Product quality estimation and operating condition monitoring for industrial ethylene fractionator

In this industry-university collaboration, a soft sensor for measuring a key product quality and an on-line monitoring system for testing the validity of the soft sensor were developed to realize highly efficient operation of the ethylene production plant. To estimate impurity concentration in the ethylene product from on-line measured process variables, a dynamic partial least squares (PLS) model was developed. The developed soft sensor can estimate the product quality very well, but it does not function well when the process is operated under conditions that have never been observed before. Therefore, an on-line monitoring system was developed to judge whether the soft sensor is reliable or not. The monitoring system is based on the dynamic PLS model designed for estimating the product quality. The present research provides a PLS-based framework for developing a soft sensor and monitoring its validity on-line. In addition, simple rules were established for checking the performance of a process gas chromatograph by combining the soft sensor and the monitoring system. The soft sensor and the monitoring system have functioned successfully in the industrial ethylene plant.