Staged pressurized oxy-coal combustion (SPOC), which is a promising technology being developed at the Washington University at St. Louis (WUSTL) aiming to be used for low-cost, low-emission, high-efficiency power generation, is investigated numerically using the ANSYS Fluent commercial package. The modelling supports the WUSTL experimental endeavors in a 100 kW lab-scale reactor, with 90% of energy coming from the coal and 10% originating from methane-air combustion. To be specific about the burner design, carbon dioxide is injected alongside the coal, for its carriage. In addition, a small amount of methane is also injected alongside the coal to maintain a steady flame. Steady and unsteady Reynolds-Averaged Navier-Stokes (RANS) simulations are performed resulting in an asymmetric flame shape. We propose several potential causes of such a flame asymmetry including peculiarities of the coal injection and the onset of the shear-layer instability occurring because the densities and velocities of the mixing streams. As a result, an influence of the presence of coal on the flame symmetry is demonstrated. In addition, a benchmark at which the further increase of coal would result in flame asymmetry has been found.This work is performed in cooperation with the Washington University at St. Louis (WUSTL). It is sponsored by the US Department of Energy (DoE) through the US-China Clean Energy Research Center – Advanced Coal Technology Consortium (CERC-ACTC).

Staged pressurized oxy-coal combustion (SPOC) is nowadays a promising technology to be used for low-cost, low-emission, high-efficiency power generation. The objective of this thesis is to compliment the experiments ongoing at the Washington University, St. Louis (WUSTL) by means of numerical simulations, thereby providing better understanding of the fluid flow, turbulence, combustion characteristics, particle dynamics and heat transfer. Carbon dioxide (CO2) is injected alongside the coal, for its carriage. A small amount of methane (CH4) is also injected alongside the coal to maintain a steady flame. The simulations are performed for a 3D geometry with the following energy source distribution: out of 100 kW in a lab-scale reactor, 10 kW originates from CH4 and 90 kW comes from coal combustion. Steady and unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are performed resulting in an asymmetric flame shape. Two causes of the flame asymmetry are hypothesized: (i) influence of coal injection and (ii) onset of a shearlayer instability due to the density variation of different gases and velocity differences of various streams in a shear layer, where mixing occurs. An impact of coal on flame symmetry is shown. In addition, a benchmark at which the further increase of coal would result in flame asymmetry has been found. The present simulations also demonstrated an occurrence of vortex shedding when the flow passes over a disk (bluff body) in a reactor, used to stabilize the flame, constituting a potential reason for periodic flame oscillations observed. An aerodynamic investigation of a flow past this bluff body is conducted for various Reynolds numbers (Re), with the bluff body height determining the characteristic length scale. Consequently, various regimes of flow are identified as Re increases. Particularly, an onset of the vortex shedding is noticed when Re > 3000. Spectral analysis is further conducted to identify the frequencies at which the flame oscillations occur, which is aimed at guiding an eventual redesign of this bluff body. It is shown that coal injection is the major contributor to the flame oscillations, as hypothesized. A non-uniform coal distribution in the burner region is found, which, in turn, creates a non-steady coal feed and ultimately results in the flame oscillations. It is subsequently demonstrated that an increase in the coal carrier (CO2) concentration provides a better feeding of coal (continuous coal injection into the burner region), ultimately resulting in a more symmetric shape of the flame front. iii ACKNOWLEDGEMENTS I would like to thank everyone who has contributed, directly or indirectly, to my activities at West Virginia University, in general, and to completing this thesis, in particular. Specifically, my heart felt gratitude goes to Dr. Akkerman, my research advisor, who has entrusted the responsibility to work on a research field as interesting as this one. Furthermore, my heart felt gratitude goes to Ozioma Ozor, who has remained a permanent source of encouragement...

Staged pressurized oxy-fuel combustion is an advanced technology to be employed for the combustion and carbon capturing processes. This technology is promising because of relatively low costs, low emissions and high-efficient power generation with exhausting pressurized carbon dioxide. Our computational combustion group at West Virginia University performs a numerical study of a lab-scale SPOC reactor by using the ANSYS Fluent software for steady and unsteady Reynolds-averaged Naiver-Stokes simulations as well as large-eddy simulations aiming to support the experiments on SPOC ongoing at Washington University in St. Louis,. The simulations consider the total power to be 100 kW, varying the inputs from coal and methane, with CO2 being the coal carrier. The ultimate computational goal is to continuously reduce the portion of CH4 and eventually perform the LES of pure coal combustion generating 100 kW without no assistants of CH4. In present work, the numerical analysis involves a two-phase flow, turbulence, heat transfer as well as the flame and particle dynamics. The species transport model with the finite rate/eddy dissipation turbulence-chemistry interaction is used for coal combustion, along with a non-premixed combustion model for coal-CH4 burning. The discrete ordinates model for radiation is employed. Being successful with the RANS for pure coal, we are currently on the transition to the LES of pure coal.

Staged pressurized oxy-coal combustion (SPOC) – a technology developed at Washington University at St. Louis (WUSTL) – is nowadays a promising tool for low-cost/emissions, high-efficiency power generation. The present computational simulations, performed at West Virginia University (WVU) by means of the ANSYS Fluent package, compliment the experimental research for better understanding of the impacts of turbulence, fluid flow, flame/particle dynamics, and heat transfer on oxy-coal combustion. Here, CO2 is injected alongside the coal, for its carriage, while a small amount of CH4 is also injected alongside the coal to maintain a steady flame. Out of 100 kW in a lab-scale reactor, 10 kW originates from CH4-air burning and 90 kW comes from coal combustion. Steady and unsteady RANS simulations are performed resulting in an asymmetric flame shape. Three causes of the flame asymmetry are hypothesized: (i) coal injection, (ii) onset of the shear-layer instability due to various stream velocities and densities in a shear layer, where mixing occurs, and (iii) presence of the vortex shedding due to the flow past a bluff body, which is used to stabilize the flame. As a result, an impact of the presence of coal on the flame symmetry is demonstrated, and a benchmark at which further increase of coal would result in flame asymmetry is found. The present simulations also shows occurrence of the vortex shedding when the flow passes over a disk in the reactor used to stabilize the flame, constituting a potential reason for the periodic flame oscillations experienced in the result.This work is performed in cooperation with the Washington University at St. Louis (WUSTL). It is sponsored by the US Department of Energy (DoE) through the US-China Clean Energy Research Center – Advanced Coal Technology Consortium (CERC-ACTC).