600 MW旋流对冲锅炉燃烧器燃尽特性及其优化数值模拟

Numerical simulation on burner burnout characteristics and optimization in a 600 MW swirling opposed boiler

在实际运行中,旋流对冲燃烧锅炉的大风箱分配到同层各燃烧器的流量不均匀,显著影响煤粉的燃尽特性。然而,对该炉型锅炉炉内单个燃烧器的燃尽特性研究相对较少。基于此,以一台600 MW前后墙旋流对冲锅炉为对象,开展炉内燃烧器燃尽特性及其优化的数值模拟,探究燃烧器不同配风方式、旋流强度及出力对煤粉燃尽特性影响。模拟结果表明,下层燃烧器对应的飞灰含碳量高于中、上层燃烧器;中间燃烧器对应的飞灰含碳量(平均值约0.1%)低于两侧燃烧器(平均值约3%),这与现场测量的结果基本一致。侧墙附近燃烧器煤粉的不完全燃烧是锅炉出口飞灰含碳量的主要来源。适当减少中间燃烧器的风量并增加侧墙附近燃烧器的风量对中间燃烧器煤粉的燃尽特性影响相对较小,但能有效改善靠近侧墙燃烧器煤粉的燃尽特性(飞灰含碳量从3.0%降至1.6%以内);适当增加侧墙附近燃烧器二次风旋流强度或提高中间燃烧器出力、降低侧墙附近燃烧器出力,也可有效降低侧墙燃烧器对应的飞灰含碳量(2%以内),改善锅炉煤粉燃尽特性。

In actual operation,the flow rate into the same-layer burners from the large air box is uneven for the swirl opposed-firing boiler,which will significantly affect the burnout characteristics of pulverized-coal.However,there are the research on the burn-out characteristics of single burner in the furnace.Taking a 600 MW front and rear wall swirl opposed boiler as the object,the numerical study and optimization on the burnout characteristics were carried out,and the effects of the air distribution,the swirl intensity and the burner output on burnout characteristics of pulverized coal were also studied.The simulated results show that the carbon content in the fly ash of the lower burner is higher than that of the upper and middle burners,and the carbon content(about 0.1%)in the fly ash of the middle burner is lower than that of the side burners(about 3%),which is consistent with the field measurement results.The incomplete combustion of pulverized-coal from the burner near the side walls is the main source of the carbon content in the fly ash.There is a relatively small impact on the burnout characteristics of the middle burner by appropriately reducing the air ratio of the middle burner and increasing the air ratio of the burners near the side wall,which can effectively improve the burnout characteristics of the burners near the side wall(the carbon content in fly ash reduces from 3%to less than 1.6%).Appropriately increasing the swirling intensity of the burner near the side wall,or properly increasing the output of the middle burner and reducing the combustion output of the burners near the side wall,can significantly reduce the carbon content(less than 2%)in the fly ash of the burners near the side wall and improve the pulverized coal burnout characteristics.