The aim of this final thesis is the application and comparison of several thermodynamic analysis methods for three different design variables in multi component distillation. The simulations of the distillation columns were mainly done with a program in C based on the method of t
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The aim of this final thesis is the application and comparison of several thermodynamic analysis methods for three different design variables in multi component distillation. The simulations of the distillation columns were mainly done with a program in C based on the method of tray-to-tray calculation. The equilibria on the trays were calculated with a new and fast concept that consisted of the combination of a data grid and an interpolation technique. The results of the program were accurate but the number of components was limited to three due to memory limitations of the software. First, the optimal sequence of distillation columns is analysed. A new approach is used that is based on the sum of a performance determining variable of each sequence. The sequence which has the minimum value for this sum should be the most optimal one. It was already known that the vapour load was useful for this variable. But this analysis has proved that a simple equation based on exergy loss gives better results. The contribution of this analysis is that after a simple exergy calculation only two or three possible sequences are left for a more rigorous analysis and therefore much time is saved. / The second design variable is the location of the feed tray. Besides the reflux ratio, the feed tray determines the number of trays in a distillation column. It is assumed that if the effects of mixing on the feed tray are minimum, the feed tray location is optimal. It is observed that the entropy production rate due to mixing on the feed tray predicted the optimal feed tray location on the edge of acceptance, but better than exergy loss due to same mixing. This is surprising because the predictability should be approximately equal. This result is however very dependant on how the mixing and thermodynamic model are defined. The temperature difference between the two flows which are mixed did not succeed at all to predict the optimal feed tray location. Finally, the location of the interstage heat exchangers is analysed with exergy in combination with the principle of equipartition of forces. According to this principle minimum exergy loss is obtained when the forces are equipartitioned over the whole column. Interstage heat exchangers are a theoretically proved method for reducing the exergy loss and they also affect the course of the driving forces. So, interstage heat exchangers at the right location can make the forces more equipartitioned. Varying the position of the heat exchangers, it has been observed that the deviation of the key force from the equipartitioned course is proportional to the total exergy loss. So, this is a practical application of the principle and it is therefore-a-step in the development towards a real engineering tool. This analysis has also/affirmea the consideration of a distillation column as a dissipative structure. '------/ The main conclusion is that the aim is successfully pursued. It is still possible to improve a relative old process like distillation with modem thermodynamic analysis tools like exergy and the equipartition of forces. The main recommendation is to develop the principle of equipartition of forces further with other processes in the chemical industry. But this work can also be a start for investigation of the flexibility and maximum output of a distillation column.