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研究生:黃奕舜
研究生(外文):Yi-Shun Huang
論文名稱:利用浮動物件控制因曝氣作用逸散至空氣中之有害氣懸微粒
論文名稱(外文):Control of aerosols producing from bubble bursting by using floating objects
指導教授:陳志傑陳志傑引用關係
口試委員:吳章甫林文印蕭大智余國賓
口試日期:2011-08-01
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:職業醫學與工業衛生研究所
學門:醫藥衛生學門
學類:公共衛生學類
論文出版年:2011
畢業學年度:99
語文別:中文
論文頁數:42
中文關鍵詞:浮動物件氣泡破滅薄膜液滴氣泡聚合
外文關鍵詞:floating objectsbubble burstingfilm dropletscoalesced bubble
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泡沫的破裂或曝氣作用是一種常見的現象,存在於許多自然和人為的過程。當氣泡從水中上升至空氣中破滅時產生兩種不同的液滴,一個是數量較多但較小的薄膜液滴,另一種是數量較少但較大的噴射液滴。過去研究顯示,氣泡上升通過水體會藉由清除作用使微粒和細菌附著其表面,氣泡破滅所生成之薄膜和噴射液滴便富含水體中的懸浮物質。水分蒸發後,這些物質懸浮於空氣中而造成健康與環境衛生上的問題。
在本研究中,我們利用壓克力建立一個曝氣槽以模擬因氣泡破裂而生成之液滴,並藉由放置浮動物件於水體表面,以減少於曝氣過程所產生的微粒。浮動物件主要為各種不同直徑之保麗龍球以及不同孔隙度之海綿,並利用單一粒徑分布之壓克力粉加入水中以模擬存在於水體中之微生物,另外於水中添加界面活性劑以改變水體之表面張力。氣泡破滅生成之微粒經過擴散乾燥管後,利用倒置於液面上方約50公分處之氣動微粒分徑器監測其濃度及粒徑分布。表面張力及曝氣流量為實驗主要之操作參數。
結果表明,當氣泡形成大於球體縫隙之空間時,薄膜液滴之穿透率可能有超出100 %的現象發生。這是因為多個氣泡的聚合生成一個更大的氣泡後,形成突出球體表面之薄膜,接著破裂形成更多的薄膜液滴。同時,各種直徑球體皆能有效抑制噴射液滴之產生。單層球體之穿透率隨著流量的增加而提升,其原因為流量提高而生成更多的氣泡且聚合,破裂後生成更多薄膜液滴。使用多層球體對於曝氣生成微粒有抑制作用但有層數之限制,當液滴產生時,這些疊層球體無法有效移除這些微粒。使用海綿抑制後之穿透率,隨著海綿密度之增加而降低。然而,高孔隙度之海綿具有較高阻抗,使其將會被氣流抬起無法平穩放置於水面上。水體之表面張力變化對於穿透率有特殊的影響。穿透率隨表面張力降低而逐漸提高至某種程度後,由於生成過多的氣泡而累積出泡沫層,使得穿透率下降。對泡沫層之氣泡而言,並非所有的薄膜液滴能有效逸散於空氣中。


