Energy saving design and control of side-streams reactive distillation configuration for diphenyl carbonate production process

Abstract

Diphenyl carbonate (DPC), a phosgene-free precursor for polycarbonate production, has traditionally undergone industrial production through a well-established two-step transesterification process by a reactive distillation (RD) and a distillation column. Thermal enhancement techniques in RD, such as thermally coupled (TCRD) and hybrid heat-integrated (HIRD) methods, have consistently demonstrated significant improvements in energy efficiency, eliminating remixing effect and reducing total annual cost (TAC) during DPC synthesis. However, the combination of TCRD or HIRD with a side-stream configuration (SS) remains relatively underexplored, particularly in the context of DPC production. This study aims to address this gap by proposing a novel combination of TCRD/HIRD, incorporating both a one side-stream (SS1-TCRD and SS1-HIRD) and a two side-streams configuration (SS2-TCRD and SS2-HIRD). Employing a sequential iterative procedure for optimization, the study sought to minimize TAC. Results unveiled SS2-HIRD as the optimal configuration, showcasing a remarkable 47.27% reduction in energy consumption and a 31.46% decrease in TAC. Moreover, four proposed control structures (CS1∼CS4) were implemented for SS2-HIRD to ensure both product quality and process safety. Among all structures, CS4 exhibited remarkable efficacy in managing disturbances in feed and composition throughput, demonstrating the smallest integral of the absolute error (IAE) value.