Study On The Application Of Dividing Wall Column To The Reactive Distillation And Air Separation

Distillation is the primary separation process used in the chemical processing. While this unit operation has many advantages, one drawback is its significant energy requirement. The dividing-wall distillation column (DWC) offers an alternative to conventional towers, with the possibility of savings in both energy and capital costs. The separation of a three-component mixture into its pure fractions in conventional systems requires a sequential system with at least two columns or main columns with side columns. With a dividing wall column this task can be solved in only one apparatus. Compared with conventional distillation sequence, the technology has a higher thermodynamic efficiency, lower energy consumption, and because a high degree of integration, the process can reduce the number of heat transfer equipment, cut down the equipment investment, and finally bring higher economic benefits. The technology is rapid developing abroad right now. There are now more than 100 columns installed worldwide, it become one of the most focus research field of process integration.In this thesis, the path from conventional distillation sequence (CDS) to DWC is introduced and the reason why this technology can save energy is analysised at the base of DWC structure and principle. And the shortcut method is presented in designing dividing wall column. According to the separation characteristics of DWC, the application ranges are given. And the way how to use Aspen Plus in design and optimization of DWC is elaborated. Methyl acetate reactive distillation system and the cryogenic air separation are taking as two examples in this work. The reaction kinetics and thermodynamic model of the two systems are studied; the corresponding DWC models are established. All of these degrees of freedom have been initialized before rigorous simulation, and then the primitive optimized value of every parameter has been determined, which provides the initial values for the further optimization of DWC.Taking the foundation of preliminary optimization results, the optimal design procedure of the two DWC are proposed considering the effects of operation and equipment parameters on the total annual cost (TAC), and then, the economic optimized operation and equipment parameters are obtained, minimizing the TAC according to certain optimization steps, maintaining the products purity requirement. At last, the two systems are analysised and completed based on the optimization results of both CDS and DWC. The results show that not only reductions in energy consumption and CO2 emissions but also higher thermodynamic efficiency can be obtained for the DWC.