29 MW高速煤粉燃烧器稳燃机理

Stable mechanism of 29 MW high speed pulverized coal burner

煤粉工业锅炉广泛应用于市政热力和工业园区,具有快速启停和调节负荷的优势。为了提高煤粉工业锅炉经济性,降低燃料成本,需要提高煤粉工业锅炉的燃料适应性。高速煤粉燃烧器作为煤粉工业锅炉的核心设备,目前其稳燃性能的研究主要围绕工业试验开展。以29 MW高速煤粉燃烧器为研究对象,研究其稳燃机理,首先对电站锅炉燃烧器着火热公式进行修正,获得适合于煤粉工业的着火热计算公式,计算7种负荷下的一次风煤粉气流着火热;其次采用数值模拟的方法分析6种工况下回流区变化情况并使用掺混系数分析高速煤粉燃烧器额定负荷燃烧混煤(工况f)时回流区边界上一次风和二次风混合情况;最后分析配置高速煤粉燃烧器的40 t/h蒸汽锅炉使用混煤和神府烟煤燃烧效果。研究结果表明,高速煤粉燃烧器一次风煤粉气流着火热随着负荷的提高而提高,当负荷从35%提高到100%,使用神府烟煤和混煤的着火热分别为450~850 kW和650~1300 kW;高速煤粉燃烧器回流区大小与负荷变化关系不大,高负荷下燃烧器内的稳燃压力大于低负荷,55%和75%负荷时回流区靠近一次风管回流帽;随一次风逆喷距离与一次风管内径比(L/d)增加,工况f回流区边界掺混系数由负值逐渐增加到正值,说明高温烟气能够及时进入回流区,促进一次风气流加热升温,同时在回流区末端烟气流出边界,与二次风汇合,形成滞止区,生成值班火焰;工业试验表明锅炉中低负荷下燃用混煤能够稳定着火并燃烧,当二次风量超过20000 Nm/h时燃烧不稳定,因为值班火焰被冷风逐渐吹灭,燃烧器内稳燃循环被打破。

The pulverized coal industrial boiler is widely used in municipal heating and industrial parks because of its quick firing and loading.In order to improve its economic performance and reduce the fuel cost,it is necessary to improve the fuel adaptability of pulverized coal industrial boiler.High-speed pulverized coal burner is the key equipment of pulverized coal industrial boiler.The stable burning mechanism of 29 MW high-speed pulverized coal burner is investigated in this study.Firstly,the ignition heat formula of power plant boiler burner is modified and the pulverized coal industrial boiler ignition heat formula is obtained.The ignition heat under seven kinds of loadings is calculated.Secondly,a numerical simulation is used to analyze the variation of the recirculation zone under six working conditions and the mixing coefficient is used to analyze the mixing of primary and secondary air at the boundary of the recirculation zone at working condition f.Finally,the combustion characteristic of 40 t/h steam boiler using mixed coal and Shenfu bituminous coal equipped with high-speed pulverized coal burner is analyzed.The research results show that the ignition heat of primary air pulverized coal in high-speed pulverized coal burner increases with the load.When the load increases from 35%to 100%,the ignition heat of Shenfu bituminous coal and mixed coal are 450-850 kW and 650-1300 kW respectively.The size of the recirculation area of the high-speed pulverized coal burner has little change with the load.The tension of stable combustion in the burner under high load is greater than that under the low load.The recirculation area is close to the cap of the primary air duct when the load is 55%and 75%.At the working condition f,the boundary mixing coefficient of the recirculation zone gradually increases from negative value to positive value with the increase of L/d.This indicates that the high temperature flue gas can enter the recirculation zone in time to heat the primary air flow,the flue can go out and mix with the second air at the end of the recirculation zone.At the same time,it forms a stagnation zone and generate orderly flame.Industrial tests show that the burner could fire smoothly under low loads when the mixed coal is used and it will be unstable when the secondary air volume exceeds 20000 Nm~3/h.This is because the orderly flame at the stagnation area in the burner is gradually blown out by cold air and the steady combustion cycle in the burner is broken.