Design and control of an energy-saving phosgenation reaction distillation for toluene diisocyanate

Abstract

In this paper, the conventional reactive distillation (CRD) of toluene diisocyanate (TDI) production process is designed and optimized by minimizing the total annual cost (TAC). In order to make the HCl content in the side stream of the reactive distillation correspond with the specifications of the CRD process, a lot of energy needs to be consumed. Therefore, a reactive distillation dividing-wall column (RD-DWC) is comparatively proposed. The results illustrate that compared with CRD process, the TAC and energy consumption of RD-DWC process decreases by 40.625% and 46.038%, respectively. Apart from that, the RD-DWC will also improve the safety of the TDI production process. During the design process, the control of CCA conversion rate of reactive column is a key factor for achieving this process efficient. Furthermore, a feasible control scheme is investigated. Specifically, the residence time is controlled by liquid level for the reactive distillation that could obviously reduce the generation of by-products. This control scheme can effectively control the process and achieve good dynamic performance when ±10% flow rate and feed composition disturbances are introduced. Research on control performance is significant to develop energy saving technology for RD-DWC process.