利用混合式薄膜蒸餾系統對共沸組成混合物分離之設計與控制

Abstract

本研究完成了混合式薄膜蒸餾系統之完整設計的最適化設計，並探討了利用內部式回收改良設計的可能性，而研究結果發現內部式回收應用在滲透蒸發單元只改善了部分的設計案例，所以我們利用經過無因次化的方程式來決定究竟回收是否有益。經推導完成的通用架構，進一步了解內部式回收的作用。在此以通用架構探討兩個真實系統：乙醇─水以及異丙醇─水的分離。不含內部式回收的最適化結果證明了不同的共沸組成造成不同的最適化程序組態。乙醇系統的最適化設計包含了單根蒸餾塔加上後接的薄膜單元串接。而異丙醇系統的組態則是需加上第二根蒸餾塔才是較經濟的設計。最後經由分析得知適當應用內部式回收可以進一步改良上述兩個製程。在系統動態方面，兩個製程的控制架構均已建立，並確定了兩個系統的可控制性。而系統動態模擬發現了包含內部式回收的系統動態響應比不含內部式回收的系統較慢。

The optimization of complete designs for hybrid membrane-distillation systems is done in this research. The possibility of design improvement by using internal recycle is investigated. Internal recycle in pervaporation only improves the design in some cases. These conditions where internal recycle is beneficial are determined by studying the generalized dimensionless equations. The result is a general framework for understanding internal recycle. Two real systems which are ethanol – water and isopropanol - water system are also investigated. Optimization results without the recycle show the difference in the azeotrope composition causes a difference in the optimum process configuration. The optimal design for ethanol system has a single distillation column followed by a membrane cascade. On other hand, for the isopropyl alcohol system a second distillation column in the configuration gives a better design. The appropriate application of internal recycle further improves the design in both cases. Control structures for these designs are developed to ensure the controllability of the process. The dynamic simulation of the system with internal recycle shows a slower response compared to those without internal recycle.