On completion of the first life cycle of plastics various recycling processes are available for further utilization of these evaluable materials. The choice of process will depend upon the materials to be recycled. In chemical recycling polymers are degraded to basic chemical substances which can be reused in the petrochemical industry. This route plays a key role for soiled waste plastics or waste plastics which could not hitherto be recycled. The pyrolysis of acrylic polymers provides a good basis for comparing a fluidized bed reactor and a tubular reactor with regard to reactor modelling. The tubular reactor with internal mass transport is a simplified model for a rotary kiln. Parameters relevant for reactor design and scale-up are presented.