Fast pyrolysis of ash-rich biomass in bubbling fluidized beds: experimental work in ash removal, transport mechanisms, and management of operations.

In the past decades, challenges associated with depletion of fossil fuels have been increasingly under scrutiny from nation and international institutions (e.g. EU, UN). One way to tackle these issues could be the utilization of biomass for energy and chemicals production (e.g. Fischer-Tropsch reactions): in particular, biomass fast pyrolysis has been regarded as a promising solution due to the production of crude bio-oil, which could be applied in numerous cases. Among the challenges presented by biomass fast pyrolysis, the quality of the crude bio-oil as well as difficulties in the management of ash in the plant shall be highlighted. This study aims at deepening the understanding of ash management in biomass pyrolysis operations in accordance with the guidelines agreed upon by industrial and academic partners. The experiments carried out involve fast pyrolysis of woody biomass in a bubbling fluidized bed, analysis of pyrolysis products via gas chromatography for gas and liquid products, and reactivity studies of biomass pyrolysis and char combustion in ash removal strategies via thermogravimetric analysis with surface ionization method in order to better understand the mechanisms of ash volatilization. The results propose operating procedures for fast pyrolysis in bubbling fluidized beds, leaching procedures to vary the ash content in fed biomass, bio-oil composition evaluations under variable operating conditions, ash detection and transport mechanisms in char reactivity studies.