高频交变电场中荷电细颗粒物凝聚的实验及模拟研究
发布时间：2019-03-31 10:58
【摘要】：由于常规的除尘装置对细颗粒物的脱除效率并不理想,多种凝聚技术应运而生。其中,荷电细颗粒物在交变电场中的凝聚技术得到了全世界科学研究者的广泛关注。早期,交变电凝聚的实验研究多在低频交变电场中进行。针对荷电细颗粒物在高频交变电场中的电凝聚而言,由于其理论基础尚不成熟,很少见到相应的研究报道。通过Indigo电凝聚器以及Cosa/Tron电凝聚器的工业应用发现,高频交变电凝聚相较于低频电凝聚不仅能耗低而且凝聚效率更加优越。鉴于此,本文开展了高频交变电场中荷电细颗粒物凝聚的实验和理论分析等工作。高频交变电场荷电细颗粒物凝聚的机理主要从两方面进行分析:直流电场中颗粒物荷电机理的研究以及交变电场中荷电细颗粒物凝聚机理的研究。直流电场中颗粒物荷电机理分为场致荷电和扩散荷电两种。0.3μm、0.5μm以及1.0μm三种粒径的细颗粒物荷电方式主要是场致荷电。交变电场中荷电细颗粒物凝聚机理研究的核心是确定电凝聚系数的大小。利用高频交变电场中荷电细颗粒物的凝聚机理,推导出了高频交变电场中荷电细颗粒物的凝聚系数Kg。在实验研究方面,搭建了高频交变电场凝聚实验台。并针对荷电电压对凝聚效率的影响、高频交变电源性质对凝聚效率的影响、气溶胶性质对凝聚效率的影响三个方面分别进行了实验研究。研究表明:采用空气中的细颗粒物作为颗粒源进行的高频交变电凝聚实验研究效率明显;对0.3μm、0.5μm以及1.0μm粒径的细颗粒物而言,最高凝聚效率分别可达65%、62%、55%;气溶胶颗粒物的饱和荷电量qmax并不是随着荷电电压值增加而无限增大,当荷电电压达到上限电压时,气溶胶颗粒物饱和荷电量不再增加;荷电电压的增加,可以使细颗粒物的电凝聚效率增加,并且当荷电电压U115kV时,荷电量达到最大值,电凝聚效率趋于平缓;在相同荷电电压的情况下,随着污染程度的增加,总凝聚效率减少;高频交变电的电压对总凝聚效率影响不大;影响高频交变电凝聚的主要因素是电源频率,频率的增加,凝聚效率增加;实验通道内的平均气流速度越大,即细颗粒物的停留时间越少,总凝聚效率下降;随着气溶胶湿度的增加,不同粒径的细颗粒物的凝聚效率皆有降低的趋势,并且相对湿度对小粒径细颗粒物凝聚效率的影响要高于大粒径细颗粒物;燃香细颗粒物与空气细颗粒物的凝聚效率趋势一致,但是在相同荷电电压下燃香细颗粒物的凝聚效率明显低于空气细颗粒物。利用FLUENT中的离散项模型(DPM)与群体平衡模型(PBM)分别对高频交变电场中荷电细颗粒物的运动轨迹与凝聚效率进行了数值模拟,并对模拟结果进行了分析。用CFD与PBM相耦合的方法成功模拟出了颗粒物凝聚效率。同时,将模拟值与实验值相对比,验证了高频交变电场中荷电细颗粒物的凝聚系数Kg的正确性。
[Abstract]:Because the removal efficiency of fine particulate matter by conventional dedusting device is not ideal, many kinds of coagulation technology emerge as the times require. Among them, the coagulation technology of charged fine particles in alternating electric field has been paid more and more attention by scientific researchers all over the world. In the early stage, the experimental study of alternating electrocoagulation was mostly carried out in low frequency alternating electric field. For the electrocoagulation of fine charged particles in high frequency alternating electric field, due to its immature theoretical basis, few studies have been reported. Through the industrial application of Indigo electrocoagulator and Cosa/Tron electrocoagulator, it is found that the high frequency alternating electrocoagulation is superior to the low frequency electrocoagulation not only in energy consumption but also in the condensation efficiency. In view of this, experiments and theoretical analysis of fine charged particles in high frequency alternating electric field have been carried out in this paper. The coagulation mechanism of charged fine particles in high frequency alternating electric field is analyzed from two aspects: the mechanism of charged particles in DC electric field and the coagulation mechanism of charged fine particles in alternating electric field. The charge mechanism of particulate matter in DC electric field is divided into two types: field-induced charge and diffusion charge. Three kinds of fine particles, 0.3 渭 m, 0.5 渭 m and 1.0 渭 m, are mainly field-induced. The core of the study on the coagulation mechanism of charged fine particles in alternating electric field is to determine the size of electrocoagulation coefficient. Based on the coagulation mechanism of fine charged particles in high frequency alternating electric field, the coacervation coefficient Kg. of charged fine particles in high frequency alternating electric field is derived. In the aspect of experimental research, a high frequency alternating electric field coagulation experimental platform is built. The effects of charge voltage on coagulation efficiency, high-frequency alternating power supply and aerosol properties on coagulation efficiency were studied experimentally. The results show that the experimental study efficiency of high frequency alternating electrocoagulation using fine particulate matter in air as particle source is obvious. For fine particles with the diameters of 0.3 渭 m, 0.5 渭 m and 1.0 渭 m, the highest coagulation efficiency can reach 65%, 62% and 55%, respectively, for fine particles with a particle size of 0.3 渭 m, 0.5 渭 m and 1.0 渭 m. The saturation charge of aerosol particles (qmax) does not increase infinitely with the increase of charge voltage. When the charge voltage reaches the upper voltage, the saturation charge of aerosol particles no longer increases. With the increase of charge voltage, the electrocoagulation efficiency of fine particles can be increased, and when the charge voltage is U115kV, the electric charge reaches the maximum value, and the electrocoagulation efficiency tends to smooth. Under the same charge voltage, the total coagulation efficiency decreases with the increase of pollution level, and the voltage of high frequency alternating current has little effect on the total condensation efficiency. The main factors influencing high frequency alternating electrocoagulation are the frequency of power supply, the increase of frequency and the increase of condensation efficiency, and the larger the average airflow velocity in the experimental channel, the less the residence time of fine particles, and the decrease of the total condensation efficiency. With the increase of aerosol humidity, the aggregation efficiency of fine particles with different particle sizes decreased, and the effect of relative humidity on the aggregation efficiency of small particles and fine particles was higher than that of large particles and fine particles. The coacervation efficiency of incense-burning fine particles is similar to that of air fine particles, but under the same charge voltage, the condensation efficiency of incense-burning fine particles is obviously lower than that of air fine particles. Based on the discrete term model (DPM) in FLUENT and the population equilibrium model (PBM), the trajectory and condensation efficiency of fine charged particles in high frequency alternating electric field are numerically simulated, and the simulation results are analyzed. The coagulation efficiency of particulate matter was successfully simulated by the coupling method of CFD and PBM. At the same time, the simulation value is compared with the experimental value to verify the correctness of the coacervation coefficient (Kg) of fine charged particles in high frequency alternating electric field.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701.2
