Simulation System Development And Energy Optimization Of Brine Treatment Process

Simulation System development and energy optimizing of the brine treatment process in producing isocyanate are crucial to exploiting large-scale manufacturing of isocyanate,which are also important for manufacturing enterprise to implement cleaner production,recycling economy,energy saving,consumption reduction,pollution abatement,efficiency enhancement and have a great significance for national polyurethane industry.In this paper,the brine treatment processs in isocyanate production process is studied by using chemical system engineering methods and tools.In this study,process data and plant parameter are collected and simulation of a whole brine treatment system is developed on Aspen Plus Platform.It is determined that a liquid activity coefficient model PHILMXA3 suits the brine system containing organic best among a large number of parameter model.The validity of this model is demonstrated by the fact that most of the predicted data agreed well with the experimental data.With the application of Aspen Plus,it is found that the molar reflux ratio of the brine treatment system methanol distillation column is much higher than that of general distillation column,which results in product quality excess and unreasonable use of energy.Reflux ratio should be greater than 11 to meet the product requirements by the sensitivity analysis on Aspen Plus Platform.We research in the manufacturing process ofisocyanate and found an alternative heat source of methanol distillation column bottom stream,and we apply Aspen Plus to this new process.The former gas feed is replaced by condensate liquid feed in the new process, which decrease the molar reflux ratio from 56 to 22,significantly reduce the diameter of methanol distillation column,and save equipment investment.The heat generated from the condensation of gas feed becomes the heat source of the 6℃cold water in the isocyanate production,hence increasing the overall energy utilization.The optimum process and operating condition of the brine treatment process is obtained in this study,which have laid the foundation for the large-scale manufacturing technology of isocyanate and provide a reliable model for manufacturing enterprise to do some further researches.Energy optimization produces huge benefits.It can be saved more than three million each year because of the reducing consumption of the steam and recycled water.