界面科学による濾過ケークの構造と圧力損失の基礎研究  [in Japanese] The Characterization of Structures of Cake Layer Based on Electro-kinetic Phenomena  [in Japanese]

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<p>粒子懸濁液のケーク濾過における濾過特性は,粒子間間隙を液体が透過する際に生じる圧力損失を反映する.この粒子間間隙の大きさを評価するため,粒子の周囲に形成される電気二重層の厚さを利用した流動電位に基づく間隙サイズ<i>D</i><sub>sp</sub>の評価方法の開発を行い,従来の評価指標(動水直径<i>D</i><sub>h</sub>,キャピラリー相当径<i>D</i><sub>p</sub>)と比較した.粒子径の異なるPMMA微粒子を用いて形成したケークの<i>D</i><sub>sp</sub>を評価した結果,<i>D</i><sub>sp</sub>は<i>D</i><sub>h</sub>,<i>D</i><sub>p</sub>と同様に粒子の平均粒子径<i>d</i><sub>50</sub>が小さくなるのに従い小さくなる傾向があった.<i>D</i><sub>sp</sub>は,ケーク比抵抗α<sub>AV</sub>が大きいときに小さくなる傾向が得られ,ケーク層中の粒子充填構造の評価に使用できることが分かった.種々の粒子(PMMA粒子,JIS粉体(関東ローム,重炭酸カルシウム),PbSO<sub>4</sub>,Zn(OH)<sub>2</sub>)により<i>D</i><sub>sp</sub>を評価した結果,その絶対値は<i>D</i><sub>h</sub>,<i>D</i><sub>p</sub>に対して1/4~1/10程度の値であった.<i>D</i><sub>sp</sub>と同時に評価される表面電荷密度<i>q</i><sub>p</sub>は粒子の種類に依存し,その絶対値はおよそ1 × 10<sup>–3</sup>から1 × 10<sup>–2</sup> C/m<sup>2</sup>の範囲の値を示した.</p>

<p>The performance of cake filtration depends on the pressure drop due to the permeation of liquid through cake layer. The size of gaps between particles in cake layer dominates the pressure drop. In this study a novel characterization method for the size of gaps based on the thickness of electric double layer around particles was developed and the results were compared with conventional methods based on hydraulic diameter <i>D</i><sub>h</sub> and capillary diameter <i>D</i><sub>p</sub>. The effects of size and morphology of particles were studied with PMMA latex particles, JIS powder (KANTO loam, sodium bicarbonate), PbSO<sub>4</sub>, Zn(OH)<sub>2</sub>. The specific cake resistance, α<sub>AV</sub>, decreased with the decrease in the average particle size. <i>D</i><sub>h</sub> and <i>D</i><sub>p </sub>were decreased with the decrease in <i>D</i><sub>50</sub>. These results showed the smaller particles will make smaller gaps in cake layer. The <i>D</i><sub>sp</sub> could be determined by the analysis of the dependence of streaming potential of cake layer on electric conductivity. <i>D</i><sub>sp</sub> showed almost same trends for particles as <i>D</i><sub>h</sub> and <i>D</i><sub>p </sub>while the absolute value of <i>D</i><sub>sp</sub> showed 1/6~1/10 smaller than <i>D</i><sub>h</sub> and <i>D</i><sub>p</sub>. This result shows the <i>D</i><sub>sp</sub> is useful for the characterization of the size of gaps in cake layer.</p>

Journal

  • Hosokawa Powder Technology Foundation ANNUAL REPORT

    Hosokawa Powder Technology Foundation ANNUAL REPORT 26(0), 105-109, 2018

    Hosokawa Powder Technology Foundation

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