KINETICS OF HYDROGEN - OXYGEN - ARGON AND HYDROGEN - OXYGEN - ARGON - PYRIDINE COMBUSTION USING A FLAT FLAME BURNER

RICHARD CARL PETERSON, Purdue University

Abstract

Fuels such as coal, oil shale and residual oils contain nitrogen which is converted to HCN, NO and N(,2) during combustion. The utilization of these energy sources in an environmentally acceptable manner requires combustion strategies which maximize conversion of bound nitrogen to the desirable product N(,2). To understand the process of HCN, NO and N(,2) formation, a comprehensive fuel nitrogen reaction mechanism is proposed, tested and verified in this study. Both H(,2)-O(,2)-Ar and H(,2)-O(,2)-Ar-Pyridine flames are considered; the former have a known reaction mechanism and are used to verify the flame analysis procedures while the latter simulate the combustion of the nitrogeneous portion of coal or heavy oils. Experimental flame data is obtained using three diagnostics: a thermocouple (temperature), optical absorption (OH and OH rotational temperature) and a sampling probe (NO via chemiluminescent analyzer; HCN and NH(,3) via bubbler and ion specific electrodes; H(,2),O(,2), Ar, N(,2), N(,2)O, CO, CO(,2) and CH(,4) via two gas chromatographs). Water is determined by an argon atomic balance. Two flame analysis procedures are used. Integration of the conservation equations determines species and temperature profiles for direct comparison with measured data; profile comparison in the H(,2)-O(,2)-Ar flames shows that strongly non-adiabatic flames can be accurately modeled. The reaction rate analysis method calculates the rate coefficient of an elementary reaction from the species reaction rate (determined from the measured mole fraction profile) and the measured mole fractions of species involved in the reaction. A novel trace-additive approach adds pyridine to the H(,2)-O(,2)-Ar flames such that the concentrations of the most important flame radicals (H, O and OH) are not significantly perturbed from an H(,2)-O(,2)-Ar flame with the same equivalent ratio, flame speed and relative amount of O(,2) and Ar. Hence, calculated profiles for H, O and OH obtained in the H(,2)-O(,2)-Ar flame can be used in the reaction rate analysis of the flame with pyridine. From the H(,2)-O(,2)-Ar-Pyridine flames a comprehensive fuel nitrogen reaction mechanism is proposed and verified. The rate coefficients of three reactions HCN + OH (--->) HNCO + H NH + O (--->) NO + H NH + NO (--->) N(,2)O + H are determined from experimental data. The mechanism describes HCN destruction, formation of NO, N(,2) and N(,2)O and is consistent with all fuel nitrogen data in the literature. Both experimental data and calculated results show maximum N(,2) conversion at an equivalence ratio of 1.3 - 1.4.

Degree

Ph.D.

Subject Area

Mechanical engineering|Energy

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