process unit models has been developed for synthesis studies that may be comparable to those developed for computer flowsheeting. The library has been integrated into an implicit enumeration process synthesis package for the generation of promising processes at the early stages of process design studies. The package allows consideration of heat integration in the conceptual synthesis of complete processes. Models for a number of commonly occurring units have been developed and a number of published synthesis studies have been reproduced including processes with non-sharp separations and with recycles. Previously published implicit enumeration synthesis procedures have used only very simplified models. Developments are reported that enable flowsheets with more realistic units to be generated. The basis of the synthesis used in this study is a rapid, stream-based implicit enumeration algorithm which combines dynamic programming and branch and bound optimisation. The technique enables the inclusion of flowsheets with multicomponent recycles and with unpredefined separation units. The program synthesises process flowsheets to meet user specified performance requirements. Thus, given process feeds and desired products, the program will select the necessary processing units and determine the way in which they are connected together. Processes synthesised, include vapour streams and liquid streams and include energy integration, handled through the use of 'heat increments' (pseudo-components) which record the temperature dependent net energy surplus or deficit in any stream. Processes can be more closely optimised by using multiple heat increments for a finer discretisation of the heat fluxes. A method of costing pressure changes between units has been introduced to allow the effect of pressure matching to be more rigorously incorporated in synthesising process flowsheets. Reactor models incorporating full kinetic expressions for more rigorous costing purpose have also been developed. Complete plant process flowsheets of sufficient scale to be of industrial relevance are generated and a number of case studies published in the literature have been reproduced and, in a number of cases, superior designs developed. Results to date compare favourably to other methods (e.g. AI, MINLP) both in quality of process design achieved and in computational time required to synthesise these designs.
|
|---|
