Impact of flue gas radiative properties and burner geometry in furnace simulations

Abstract

Three fully coupled Computational Fluid Dynamics (CFD) simulations of a complete industrial steam cracking furnace equipped with floor burners are performed. The influence of the flue gas radiative properties and burner geometry on the flame front in the firebox, the heat transfer to the coils and the product selectivities has been investigated. A nine‐band model developed from the Exponential Wide Band Model (EWBM) is used as nongray gas radiation model to compare with the gray gas implementation of Weighted Sum of Gray Gas Model for the evaluation of the flue gas radiative properties. The gray gas radiation model predicts a flue gas outlet temperature that is 70 K lower than the temperature obtained with the nongray gas radiation model, resulting in a 3.6% higher thermal efficiency and 44 K higher average Coil Outlet Temperature (COT). Important differences between the 22 reactors in the furnace are seen because of shadow effects with and without accounting for the detailed burner geometry. The maximum difference between the COT of different reactors in the furnace caused by shadow effects is about 29 K which corresponds to a propene‐over‐ethene difference of 0.1. Full furnace CFD simulations prove thus to be essential in design and during debottlenecking, when aiming for a more uniform COT distribution to the reactors by feed or fuel distribution. © 2015 American Institute of Chemical Engineers AIChE J, 2015 2014 American Institute of Chemical Engineers AIChE J, 61: 936–954, 2015

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

“…The flue gas absorption-emission bands are introduced for the first time in this work. The band upper and lower limits for each band have been taken from Zhang et al [ 18 ]. The participating species, water, and carbon dioxide, present in the flue gas of gas-fired furnaces, emit and absorb radiation in these wavelength ranges.…”

“…Additionally, the surface has to reflect as much radiation as possible in the solar spectrum, situated between 0.3 and 2.5 µm, for daytime radiative cooling applications [ 17 ]. For gas-fired furnaces, almost all radiative heat transfer occurs in the thermal infrared wavelength range, 0.8–25 µm [ 18 ]. Hence, the industrially used high emissivity coatings maximize the emissive properties over the entire wavelength range.…”

Review: Thermal ceramic coatings as energy saving alternatives for high temperature processes

“…Figure 5 highlights the main differences regarding the absorption and emission behavior between solids and fluids. The particular aspect of the spectral absorption of gases has been widely explored to enhance the heat transfer in industrial facilities 24,45,46 …”

Computational Fluid Dynamics-Based Study of a High Emissivity Coil Coating in an Industrial Steam Cracker

“…The governing equations and closure models are only briefly described. For a more detailed discussion on the furnace− reactor simulations, the reader is referred to Zhang et al 16 For further details on the convection section simulations, the reader is referred to Verhees et al 23 2.1. Tubular Reactors.…”

“…obtain the reaction rates for the fuel combustion. The reactions and the associated kinetic parameters are taken from the work of Stefanidis et al 28 and Zhang et al 16 and are given in Table 1. The turbulence−chemistry interaction is accounted for via the finite-rate/eddy-dissipation model.…”