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

Abstract

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

Standards for fired heater design: An assessment based on computational modelling

“…[9] and the formation of NO x emissions in steam crackers [10]. They also investigated the effect of high-emissivity coatings using a non-grey gas radiation model [11] and extended their model to a steam cracker convection section [12]. Guihua et al first reported a complete detailed coupled model of flow, combustion, radiative heat transfer and ethylene cracking reaction process which used a computational fluid dynamics (CFD) code [13].…”

Morphology controllable preparation and infrared emissivity of vanadium pentoxide

“…High infrared emissivity materials have widely been used in energy conservation equipment or thermal protective system [12][13][14]. In recent years, many attentions have been attracted to improve the infrared emissivity by changing the factors of component, crystalline size, heat treatment, doping [15,16].…”

SLW model for computational fluid dynamics modeling of combustion systems: Implementation and validation

“…Moreover, modeling of radiative heat transfer in the CFD solver necessitates an accurate and computationally efficient nongray radiative property estimation technique for all combustion environments. To achieve this objective, accuracy of different nongray WSGGM [10][11][12][13][14][15] and full-spectrum k-distribution method [16] was tested by comparing their predictions against those of gray WSGGM, all coupled with ANSYS FLUENT for different test cases. These studies imply that nongray gas radiative properties are necessary when modeling air-fuel, oxy-fuel, or oxy-enriched combustion.…”