Bubble bursting or aeration is a common phenomenon found in many natural and man-made processes. There are two types of droplets generated when bubbles rising from liquid to air and bursting on the liquid surface. One is the more numerous, smaller film droplets, and the other is a few larger jet droplets. Previous studies have shown that bubbles rising through a liquid scavenge particles and bacteria on their surfaces. Both film and jet droplets generated by bubble bursting may be enriched with dissolved and suspended materials from the liquid. After the droplets evaporation, these material residues may remain airborne and become a health issue or environmental problem.
In the present study, a Plexiglas aeration tank with bubble diffuser was built to simulate the droplet generation from bubble bursting. In order to reduce the amount of bubble-bursting generated droplets, a variety of floating objects were placed on liquid. The floating objects included round polystyrene balls of different diameter and polyurethane foam filters of different porosity number. Monodisperse acrylic powder was used to simulate microbes in water. Surfactant was used to vary the surface tension of the liquid. After passing through a diffusion drier, the aerosol concentration and size distribution of the droplets were monitored by using an Aerodynamic Particle Sizer placed about 50 cm above the liquid surface. Surface tension and air flow were among the major operating parameters.
The results showed that the penetration rate of film droplets could exceed 100% when the bubble size was larger than the interstitial space among balls. This was because the bubbles coalesced and became a larger bubble to climb up the polystyrene ball layer and then burst to form more film droplets. Meanwhile, the jet droplets generation was effectively suppressed by the floating ball of all sizes. The aerosol penetration through single layer of floating balls increased with increasing flow rate because there were more bubbles to coalesce to generate more film droplets. The use of multiple layers of floating balls helped reduce the film droplets but with a limit. This was because these balls did not efficiently remove the droplets once they were formed. The aerosol penetration through foam filters decreased with increasing foam porosity number. However, the foam filter of high porosity number might become levitated and stayed away from the liquid surface because of its high air resistance. Surface tension affected the aerosol penetration in a unique way. The aerosol penetration increased first with decreasing surface tension to some extent, then decreased because the coalesced bubbles became too foamy. For foamy bubbles, not all film droplets were effectively released to air.


目錄
口試委員會審定書 I
致謝 II
摘要 III
Abstract IV
目錄 VI
表目錄 VIII
圖目錄 IX

第一章 研究背景與目的 1
第二章 文獻回顧 2
第三章 研究材料與方法 8
3.1 實驗系統 8
3.1.1 曝氣槽模擬系統 8
3.1.2 以單一粒徑壓克力微粒模擬水體中物質 8
3.1.3 單一薄膜生成系統 8
3.1.4 實驗操作參數 9
3.2 監測儀器 9
3.2.1 氣動微粒分徑器 9
3.2.2 凝結核微粒計數器 9
3.2.3 表面張力計 10
3.3 實驗步驟 10
3.3.1 曝氣槽模擬 10
3.3.2 固態及液態微粒逸散 10
3.3.3 浮動物件控制固態微粒逸散之效率 10
I. 球體 11
II. 海綿 11
3.3.4 水體特性對浮動物件抑制效率之影響 11
第四章 實驗結果與討論 12
4.1 曝氣槽中固態及液態微粒逸散情形 12
4.2 氣泡直徑與浮球大小 12
4.3 浮動物件控制微粒逸散之效率評估 13
4.3.1 保麗龍球之控制效率評估 13
I. 單層球體 13
II. 薄膜大小與生成之微粒 14
III. 多層球體 14
4.3.2 海綿控制微粒逸散之效率評估 15
I. 不同孔隙度之單層海綿比較 15
II. 相同孔隙度之多層海綿比較 16
III. 海綿碎塊單層及多層比較 16
4.3.3 界面活性劑對浮動物件抑制效果之影響 17
I. 保麗龍球 17
II. 海綿 17
第五章 結論與建議 19
第六章 參考文獻 21

表目錄
表一 單層球體數量及其未覆蓋之開放面積 25
表二 單層球體與海綿使用之流量及表面風速上限 26

圖目錄
圖一 曝氣槽模擬系統圖 27
圖二 單一薄膜生成實驗系統 28
圖三 微粒之乾燥前後比較 29
圖四 曝氣生成微粒之掃瞄式電子顯微鏡照片 30
圖五 浮球於曝氣槽系統中排列情形 31
圖六 不同直徑球體在相同曝氣流率下微粒逸散之控制情形 32
圖七 相同直徑球體在不同曝氣流率下微粒逸散之控制情形 33
圖八 單一薄膜及其單位面積之微粒生成量 34
圖九 球體堆疊對微粒逸散之控制情形 35
圖十 不同孔隙度之海綿對微粒逸散之控制情形 36
圖十一 相同孔隙度海綿之層數堆疊對微粒逸散之控制情形 37
圖十二 海綿之單純穿透率 38
圖十三 海綿碎塊層數堆疊對微粒逸散之控制情形 39
圖十四 浮球於含界面活性劑水體對微粒逸散之控制情形 40
圖十五 水體中界面活性劑濃度變化對78 mm浮球之微粒逸散控制情形 41
圖十六 水體中界面活性劑濃度變化對42 ppi海綿之微粒逸散控制情形 42



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