Liquid−Solid Mass Transfer in Agitated Slurry Reactors and Rotating Solid Foam Reactors

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• 作者：R. Tschentscher ; R. J. P. Spijkers ; T. A. Nijhuis ; J. van der Schaaf ; J. C. Schouten
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2010
• 出版时间：November 3, 2010
• 年：2010
• 卷：49
• 期：21
• 页码：10758-10766
• 全文大小：326K
• 年卷期：v.49,no.21(November 3, 2010)
• ISSN：1520-5045

文摘

The liquid−solid mass transfer rate is studied for two three-phase reactor configurations, a stirred reactor and a rotating solid foam reactor, using the dissolution of copper by potassium dichromate as a model reaction. For the stirred reactor consisting of a Rushton stirrer and a slurry with small particles, the particle density has a large influence on the liquid−solid mass transfer rate. Heavy particles show high slip velocities, as their path is less influenced by the liquid turbulence. Furthermore, the mass transfer is enhanced by neighboring particles passing each other. In the case of solid copper particles, a k_LS value of 3 × 10⁻³ ms⁻¹ was observed. For particles having a density comparable to industrial catalyst supports, the k_LS value is 1 order of magnitude lower. For the rotating foam block stirrer also, high k_LS values of 2.5 × 10⁻³ ms⁻¹ could be achieved due to the high liquid velocity along the foam struts. The influence of several parameters on the hydrodynamics and the liquid−solid mass transfer was studied. Among these, the foam block height, the foam pore size, and the space above the foam block stirrer have a large effect on the liquid circulation, the bubble formation, and therefore on the liquid−solid mass transfer. The reduction of the foam pore size has two counterbalancing effects, resulting only in a slight increase of the rate of mass transfer: (i) the liquid−solid interfacial area is increased; (ii) the liquid circulation is, however, reduced due to the higher frictional pressure drop. Gas bubbles passing the foam struts affect the liquid−solid mass transfer by inducing liquid velocity fluctuations. For the foam block stirrer, a maximum k_LSa_LS value of 0.6 s⁻¹ was obtained. This shows great potential for further optimization of the liquid flow and therefore the mass transfer. An additional advantage of the foam stirrer reactor is that the solid phase is fixed and the catalyst does not need to be separated downstream from the reactor.