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Combustion characterisation of compositionally dynamic steelworks gases

Pugh, Daniel 2013. Combustion characterisation of compositionally dynamic steelworks gases. PhD Thesis, Cardiff University.
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Abstract

This thesis investigates the combustion of fuel compositions representative of those produced by the integrated steelmaking process. As organisations strive for improvements in utilisation efficiency with increasingly complex technologies, more detailed understanding is required to accurately simulate combustion of the potentially weak and dilute fuels, and thereby aid design processes. Dynamic fuel properties have been characterised through experimentation, in addition to a comparison of numerically simulated results obtained from chemical kinetics. The parameters identified to investigate fuel behaviour were laminar burning velocity and Markstein Length, and characterised with regard to operational instability in practical combustion systems. The design and construction of a suitable experimental rig is detailed, as required to facilitate the accurate determination of burning velocities by quantifying the outward propagation of spherical flames. A regressive analytical technique was developed based on previous studies, nonlinearly relating propagation to change in stretch rate. The developed solution was benchmarked against analogous studies in literature, and ensured experimental performance was accurate and repeatable for the well documented combustion of methane. Steelworks gases were tested to attain representative burning velocities, with significant attention paid to the change resulting from fluctuation in blast furnace gas H2 fraction. The study characterised the observed sensitivity to change in flame speed and discussed the implications with regard to practical combustion systems. Several methods of reducing the measured fluctuation are subsequently quantified, including change in ambient condition, and relative humidity. Non-monotonic behaviour was observed for the latter effect, with a suggested trade-off between a chemically catalytic influence on intermediate species, and lowering of flame temperature. Consequently this suggested water addition could be an effective mechanism for the reduction of H2 induced flame speed variation for blast furnace gas, and influence other synthesised fuels comprising large quantities of CO, including BOS gas. Additional steelworks gases were blended in different ratios to assess dynamic combustive properties relating to fuel flexibility, and the effectiveness of minimising fluctuation in combustion behaviour.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords: Laminar flame speed; Flame stretch; Marhstein length; Blast furnance gas; Coke oven gas; Steelworks gases.
Funders: EPSRC
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 06:16
URI: http://orca.cf.ac.uk/id/eprint/58006

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