(44a) Steam Turbine Extraction APC Application

Significant challenges exist when trying to operate the steam system of a major chemical complex in the most efficient manner. One challenge is the constantly changing steam demand from different operating units. Each unit has its own level of operational autonomy which varies the steam demand. Another challenge is the distribution of responsibility for the operation of major steam-intensive equipment across multiple board technicians. For example, the boilers may be the responsibility of Board-A, while the two largest steam turbines are separately operated by Board-B and Board-C. It is difficult for technicians spread across multiple boards to manually control a complicated steam system in the most efficient manner. More than likely, the board technicians find an operating region within their comfort zone, which is a measurable distance from maximum efficiency. It is increasingly important to implement automated control strategies to overcome these challenges as utility costs continually increase. Equistar's Chocolate Bayou Chemical Complex has developed an Advanced Process Control (APC) application to operate the complex's steam system more efficiently by maximizing the extraction steam flows from the two largest turbines while monitoring key constraints in the turbines and steam letdown stations. Ultimately, the application reduces the cost of steam for all units inside the complex.