Search

Oxy-fuel coal combustion is a promising Carbon Capture and Storage technology that allows retro-fitting of existing power plants. Due to high concentrations of CO 2 and H 2 O and the strong and irregular spectral variation of their absorption coefficients, prediction of radiative heat transfer in oxy-fuel combustion systems requires a non-grey gas radiation model. Several models, including narrow-band correlated-k (NBCK), wide-band correlated-k (WBCK), full-spectrum correlated-k (FSCK), and weighted-sum-of-grey-gases (WSGG) models, were used to predict radiative heat transfer by CO 2 and H 2 O in a three-dimensional real-size virtual coal-fired furnace under air- and oxy-fuel (dry and wet flue-gas recycle) conditions. The best agreement with the benchmark solution calculated by the NBCK model with the updated EM2C parameters is achieved by the FSCK model. The WBCK model is less accurate. The WSGG parameter sets of Kangwanpongpan et al. (2012) and Bordbar et al. (2014) are most suited for oxy-fuel combustion among the six sets considered. The FSCK model offers the best performance in terms of both accuracy and computational efficiency among the considered gas radiation models and is recommended for CFD simulations of real-sized oxy-coal systems. [ABSTRACT FROM AUTHOR]

Abstract: In this study, new coefficients for the weighted-sum-of-gray-gas (WSGG) model are proposed based on the up-to-date HITEMP2010 database. The coefficients are determined for gas mixtures of water vapor and carbon dioxide with partial pressure (or molar concentration) ratios equal to 1.0 and 2.0, representing typical products of the combustion of fuel oil and methane. The correlations are valid for pressure path-lengths ranging from 0.001atmm to 10atmm, and for temperatures varying between 400K and 2500K. The WSGG model with the new coefficients are applied to the solution of the radiation heat transfer in non-isothermal, non-homogeneous gas mixtures, which are then compared with benchmark line-by-line solutions to access the accuracy of the model for a few illustrative test cases. Results show that, in spite of its simplicity in comparison to modern gas models, the WSGG model is still a competitive alternative to provide fast but reliable solutions of radiation heat transfer in non-uniform media. [Copyright &y& Elsevier]

Abstract: Presumed shape multi-environment Eulerian PDF Transport method (MEPDF), which involves representing the joint composition PDF shape as a collection of finite number of Delta functions, has been used to model the turbulence-chemistry interactions. The governing transport equations are solved for the probability and the probability weighted mass fraction of species and enthalpy in an Eulerian frame. The radiation heat transfer is included using the non-gray modeling of the radiative properties of the medium by weighted sum of gray gases (WSGG) considering four fictitious gray gases. The absorption coefficients as well as the weight functions of the gray gases are calculated from published literature as a function of the species mass fraction and temperature. The effect of turbulence radiation interaction (TRI) is included using an empirical relations for emission enhancement. The combined tool is then used to model two pilot stabilized hydrocarbon flames (Sandia Flame D and Delft Flame III) with realistic finite rate chemistry. A parametric study of the micro-mixing constant is performed to understand its impact in flame stabilization. In case of Delft Flame III, two different pilot treatments are considered and also the impact of pilot flame power is studied with the MEPDF model. The current model results have been compared with the experimental data and also with the Lagrangian solution of the joint composition PDF transport equation. The discrepancies of the current predictions with the experimental data and other published results have been quantified and discussed. [Copyright &y& Elsevier]

In this work, radiative heat transfer in axisymmetric Controlled Profile Reactor, fired with a pulverized coal combustion jet is studied. Radiation is investigated numerically by the Finite Volume Method (FVM). The developed numerical code is validated by comparing its predictions of the radiative heat flux with published experimental measurements. The non gray feature of the medium is analyzed using the Weighted Sum of Gray Gases Model (WSGG). Then the effects of the gas and particles distribution on the radiative heat flux and on the radiative source term are presented. Finally, the influence of the gas and particle distributions and of the temperature fluctuations on the radiative transfer is investigated. [ABSTRACT FROM AUTHOR]