Abstract Agglomeration is one of the main challenges for combustion and gasification of biomass in fluidized beds. Bed agglomeration is related to K species present in biomass. Understanding the role of different types of K species on formation of agglomerates at different conditions can reveal the mechanisms of biomass ash induced agglomeration. Extensive experiments are conducted in a laboratory scale fluidized bed reactor, using mixtures of quartz sand and K species, including KCl, K2SO4 and K2CO3, to study the agglomeration mechanisms. The effects of gas composition, including air, H2– and H2O– containing gas are investigated. The morphology and elemental analyses of the agglomerate samples are examined by SEM/EDS analysis. Thermodynamic equilibrium calculations are performed for verifying the proposed mechanisms. The results show that the role of various forms of potassium salts on agglomeration in fluidized beds is different. Gas composition also has strong impact on the agglomeration tendency. In the air and H2-containing gas, defluidization of KCl in a sand bed is caused by the melt of KCl. However, KCl reacts with SiO2 to form K-silicates in the H2O-containing gas, which results in a lower defluidization temperature. No defluidization is observed for K2SO4 in the presence of oxygen or water. However, K2SO4 decomposes and reacts with SiO2 to form K-silicates, causing defluidization at 850 °C in the H2-containing gas. In the air, H2– or H2O-containing gas, K2CO3 would react with SiO2 to form potassium silicates and KOH may be additionally formed in the H2– and H2O-containing gas. The possible mechanisms of agglomeration of various potassium salts at different conditions are discussed.

中文翻译：

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生物质灰在流化床中引起团聚。第 2 部分：钾盐对不同气体成分的影响

摘要 团聚是流化床中生物质燃烧和气化的主要挑战之一。床团聚与生物质中存在的 K 物种有关。了解不同类型 K 物种在不同条件下对团聚体形成的作用可以揭示生物质灰诱导团聚的机制。在实验室规模的流化床反应器中进行了大量实验，使用石英砂和 K 物质（包括 KCl、K2SO4 和 K2CO3）的混合物来研究团聚机制。研究了气体成分的影响，包括空气、含 H2– 和 H2O– 的气体。通过SEM/EDS分析检查附聚物样品的形态和元素分析。执行热力学平衡计算以验证所提出的机制。结果表明，不同形态的钾盐对流化床团聚的作用不同。气体成分对团聚倾向也有很大影响。在空气和含 H2 气体中，KCl 在砂床中的脱流是由 KCl 的熔体引起的。然而，KCl 与 SiO2 反应在含 H2O 的气体中形成 K-硅酸盐，这导致较低的脱流温度。在氧气或水的存在下，K2SO4 没有观察到去流化。然而，K2SO4 分解并与 SiO2 反应形成 K-硅酸盐，在 850 °C 的含 H2 气体中引起脱流化。在空气中，含 H2– 或 H2O 的气体中，K2CO3 会与 SiO2 反应生成硅酸钾，并且在含 H2– 和 H2O 的气体中可能会另外生成 KOH。