本文選題：微波冶金爐 + 加熱效率��； 參考：《昆明理工大學》2015年博士論文

【摘要】：微波冶金爐是微波冶金的關鍵設備之一。但長期以來,微波冶金爐的加熱效率問題一直困擾著學術界和工業(yè)界,從而影響該項技術的應用和推廣。許多研究者從調整冶金工藝參數(shù)的角度對此進行了大量的改進。但是研究表明,微波冶金爐的加熱效率與被加熱物料的吸波性能、爐子內襯耐火材料的透波性能以及電磁波的入射角和極化方式密切相關,這些因素以復雜的方式交互影響著微波加熱的效率。因此,要提高微波冶金爐的加熱效率,必須將爐子的內襯、物料和電磁波等作為一個耦合整體來加以考慮。影響微波冶金爐加熱效率的直接因素就是微波能轉化成內熱源的效率問題。而影響微波能轉化成內熱源的本質因素主要包括三個方面：一是被加熱物料的吸波特性；二是電磁波的極化方式和入射角；三是內置爐襯及承載體的透波性能。本研究致力于提高微波冶金爐的加熱效率,提升微波冶金爐的設計水平,針對影響微波加熱效率的上述本質因素,具體研究了典型冶金物料和微波冶金常用耐火材料的物性參數(shù)、幾何尺寸和入射電磁波頻率、極化方式和入射角等因素對被加熱物料吸波效率和耐火材料透波效率的影響問題。具體研究內容如下：(1)為了研究內置爐襯及物料的微波冶金爐電磁熱耦合場的分布情況,根據(jù)多物理場耦合理論,研究了內置爐襯(耐火層、保溫層)和物料的微波諧振腔內電磁場、溫度場的分布,分析了物料以及耐火保溫層在微波加熱過程中溫度熱點以及電磁場的動態(tài)變化情況。研究結果表明：爐襯和物料電磁參數(shù)的變化對電磁場、溫度場的分布有較大影響；微波加熱前期,微波能大都耗散于物料內,爐襯吸收的微波能較少；微波加熱中后期,爐腔溫度較高時,爐襯吸收的微波能多于物料吸收的微波能；高溫時,物料主要靠表層部分吸收微波能,加熱不均勻現(xiàn)象變得明顯；波導饋口處溫度高,微波能損耗大,使得該處的微波穿透深度最小,8000s之后,微波穿透深度小于10 cm。在一般情況下,溫度場的分布與電磁場分布基本一致,即高場強與溫度熱點對應；但是隨著溫度的升高,當材料的復介電常數(shù)變化較大時,電磁場的諧振模式就會發(fā)生跳變。而此時溫度場不能馬上跟隨作相應變化,只能在新的電磁場模式下慢慢地跟隨電磁場的變化,即溫度場的變化滯后于電磁場的變化。(2)針對微波加熱效率嚴重依賴于物料的介電特性的問題,根據(jù)垂直入射電磁波的反射損耗理論,分別針對微波垂直入射三種典型冶金物料(氯化鈉、石英砂、石油焦),分析了含水率、溫度、料層厚度對物料吸波性能的影響規(guī)律。研究結果表明：氯化鈉料層的最佳加熱工藝參數(shù)為溫度60℃,料層厚度0.04m,該結論與文獻中的實驗結果基本一致。不同含水率、溫度下的料層的反射損耗均與料層厚度有關；隨著厚度的增加,反射損耗曲線會出現(xiàn)若干吸波峰,并且吸波峰的位置會隨著溫度和含水率的變化而偏移；在整個微波干燥過程中都取得最大的加熱效率只能存在于偏移值小于八分之一波長時；并給出了典型冶金物料獲得最大吸波性能的厚度范圍。(3)為了探討電磁波入射角及極化方式對微波加熱效率的影響,根據(jù)斜入射電磁波的反射損耗理論,研究了微波斜入射氯化鈉、石英砂和石油焦三種典型冶金物料的反射損耗,分析了微波入射角以及微波極化方式對吸波性能的影響規(guī)律。研究結果表明：微波入射角和極化方式對物料吸收微波的能力有很大影響,在整個微波加熱過程中取得最大的微波吸收效率可以通過改變入射角及極化方式來達到；在水平極化電磁波(TE)下,溫度為20℃,厚度為0.143m的石英砂物料在入射角為8。時取得最大的吸波效率；入射角和極化方式對不同物料吸波性能的影響并無統(tǒng)一的規(guī)律可循,需要根據(jù)物料的具體電磁特性進行計算分析；最后給出了三種冶金物料獲得最大吸波效率的入射角范圍。(4)為提高微波能在耐火材料中的傳輸效率,根據(jù)電磁波的功率透過系數(shù)理論,針對幾種微波冶金常用耐火材料(莫來石陶瓷、氧化鋁陶瓷、二氧化硅陶瓷等),研究了微波頻率、溫度、耐火層厚度對耐火材料透波性能的影響規(guī)律。結果表明：在2.45 GHz頻率下,[0,0.1m]厚度區(qū)間內,20℃～1000℃范圍內二氧化硅陶瓷的透波效率均在70%以上；耐火材料的功率透過系數(shù)曲線隨著耐火層厚度的增加呈波動狀分布,其中存在若干個透波峰；隨著溫度的升高,透波峰位置出現(xiàn)了向較小厚度方向偏移的現(xiàn)象,且隨著材料厚度增加,透波峰偏移值增大；功率透過系數(shù)曲線中透波峰幅值隨著溫度的升高和厚度的增加而減小；最后給出了耐火材料選用原則及厚度優(yōu)選范圍。
[Abstract]:Microwave metallurgical furnace is one of the key equipment of microwave metallurgy. But for a long time, the heating efficiency of the microwave metallurgical furnace has been puzzling the academic and industrial circles, which affects the application and popularization of this technology. Many researchers have made a great deal of improvement on the angle of adjusting metallurgical parameters. However, the research shows that microwave metallurgy is used. The heating efficiency of the furnace is closely related to the wave performance of the heated material, the wave performance of the refractory material and the incidence angle and polarization mode of the electromagnetic wave. These factors interact with the microwave heating efficiency in a complex way. Therefore, to improve the heating efficiency of the microwave metallurgical furnace, the lining, material and electricity of the furnace must be improved. The direct factor affecting the heating efficiency of the microwave metallurgical furnace is the efficiency of the conversion of microwave to the internal heat source. The essential factors affecting the conversion of microwave to internal heat source include three aspects: the first is the absorption characteristic of the heated material; the two is the polarization mode and the entry of the electromagnetic wave. This study is devoted to improving the heating efficiency of the microwave metallurgical furnace and improving the design level of the microwave metallurgical furnace. In view of the essential factors affecting the microwave heating efficiency, the physical parameters, geometry size and entry of the typical metallurgical materials and the microwave metallurgy Refractory materials are studied in this study. Three The influence of electromagnetic wave frequency, polarization mode and incident angle on the absorption efficiency of heated materials and the permeability of refractories is studied. (1) in order to study the distribution of the electromagnetic thermal coupling field of the microwave metallurgical furnace with built-in furnace lining and material, the internal lining (fire resistance) is studied based on the theory of multi physical field coupling. The distribution of the electromagnetic field and temperature field in the microwave resonant cavity of the material, the distribution of the temperature field in the microwave resonant cavity of the material, and the dynamic change of the hot spot and the electromagnetic field in the material and the fire-resistant insulating layer during the microwave heating process. In the pre heating period, the microwave energy is mostly dissipated in the material, and the microwave energy absorbed by the lining