Gas—solids contact efficiency in a high-velocity fluidised bed
Gas—solids contact efficiency in a high-velocity fluidised bed
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DOI：
10.1016/0032-5910(87)80111-0
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发表时间：
1987-10
影响因子：
5.2
通讯作者：
R. Dry;I. Christensen;C. White
中科院分区：
文献类型：
--
作者：
R. Dry;I. Christensen;C. White
测定了FCC催化剂高速流化床内气固接触效率。该技术涉及使用加热气体作为反应示踪剂，并通过快速响应热电偶检测这种热气体。所得到的测量结果表明有多少气体在床的出口处出现而没有与任何固体颗粒接触。这类信息可能对商业高速系统的设计和操作具有重要意义。实验装置，气体速度范围为2至8 m/s，固体循环速率高达200 kg m-2s-1。对于超过100 kg m-2s-1的固体速率，气固接触在2 m/s时几乎完全，但随着气速的增加而稳定地降低。在8 m/s时，即使在接近200 kg m−2s− 1的固体速率下，接触效率也明显低于100%。使用一个简单的模型来估计床中有效颗粒表面积与实际颗粒表面积的比率，这定义了表面效率，发现其范围为0.01至0.13%。有人建议，这可能与在任何时刻作为个体自由移动的颗粒的比例有关，而不是构成松散团聚体的颗粒，如飘带或致密壁区。
The efficiency of contact between gas and solid phases in a high-velocity fluidised bed of FCC catalyst has been measured. The technique involves the use of heated gas as a reacting tracer and detection of this hot gas by a rapid-response thermocouple. The resulting measurement indicates how much gas emerges at the outlet from the bed without having come into contact with any solid particles. This type of information could have significant implications for the design and operation of commercial high-velocity systems.Contact efficiencies are presented for a 0.09-m I.D. experimental rig, with gas velocities in the range 2 to 8 m/s and solids circulation rates of up to 200 kg m−2s−1. Gas—solids contact appears to be almost complete at 2 m/s for a solids rate exceeding 100 kg m−2s−1, but decreases steadily as gas velocity is increased. At 8 m/s, it appears that contact efficiencies are significantly less than 100%, even at solids rates approaching 200 kg m−2s−1.A simple model is used to estimate the ratio of effective to actual particle surface area in the bed, and this defines a surface efficiency which is found to lie in the range 0.01 to 0.13%. It is suggested that this could be related to the proportion of particles which are free to move as individuals at any instant, as opposed to particles which make up loose agglomerates such as streamers or dense wall regions.