Determination of the sootblower activation moment for biomass co-firing in a pulverized coal furnace

Abstract

The pulverized coal-fired furnaces are expected to use co-firing with biomass for environmental reasons. Although the non-uniform ash deposits are formed on the furnace walls, the uniform deposits could be used for the analysis of the furnace operation. The objective of this investigation was determination of the uniform deposit thickness, used as a criterion for prediction of the sootblower activation moment in coal-biomass co-firing. The investigation comprised numerical simulations for uniform and non-uniform deposits to find the relative differences for the selected variables that were important for the sootblower activation: the mean wall fluxes and flame temperatures. The local thicknesses of the non-uniform deposits were determined by the gamma distribution for several mean and standard deviation values using the inversion method. The thicknesses of the uniform deposits were considered among the measures of central tendency: mode, mean, and median, of the non-uniform deposits. The mean was expected to provide the smallest relative differences, while the mode was excluded from further consideration after analysis of its values. The median was found to be better choice than the mean, as it provided smaller relative differences of the selected variables for the thick deposits, which were important for the sootblower activation. The method based on comparison of the uniform deposits for coal firing and those for the co-firing with biomass was proposed for the prediction of the sootblower activation moment. The method can be used for the selection of the operational regimes for coal-biomass co-firing.