The knowledge of reaction rates and reaction pathways is essential for the upscaling of laboratory- and pilot-sized plants to full scale industrial processes. Over the last decades lumped kinetic modelling became the standard modelling approach for cracking reactions of hydrocarbon blends. In this paper a sequential nine-lump kinetic model is developed. The model allows for a fully automatic calculation of the kinetic parameters and efficient implementation in process simulation software like PetroSim. The kinetic parameters were calculated using experiments in a laboratory sized tubular reactor with a mass throughput between 600 g h−1 and 2500 g h−1 and temperatures between 440 °C and 530 °C at a pressure of 15 bar. A feedstock of 30 wt% plastic in different blends (PP, LDPE, HDPE) and 70 wt% carrier medium, a heavy refinery intermediate product, was used for the fitting and evaluation of the kinetic model. The results were evaluated with a set of experimental data, independent from the set used for the fitting. A residual analysis shows that the model has good predictive capabilities and can be used to simulate the cracking reaction of plastics in a plug flow reactor over a broad range of operating conditions.