Numerical investigation on pyrolysis and ignition of ammonia/coal blends during co-firing

Ma, Peng; Nicolai, Hendrik; Huang, Qian; Debiagi, Paulo; Berkel, Leon Loni; Stagni, Alessandro; Yang, Yuanping; Hasse, Christian; Li, Shuiqing

doi:10.1016/j.combustflame.2023.113268

Cited by 4 publications

(6 citation statements)

References 66 publications

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“…Finally, ω̇ k represents the chemical reaction rate calculated using various reaction mechanisms incorporating the Arrhenius equation. The gas-phase reactions are accounted for using the detailed reaction mechanism established by Okafor et al This mechanism is chosen based on the following considerations: (1) it has been proven to be accurate for describing ammonia/methane flames through comparison with experimental data; (2) our previous studies , demonstrated that the overall PCC flame structure predicted using high hydrocarbon volatile components can be well reproduced when volatile components are assumed as a combination of light gases; (3) recently, it has also been successfully used for the co-combustion of coal and ammonia, and reasonable agreement with experimental data can be obtained; (4) the current work mainly focuses on the FPV model, and the main discussion and conclusion are minimally impacted by the selection of the reaction mechanism; (5) the number of species and reactions (59 species and 356 reactions) is significantly smaller than those in the mechanism used in ref (129 species and 1644 reactions) and the mechanism used in ref (116 species and 1513 reactions). This can significantly save computational cost for 3D PP-DNS.…”

Section: Numerical Methods and Modelsmentioning

confidence: 99%

“…Additionally, Cardoso et al proposed a two-dimensional Eulerian-Lagrangian numerical model for ammonia/coal co-firing to explore the impact of the NH 3 co-firing ratio on heat release, as well as carbon and NO emissions. Recently, several studies have investigated the reaction mechanisms of ammonia/coal co-firing and the associated NO x generation mechanism. − These studies have significantly advanced the application of numerical simulations in the field of ammonia/coal co-firing.…”

Section: Introductionmentioning

confidence: 99%

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Direct Numerical Simulation and Flamelet Modeling of Coal/Ammonia Cofiring Flame

Xue,

Xing,

Tang

et al. 2024

Energy Fuels

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Combusting ammonia with coal is regarded as an effective technical approach for reducing carbon emissions. This process involves multiple fuel streams and nitrogen sources, posing challenges for accurate and efficient modeling of combustion and NO formation. The present paper presented a point-particle direct numerical simulation (PP-DNS) work with detailed chemistry for a coal/ammonia co-firing flame, and a flamelet/progress variable (FPV) model for ammonia/coal co-firing was applied to consider the multiple fuel streams and reacting stages. The performance of the extended FPV model was evaluated by conducting a priori analyses with the PP-DNS solution as benchmarks. The gas temperature, major species, and CO profiles in the PP-DNS can be well reproduced by the extended FPV model. The reaction time scale analysis indicated that NO is formed on the same order of time scale as those of the major species in this flame. Therefore, it can be acceptably predicted by directly extracting data from the flamelet tables. Incorporating NO in the progress variable does not enhance the NO prediction and lowers the accuracy of the temperature and major species predictions. The main deviations of NO prediction can be attributed to the multi-dimensional effect.

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Section: Numerical Methods and Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Direct Numerical Simulation and Flamelet Modeling of Coal/Ammonia Cofiring Flame

Xue,

Xing,

Tang

et al. 2024

Energy Fuels

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“…The variation of the ignition delay distance was mainly related to the competitive role between the ignition delay effect brought by the reduction of the local oxygen concentration and gas-phase mixture reactivity and the ignition advance effect brought by the increase of coal particle temperature and the acceleration of volatile matter pyrolysis due to ammonia blending. 35 The preheating effect of ammonia combustion promoted the ignition advance of the coal at low ammonia blending ratios. 33 However, as E NH3 increased, the ignition delay effect gradually surpasses the ignition advance effect, resulting in an increase in the ignition delay with higher E NH3 .…”

