(427g) Industrial Fluidized Bed Polyethylene Reactor Temperature Modeling in Condensed Mode Operation

As one of the most essential parts in the gas-phase polymerization of ethylene, the condensed mode operation plays a critical role in the yield of polymer product. This study is based on the classical emulsion-bubble two phases model with the liquid and its evaporation module also being taken into consideration. The modified model introduces a concept of “coexistence of the gas-liquid-solid (G-L-S) zone and the gas-solid (G-S) zone within the same fluidized bed reactor”.  In this model, the emulsion phase is regarded as a plug flow regime in the G-L-S zone and a well-mixed regime in the G-S zone. However, the bubble phase is assumed to be a plug flow regime along the whole fluidized bed. According to the heat balance equation, the temperature along the reactor bed height is obtained by use of the industrial operating data. The model results demonstrate that, as the liquid content increases, the height of G-L-S zone expands and the temperature profile witnesses a corresponding change. This study investigates the effect of important parameters, such as bubble size, on the heat transfer and temperature distribution along the bed height. To be specific, large-sized bubbles lead to low-value heat transfer coefficients between the bubble and emulsion phase, and thus causes the ultimate temperature difference between bubble and emulsion phase, which obviously affects the bed temperature distribution significantly. The results from our model fit satisfactory with the industrial temperature data.