最佳化批次結晶程序之操作與限制分析

Optimization of batch crystallization with constraints

謝翔峰(Hsiang-Feng Hsieh)

指導教授 ： 吳哲夫

國立臺灣大學/工學院/化學工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601942

摘要

本篇研究專注在三個批次結晶程序之動力模型。最適化冷卻結晶以及蒸發結晶的結果皆顯示，後期成長策略能生成較少量的新成核晶體質量。然而，後期成長策略是藉由在批次操作時間末期時，短時間內快速下降溫度或快速蒸發溶劑後達到設定的最終狀態。而實際操作上，需要不少的熱交換面積或者是耗費極大的能源才能完成最適化。因此，許多工廠在操作變數的曲線中加入下降速率的限制。結晶物質的動力學有助於找到最佳化的操作曲線以及加入限制操作的時間點，但是找出動力學參數是非常耗時的。所以本研究希望藉由模擬三種已驗證過動力學的物質，在特定限制條件下，找出一條回歸式。在已知最初、最終操作變數以及總批次時間下，能使用回歸式找出在特定限制條件下的最佳操作曲線。回歸曲線與模擬在限制下的最佳操作策略結果比較，平均誤差約為5.03%。Mullin-Nyvlt, cubic和linear 為三種不需動力式即可預測操作曲線的控制策略。將限制條件加入這三種策略並與回歸曲線比較。Mullin-Nyvlt, cubic 和回歸曲線皆有適用的系統，Linear 則無適用的系統。

關鍵字

結晶動力學彙整 ； 後期成核策略 ； 限制下的最適化 ； 冷卻結晶 ； 蒸發結晶

並列摘要

Three published crystallization kinetics from batch crystallizer is compiled, and the simulation and optimization of crystallization process are also provided. The results suggest that a late growth policy would be appropriate to minimize the final nucleated crystal mass. However determining the optimal curve of temperature or solvent mass is difficult and requires a kinetic model. Adding constraints on operating curve is a common method in industries. The simulation results of optimal procedure with constraints illustrate a trade-off between mass of nucleated crystals and equipment costs. Another problem often encountered in practical operation is hard to collecting useful data to find crystal kinetics. When dimensionless temperature or solvent mass is plotted versus dimensionless time, the optimal trajectory for many systems is similar for a given constraint. Therefore, for each constraint the results of many systems are fitted to a single curve which can be applied without knowledge of the kinetic parameters. Knowing the total batch time, initial and final value of manipulated variable, we can find a nearly optimal operating curve in a specific constraint. The average deviation between each optimal trajectory and regressed curve is 5.03%. Mullin-nyvlt, cubic trajectory and regressed curve may applicable in different system. Linear trajectory is no applicable in any system.

並列關鍵字

crystallization kinetics compilation ； late growth ； optimization with constraints ； cooling crystallization ； evaporation crystallization

參考文獻

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