Use of Process Simulation In Ethylene Plant APC and Dynamic Optimization

Showa Denko owns and operates a large Ethylene plant in Oita, Japan.  Depending on the economic environment, plant objective is a combination of Energy Efficiency and Production Capacity.  In order to achieve these objectives, Showa Denko had contracted Yamatake and Honeywell to design, configure and commission APC and Dynamic Optimization on the Ethylene Plant.  Such a project was completed in 2002 and the APC and Optimization applications have been continuously operational for the last decade.

The solution at Showa Denko utilized Multivariable Predictive Control applications that have linear models.  The Dynamic Optimization application inherited the APC models which maintained complete consistency between APC and Optimization.  This approach however required a strategy for handling non-linearities that are inherent in the operation of an Ethylene plant.   A gain updating strategy that utilized custom calculations of yield prediction and energy consumption were commissioned. 

Since the initial commissioning, Showa Denko has continued to enhance the applications.  Additional variables that accounted for all major energy usage and associated gain scheduling have been added.  The operator workflow has been made effective by a hierarchy of displays in Japanese, by a continuous display of active bottlenecks and by daily optimization reports.         

An upgrade completed in 2010 by Yamatake and Honeywell has converted the custom calculations for gain updating by standard software that uses a commercially available Process Simulator.  A benefit of this approach is that the applications can now be more easily maintained and enhanced by Showa Denko.  This paper summarizes the existing APC and Optimization solution and discusses the details of the gain updating strategy that was recently implemented.