Dynamic simulation and operation of a high pressure ethylene-vinyl acetate (EVA) copolymerization autoclave reactor

Abstract

Polyethylene (PE) is one of the most widely used polymers in chemical industry. In all the PE processes, low density polyethylene (LDPE) process is generally considered as the most profitable segment of the polyethylene business worldwide. There are two basic processes used for the manufacturing of LDPE: autoclave and tubular reactor, where autoclave reactor is often used to produce high-value specialty-type grades including ethylene-vinyl acetate (EVA) copolymer. Depending on different grades of the product, reactor zone temperatures in this autoclave process can be in the range 150–230 °C and pressure in the range of 1500–2000 kg/cm 2. In this paper, dynamic simulation of an industrial EVA copolymerization reactor will be established. Industrial operating condition data of seven product grades with melt index ranging from ones to over four hundred will be used as fitted data to obtain the key kinetic parameters in the model. The predicted outputs of melt index, vinyl acetate wt.% in polymer, and polymer production rate will be compared to plant data. This dynamic model was used in determining the controller tuning constants of the three important zone temperature control loops of the autoclave reactor and was also used for comparative study of various operating policies during grade transition.