(112a) Synthesis of Efficient Retrofit Designs Using Procafd

The face of process industry is changing rapidly by the development of new technologies, green chemistry and designing chemical processes or products that are efficient and sustainable. Due to increased environmental awareness, competitiveness and strict implementation of government legislation's, many industries are now paying more attention to improving their process to maintain their profitability. According to Grossmann [1] and Gunderson [2], about 70% of the projects initiated in process industry are retrofit projects. Process retrofitting & revamping mainly aims to find ways to minimize the operational expenditure with minimum change in the existing process equipment/operation. As a result, retrofit problems are more complex than the new synthesis design problems which has more degrees of freedom in the preliminary phase. So systematic process retrofitting methods and corresponding tools have become major area of research in process systems engineering.

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.[3], 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 [4] and life cycle assessment factors [5].

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%.

References:

[1] Gundersen, T., 1990, Retrofit design research and applications of systematic methods, in Foundations of Computer-Aided Process Design, Siirola, J.J., Grossmann, I.E. and Stephanopolous, G. (eds) (CACHE, Elsevier, Amsterdam, The Netherlands), p 213.

[2] Grossmann, I.E., Westerberg, A.W. and Biegler, L.T., 1987, Retrofit design of processes, in Proceedings of 1st International Conference on Foundation of Computer Aided Procedures and Operations (FOCAPO), Park City, UT, July, p 403.

[3] Tula, A.K., Eden, M. R., & Gani, R. (2015). Process synthesis, design and analysis using a process-group contribution method. Computers and Chemical Engineering, 81, 245-259.

[4] Carvalho, A., Matos, H. M., Gani, R., SustainPro-A tool for systematic process analysis, generation and evaluation of sustainable design alternatives, Computers and Chemical Engineering, 2013, 50, 8.

[5] Kalakul, S., Malakul, P., Siemanond, K., Gani, R. (2014), Integration of Life Cycle Assessment Software with Tools for Economic and Sustainability Analyses and Process Simulation for Sustainable Process Design, Journal of Cleaner Production, 71, 98-109