Analysis of air-staged combustion of NH3/CH4 mixture with low NOx emission at gas turbine conditions in model combustors
Analysis of air-staged combustion of NH3/CH4 mixture with low NOx emission at gas turbine conditions in model combustors
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DOI：
10.1016/j.fuel.2018.09.131
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发表时间：
2019-02
期刊：
影响因子：
7.4
通讯作者：
Shangpeng Li;Shanshan Zhang;Hua Zhou;Zhuyin Ren
中科院分区：
文献类型：
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作者：
Shangpeng Li;Shanshan Zhang;Hua Zhou;Zhuyin Ren
在由完全搅拌反应器 (PSR) 和活塞流反应器 (PFR) 组成的 NH3/CH4 燃烧模型燃烧室中，具有 84 种 Tian 机制，在燃烧室出口处 23atm 和 1873K 的燃气轮机相关条件下，对 NOx 形成特性进行了数值研究。具体来说，首先在非分级模型燃烧室中研究了 NH3 稀释对 NOx 形成的影响，该燃烧室由一个代表主燃烧区的 PSR 和一个代表后燃烧区的 PFR 在 NH3/CH4 燃料中 NH3 体积比的较宽范围内组成。研究发现，随着NH3的添加，NOx排放量急剧增加，主要是通过增强主反应区的HNO路径。认识到通过 HNO 途径形成的 NOx 受到氧气可用性的限制，然后在不同的 NH3 稀释水平下量化了燃料/空气当量比对 NOx 形成的影响。结果表明，在燃料丰富的条件下，通过 HNO 途径形成的 NOx 可以通过其他途径（例如与 NHi 相关的途径）的减少来抵消，从而导致整体低 NOx 排放。最后，提出了一种空气分级模型燃烧系统，其中初级当量比选择为1.5，以利用富燃料条件下的低NOx排放。两级空气分流由固定出口温度1873K决定，参数研究表明，即使NH3体积比达到40%，简单的两级燃烧也能实现低于30ppm的NOx排放，大大低于非分级燃烧的数千ppm。结果通过47种Konnov机制得到进一步验证，证明了空气分级燃烧在NH3/CH4燃烧中低NOx排放的巨大潜力。
The NOxformation characteristics have been numerically investigated in the NH3/CH4fired model combustor consisting of perfectly stirred reactors (PSR) and plug flow reactors (PFR) with 84-species Tian mechanism at gas-turbine relevant conditions of 23 atm and 1873 K at the combustor outlet. Specifically, the impacts of NH3dilution on NOxformation were first studied in a non-staged model combustor consisting of one PSR representing main combustion zone and one PFR representing post-combustion zone over a wide range of the volumetric ratio of NH3in the NH3/CH4fuel. It was found that the NOxemission increases sharply with the NH3addition mainly through the enhanced HNO pathway in the main reaction zone. Recognizing that the NOxformation via the HNO pathway is limited by the availability of oxygen, the effects of fuel/air equivalence ratio on NOxformation were then quantified under different levels of NH3dilution. It was revealed that at fuel-rich conditions, the NOxformation via HNO pathway can be offset by the reduction via other pathways, such as pathways related to NHi, leading to the overall low NOxemission. Finally, an air-staged model combustion system was proposed, in which the equivalence ratio in the primary stage was chosen to be 1.5 to take advantage of the low NOxemission under fuel-rich conditions. The air split among the two stages was determined by the fixed outlet temperature of 1873 K. A parametric study demonstrated that less than 30 ppm NOxemission can be achieved with simple two-stage combustion even when the volumetric ratio of the NH3reaches 40%, which is dramatically lower than the one of thousands ppm in the non-staged combustion. The results were further verified with the 47-species Konnov mechanism, demonstrating the great potential of air-staged combustion for low NOxemission in the NH3/CH4fired combustion.