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Folkeson, Björn, 2014. Propensity of bed materials used in dual fluidized beds to retain ash-forming elements from biomass fuels. Second cycle, A2E. Uppsala: SLU, Dept. of Energy and Technology



The main aim of this work was to investigate the propensity of bed materials to retain ash-forming elements from biomass under conditions relevant to dual fluidized bed
gasification (DFBG). The investigation was carried out in a laboratory-scale bubbling fluidized bed reactor in which biomass was gasified with steam and the unconverted char
was combusted in the temperature range 800–900 ° C. Three bed materials (sand, olivine and bauxite) and two biomass fuels (forestry residue and wheat straw) were studied.
From the results obtained and literature on the ash transformation chemistry during thermal conversion of biomass, it was found that the extent to which ash-forming
elements from biomass are retained on bed materials depend among other factors on (1) the abundance of ash-forming elements in the fuel, (2) the ability of the bed material to
react and form compounds with ash-forming elements and (3) the atmosphere surrounding the fuel in the reactor. For example, Ca, P and K (which were among the most abundant ash-forming elements in the forestry residues) were also the main ashforming elements retained on sand, olivine and bauxite during thermal conversion of the forestry residues. However, the retention of these elements differed on the three bed materials. With respect to reactor atmosphere, Ca and P were retained on olivine primarily during char combustion while the retention of K on olivine was somewhat
similar during gasification and char combustion.

In addition to the experimental results, the effect of the retention of ash-forming elements on bed agglomeration tendency and the composition of the product gas is discussed as well as the relevance of the obtained results for the DFBG process.

Main title:Propensity of bed materials used in dual fluidized beds to retain ash-forming elements from biomass fuels
Authors:Folkeson, Björn
Supervisor:Larsson, Gunnar and Placid, Atongka Tchoffor
Examiner: Nordberg, Åke
Series:Examensarbete / Institutionen för energi och teknik, SLU
Volume/Sequential designation:2014:20
Year of Publication:2014
Level and depth descriptor:Second cycle, A2E
Student's programme affiliation:TE2SY Energy Systems Engineering (admitted before July 1, 2010) 300 HEC
Supervising department:(NL, NJ) > Dept. of Energy and Technology
Keywords:fluidized bed, ash retention, gasification, combustion, bed material
Permanent URL:
Subject. Use of subject categories until 2023-04-30.:Renewable energy resources
Deposited On:12 Dec 2014 12:41
Metadata Last Modified:12 Dec 2014 12:41

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