Abstract In this work, an investigation on the fluidization behaviour of solid particles was carried out while the fluidizing agent was switched from one gas to another with an equal volumetric flow. Four different gases, namely helium, nitrogen, argon and carbon dioxide (He, N2, Ar and CO2), were adopted as fluidizing agents, and fluid catalytic cracking (FCC) was used as the experimental material. When changing the gas supply a sharp decrease of the bed pressure drop and significant compression of the emulsion phase are observed, as well as the disappearing of the bubbles and the formation of channels inside the bed. However, these disturbances are temporary, and the initial fluidization conditions can be restored after a certain amount of time. Such behaviour is quantitatively described by measuring the maximum relative decrease of bed pressure drop, the time duration and the intensity of the defluidization phase. The effects of the initial powder bed height, the switching gas velocity and the gas properties are analyzed as well. Finally, a semi-empirical model was developed to predict the defluidization time based on the understanding of this physical process and analyzing the experimental data.

中文翻译：

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换气流化过程中脱流化行为及其影响因素的实验研究

摘要 在这项工作中，研究了流化剂从一种气体切换到另一种具有相等体积流量时固体颗粒的流化行为。采用氦气、氮气、氩气和二氧化碳（He、N2、Ar和CO2）四种不同气体作为流化剂，流化催化裂化（FCC）作为实验材料。当改变气体供应时，观察到床压降急剧下降和乳液相的显着压缩，以及气泡消失和床内通道的形成。然而，这些扰动是暂时的，经过一定的时间后可以恢复初始流化条件。这种行为通过测量床压降的最大相对降低、持续时间和去流化阶段的强度来定量描述。还分析了初始粉末床高度、切换气体速度和气体性质的影响。最后，在了解这一物理过程并分析实验数据的基础上，建立了半经验模型来预测脱流时间。