Design and control of a comprehensive Ethylenediamine (EDA) process with external/internal heat integration

Abstract

Ethylenediamine (EDA), also known as Ethane-1,2-Diamine, is a valuable raw material, and the synthesis will produce several higher polyamines. This study proposes a systematic synthesis method for separating six products from the EDA plant as the fresh feed. For the separation of six components, there are forty-two possible sequences. There will be only seven promising sequences left with the constraint of azeotrope and heuristics in distillation. To minimize the total annual cost (TAC), the pressure-swing configuration and the purity of flow rate that how close to the azeotrope can be optimized. Furthermore, unlike ordinary optimization, this study provides a method that considers the heat-integrated pressure-swing distillation (PSD) system during the iterative procedure. It is proved that this method can indeed find the genuinely optimal sequence distinct from the traditional iterative result based on the objective function, the lowest TAC. Through the other energy-saving strategies, the optimal result will save TAC of 15.15% by the external and internal heat integration, known as dividing wall columns (DWC). Afterward, basic and improved control structures are explored based on the optimal results in steady-state design. With the proposed control strategies, the purities of all components can be kept within acceptable ranges when faced with the inevitable throughput and composition changes.