Trickle flow hydrodynamic multiplicity: Experimental observations and pore-scale capillary mechanism

Merwe, Willem van der; Nicol, Willie

doi:10.1016/j.ces.2008.10.069

Cited by 12 publications

(7 citation statements)

References 47 publications

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“…Moreover, direct studies of the effect of multiplicity on reactor performance are scarce 26. In this investigation, two of the prewetting methods as summarized by van der Merwe and Nicol27 are used to explore the boundaries of multiplicity behavior.…”

Section: Introductionmentioning

confidence: 99%

Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

Houwelingen

Nicol

2011

AIChE Journal

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A novel method for the measurement of wetting efficiency in a trickle-bed reactor under reaction conditions is introduced. The method exploits reaction rate differences of two first-order liquid-limited reactions occurring in parallel, to infer wetting efficiencies without any other knowledge of the reaction kinetics or external mass transfer characteristics. Using the hydrogenation of linear-and isooctenes, wetting efficiency is measured in a 50-mm internal diameter, high-pressure trickle-bed reactor. Liquidsolid mass transfer coefficients are also estimated from the experimental conversion data. Measurements were performed for upflow operation and two literature-defined boundaries of hydrodynamic multiplicity in trickle flow. Hydrodynamic multiplicity in trickle flow gave rise to as much as 10% variation in wetting efficiency, and 10-20% variation in the specific liquid-solid mass transfer coefficient. Conversions for upflow operation were significantly higher in trickle-flow operation, because of complete wetting and better liquid-solid mass transfer characteristics.

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Section: Introductionmentioning

confidence: 99%

Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

Houwelingen

Nicol

2011

AIChE Journal

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“…For liquid superficial velocities between 1 to 10 mm/s and a gas superficial velocity of the order of 100 mm/s, the pressure drop per unit of reactor length is in the range of 1−20 kPa/m and the pressure drop in the two branches can differ by a factor of 2 for the same gas and liquid velocities. The hysteresis effect increases as the particle size decreases for a particle diameter ( d p ) range between 0.5 and 8 mm. , In fact, the hysteresis phenomenon is only observed in the trickling flow regime and will disappear when particles are fully wetted by a change in flow pattern, e.g. by short-lived full wetting in a pulsing flow regime.…”

Section: Introductionmentioning

confidence: 99%

Transient Behavior and Stability in Miniaturized Multiphase Packed Bed Reactors

Márquez

Castaño

Moulijn

et al. 2010

Ind. Eng. Chem. Res.

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The step response, including various startup procedures, in a three-phase microreactor of 2 mm internal diameter packed with nonporous particles of 100 μm is reported. We demonstrate that the bed behaves reproducibly through many cycles of operating conditions. Interestingly, we find that the different startup procedures have little effect on the steady state that is achieved. In other words, minimal hysteresis was observed, in sharp contrast to larger-scale reactors with larger particles where prewetting has a remarkable impact on the hydrodynamic behavior. The powder-packed beds have very high liquid saturation values, and prewetting is not needed. At least four liquid-residence times were needed to achieve stable pressure drop and dispersion values over the bed. This indicates that the hydrodynamic response into a stable operation may well be the limiting factor that determines the rate at which kinetic experiments can be performed in high-throughput equipment.

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“…Although the existence of multiplicity had been established as early as 1978, in-depth investigation of the causes and application possibilities of this phenomenon is relatively new to TBR literature. The ongoing development of nonintrusive visualization techniques has led to improved images of trickle flow structures. − In a recent study by Van der Merwe and Nicol, high definition X-ray tomography results were used to analyze the flow structure differences between various hydrodynamic multiplicity modes. The study highlighted the importance of capillary effects in pore necks (small channels between larger pore openings) and proposed a mechanism where capillary blocking (or the absence thereof) in pore necks was used to account for multiplicity.…”

Section: Introductionmentioning

confidence: 99%

Multiplicity Behavior of Trickle Flow Liquid−Solid Mass Transfer

Joubert

Nicol

2009

Ind. Eng. Chem. Res.

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Dissolution as well as electrochemical techniques confirmed the existence of multiplicity. The commonly accepted upper multiplicity branch (achieved by Kan liquid prewetting) outperformed the lower branch (achieved by Levec prewetting) by as much as 1.6 times in Sherwood numbers. Although similar trends were observed for the two measurement techniques, the dissolution measurements were significantly lower than the electrochemical measurements. It was further shown that the multiplicity behavior of liquid-solid mass transfer is not linked solely to liquid hold-up and wetting efficiency variations, indicating major differences in flow structures between the multiplicity modes employed. In addition, a decrease in Sherwood numbers with bed depth was observed for both multiplicity modes.

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Trickle flow hydrodynamic multiplicity: Experimental observations and pore-scale capillary mechanism

Cited by 12 publications

References 47 publications

Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

Transient Behavior and Stability in Miniaturized Multiphase Packed Bed Reactors

Multiplicity Behavior of Trickle Flow Liquid−Solid Mass Transfer

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