Experimental research on the control of heavy metal emissions from 330 MW coal-fired unit by heterogeneous agglomeration
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摘要: 湖北某电厂1号机组容量为330 MW，配备双室四电场静电除尘器，为了考察异相凝并技术对细颗粒物以及重金属脱除效率的影响，对1号机组除尘器前后，脱硫塔后进行颗粒物与重金属采样测试。结果表明，在烟道中喷射凝并吸附剂后，ESP入口颗粒态重金属占比增加，其中，Se元素在PM2.5和PM10上增加尤为明显，而气态的重金属含量有所降低，表明凝并吸附剂增强了颗粒态重金属的凝并效果，小颗粒态与气态重金属通过异相凝并过程转移至大颗粒态。喷入凝并吸附剂后，石膏中重金属含量显著降低，说明能够进入脱硫石膏的重金属含量减少，异相凝并提升了ESP对重金属的脱除作用；在尾部烟道末端烟囱排放口采样点，重金属含量相较于未喷入凝并吸附剂的工况，有着明显的降低，表明了经过异相凝并之后，排放至大气中的重金属显著减少，异相凝并对于重金属的控制起到关键作用。Abstract: In order to investigate the influence of spraying the agglomeration adsorbent on the removal efficiency of fine particles and heavy metals, the sampling and tests on particles and heavy metals were carried out before and after the dedusters and the desulfurization towers in the Unit 1 of a power plant in Hubei Province with a capacity of 330 MW and equipped with a double-chamber four-electric-field electrostatic precipitator. The test results show that after spraying the agglomeration adsorbent in the flue, the proportion of the particulate heavy metals at the ESP inlet increases, the Se element increasing significantly in PM2.5 and PM10, while the heavy metal content in the gas phase decreases, indicating that the agglomeration adsorbent can improve the coagulation efficiency of particulate heavy metals, leading to the small particulate and heavy metals in gas phase being transferred to large particulates. In gypsum, the content of heavy metals is significantly reduced after agglomeration, indicating that heavy metals can join the desulfurized gypsum. Also, the heterogeneous agglomeration enhances the effect of ESP on the removal of heavy metals. At the point before final discharge to the chimney, there is a significant decrease in the content of heavy metals compared with the non-agglomerated condition, which indicates that the heavy metals discharged into the atmosphere after agglomeration are significantly reduced, and the heterogeneous agglomeration plays a key role in the control of heavy metals.
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Key words:
- heterogeneous agglomeration /
- particle /
- heavy metals /
- arsenic /
- selenium /
- lead
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图 10 气态与PM10上重金属质量浓度之和变化
Figure 10 Heavy metal concentration in both PM10 and the flue gas
图 11 WFGD后烟气重金属总质量浓度
Figure 11 Total concentration of heavy metals in flue gas after desulfurization
表 1 煤样的元素分析和工业分析
Table 1 Ultimate analysis and proximate analysis of coal samples
Ultimate analysis w/% Heavy metals content /(μg·g-1) Proximate analysis w/% Qnet, ar /(MJ·kg-1) C H N S O As Se Pb Mt-ar Mad Aar Vdaf 60.2 2.7 0.7 1.5 4.9 4.1 1.8 53.3 8.30 6.9 23.0 16.0 22.6 
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表 2 异相凝并系统参数
Table 2 Parameters for an agglomeration system
Project Unit Parameter Adsorbent supply capacity kg/h 2-4 Dilution water supply capacity kg/h 18000 Compressed air supply capacity m3/min 30 Installed power of agglomeration device kW < 50 Installed power of air compressor kW 180
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表 3 采样参数
Table 3 Sampling parameters
Sampling site Adsorbent Suction volume /L Load/MW Before ESP with 20 300 After ESP with 1045 300 After WFGD with 1230 300 Before ESP without 20 300 After ESP without 1465 300 After WFGD without 1800 300
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表 4 颗粒物采样
Table 4 Particle sampling concentration results in size
Sampling site Adsorbent 2.5-10 μm/(mg·m-3) 1-2.5 μm/(mg·m-3) < 1 μm/(mg·m-3) Before ESP with 31.0 44.0 98.5 Before ESP without 183.5 927.0 102.0 After ESP with 0.49 2.08 1.69 After ESP without 0.07 0.02 3.50
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表 5 固体样中重金属的含量
Table 5 Concentrations of heavy metals in solid samples
Sample w/(μg·g-1) As Se Pb limestone 9.02 3.88 10.43 Slag 0.37 0.11 15.09 ESP fly ash without adsorbent 18.80 8.09 234.01 ESP fly ash with adsorbent 19.53 9.19 243.96 Gypsum without adsorbent 11.10 6.76 15.56 Gypsum with adsorbent 7.52 2.19 10.89
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表 6 脱硫废水中重金属的含量
Table 6 Concentrations of heavy metals in a desulfurization wastewater
Sample w/(μg·g-1) As Se Pb Desulfurization wastewater 0.85 1.64 0.13
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表 7 各元素质量平衡率
Table 7 Mass balance rate for each element
Adsorbent MBR /% As Se Pb With 97.45 103.82 90.88 Without 96.11 98.87 87.45
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表 8 各元素在各产物中的富集
Table 8 The enrichment of each element in each product
Adsorbent element With /% Without /% As Se Pb As Se Pb Fly ash 95.13 96.45 98.38 92.87 89.21 98.07 Slag 0.32 0.20 1.07 0.33 0.21 1.12 Gypsum 4.53 2.84 0.54 6.79 9.23 0.81 Desulfurization wastewater 0.70 2.93 0.01 0.71 3.07 0.01 Air 0.01 0.47 0.01 0.01 1.32 0.01
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