AN IMPROVED MODEL FOR TEMPERATURE AND CONVERSION PROFILES IN TUBULAR HIGH PRESSURE POLYETHYLENE REACTORS

An earlier computer model for tubular high pressure polyethylene reactors is extended to take into account two radical generating sources, in addition to an injected initiator: a long-lived intermediate, possibly generated from the interaction of ethylene with trace amounts of oxygen, and the ethylene itself undergoing thermal polymerization. The first of these reactions can account for the smoothing of the temperature profile near the peak temperature, attributed by Lee to initiator and radical carryover; the second, whose inclusion is justified by experiments recently performed by Buback, can account for the explosive decomposition of ethylene known to occur in LDPE reactors if the temperature is allowed to exceed about 350 degrees C, and it also can contribute significantly to polymer production at very high temperatures. The contribution of both reactions must be evaluated quantitatively, if reliable heat transfer coefficients are to be obtained from experiment.