| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 96 === Owing to the rising cost of energy and the fact that new energy resources are not yet available to all, how to utilize energy in an efficient way has become an important issue for industrial processes. In normal chemical works, the distillation process plays the most part in consuming energy and naturally turns into the major subject to be investigated by many savants. The main objective is to design an applicable mode for the manipulation of distillation columns which achieves the energy saving. Therefore, not only the operating cost can be reduced but the environmental impact will be also lowered. The concept of multi-effect distillation columns had been introduced in 1950 by Robinson and Gilliland: The temperature differences (for heat exchange) between distillation columns can be produced by increasing the pressure in some columns, and heat integration within the distillation system is then carried out for the purpose of energy recovery and energy saving.
Based on a superstructure which incorporates all possible schemes, this work aims to propose a general mixed-integer nonlinear programming (MINLP) formulation for modeling and optimizing the multi-effect distillation system, where design objectives include the minimization of energy consumption and the minimization of total annual cost (TAC). Accordingly, optimal operating conditions can be obtained with different design objectives. For one thing, results from the proposed mathematical formulation will be compared with the results from Underwood’s method to confirm its validness. For the next, the results of multi-effect distillation system are also compared with the results of conventional distillation system to illustrate that the multi-effect distillation columns are actually capable of reducing the energy consumption and the total annual cost. Furthermore, the correlation between feed condition and resultant framework of distillation can be generalized through discussions on a series of examples.
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