Multi-reactor system and method for production of polyethylene and ethylene co-polymers

A process for monitoring the polymerization of ethylene or ethylene and comonomers in the presence of a free-radical polymerization initiator at pressures from about 10,000 psi to about 50,000 psi and at temperatures from about 320° F. to about 600° F. in a multi-reactor system, comprising the steps of:

• a) providing a multi-reactor system comprising a first polymerization reactor and a second polymerization reactor, wherein an inner volume of the first polymerization reactor is from about 30% to about 50% of an inner volume of the second polymerization reactor;
• b) measuring as process parameters the temperature profiles and the pressures of reaction mediums and the flow and temperature profiles of cooling mediums along each of the first and second polymerization reactors,
• c) monitoring the feeds of ethylene, free-radical polymerization initiator, chain-transfer agent, and, optionally, comonomer to each of the first and second polymerization reactors,
• d) calculating, based on process parameters and on a model for the polymerization process, concentrations for free-radical polymerization initiator, chain transfer agent, ethylene, and, optionally, comonomers at a sufficient number of positions along each the first polymerization reactor and the second polymerization reactor such that at least one calculation is carried out each 10 seconds for a volume unit flowing through the first polymerization reactor,
• e) calculating, based on the measured process parameters and the calculated concentrations, the cooling power, the generation of heat, and the concentration of radicals,
• f) calculating, based on the calculated data of the cooling power, of the generation of heat, and of the concentration of radicals, the probability of a thermal runaway of the reaction mixture at the positions along each of the first polymerization reactor and the second polymerization reactor which have the highest temperatures, and
• g) outputting an alarm signal or activating an interlock if the calculated value for the probability of a thermal runaway in either the first polymerization reactor or second polymerization reactor exceeds a predefined value.