The Effect of Refractory Wall Emissivity on the Energy Efficiency of a Gas-Fired Steam Cracking Pilot Unit

Abstract

The effect of high emissivity coatings on the radiative heat transfer in steam cracking furnaces is far from understood. To start, there is a lack of experimental data describing the emissive properties of the materials encountered in steam cracking furnaces. Therefore, spectral normal emissivity measurements are carried out, evaluating the emissive properties of refractory firebricks before and after applying a high emissivity coating at elevated temperatures. The emissive properties are enhanced significantly after applying a high emissivity coating. Pilot unit steam cracking experiments show a 5% reduction in fuel gas firing rate after applying a high emissivity coating on the refractory of the cracking cells. A parametric study, showing the effect of reactor coil and furnace wall emissive properties on the radiative heat transfer inside a tube-in-box geometry, confirms that a non-gray gas model is required to accurately model the behavior of high emissivity coatings. Even though a gray gas model suffices to capture the heat sink behavior of a reactor coil, a non-gray gas model that is able to account for the absorption and re-emission in specific bands is necessary to accurately model the benefits of applying a high emissivity coating on the furnace wall.

Assessing the CO2 emission reduction potential of steam cracking furnace innovations via computational fluid dynamics: From high-emissivity coatings, over coil modifications to firing control

“…The wall refractory emissivity is increased from 0.5 to 0.95. The value for the base case is obtained as an average from previous work [55], whereas the increased value is taken as an upper limit of the achievable emissivity using coatings [24,25].…”

“…Vandewalle et al performed dynamic computational fluid dynamics (CFD) simulations researching the impact of fouling on different reactor coil geometries [23]. The application of a high-emissivity coating to the refractory walls of steam cracking fireboxes improves the energy efficiency and reduces the CO2 emissions of the global steam cracking process, as investigated both experimentally and numerically by Vangaever et al [24,25]. This last CFD study used a simplistic combustion model and did not include any validation data.…”

Optimizing air distribution in floor and wall burners of an industrial steam cracking firebox: a CFD study

“…Vandewalle et al performed dynamic computational fluid dynamics (CFD) simulations researching the impact of fouling on different reactor coil geometries [27]. As demonstrated both experimentally and numerically by Vangaever et al, the application of a high-emissivity coating to the refractory walls improves the energy efficiency and reduces the CO2 emissions of the global steam cracking process [28,29]. Rebordinos et al studied different measures to increase energy efficiency in a steam cracking firebox [30].…”

Thermodynamic Irreversibility Analysis of Thermal Radiation in Coal-Fired Furnace: Effect of Coal Ash Deposits

“…These ash deposits decrease the boiler performance by being the leading obstacles to heat transfer [ 23 , 24 , 25 ]. Specifically, the ash deposits influence thermal radiation significantly because they alter wall emissivity [ 26 , 27 ]. From the point of view of the second law of thermodynamics, the ash deposits will have a significant effect on the REG and thermodynamic efficiency of radiative heat transfer in a furnace.…”