Multi-level modelling of the hydrodynamics in gas phase polymerisation reactors

The gas-solid fluidised bed process is the most versatile process for the production of polyolefins, because it allows the production of polyolefins with a broad distribution of both the product density and molecular weight. In spite of the excellent heat transfer characteristics of a fluidised bed, the production capacity is still limited by the rate of heat removal and temperature control in the polyolefin production process is a major point of attention. The rate of heat removal is largely determined by the large scale convection patterns prevailing in the gas phase olefin polymerisation reactor, induced by the in situ formed and growing gas bubbles. Moreover, the bubbles play an intricate role in the particle mixing and segregation behaviour of the fluidised bed. To improve the design, operation and scale-up of these gas-fluidised bed processes, a better understanding and a quantitative description of these phenomena is required. Therefore, the main objective of this project was the development of fundamental hydrodynamic models to describe and study the hydrodynamic behaviour of the gas-solid fluidised bed reactor.