本文關(guān)鍵詞： 靜電除塵 微細顆粒 受力 水膜 換熱 多場協(xié)同 運動特性　出處：《山東大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：微細顆粒質(zhì)量輕、顆粒小、跟隨性好、吸附性強且較難脫除,是造成大氣能見度降低、灰霾天氣等問題的重要因素,由其引發(fā)的污染已成為我國突出的大氣環(huán)境問題。現(xiàn)有燃煤電廠大多采用靜電除塵器進行除塵處理,其對粒徑10μm以上的顆粒除塵效率高達99%以上,但對微細顆粒(粒徑小于10μm)的脫除效率并不理想。研究表明,將電場、溫度場和濕/濃度場的綜合作用應(yīng)用于靜電除塵器中可以有效提高微細顆粒的脫除效率,但是在流場、電場、溫度場、濕度場及濃度場各自及協(xié)同作用下,靜電場中微細顆粒的濃度分布狀況及運動特性的相關(guān)研究較少,本文通過ELPI在線測試與數(shù)值模擬方法,考察了場協(xié)同作用下顆粒在靜電除塵器內(nèi)部的顆粒總濃度分布、沿程顆粒分級濃度分布、沿程分級濃度減少率、顆粒運動軌跡、沉積效率等,深入研究靜電除塵器內(nèi)部顆粒分布與運動特性等內(nèi)在物理過程,為提高微細顆粒脫除效率提供理論基礎(chǔ)。對靜電除塵器內(nèi)顆粒受力類型、大小和方向進行總結(jié)分析,并將這些力在靜電除塵器內(nèi)部的不同區(qū)域(極線區(qū)、主流區(qū)、近壁區(qū)和壁面上)、不同的工況(原始狀態(tài)、干式狀態(tài)、濕式狀態(tài)、換熱狀態(tài)和協(xié)同狀態(tài))下進行分類,通過已知的參數(shù)對這些力進行量級分析,基于受力類型、大小、方向和量級分析對靜電除塵器內(nèi)部顆粒的力學(xué)行為進行建模,分別建立了微細顆粒趨于壁面運動的運動模型和微細顆粒與收塵極板之間的粘結(jié)模型。搭建了基于靜電除塵的多場協(xié)同脫除微細顆粒試驗臺,通過測試不同狀態(tài)下除塵器內(nèi)部溫濕度場的分布,進一步分析微細顆粒在除塵器內(nèi)部多場協(xié)同作用下的分布與運動特性。基于ELPI在線測試分析的方法,對微細顆粒的分布狀態(tài)及運動特性進行試驗研究,分別對比研究了不同狀態(tài)下橫截面上的顆�？倽舛确植家�(guī)律,沿程顆粒分級濃度變化規(guī)律以及沿程分級濃度減少率,得到以下結(jié)論:(1)干式狀態(tài)下,截面中與極線平行的位置處顆粒的匯集程度最高;壁面換熱后,高濃度區(qū)隨著氣流的發(fā)展向壁面方向移動,且返混現(xiàn)象減緩;壁面布水后,近壁區(qū)出現(xiàn)低濃度區(qū),且隨著氣流的發(fā)展面積增大,返混現(xiàn)象消失;協(xié)同狀態(tài)下,場協(xié)同效果均優(yōu)于以上場疊加效果,近壁區(qū)濃度梯度較濕式狀態(tài)下更高,近壁區(qū)低濃度區(qū)更明顯。(2)干式狀態(tài)下,粒徑0.04～0.6μm范圍內(nèi)的顆粒的收塵效果不佳,出現(xiàn)返混現(xiàn)象。壁面換熱后,0.4～0.6μm范圍內(nèi)的顆粒返混現(xiàn)象消失,近壁區(qū)顆粒濃度大幅度增加。壁面布水后,0.1～1μm范圍內(nèi)的顆粒濃度大幅度的降低,近壁區(qū)最多降低30%左右。協(xié)同狀態(tài),與濕式狀態(tài)下顆粒的沿程數(shù)濃度變化曲線相似,但整個粒徑范圍內(nèi)顆粒的濃度均有所下降,0.1～1μm范圍內(nèi)的顆粒沿程最多降低了 50%左右。(3)干式狀態(tài),電壓升高對粒徑大于或者小于0.3μm顆粒有明顯的脫除效果,沿程分級濃度減少率升高了 20%～50%左右。壁面換熱后,粒徑0.01μμm的顆粒的減少率有30%的提高,而其他粒徑范圍內(nèi)的顆粒的減少率提高幅度相對略低,10%左右。壁面布水后,液橋力造成小顆粒團聚后數(shù)目減少,同時較大粒徑的顆粒的數(shù)目增多,在近壁區(qū)更明顯,變化幅度更大。協(xié)同狀態(tài)下,多場協(xié)同使整個粒徑范圍內(nèi)的顆粒的濃度減少率均有所提高。與濕式狀態(tài)相比,粒徑大于1μm的顆粒的濃度減少率的提高更明顯,10%左右,近壁區(qū)0.1～1μm范圍內(nèi)的顆粒的效果最明顯,沿程最多降低了 15%左右。綜合考慮流場模型、電暈電場模型、顆粒運動模型、顆粒荷電模型、壁面換熱模型和水膜蒸發(fā)擴散模型,采用COMSOL對不同狀態(tài)下微細顆粒的分布狀況及運動特性進行數(shù)值模擬研究,對電場分布狀況、溫濕度變化,顆粒軌跡、沿程濃度分布狀況以及沿程效率分布狀況做詳細的分析,建立多場協(xié)同下微細顆粒分布與運動特性數(shù)值模型,得到以下結(jié)論:電場強度和顆粒飽和荷電量的分布均以芒刺線為對稱軸呈現(xiàn)軸對稱形式,極線區(qū)的電場強度和顆粒飽和荷電量最強,隨著電壓的升高,芒刺尖端的電場強度增大,顆粒的飽和荷電量也逐漸增大;不同狀態(tài)下,數(shù)值模擬計算得到的溫濕度變化趨勢、沿程濃度分布狀況及沿程沉積效率分布與試驗結(jié)果符合良好,模型可以準確描述溫度、濕度、濃度分布;微細顆粒在電場中運動時有向收塵極板偏移的趨勢,隨著電壓的升高,顆粒的偏移程度加強,顆粒的沉積位置逐漸前移且沉積量逐漸增加,在換熱/換熱/協(xié)同狀態(tài)下,與干式狀態(tài)相比,顆粒的沉積位置逐漸前移且沉積量逐漸增加。綜合以上理論分析、試驗和模擬結(jié)果,對不同狀態(tài)下微細顆粒的受力變化及力學(xué)行為進行總結(jié),揭示了微細顆粒物在流場、顆粒場、電場、溫度場、濕度場、濃度場及其耦合作用下的力學(xué)行為和受力模型,分析了電場/壁面換熱/壁面水膜/協(xié)同作用引起的靜電除塵器內(nèi)部顆粒的受力類型及其變化,建立不同狀態(tài)下微細顆粒的受力模型并確定微細顆粒的量級大小,繪制了在電場/換熱/水膜/協(xié)同作用下靜電除塵器內(nèi)部的顆粒的基本運動情況圖。
