A technique for separating molten polymer blends is investigated computationally. The device includes a rotating cylinder, separating the mixture components with different densities by the centrifugal force. Molten LDPE (Low-Density Poly(Ethylene)) and PET (Poly(Ethylene) Terephthalate) mixtures are investigated. The computational modeling is intended to evaluate the feasibility of such a technique at the time and length scales studied. A dispersed mixture model accounts for the immiscibility of the mixture components. The CFD simulations provide the field distributions of the flow field variables and of the mixture component fractions. The outlet composition and separation efficiency in the steady-state process, and the different process parameter influences on the process result, are studied. The polymer system at hand represents blends of postconsumer plastics. The study can therefore contribute to the development of a novel method for plastic waste recycling. With continuous feed and extraction of the polymer streams, the process can be automated.