Enhancing incremental deep learning for FCCU end-point quality prediction

Abstract

In the refining process, Fluid Catalytic Cracking Unit (FCCU) end-point quality prediction plays an important role in real-time quality monitoring, optimization and control. Due to the process uncertainties (such as changes of raw materials, abrasion of mechanic components, catalyst deactivation, changes in the external environment, etc), data distribution of process data in FCCU is time-varying, which leads to accuracy degradation of the quality prediction model. Therefore, to deal with the time varying characteristic of process data and avoid accuracy degradation of the quality prediction model, real-time processing should be considered. In this paper, an enhancing incremental deep learning approach is proposed for the online quality prediction of the absorption-stabilization system in FCCU. First, the offline model is built by Stacked Auto Encoder-Deep Neural Network (SAE-DNN). To determine whether the data distribution has changed and model modification is needed, a concept drift detector is proposed for the regression problem by defining an error bound in the Statistical Test of Equal Proportions (STEPD). If the model modification is needed, then the top layer of the offline SAE-DNN model is expanded by Random Vector Functional Link (RVFL) structure, and the parameters in the expansion layer is dynamically assigned by the new coming data with the group lasso regularization and the L2 regularization. The proposed approach is validated by predicting the Saturated Vapor Pressure (SVP) of stabilized gasoline in the FCCU. The experimental results show that the proposed approach can deal with the time-varying characteristic of process data and avoid accuracy degradation under process uncertainties.