Combustion features of CH4/NH3/H2 ternary blends
Combustion features of CH4/NH3/H2 ternary blends
复制标题
DOI：
10.1016/j.ijhydene.2022.03.254
复制
发表时间：
2022-04
影响因子：
7.2
通讯作者：
S. Mashruk;M. Vigueras-Zuñiga;M. Tejeda-del-Cueto;H. Xiao;C. Yu;U. Maas;A. Valera-Medina
中科院分区：
文献类型：
--
作者：
S. Mashruk;M. Vigueras-Zuñiga;M. Tejeda-del-Cueto;H. Xiao;C. Yu;U. Maas;A. Valera-Medina
在过去的几十年里，所谓的“绿色”氢用于能源和推进部门的脱碳引起了相当大的关注。尽管取得了进步，但在直接用于燃气轮机等动力系统时，氢仍然存在一些限制。因此，另一种载体如氨可以作为一种化学物质来运输和分配绿色氢，而它在燃气轮机中的使用可以限制燃烧反应性，与氢相比，可操作性更好。然而，纯氨本身表现出缓慢而复杂的反应动力学，这需要更多的活性分子掺杂，从而确保更大的火焰稳定性。预计在未来几年内，氨将在发电和供热装置中取代天然气（含约90%的甲烷），从而使氨/甲烷共烧成为替代CH4as化石燃料的明确途径。氢可以从氨的预裂解中获得，因此表明了通过使用氨/氢混合物实现脱碳的明确途径。因此，氨/甲烷/氢可能在当前燃烧装置的某个阶段共燃，因此需要对这些三元混合物产生的稳定性、排放和火焰特征进行更内在的分析。作为回报，这将确保从天然气到可再生能源产生的电子燃料（如所谓的“绿色”氢和氨）的过渡，对设备和工艺的损害很小。为此，本文分析了不同浓度的氨/甲烷/氢共混物的燃烧特性。通用切向旋流燃烧器在恒功率和不同当量比下工作。得到了辐射、OH * /NH * /NH2 * /CH *化学发光、可操作性图和光谱特征，并进行了讨论。本文还研究了应变层流预混火焰的消光行为。总体而言，从化石燃料到电子燃料的转变是由OH、CH、CN和NH2等自由基的反应性变化主导的，在低氨和高氨含量下排放增加。同时，当注入量达到30% （vol）时，氢的加入提高了可操作性，超过这个量，氢就开始控制混合物的反应性。消光应变率证实了实验中发现的现象，高氨混合物在不同氢含量下的值之间存在很大差异。最后，在高当量比（1.2）下，20/55/25%（体积）的甲烷/氨/氢混合物似乎是最有希望的，没有明显的闪回，排放低，NH2/OH自由基形成适中，可操作性好。
The use of so-called “green” hydrogen for decarbonisation of the energy and propulsion sectors has attracted considerable attention over the last couple of decades. Although advancements are achieved, hydrogen still presents some constraints when used directly in power systems such as gas turbines. Therefore, another vector such as ammonia can serve as a chemical to transport and distribute green hydrogen whilst its use in gas turbines can limit combustion reactivity compared to hydrogen for better operability. However, pure ammonia on its own shows slow, complex reaction kinetics which requires its doping by more reactive molecules, thus ensuring greater flame stability. It is expected that in forthcoming years, ammonia will replace natural gas (with∼90% methane in volume) in power and heat production units, thus making the co-firing of ammonia/methane a clear path towards replacement of CH4as fossil fuel. Hydrogen can be obtained from the pre-cracking of ammonia, thus denoting a clear path towards decarbonisation by the use of ammonia/hydrogen blends. Therefore, ammonia/methane/hydrogen might be co-fired at some stage in current combustion units, hence requiring a more intrinsic analysis of the stability, emissions and flame features that these ternary blends produce. In return, this will ensure that transition from natural gas to renewable energy generated e-fuels such as so-called “green” hydrogen and ammonia is accomplished with minor detrimentals towards equipment and processes. For this reason, this work presents the analysis of combustion properties of ammonia/methane/hydrogen blends at different concentrations. A generic tangential swirl burner was employed at constant power and various equivalence ratios. Emissions, OH∗/NH∗/NH2∗/CH∗ chemiluminescence, operability maps and spectral signatures were obtained and are discussed. The extinction behaviour has also been investigated for strained laminar premixed flames. Overall, the change from fossils to e-fuels is led by the shift in reactivity of radicals such as OH, CH, CN and NH2, with an increase of emissions under low and high ammonia content. Simultaneously, hydrogen addition improves operability when injected up to 30% (vol), an amount at which the hydrogen starts governing the reactivity of the blends. Extinction strain rates confirm phenomena found in the experiments, with high ammonia blends showing large discrepancies between values at different hydrogen contents. Finally, a 20/55/25% (vol) methane/ammonia/hydrogen blend seems to be the most promising at high equivalence ratios (1.2), with no apparent flashback, low emissions and moderate formation of NH2/OH radicals for good operability.