is less. In the middle and late stages of the microwave heating, the microwave energy absorbed by the furnace lining is more than the microwave energy absorbed by the material. When the temperature is high, the material mainly absorbs the microwave energy on the surface part, and the heating unevenness becomes obvious; the temperature of the waveguide feed outlet is high and microwave is high. After 8000s, the depth of the microwave penetration is less than 10 cm., and the distribution of the temperature field is basically the same as the distribution of the electromagnetic field, that is, the high field intensity corresponds to the hot spot. The temperature field can only follow the change of the electromagnetic field slowly in the new electromagnetic field mode, that is, the change of the temperature field lags behind the change of the electromagnetic field. (2) the microwave heating efficiency depends heavily on the dielectric properties of the material, and the reflection loss of the vertical incident electromagnetic wave is based on the problem of the dielectric properties of the material. Three typical metallurgical materials (sodium chloride, quartz sand, petroleum coke) are analyzed in theory. The influence of water content, temperature and thickness of material layer on the absorbing properties of materials is analyzed. The results show that the optimum heating parameters of the NaCl layer are temperature 60 C and the thickness of the material 0.04m. The conclusion is with the experimental knot in the literature. The reflection loss of the material layer at different water content is related to the thickness of the material layer. With the increase of the thickness, the reflection loss curve will appear a number of absorption peaks, and the position of the absorption peak will shift with the change of temperature and water content, and the maximum heating efficiency can only be saved during the whole microwave drying process. In order to investigate the influence of the incident angle and polarization of the electromagnetic wave on the microwave heating efficiency, the influence of the incident angle and polarization of the electromagnetic wave on the microwave heating efficiency is given. (3) the microwave oblique incidence of sodium chloride, quartz sand and petroleum coke three are studied in order to investigate the influence of the incidence angle and polarization mode of the electromagnetic wave on the microwave heating efficiency. The influence of microwave incidence angle and microwave polarization mode on the absorption properties of typical metallurgical materials is analyzed. The results show that microwave incidence angle and polarization mode have great influence on the ability of microwave absorption, and the maximum microwave absorption efficiency can be changed into the microwave heating process. In the horizontal polarization electromagnetic wave (TE), the quartz sand materials with the temperature of 20 and the thickness of 0.143m obtain the maximum absorption efficiency when the incident angle is 8.. The influence of the incident angle and polarization mode on the absorbing properties of different materials is not uniform, and the specific electromagnetic properties of the material should be calculated. In the end, the incidence angle range of the maximum absorption efficiency of three metallurgical materials is given. (4) in order to improve the transmission efficiency of microwave energy in the refractory material, according to the theory of the power transmission coefficient of the electromagnetic wave, some microwave metallurgy Refractory materials (mullite ceramics, alumina ceramics, silica ceramics, etc.) are studied. The effect of frequency, temperature and thickness of refractory layer on the permeability of refractories has been studied. The results show that in the 2.45 GHz frequency and within the thickness range of [0,0.1m], the transmittance efficiency of silica ceramics within the range of 20 to 1000 C is above 70%, and the power transmission coefficient curve of the refractories fluctuates with the increase of the thickness of the refractory layer. With the increase of temperature, the displacement of the wave peak is shifted to a smaller thickness. With the increase of the thickness of the material, the displacement of the wave peak is increased, and the peak amplitude of the power transmission coefficient decreases with the increase of temperature and thickness. Finally, the refractory material is selected as the original. And the optimum range of thickness.

【學位授予單位】：昆明理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TF061

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