Abstract
Dimethyl carbonate (DMC), an important environmentally benign chemical because of its biodegradability and less toxicity, is widely used in process industry. A reactive-distillation-based process was recently developed by Liaoning Oxiranchem Group to produce DMC via transesterification of methanol (MeOH) and ethylene carbonate (EC), coproducing ethylene glycol (EG). To synthesize the heat exchanger network (HEN) of the preliminary process design, it was noticed that the variation of operating conditions of the high pressure column in the pressure swing distillation scheme had strong impacts on the temperature and composition of the overhead stream, and thus affected the HEN design. Taking into consideration the strong interaction between the process units and HEN, the process operating conditions were optimized simultaneously with the synthesis of HEN, instead of using the traditionally sequential optimization scheme. Based on Pinch technology, the Composite Curves and Grand Composite Curves were used to dig out the potential for the reduction of energy consumption. Sensitivity analysis was carried out to investigate how the operating variables affect the energy targets of the HEN. By assessing and comparing the energy target in each case, the optimal operating condition was obtained, under which the heat duties of hot utility and cold utility were 3.84 MW and 3.45 MW respectively. The comparison between the proposed HEN design and the one acquired using the sequential optimization approach showed a considerable reduction of 20.8 % in the hot utility consumption, indicating that through simultaneous optimization of process operating conditions and HEN synthesis, more energy savings could be expected.
