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Catalytic influence of water vapor on lean blowoff and NOx reduction for pressurised swirling syngas flames

Pugh, Daniel, Bowen, Philip, Crayford, Andrew, Marsh, Richard, Runyon, Jon, Morris, Steven and Giles, Anthony 2018. Catalytic influence of water vapor on lean blowoff and NOx reduction for pressurised swirling syngas flames. Journal of Engineering for Gas Turbines and Power 140 (6) , 061502. 10.1115/1.4038417

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Abstract

It has become increasingly cost-effective for the steel industry to invest in the capture of heavily carbonaceous BOF (Basic Oxygen Furnace) or converter gas, and use it to support the intensive energy demands of the integrated facility, or for surplus energy conversion in power plants. As industry strives for greater efficiency via ever more complex technologies, increased attention is being paid to investigate the complex behavior of by-product syngases. Recent studies have described and evidenced the enhancement of fundamental combustion parameters such as laminar flame speed due to the catalytic influence of H2O on heavily carbonaceous syngas mixtures. Direct formation of CO2 from CO is slow due to its high activation energy, and the presence of disassociated radical hydrogen facilitates chain branching species (such as OH), changing the dominant path for oxidation. The observed catalytic effect is non-monotonic, with the reduction in flame temperature eventually prevailing, and overall reaction rate quenched. The potential benefits of changes in water loading are explored in terms of delayed lean blowoff, and primary emission reduction in a premixed turbulent swirling flame, scaled for practical relevance at conditions of elevated temperature (423 K) and pressure (0.1-0.3 MPa). Chemical kinetic models are used initially to characterize the influence that H2O has on the burning characteristics of the fuel blend employed, modelling laminar flame speed and extinction strain rate across an experimental range with H2O vapor fraction increased to eventually diminish the catalytic effect. These modelled predictions are used as a foundation to investigate the experimental flame. OH* chemiluminescence and OH planar laser induced fluorescence (PLIF) are employed as optical diagnostic techniques to analyze changes in heat release structure resulting from the experimental variation in water loading. A comparison is made with a CH4/air flame and changes in lean blow off stability limits are quantified, measuring the incremental increase in air flow and again compared against chemical models. The compound benefit of CO and NOx reduction is quantified also, with production first decreasing due to the thermal effect of H2O addition from a reduction in flame temperature, coupled with the potential for further reduction from the change in lean stability limit. Power law correlations have been derived for change in pressure, and equivalent water loading. Hence, the catalytic effect of H2O on reaction pathways and reaction rate predicted and observed for laminar flames, are compared against the challenging environment of turbulent, swirl-stabilized flames at elevated temperature and pressure, characteristic of piratical systems.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Engineering
Publisher: American Society of Mechanical Engineers (ASME)
ISSN: 0742-4795
Date of First Compliant Deposit: 14 August 2017
Date of Acceptance: 28 July 2017
Last Modified: 12 Nov 2019 23:26
URI: http://orca-mwe.cf.ac.uk/id/eprint/103602

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