Effect of foam stirrer design on the catalytic performance of rotating foam stirrer reactors
Effect of foam stirrer design on the catalytic performance of rotating foam stirrer reactors
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DOI：
10.1016/j.cej.2012.06.053
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发表时间：
2012-10
影响因子：
15.1
通讯作者：
M. A. León;P. Geers;T. A. Nijhuis;J. Schaaf;J. J. Schouten-J.
中科院分区：
文献类型：
--
作者：
M. A. León;P. Geers;T. A. Nijhuis;J. Schaaf;J. J. Schouten-J.
以苯乙烯加氢为模型反应，研究了旋转泡沫搅拌反应器和浆态床反应器中的液固传质速率。旋转泡沫搅拌反应器是一种新型的多相反应器，其中高度开孔的材料，固体泡沫，被用作催化剂载体和搅拌器。泡沫搅拌器的设计对液固传质速率有很大的影响。使用环形泡沫块配置，液固传质系数kLS比叶片配置低五倍。通过泡沫块结构的减少的液体循环由更高的摩擦压降解释。孔雷诺数表明，泡沫块搅拌器的流动是在层流状态，而叶片搅拌器是湍流。kLS的局部测量值表明沿着泡沫块结构的高度沿着的质量传递曲线，允许泡沫块内催化剂位置的相关选择和/或建议改变泡沫块设计以避免底部效应，例如，使用圆锥形泡沫块形状。然而，泡沫块搅拌器提供比叶片搅拌器更高的液-固界面面积，导致更高的kLSaLS。在1000 W/mL ~ 3以上的功率输入下，使用顶部具有催化活性的20 μ m泡沫块，反应速率不受液-固传质限制。与Rushton搅拌器相比，由于高的液-固界面面积和催化剂表面的快速更新，液-固传质速率得到增强。kLSaLS值为0.5s-1，而浆料系统为0.04s-1。使用少62%的催化剂实现了与淤浆反应器中相同的生产速率。由于催化剂固定在搅拌器上，旋转泡沫搅拌器反应器的另一个优点是不存在催化剂分离步骤。催化剂不发生失活和团聚，泡沫催化剂可重复使用。
The liquid–solid mass transfer rate in a rotating foam stirrer reactor and in a slurry reactor is studied using the hydrogenation of styrene as a model reaction. The rotating foam stirrer reactor is a novel type of multi-phase reactor where highly open-celled materials, solid foams, are used as a catalyst support and as a stirrer. The design of the foam stirrer has a strong influence on the liquid–solid mass transfer rate. Using a donut-shaped foam block configuration, the liquid solid mass transfer coefficient, kLS, is five times lower than in a blade configuration. The reduced liquid circulation through the foam block structure is explained by a higher frictional pressure drop. The pore Reynolds number indicates that the flow is in the laminar regime for the foam block stirrer while it is turbulent for the blade stirrer. Local measurements of kLSindicate a mass transfer profile along the height of the foam block structure, allowing a pertinent choice of the catalyst location within the foam block and/or suggesting changes of the foam block design to avoid the bottom effects, for instance, using a conical foam block shape. However, the foam block stirrer offers higher liquid–solid interfacial area than a blade stirrer, resulting in higher kLSaLS. At a power input above 1000W/mL3and using a 20ppi foam block with the top part catalytically active, the reaction rate is not liquid–solid mass transfer limited. Compared to a Rushton stirrer, the liquid–solid mass transfer rate is enhanced because of a high liquid–solid interfacial area and a fast refreshment of the catalyst surface. kLSaLSvalues of 0.5s−1are obtained compared to 0.04s−1for the slurry system. The same production rate as in the slurry reactor is achieved using 62% less catalyst. As the catalyst is immobilized on the stirrer, an additional advantage of the rotating foam stirrer reactor is the absence of a catalyst separation step. Attrition and agglomeration of the catalyst do not occur and the foam catalyst can be reused.