Experimental analysis of biomass co-firing flames in a pulverized fuel swirl burner using a CCD based visualization system

• Coal-biomass co-firing impacts on flame characteristics are investigated.
• Biomass addition modifies flame brightness and luminous internal distribution.
• Spatial analysis of flame area is studied by statistical and spectral parameters.
• High CO emissions during unsteady combustion affect the flame luminous fluctuation rate.
• Some statistical flame parameters show a particular connection with CO emissions.

Biomass co-firing with pulverized coal in conventional, large-scale power plants is considered a low-cost strategy to reduce CO2 emissions and fossil-fuel dependence. This work analyzes the effects of biomass co-firing in the physical characteristics and oscillation patterns of the flame, by means of a digital imaging system installed in a 500 kWth semi-industrial scale swirl burner. The system is based on a monochrome CCD (Charged Couple Device) camera of high-speed frame rate (120 frames per second). Processing stage comprises the digital analysis in the spatial and spectral domain of recorded videos. Several co-firing flames with two biomass fuels (Cynara cardunculus and Populus sp.) were investigated, at substitution percentages ranging from 0% to 15%, energy basis. Spatial analysis of swirling flames highlights the effects of biomass addition in terms of luminous fluctuation rates and symmetry properties. With the joint analysis of flame derived parameters and CO emissions, flame flicker has been proved as a potential indicator of combustion performance. Additionally, a deeper investigation of luminous flame signal throughout its resulting histogram, have found new outcomes in the identification of instabilities of combustion process. Kurtosis and skewness parameters have shown an interesting response when CO emissions increase resulting in a promising option to develop monitoring and control systems based in non-intrusive measurements.

Figure optionsDownload as PowerPoint slide