预燃室旋流煤粉燃烧器低负荷运行燃烧特性试验研究

Experiment study on combustion characteristic of swirl burner with precombustion chamber under low-load operation

预燃室旋流燃烧器的燃烧特性与运行条件和操作参数密切相关,直接影响煤粉燃尽度和污染物排放,一直是工业锅炉系统关注研发的重点。为了探讨预燃室旋流燃烧器在低负荷运行下的燃烧特性及合理操作参数,以14 MW煤粉燃烧试验台架为基础,通过高温热电偶、烟气分析仪和高速摄像机对预燃室内的温度分布、组分体积分数分布及预燃室外的火焰形态进行测量,分析煤粉在预燃室内、外的燃烧过程,同时对其关键操作参数内外二次风量比进行优化。试验结果表明:低负荷运行下预燃室旋流燃烧器可实现煤粉稳定燃烧,同时预燃室内形成中心高温无氧强还原性气氛区域和边壁低温空气层,沿径向出现“风包火、火包粉”的燃烧状态,有利于抑制燃烧初期NO生成和保障燃烧器低负荷长期稳定运行;预燃室外形成稳定性较高的湍流扩散火焰,较长火焰行程及火焰锋面强烈热质交换有利于煤粉后续在炉膛内燃尽,且预燃室出口可避免高温腐蚀;同时在内外二次风量比为1∶2的工况下无氧区域半径最大R=171 mm与其他工况差异较小,而平均温度峰值为1 122℃,强还原性气氛中平均CO体积分数峰值为13.713%,明显优于其他工况,以及火焰行程中火焰长度为4 473 mm优于其他工况,有利于进一步降低NO含量和提高煤粉燃尽率,可作为预燃室旋流燃烧器在46%负荷、过量空气系数1.63,内二次风旋流数1.6运行条件下的最优工况。

The combustion characteristics of swirl burners with precombustion chamber are closely related to the operating conditions and parameters, which directly affect the coal burnout and pollutant emission. It has always been the focus of industrial boiler system research and development. In order to explore the combustion characteristics and reasonable operating parameters of pre-combustion chamber swirl burner under low load operation, the pre-combustion chamber was monitored by high temperature thermocouple, flue gas analyzer and high-speed camera. The temperature distribution, component concentration distribution and flame shape outside the pre-combustion chamber were measured by high-temperature thermocouple, flue gas analyzer and high-speed camera on the basis of 14 MW pulverized coal combustion test-bed in this paper. The combustion process of pulverized coal in and outside the precombustion chamber was analyzed, and the inner and outer secondary air mass flow ratios was optimized. The test results showed that the pre-chamber swirl burner can achieve stable combustion of pulverized coal under low load operation. Meanwhile, the high-temperature anaerobic strong reducing atmosphere area in the center and the low-temperature air layer on the side wall were formed in the precombustion chamber, and the "fire in air and pulverized coal in fire" combustion state was appeared along the radial direction, which was conducive to restrain NOgeneration at the initial stage of combustion and keep long-term stable low operating load. The stable turbulent diffusion flame was formed outside precombustion chamber. The exchange is conducive to the subsequent combustion of the pulverized coal in the furnace, and the outlet of the pre-combustion chamber can avoid high temperature corrosion. At the same time, the maximum radius of the oxygen-free area under the 1:2 case is R=171 mm, which has little difference with others, while the average temperature peak value is 1 122 ℃, and the average peak value of CO concentration in strong reducing atmosphere is 13.713%, and it is obviously better than other working conditions. The flame length in the flame stroke is 4 473 mm in the flame stroke, and it is better than others, which is conducive to further reducing NOemissions and improving pulverized coal burnout. It can be used as the optimal operating condition of precombustion chamber swirl burner under the operating conditions of 46% load, excess air ratio of 1.63 and inter secondary air swirl number of 1.6.