IMPACT OF THE BLENDING METHOD ON THE MELTING CHARACTERISTICS OF ASHES OF BIOMASS BLENDS

Multi-fuel firing has become a credible alternative to single fuel firing. Ash behavior of fuel blends could not be predicted according to single fuels in blend, i.e. ash melting behavior of the blends is not linear with the proportions of the fuel in blend. The standard method for the determination of ash melting behavior (CEN/TS 15370) lacks instructions for the preparation of ashes of fuel blends. This paper focuses on the blends of wheat straw pellets, Douglas fir wood chips, wood pellets, and reed. Two approaches for the preparation of ashes of fuel blends were applied: a) Approach 1 ("Ash blend") - fuels are ashed separately and then the ashes are blended according to certain proportions for the determination of ash melting behavior; b) Approach 2 ("Fuel blend") - fuels are blended according to a certain proportion and then the fuel blend is ashed. Two ashing temperatures of 550 degrees C and 850 degrees C were applied. Our results showed no remarkable differences in ash melting behavior between different approaches of ash preparation at the ashing temperature of 550 or even 850 degrees C.