Low-Load Stable Combustion Technology of 600 MW Supercritical Low-Calorific Value Lignite Octagonal Tangentially Fired Boiler

doi:10.12096/j.2096-4528.pgt.260207

Abstract

Abstract:

Objectives With the high proportion of new energy generation units connected to the power grid, higher requirements are put forward for the deep peak shaving capacity of traditional thermal power units. However, low-calorific value lignite boilers are difficult to burn stably under low-load conditions, so they need to be optimized and adjusted according to the actual situation. Methods By changing the combustion organization to compress the height of the flame center and improve the flame filling degree, combined with optimized operating parameters, stable combustion of the boiler under low-load conditions can be achieved. To predict the stable combustion effect, a comprehensive model of flow, heat transfer, mass transfer and combustion is established to study the combustion characteristics of a 600 MW supercritical low-calorific value lignite octagonal tangentially fired boiler at different loads (from 100% to 35%). Results Through local centralized coal feeding and operating No. 1, 3, 4, 5 and 7 coal mills, the minimum stable combustion load of a 600 MW supercritical octagonal tangentially fired boiler with a moisture content of 50% and a calorific value of 8.85 MJ/kg can reach 35%, and the NO _x concentration at the furnace outlet does not change significantly under various loads. Conclusions Optimizing local centralized coal feeding and coal mill operation modes can solve the problem of difficult stable combustion of low-calorific value lignite boilers under low-load conditions, and improve the deep peak shaving capacity of power plants.

Key words: thermal power units, octagonal tangentially fired boiler, deep peak shaving, low-load stable combustion, numerical simulation, low-calorific value lignite, combustion characteristics

CLC Number:

TK 16

Baoqun GUO, Jiahao YUE, Maozhan CONG, Hongpeng LIU, Baizhong SUN. Low-Load Stable Combustion Technology of 600 MW Supercritical Low-Calorific Value Lignite Octagonal Tangentially Fired Boiler[J]. Power Generation Technology, 2026, 47(2): 295-303.

Figures/Tables 17

Fig. 1 Geometric model of boiler and schematic diagram of burner layout

Tab. 1 Fuel characteristics

参数	数值
收到基碳质量分数C_ar/%	25.28
收到基氢质量分数H_ar/%	2.22
收到基氧质量分数O_ar/%	9.80
收到基氮质量分数N_ar/%	0.24
收到基硫质量分数S_ar/%	0.26
水分质量分数M_t/%	50.00
收到基灰分质量分数A_ar/%	12.20
干燥无灰基挥发分质量分数V_daf/%	62.88
收到基低位发热量Q_net,ar/(MJ/kg)	8.85

Fig. 2 Schematic diagram of boiler grid division

Tab. 2 Simulated working conditions

参数	100%负荷	75%负荷	50%负荷	35%负荷
煤粉量/(t/h)	584.80	482.75	364.24	262.90
一次风量/(m³/h)	639.34	493.17	399.73	307.46
总二次风量/(m³/h)	1 479.52	1 101.02	875.08	744.69
燃尽风量/(m³/h)	613.98	386.02	311.63	263.81

Tab. 3 Comparison between numerical calculation results and power plant operational results

项目	炉膛出口温度/K	炉膛出口O₂体积分数/%	炉膛出口NO _x 质量浓度/(mg/m³)
误差/%	0.12	2.78	4.07
数值计算	1 177.43	3.5	318.0
电厂运行	1 176.00	3.6	331.5

Fig. 3 Pulverized coal concentration distribution during 35% load operation of boiler before and after optimization

Fig. 4 Temperature distribution during 35% load operation of the boiler before and after optimization

Fig. 5 Velocity distribution of furnace cross-section under different loads

Fig. 6 Temperature distribution of furnace longitudinal section under different loads

Fig. 7 Distribution of furnace temperature with furnace height under different loads

Fig. 8 O2 concentration distribution at the center section of the furnace under different loads

Fig. 9 Distribution of O2 concentration with furnace height under different loads

Fig. 10 CO concentration distribution in furnace section under different loads

Fig. 11 CO concentration distribution with furnace height under different loads

Fig. 12 Distribution of NO x concentration in furnace cross-section under different loads

Fig. 13 Distribution of actual coal NO x concentration with furnace height under different loads

Tab. 4 Results of 35% load stable combustion test of unit

参数	测试结果
电负荷/MW	210
运行O₂体积分数/%	6.2
排烟温度/℃	133.1
排烟CO体积分数/%	0
飞灰可燃物体积分数/%	0.20
底渣可燃物体积分数/%	0.25
修正后排烟温度/℃	139.2
未燃碳热损失/%	0.18
干烟气热损失/%	7.59
CO引起的热损失/%	0
修正后锅炉效率/%	89.84

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