Control of polyolefin production plants: Practical examples from nonlinear model predictive control to monitoring instrumentation

Polyolefin revolutionised life and also saved numerous ones. RADAR would not have been, electric cables would still use paper and gutta-percha insulation and supermarkets with their pre packed see- through wrapping would not exists; had it not been for polyolefin. The main raw materials, ethylene and propylene are typically coming from ethane or naphtha crackers. In such crackers, advanced process control (APC) such as model predictive control (MPC) and also real-time optimization (RTO) have been in common use for a long time. The situation is different in the production plants for polyolefin, APC technology has not been in so wide use as in the olefin production plants. Various factors can be contributed; amongst these is the need for coping with the nonlinearities observed in producing polyolefin. Examples of applying APC for the polyolefin industry will be drawn from proprietary developed controllers. Amongst these are the world´s first nonlinear MPC based on physical models implemented in the industrial size polypropylene plant in Norway back in 1993 as well as a model based reactor controller also based on physical models for the high pressure polyethylene production operational from around 1990 also in Norway.