Evaluation of high-emissivity coatings in steam cracking furnaces using a non-grey gas radiation model

The efficiency of the application of high-emissivity coatings on the furnace walls in steam cracking technology can only be evaluated on the asis of a description of radiative heat transfer distinguishing between the frequency bands. To this end, a non-grey gas radiation model based on he exponential wide band model (EWBM) has been developed and applied in the context of three-dimensional CFD simulations of an industrial aphtha cracking furnace with side-wall radiation burners. Applying a high-emissivity coating on the furnace wall decreases the net outgoing adiation from the furnace wall in the absorption bands and increases the net outgoing radiation from the furnace wall in the clear windows. Since adiation that is emitted by the furnace wall and travels through the flue gas in the clear windows can reach the reactor tubes without partially eing absorbed by the flue gas, contrary to radiation that is emitted by the furnace wall and travels through the flue gas in the absorption bands, the hermal efficiency of the furnace increases. It was found that application of a high-emissivity coating on the furnace walls improves the thermal fficiency of the furnace (∼1%), the naphtha conversion (∼1%) and the ethylene yield (∼0.5%). These differences are small but, considering the ndustrial importance and scale of the steam cracking process, significant. 2007 Elsevier B.V. All rights reserved.