New weighted-sum-of-gray-gases model for typical pressurized oxy-fuel conditions

Abstract

Summary Pressurized oxy‐fuel combustion technology has received considerable attention due to its ability to improve the overall system efficiency and to control CO2 emissions. The characteristics of radiation heat transfer are significant for pressurized oxy‐fuel gas mixture and different from those under atmospheric conditions. Therefore, to calculate the radiation characteristics of pressurized oxy‐fuel gas mixture quickly and accurately, new weighted‐sum‐of‐gray‐gases (WSGG) model for pressurized oxy‐fuel conditions was first presented in this paper, which was applied in 3 typical high pressure conditions: 5, 10, and 15 bar. The new WSGG model correlations were suitable for pressurized conditions with a molar ratio range of 0.125‐2, temperature range of 400‐2500 K, and path length range of 0.1‐20 m. Calculations for a variety of typical pressurized oxy‐fuel combustion cases showed that the new WSGG model can accurately predict the radiation characteristics and heat transfer characteristics of the gas mixtures compared with the SNB model benchmark. In addition, the application of the previous atmospheric WSGG models yielded non‐ideal results under pressurized conditions. Consequently, the new model can provide efficient and accurate radiation heat transfer results for pressurized oxy‐fuel conditions and can be used to design pressurized oxy‐fuel combustion furnaces or boilers.

A novel flame energy grading conversion system: Preliminary experiment and thermodynamic parametric analysis

“…Generally, radiation transfer occurs with participating media in pulverized coal combustion. It cannot be simply regarded as gray body radiation due to the presence of soot, CO 2 , and H 2 O . Nevertheless, the characteristics of the spectral radiation distribution still follow the basic law of radiation; thus, it was observed in this experiment that the proportion of radiative energy increased in the spectrum range below 4.1 μm and decreased in the spectrum range above 4.1 μm.…”

“…In Equation , p is pressure and an atmospheric pressure of 0.1 MPa is used here; l is the path length and l = 3.6 V / F , where V is the furnace volume and F is the furnace wall area; κ is the flame radiation extinction coefficient: where κ g is the gas extinction coefficient, which is calculated using the weighted sum of gray gases (WSGG) model; in this study, r g is the radiative gas volume fraction; κ ah is the fly ash extinction coefficient, which is estimated as , where d ah is the ash particle diameter, which is set as 13 μm; μ ah is the fly ash concentration; κ ch is the coal char extinction coefficient, which is set as 10 (m MPa) −1 , x 1 = 1 for anthracite, x 1 = 0.5 for lignite and bituminous coal, and x 2 = 0.1 for pulverized coal furnace. The estimation method and parameters of fly ash extinction coefficient are all based on Bauer…”

“…where κ g is the gas extinction coefficient, which is calculated using the weighted sum of gray gases (WSGG) model 46,47 ; in this study, r g is the radiative gas volume fraction; κ ah is the fly ash extinction coefficient, which is estimated as κ ah = 55900= ffiffiffiffiffiffiffiffiffiffiffi ffi T 2 g d 2 ah 3 q , where d ah is the ash particle diameter, which is set as 13 μm; μ ah is the fly ash concentration; κ ch is the coal char extinction coefficient, which is set as 10 (m MPa) −1 , x 1 = 1 for anthracite, x 1 = 0.5 for lignite and bituminous coal, and x 2 = 0.1 for pulverized coal furnace. The estimation method and parameters of fly ash extinction coefficient are all based on Bauer.…”

Combustion and heat transfer characteristics of co-firing biomass and coal under oxy-fuel condition

“…Some modeling strategies were refined for oxy‐fuel combustion because the combustion atmosphere has been changed. For instance, several researchers proposed modified models to simulate the radiative heat transfer process . For gas phase combustion, Westbrook and Dryer 2‐step mechanism and Jones and Lindstedt 4‐step mechanism were improved and investigated by Andersen et al Char combustion and gasification processes were also studied .…”

“…For instance, several researchers proposed modified models to simulate the radiative heat transfer process. [10][11][12] For gas phase combustion, Westbrook and Dryer 2-step mechanism and Jones and Lindstedt 4-step mechanism were improved and investigated by Andersen et al 13 Char combustion and gasification processes were also studied. [14][15][16] Comparatively, the combustion atmosphere has little influence on devolatilization process.…”