Effects of multiple agglomeration technology on the removal of particulate matters and particulate heavy metals: A pilot study
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摘要: 燃煤颗粒物和其上富集的As、Se、Pb等重金属排入大气后危害环境和人体健康。本研究开发以湍流聚并、壁面回流吸附为原理的复合聚并器，研究了聚并前后对颗粒物和颗粒态重金属的聚并效果。首先采用数值模拟方法综合考虑压力损失、速度均匀性和颗粒物聚并效果，优选了折叶片作为复合聚并器的叶片类型。随后进行了不同流量的颗粒物聚并中试研究，发现复合聚并器对PM1的聚并率可达32.84%，随着流量从11.1 m/s增加到17.6 m/s，PM2.5聚并率呈现一定下降趋势，说明了流量增加导致颗粒停留时间缩短和颗粒物聚并率的下降。通过对比聚并前后颗粒物中As、Se、Pb的浓度变化，发现聚并过程增强了对气态重金属的吸附，也会聚集富含重金属的纳米级颗粒物，从而造成PM1中重金属浓度的增加。聚并后PM1内的As、Se、Pb绝对浓度的降低，显示了复合聚并器对颗粒物和颗粒态重金属的协同脱除效果。Abstract: The emmision of particulate matters and heavy metals such as As, Se and Pb from coal combustion into the atmosphere would cause a serious environmental and human health hazard. Therefore, a multiple agglomeration based on the principle of turbulent coalescence and wall surface adsorption was developed to investigate the agglomeration effects on the removal of particulate matter and particulate heavy metals. Firstly, a numerical simulation method was adopted to comprehensively study the pressure loss, the velocity uniformity and the particle agglomeration effect, and a folded blade was selected for the multiple agglomeration device. Subsequently, a pilot study at a coal-fired plant on the particle agglomeration at different flue gas velocities was carried out. It is found that the agglomeration rate of PM1 in the multiple agglomeration device is up to 32.84%. As the gas velocity is increased from 11.1 to 17.6 m/s, the agglomeration rate of PM2.5 shows a certain decline, indicating that an increase in gas velocity would lead to a shorter residence time of particles and thus a decrease in agglomeration rate of particles. By comparing the concentration changes of As, Se and Pb in the particles before and after agglomeration, it is found that the agglomeration process can enhance the adsorption to gaseous heavy metals and also aggregate the nano-particles rich in heavy metals, thus resulting in an increase in the concentration of heavy metals in PM1. The decrease of the absolute concentrations of As, Se and Pb in PM1 after coalescence shows a cooperative removal effect in the multiple agglomeration device on the particulate matter and particulate heavy metals.
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图 2 流经扰流叶片的复合聚并原理示意图
Figure 2 Multiple agglomeration mechanisms affected by disturbed flow blade
图 4 数值模拟使用的扰流叶片结构参数
Figure 4 Blade type used by the calculation of numerical simulation
图 5 复合聚并器不同叶片的压力损失及出口速度均匀性
Figure 5 Pressure loss and velocity uniformity of different blades in multiple agglomeration device
图 6 复合聚并器不同叶片的颗粒物聚并率
Figure 6 Agglomeration rate of PM10 using different blades in multiple agglomeration device
图 7 聚并前后细颗粒物的微观形貌
Figure 7 Morphology of fine particles before and after agglomeration
图 10 聚并前后总灰中As、Se、Pb浓度
Figure 10 Concentrations of As, Se and Pb in bulk ash before and after agglomeration
图 11 聚并前后PM10中As、Se、Pb含量
Figure 11 Concentrations of As, Se and Pb in PM10 before and after agglomeration
图 12 聚并前后PM1中As、Se、Pb绝对质量浓度
Figure 12 Absolute concentrations of As, Se and Pb in PM1 before and after agglomeration
表 1 机组燃用煤种的元素分析和工业分析
Table 1 Proximate and ultimate analysis of coal
Ultimate analysis wdaf/% Proximate analysis wad/% C H N S O* M V A FC 59.9 3.8 1.1 0.6 34.6 4.4 41.6 22.6 31.3 *: by difference 
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表 2 不同烟气流量下复合聚并器对颗粒物的聚并效率
Table 2 Agglomeration rates of PM1 and PM2.5 at different flue gas velocities
Pilot study 11.1 m/s 13.4 m/s 17.6 m/s Agglomeration rate of PM1/% 28.40 32.84 13.56 Agglomeration rate of PM2.5/% 26.06 20.66 18.79 Simulation 10 m/s 14 m/s 18 m/s Agglomeration rate of PM1/% 32.29 26.41 24.59 Agglomeration rate of PM2.5/% 8.14 6.43 5.29
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