Estimating Product Composition Profiles in Batch Distillation Via
ARTICLE IN PRESS Control Engineering Practice 12 (2004) 917–929 Estimating product composition profiles in batch distillation via partial least squares regression Eliana Zamprognaa, Massimiliano Baroloa,*, Dale E. Seborgb a Dipartimento di Principi e Impianti di Ingegneria Chimica (DIPIC), Universita" di Padova, Via Marzolo, 9, 35131 Padova PD, Italy b Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA Received 15 February 2003; accepted 24 November 2003 Abstract The properties of two multivariate regression techniques, principal component analysis and partial least squares (PLS) regression, are exploited to develop soft sensors able to estimate the product composition profiles in a simulated batch distillation process using available temperature measurements. The estimators’ performance is evaluated with respect to several issues, such as pre-processing of the calibration and validation data sets, number of measurements used as sensor inputs, presence of noise in the input measurements, and use of lagged measurements. A simple augmentation of the conventional PLS regression approach is also proposed, which is based on the development and sequential use of multiple regression models. The results prove that the PLS estimators can provide accurate composition estimations for a batch distillation process. The computational requirements are very low, which makes the estimators attractive for on-line use. r 2004 Elsevier Ltd. All rights reserved. Keywords: Batch distillation; Composition estimators; Soft sensors; Partial least squares regression; Principal component analysis 1. Introduction composition), at constant distillate composition (with variable reflux ratio), and at total reflux. A combination Batch distillation is a well-known unit operation that of these three basic modes can be used to optimize the is widely used in the fine chemistry, pharmaceutical, performance of the separation.
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