醋酸去水製程中進料雜質對非均相共沸蒸餾塔的設計與控制之影響(II)

Effect of Feed Impurity on the Design of and Control of Heterogeneous Azeotropic Distillation for Acetic Acid Dehydration(II)

高堂凱(Tang-Kai Gau)

指導教授 ： 黃孝平

國立臺灣大學/工學院/化學工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.02249

摘要

王俊惠(2004)利用實際的工廠數據，對含有間位二甲苯和乙酸甲酯之進料不純物，探討其在酸酸去水製程對非均相共沸蒸餾程序造成的影響。本研究是探討在醋酸去水製程中，進料中含有對位二甲苯之不純物對非均相共沸蒸餾塔的穩態設計與動態模擬測試之影響。醋酸與水並沒有共沸點，但是如果用簡單蒸餾的方法來分離醋酸和水是非常不實際的，因為在汽液平衡區線上接近純水的區域會有切線狹點(tangent point)的現象存在，因此一般是用非均相共沸蒸餾塔來分離醋酸與水，本論文使用的共沸劑是乙酸異丁酯。當系統有對位二甲苯這個不純物存在時，在設計時必須要加上一條側分流，否則對位二甲苯會累積在塔內。經由年總成本(TAC)的計算，找出系統的最適設計，不過最適設計的控制效果不佳，因此加大共沸劑的流量，使塔底出料的共沸劑組成增大，這時的控制效果就相當的好。因為側分流的流量太小不易控制，所以提出了自動清除策略(Automatic Purging Strategy)來解決這個問題，它不需要即時的量測出料的濃度，只需量測塔內某一板的溫度就可以使用，而且塔頂和塔底醋酸的濃度也會維持在規格附近。

關鍵字

共沸蒸餾 ； 醋酸去水 ； 進料雜質

並列摘要

In this study, effect of feed impurity on the design and control of heterogeneous azeotropic distillation for acetic acid dehydration is investigated. Although acetic acid and water do not form azeotrope, using simple distillation to separate these two components is not practical. The reason is because the system has tangent pinch on the pure water end, thus it is more customary in industry to use an entrainer via a heterogeneous azeotropic distillation column system for the separation. The entrainer used for this system to enhance the acetic acid and water separation is isobutyl acetate. The impurity, p-Xylene, during normal operation will not leave the column system through outlet stream from either aqueous phase of top decanter or column bottom . A side stream purge is proposed to solve the problem of p-Xylene accumulation. Optimum design of acetic acid dehydration system is determined by total annual cost (TAC). But the controlability of the optimal design system is not good. Increasing entrainer flow rate is proposed to improve the controlability. Since the optimal flow rate of the side stream is quite small, it is not easy to control the flow rate. A practical automatic purging strategy is proposed instead. This automatic purging strategy does not rely on any on-line composition measurement but just on some tray temperature measurements. Closed-loop dynamic simulation demonstrates that the proposed purging strategy can successfully keep both top and bottom product purities at their specifications.

並列關鍵字

Heterogeneous Azeotropic Distillation ； Acetic Acid Dehydration ； Feed Impurity

參考文獻

[1] 錢義隆，”共沸蒸餾系統之設計與控制”，化工月刊，第49卷第4期程序系統工程專刊(2002)

[2] 王俊惠，”進料雜質對非均相共沸蒸餾之影響”，國立臺灣大學化學工程研究所碩士論文(2004)

[7] Chien, I. L.; Fruehauf P. S., “Consider IMC Tuning to Improve Controller Performance,” Chemical Engineering Progress, 86(10), 33-41(1990)

[8] Chien, I. L.; Wang, C. J.; D. S. H. Wong, “Dynamics and Control of a Heterogeneous Azeotropic Distillation Column: Conventional Control Approach,” Ind. Eng. Chem. Res., 38, 468-478(1999)

[9] Chien, I. L.; Wang, C. J.; D. S. H. Wong; Lee, C. H.; Cheng, S. H.; Shin, R. F.; Liu, W. T.; Tsai, C. S., “Experimental Investigation of Conventional Control Strategies for a Heterogeneous Azeotropic Distillation Column,” Journal of Process Control, 10, 333(2000a)