Design and control of reactive dividing-wall column for the synthesis of diethyl carbonate

- A reactive dividing-wall column is designed to synthesize diethyl carbonate by transesterification.
- Homogeneous catalyst sodium ethoxide is used in reactive distillation column to ensure sufficient activity.
- Due to the presence of azeotrope in the reaction system, feed location is discussed and an unusual feed location is used.
- An effective control structure for the reactive dividing-wall column is proposed to control the product composition.

In this study, dimethyl carbonate (DMC) and ethanol (EtOH) are used to synthesize diethyl carbonate (DEC) by transesterification. In order to have sufficient activity for application in reactive distillation (RD) column, homogeneous catalyst sodium ethoxide is used and can be recycled to reuse. Due to the presence of azeotrope in the reaction system, feed location is discussed and an unusual feed location is used: the heavier DMC feed should be located in the middle of the reaction section, while the lighter EtOH feed should be located at the top part of the reaction section. A conventional RD process is developed and optimized by minimizing the total annual cost (TAC). A reactive dividing-wall column (R-DWC) is also designed with the same number trays, feed conditions and product specifications. The results show that the R-DWC can save 18.7% of the energy consumption and 13.9% of the TAC compared with the conventional RD process. The control structure for the R-DWC is investigated to control the product composition. The proposed control structure can maintain the product purities close to the set point when disturbances in the feed flow rate and feed composition are introduced.

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