A new low NOx emission technique for NH3/H2 blends in a flameless combustor through offset injection

IF 5.6 2区 工程技术 Q2 ENERGY & FUELS
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Abstract

The application of ammonia (NH3) as a possible future fuel presents a plausible solution for green energy storage. It helps provide a carbon-neutral fuel alternative for industrial power generation and transportation. However, the combustion of NH3 presents a formidable challenge due to its low reactivity, inadequate flame stability, sluggish flame propagation, and high NOx emissions. Consequently, its integration into combustion systems necessitates substantial system and strategy modification to enable its deployment to industrial systems. The current study presents a novel fuel/air injection technique, which emphasizes the high recirculation of hot combustion products and the extended residence time of fuel/air mixtures. A comprehensive experimental and numerical investigation is conducted using a swirl air injection and offset fuel injection to achieve the flameless combustion mode for optimized NH3/H2 fuel blends. A range of mixture conditions (ϕ = 0.5–1.2) and NH3/H2 compositions (50/50–70/30) are experimentally examined. The investigations helped elucidate the effect of residence time and recirculation on NOx emissions through kinetic simulations using a reactor network model. Subsequently, 3-D numerical simulations helped identify regions of high recirculation, quantified through reactant dilution ratios and uniform temperature distribution. These aspects are determined using a new parameter, the temperature uniformity index along the axial direction of the combustor. The emissions of NOx, unburnt NH3, and unburnt H2 are quantified for different equivalence ratios and NH3 mole fractions in the fuel mixture. The investigations reveal that NOx emissions reached their minimum (450–654 ppm) and (344-211 ppm), when the burner operated at lean (ϕ = 0.5–0.8) and rich (ϕ = 1.0–1.2) conditions, respectively, for 70/30 NH3/H2 blend. The emissions of unburnt NH3 and H2 species remain minimal for lean conditions. Both lean and rich operational regimes demonstrated similar or superior emission characteristics in flameless combustion mode when compared to the conventional combustion mode.
在无焰燃烧器中通过偏置喷射实现 NH3/H2 混合物低氮氧化物排放的新技术
氨(NH3)作为一种可能的未来燃料,为绿色能源储存提供了一种可行的解决方案。它有助于为工业发电和运输提供碳中和燃料替代品。然而,由于 NH3 的反应活性低、火焰稳定性不足、火焰传播缓慢以及氮氧化物排放量高,它的燃烧面临着严峻的挑战。因此,要将其集成到燃烧系统中,必须对系统和策略进行大量修改,才能将其应用到工业系统中。目前的研究提出了一种新型燃料/空气喷射技术,该技术强调热燃烧产物的高度再循环和燃料/空气混合物停留时间的延长。研究人员利用漩涡空气喷射和偏置燃料喷射进行了全面的实验和数值研究,以实现优化的 NH3/H2 混合燃料的无焰燃烧模式。实验研究了一系列混合条件(j = 0.5-1.2)和 NH3/H2 成分(50/50-70/30)。通过使用反应器网络模型进行动力学模拟,这些研究有助于阐明停留时间和再循环对氮氧化物排放的影响。随后,三维数值模拟帮助确定了高再循环区域,并通过反应物稀释比和均匀的温度分布进行了量化。这些方面是通过一个新参数,即沿燃烧器轴向的温度均匀性指数来确定的。针对燃料混合物中不同的当量比和 NH3 摩尔分数,对氮氧化物、未燃 NH3 和未燃 H2 的排放量进行了量化。研究表明,对于 70/30 NH3/H2 混合燃料,当燃烧器分别在贫油(j = 0.5-0.8)和富油(j = 1.0-1.2)条件下运行时,氮氧化物排放量分别达到最小值(450-654 ppm)和(344-211 ppm)。在贫油条件下,未燃烧的 NH3 和 H2 物种的排放量仍然很小。与传统燃烧模式相比,在无焰燃烧模式下,贫燃和富燃两种运行模式都具有相似或更优的排放特性。
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来源期刊
Journal of The Energy Institute
Journal of The Energy Institute 工程技术-能源与燃料
CiteScore
10.60
自引率
5.30%
发文量
166
审稿时长
16 days
期刊介绍: The Journal of the Energy Institute provides peer reviewed coverage of original high quality research on energy, engineering and technology.The coverage is broad and the main areas of interest include: Combustion engineering and associated technologies; process heating; power generation; engines and propulsion; emissions and environmental pollution control; clean coal technologies; carbon abatement technologies Emissions and environmental pollution control; safety and hazards; Clean coal technologies; carbon abatement technologies, including carbon capture and storage, CCS; Petroleum engineering and fuel quality, including storage and transport Alternative energy sources; biomass utilisation and biomass conversion technologies; energy from waste, incineration and recycling Energy conversion, energy recovery and energy efficiency; space heating, fuel cells, heat pumps and cooling systems Energy storage The journal''s coverage reflects changes in energy technology that result from the transition to more efficient energy production and end use together with reduced carbon emission.
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