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    题名: 攪拌系統中膠體顆粒凝絮機制與穩態分析;Aggregation of colloidal aggregation in an agitated system
    作者: 邱信菖;Shin-Chang Chiou
    贡献者: 環境工程研究所
    关键词: 軌跡分析;凝絮效率;擾流狀態之剪力流;穩態分析;stability diagram;turbulent shear;Aggregation efficiency;trajectory analysis
    日期: 2005-07-19
    上传时间: 2009-09-21 12:17:02 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 本研究以軌跡分析模擬顆粒在擾流狀態之剪力流場中的運動行為,在忽略布朗運動及重力作用的情形下,探討離子強度、顆粒間凡德瓦爾吸引力、靜電斥力與流場中剪應力,對兩顆粒間碰撞效率的影響,結果發現,在高離子強度(0.01~0.1 M)中,碰撞效率是隨著Hamaker constant的上昇而增加,而不隨界達電位改變,另外在低離子強度(0.0005~0.001 M)、高粒徑比(0.9~1.0)、高轉速(300rpm)且低Hamaker constant (A=8E-20 J)時,此時若界達電位越大,越容易發生碰撞效率越低或等於零的情形。當轉速與粒徑漸增時,碰撞效率都是呈現逐漸下降的趨勢。利用統計分析,建立碰撞效率迴歸式後發現,在I=0.0005~0.1 M,粒徑比0.2~0.8之間,碰撞效率是與Ca0.1呈現正比關係;接著在I=0.0005~0.1 M,粒徑比為0.9 與 I=0.01~0.1 M,粒徑比為1.0中,碰撞效率是與Ca0.2呈現正比關係;最後,在I=0.001 M與0.0005 M,粒徑比為1.0中,碰撞效率與Ca0.3呈現正比關係。最後是繪製NR -NF及κ (ri+rj)-NF穩定機制圖,主要將混凝區域分為三大部分:一級混凝區、二級混凝區與穩態區,穩定機制圖的目的是爲了避免繁雜的計算,來求得顆粒是位於何種混凝區,所以利用假設的參數條件,經過簡易的計算 κ (ri+rj)、NF與NR,就可判定是何種混凝區。 Aggregations of colloidal particles in stirred tanks were modeled by trajectory analysis in this study. The influences of Hamaker constant, ionic strength (I), zeta potential, and agitation speed on the collision efficiency between two unequal-sized particles were investigated. The simulation results showed that at high ionic strength, the collision efficiency increased with increasing Hamaker constant and were not affected by zeta potentials. When ionic strength is low and particle size ratio is close to 1, the collision efficiency dropped to zero at high zeta potentials. A semi- empirical collision efficiency equation was formulated using STATISTICA by analyzing trajectory analysis results. It was found that the collision efficiency is a function of Ca to the power of 0.1, 0.2, and 0.3 at I = 0.0005 ~ 0.1 M and ??(particle size ratio) = 0.2 ~ 0.8, I = 0.0005~0.1 M and ? = 0.9, as well as I = 0.01 ~ 0.1 M and ? = 1, respectively. Stability diagram of particle aggregations in stirred tanks was also established. Influences of various parameters on the boundaries in the stability diagram were also discussed.
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