Cost function design for economically optimal grade changes for a polyethylene gas phase reactor

This paper considers optimization of stationary production and dynamic grade changes for a gas phase polyethylene reactor. The designed cost function considers costs of inflows and revenues from produced polymer. At dynamic optimization, the cost function uses grade variable intervals for defining on-grade polymer and includes economical incentives to produce on-target polymer. Additionally, it also considers a preparatory time interval prior defined transition time, used for economical preparation of reactor state. A previously published model of a gas phase reactor is used and several grade changes are optimized, showing the effects of an economical cost function.