Agglomeration phenomena in a pilot scale BFB combustor fired with a biomass fuel

The paper presents and discusses the results concerning agglomeration phenomena manifested during an experimental campaign with a pilot scale BFB combustor fired with a biomass fuel (pine seed shells). Extensive bed agglomeration and defluidization was experienced after around 30 hr of operation under typical conditions for fluidized bed combustion. The aggregates obtained from discharged bed materials were subjected to SEM/EDX analysis that demonstrated the enrichment in potassium and the consequent formation of glassy structures. Interactions between sand and char/ash particles clearly appear from the inspection of a number of coarse aggregates that well resemble the original fuel particle. The bed agglomeration was rapidly monitored by the effect played on the measured variables that rapidly departed from their stationary values.