戴怡德臺灣大學：化學工程學研究所林彥志Lin, Yen-ChihYen-ChihLin2007-11-262018-06-282007-11-262018-06-282005http://ntur.lib.ntu.edu.tw//handle/246246/52151近年來，在化學工業的程序上，流化床結晶槽(pellet reactor, crystalactor)技術佔有相當重要的地位，其應用在許多方面，例如：硬水軟化、重金屬去除、除磷、除氟等。就硬水軟化而言，為了利用流體化床來處理硬水，因此必須要找出流體化床中，碳酸鈣晶體的成長動力學模式；早期的文獻多為經驗式，如：總晶體成長模式，雖然此模式相當簡單，但是因為此模式的適用範圍受到限制，所以雙重阻力模式逐漸被採用來詮釋流體化結晶槽內的晶體成長模式。 因此為了探討溶液性質對於碳酸鈣晶體成長的影響，本研究以流體化床為實驗裝置，採用定組成法進行晶體成長實驗，接著利用雙重阻力模式的分析方式，將實驗結果的相對過飽和度與成長速率帶入計算，求得動力學參數之表面反應速率係數、質傳擴散速率係數。並且改變可能會影響晶體成長的變數：pH值、過飽和度、離子強度、離子活性比等，以探討各個變數對於晶體成長動力學參數的影響。另一方面以天然的文石晶體作為晶種，改變溶液的pH值，觀察pH值對於文石成長速率。 本實驗將以下條件固定不變：晶種平均粒徑774 μm、水流表面速度為0.047 m/s、溫度為298 K。為了探討溶液性質，『pH、I與R』，的影響，因此在特定的pH、離子強度與離子活性比下，藉由量測不同相對過飽和度所對應的成長速率，可以探討溶液性質對於成長速率、Kd與Kr的影響。 結果發現pH=8.5~9.5，I=0.005~0.035 M，R=0.4~5.54時，成長速率隨著pH和I值的增加而上升，但是當R約等於1時，成長速率有一最大值。 利用表面反應階數為2的雙重阻力模式分析成長數據時，所得到的質傳擴散速率係數不受pH和離子活性比的影響，但是會隨著離子強度的增加而提高；而表面反應速率係數則是隨著pH值和離子活性比的增加而上升，但是卻不受離子強度的影響。 然而在文石晶種的成長實驗中，pH值的操作範圍在8.3~10之間，隨著pH的上升，成長速率遞減，但是pH值介於9.5~10時，對於成長速率的影響並不顯著。Recently a pellet reactor, which plays an important role in chemical engineering process, has been developed for water softening, fluoride and phosphate removal, and heavy-metal recovery. In the design of a pellet reactor for water softening, we need to know the kinetics of CaCO3 in a fluidized bed. Most of the reported growth-rate model of calcite is rather empirical, for example, an overall growth-rate model. Although the over-all growth model is convenient to use, the applicability of it was limited to a certain range of operating variables. Therefore, the two-step growth model was used to modify the growth kinetics of calcite in a pellet reactor. In this research, the measurement of crystal growth of calcite in a fluidized-bed was designed by using a constant-composition technique, which can be used to study the effects of solution properties. The calcite growth-rate data was analyzed by the two-step growth model to obtain the kinetic parameters of surface-reaction coefficient and mass-transfer coefficient. The effects of operating variables, such as pH, supersaturation, ionic activity ratio, and ionic strength on the coefficients were studied. In addition, an experiment was conducted to study the influence of pH on aragonite growth rate. In the calcite growth experiment, several operation variables were fixed, such as L = 774 μm, v = 0.047 m/s, and T=298 K, then the crystal growth rate data were measured at various supersaturation under specified pH, activity ratio and ionic strength. In the range of the pH value between 8.5 and 9.5, the ionic strength (I) between 0.005 and 0.034 M, and the activity ratio between 0.4 and 5.54, the calcite growth rate increase with an increase in supersaturation, pH value, and ionic strength, however, the growth rate data shows a maximum at an activity ratio around 1. Finally the growth-rate data were analyzed by the two-step crystal growth model by assuming r = 2. The calculated mass-transfer coefficient is rather independent of pH and activity ratio, but varies with ionic strength, the surface-reaction coefficient increase with pH and activity ratio but rather independent of ionic strength. In the experiments of aragonite crystallization, the growth rate decreases with an increase in the pH range between 8.3 and 10, however, the effect of pH is not significant for pH being between 9.5 and 10.中文摘要………………………………………………………………....I 英文摘要………………………………………………………………..III 目錄……………………………………………………………………...V 圖索引………………………………………………………………...VIII 表索引………………………………………………………………….XII 第一章 緒論……………………………………………………………1 第二章 文獻回顧………………………………………………………5 2-1 過飽和度………………………………………………………..5 2-2 介穩區…………………………………………………………..8 2-3 晶體成長與雙重阻力模式……………………………………12 2-4 流化床中的質傳式. …………………………………………..17 2-5 操作變數對晶體成長的影響…………………………………19 2-5-1 溶液性質的影響………………………………………..19 2-5-2 磁場對晶型的影響……………………………………..21 2-6電雙層與零電點………………………………………………..29 2-7 文石晶種的合成………………………………………………33 2-7-1 影響文石成長的條件…………………………………..33 2-7-2 文石單晶的合成反應…………………………………..34 第三章 原理…………………………………………………………..36 3-1 微溶物系溶液組成之決定……………………………………36 3-2 定組成方法……………………………………………………41 3-3 晶體成長速率的計算…………………………………………46 3-4 碳酸鈣晶體介穩區的界定……………………………………49 3-5 雙重阻力晶體成長模式的分析………………………………50 3-6 文石晶種的合成製備…………………………………………51 第四章 實驗裝置與步驟……………………………………………..52 4-1 實驗裝置………………………………………………………52 4-2 實驗藥品………………………………………………………58 4-3 分析儀器………………………………………………………60 4-4 總鈣離子濃度測量分析………………………………………61 4-5 操作原理………………………………………………………63 4-6 實驗步驟………………………………………………………64 4-6-1方解石晶體成長速率之測量……….…………………..64 4-6-2晶體成長速率之求取…………………………………...65 4-6-3文石晶種之合成………………………………………...68 4-6-4帝斯卡鈍水器作用下的文石成長速率量測…………...69 4-7. 實驗過程之應注意事項……………………………………...71 第五章 結果與討論…………………………………………………..72 5-1方解石晶體成長實驗內容及注意事項…………………….…72 5-2溶液性質對於方解石成長速率的影響……………………….75 5-2-1 pH值的效應…………………..………………………...75 5-2-2離子活性比的影響..…………………………………….78 5-2-3離子強度的影響……….………………………………..81 5-3溶液性質對於Kd與Kr的影響………………………………..84 5-3-1 pH值的效應…………………………………………….84 5-3-2 離子活性比的效應……………………………………..90 5-3-3 離子強度的效應………………………………………..94 5-4方解石成長之控制步驟………………………………………100 5-5文石晶種的合成與磁場作用下的成長速率…………………105 5-5-1文石晶種的合成……………………………………….105 5-5-2磁場對文石成長速率之影響………………………….109 第六章 結論…………………………………………………………114 符號說明………………………………………………………………116 參考文獻………………………………………………………………119 附錄……………………………………………………………………1253252852 bytesapplication/pdfen-US方解石定組成動力學雙重阻力模式文石calciteconstant compositionkinetictwo-step growth modelaragonitethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/52151/1/ntu-94-R92524043-1.pdf