多通道逆喷旋流煤粉燃烧特性及NO_(x)排放试验研究

Expevimental stady on pulverzed coal combustion characteristics and NO_(x) emission of multichannel reverse-jet suirl burner

煤粉燃烧器是煤粉工业锅炉核心技术,也是实现煤炭在工业锅炉领域清洁高效利用的关键。为探究14 MW多通道逆喷旋流煤粉燃烧器的燃烧特性及NO_(x)排放特性,基于热态台架试验及14 MW煤粉工业锅炉工业试验,采用高温热电偶、烟气分析仪、高速工业摄像机和飞灰收集装置对预燃室内温度分布、组分浓度分布以及预燃室外火焰形态和尺寸、炉尾NO_(x)排放浓度和飞灰发热量进行测量,定量表征了该燃烧器的燃烧特性、火焰特性及NO_(x)排放特性。试验结果表明:(1)燃烧特性方面,逆向射流、旋转射流及预燃室技术的耦合,在预燃室内初级火焰区创造了高温(>1 200℃)、低氧(<1%)、高质量浓度CO(>50 000 mg/L)和低质量浓度NO_(x)(<300 mg/Nm~3)的强还原区,实现了煤粉在预燃室内的低氮、稳燃。紧贴预燃室壁面的直流外二次风形成了低于440℃的低温区域,其对于降低预燃室壁面温度、壁面高温腐蚀具有重要作用。(2)火焰特性方面,预燃室外燃烧火焰长度约为2 680 mm,火焰直径接近770 mm,火焰发散角为27.97°,火焰形态稳定、色泽明亮且具有一定的旋转刚性。火焰锋面上存在明显的褶皱,表明火焰锋面上的热质交换较为强烈,燃烧强度较为剧烈。(3)NO_(x)排放特性及燃尽特性方面,炉尾NO_(x)初始排放质量浓度为384 mg/Nm^(3)(O_(2)质量分数为9%条件下),再结合SNCR技术可将NO_(x)排放质量浓度降至164 mg/Nm~3(O_(2)质量分数为9%条件下),而此时炉尾飞灰低位发热量仅为540 k J/kg,计算得煤粉燃烧效率约为97.92%,具备低氮、高效的燃烧特性。

As a core component in pulverized coal boiler,the burner plays a key role for clean and efficient combustion realization.To study combustion characteristic and NO_(x) emission of 14 MW multichannel reverse-jet swirl burner of industrial pulverized coal boiler,thermal bench and industrial test are performed using high-temperature thermocouple,flue gas analyzer,high-speed cameras and fly ash collecting device.And then,the following parameters are measured,including temperature distribution,concentration of gas components,the flame shape and size,NO_(x) emission concentration and calorific value of furnace tail.The results show that:①In terms of combustion characteris⁃tics,the combination of reverse jet,swirl and pre combustion chamber technology creates a strong reduction zone with high temperature(>1200℃),low oxygen(<1%),high CO(>50000 mg/L)and low NO_(x)(<300 mg/Nm^(3))in the primary flame zone of the pre combustion chamber,which leads to low nitrogen and stable combustion of pulverized coal in the pre combustion chamber.Furthermore,a low tempera⁃ture area with the temperature below 440℃is formed as a result of the outer secondary air jet close to the wall of the pre combustion chamber forms,which helps reduce the wall temperature of the pre combustion chamber and boost the high temperature corrosion of the wall.②In terms of flame characteristics,the flame length outside the pre combustion chamber is approximately 2680 mm,the diameter of the flame nears to 770 mm,and the divergence angle is 27.97°.Overall,the flame shape is stable with bright appearance,and exhibits rota⁃tional rigidity to a certain extent.In addition,obvious folds are observed on the flame front,which indicates that the heat and mass ex⁃change on the flame front is more intense,and the combustion intensity is more intense.③In terms of NO_(x) emission characteristics and burnout characteristics,the initial NO_(x) emission concentration of the furnace tail is recorded as 384 mg/Nm3(O_(2) mass fraction is 9%).Combined with SNCR technology,the NO_(x) emission concentration can be reduced to as low as 164 mg/Nm3(O_(2) mass fraction is 9%).Cur⁃rently,the low calorific value of the fly ash of the furnace tail is only 540 kJ/kg and the calculated combustion efficiency of pulverized coal is about 97.92%.Hence,overall,it demonstrates a low nitrogen,high efficiency combustion characteristics.