[Abstract]:Fine particles of light weight, small particles, with good adsorption ability and is difficult to be removed, is caused by the atmospheric visibility, the important factors of haze weather problems, caused by air pollution has become a prominent environmental problem in China. Most of the existing coal-fired power plants by electrostatic precipitator dust treatment, the grain the size of more than 10 m particle removal efficiency reaches more than 99%, but the fine particles (particle size less than 10 mu m) the removal efficiency is not ideal. The results show that the electric field, temperature field and concentration field of wet / comprehensive effect used in electrostatic precipitator can effectively improve the removal efficiency of fine particles, but in the flow field, electric field, temperature field, humidity field and concentration field and their synergistic effect, research concentration distribution and movement characteristics of fine particles in electrostatic field less, through the test and the number of online ELPI value simulation method, investigation The field synergy particles under the action of particles in the interior of the electrostatic precipitator concentration distribution along the particle concentration distribution along the hierarchical classification, concentration reduction rate, particle trajectory, deposition efficiency, particle size distribution of electrostatic precipitator and the internal movement characteristic of the inner physical process of in-depth, in order to improve the removal efficiency of fine particles and provide a theoretical basis for the force on the particle. The type of electrostatic precipitator, summarized and analyzed the size and direction, and the force of different regions in the internal electrostatic precipitator (polar region, the main region, the area near the wall and the wall surface), different conditions (original state, dry state, wet state, heat transfer and the state under the collaborative state) classification, magnitude analysis to these forces by the known parameters, the size of the force type, based on the direction and magnitude of the mechanical behavior analysis of particles inside the electrostatic precipitator for modeling, are established. The bonding model between fine particles tend to fine particle motion model and wall motion and collecting plate. To build a multi field collaborative electrostatic dust removal of fine particles by test bench based on distribution test under different conditions of temperature and humidity inside the collector field, further analysis of the distribution in the ESP internal field under the synergistic action and the motion characteristics of micro fine particles. Analysis method of ELPI online test based on the experimental study of distribution and movement characteristics of fine particles, were studied the total particle concentration distribution law of cross section under different conditions on the particle concentration variation along the classification and grading along the concentration reduction rate, obtained the following conclusions: (1) dry state, aggregation degree of position in parallel grain section and pole top; wall heat transfer, the high concentration area with the development of the wall surface to air movement, and 榪旀販鐜拌薄鍑忕紦;澹侀潰甯冩按鍚，

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