Chemical forms of ash-forming matter in woody fuels for FBC

The prediction of the ash behavior in combustion processes is enhanced by the detn. of the ash-​forming matter in the fuel.  The scope of this work was to characterize Scandinavian wood fuels by studying the wood, bark and leaves from a spruce and an aspen.  Chem. Fractionation, a step-​wise leaching procedure that treat the fuel in water, ammonium acetate and hydrochloric acid, was used to det. the soly. of the ash elements.  The resulting solns. were farther analyzed on ionic species, which was coupled to the presence of salt compds. in the original biomass tissues.  The leaching procedure dissolved nearly 100​% of the ash-​forming matter.  The phosphorus (P)​, chlorine (Cl) and some of the sulfur (S) were readily leached with water and found present as HPO₄^2-​, SO₄^2-​ and Cl^-​ in the solns.  The simultaneous dissolving of potassium (K) in this step proved the presence of water sol. potassium salts in the biomasses.  The remaining K after the water treatment and all magnesium (Mg) dissolved completely in the ammonium acetate step together with a large part of the tissues' calcium (Ca) and manganese (Mn)​.  The remaining Ca after the second step was leached in hydrochloric acid together with equiv. amts. of oxalate ions, C₂O₄^2-​.  This proved the presence of acid sol. calcium oxalate in the tissues, a salt with low soly. in neutral pH.