Effect of bed material on agglomeration of bed particles in CFB burning pellets from Arundo Donax

Xiaofei Long, Jianbo Li, Shengqi Yuan, Runxia Cai, Mingyi Chen, Yuanyuan Zhang, Xiaofeng Lu and Dongke Zhang

Energy, 2025, vol. 330, issue C

Abstract: This contribution details a piece of innovative work elucidating the effect of bed material on particle agglomeration during CFB combustion of a high-potassium biomass, Arundo Donax. Experiments were performed in a lab-scale CFB at 900 °C using quartz or Si-lean material as bed material, during which bed particles were discharged every 2-h and subjected to be examined. Severe agglomeration was observed for quartz particles but not for Si-lean bed material. Characterisation using SEM-EDX, XRF, XRD, XMT and FactSage calculation showed that quartz particle agglomeration was initiated by molten ash and strengthened by K/Ca-silicate coating layer of low melting-points. A considerable amount (7.4 %) of K2O was found in the agglomerates, leading to a liquid proportion as high as 32.6 % in the coating layer. The Si-lean bed material rich in mainly Ca/Al/Fe/Mg showed an insignificant agglomeration propensity because its Al constituents have dissolved into the fuel ash to generate K aluminosilicates owing to its lowest Gibbs free-energy, thereby reducing the liquid proportion by 12.1 %. Meanwhile, K-species were found to be captured and retained inside bed particles, inhibiting consequent formation of K-rich layer. With a negligible K2O content of 2.0 % in particle agglomerates, both the melt-induced and coating-induced pathways for agglomeration initiation, by using the studied alternative bed material, were therefore mitigated.

Keywords: Agglomeration; Alternative bed material; Arundo Donax; Biomass; Circulating fluidised bed (CFB); Potassium (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:330:y:2025:i:c:s0360544225025022

DOI: 10.1016/j.energy.2025.136860

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