Scaling of Pulverized-Fuel Jet Flames That Apply Large Amounts of Excess Air—Implications for NOx Formation

Measures to reduce nitrogen oxides (NOx) formation in industrial combustion processes often require up-scaling through pilot-scale facilities prior to being implemented in commercial scale, and scaling is therefore an important aspect of achieving lower NOx emissions. The current paper is a combined experimental and modelling study that aims to expand the understanding of constant velocity scaling for industrial jet flames applying high amounts of excess air. These types of flames are found in e.g., rotary kilns for production of iron ore pellets. The results show that, even if the combustion settings, velocity, and temperature profiles are correctly scaled, the concentration of oxygen experienced by the fuel during char combustion will scale differently. As the NO formation from the char combustion is important in these flames, the differences induced by the scaling has important impacts on the efficiencies of the applied primary measures. Increasing the rate of char combustion (to increase the Damköhler number), by using, for example, smaller-sized particles, in the pilot-scale is recommended to improve scaling.

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Numerical Simulation on Fluid Flow and Combustion in a Subcritical Pressure Boiler With Various Hybrid Coal

Volume 3: Combustion Science and Engineering ◽

10.1115/imece2008-68927 ◽

2008 ◽

Author(s):

Zaixing Zhu ◽

Jiemin Zhou ◽

Ying Wang ◽

Ping Zhou ◽

Aichun Ma

Keyword(s):

Fluid Flow ◽

Unstructured Mesh ◽

Natural Circulation ◽

Computational Results ◽

Simulation Data ◽

Excess Air ◽

Different Types ◽

Pulverized Fuel ◽

Flow Heat ◽

Combustion Processes

With a 300t/h Hg1025/18.2-YM13 sub-critical natural circulation tangentially corner-fired boiler serving as a prototype, a realizable k–ε turbulent mathematical model was established. This model used computational fluid dynamics software FLUENT6.2 and unstructured mesh generating technique of Gambit to reduce numerical false diffusion of the computational results. The fluid flow, heat transfer and combustion processes in the boiler were investigated numerically with different types of coal. The simulation data was compared and analyzed. The influences of primary air ratio, excess air ratio, pulverized fuel feeder on the combustion processes have been studied. These results could be of great help in the operation of tangentially fired furnace of pulverized coal boilers.

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Topological imaging of turbulent premixed, prevaporized liquid fuel jet flames using CH (C-X) band PLIF

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2020.08.021 ◽

2020 ◽

Author(s):

Thomas A. McManus ◽

Amirreza Gandomkar ◽

Campbell Carter ◽

Patton M. Allison

Keyword(s):

Liquid Fuel ◽

Jet Flames ◽

Fuel Jet ◽

X Band ◽

Turbulent Premixed

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Corrigendum to “Results of fly ash quality for disposal options from high thermal shares up to pure biomass combustion in a pilot-scale and large scale pulverized fuel power plants” [Renew Energy 75 (2015) 899–910]

Renewable Energy ◽

10.1016/j.renene.2015.01.051 ◽

2015 ◽

Vol 78 ◽

pp. 685

Author(s):

A. Fuller ◽

M. Carbo ◽

P. Savat ◽

J. Kalivodova ◽

J. Maier ◽

...

Keyword(s):

Fly Ash ◽

Power Plants ◽

Large Scale ◽

Pilot Scale ◽

Biomass Combustion ◽

Pulverized Fuel ◽

Disposal Options

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Sulphur Neutralization by Lignite Ash: Pilot-Scale Combustion Experiments

Journal of Engineering for Power ◽

10.1115/1.3446627 ◽

1979 ◽

Vol 101 (4) ◽

pp. 615-619 ◽

Cited By ~ 1

Author(s):

T. D. Brown ◽

G. K. Lee ◽

H. A. Bambrough

Keyword(s):

Nitric Oxide ◽

Flue Gas ◽

Solid Phase ◽

Coal Ash ◽

Pilot Scale ◽

Controlled Experiments ◽

Excess Air ◽

Nitric Oxide Emissions ◽

Carry Over ◽

Lime Addition

A pilot-scale research boiler (750 kg steam/hr) has been used to study the degree of sulphur neutralization during combustion experiments with three lignites. A series of four closely controlled experiments showed that sulphur balances close to 100 percent could be achieved in the pilot-scale system burning Gascoyne lignite; in these experiments the sulphur retained in solid phase residues varied between 21 and 24 percent of the input sulphur. It was also demonstrated with Utility lignite that external recirculation of flue-gas was moderately effective in reducing nitric oxide emissions at the expense of major increased in the carry-over of unburnt carbon. However, sulphur dioxide neutralization by the coal-ash cations remained essentially unchanged as the recirculation ratio increased. Enhancement of sulphur neutralization by dry lime addition to Poplar River lignite was only found to be effective at addition rates above 1/2 percent lime by weight. The effectiveness of the lime was found to increase as the excess-air level increased.

