Optimization of co-Firing burners

At present, unless a boiler is especially designed to burn biomass, the levels of co-firing are generally limited to around 5% by mass. Higher levels of substitution sometimes lead to burner instability and other issues. In order to co-fire higher concentrations of biomass, a technique is required which can monitor flame stability at the burner level and optimize the combustion to ensure that local NO_x is maintained below set limits. This paper presents an investigation of a system that monitored the combustion flame using photodiodes with responses in the ultraviolet (UV), infrared (IR), and visible (VIS) bands. The collected data were then processed using the Wigner-Ville joint time-frequency method and subsequently classified using a self-organizing map (SOM). It was found that it was possible to relate the classification of the sensor data to operational parameters, such as the burner airflow rate and NO_x emissions. The developed system was successfully tested at pilot scale (500 kW_t), where the ability of the system to optimize the combustion for a variety of unseen coal/biomass blends was demonstrated.