Coke deposition and run length in industrial naphtha thermal cracking furnaces via a quasi-steady state coupled CFD model

Mathematical modelling of the thickness of the coke layer growing over months in millisecond cracking reactors is a dilemma in computational fluid dynamics (CFD) simulation. To address the time scale issue, a quasi-steady state (QSS) approach was employed through a comprehensive coupled reactor/firebox CFD model in the current study. The model was applied to predict the time-dependent behaviour of coke deposition and to determine the appropriate operating conditions for maximum olefin yields over an industrial furnace run length. A novel algorithm was designed to overcome the complexity of QSS simulation of the CFD model, which is a combination of reactive turbulence flow, combustion, and radiation models. The furnace parameters were studied as a function of two variables: the dilution steam-to-feed ratio and the liberated heat by the burners. The results indicated that the run length can be extended by up to 20% while retaining the main product yields. This study offers practical suggestions to maximize the run length in the operation.