Experimental Study on Wide-Load Low-NO x Combustion Retrofit for Circulating Fluidized Bed Boiler Burning High-Alkali Coal

doi:10.12096/j.2096-4528.pgt.25027

Abstract

Abstract:

Objectives During the operation of a 440 t/h circulating fluidized bed (CFB) boiler burning high-alkali coal in Xinjiang, China, it is found that its NO _x emissions do not meet the standard. Consequently, an experimental study for low-NO _x combustion retrofit is conducted on this boiler. Methods NO _x emissions are reduced through boiler component modifications and operational parameter adjustments. To enhance separator efficiency and thereby lower the average bed temperature of the boiler, the heating surface of the water-cooled wall is appropriately extended, and the inlet velocity of the separator is increased. The secondary air is optimized by adjusting the height of the secondary air nozzles. To create a reducing atmosphere, a flue gas recirculation system is added. Results Through comprehensive transformation measures, the average bed temperature and furnace flue gas temperature of the boiler are significantly reduced, and the O₂ content in the flue gas is effectively decreased. A more uniform temperature field and a reducing atmosphere are created, both of which are conducive to suppressing NO _x formation, thereby reducing NO _x generation and emissions. Conclusions Following the retrofit, ultra-low NO _x emissions (below 40 mg/m³) are achieved under wide-load conditions even without employing selective non-catalytic reduction (SNCR). This retrofit practice holds positive implications and reference value for low-NO _x combustion control in existing CFB boilers.

Key words: pure burning of high-alkali coal, circulating fluidized bed (CFB) boiler, boiler retrofit, low-NO _x combustion, ultra-low emissions, wide load, reducing atmosphere

CLC Number:

TK 22

Hongjian WANG, Yankai HUANG, Xin YU, Dunxi YU. Experimental Study on Wide-Load Low-NO _x Combustion Retrofit for Circulating Fluidized Bed Boiler Burning High-Alkali Coal[J]. Power Generation Technology, 2025, 46(5): 1005-1013.

Figures/Tables 8

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项目	参数	数值
元素分析	收到基碳质量分数C_ar/%	48.43
	收到基氢质量分数H_ar/%	3.30
	收到基氧质量分数O_ar/%	9.70
	收到基氮质量分数N_ar/%	0.31
	收到基全硫质量分数S_t，ar/%	0.47
工业分析	收到基灰分质量分数A_ar/%	17.63
	全水分质量分数M_ar/%	24.60
	干燥无灰基挥发分质量分数V_daf/%	32.45
发热量	收到基低位发热量Q_net，ar/(kJ/kg)	15 178.92
灰熔点	灰变形温度/℃	1 150
	灰软化温度/℃	1 159
	灰流动温度/℃	1 172
灰成分分析	w(SiO₂)/%	44.80
	w(Al₂O₃)/%	8.20
	w(Fe₂O₃)/%	5.60
	w(CaO)/%	9.80
	w(MgO)/%	3.80
	w(Na₂O)/%	2.97
	w(K₂O)/%	1.40
	w(TiO₂)/%	0.10

项目	参数	数值
元素分析	收到基碳质量分数C_ar/%	48.43
	收到基氢质量分数H_ar/%	3.30
	收到基氧质量分数O_ar/%	9.70
	收到基氮质量分数N_ar/%	0.31
	收到基全硫质量分数S_t，ar/%	0.47
工业分析	收到基灰分质量分数A_ar/%	17.63
	全水分质量分数M_ar/%	24.60
	干燥无灰基挥发分质量分数V_daf/%	32.45
发热量	收到基低位发热量Q_net，ar/(kJ/kg)	15 178.92
灰熔点	灰变形温度/℃	1 150
	灰软化温度/℃	1 159
	灰流动温度/℃	1 172
灰成分分析	w(SiO₂)/%	44.80
	w(Al₂O₃)/%	8.20
	w(Fe₂O₃)/%	5.60
	w(CaO)/%	9.80
	w(MgO)/%	3.80
	w(Na₂O)/%	2.97
	w(K₂O)/%	1.40
	w(TiO₂)/%	0.10

参数	数值
水冷屏增加面积/m²	235
屏式过热器增加面积/m²	112
分离器缩口减小宽度/mm	204
上二次风口增加标高/mm	2 000
下二次风口增加标高/mm	1 000

参数	数值
水冷屏增加面积/m²	235
屏式过热器增加面积/m²	112
分离器缩口减小宽度/mm	204
上二次风口增加标高/mm	2 000
下二次风口增加标高/mm	1 000