Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 2. Na-Feldspar
Journal article, 2019

Selecting a suitable bed material for the thermochemical conversion of a specific feedstock in a fluidized bed system requires identification of the characteristics of potential bed materials. An essential part of these characteristics is the interaction of the bed material with feedstock ash in a fluidized bed, which leads to layer formation and morphology changes. For this purpose, the interaction of feldspar bed material with the main ash-forming elements in wood ash (Ca, K, Mg, Si) in an indirect gasification system was analyzed using SEM-EDS, XRD, and thermodynamic modeling. In part 1 of this work (DOI: 10.1021/acs.energyfuels.9b01291), the layer formation on K-feldspar dominated by Ca reaction and ash deposition was investigated. The aim of this second part of the work was to determine the time-dependent layer formation on Na-feldspar and compare the results with the findings for K-feldspar. Interaction of Na-feldspar with ash-derived elements resulted in different layers on Na-feldspar: K reaction layers, where K replaced Na and Si shares decreased; Ca reaction layers, where Ca enriched and reacted with the Na-feldspar; and ash deposition layers, where wood ash elements accumulated on the surface. Ca reaction layers were formed first and became continuous on the surface before K reaction layers and ash deposition layers were detected. Cracks and crack layer formation in the Na-feldspar particles were found after several days of operation. The layer compositions and growth rates indicate that the diffusion of Ca and K plays an essential role in the formation of Ca reaction and K reaction layers. The reaction with Ca and the crack formation coincide with the interaction previously found for quartz and K-feldspar. In contrast to K-feldspar, Na-feldspar showed high potential for reaction with K. The findings indicate that the reaction of Na- feldspar with ash-derived K makes Na-feldspar a less stable bed material than K-feldspar during the thermochemical conversion of K-rich feedstocks in a fluidized bed system.

Author

Thomas Karl Hannl

Robin Faust

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry

Matthias Kuba

Martin Seemann

Chalmers, Space, Earth and Environment, Energy Technology

Pavleta Knutsson

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry

Teresa Berdugo Vilches

Chalmers, Space, Earth and Environment, Energy Technology, Energy Technology 2

Marcus Ohman

Energy & Fuels

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

Vol. 33 8 7333-7346

Subject Categories

Inorganic Chemistry

Energy Engineering

Materials Chemistry

Bioenergy

Areas of Advance

Energy

Materials Science

DOI

10.1021/acs.energyfuels.9b01292

More information

Created

9/10/2019