Characterization of ash component desorption on novel bed material for fluidized bed boilers
Paper in proceedings, 2018
The use of biomass as a renewable fuel for production of heat and electricity is regarded as a key to reduce fossil fuel dependency, and thereby to reduce net CO2 emissions. Fluidized bed (FB) technology is widely accepted as the most energy efficient process for thermal conversion of biomass. One of the often-mentioned drawbacks is the building up of agglomerates within the process because of bed material-ash interaction. To avoid unplanned operational stops due to agglomeration, bed material is continuously replenished and spent bed material is removed in the form of bottom ash. The spent bed material cannot readily be reused and is usually deposited or used as construction filler material. Sand is the primary choice for bed material but novel bed materials are being tested to improve biomass conversion. Even though agglomeration is reduced and the energy efficiency of the conversion process is improved, bottom and fly ash are still being generated and need to be managed. To conceive new management strategies there is need to improve the understanding of the composition and stability of the compounds formed from the interaction between biomass ash and the novel bed materials. In the present work four bed materials (Olivine, Ilmenite, Feldspar and Manganese ore), all minerals, have been used in a biomass fueled 10MW CFB boiler. The materials have been sampled upon similar gas composition and time exposures in order to assure similarity in bed material “activity”. Bed material characterization followed by stepwise leaching have been used to identify opportunities in terms of pretreatment prior to deposition or/and the possibilities for alternative reuse.