Searching for improved characterization of ash forming matter in biomass

Characterization of ash forming matter in biomass fuels provides a key knowledge for better ash behavior predictions in flue gases.  In this paper the chem. fractionation based on selective leaching of a no. of biomass fuels is reported, i.e. Finnish and Swedish pine bark and Scandinavian wood.  Two samples of Finnish peat and a coal are included as ref. materials.  Extended leaching tests were carried out with the Finnish bark and wood.  Here different amts. of leaching agent were used.  It was shown that leaching with 20 mL NH₄Ac​/g fuel during 24 h is sufficient to reach equil.  Further tests should be carried out in order to check whether a one, two or three- step procedure is necessary.  In case of leaching with HCl it is shown that a liq. amt. of 20 mL HCl​/g fuel is sufficient to reach equil.  In the future, tests will be carried out in order to check whether a two-​step procedure is necessary and if the HCl-​leaching also could be carried out at room temp. instead of at 70°C as done here.  SEM​/EDX anal. of untreated solid samples, of samples after leaching and of lab. ashed samples was used in an attempt to verify the fractionation results and to distinguish between internal and external minerals in the fuel.  It was shown that depending on the origin and biol. function of a biomass fuel, it will contain included minerals (as in the bark studied here- for sturdiness) and​/or external minerals (soil contamination)​.  The improved anal. of the ash-​forming matter gives a solid starting point for more accurate prediction of ash deposit formation.