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A novel catalytic coating that converts coke to carbon oxides through a reaction with steam has been developed. Several coating formulations were tested in a jet-stirred reactor setup, and the best performing formulation was further evaluated in a pilot plant setup. Application of the coating during steam cracking of ethane at industrially relevant conditions resulted in a reduction of the asymptotic coking rate by 76%. The coating activity remained constant over several coking/decoking cycles. Coupled furnace-reactor run length simulations of an industrial ethane cracking unit were performed and resulted in an increase of the run length by a factor of 6. However, the simulated CO2 yield is higher than the design value of a typical caustic tower.

The use of one-dimensional reactor models to simulate industrial steam cracking reactors has been one of the main limiting factors for the development of new reactor designs and the evaluation of existing three-dimensional (3-D) reactor configurations. Therefore, a 3-D computational fluid dynamics approach is proposed in which the detailed free-radical chemistry is for the first time accounted for. As a demonstration case, the application of longitudinally and helicoidally finned tubes as steam cracking reactors was investigated under industrially relevant conditions. After experimental validation of the modeling approach, a comprehensive parametric study allowed to identify optimal values of the fin parameters, that is, fin height, number of fins, and helix angle to maximize heat transfer. Reactive simulations of an industrial Millisecond propane cracker were performed for four distinct finned reactors using a reaction network of 26 species and 203 elementary reactions. The start-of-run tube metal skin temperatures could be reduced by up to 50 K compared to conventionally applied tubular reactors when applying optimal fin parameters. Implementation of a validated coking model for light feedstocks shows that coking rates are reduced up to 50%. However, the increased friction and inner surface area lead to pressure drops higher by a factor from 1.22 to 1.66 causing minor but significant shifts in light olefin selectivity. For the optimized helicoidally finned reactor the ethene selectivity dropped, whereas propene and 1,3-butadiene selectivity increased with a similar amount. The presented methodology can be applied in a straightforward way to other 3-D reactor designs and can be extended to more complex feedstocks such as naphtha.

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Three fully coupled Computational Fluid Dynamics (CFD) simulations of a complete industrial steam cracking furnace equipped with floor burners are performed. The influence of the flue gas radiative properties and burner geometry on the flame front in the firebox, the heat transfer to the coils and the product selectivities has been investigated. A nine‐band model developed from the Exponential Wide Band Model (EWBM) is used as nongray gas radiation model to compare with the gray gas implementation of Weighted Sum of Gray Gas Model for the evaluation of the flue gas radiative properties. The gray gas radiation model predicts a flue gas outlet temperature that is 70 K lower than the temperature obtained with the nongray gas radiation model, resulting in a 3.6% higher thermal efficiency and 44 K higher average Coil Outlet Temperature (COT). Important differences between the 22 reactors in the furnace are seen because of shadow effects with and without accounting for the detailed burner geometry. The maximum difference between the COT of different reactors in the furnace caused by shadow effects is about 29 K which corresponds to a propene‐over‐ethene difference of 0.1. Full furnace CFD simulations prove thus to be essential in design and during debottlenecking, when aiming for a more uniform COT distribution to the reactors by feed or fuel distribution. © 2015 American Institute of Chemical Engineers AIChE J, 2015 2014 American Institute of Chemical Engineers AIChE J, 61: 936–954, 2015

As large floor-fired furnaces have many applications in refinery and (petro-) chemical units and about 80% of heat transfer in these furnaces is by radiation, the accurate description of radiative heat transfer is of the most importance for accurate design and optimization. However, the impact of using different radiation models in coupled furnace/reactor simulations has never been evaluated before. Therefore coupled furnace/reactor simulations of an industrial naphtha cracking furnace with a 130kt/a capacity have been conducted.Computational fluid dynamics simulations were performed for the furnace side, while the onedimensional reactor model COILSIM1D was used for the reactor simulations. The Adiabatic, P-1, discrete ordinates model (DOM) and discrete transfer radiation model (DTRM) were evaluated for modeling the radiative heat transfer. The results with DOM and the DTRM radiation model are very similar both on the furnace and the reactor side. The flue gas temperature using DOM is higher than when using the P-1 radiation model, resulting in higher incident radiation. Comparing the simulated results of all radiation models to the industrial product yields and run lengths shows that DOM and DTRM outperform the others. As DOM has a broader application range than DTRM, and because the current implementation of DTRM in FLUENT/14.0 cannot be run in parallel yet, DOM is the recommended radiation model for run length simulations of steam cracking furnaces.