(375y) Property Based Methods for Flowsheet and Molecular Synthesis
Every chemical process involves separation processes. The design of such separation processes and their corresponding flowsheets can be achieved by utilizing process group contribution methods where a set of process groups representing different types of separation operations are used (d'Anterroches et al., 2004). This method is analogous to the group contribution methods available for molecular design . The required process groups for a given mixture can be predicted based on the relevant properties for each specific separation unit operation (Jacksland et al., 1994). In this work a systematic framework is developed to identify the process groups and their sequence. The optimal sequence of separation processes with respect to a given target is identified based on the contributions of each process group to the needed property. Separation operations involving a mass separating agent require the identification of a suitable MSA. When solving the reverse design problem formulated by the process groups, some traditional MSAs may not meet the property constraints. Novel MSAs are identified using a reverse product design problem. The result is an integrated framework that simultaneously solves the molecular design problem as well as identifies the optimal sequence of separation processes involved. The developed approach involves the solution of two reverse problems. The first reverse problem identifies the property targets corresponding to the desired process performance. The second reverse problem is the reverse of a property prediction problem, which identifies the molecular structures that match the targets identified in the first problem. Property operator techniques are used to track the properties in both the process and molecular design problems. In this contribution, an algebraic technique has been developed for solving process and molecular design problems simultaneously. The developed algorithm merges the source-sink process design problem and molecular design problem using higher order property operators to identify the molecules with desired properties. Group contribution methods are used to form the molecular property operators that will be used to track the properties. The set of inequality expressions for the process and product design problem are solved simultaneously. The whole process synthesis, design and product design problem can be presented on a same platform from a property perspective as all of them aim at desired performance from a property perspective. This contribution will use a case study to highlight the principles of the developed methodology.