Oxy-Fuel Combustion Modeling: Performance of Global Reaction Mechanisms

Abstract

Three global reaction mechanisms derived for oxy-fuel combustion and one global reference mechanism are investigated and compared under gaseous oxy-fuel combustion conditions. The aim is to evaluate their prediction of major in-flame species and temperature by comparison with a detailed reaction mechanism (validated for oxy-fuel conditions) and experimental data. The evaluation is performed using a 1D plug flow reactor (PFR) method and 3D CFD calculations. Through the PFR calculations, it is found that the global mechanisms all predict a too early onset of fuel oxidation compared to the detailed mechanism. Furthermore, the global reference mechanism predicts gas concentrations more in line with the detailed mechanism than the oxy-fuel mechanisms, which yield incorrect reaction sequences. In the CFD analysis, significant differences in the predicted gas concentrations and temperature fields between the global mechanisms show that the choice of reaction mechanism strongly influences the results. In summary, the global reference mechanism is a preferable alternative to represent the combustion chemistry when modeling oxy-fuel combustion using CFD, if the use of a detailed reaction mechanism is prohibited due to computational limitations.

Numerical Study of the Combustion Characteristics of Propane–Oxyfuel Flames with CO2 Dilution

“…However, the forward rate exponent of H 2 O (having a value of 0.5) needs to be included as it affects the reaction due to H 2 O presence in the combustion mixture. , Also, the rate exponent of the H 2 O is used in the calculation of the pre-exponential factor, A , in proper units for importing it into the Fluent software. The mechanism is adopted from the work of Hjärtstam et al where the dissociation reactions were modified from original Jones–Lindstedt to account for changes in oxyfuel combustion.…”

“…The most accurate of such predictions can be achieved by the use of detailed chemical mechanism which is computationally very expensive. Ultimately it is common practice in CFD to use reduced and global chemical mechanisms which are comparatively less expensive and give reasonable degree of accuracy. , Some of the global mechanisms modified for oxyfuel combustion reported in the literature include the work of Hjärtstam et al, Frassoldati et al, and Andersen et al…”

“…Ultimately it is common practice in CFD to use reduced and global chemical mechanisms which are comparatively less expensive and give reasonable degree of accuracy. 17,18 Some of the global mechanisms modified for oxyfuel combustion reported in the literature include the work of Hjartstam et al, 19 Frassoldati et al, 20 and Andersen et al 21 There have been some numerical studies focusing on oxyfuel combustion in the literature. These includes a study using detailed combustion mechanism, and thermodynamics analysis on oxyfuel combustion characteristics in gas turbine modes, 22 study on the role combustion chemistry and radiation heat transfer plays in oxyfuel combustion modeling, 23 and study on combustion and heat transfer properties in a retrofitted 600 MW utility boiler.…”

Synergistic Removal of SOx and NOx in CO2 Compression and Purification in Oxy-Fuel Combustion Power Plant

“…Recently, carbon dioxide emissions have gained increasing research attention. Anthropogenic CO 2 emissions are the main cause of global warming, and power plants are the main source of carbon dioxide emissions. − Oxy-fuel combustion technology can reduce the emission from coal-fired power plants and store CO 2 safely in an underground aquifer. , Oxy-fuel combustion is a CO 2 capture technology that is yet to be commercially applied . The technology achieves efficient coal combustion by using mixed O 2 and recycled flue gas.…”

Predicting Radiative Heat Transfer in Oxy-Methane Flame Simulations: An Examination of Its Sensitivities to Chemistry and Radiative Property Models

“…Consequently, the need to refine models for gas-phase chemistry and radiative properties that have previously been deemed to be accurate in computational fluid dynamic (CFD) simulations of combustion in air has garnered much attention in recent reviews [8,9]. This has led to the development and validation of gas-phase radiative property models in the form of weighted-sum-of-gray-gases (WSGG) coefficients based on different spectroscopic/model databases [10][11][12][13] and the refinement of kinetic parameters in previously proposed global kinetic mechanisms [14,15] to improve their prediction accuracy in oxy-combustion scenarios [16][17][18]. Summarized in Table 1 are the results from CFD simulations of oxy-methane/natural gas combustion employing these refined chemistry and radiative property models.…”