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Further Evaporation and Final Treatment of Process-Water Concentrates

Water Science & Technology ◽

10.2166/wst.1999.0691 ◽

1999 ◽

Vol 40 (11-12) ◽

pp. 25-32

Author(s):

Paterson McKeough ◽

Leena Fagernäs

Keyword(s):

Large Scale ◽

Treatment Process ◽

Treatment Options ◽

Paper Mill ◽

Pilot Scale ◽

Forced Circulation ◽

Final Treatment ◽

Solids Content ◽

Combustion Processes ◽

Future Work

The study is part of a longer-term effort aimed at developing a separate treatment process for evaporation-concentrates of paper-mill process waters. This article deals with research on the two key processing steps; namely, the further evaporation and the final treatment of the concentrates. In laboratory experiments, various feed waters, including several different TMP filtrates, were evaporated to high dry-solids contents. The condensates recovered in most experiments contained relatively small amounts of organic matter. The extent of vapourisation of organic acids, relative to water, increased somewhat with increase in dry-solids content. Two TMP concentrates from large-scale evaporation plants were further concentrated in a pilot-scale forced-circulation evaporator. Viscosity was the factor limiting the extent of concentration. Using an evaporation temperature of about 80°C, the maximum dry-solids contents achieved with the two different concentrates were about 45 wt% and about 60 wt%, respectively. Fouling of heat-transfer surfaces was observed with both concentrates. A techno-economic evaluation of final-treatment options for alkali-rich concentrates is under way. According to intermediate results, molten-phase combustion processes would not require support fuel once the dry-solids content of TMP concentrate exceeds about 50 wt%. The aim of future work is to optimise the overall treatment process.

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Assessment of Stabilization Mechanisms of Confined, Turbulent, Lifted Jet Flames: Effects of Ambient Coflow

Volume 1: Fuels and Combustion, Material Handling, Emissions; Steam Generators; Heat Exchangers and Cooling Systems; Turbines, Generators and Auxiliaries; Plant Operations and Maintenance ◽

10.1115/power2013-98033 ◽

2013 ◽

Cited By ~ 1

Author(s):

Andrew R. Hutchins ◽

James D. Kribs ◽

Richard D. Muncey ◽

Kevin M. Lyons

Keyword(s):

Turbulent Mixing ◽

Leading Edge ◽

Ambient Air ◽

Turbulent Jet ◽

Fuel Flow Rate ◽

Jet Flames ◽

Combustion Chemistry ◽

Intermittent Behavior ◽

Fuel Flow ◽

Fuel Jet

The aim of this investigation is to determine the effects of confinement on the stabilization of turbulent, lifted methane (CH4) jet flames. A confinement cylinder (stainless steel) separates the coflow from the ambient air and restricts excess room air from being entrained into the combustion chamber, and thus produces varying stabilization patterns. The experiments were executed using fully confined, semi-confined, and unconfined conditions, as well as by varying fuel flow rate and coflow velocity (ambient air flowing in the same direction as the fuel jet). Methane flames experience liftoff and blowout at well-known conditions for unconfined jets, however, it was determined that with semi-confined conditions the flame does not experience blowout. Instead of the conventional unconfined stabilization patterns, an intense, intermittent behavior of the flame was observed. This sporadic behavior of the flame, while under semi-confinement, was determined to be a result from the restricted oxidizer access as well as the asymmetrical boundary layer that forms due to the viewing window. While under full confinement the flame behaved in a similar method as while under no confinement (full ambient air access). The stable nature of the flame while fully confined lacked the expected change in leading edge fluctuations that normally occur in turbulent jet flames. These behaviors address the combustion chemistry (lack of oxygen), turbulent mixing, and heat release that combine to produce the observed phenomena.

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04/02968 Intermediate radical concentrations in hydrogen-natural gas blended fuel jet flames

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(04)80773-2 ◽

2004 ◽

Vol 45 (6) ◽

pp. 419

Keyword(s):

Natural Gas ◽

Jet Flames ◽

Intermediate Radical ◽

Fuel Jet ◽

Blended Fuel

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Environmentally sound destruction of hexachlorobutadiene during waste incineration in commercial- and pilot-scale rotary kilns

Journal of Environmental Chemical Engineering ◽

10.1016/j.jece.2019.103464 ◽

2019 ◽

Vol 7 (6) ◽

pp. 103464 ◽

Cited By ~ 1

Author(s):

Natsuko Kajiwara ◽

Yukio Noma ◽

Hidenori Matsukami ◽

Mayumi Tamiya ◽

Takumi Koyama ◽

...

Keyword(s):

Waste Incineration ◽

Pilot Scale ◽

Rotary Kilns ◽

Environmentally Sound

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NOx Emissions Modeling and Uncertainty From Exhaust-Gas-Diluted Flames

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4031603 ◽

2015 ◽

Vol 138 (5) ◽

Cited By ~ 7

Author(s):

Antonio C. A. Lipardi ◽

Jeffrey M. Bergthorson ◽

Gilles Bourque

Keyword(s):

Nox Reduction ◽

Flame Temperature ◽

No Production ◽

Exhaust Gas ◽

Oxides Of Nitrogen ◽

Nox Formation ◽

Kinetic And Thermodynamic Parameters ◽

Emissions Modeling ◽

Combustion Processes ◽

Gas Recirculation

Oxides of nitrogen (NOx) are pollutants emitted by combustion processes during power generation and transportation that are subject to increasingly stringent regulations due to their impact on human health and the environment. One NOx reduction technology being investigated for gas-turbine engines is exhaust-gas recirculation (EGR), either through external exhaust-gas recycling or staged combustion. In this study, the effects of different percentages of EGR on NOx production will be investigated for methane–air and propane–air flames at a selected adiabatic flame temperature of 1800 K. The variability and uncertainty of the results obtained by the gri-mech 3.0 (GRI), San-Diego 2005 (SD), and the CSE thermochemical mechanisms are assessed. It was found that key parameters associated with postflame NO emissions can vary up to 192% for peak CH values, 35% for thermal NO production rate, and 81% for flame speed, depending on the mechanism used for the simulation. A linear uncertainty analysis, including both kinetic and thermodynamic parameters, demonstrates that simulated postflame nitric oxide levels have uncertainties on the order of ±50–60%. The high variability of model predictions, and their relatively high associated uncertainties, motivates future experiments of NOx formation in exhaust-gas-diluted flames under engine-relevant conditions to improve and validate combustion and NOx design tools.

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