Enhanced Mass Transfer in Monolith Catalysts with Bumps on the Channel Walls

Holmgren, Anna

doi:10.1021/ie980597f

Cited by 16 publications

(15 citation statements)

References 31 publications

(74 reference statements)

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“…A predominant method to quantify mass transfer found in the literature 1,11,12,14,15,[18][19][20][21] is the use of the Sherwood number, N SH . The Sherwood number is defined as:…”

Section: Sherwood Numbermentioning

confidence: 99%

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Monolithic Supports with Unique Geometries and Enhanced Mass Transfer

Stuecker

Ferrizz

Cesarano

et al. 2004

Ind. Eng. Chem. Res.

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The catalytic combustion of natural gas has been the topic of much research over the past decade. Interest in this technology results from a desire to decrease or eliminate the emissions of harmful nitrogen oxides (NO X ) from gas turbine power plants. A low-pressure drop catalyst support, such as a ceramic monolith, is ideal for this high-temperature, high-flow application. A drawback to the traditional honeycomb monoliths under these operating conditions is poor mass transfer to the catalyst surface in the straight-through channels. "Robocasting" is a unique process developed at Sandia National Laboratories that can be used to manufacture ceramic monoliths with alternative 3-dimensional geometries, providing tortuous pathways to increase mass transfer while maintaining low pressure drops.This report details the mass transfer effects for novel 3-dimensional robocast monoliths, traditional honeycomb-type monoliths, and ceramic foams. The mass transfer limit is experimentally determined using the probe reaction of CO oxidation over a Pt / γ-Al 2 O 3 catalyst, and the pressure drop is measured for each monolith sample. Conversion versus temperature data is analyzed quantitatively using well-known dimensionless mass transfer parameters. The results show that, relative to the honeycomb monolith support, considerable improvement in mass transfer efficiency is observed for robocast samples synthesized using an FCC-like geometry of alternating rods. Also, there is clearly a trade-off between enhanced mass transfer and increased pressure drop, which can be optimized depending on the particular demands of a given application.4

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“…A predominant method to quantify mass transfer found in the literature 1,11,12,14,15,[18][19][20][21] is the use of the Sherwood number, N SH . The Sherwood number is defined as:…”

Section: Sherwood Numbermentioning

confidence: 99%

“…However, for ceramic foams and the robocast samples in this study, the channel diameter (or average pore size) is somewhat an abstract quantity. A common expression 6,15,21,25 for determining d H for unusual geometries is the following:…”

Section: Sherwood Numbermentioning

confidence: 99%

Monolithic Supports with Unique Geometries and Enhanced Mass Transfer

Stuecker

Ferrizz

Cesarano

et al. 2004

Ind. Eng. Chem. Res.

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show abstract

Section: Sherwood Numbermentioning

confidence: 99%

Monolithic supports with unique geometries and enhanced mass transfer.

Stuecker

Ferrizz

Cesarano

et al. 2004

View full text Add to dashboard Cite

The catalytic combustion of natural gas has been the topic of much research over the past decade. Interest in this technology results from a desire to decrease or eliminate the emissions of harmful nitrogen oxides (NO X) from gas turbine power plants. A low-pressure drop catalyst support, such as a ceramic monolith, is ideal for this high-temperature, high-flow application. A drawback to the traditional honeycomb monoliths under these operating conditions is poor mass transfer to the catalyst surface in the straight-through channels. "Robocasting" is a unique process developed at Sandia National Laboratories that can be used to manufacture ceramic monoliths with alternative 3-dimensional geometries, providing tortuous pathways to increase mass transfer while maintaining low pressure drops. This report details the mass transfer effects for novel 3-dimensional robocast monoliths, traditional honeycomb-type monoliths, and ceramic foams. The mass transfer limit is experimentally determined using the probe reaction of CO oxidation over a Pt / γ-Al 2 O 3 catalyst, and the pressure drop is measured for each monolith sample. Conversion versus temperature data is analyzed quantitatively using well-known dimensionless mass transfer parameters. The results show that, relative to the honeycomb monolith support, considerable improvement in mass transfer efficiency is observed for robocast samples synthesized using an FCC-like geometry of alternating rods. Also, there is clearly a trade-off between enhanced mass transfer and increased pressure drop, which can be optimized depending on the particular demands of a given application.

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“…The gas flow through the catalyst channel is normally laminar (the Reynolds number is smaller than 2000 and the critical Reynolds number is 2300 ), but it has been proven that, by using protrusions on the walls of channel, the critical Reynolds number decreases to 700 . Holmgren and Hass and Rice noticed that using protrusions enhances the mass transfer phenomenon. These protrusions disturb the boundary layer, generate vortex and intensify turbulence in the channel .…”

Section: Introductionmentioning

confidence: 99%

“…However, based on the literature for the case of a turbulent monolith structure, the Nusselt and Sherwood numbers can be estimated to be between one to ten times of the laminar flow condition. According to Holmgren , the use of turbulent monolith structure causes pressure loss in the channel, but in the case of a channel with bumps (turbulent flow), the value of Chilton–Colburn mass transfer factor to the Fanning friction factor

\frac{j_{normalD}}{(f / 2)}

is higher than channel without bumps. This means that the effect of mass transfer dominates over the pressure loss.…”

Section: Introductionmentioning

confidence: 99%

Finding optimum range for increasing the transport coefficients in a three-way catalytic converter in order to achieve minimum light-off time and maximum increase in efficiency using multiobjective genetic algorithm

Daryan

Shamekhi

2014

Environ. Prog. Sustainable Energy

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In this article, an optimum range for increasing transport coefficients with respect to the laminar flow condition in the channel of a three‐way catalyst is introduced. A mathematical model of a three‐way catalyst was first developed. The model is a one‐dimensional plug flow model which involves mass and energy equations in gas and solid phases. To save numerical time, the three‐way catalyst model was replaced with a neural network model used in optimization which was solved by using a multi‐objective genetic algorithm method. The results of optimization introduce a range in which the desirable objectives will be satisfied. The objectives are to achieve minimum light‐off time and maximum increase in catalyst efficiency during different operating conditions of engine. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 368–379, 2015

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Enhanced Mass Transfer in Monolith Catalysts with Bumps on the Channel Walls

Cited by 16 publications

References 31 publications

Monolithic Supports with Unique Geometries and Enhanced Mass Transfer

Monolithic Supports with Unique Geometries and Enhanced Mass Transfer

Monolithic supports with unique geometries and enhanced mass transfer.

Finding optimum range for increasing the transport coefficients in a three-way catalytic converter in order to achieve minimum light-off time and maximum increase in efficiency using multiobjective genetic algorithm

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