Abstract: The invention relates to a device for depolymerizing used and waste plastics, comprising a closed reactor and a circulation system the mildly heating of the reactor contents connected to the reactor, as well as to a process for depolymerizing used and waste plastics. To protect the circulation system from erosion by solid particles contained in the reactor contents, the reactor is designed so that the reactor contents drawn off into the circulation system traverse a riser section integrated into the reactor for removing fairly coarse solid particles having correspondingly high settling rate before entry into the take-off line.