發(fā)布時間：2019-03-31 10:58

【摘要】：由于常規(guī)的除塵裝置對細(xì)顆粒物的脫除效率并不理想,多種凝聚技術(shù)應(yīng)運而生。其中,荷電細(xì)顆粒物在交變電場中的凝聚技術(shù)得到了全世界科學(xué)研究者的廣泛關(guān)注。早期,交變電凝聚的實驗研究多在低頻交變電場中進行。針對荷電細(xì)顆粒物在高頻交變電場中的電凝聚而言,由于其理論基礎(chǔ)尚不成熟,很少見到相應(yīng)的研究報道。通過Indigo電凝聚器以及Cosa/Tron電凝聚器的工業(yè)應(yīng)用發(fā)現(xiàn),高頻交變電凝聚相較于低頻電凝聚不僅能耗低而且凝聚效率更加優(yōu)越。鑒于此,本文開展了高頻交變電場中荷電細(xì)顆粒物凝聚的實驗和理論分析等工作。高頻交變電場荷電細(xì)顆粒物凝聚的機理主要從兩方面進行分析:直流電場中顆粒物荷電機理的研究以及交變電場中荷電細(xì)顆粒物凝聚機理的研究。直流電場中顆粒物荷電機理分為場致荷電和擴散荷電兩種。0.3μm、0.5μm以及1.0μm三種粒徑的細(xì)顆粒物荷電方式主要是場致荷電。交變電場中荷電細(xì)顆粒物凝聚機理研究的核心是確定電凝聚系數(shù)的大小。利用高頻交變電場中荷電細(xì)顆粒物的凝聚機理,推導(dǎo)出了高頻交變電場中荷電細(xì)顆粒物的凝聚系數(shù)Kg。在實驗研究方面,搭建了高頻交變電場凝聚實驗臺。并針對荷電電壓對凝聚效率的影響、高頻交變電源性質(zhì)對凝聚效率的影響、氣溶膠性質(zhì)對凝聚效率的影響三個方面分別進行了實驗研究。研究表明:采用空氣中的細(xì)顆粒物作為顆粒源進行的高頻交變電凝聚實驗研究效率明顯;對0.3μm、0.5μm以及1.0μm粒徑的細(xì)顆粒物而言,最高凝聚效率分別可達65%、62%、55%;氣溶膠顆粒物的飽和荷電量qmax并不是隨著荷電電壓值增加而無限增大,當(dāng)荷電電壓達到上限電壓時,氣溶膠顆粒物飽和荷電量不再增加;荷電電壓的增加,可以使細(xì)顆粒物的電凝聚效率增加,并且當(dāng)荷電電壓U115kV時,荷電量達到最大值,電凝聚效率趨于平緩;在相同荷電電壓的情況下,隨著污染程度的增加,總凝聚效率減少;高頻交變電的電壓對總凝聚效率影響不大;影響高頻交變電凝聚的主要因素是電源頻率,頻率的增加,凝聚效率增加;實驗通道內(nèi)的平均氣流速度越大,即細(xì)顆粒物的停留時間越少,總凝聚效率下降;隨著氣溶膠濕度的增加,不同粒徑的細(xì)顆粒物的凝聚效率皆有降低的趨勢,并且相對濕度對小粒徑細(xì)顆粒物凝聚效率的影響要高于大粒徑細(xì)顆粒物;燃香細(xì)顆粒物與空氣細(xì)顆粒物的凝聚效率趨勢一致,但是在相同荷電電壓下燃香細(xì)顆粒物的凝聚效率明顯低于空氣細(xì)顆粒物。利用FLUENT中的離散項模型(DPM)與群體平衡模型(PBM)分別對高頻交變電場中荷電細(xì)顆粒物的運動軌跡與凝聚效率進行了數(shù)值模擬,并對模擬結(jié)果進行了分析。用CFD與PBM相耦合的方法成功模擬出了顆粒物凝聚效率。同時,將模擬值與實驗值相對比,驗證了高頻交變電場中荷電細(xì)顆粒物的凝聚系數(shù)Kg的正確性。
[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.
【學(xué)位授予單位】：北京建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X701.2

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