多效蒸餾塔系統之分析與最適化設計

Abstract

近年來能源短缺問題日益嚴重，如何能有效率的提升工業製程之能源使用效率，已是相當重要的課題。在傳統化學工業中，蒸餾塔是相當耗能的單元，如何設計出適當的蒸餾塔結構，有效率地使用能源減低操作成本與減少對環境的污染，已成為大家研究的方向。早在1950多效蒸餾塔(Multi-effect Distillation Columns)的概念已被Robinson與Gilliland提出，藉由調整兩根塔的壓力，造成溫度差以進行熱整合，進而達到節省能量消耗與能量再利用的目的。 本論文以Underwood's equation與kings formula計算出的理論最小蒸氣量並繪製蒸氣量圖為基礎，討論三成分系統多效蒸餾塔進料與蒸餾塔蒸氣量的關係，進而提出四成分多效蒸餾塔結構與推導各結構所需最小蒸氣量，計算出各結構節省的能量百分比，歸納在各種不同進料狀況下，所適合的蒸餾塔結構。將理論推導的結果與知名商業軟體 Aspen Plus 模擬出的最小蒸氣量做比擬，驗證本研究之準確性以及偏差的原因，並依照實際狀況提出更加省能的方法。

The problem of energy shortage has become serious. it is important to study useful methods for increasing the energy efficiency in process industries. Distillation process is a typical unit that uses a lot of energy in chemical plants.The topics of designing proper distillation column arrangements to utilize energy efficiently and lowering operating cost while attaining the goal of protecting environment have become important research directions. The concept of multi-effect distillation columns has already mentioned by Robinsson and Gilliand in 1950. They proposed that by adjusting the pressure of two columns, the temperature difference of them would be large enough to enable heat integration. And it can achieve the purpose of energy conservation and recovery. Based on the Underwood's equation and kings formula to calculate the theoretical minimum vapor flow rate in a distillation column, the study attempts to discuss the relationship between the feed conditions and the minimum vapor flow rate in three components multi-effect distillation system. The results from three component separation problems are extended to multi-effects distillation columns for separating four components. The potential energy savings when compared with the conventional arrangement are investigated. The theoretical results are also confirmed by comparing its results with those from Aspen Plus simulation.