Energy-saving Analysis Of Distillation Process Based On Self-heat Recuperation Theory

Distillation is the most commonly used and effective separation method in chemical process. But the heat exhausted in the condenser and required in the reboiler result in huge consumption and low efficiency of energy in the conventional process. Although some ways used to improve the current system such as multi-effect distillation, thermally coupled distillation and heat pump distillation,the drawbacks accordingly arise as increase of exergy and investment costs. Therefore a new process with high efficiency and low-consumption should be projected.In this paper, A novel distillation process of methanol-water was designed with “self-heat recuperation theory”.Then a model was built to determine the operational parameters while another was made to calculate the material and energy balance of main equipments.finally,the whole process was simulated in Aspen Plus.Next,the analysis model was built on account of the characteristics of energy utilization,which included the energy balance in each equipment,analysis on system based on “three-link theory”,efficient use of energy.Then The results show that the ratio of recycled energy to total energy is only 5.9% in the conventional process(the remaining 94.1% share in the total energy must be provided) which is 88.71% in the advance process(only the remaining 11.29% share in the total must be provided). Accordingly,the energy input of the latter is decreased 86.43% of the former,which means the advanced project is more efficient than the conventional one.Further, three calculation ways were proposed to analysis exergy which based on exergy definition,exergy loss in equipments, exergy evaluation methods.Then it’s concluded that the conversion efficiency and recycling ratio of exergy of the advanced one were 93.18% and 61.42% respectively much more than those of the conventional system(63.66% and 1.38%),which means the advanced one is more reasonable than the conventional one.Finally,the economic analysis conducted by synthesizing energy cost and fixed investment indicated that the cost and the standard coal consumption of the advanced process were respectively decreased 76% and 75.18% of the conventional process on given boiler efficiency(70%) and generating efficiency(30%). In addition,the optimal direction for the advanced system was indicated on the thermal economy analysis.