Modelling of Condensed Mode Cooling during the Polymerization of Ethylene in Fluidized Bed Reactors

A compartmentalized reactor model has been developed to simulate the impact of running a fluidized bed reactor for the gas-phase production of ethylene in condensed mode operation, that is, in the presence of an induced condensing agent (ICA). The reactor model captures the impact of the liquefied feed on production rates and molecular weight distributions. Particular attention has been paid to including the co-solubility and co-diffusion effects of the ICA, which are often overlooked. A criterion for defining compartment height is also proposed, and the effects of number/height of compartments in the model predictions are studied. The model is validated with patent data and shows good agreement with two sets of data from different sources. The effects of two ICAs (n-pentane and n-hexane) are studied, and it is shown that an increased ICA liquid content leads to less steep temperature profiles and increased production rates. The effects of other operating conditions such as hydrogen content, operating temperature, liquid droplet size, polymer recovery height, and liquid injection height are studied. They all showed good agreement with the available experimental results found in the literature. A scale-down exercise was also carried out where industrial and pilot-scale reactors are compared.