Bubbles rising through fluidized beds at velocities several times superficial velocities contribute to solids backmixing. In micro-fluidized beds, the walls constrain bubble sizes and velocities. To evaluate gas-phase hydrodynamics and identify diffusional contributions to longitudinal dispersion, we injected a mixture of H₂, CH₄, CO, and CO₂ (syngas) as a bolus into a fluidized bed of porous fluid catalytic cracking catalyst while a mass-spectrometer monitored the effluent gas concentrations at 2 Hz. The CH₄, CO, and CO₂ trailing RTD traces were elongated versus H₂ demonstrating a chromatographic effect. An axial dispersion model accounted for 92% of the variance but including diffusional resistance between the bulk gas and catalyst pores and adsorption explained 98.6% of the variability. At 300°C, the CO₂ tailing disappeared consistent with expectations in chromatography (no adsorption). H₂ and He are poor gas-phase tracers at ambient temperature. We recommend measuring RTD at operating conditions.

中文翻译：

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合成气中 CO2 的流化床流体动力学模型：由于 FCC 吸附导致 RTD 曲线失真

以数倍于表观速度的速度通过流化床上升的气泡导致固体返混。在微流化床中，壁限制了气泡的大小和速度。为了评估气相流体动力学并确定对纵向分散的扩散贡献，我们将 H ₂、CH ₄、CO 和 CO ₂（合成气）的混合物作为丸剂注入多孔流化催化裂化催化剂的流化床中，同时大量光谱仪以 2 Hz 的频率监测废气浓度。CH ₄、CO 和 CO ₂拖尾 RTD 迹线相对于 H ₂被拉长显示色谱效应。轴向扩散模型解释了 92% 的变异，但包括主体气体和催化剂孔之间的扩散阻力，吸附解释了 98.6% 的变异。在 300°C 时，CO ₂拖尾消失，与色谱中的预期一致（无吸附）。H ₂和He 在环境温度下是较差的气相示踪剂。我们建议在工作条件下测量 RTD。