Model based optimisation of tubular reactors for LDPE production

This paper presents a study on the model based optimisation of an industrial tubular reactor for the production of low-density polyethylene (LDPE). First a detailed reactor simulator is presented. Second, a well-posed optimisation problem is formulated. To this end, an economic cost function consisting of conversion and energy terms is derived and constraints due to operational and safety reasons are added. The degrees of freedom involve parameters such as the initiator feed rates, the cooling water temperatures and the switching position between hot and cold cooling water. The optimal design of a dual water circuit operating at a low and a high temperature achieved in this work allows significant improvements in conversion with respect to the reference case of a single temperature circuit, while maintaining similar molecular characteristics.