Relay Feedback Tests for Highly Nonlinear Processes: Reactive Distillation

This paper is intended to demonstrate the effectiveness of the relay feedback test for the identification of highly nonlinear processes, namely, reactive distillation. Because of the multifunctional nature, reactive distillation exhibits strong nonlinearity and possible "sign reversal" in the steady-state gain of product composition and tray temperatures. A methyl acetate reactive distillation is used to illustrate performance of two different identification approaches: step test and relay feedback test. For the composition control, step tests reveal sign changes in steady-state gain as the step size varies from -10% to +10%. Moreover, step test is also sensitive to the direction of the step. On the other hand, consistent ultimate gain and the ultimate period can be identified for different relay heights with different initial step directions. The error in the high-frequency information is <5% for the reactive distillation column that has been studied. Good control performance can be obtained using simple PI controllers tuned with the ultimate gain and ultimate period. Comparison is also made for temperature control and, again, the results indicate that consistent high-frequency information can be obtained with the relay feedback test. Finally, relay feedback is applied to multivariable control of reactive distillation. The resultant PI controllers, designed based on the ultimate information, also gives satisfactory performance for set-point and load changes.

[1]  Kok Kiong Tan,et al.  Finite Spectrum Assignment Control of Unstable Time Delay Processes with Relay Tuning , 1998 .

[2]  Cheng-Ching Yu,et al.  Control of different reactive distillation configurations , 2006 .

[3]  Shih‐Haur Shen,et al.  Use of relay‐feedback test for automatic tuning of multivariable systems , 1994 .

[4]  Derek P. Atherton,et al.  Parameter estimation from relay autotuning with asymmetric limit cycle data , 2001 .

[5]  Achim Kienle,et al.  Nonlinear control of a reactive distillation column , 2003 .

[6]  Qing-Guo Wang,et al.  Low-Order Modeling from Relay Feedback , 1997 .

[7]  Cheng-Ching Yu.  Autotuning of PID Controllers , 1999 .

[8]  G. Marchetti,et al.  Identification and control of open-loop unstable processes by relay methods , 2001, Autom..

[9]  Cheng-Ching Yu,et al.  Derivation of transfer function from relay feedback systems , 1992 .

[10]  Cheng-Ching Yu,et al.  Autotune identification for systems with right-half-plane poles and zeros , 1999 .

[11]  Santosh Devasia,et al.  Output tracking between operating points for nonlinear processes: Van de Vusse example , 2002, IEEE Trans. Control. Syst. Technol..

[12]  Moses O. Tadé,et al.  Two-point control of a reactive distillation column for composition and conversion , 1999 .

[13]  William L. Luyben.  Getting more information from relay-feedback tests , 2001 .

[14]  Michael F. Malone,et al.  Conceptual design of distillation systems , 2001 .

[15]  Cheng-Ching Yu,et al.  Use of biased-relay feedback for system identification , 1996 .

[16]  B. R. Young,et al.  Modeling and Model Predictive Control of Composition and Conversion in an ETBE Reactive Distillation Column , 2005 .

[17]  William L. Luyben,et al.  Derivation of transfer functions for highly nonlinear distillation columns , 1987 .

[18]  Alberto Leva,et al.  Model-based proportional-integral-derivative autotuning improved with relay feedback identification , 2005 .

[19]  Muhammad A. Al-Arfaj,et al.  Comparison of Alternative Control Structures for an Ideal Two-Product Reactive Distillation Column , 2000 .

[20]  Moses O. Tadé,et al.  Pattern-based predictive control for ETBE reactive distillation , 2003 .

[21]  In-Beum Lee,et al.  An improved algorithm for automatic tuning of PID controllers , 2000 .

[22]  Sebastian Engell,et al.  Control of a reactive separation process , 2003 .

[23]  B. Bequette,et al.  Model predictive control of processes with input multiplicities , 1995 .

[24]  Devrim B. Kaymak,et al.  Comparison of two types of two-temperature control structures for reactive distillation columns , 2005 .

[25]  Muhammad A. Al-Arfaj,et al.  Comparative control study of ideal and methyl acetate reactive distillation , 2002 .

[26]  David Bogle,et al.  Study on nonminimum phase behaviour and optimal operation , 1997 .

[27]  K. Sundmacher,et al.  Reactive distillation : status and future directions , 2003 .

[28]  Moshood J. Olanrewaju,et al.  Performance Assessment of Different Control Structures for Generic Reactive Distillation Using Linear and Nonlinear Process Models , 2005 .

[29]  Cheng-Ching Yu,et al.  Temperature Control of Heterogeneous Reactive Distillation , 2004 .

[30]  Cheng-Ching Yu,et al.  Design alternatives for the amyl acetate process: Coupled reactor/column and reactive distillation , 2002 .