Comparison of Ash Layer Formation Mechanisms on Si-Containing Bed Material during Dual Fluidized Bed Gasification of Woody Biomass
Journal article, 2020

Quartz, feldspar, and olivine are minerals commonly used as bed materials for dual fluidized bed gasification of biomass. During their interaction with biomass ash, the materials develop surface layers rich in ash-derived elements. These layers decrease the concentration of tar which is an unwanted side product of gasification. The interactions of quartz, feldspar, and olivine with woody biomass ash leading to the formation of active layers were studied with X-ray diffraction, scanning electron microscopy- energy dispersive X-ray spectroscopy, and iime-of-flight secondary ion mass spectrometry, and the results were compared to calculations done with FactSage. It was found that the interaction causes the formation of three-layered structures for all materials: a Mg-rich surface layer, a Ca-rich intermediate layer, and an inner layer which varies among the three materials. For quartz and feldspar, the integration of Ca and Mg into the structure causes a transition by depolymerizing the tectosilicate structure via an inosilicate intermediate to finally a nesosilicate. As the olivine structure is a nesosilicate from the beginning, no further depolymerization of the silicate structure can occur and a substitution of Mg by Ca occurs, leading to an accumulation of expelled MgO on the surface. The interaction of the materials with K was found to differ, causing melt formation for quartz, a substitution of Na-rich feldspar by K-rich feldspar, and the formation of feldspathoids for alkali feldspar, or retention as a separate phase for olivine.


Robin Faust

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Teresa Berdugo Vilches

Chalmers, Space, Earth and Environment, Energy Technology

Per Malmberg

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry

Martin Seemann

Chalmers, Space, Earth and Environment, Energy Technology

Pavleta Knutsson

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Energy & Fuels

0887-0624 (ISSN) 1520-5029 (eISSN)

Vol. 34 7 8340-8352

Subject Categories

Inorganic Chemistry

Physical Chemistry

Materials Chemistry


Chalmers Materials Analysis Laboratory



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