文献类型： 外文期刊

第一作者： Guo, Shuai

作者： Guo, Shuai;Qi, Guoliang;Gao, Long;Qu, Hongwei;Li, Xingcan;Zhao, Deng;Song, Dean

作者机构：

关键词： Hydrochar; NH3; Co-combustion; ReaxFF MD; Oxygen equivalence ratio; Ammonia co-combustion ratio

期刊名称：JOURNAL OF ENVIRONMENTAL MANAGEMENT （ 影响因子：8.4； 五年影响因子：8.6 ）

ISSN： 0301-4797

年卷期： 2025 年 391 卷

页码：

收录情况： SCI

摘要： Co-combustion of NH3 (ammonia) and hydrochar is a promising strategy to reduce fossil fuel usage and CO2 emissions. In this study, reactive molecular dynamics simulations (ReaxFF MD) were performed to investigate the effects of oxygen equivalence ratio (lambda), ammonia co-combustion ratio, and combustion atmosphere on the combustion characteristics of the NH3/hydrochar mixture. Firstly, Increasing the oxygen equivalence ratio from 0.5 to 1.5 accelerated the reaction and enhanced fuel conversion: the total molecule count rose by similar to 56 % (from 2449 to 3810), and heavy coke species (C40(+) compounds) were completely eliminated at lambda >= 1.0. A higher lambda facilitated the conversion of H-2 into H2O and N-2 into NO/NO2, increasing H2O, NO, and NO2 yields while suppressing H-2 and N-2. At lambda = 0.5, no CO2 or NO2 formed; at lambda = 1.5, small amounts appeared, with CO produced being several-fold more abundant than CO2. Correspondingly, the peak NH2 intermediate count increased from 181 to 233 as lambda rose from 0.5 to 1.5, whereas N2Hx intermediates (N2H2, N2H3, N2H4) declined - an oxygen-driven shift favoring NO formation over N-2. Secondly, increasing the ammonia co-combustion ratio from 62.5 % to 85 % led to higher final yields of CO, NO, and N-2, with a corresponding drop in residual unconverted carbon (UC). A greater NH3 proportion promoted the conversion of hydrochar into small molecules (C-1-C-4 gases), thereby reducing tar and coke formation (fewer tar/coke species at 85 % NH3 than at 62.5 %). Mechanistic analysis showed that a hydrochar fragment (C49H40O5) can be stepwise broken down by NH3-derived radicals (e.g. NH2, OH, H) into intermediate species such as C49H38O5 and C49H37O5, ultimately producing CO. Finally, the combustion atmosphere had a notable impact on reaction heat release. Under both air (O-2/N-2) and pure O-2 conditions, the co-combustion process began with an endothermic phase followed by exothermic heat release. The peak heat absorption at lambda = 1.0 reached 69.18 Ha under pure O-2, much higher than the 16.78 Ha under air, indicating a more intense initial reaction in an oxygen-rich environment. By the end of 500 ps, however, the net energy released in air (20.62 Ha) slightly exceeded that in pure O-2 (14.10 Ha). These results demonstrate that pure oxygen accelerates fuel consumption and product formation, whereas air yields a greater overall energy release - providing quantitative insight for optimizing practical NH3-hydrochar co-combustion.

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