Influence of air staging variation on agglomeration behavior of biomass fuels in fluidized bed technology

Abstract

The fluidized bed system is an effective approach widely accepted and commonly used for the thermochemical conversion of solid fuel such as biomass and agricultural residue. In most instances, there are some demerits usually associated with this approach such as development of eutectic mass, increased process of melting and bed agglomeration. This work was carried out to study the behavior of five readily available biomass fuels (Palm tree fronds, corn straw, plantain peels, sugarcane bagasse and domestic woods) in a bubbling fluidized bed (BFB) combustor. Characterization of the bed materials and ash samples were done using SEM-EDX, XRF and XRD. The effect of physical factors on the composition of obtained ash and particles from the bed was assessed. Also, the interaction between the fuel ash and bed particle was evaluated to reveal its influence on bed materials morphology. The results obtained revealed a combustion efficiency that varies between 96.2 to 99.6 % with the highest value obtained for sugarcane bagasse. The corn straw has the highest Potassium (K) content, while the domestic wood ash contained the highest Calcium (Ca) content. The XRF analysis revealed the conversion of the major potassium content of the corn straw to K2O. Meanwhile, bed agglomeration was absent when combustion was carried out with no staging-air as well as with staging air, despite high temperature above 800 oC used. Data obtained from this work revealed that agglomeration effect will be minimal issue when carrying out fluidized bed combustion of the selected biomass.