Hysteresis in Trickle-Bed Reactors: A Review

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• 作者：Rabindranath Maiti ; Rajesh Khanna ; and K. D. P. Nigam
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2006
• 出版时间：July 19, 2006
• 年：2006
• 卷：45
• 期：15
• 页码：5185 - 5198
• 全文大小：710K
• 年卷期：v.45,no.15(July 19, 2006)
• ISSN：1520-5045

文摘

A concise review of the hysteresis in cocurrent down-flow trickle-bed reactors (TBRs) is presented. Theeffects of several factors on the hysteresis, such as the type of particles (porous/nonporous), the size of theparticles, the operating flow ranges, and the start-up conditions (wet/dry) are described. Also, some limitedinformation that is available about the effects of other factors, such as addition of wetting agents (surfactants)and inlet liquid distribution, are also discussed. Empirical and theoretical models developed to predict hysteresisare briefly described. Most of the studies have reported an appreciable amount of hysteresis in keyhydrodynamic parameters such as pressure drop, liquid holdup, and wetting efficiency, especially with smallpacking material (~1.6-3.5 mm). The hysteresis is attributed to the different degrees of wetting, whichoccurs because of the flowing of liquid in two different modes, such as film and rivulet. The hysteresisbehavior of a packed bed with porous particles is observed to be significantly different than that of nonporousparticles. These differences are linked to the dual nature of pores, i.e., the pores act both as an acceleratorand brakes on the spreading drop edge over the porous surface. This pore-level concept is further enhancedby the concept of participating and nonparticipating particles to understand the different hysteretic behaviorof TBRs. Few mathematical modeling efforts have been attempted to capture the trend that is observed inhysteresis behavior with nonporous particles only. Recently, an attempt has been made to understand thecomprehensive hysteretic behavior of both porous and nonporous particles with the conceptual framework ofhysteresis. The present review focuses the attention to enhance the further understanding of the physics ofthe flow of fluids through TBRs, which may be responsible for the phenomena of hysteresis, especially inporous particles.