Section: Flame Morphology Of Coal/ammonia Ignitionmentioning

confidence: 99%

“…Conversely, Ma et al’s investigation on the co-combustion phenomenon of high volatile coal and ammonia by means of a two-stage flat flame burner revealed that the ignition time τ OH monotonically increased with the increase of ammonia blending ratio at the oxygen concentration X i,O2 = 0 . Their subsequent numerical simulations showed that the ignition delay caused by ammonia blending was mainly related to the decrease in the reactivity of oxygen-fuel mixture and local oxygen concentration …”

Section: Introductionmentioning

confidence: 98%

“…34 Their subsequent numerical simulations showed that the ignition delay caused by ammonia blending was mainly related to the decrease in the reactivity of oxygen-fuel mixture and local oxygen concentration. 35 The investigation of the interaction between coal particles and ammonia under consistent experimental conditions remains limited. This gap represents a significant challenge for understanding non-additive behaviors, improving combustion efficiency, and controlling pollutant emissions in coal and ammonia co-combustion.…”

Section: Introductionmentioning

confidence: 99%

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Ignition Characteristics and Interaction of Coal and Ammonia Co-Combustion on a Diffusion-Flamelet-Based Hencken Burner

Yang,

Zhou,

et al. 2024

Energy Fuels

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Co-combustion of coal and ammonia presents an effective strategy to gradually reduce the share of coal-fired power generation and, thereby, achieve CO 2 reduction. In this work, the ignition characteristics and interaction of coal and ammonia cocombustion with varying ammonia blending ratios (0−100%) under different oxygen concentrations (5%−30%) were investigated on a diffusion-flamelet-based Hencken burner. The flame morphologies of coal and ammonia co-combustion under different operating conditions were captured through the co-combustion flame images. And the flame radial intensity profiles at the cross sections of the ignition positions exhibited a bimodal distribution at 20% and 30% O 2 concentrations with the addition of ammonia, which were not observed at 5% and 10% O 2 concentrations or in pure coal combustion scenarios. Correspondingly, the trend in the flame diameter of coal and ammonia co-combustion with the increase of ammonia blending ratio shifted from initially increasing and then decreasing at 5% and 10% O 2 concentrations to a monotonically increasing one at 20% and 30% O 2 concentrations. Furthermore, the chemiluminescence spectrum of coal and ammonia co-combustion was measured to analyze the evolution of the radicals at different ammonia blending ratios, and the NH* and OH* radical signals were used to correlate the intensity of the gas-phase reaction of ammonia and coal volatile matter combustion. It was found that the interaction between ammonia and coal became more pronounced at higher oxygen concentrations. Notably, the NH*/OH* ratio at the outlet of the central fuel tube was strongly correlated with the ignition delay distance of coal and ammonia co-combustion. Finally, the variation of the coal particle temperatures during the ignition stage was analyzed to elucidate the interaction of the co-combustion process. In most cases, the addition of ammonia led to an increase in the maximum temperature of the coal particles. This effect was primarily influenced by the particle number density (PND) of the pulverized coal and the distribution of the thermal input between the coal and ammonia.

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Comparative study on co-firing characteristics of normal and superfine pulverized coal blended with NH3 under the MILD combustion mode

Zha,

Zhang,

Zhao

et al. 2024

Energy

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Numerical investigation on pyrolysis and ignition of ammonia/coal blends during co-firing

Cited by 4 publications

References 66 publications

Direct Numerical Simulation and Flamelet Modeling of Coal/Ammonia Cofiring Flame

Direct Numerical Simulation and Flamelet Modeling of Coal/Ammonia Cofiring Flame

Ignition Characteristics and Interaction of Coal and Ammonia Co-Combustion on a Diffusion-Flamelet-Based Hencken Burner

Comparative study on co-firing characteristics of normal and superfine pulverized coal blended with NH3 under the MILD combustion mode

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