Detailed experimental investigation of the spatially distributed gas release and bed temperatures in fixed-bed biomass combustion with low oxygen concentration

This work is focused on the experimental investigation of the fixed-bed conversion and release behavior in a 30 kW lab-scale reactor of a novel fuel flexible biomass combustion technology operated with a low oxygen concentration in the bed. The low oxygen concentration was obtained through a low primary air ratio and the additional supply of recirculated flue gas, reducing bed temperatures and therefore its inorganic emissions while increasing the feedstock flexibility. During the experiments, the reactor was operated with softwood chips with different water contents and Miscanthus, as well as with or without flue gas recirculation. All relevant components of the released gas, including gaseous species, light and heavy tars and water were measured with several techniques. The fuel bed temperature distribution was also measured. The distribution of the thermochemical conversion process in different zones inside the fuel bed were analyzed and the influence of process conditions such as flue gas recirculation, different fuels or a higher moisture content on the conversion behavior was discussed.