Advanced control strategies for polyolefin gas phase processes

Advanced control strategies have been implemented on various polyolefin gas phase processes including reactor temperature, gas compositions, polymer properties, production rate and bed weight/level controls. The strategies consist of nonlinear inferential estimators to provide estimates of disturbances and quality soft sensors (VOAs), nonlinear model predictive controllers (NMPC) to describe nonlinear process dynamic behavior, and MPC which is adopted in a hierarchical structure for staged implementation. Temperature and gas composition (GC) Process Perfecter®s are designed to stabilize the operation and handle highly interactive controlled variables. Quality (QC) Process Perfecter® is used to manipulate the concentration ratio setpoints of GC Process Perfecter®, control polymer quality properties, perform automatic grade transition, and maximize prime production. The implementation methodologies and controllers´ performance are presented to illustrate the usefulness of these advanced control strategies to industrial polymer manufacturing facilities.