A Short-Cut Method for Optimal Selection of Controlled Variables

Mahajanam, Rama V.; Zheng, Alex

doi:10.1016/s1474-6670(17)38532-4

Cited by 1 publication

(2 citation statements)

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“…The controllability index is a function of process dynamics, process constraints, disturbance characteristics, product variability, and controller/control structures. Consider a simplified flowsheet of the butane alkylation process, a continuous process, discussed in detail in Mahajanam and Zheng 11 and depicted in Figure 1. The process objectives are to meet the desired production rate and maintain the product purity of i-octane within variability specifications.…”

Section: Controllability Index νmentioning

confidence: 99%

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Evaluation of Cost of Dynamic Controllability and Optimal Surge Capacity without Dynamic Models

Mahajanam

Zheng

2002

Ind. Eng. Chem. Res.

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It is well-known that the most economical design from a steady-state economics perspective does not necessarily need to be easily controllable and might, in some extreme cases, even be uncontrollable. It is important to evaluate and quantify the dynamic controllability of a process at the design stage. Mahajanam (Ind. Eng. Chem. Res. 1999, 38, 999-1006) introduced a simple controllability index (ν) to quantify dynamic controllability in terms of economics. The dynamic controllability index is defined as the smallest additional surge capacity required to meet all of the control objectives and constraints dynamically for all of the expected disturbances. The index depends quantitatively on the process design and the control system alternative for each design. It has been found useful to compare plantwide control alternatives quantitatively (AIChE J. 1999(AIChE J. , 45, 1255(AIChE J. -1265. The main difficulty in applying the above method at the design stage is the need for a rigorous dynamic model, which is rarely available at the conceptual design stage. To resolve this difficulty, we propose that the controllability index (ν) be estimated with a steady-state model of the process. The proposed approach is based on several simplifying assumptions and is illustrated with a simple reactor-separator-recycle system.

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Section: Controllability Index νmentioning

confidence: 99%

“…Consider a simplified flowsheet of the butane alkylation process, a continuous process, discussed in detail in Mahajanam and Zheng and depicted in Figure . The process objectives are to meet the desired production rate and maintain the product purity of i -octane within variability specifications.…”

Section: Controllability Index νmentioning

confidence: 99%