本文選題：分子結(jié)構(gòu)　切入點：結(jié)晶　出處：《北京化工大學》2015年碩士論文　論文類型：學位論文

【摘要】：氧化鋁工業(yè)赤泥、粉煤灰等是我國主要的高鋁固體廢棄物,它們的占地堆存造成了嚴重的社會和環(huán)境問題。但同時它們也是一種優(yōu)良的非傳統(tǒng)提鋁資源。采用亞熔鹽法處理赤泥、粉煤灰提取氧化鋁的方法,能夠成功達到對其中Al2O3的經(jīng)濟循環(huán)利用,獲取了苛性比較高(大于4)的鋁酸鈉溶液。這種高苛性比的溶液難以采用傳統(tǒng)的只適用于苛性比1.5左右鋁酸鈉溶液的種子分解的方法制備Al(OH)3,但可以使用鋁酸鈉結(jié)晶析出的方法首先降低溶液的苛性比,然后再進行種分分解。目前,在半工業(yè)化實踐中,結(jié)晶過程存在著結(jié)晶時間長、影響因素難以有效控制等問題。針對此問題,中國科學院過程工程研究所提出采用超聲波強化鋁酸鈉溶液結(jié)晶的新方法,結(jié)晶效率大為提升,但強化機理尚不明確。因此,本論文首先通過對比亞熔鹽法處理不同原料獲得的溶出液結(jié)晶過程進行差異研究,獲得了影響其溶液結(jié)晶的關鍵因素,隨后重點研究了超聲波對溶液粘度、濁度等物化性質(zhì)的影響規(guī)律,剖析了結(jié)晶過程中超聲波的強化機理。論文取得如下創(chuàng)新性成果：(1)通過對比不同來源的粉煤灰溶出液在超聲結(jié)晶過程中結(jié)晶效果的不同,發(fā)現(xiàn)溶出液中含量不多的雜質(zhì)硅、鐵等成分會嚴重影響溶液的超聲結(jié)晶效果。實驗中分別對比了不同的硅、鐵濃度以及不同的初始條件(初始堿濃度不同、初始苛性比不同),發(fā)現(xiàn)當硅濃度改變0.5-2g/L,鐵濃度改變0.4g/L時,結(jié)晶率將大大降低。(2)系統(tǒng)研究了鋁酸鈉溶液雜質(zhì)種類、雜質(zhì)濃度等因素對溶液結(jié)晶率、苛性比、粘度、濁度、電導率等性質(zhì)以及產(chǎn)物的晶體形貌的影響。結(jié)果表明,鋁酸鈉溶液中對結(jié)晶起主要阻礙作用的因素是雜質(zhì)硅。(3)深入探究了超聲波作用下鋁酸鈉溶液結(jié)構(gòu)的變化規(guī)律,明晰了超聲波的作用機理。研究發(fā)現(xiàn),溶液中硅的加入使得其結(jié)構(gòu)變得更加復雜。隨著雜質(zhì)硅的增多,硅氧鍵的吸收峰逐漸變大變寬,原本溶液中的鋁氧鍵等簡單結(jié)構(gòu)逐漸變?yōu)镾i-O-Al交織而成的復雜的網(wǎng)絡狀結(jié)構(gòu)。當有超聲存在時,硅氧鍵的吸收峰明顯減弱,并且出現(xiàn)峰位偏移。這說明超聲過程中,復雜的Si-O-Al等鍵可被斷裂,形成小的碎片形式的結(jié)構(gòu),進而減小了鋁酸鈉成核所需的能量,減小了溶液的粘度,從而有助于鋁酸鈉結(jié)晶的析出。
[Abstract]:Red mud and fly ash in alumina industry are the main solid wastes with high aluminum content in China. Their storage has caused serious social and environmental problems, but at the same time they are also a kind of excellent unconventional aluminum resources. The submolten salt method is used to treat red mud and fly ash to extract alumina. Can successfully achieve the economic recycling of Al2O3, Sodium aluminate solution with higher causticity (> 4) was obtained. The solution with high causticity ratio is difficult to be prepared by the traditional seed decomposition method, which is only suitable for caustic ratio about 1.5 sodium aluminate solution, but the sodium aluminate junction can be used. The method of crystal precipitation first reduces the causticity ratio of the solution, At present, in the practice of semi-industrialization, the crystallization process has many problems, such as long crystallization time, difficult to control the influencing factors and so on. The Institute of process Engineering of the Chinese Academy of Sciences proposed a new method for strengthening the crystallization of sodium aluminate solution by ultrasonic wave. The crystallization efficiency was greatly improved, but the strengthening mechanism was not clear. In this paper, the crystallization process of dissolution solution obtained by submolten salt treatment was studied, and the key factors affecting the solution crystallization were obtained, and the viscosity of solution by ultrasonic wave was studied. The effect of turbidity and other physical and chemical properties on ultrasonic hardening mechanism in crystallization process was analyzed. The following innovative results were obtained: 1) by comparing different sources of fly ash dissolving liquid in ultrasonic crystallization process, the effect of crystallization was different. It was found that the concentration of silicon and iron in the solution would seriously affect the ultrasonic crystallization of the solution. In the experiment, different concentrations of silicon, iron and different initial conditions (initial alkali concentration, initial alkali concentration, etc.) were compared. The initial causticity ratio is different. It is found that when the concentration of silicon changes 0.5-2g / L, and the concentration of iron changes 0.4g / L, the crystallization rate of sodium aluminate solution will be greatly reduced. (2) the effects of impurity types, impurity concentration and other factors on the crystallization rate, causticity ratio, viscosity, turbidity of sodium aluminate solution are studied systematically. The results show that the main obstacle to crystallization in sodium aluminate solution is the impurity silicon. 3) the structure of sodium aluminate solution under the action of ultrasonic wave is studied. The mechanism of ultrasonic wave was clarified. It was found that the addition of silicon in solution made its structure more complicated. With the increase of impurity silicon, the absorption peak of silicon oxygen bond became larger and wider. The simple structures such as aluminum and oxygen bonds in the original solution gradually become complex network structures intertwined with Si-O-Al. The absorption peaks of silicon and oxygen bonds are obviously weakened and the peak position is shifted in the presence of ultrasound, which indicates that in the process of ultrasound, The complex Si-O-Al bonds can be broken to form a small fragment structure, thus reducing the energy required for nucleation of sodium aluminate and the viscosity of the solution, thus facilitating the precipitation of sodium aluminate crystals.
【學位授予單位】：北京化工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ133.1

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本文編號：1614041