Syngas Oxidation Mechanism

Abstract

A comprehensive analysis of synthesis gas (syngas) oxidation kinetics in wide ranges of temperature, pressure, fuel-to-air equivalence ratio, and fuel composition is performed on the basis of the reaction mechanism of syngas ignition and combustion in air. A vast set of experimental data on the ignition delay time, laminar flame propagation velocity, and time evolution of mole fractions of the basic species, which were obtained in shock tubes and in a flow reactor, is used for verification of the kinetic model. Based on a sensitivity analysis, it is shown that the role of reactions determining the basic characteristics of ignition and combustion depends on the composition of the fuel-air mixture and the syngas proper.

On the role of excited species in hydrogen combustion

“…Findlay and Snelling [88] summarized earlier measurements of collisional deactivation of singlet oxygen and concluded that hydrogen-containing species possess efficiencies close to molecular oxygen, which was recently confirmed for hydrogen [89], water [90], and a range of hydrocarbons [91]. This was attributed to weak chemical interaction otherwise manifested in reaction (31) or reaction between O 2 (1 ) and H 2 O discussed in the following. The measurements of deactivation rate constants for H 2 and H 2 O at room temperature show good consistency and recent accurate results [89,90] are adopted in the present work.…”

“…The rate constant of reaction (X7) originates from the calculations of Karkach and Osherov [62] and is significantly smaller than that of reaction (31). The existence of the reverse reaction has not been completely ruled out [83,84], yet there is no data to substantiate the significance of it.…”

“…For consistency, all these rates were taken from the work of Findlay and Snelling [88]. The values for N 2 and Ar used in our previous work [34] and based on the measurements of Clark and Wayne [80,92] were apparently overestimated due to experimental problems [81] discussed above in relation to reaction (31). The temperature dependence obtained for O 2 between 100 and 450 K [85] was assumed for other colliders with exception of atomic oxygen and hydrogen.…”

“…Olm et al [33] presented extensive analysis of the performance of 19 recent hydrogen combustion models in comparison with ignition measurements in shock tubes and rapid compression machines, burning velocity measurements and concentration-time profiles in jet-stirred and flow reactors, covering wide ranges of temperature, pressure and equivalence ratio. The analysis indicates that the performance of the mechanism of Starik et al [31] is far from being satisfactory and cannot be recommended for the modeling of hydrogen combustion.…”

“…Most recent models of Starik et al [13,18,31,32] seem to properly incorporate reaction H 2 + O 2 = H + HO 2 (14) as initiation step in the absence of excited species. However, overall performance of these mechanisms in hydrogen combustion modeling was shown to be unsatisfactory.…”