09/11/2010
Co-firing Black Liquor and Biomass
Mills having recovery boilers with excess capacity can potentially mix other biofuels into the black liquor to produce more electricity from biomass. This work is a laboratory study of the effect on combustion of mixing other biofuels with black liquor. The four fuels mixed with softwood black liquor were bark, wood chips, peat, and bio-sludge (which some mills already burn with black liquor). Droplets of the mixed fuels were burned at 1100°C and 3% O2 in a single particle reactor. Video and on-line gas analyzers for CO, CO2 and NO were used to measure swelling, combustion times, carbon evolution (CO+CO2), and NO formation tendency. Changes in swelling, char burning, and NO formation were found, but the results indicate that mixing biofuels with black liquor may be a reasonable method of producing additional electricity. (TAPPI J., Sept.2010)