Anticoking coatings for high temperature petrochemical reactors

Coke deposition is a major problem for several refinery and petrochemical p rocesses, among which steam cracking for ethylene production. Decreasing coking rates will reduce decoking frequency and will also decrea se heat transfer degradation. For these processes, a means of reducing coki ng phenomena is the application of anticoking coatings on the reactor walls . For this purpose a methodology was developed under a CEC Brite-Euram proj ect with steam cracking as the main application. A first selection of the coatings and their techniques of deposition was pe rformed according to their composition (non catalytic compounds), their res istance to carburization and oxidation and also according to the nature of the substrate. The feasibility of coating deposition was studied for small diameter furnace tubes and the techniques were perfected in particular with respect to the physicochemical characterization of the coatings and their resistance during thermal cycling and coking-decoking cycles. For the therm al cycling and the coking evaluation, industrial conditions were reproduced as closely as possible. For coking tests, a microreactor with complete mixing of the gas phase was developed for temperatures up to 950 degrees C. The coking behavior of the coated samples was compared with conventional refractory alloys: reduction of the coking rare by a factor of 3 was measured with the most promising co ating. This work was completed by the kinetic modelling of coking on uncoat ed materials.