本文選題：硝酸鉀水溶液 + 冰晶　； 參考：《天津科技大學》2017年碩士論文

【摘要】：冷凍濃縮是一種綠色、節(jié)能的結晶方式,被廣泛地應用于食品和化工等領域。雖然由冷凍濃縮得到冰晶的生產(chǎn)路線比較成熟,但是目前國內(nèi)由冷凍濃縮技術得到的冰晶存在晶體粒度小且粒度分布不均勻等問題,不能滿足市場需要。本文系統(tǒng)的對硝酸鉀水溶液冰晶的結晶熱力學和動力學進行了實驗和理論研究,同時考察了各種因素對硝酸鉀水溶液冰晶粒度的影響。首先,對硝酸鉀水溶液的冰晶進行結晶熱力學的研究。實驗建立并驗證了測定冰點溫度的方法,并通過實驗建立的測定冰點溫度的方法測定了硝酸鉀水溶液的冰點數(shù)據(jù),實驗結果表明,硝酸鉀水溶液的冰點數(shù)據(jù)較好的符合Extend-UNIQUAC模型,向硝酸鉀水溶液中摻加雜質(zhì),雜質(zhì)離子半徑越小,其冰點溫度越低。同時用直接觀察法測定了硝酸鉀水溶液的介穩(wěn)區(qū),并考察了雜質(zhì)離子、降溫速率對介穩(wěn)區(qū)寬度的影響。結果顯示,陽離子雜質(zhì)的價態(tài)越高,介穩(wěn)區(qū)寬度越寬,陰離子反之。并利用基于經(jīng)典成核理論所推導的介穩(wěn)區(qū)寬度模型方程對試驗數(shù)據(jù)進行模擬計算,模擬結果與實驗值符合較好,計算得到硝酸鉀水溶液的冰晶成核級數(shù)為1.46。其次,對硝酸鉀水溶液的冰晶進行動力學研究。采用間歇動態(tài)法測定了硝酸鉀水溶液冰晶的結晶動力學,實驗結果表明,硝酸鉀水溶液冰晶的生長與粒度相關,采用MJ2模型,通過矩量變換法,使用1stOpt軟件中的麥夸特法(Levenberg-Marquardt)和通用全局優(yōu)化法對實驗數(shù)據(jù)進行了擬合,得到了硝酸鉀水溶液冰晶結晶的成核與生長速率的動力學方程,從擬合的結果可以看出,過飽和度AC與懸浮密度MT是影響晶體成核與生長的主要因素。最后,結合硝酸鉀水溶液冰晶的結晶熱力學和動力學分析結果,對硝酸鉀水溶液冰晶的粒度控制進行了研究。實驗考察了降溫速率、攪拌速率及晶種添加量對硝酸鉀水溶液的冰晶的粒度及粒度分布的影響。實驗結果表明:降溫速率、攪拌速率、晶種等因素對產(chǎn)品的粒度分布有著重要的作用。
[Abstract]:Freezing concentration is a green and energy-saving crystallization method, which is widely used in food and chemical industry. Although the production route of freezing concentrated ice crystals is relatively mature, the current domestic ice crystals obtained by freezing concentration technology have some problems such as small crystal size and uneven distribution of grain size, which can not meet the needs of the market. In this paper, the crystallization thermodynamics and kinetics of potassium nitrate aqueous solution ice crystals have been studied systematically, and the effects of various factors on the grain size of potassium nitrate aqueous solution ice crystals have also been investigated. Firstly, the crystallization thermodynamics of ice crystals in potassium nitrate aqueous solution was studied. The method of measuring freezing point temperature was established and verified, and the freezing point data of potassium nitrate aqueous solution were determined by the method established by experiment. The experimental results showed that the freezing point data of potassium nitrate aqueous solution were in good agreement with Extend-UNIQUAC model. The smaller the impurity radius is, the lower the freezing temperature is. At the same time, the metastable zone of potassium nitrate aqueous solution was determined by direct observation, and the influence of impurity ion and cooling rate on the width of metastable zone was investigated. The results show that the higher the valence state of cationic impurity is, the wider the width of metastable region is, and the other is anion. The experimental data are simulated and calculated by using the metastable zone width model equation derived from the classical nucleation theory. The simulation results are in good agreement with the experimental data, and the nucleation order of ice crystals in potassium nitrate aqueous solution is calculated to be 1.46. Secondly, the kinetics of ice crystals in potassium nitrate aqueous solution was studied. The crystallization kinetics of ice crystals in potassium nitrate aqueous solution was determined by batch dynamic method. The experimental results show that the growth of ice crystals in potassium nitrate aqueous solution is related to the grain size. The MJ2 model and the moment transformation method are used to determine the crystallization kinetics of ice crystals in potassium nitrate aqueous solution. Using Levenberg-Marquardt method in 1stOpt software and general global optimization method, the experimental data were fitted and the kinetic equations of nucleation and growth rate of ice crystal crystallization of potassium nitrate aqueous solution were obtained. Supersaturation AC and suspended density MT are the main factors affecting the nucleation and growth of crystals. Finally, the particle size control of potassium nitrate aqueous solution ice crystal was studied by combining the results of thermodynamics and kinetics analysis. The effects of cooling rate, stirring rate and seed content on the grain size and distribution of ice crystals in potassium nitrate aqueous solution were investigated. The results show that the cooling rate, stirring rate, seed and other factors play an important role in the particle size distribution of the product.
【學位授予單位】：天津科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ131.13;O78

【參考文獻】

相關期刊論文 前10條

1 付茜;詹先成;徐敖;;藥物溶液冰點的理論計算[J];華西藥學雜志;2016年01期

2 鐘劍鋒;陳葵;朱家文;武斌;;濕法磷酸熔融結晶的靜態(tài)與懸浮過程研究[J];化工礦物與加工;2015年04期

3 文玲;張旭;;冷凍濃縮處理廢水COD、TOC及能耗分析[J];環(huán)境科學與技術;2014年01期

4 曾桂生;李慧;王賢勇;;無水硫酸鈉結晶熱力學及介穩(wěn)區(qū)寬度研究[J];南昌航空大學學報(自然科學版);2012年04期

5 陳愛梅;朱家文;武斌;陳葵;紀利俊;吳艷陽;;熔融懸浮結晶法提純濕法磷酸[J];化學工程;2012年08期

6 吳俊;黃民;郭思斯;王琰;李佟茗;孔德金;;雙進料混合二甲苯連續(xù)懸浮結晶工藝的優(yōu)化[J];高�；瘜W工程學報;2010年04期

7 韓強;劉瑞t，

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