Application of close loop expert system for heating control of rolling mill furnaces in a steel plant

Abstract

One of the critical impediment faced in hierarchical control in an process industry is unavailability of exact mathematical co-relations, which can precisely define the process behavior. These are primarily due to variable, complex and un-measurable factors and noises influencing the process behavior. However, such cases are most appropriate application areas of Expert Systems. In process industry, Expert Systems are one of the successful application areas of Artificial Intelligence, where expertise and knowledge of a Process Expert or a group of Experts are embedded as computer inference software and database. In a real time situation, these systems can take intelligent decisions as would have been taken by process Expert on a similar situation. Determination of exact Set Process Temperatures or thermal regime on different parts of Rolling Mill Furnaces like Annealing Furnace in a Steel Industry is an intriguing problem. However, this decision is very crucial as final mechanical and metallurgical quality of steel stock significantly depends on fixing and accurate control of these temperatures. But as a irony, no well defined mathematical co-relations are available, which can predict exact thermal regime to be followed to achieve desired quality and properties of steel coils/sheets under heating inside such furnaces. The aforesaid intriguing issue has been successfully resolved by development and implementation of Expert System guided heating control system through prediction and control of optimum furnace temperatures inside Annealing Furnaces at Cold Rolling Mill of Bokaro Steel Plant and Decarburization-Annealing Furnace at Silicon Steel Mill of Rourkela Steel Plant. In both the cases, concepts of hierarchical automation has been used, wherein Expert System comprising Level-II tier of automation predicts most appropriate thermal regime to obtain desired product quality for a given set of steel sheet. A seamlessly dovetailed PLC constitutes Level-I automation layer. PLC monitors and controls the plant as per advice from Expert System. Both the systems have enhanced plants efficiency by improving production, quality and energy conservation.