Design of solid biofuels blends to minimize the risk of sintering in biomass boilers

Abstract Biomass with high concentration of alkali/alkaline and silica components can lead to slagging/fouling, and sintering of the ash deposits, causing corrosion and erosion of the boilers. There are several methods to predict bed agglomeration such as slagging/fouling indexes. However, these indexes are developed to be used for coal ashes, which shows a different behaviour than biomass fuels. The aim of this work was to determine the suitable percentage of different species found in biomass blends in order to reduce the risk of slagging and sintering. We studied the ash behaviour of 24 blended biomass samples using two slagging indexes: the alkali index, and the % of bases in ashes index, and we validated these two indexes with the Bioslag test, and with the Hardness Index (%D1). There is low risk of slagging in most of the samples, as well as a low sintering risk. However, some samples present moderate risk of sintering possibly due to SiO2. The Bioslag test and the %D1 test support our results. Samples showing risk of sintering exceed 25% of the total accumulated ash weight percentage ac%_1P>25%, and show a hardness of %D1 > 0.7. These validations can be considered as useful tools for estimating slagging and sintering of woody biomass fuels in domestic pellet boilers.