Burning Velocities of Coal-derived Syngas Mixtures

Summary Integrated gasification combined cycle (IGCC) systems, which utilize coal, petroleum coke, heavy oil, biomass and waste materials as a feedstock, continue to enter the power generation market. The gasification products from gasifiers using these feedstocks are mixtures of hydrogen, carbon monoxide and inerts like nitrogen, carbon dioxide and water. These mixtures are then used as a fuel in low-emission power generation applications. Unlike natural gas or methane, which has been widely used and researched for many years, these mixtures have not been widely investigated. Thus the aim of this study is to provide data on the combustion properties of syngas mixtures, mainly focusing on laminar burning velocities and critical strain rates to extinction. These combustion properties data are essential for gas turbine combustor modelling using turbulent burning velocity closure models. The establishment of such a database in this study mainly relies on numerical computations. Therefore, the experimental campaign was limited to investigation of several CO/H2/N2 fuel mixtures fuel mixtures at different equivalence ratios and operating conditions. The laminar burning velocity values, obtained from the experimental campaign were used mainly for validation of the chemical kinetics model and reaction mechanism. The principal outcome from this study is that at ambient conditions and reactant preheat temperatures up to 400K experimental laminar burning velocity values compare well with numerical predictions. The laminar burning velocity tests at high pressure presented a number of complications due to the formation of cellular flames and the flow in theburner tube entering the transitional laminar to turbulent regime. As a result the numerical model could not be fully validated experimentally for high pressure conditions. A comprehensive combustion properties database has been created using numerical simulations, based on comprehensive descriptions of the chemical kinetics and extensions using neural networks. CFD simulations of reacting flows in a practical combustor geometry demonstrated the importance of obtaining accurate laminar burning velocities and critical strain rates to extinction data.