Machine Learning-Based Soft Sensors for Vacuum Distillation Unit

Introduction Product quality assessment in the petroleum processing industry, such as crude distillation, can be difficult and time-consuming, e.g. due to a manual collection of liquid samples from the plant and the subsequent chemical laboratory analysis of the samples. The product quality is an important property that informs whether the products of the process are within the regulated specifications, such as ASTM Petroleum Standards. In particular, the delays caused by sample processing (collection, laboratory measurements, results analysis, reporting, etc.) can lead to detrimental economic effects. One of the strategies to deal with this problem is so-called soft sensors. Soft sensors are a collection of models that can be used to predict and forecast some infrequently measured properties (such as laboratory measurements of petroleum products) based on more frequent measurements of quantities like temperature, pressure and flow rate provided by physical sensors [1]. Soft sensors short-cut the pathway to obtain relevant information about the product quality, often providing relevant measurements as frequently as every minute. One of the applications of soft sensors is for the real-time optimization of a chemical process by a targeted adaptation of operating parameters. Models used for soft sensors can have various forms, however, among the most common are those based on artificial neural networks (ANNs) [2]. While soft sensors can deal with some of the issues in the refinery processes, their development and deployment can pose other challenges that are addressed in this paper. Firstly, it is important to enhance the quality of both sets of data (laboratory measurements and physical sensors) in a so-called data pre-processing stage (as described in Methodology section) [3]. Secondly, once the data sets are preprocessed, different models need to be tested against prediction error and the model’s interpretability. In this work, we present a framework for soft sensor development from raw data to ready-to-use models.