Estimator design with PLS model for consistent control of refinery main fractionators

In this paper the problem of designing product quality inferentials for refinery main fractionations is addressed by using the PLS regression. A simulated crude distillation unit is chosen as case study, and several linear steady-state estimators are designed and compared in terms of accuracy and consistency, i.e. the estimator ability of guaranteeing low closed-loop offset. The paper shows the importance of the auxiliary measurement choice in order to build an effective inferential control scheme. Moreover, it shows that the use of only temperature measurements is not sufficient to guarantee an acceptable estimator performance. Additional measurements as the operating pressure and internal flows have been used to improve the estimator accuracy and consistency.