Conversion of Fuel Nitrogen during Combustion of Biofuel in a Fixed Bed - Measurements Inside the Bed

Paper in proceeding, 2006

The conversion of fuel nitrogen during combustion of biofuel pellets in a fixed bed is investigated experimentally. Measurements were performed in a quadratic (0.3x0.3 m2) reactor, with a bed height of about 0.4 m. The ignition front propagated from the top of the bed towards the grate, counter-current to the gas stream. The combustion in the batch-fired reactor can be divided into two phases. In the first phase, the fuel is ignited and devolatilised by the ignition front, and in the second phase the remaining char, accumulated above the front is burnt. When the ignition front propagates through the bed, NH3 is the dominant nitrogen compound measured and there are only small amounts of HCN and NO. During the char combustion phase when there was an excess of oxygen, only NO is detected. NO2 and N2O were not found in any of the two phases. The result can be used to validate models describing the conversion of nitrogen in a fixed bed of biofuel.