(57a) Keeping Advanced Process Control (APC) Performance and Maintenance and Improvement of APC System

This paper explains the history of advanced control projects in Mitsubishi Chemical Corporation (MCC) and the current problems of them. Our company started using advanced control systems in the 1980's which were made by MCC. Afterwards, we changed them gradually into commercially packaged software (mainly multivariate model prediction controllers), like DMC plus for large-scale plants. Using the commercial packages helped us to obtain greater profits much faster than before. Most large-scale petrochemical plants already have been equipped with the advanced control systems, and we have now shifted the stage of the projects to development of systems for small and medium-sized scale plants. Also we recognized the importance of system maintenance to keep the advanced process control (APC) performance high, and daily maintenance and improvement of control performances have been done. Simultaneously, we have been trying to use a couple of new technologies like soft sensors to improve control performance. We have also been investigating methods of quantitative assessments of control performance to detect deterioration much faster and the method of efficient model construction to reduce costs and time to apply them to the new plants.