Title: Development of Comprehensive Detailed and Reduced Reaction Mechanisms for Synagas and Hydrogen Combustion PI: Chih-Jen Sung Case Western Reserve University Department of Mechanical and Aerospace Engineering Cleveland, OH 44106 Tel: (216) 368-2942 Fax: (216) 368-6445 E-mail: cjs15@case.edu Subcontractor: Hai Wang, University of Southern California Angela Violi, University of Michigan Grant Number: DE-FG26-06NT42717 Performance Period: 3/1/2007 – 2/28/2008 ABSTRACT Objective This project aims to develop tools necessary for the design of future coal derived syngas and hydrogen (SGH) fueled combustion turbines. A set of benchmark experiments and computations will be carried out to map laminar flame speeds, autoignition delays, and extinction limits of SGH/oxidizer mixtures over a wide range of mixture compositions, inlet temperatures, and pressures. These fundamental combustion properties will in turn be used to develop comprehensive detailed and reduced kinetic models for H 2 /CO/H 2 O/O 2 /N 2 chemistry. Additionally, the resulting experimental database will be of practical use in determining the desired syngas compositions for optimal IGCC operation, as well as improving the design and operation of advanced combustors fueled by SGH. Accomplishments to Date Using the counterflow burner apparatus, laminar flame speed measurements were conducted for a CO-rich fuel gas mixture, H 2 /CO mole ratios of 5/95, at a preheat temperature of 323 K. Effects of water addition on flame propagation over a wide range (0 to 35% of the fuel mixture) were studied for equivalence ratios of 0.6–0.9. The molar percentage water addition is defined as [(X H2O )/(X H2 +X CO +X H2O )]×100%. It was found that with water addition the laminar flame speed responded non-monotonically for the CO-rich fuel mixture. The flame speed increased with water addition from 0 to 15% and then decreased from 15 to 35%. Detailed integrated flux flow analysis was also carried out using a recently developed chemical kinetic mechanism to understand the controlling chemistry responsible for such non-monotonic behavior. To further examine the effect of water addition for various H 2 /CO ratios, laminar flame speeds for fuel gas mixtures with H 2 /CO ratios of 5/95, 10/90, 15/85 and 20/80, were determined at equivalence ratio of 0.6 and water addition of 0–35%. It was found that the non-monotonic behavior was most pronounced for H 2 /CO=5/95. The extent of non-monotonicity decreases with increasing H 2 /CO ratio. It was also noted that the peak of laminar flame speed occurred at a lower value of water addition when the H 2 /CO ratio was increased. For H 2 /CO ratio of 20/80, the laminar flame speed response with water addition was strictly monotonically decreasing. The results indicate that for H 2 /CO ratio less than 15/85, laminar flame speed varies non-monotonically with addition of water. However, beyond this value of H 2 /CO ratio of 15/85, water addition decreases the laminar flame speed. Furthermore, ab initio quantum chemical calculations, master equation modeling, and detailed kinetic modeling were used to resolve the remaining kinetic issues in syngas combustion. The reaction CO + HO 2 → CO 2 + OH was examined using the single-reference CCSD(T) method with Dunning’s cc-pVTZ and cc-pVQZ basis sets and multireference CASPT2 methods. It was found that the classical energy barriers are about 18 and 19 kcal/mol for CO + HO 2 addition following the trans and cis paths. The HOOCO adduct has a well-defined local energy minimum in the trans configuration, but the cis conformer is either a very shallow minimum or an inflection point on the potential energy surface. This observation led us to treat the cis pathway with conventional transition state theory and the trans pathway with a master equation analysis. The computation showed that the overall rate is independent of pressure up to 500 atm. Upon a careful treatment of the hindered internal rotations in the HOOCO