(112a) Synthesis of Efficient Retrofit Designs Using Procafd
This work focuses on the application of hybrid approach and corresponding tool (ProCAFD) for providing a fast and efficient approach for retrofit at the process level. The hybrid approach is based on synthesis method proposed by Tula et al., which applies principles of computer-aided molecular design to the synthesis and design of process flow-sheets. That is, use process-groups representing different unit operations (reactor, distillation, flash, crystallization, etc.), bonds representing streams and/or recycles, rules for chemical feasibility also representing process flow-sheet feasibility and sum of group contributions representing the performance of the flow-sheet that can later be used to quickly screen the alternatives. However application of this method for retrofit problems is achieved by generating the process alternatives around an existing backbone composed of known process-groups. Here the existing process-groups (backbone) are selected based on the analysis of the base case flow-sheet using a comprehensive indicator-based analysis incorporating process economics, sustainability measures  and life cycle assessment factors .
In this work, ProCAFD is applied to various industrial processes to find retrofit designs that can substantially reduce operational cost. The application of the method and the tool will be highlighted using case studies involving production of styrene monomer from ethyl benzene, separation of C6 isomers etc. In all the cases the tool was able to find better retrofit designs where the total utility savings of the entire process are in the tune of 15-20%.
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