Arrangement of Throughput Manipulator and Inventory Control in Plantwide Control

整廠控制之產能操作與液位控制間的研究

鄭育昌(Yu-Chang Cheng) ； 吳國亮(Kwo-Liang Wu) ； 余政靖(Cheng-Ching Yu)

《Journal of the Chinese Institute of Chemical Engineers》 33卷3期 (2002/05) Pp. 283-295

https://doi.org/10.6967/JCICE.200205.0283

摘要

在這篇論文中主要是要討論整廠控制中產能與液位控制間的排列問題。當產能改變時，對於系統中的流量與濃度間的動態相互作用的重要性也被指出。我們可以用相對干擾增益(relative disturbance gain)來評估質量平衡控制的適當性，更重要的是相對干擾增益可由簡單的系統設計參數來求得，例如：系統的濃度或程序迴流比等。但這簡單的分析工具可提供我們基本的產能調節變的選擇，最後我們得到的結論是使用外部流（例如：新鮮進料或產能排出股）是優於內部流為產能操作變數。另外當產能是由反應器液位來調節的例子中，動態的交互作用顯得更重要。這意味著儘管得到完美的穩態交互作用的量測，但是實際上此結構還是有個明確的流量與濃度動態間的交互作用存在。因此一般對於質量平衡控制的設計是希望將動態間的交互作用最小化，所以流量動態速度的調諧也變得更重要。在這類型的例子中使用外部流仍是產能調節的最佳選擇，且流量速度適當的調諧對於好的質量平衡控制結構是重要的，而非線性的模擬結果也證實此結果。

並列摘要

The arrangement of the throughput/inventory control in plantwide control is studied in this article. Based on the way the production rate change is handled, two basic product quality control principles are explored. For the case of the conventional control structure, i.e., constant reactor level and temperature, the importance of the interaction between the flow and composition dynamics is pointed out. A steady-state interaction measure, relative disturbance gain, is employed to evaluate the appropriateness of the material balance control. Moreover, the relative disturbance gain can be expressed in terms of the design parameters, e.g., composition and recycle ratio. This serves as a basis for the selection of the throughput manipulator. The results show that the external flow, i.e., feed or product flow, is preferred over the internal flows. For the cases of variable reactor holdup, the dynamic interaction becomes important. That means, despite having a perfect steady-state interaction measure, schemes with significant dynamic interaction lead to poor closed-loop flow dynamics. Thus, the material balance control should be designed such that the dynamic interaction is minimized. Therefore, the tuning of the flow dynamics becomes important. Results also show that we should use the external flow as the throughput manipulator and tune the inventory control loops such that the flow/composition interaction is minimized. Since flow/composition interaction is inherent in recycle processes, the results can be extended to more complex recycle processes, e.g., systems with more than one recycle streams, in a straightforward manner.

並列關鍵字

Plantwide control ； Material balance control ； Inventory control ； RDG