Mathematical modeling and optimal operation of industrial tubular reactor for naphtha cracking

The tubular reactor in a naphtha cracking furnace is modelled rigorously in this paper. The mathematical model can be used to predict product yields, coking buildup inside the tube wall, run length (i.e. the time between two consecutive decoking operations), residence time and pressure drop. A powerful modelling, simulation and optimisation tool gPROMS was chosen to implement the proposed work. This model provides detailed understanding of the naphtha cracking process. Steady-state optimisation was then applied to the operation of this industrial tubular reactor. The operating profit is maximised when the process gas temperature profile along the reactor and the inlet steam to naphtha ratio vary within certain ranges. The effects of coking on heat transfer, on reduction of manufacturing time and the decoking cost have been considered in the optimisation. Process simulation and optimisation based on this detailed model will give process engineers in the ethylene industry some insights on ethylene furnace design and operation.