超小断面切圆贫煤锅炉在掺烧烟煤时存在结渣严重、高温腐蚀等问题,为适应当前煤炭市场多元化及锅炉灵活性运行等需求,亟待提升其对复杂煤种掺烧的适应性。以某电厂300MW超小断面四角切圆燃烧锅炉为研究对象,开展煤种适应性燃烧改造研究。首先,利用CFD数值模拟方法评估出锅炉原燃烧系统在掺烧烟煤时存在的燃烧问题,从而针对性地提出燃烧系统改造方案,通过增加燃烧器间距降低燃烧器区域热负荷、减小假想切圆解决火焰刷墙、增加燃尽风率实现深度空气分级等措施,拓展锅炉对煤质的适应能力;进而运用CFD数值模拟方法确定了该燃烧改造方案最佳的性能参数,预测了燃烧改造后锅炉在掺烧67%及100%低灰熔融温度烟煤下的燃烧状态,并通过工程试验验证了该燃烧改造的有效性。结果表明,燃烧改造后该300MW超小断面四角切圆燃烧锅炉燃用煤质可由原掺烧20%烟煤到适应掺烧67%~100%低灰熔融温度烟煤,有效增强了煤种适应性。经第三方考核试验,改造后燃用设计煤工况锅炉效率提高2.25%、NOx排放率降低40%~48%、炉膛未出现明显结渣及高温腐蚀问题。该燃烧改造方案为国内原设计贫煤的切圆燃烧锅炉拓展烟煤适应性提供借鉴。

Ultra-small section circle lean coal boiler has problems such as serious slagging and high temperature corrosion. In order toadapt to the current coal market diversification and boiler flexibility operation and other needs,it is urgent to improve its adaptabilityto complex coal blending. Taking the 300 MW ultra-small section of a power plant as the research object,the coal adaptive combustion modification was carried out. Firstly,CFD numerical simulation was used to evaluate the combustion problems of the original combustion system of the boiler when mixed with bituminous coal,then the modification scheme of the combustion system was put forward accordingly: by increasing the burner distance to reduce the heat load of the burner area,reducing the imaginary circle to solve the flame brushwall,increasing the burn out air rate to achieve deep air classification and other measures,the coal type adaptability of the boiler could beexpanded. Then CFD numerical simulation was used to determine the best performance parameters of the combustion modification scheme,and predict the combustion state of the boiler under 67% and 100% low ash bituminous coal after combustion modification. The effectiveness of the combustion modification was verified through the engineering test. The results show that the 300 MW ultra-small section circle-fired boiler can be mixed with 20% bituminous coal to adapt to burn 67%-100% low ash melting point bituminous coal,so the adaptabilityof coal species can be effectively enhanced. According to the official assessment and test, the efficiency of the boiler in thedesigned coal condition is improved by 2.25%,NO emission rate is reduced by 40%-48%,and there is no obvious slagging and high temperature corrosion problems in the furnace. The combustion modification scheme provides guidance for the adaptability of bituminous coal.