Dynamics and stability of ethylene polymerization in multizone circulating reactors
Document Type
Article
Publication Date
1-1-2009
Abstract
Multizone circulating bed reactors (MZCR) have the exclusive characteristics of producing polymers of different molecular weights in a single particle. Traditional fluidized bed reactors, on the other hand, can produce only one kind of molecular weight with relatively narrow distribution. A dynamic model for the MZCR is used to illustrate the basic dynamic behavior of the new reactor design used for polyethylene production. The model is used to study the copolymerization of ethylene with butene. Several parameter sensitivity analyses are performed to show the computer-simulated time responses for reactor temperature, number-average molecular weight, weight-average molecular weight, catalyst feed rate and the monomer/comonomer concentration along the reactor length. At certain operating conditions dynamic instability is observed and the results for the effect of cooling water temperature, catalyst feed rate, monomer and comonomer initial feed concentration on the reactor temperature and polymer molecular weight reveal that the system is very sensitive to disturbances in the heat exchanger coolant temperature. Also, at some operating conditions, the reactor temperature oscillates above the polymer melting temperature. Temperature runaway above polymer softening point is a serious problem which may cause polymer melting and hence reactor shutdown. The oscillatory behavior of the reactor temperature necessitates a suitable temperature control scheme to be installed.
Keywords
polyethylene, multi zone circulating reactor, ethylene, polymerization, gas-phase polymerization, fluidized-bed reactors, hybrid catalysts, copolymerization, size.
Divisions
fac_eng
Publication Title
Korean Journal of Chemical Engineering
Volume
26
Issue
3
Publisher
Korean Journal of Chemical Engineering
Additional Information
448GB Times Cited:3 Cited References Count:16