Radiation Modeling in Oxy-Fuel Combustion Scenarios

Abstract

Three gray models for the radiative properties of gases were examined for their usage in oxy-combustion simulations of a full scale boiler with flue gas recycle. Fully coupled computational fluid dynamic (CFD) simulations of a full scale boiler were carried out employing the weighted-sum-of-gray-gases model (WSGGM) at air burn, dry-recycle and wet-recycle conditions. The resulting thermal and composition fields were then frozen and the radiative properties of the gaseous media recomputed employing the Exponential Wide Band Model (EWBM) and correlations for total emissivities of gas mixtures. It is shown that when high CO2/H2O ratios were encountered within the boiler such as in dry-recycle scenarios, employing emissivity correlations developed for purely CO2 media within the models can result in incorrect gas properties. The errors associated with this can be significant when there are large pockets within the furnace where the gas radiation dominates the particle radiation.

Calculations of gas thermal radiation transfer in one-dimensional planar enclosure using LBL and SNB models

“…The extremely rapid variation of the radiative properties of real gases (primarily CO 2 and H 2 O in combustion) with wavelength makes it difficult to predict thermal radiation transfer accurately and efficiently. Various models have been developed in the literature over the last few decades, which include the line-by-line (LBL) model, narrow band models, wide band models, and global models.…”

“…Radiative properties of CO 2 and H 2 O have received continuous research attention in the last few decades mainly because they are required to model radiative transfer in various applications, such as remote-sensing, atmosphere science, heat transfer, and combustion and fires. The last two decades have witnessed a rapid development of efficient and yet accurate non-gray gas radiative property models for the ultimate application to large-scale threedimensional engineering problems.…”

“…Prior to the availability of HITEMP2010, earlier versions of LBL databases, such as HITEMP1995, HITRAN2004, and HITRAN2008, had been employed for LBL calculations. The CDSD database [37][38][39][40], which is more accurate for CO 2 , also was included in the present evaluation study.…”

“…In this work, LBL programs were developed to calculate the absorption coefficients of CO 2 The objectives of this study are threefold: (1) to evaluate the effect of spectral database on the LBL results of radiative heat transfer by performing LBL calculations using several different spectral databases, including HITEMP1995, HITRAN2004, HITRAN2008, HI-TEMP2010, and CDSD-1000 (updated), (2) to evaluate the accuracy of the SNB model by comparing the SNB results obtained using the EM2C SNB parameters against the LBL results using the HITEMP2010 database, and (3) to provide updated benchmark solutions of radiative heat transfer with the assumption that HI-TEMP2010 is currently the most accurate spectral database at high temperatures. In the next section, the LBL method, several highresolution spectral databases, and the SNB model are first presented.…”

“…The last two decades have witnessed a rapid development of efficient and yet accurate non-gray gas radiative property models for the ultimate application to large-scale threedimensional engineering problems. Accurate CFD modeling of the recently developed oxy-fuel combustion technologies has generated renewed interest in assessing the suitability of traditional weighted-sum-of-gray-gases (WSGG) models and developing efficient and accurate gas radiative property models under very high concentrations of CO 2 for large-scale and 3D CFD calculations [1,2].…”