Oxy-coal combustion studies - Task 3 topical report, Utah Clean Coal Program.

The objective of this task is to move toward the development of a predictive capability with quantified uncertainty bounds for pilot-scale, single-burner, oxy-coal operation. This validation research brings together multi-scale experimental measurements and computer simulations. The combination of simulation development and validation experiments is designed to lead to predictive tools for the performance of existing air fired pulverized coal boilers that have been retrofitted to various oxy-firing configurations. In addition, this report also describes novel research results related to oxy-combustion in circulating fluidized beds. For pulverized coal combustion configurations, particular attention is focused on the effect of oxy-firing on ignition and coal-flame stability, and on the subsequent partitioning mechanisms of the ash aerosol. To these ends, the project has focused on: ~ The development of reliable Large Eddy Simulations (LES) of oxy-coal flames using the Direct Quadrature Method of Moments (DQMOM). ~ Extending the previous project phases by exploring how coal composition affects flame stand-off distance and flame ignition. ~ Development and application of optical diagnostic techniques to a 100 kW scale pulverized-coal flames in order to obtain experimental data for computational fluid dynamics model validation. ~ Comparison of results from oxy-coal combustion in a bench-scale bubbling fluidized-bed (BFB) reactor and a pilot-scale circulating fluidized-bed (CFB). ~ Evaluation of limestone sulfation mechanisms under air firing and oxy-firing conditions as well as parametric effects of temperature, CO2 concentration, and heating rate on CO2 capture capacity of limestone looping under CFB conditions. ~ Development of a detailed kinetic model to identify steam and CO2 gasification to include in oxy-combustion models. ~ Evaluation of the effects of: oxygen concentration, combustion environment (CO2 versus N2), furnace temperature, coal type (Utah Skyline, Illinois #6, and Black Thunder PRB), and gas-phase conditions on particulate formation. ~ Cases of oxy-coal combustion with various recycled flue gas (RFG) options and various RFG amounts were conducted on oxy-fuel combustor (OFC).