Numerical study of HCN and NH3 reduction in a two-stage entrained flow gasifier by implementing MILD combustion

Xu, Minyi; Tu, Yaojie; Zhou, Anqi; Xu, Hongpeng; Yu, Wenbin; Li, Zhenwei; Yang, Wenming

doi:10.1016/j.fuel.2019.03.135

Cited by 16 publications

(5 citation statements)

References 43 publications

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“…Syngas is a clean fuel that has been widely used in heating furnaces and gas turbines. , It is produced from coal, biomass, or waste by gasification, pyrolysis, or reforming processes . In actual syngas, there are a certain number of nitrogen-containing components (e.g., NH 3 ) resulted from the syngas production process. − NH 3 is a typical fuel-nitrogen precursor and the control of the fuel-NO x emission is essential for the combustion of ammonia-containing syngas. , The investigation on the oxidation of syngas-ammonia is crucial for suppressing the fuel-NO x emission from the combustion of actual syngas containing initial NH 3 .…”

Section: Introductionmentioning

confidence: 99%

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N₂ and CO₂ Atmospheres in a Jet-Stirred Reactor

Ding

Wang

et al. 2021

Energy Fuels

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Although syngas combustion has been extensively investigated, previous studies did not systematically examine the fuel-NO x formation from ammonia-containing syngas in both N2 and CO2 atmospheres. Investigations on syngas-ammonia oxidation are significant for suppressing the fuel-NO x emission from the combustion of actual syngas containing NH3. This study presents new experimental results on syngas-ammonia oxidation under both N2 and CO2 atmospheres in a jet-stirred reactor. The effects of CO2 concentration (X CO2: 0–60%), temperature (T: 900–1400 K), equivalence ratio (Φ: 0.4–1.65), initial CH4 concentration (X CH4: 0–2000 ppm), CO/H2 ratio, and residence time (τ: 0.001–10 s) are investigated. For the oxidation of syngas-ammonia, the reactant consumption is delayed and more CO is produced in high CO2 concentration. A critical temperature to obtain the peak N2O production is found, and it is slightly reduced from 1000 to 950 K with Φ increasing from 0.63 to 1.25. Moreover, the N2O concentration is basically insensitive to the concentration of CH4 and the CO/H2 ratio in syngas. The NO production is enhanced with the increase of T, X CH4, and the CO/H2 ratio, while it is reduced with increasing Φ. Interestingly, the high concentration of CO2 suppresses the fuel-NO formation in fuel-lean conditions, while it significantly enhances the fuel-NO production in fuel-rich conditions. To minimize emissions of NO, N2O, and CO, it is recommended to operate the reaction at T > 1000 K and simultaneously avoid significantly high temperatures at the equivalence ratio of approximately 0.9, low values of initial CH4 concentration and the CO/H2 ratio (e.g., <1), long residence times (τ > 2 s), and high concentrations of CO2 (X CO2 > 30%). Furthermore, the numerical simulations agree well with the vast majority of measurements, and the dependence of NO on Φ at X CO2 = 30% is also well predicted. The present study provides new fundamental understandings of the fuel-NO x formation from ammonia-containing syngas.

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Section: Introductionmentioning

confidence: 99%

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N₂ and CO₂ Atmospheres in a Jet-Stirred Reactor

Ding

Wang

et al. 2021

Energy Fuels

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“…The renormalization group (RNG) k –ε model with standard wall function is adopted for modeling turbulence, and this model works well for moderately swirling flows . The eddy dissipation concept (EDC) model is used to simulate the turbulence–chemistry interaction, and this combustion model can reasonably predict flameless combustion. ,,,,,,, The EDC model parameters are important for the prediction accuracy . For the present simulation, it has been examined that the turbulent Reynolds number is greater than 65 and default model parameters of C ξ = 2.1377 and C τ = 0.4082 are used.…”

