The reduction and prevention of carbon dioxide emissions is a main concern in the development of modern power plant systems. As the safe supply of electrical power has to be guaranteed within the next decades, conventional plants relying on combustion technologies will still be essential and must be further enhanced. A promising method for the reduction of CO2 emissions is oxy-fuel combustion used in combination with carbon capture and storage (CCS) systems. Instead of using air in the combustion process, fuel particles are burnt within an atmosphere of oxygen and recirculated flue gas. This approach leads to a CO2-enriched flue gas and allows for an efficient separation of CO2, therefore, significantly lowering greenhouse gas emissions. The combustion characteristics are altered with the replacement of nitrogen with recirculated flue gas, which can be observed in different temperature and velocity profiles as well as combustion instabilities. For a detailed understanding of the chemical and physical processes, the SFB/Transregio 129 Oxyflame (www.oxyflame.de) supported by the German Research Foundation (DFG) (www.dfg.de) was set up in 2013. Its objective is the development of methods and models to achieve predictive engineering as a tool for the design of burners and boilers operated at oxy-fuel conditions.
The combustion of solid fuel particles is investigated under various flow configurations, therefore, allowing for a detailed understanding of the influence of turbulence, particle number density, and oxidizer compositions on the ignition and combustion of coal and biomass. For this purpose, two test rig environments equipped with optical diagnostics systems are used in project B7 of SFB/TRR 129. Experimental studies conducted in a laminar flow reactor (Fig. 1) enable a deeper insight into the different stages of single particle combustion as well as particle cloud flames for low flow rates. A microwave plasma heater (Fig. 2) is utilized for studying the interaction between auto-igniting particles and the turbulence properties of the surrounding oxidizer flow. Optical diagnostics such as laser-induced fluorescence (LIF), diffuse back-illumination (DBI), and particle image velocimetry (PIV) are applied to gather extensive experimental data sets. The combination of the findings from both test bench environments enable a better comprehension of the combustion in oxy-fuel conditions as well as the improvement of associated numerical models.
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