Effect of CO2 and steam gasification reactions on the oxy-combustion of pulverized coal char |
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| Authors: | Ethan S. Hecht Christopher R. Shaddix Manfred Geier Alejandro Molina Brian S. Haynes |
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| Affiliation: | 1. Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84112, USA;2. Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550, USA;3. Universidad Nacional de Colombia-Sede Medellín, Facultad de Minas, Bioprocesos y Flujos Reactivos, Medellín, Colombia;4. School of Chemical and Biomolecular Engineering, University of Sydney, Sydney, NSW 2006, Australia;1. State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China;2. University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China;1. Instituto Nacional del Carbón, INCAR-CSIC, Apartado 73, 33080 Oviedo, Spain;2. Department of Energy Technology, Aalborg University, 9220 Aalborg East, Denmark;1. CIC Virtuhcon, Technische Universität Bergakademie Freiberg, Reiche Zeche, Fuchsmühlenweg 9, Haus 1, 09596 Freiberg, Germany;2. Department of Energy Process Engineering and Chemical Engineering, Technische Universität Bergakademie Freiberg, Reiche Zeche, Fuchsmühlenweg 9, Haus 1, 09596 Freiberg, Germany;1. School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;2. School of Energy and Power Engineering, Northeast Electric Power University, Jilin, 132012, China;3. Institute of Thermal Science and Technology, Shandong University, Jinan, 250061, China |
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| Abstract: | For oxy-combustion with flue gas recirculation, elevated levels of CO2 and steam affect the heat capacity of the gas, radiant transport, and other gas transport properties. A topic of widespread speculation has concerned the effect of gasification reactions of coal char on the char burning rate. To asses the impact of these reactions on the oxy-fuel combustion of pulverized coal char, we computed the char consumption characteristics for a range of CO2 and H2O reaction rate coefficients for a 100 μm coal char particle reacting in environments of varying O2, H2O, and CO2 concentrations using the kinetics code SKIPPY (Surface Kinetics in Porous Particles). Results indicate that gasification reactions reduce the char particle temperature significantly (because of the reaction endothermicity) and thereby reduce the rate of char oxidation and the radiant emission from burning char particles. However, the overall effect of the combined steam and CO2 gasification reactions is to increase the carbon consumption rate by approximately 10% in typical oxy-fuel combustion environments. The gasification reactions have a greater influence on char combustion in oxygen-enriched environments, due to the higher char combustion temperature under these conditions. In addition, the gasification reactions have increasing influence as the gas temperature increases (for a given O2 concentration) and as the particle size increases. Gasification reactions account for roughly 20% of the carbon consumption in low oxygen conditions, and for about 30% under oxygen-enriched conditions. An increase in the carbon consumption rate and a decrease in particle temperature are also evident under conventional air-blown combustion conditions when the gasification reactions are included in the model. |
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