Section: Methodsmentioning

confidence: 99%

“…They found that the performance of flameless combustion of dried sludge can be improved with a horizontal cyclone combustor. Xu et al 29 recently found through computational fluid dynamics (CFD) simulation that flameless combustion can reduce formations of HCN and NH 3 in the coal gasification process. Hu et al 30 extended the flameless combustion to burn the typical heterogeneous fuel of residual char.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study between Flameless Combustion and Swirl Flame Combustion Using Low Preheating Temperature Air for Homogeneous Fuel NO Reduction

Ding

Shi

et al. 2021

Energy Fuels

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The reduction of NO x emission in the combustion process is of vital importance to satisfy the increasingly strict NO x emission standards. Although substantial progress has been made for fuel NO reduction in conventional flame combustion, the homogeneous fuel NO mechanism in flameless combustion has not been systematically investigated. This paper performs a detailed comparative study between flameless combustion and conventional swirl flame combustion for homogeneous fuel NO reduction by both experiments and numerical simulations. The simulations are validated with experiments. It is found that the equivalence ratio (Φ) is significant for the stability and performance of flameless combustion. First, we found that the critical Φ to achieve flameless combustion is reduced with the increase of air preheating temperature. Second, importantly, with the increase of Φ from 0.68 to 0.82 a decreasing tendency of fuel NO emission is found in our experiments, which is the opposite of high temperature combustion. Considering that CO emissions are sharply increased when Φ > 0.8, there is a recommended Φ (i.e., Φ = 0.8 for the present study) to obtain the minimum emissions of fuel NO and CO in flameless combustion. Moreover, our experiments for the first time show that flameless combustion can reduce the homogeneous fuel NO emission by 60–85% relative to swirl flame combustion. Reaction pathway analysis demonstrates that in flameless combustion fuel NO is mostly formed via the NH3 → NH2 → HNO → NO path while NO is reduced through the pathway NO → HCN → NCO → N2. The present study reports the advantage of flameless combustion using low preheating temperature air for significant reduction of homogeneous fuel NO and provides new fundamental understandings of the fuel NO mechanism.

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“…В этом случае необходимы модели, учитывающие кинетику физико-химических превращений топливной частицы в несущем потоке газа. 2D-и 3D-моделирование газогенераторов позволяет решить ряд конструкционных или режимных вопросов, на-пример, связанных с выбором расположения питателей [21,22]. Однако для анализа большого количества вариантов эти модели оказываются слишком ресурсоемкими, поэтому на первом этапе анализа обычно достаточно более упрощенного рассмотрения.…”

Section: исходные данные для расчетовunclassified

Influence of Gasification Agent Parameters on the Efficiency of High-Temperature Staged Pulverized Coal Gasification Process

2020

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Numerical study of HCN and NH3 reduction in a two-stage entrained flow gasifier by implementing MILD combustion

Cited by 16 publications

References 43 publications

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N₂ and CO₂ Atmospheres in a Jet-Stirred Reactor

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N₂ and CO₂ Atmospheres in a Jet-Stirred Reactor

Comparative Study between Flameless Combustion and Swirl Flame Combustion Using Low Preheating Temperature Air for Homogeneous Fuel NO Reduction

Influence of Gasification Agent Parameters on the Efficiency of High-Temperature Staged Pulverized Coal Gasification Process

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Numerical study of HCN and NH3 reduction in a two-stage entrained flow gasifier by implementing MILD combustion

Cited by 16 publications

References 43 publications

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N2 and CO2 Atmospheres in a Jet-Stirred Reactor

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N2 and CO2 Atmospheres in a Jet-Stirred Reactor

Comparative Study between Flameless Combustion and Swirl Flame Combustion Using Low Preheating Temperature Air for Homogeneous Fuel NO Reduction

Influence of Gasification Agent Parameters on the Efficiency of High-Temperature Staged Pulverized Coal Gasification Process

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Product

Resources

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Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N₂ and CO₂ Atmospheres in a Jet-Stirred Reactor

Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N₂ and CO₂ Atmospheres in a Jet-Stirred Reactor