Study on mercury emission characteristics of circulating fluidized bed boiler and pulverized coal boiler
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摘要: 选取600 MW循环流化床锅炉及1000 MW煤粉炉的电厂进行汞迁移转化及排放特性研究,采用EPA 30B法对烟气汞质量浓度进行采样,同时采集了入炉煤、飞灰、底渣、石灰石、工艺水、脱硫石膏、脱硫废水等固体液体样品进行对比分析。研究了两电厂现有污染物控制装置对汞的协同脱除作用,分析了汞的迁移转化规律。两电厂烟气经过污染物控制装置后,总汞脱除率均达到88%以上,最终排放烟气汞质量浓度分别为1.85和1.10 μg/m3,明显低于中国现行排放标准要求,在现有设备条件下即可实现汞的达标排放。Abstract: A 600 MW circulating fluidized bed boiler power plant and a 1000 MW pulverized coal boiler power plant were selected to study mercury migration, transformation and emission characteristics. The mercury concentration in flue gas was sampled by EPA 30B method, and the solid and liquid samples such as furnace-incoming coal, fly ash, bottom slag, limestone, process water, desulfurization gypsum and desulfurization wastewater were collected for analysis. The synergetic effect of existing pollutant control devices on mercury removal in two power plants was studied, and the migration and transformation law of mercury was discussed. After the flue gas of the two power plants passes through APCDs, the total mercury removal rate reaches over 88%, and the final mercury concentrations of the flue gas are 1.85 and 1.10 μg/m3, which are far lower than the national requirements. Under the existing equipment conditions, the ultra-low mercury emission can be realized.
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表 1 CFB及PC电厂煤样煤质分析
Table 1 Coal quality analysis of coal samples in CFB and PC power plants
Coal sample Proximate analysis/% Ultimate analysis /% Mercury content
/(ng·g−1)M A V FC C H O N S CFB 8.91 15.07 25.35 50.67 68.06 4.22 25.82 0.94 0.96 117.40 PC 11.11 17.71 30.57 40.61 68.87 4.71 24.20 1.27 0.95 158.66 表 2 CFB及PC电厂固体液体样汞含量
Table 2 Mercury concentration of solid and liquid samples in CFB and PC power plants
Coal sample w/(μg·kg−1) w/(μg·L−1) coal bottom ash fly ash limestone gypsum water waste water CFB 117.4 ± 5.67 0.58 ± 0.04 455 ± 5.74 15.28 ± 0.28 − 0 − PC 158.66 ± 3.48 27.08 ± 0.85 211.70 ± 2.64 0 429.47 ± 8.41 0 0 表 3 CFB电厂汞平衡计算
Table 3 Calculation of mercury balance in CFB power plant
Sample Mercury input/Mercury output/(mg·h−1) Proportion/% Mercury input coal 22118.16 98.24 limestone 396.67 1.76 water 0 0.00 total 22514.83 100.00 Mercury output tail gas 2742.35 11.64 fly ash 20802.60 88.31 bottom ash 10.94 0.05 total 23555.89 100.00 Mercury mass balance rate 104.62% 表 4 PC电厂汞平衡计算
Table 4 Calculation of mercury balance in PC power plant
Sample Mercury input/Mercury output/(mg·h−1) Proportion/% Mercury input coal 37205.77 100.00 limestone 0 0.00 water 0 0.00 total 37205.77 100.00 Mercury output tail gas 1906.34 4.95 fly ash 29786.19 77.31 gypsum 4294.70 11.15 waste water 0 0.00 bottom ash 2540.10 6.59 total 38527.34 100.00 Mercury mass balance rate 103.55% 表 5 CFB电厂各采样点烟气汞含量
Table 5 Mercury concentration in flue gas at each sampling point of CFB power plant
Furnace outlet ESP outlet WFGD outlet Hg0/(μg·m−3) 2.95 ± 0.32 0.43 ± 0.12 0.82 ± 0.22 Hg2+/(μg·m−3) 1.97 ± 0.22 3.43 ± 0.67 1.03 ± 0.25 HgP/(μg·m−3) 10.56 ± 1.03 − − HgT/(μg·m−3) 15.48 ± 1.57 3.86 ± 0.79 1.85 ± 0.47 表 6 PC电厂各采样点烟气汞含量
Table 6 Mercury concentration in flue gas at each sampling point of PC power plant
Furnace outlet SCR outlet ESP outlet WFGD outlet Hg0/(μg·m−3) 3.90 ± 0.43 0.61 ± 0.13 0.62 ± 0.13 0.47 ± 0.09 Hg2+/(μg·m−3) 0.23 ± 0.09 0.53 ± 0.11 0.57 ± 0.12 0.63 ± 0.13 HgP/(μg·m−3) 5.35 ± 0.57 10.57 ± 1.09 − − HgT/(μg·m−3) 9.48 ± 1.09 11.71 ± 1.33 1.19 ± 0.25 1.10 ± 0.22 -
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