Modeling Fouling Effects in LDPE Tubular Polymerization Reactors. 2. Heat Transfer, Computational Fluid Dynamics, and Phase Equilibria

Fouling in a low-density polyethylene (LDPE) tubular polymerization reactor is caused by the polyethylene/ethylene mixture forming two phases inside the reactor. Some of the polymer-rich phase is deposited on the reactorʹs inside wall, which considerably reduces heat-transfer rates. Phase equilibria calculations show a high degree of sensitivity of the singlephase/two-phase process fluid boundary to temperature. Almost all of the process stream is single phase and the fluid mixture is only two phase in the boundary layer close to the reactor wall where the temperature is low enough to cause phase separation. At a given reactor pressure, the reactor inside wall temperature is the critical parameter in determining when fouling occurs, and this is controlled by the coolant stream temperatures.