Numerical Investigation of Catalyst Structure for Steam Reforming Process

Arslan, Muhammad (2021) Numerical Investigation of Catalyst Structure for Steam Reforming Process. Doctoral thesis, Birmingham City University.

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Text Muhammad Abdullah Arslan PhD Thesis published_Final version_Submitted Jul 2021_Final Award Oct 2021.pdf - Accepted Version Download (7MB)

Abstract

Internal combustion engines substantially lose fuel energy in the form of heat without contributing to the vehicle’s propulsion. About a third of this waste energy gets released from the exhaust pipeline. Catalysts recover this unused heat for their essential function to curb emissions; however, a fuel reformer catalyst can take it further. An onboard fuel reformer makes hydrogen and carbon monoxide, known as syngas. The syngas and primary fuel increases fuel heating value and modify combustion characteristics towards low emissions.

This study numerically investigates catalyst design impacts on its efficiency. The primary goal of this research is to achieve a higher hydrogen yield without altering the catalyst dimensions. Structural changes such as cell height, catalyst segmentation, and passive passages remarkably affect catalyst efficiency. Meanwhile, key catalyst characteristics such as flow uniformity, pressure drop, light-off, and residence time remain under consideration during these variations.

For this purpose, after verifying the simulation against an experimental study, a successful channel height reduction is achieved by employing metal foam as a support structure (protrusion). Usually, the catalyst cell wall contains a reacting material layer. Putting this layer on the protrusion and elevating it to the middle of the cell height increases the hydrogen mass fraction (H2 mf) by more than fifty per cent. The nearby fluid temperature for this pattern is 60 K higher than the conventional design, which is the primary reason for the higher yield. This modification also enables channel height variation without changing the cell height or shape.

The channel is then divided into inert and catalytic portions. This segmentation allows the reactants to regain heat after passing over these inactive isothermal parts. Thus, fluid mixing and higher temperature increase the reaction rate before reactants reach the next catalyst section. The length of these patterns is carefully kept equal to the reference design. As a result of these modifications, the hydrogen mf increases 11% further.

Transverse flow channels permit inter-channel heat and mass transfer. The location and number of these passive passages need further investigation. Metal foam existence at these paths can direct fluid flow by varying the foam properties. Directional porosity and permeability mainly affect the flow pattern. In addition, metal foam presence at these perforations enhances the neighbouring gas temperature by 20 K and the hydrogen production by 15%.

Overall, numerical calculations show that compared to the conventional structure, cell height and segmentation can increase H2 mf by 50-80%, whereas passive passages increase it by 15%.

Item Type:	Thesis (Doctoral)
Dates:	Date Event 16 July 2021 Accepted 25 October 2021 Submitted
Uncontrolled Keywords:	Numerical analysis, Fuel cell, Metal foam, Segmentation, Passive flow, Catalyst, Structure variation, Heat recovery
Subjects:	CAH10 - engineering and technology > CAH10-01 - engineering > CAH10-01-01 - engineering (non-specific)
Divisions:	Doctoral Research College > Doctoral Theses Collection Faculty of Computing, Engineering and the Built Environment
Depositing User:	Jaycie Carter
Date Deposited:	03 Oct 2022 13:25
Last Modified:	03 Oct 2022 13:25
URI:	https://www.open-access.bcu.ac.uk/id/eprint/13637

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