Liquid–solid mass transfer distributions in trickle bed reactors

Nicol, Willie; Joubert, Rita

doi:10.1016/j.cej.2013.06.111

Cited by 8 publications

(3 citation statements)

References 21 publications

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“…For the Levec prewetted bed the decline in φ k ls is a consequence of both a decrease in wetting efficiency combined with a reduction in the “quality” of flow where there is contact between the solid and the liquid. This supports the conclusions of Nicol and Joubert, which confirmed the two-wetted zone theory in trickle bed reactors and showed that more static liquid zones, where the rate of surface renewal processes is slow, exist in a Levec prewetted bed. In the Kan prewetted bed the decrease in the solid wetted fraction is the main contributing factor for an axial decline in φ k ls .…”

Section: Resultssupporting

confidence: 90%

Axial Variation of Wetting Efficiency and Liquid–Solid Mass Transfer in Long Trickle Bed Columns

Toit

Joubert

Saayman

et al. 2013

Ind. Eng. Chem. Res.

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The wetting efficiency and solid liquid mass transfer coefficient was measured separately and simultaneously using the electrochemical cell technique while varying the superficial liquid velocity and hydrodynamic state of the column by using different pre-wetting procedures.The wetting efficiency in columns with an aspect ratio -distance from distributor divided by column diameter -of up to 33, decreased with distance from the distributor regardless of the hydrodynamic state of the column. Although the solid liquid mass transfer coefficient also decreased with an increase in axial position, this decrease was much more significant where the pre-wetting procedure that resulted in a lower overall wetting efficiency was used. When a pre-wetting procedure that resulted in a higher average wetting efficiency was used, the liquid solid mass transfer coefficient was much less dependent on liquid velocity and only a relatively small decrease with axial position was observed. The results highlight the difference in surface renewal processes that is possible between columns operated at the same conditions but under different hydrodynamic states and emphasise the importance of hydrodynamic multiplicity when liquid redistribution is considered.

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Section: Resultssupporting

confidence: 90%

Axial Variation of Wetting Efficiency and Liquid–Solid Mass Transfer in Long Trickle Bed Columns

Toit

Joubert

Saayman

et al. 2013

Ind. Eng. Chem. Res.

Self Cite

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“…Single‐ and two‐phase flow experiments were conducted in a horizontal square‐shaped spherical‐particle string reactor with a channel size of 4 mm × 4 mm and particle diameters from 2 to 4 mm, with mean hydraulic channel diameter‐to‐particle diameter ratios of 1.1–1.7. The electrochemical method has also been employed to measure the local instantaneous liquid‐solid mass transfer coefficient at a certain position within the bed 16, 26–34. Other methods including chemical reacting systems 12, 35–39, activated carbon absorption 40, and ion exchange of Na + from aqueous solutions of NaOH 41 have also been used for the determination of liquid‐solid mass transfer coefficients.…”

Section: Introductionmentioning

confidence: 99%

Liquid‐to‐Particle Mass Transfer in a Structured‐Bed Minireactor

Templis

Papayannakos

2016

Chem Eng & Technol

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Liquid-to-particle mass transfer effects in a string pellet minireactor were studied by applying the diffusion-controlled copper dissolution technique. Structured beds were formed with cylindrical particles in spiral and vertical configurations and operated with liquid and gas-liquid feeds in upflow mode. Single-and two-phase flow experiments were conducted to study the effects of the gas and the liquid superficial velocities on the liquid-to-particle mass transfer coefficient. Computational fluid dynamics calculations were performed to study the effect of the arrangement of the particles in the reactor tube on the liquid-to-particle effective mass transfer coefficient for the single-phase flow. Correlations of the mass transfer coefficient with the operating conditions were derived.

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“…Another important factor is the prewetting procedure, 10–12 while non‐prewetted catalyst beds performed poor radial dispersion, prewetted beds showed improved liquid distribution and wetting efficiency. Multiplicity of hydrodynamic states have been reported in the increasing and decreasing modes of operation of TBR and up to 100% difference in pressure drop and up to 30% in liquid holdup have been reported 11,13,14 .…”

Section: Introductionmentioning

confidence: 99%

Bed structure and its impact on liquid distribution in a trickle bed reactor

2022

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Trickle bed reactors, which has been a workhorse for the process and refining industry for many decades, are progressively being challenged to provide solutions to deep processing of feedstocks. It is known that the structure of the packed bed which is formed with a certain arrangement of catalyst particles in the three‐dimensional space within the reactor modulates in an unknown fashion the flow of fluids in the trickle bed, and in turn affects the conversion and selectivity in the trickle bed. Under deep processing conditions, the impact of the bed structure in modulating the overall reactor performance in a trickle bed is not as yet established. The question begets three sequential studies: estimating and quantifying the bed structure, measuring the liquid distribution, and estimating transport parameters (that are dependent on the bed structure and liquid distribution) so that the overall performance metrics as a reactor may be quantified. This contribution relates to the second of these questions, the first being already addressed to some extent by our earlier work. The current investigation aims at quantifying the effect of structure of the packed bed on hydrodynamics of the reactor. The impact of various packing techniques is discussed along with the development of correlations for two‐phase pressure drop and dynamic liquid holdup. Liquid distribution is studied in depth for various operating parameters such as gas and liquid superficial velocities and column aspect ratio for uniform and non‐uniform packing methods. The packing devices consist of various inserts attached to a hopper which can generate packing structures having void fraction in the range of 37.2%–46.4%. The maldistribution factor and flow maps for various aspect ratio of column suggest that maldistribution rises along with the increased channeling effect along the height of the column. Uniformly packed bed were measurably less prone to maldistribution along the length than the non‐uniformly packed beds.

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Liquid–solid mass transfer distributions in trickle bed reactors

Cited by 8 publications

References 21 publications

Axial Variation of Wetting Efficiency and Liquid–Solid Mass Transfer in Long Trickle Bed Columns

Axial Variation of Wetting Efficiency and Liquid–Solid Mass Transfer in Long Trickle Bed Columns

Liquid‐to‐Particle Mass Transfer in a Structured‐Bed Minireactor

Bed structure and its impact on liquid distribution in a trickle bed reactor

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