本文编号：2450842
[Abstract]:Because the removal efficiency of fine particulate matter by conventional dedusting device is not ideal, many kinds of coagulation technology emerge as the times require. Among them, the coagulation technology of charged fine particles in alternating electric field has been paid more and more attention by scientific researchers all over the world. In the early stage, the experimental study of alternating electrocoagulation was mostly carried out in low frequency alternating electric field. For the electrocoagulation of fine charged particles in high frequency alternating electric field, due to its immature theoretical basis, few studies have been reported. Through the industrial application of Indigo electrocoagulator and Cosa/Tron electrocoagulator, it is found that the high frequency alternating electrocoagulation is superior to the low frequency electrocoagulation not only in energy consumption but also in the condensation efficiency. In view of this, experiments and theoretical analysis of fine charged particles in high frequency alternating electric field have been carried out in this paper. The coagulation mechanism of charged fine particles in high frequency alternating electric field is analyzed from two aspects: the mechanism of charged particles in DC electric field and the coagulation mechanism of charged fine particles in alternating electric field. The charge mechanism of particulate matter in DC electric field is divided into two types: field-induced charge and diffusion charge. Three kinds of fine particles, 0.3 渭 m, 0.5 渭 m and 1.0 渭 m, are mainly field-induced. The core of the study on the coagulation mechanism of charged fine particles in alternating electric field is to determine the size of electrocoagulation coefficient. Based on the coagulation mechanism of fine charged particles in high frequency alternating electric field, the coacervation coefficient Kg. of charged fine particles in high frequency alternating electric field is derived. In the aspect of experimental research, a high frequency alternating electric field coagulation experimental platform is built. The effects of charge voltage on coagulation efficiency, high-frequency alternating power supply and aerosol properties on coagulation efficiency were studied experimentally. The results show that the experimental study efficiency of high frequency alternating electrocoagulation using fine particulate matter in air as particle source is obvious. For fine particles with the diameters of 0.3 渭 m, 0.5 渭 m and 1.0 渭 m, the highest coagulation efficiency can reach 65%, 62% and 55%, respectively, for fine particles with a particle size of 0.3 渭 m, 0.5 渭 m and 1.0 渭 m. The saturation charge of aerosol particles (qmax) does not increase infinitely with the increase of charge voltage. When the charge voltage reaches the upper voltage, the saturation charge of aerosol particles no longer increases. With the increase of charge voltage, the electrocoagulation efficiency of fine particles can be increased, and when the charge voltage is U115kV, the electric charge reaches the maximum value, and the electrocoagulation efficiency tends to smooth. Under the same charge voltage, the total coagulation efficiency decreases with the increase of pollution level, and the voltage of high frequency alternating current has little effect on the total condensation efficiency. The main factors influencing high frequency alternating electrocoagulation are the frequency of power supply, the increase of frequency and the increase of condensation efficiency, and the larger the average airflow velocity in the experimental channel, the less the residence time of fine particles, and the decrease of the total condensation efficiency. With the increase of aerosol humidity, the aggregation efficiency of fine particles with different particle sizes decreased, and the effect of relative humidity on the aggregation efficiency of small particles and fine particles was higher than that of large particles and fine particles. The coacervation efficiency of incense-burning fine particles is similar to that of air fine particles, but under the same charge voltage, the condensation efficiency of incense-burning fine particles is obviously lower than that of air fine particles. Based on the discrete term model (DPM) in FLUENT and the population equilibrium model (PBM), the trajectory and condensation efficiency of fine charged particles in high frequency alternating electric field are numerically simulated, and the simulation results are analyzed. The coagulation efficiency of particulate matter was successfully simulated by the coupling method of CFD and PBM. At the same time, the simulation value is compared with the experimental value to verify the correctness of the coacervation coefficient (Kg) of fine charged particles in high frequency alternating electric field.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701.2
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