Multiscale modeling of turbulent combustion and NO_x emission in steam crackers

Abstract

in Wiley InterScience (www.interscience.wiley.com).A 3D RANS simulation of lean premixed turbulent combustion in an industrial scale steam cracking furnace is performed. Turbulence is represented by a renormalization group (RNG) k 2 e model, while combustion is modeled with a skeletal mechanism. The eddy dissipation concept (EDC) model is used to account for turbulence/combustion interaction. The turbulent combustion regime is identified as a ''thin flame regime with pockets'' or a ''corrugated flamelet regime''. A weighted sum of gray gases model (WSGGM) is used to account for the gas radiative properties. The radiative transfer equation is solved using the P-1 and discrete ordinates method in the conservative finite volume formulation. NO x calculations are performed as a postprocessing step, with the flow field, temperature, and species concentrations fixed. The formation of NO through thermal, prompt, and N 2 O intermediate mechanisms is considered. The in situ adaptive tabulation technique is used to decrease the computational time required to treat the combustion chemistry. The effect of radiation models on the predicted furnace wall, tube skin, and flue gas temperature profiles and heat fluxes toward the reactor tubes, as well as on the predicted species and NO concentration profiles and structure of the furnace flames under normal firing conditions, is discussed.

Application of the steady flamelet model on a lab-scale and an industrial furnace for different oxygen concentrations

“…Transport equation for the mean enthalpy is given in Eq. (11), where k t is the turbulent conductivity and S h is the source term.…”

“…The CFD model is able to predict the heat transfer as well as detailed resolution of the flow field inside the combustion chamber especially when measurements of temperature and species concentrations are difficult. Habibi et al [11] for example, investigated the heat flux and NOx concentrations in a steam cracking under airfired conditions. Another study on flow, combustion and heat transfer was done by Guihua et al [12] for an ethylene cracking furnace.…”

Large eddy simulation of upward flame spread on PMMA walls with a fully coupled fluid–solid approach

“…The eddy dissipation model was originally proposed by Magnussen et al [66]. The eddy dissipation model was extended to the eddy dissipation concept (EDC) model by giving the consideration of turbulence structures by Magnussen [67], and the models have since been widely applied to combustion simulations [68,69]. However, the original formulas were strongly dependent on grid resolutions [70], which was thought to be caused by the direct replacement of the total kinetic energy with the SGS kinetic energy [24].…”

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

“…The Heynderickx group then analysed the effect of several radiation models in Ref. [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].…”