燃煤锅炉掺氨燃烧研究进展

Research Progress on Co-firing Ammonia in Coal-fired Boiler

将零碳燃料氨在燃煤锅炉中进行掺烧,是极具潜力的电力系统低碳化改造路径之一,对我国“双碳”目标的实现具有重要意义。由于氨与煤的理化特性迥异,掺氨燃烧将对燃煤锅炉的运行造成一系列影响。本文总结国内外相关研究,从氨燃料特性出发,简述了氨燃烧增强策略,分析了掺氨对燃煤锅炉传热、燃烧及NO_(x)排放、受热面安全、锅炉效率及[火用]效率的影响,最后对燃煤锅炉掺氨燃烧的研究进行了展望。研究表明,氨在储运成本及安全性方面具有优势,但其燃烧特性与氢气、天然气等气体燃料相比存在差距,可通过与挥发分共燃、富氧燃烧、燃料预热等策略实现氨燃料的稳定着火及燃尽,而这些策略在燃煤锅炉中均可较方便地实施。掺氨比例越高,炉内辐射传热量降低,对流传热量增加。在空气分级条件下,若燃烧组织得当,掺氨燃烧后NO_(x)排放甚至不升反降。此外,燃煤锅炉掺氨燃烧可能会加剧尾部受热面的低温腐蚀,系统[火用]效率性也略有降低。未来,氮氧化物的生成机理与预测模型、氨煤掺烧锅炉炉内的多场耦合机制等将是燃煤锅炉掺氨燃烧领域研究的重点方向,相关数值模拟子模型的完善以及中试以上规模燃煤锅炉掺氨燃烧的工程验证也亟待开展。

Co-firing ammonia in coal-fired boilers is one of the potential paths for low carbon transformation of the power system in China,which is of great significance for the carbon peaking and carbon neutrality goals.Because of the different physical and chemical properties between ammonia and coal,ammonia co-combustion will cause a series of impacts on the co-fired boilers.This paper summarizes the recent studies on the coal/ammonia co-firing.Starting from the characteristics of ammonia,the enhancement strategy of ammonia combustion is briefly described.The influences of ammonia blending on the heat transfer,combustion and NO_(x) emission,safety of the heating surfaces and the thermal economy of coal-fired boilers are analyzed.Finally,the prospect of the future work on ammonia co-firing in the coal-fired boilers is put forward.The results show that ammonia has advantages in storage,transportation and safety,but its combustion characteristics are not as good as those of other gaseous fuels such as hydrogen and natural gas.The ignition and burnout behaviors of ammonia can be enhanced by co-combustion with volatiles,oxy-fuel combustion and preheating.All these strategies can be implemented conveniently in coal-fired boilers.Higher ammonia blending ratio brings less radiation but more convection heat transfer.Under the condition of air-staging combustion,the NO_(x) emission in coal/ammonia cases could even be lower than that in coal-fired case if the combustion is well-organized.In addition,ammonia co-firing may aggravate the low temperature corrosion of the tail heating surfaces,and may cause adverse impacts on the exergy efficiency of the system.In the future,the formation mechanisms and prediction model of NO_(x),the multi-field coupling in ammonia/coal co-firing boiler will be the key research directions.The improvement of the simulation sub-models and the engineering verification of ammonia co-firing in large-scale coal-fired boilers are also urgent to be addressed.