(53ad) Coatalloy ™ Barrier Coating for Reduced Coke Formation in Steam Cracking Reactors: Experimental Validation and Simulations

CoatAlloy â„¢ barrier coating for reduced coke formation in steam cracking reactors: experimental validation and simulations

Authors: Olahova N.¹, Sarris S.A.¹, Djokic M.¹, Van Geem K.M.^1,*, Couvrat M.^2,*, Riallant F., Chasselin H.²

¹ Laboratory for Chemical Technology, Department of Chemical Engineering, Ghent University, Technologiepark 918, B-9052 Zwijnaarde, Belgium

² Manoir Industries, 12 Rue des Ardennes BP8401 - Pitres 27108 VAL DE REUIL Cedex

Steam cracking is one of the most important sources of valuable base chemicals, such as olefins and aromatics. One of the process’ major byproduct is a carbonaceous residue deposited on the walls of the reactor. This coke layer strongly affects both the production and energetic efficiency as well as economics of the process. Considering this issue, the development of coke-reducing technologies is continuously expanding. One of these technologies is the application of a coating on the internal surface of steam cracker furnace coils. Distinction can be made between barrier coatings that passivate the inner coil wall and catalytic coatings that convert coke to carbon oxides ¹. CoatAlloy â„¢ is a newly developed barrier coating, it is multilayered with diffusion barriers to tolerate extreme aging without losing its efficiency.

Foremost, the anti-coking capability of the coating over a reference alloy was experimentally tested in an electrobalance setup ². The influence of two different pretreatments, presulfidation and continuous sulfur addition was investigated during cyclic aging. The tested samples were subsequently examined using scanning electron microscopy (SEM) and energy diffractive X-ray (EDX) together with X-ray photoelectron spectroscopy and wavelength-dispersive X-ray spectroscopy for surface and cross-section analysis. The barrier coating was found to perform better than the reference material after identification of a proper pretreatment while no effect on the product distribution was observed. Presulfidation of the coating has a negative effect on the observed coking rates in comparison with the reference alloy. In addition, nitrogen proved to be detrimental for the anti-coking performance of the coating.

Next to this, the barrier coating was also studied on a larger scale in the LCT pilot plant using a reactor with an internal diameter of 26 mm. The coating is compared to the same reference alloy under typical industrial conditions in a well-controlled and monitored environment ³. The influence of several process conditions, such as coil outlet temperature, presulfidation, continuous sulfur addition and aging was evaluated. The applied coating resulted in reduced measured quantities of coke as well as yields of CO and CO₂ compared to the uncoated coil. The surface of both tested reactor materials was studied by means of the SEM and EDX. Further scale up was assessed by coupled simulation of an industrial ethane cracker. All these findings showed that the barrier coating can reduce coke formation and maintains anti-coking activity over multiple cracking-decoking cycles.

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