Process enhancement through waste minimization and multiobjective optimization

A simultaneous approach to maximize profit, while minimizing waste through source reduction with the implementation of multiobjective optimization with process simulation is presented in this paper. To demonstrate this methodology, the acrylonitrile process case study was selected. The approach involved four steps: process modeling and analysis, identification of process alternatives, selection of process alternatives and incorporation of multiobjective optimization. The simulator ASPEN PLUS™ 12.1 was used to model and evaluate the process. Process alternatives were identified from both literature and sensitivity analysis procedures. Sensitivity analysis helps initially in quickly eliminating inferior alternatives and then in enhancing the superior alternative to develop an efficient optimization procedure. Through this work, a general methodology was developed for the application of process optimization to process design. A sensitivity curve that shows the effect of waste treatment on the profit for the process was developed. Based on the sensitivity analysis results, the Plug Flow reactor scheme was the better alternative as compared to the base case, CSTR reactor scheme. After process modification and optimization, the process can earn a maximum net savings of $ 3.59 × 108 in seven years, an increase of 69% over the base case. At the other end of the spectrum, the modified process could generate waste of 1884 kg h−1, a 38% reduction compared to the base case. The modified optimized process is observed to show significant improvements in environmental impacts as analyzed by the Waste Reduction Algorithm.