(666f) Generation of Sustainable Hybrid Process Flowsheets Using Procafd

Authors: 
Kumar Tula, A., Auburn University
Eden, M. R., Auburn University
Gani, R., Technical University of Denmark
The chemical industry is always looking for innovative process designs, which are both efficient and sustainable. To generate an optimal flowsheet, what is needed is a systematic way to identify the types of tasks-operations that need to be performed, the corresponding design of the operation-equipment, their configuration, mass-energy flows etc. Due to the fact that process synthesis problems are by nature combinatorial and open ended, a number of different solution approaches have been proposed. However, the solution for any synthesis-design problem is dependent on the search space of alternatives and the process performance criteria which in most cases are influenced by economic factors. This work focuses on the development of a computer aided tool (ProCAFD), capable of enumerating the entire feasible search space, analyze and determine the most sustainable process. ProCAFD is based on decomposition based method developed by Tula et al. (2015). On a higher level the workflow of ProCAFD can be divided into three stages: 1) Synthesis stage – Here a hybrid approach based on group contribution is used to generate and rank the alternatives. In this stage, chemical process flowsheets are synthesized in the same way as atoms or groups of atoms are synthesized to form molecules in computer aided molecular design (CAMD) techniques. The building blocks in flowsheet synthesis are called process-groups, which represent a single or set of unit operations that are selected by employing a thermodynamic insights based method. These building blocks are then combined using connectivity rules to generate all the feasible flowsheet alternatives. The main advantage of representing the flowsheet with process-groups is that, the performance of the entire process can be evaluated from the contributions of the individual process-groups towards the selected flowsheet property (for example, energy consumed). Available flowsheet property models include energy consumption, carbon footprint, product recovery, product purity etc. In this way, the entire list of feasible chemical process flowsheets is quickly generated, screened and selected. 2) Analysis stage – In this stage, comprehensive investigation consisting of sustainability, life cycle and economic analysis is performed to identify areas of improvement for the generated process alternative. The identified areas or process hotspots are translated into design targets that, if satisfied will guarantee process improvement. 3) Innovation stage – In this stage different innovative design strategies are used to match the set design targets. Different design strategies include simultaneous process optimization and heat integration where determination of optimal operating conditions and design parameters is solved together with heat integration involving minimizing utility consumption. One other strategy ProCAFD uses is a generalized method based on Tula et al. (2016) to replace distillation columns in the selected design with a hybrid distillation-membrane system to reduce the operational cost substantially. Other strategies include process intensification, where the phenomena based intensification method developed by Babi et al. (2015) is employed to generate intensified processes.

In this work, the software implementation of the developed methodology will be highlighted through several examples involving chemical and biochemical processes. In all the cases studied, the developed software could generate innovative and more sustainable solutions very quickly.

References:

A. K. Tula, B. Befort, N. Garg, K. V. Camarda, R. Gani, Sustainable Process Design & Analysis of Hybrid Separations, Computers & Chemical Engineering (2016). http://dx.doi.org/10.1016/j.compchemeng.2016.11.031.

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

D. K. Babi, J. Holtbruegge, P. Lutze, A. Gorak, J.M. Woodley, R. Gani, 2015, Sustainable Process Synthesis-Intensification, Computers & Chemical Engineering, 81, 218-44.