- 學位論文
以旋轉填充床回收水中氨氮之研究
Recovery of ammonia from aqueous solution using a rotating packed bed
摘要
本研究使用汽提法去除廢水中氨氮，再將氨氮以高濃度的氨水的形式回收，搭配旋轉填充床(Rotating packed bed, RPB)具有質傳效率高、設備體積小及液體滯留時間短等優勢，建立一套佔地面積小、氨去除效率高且回收產物具有經濟價值的氨氮廢水處理技術。研究主要分為二部分，第一部分探討汽液質量比、填充床轉速(ω)、蒸汽進口溫度(TSi)、液體進口溫度(TLi)與進口液體氨氮濃度(CLi)對氨去除率(ARE)與回收氨水濃度(CR)的影響。研究結果顯示，在不同操作條件下得到ARE與CR的範圍為78.4-98.9 %及2.18-22.9 wt. %，且ARE一般會隨者汽液質量比和ω上升而增加，而TSi、TLi與CLi對ARE的影響不顯著；回收氨水濃度會隨者ω和CLi增加而上升，而隨者汽液質量比、TSi和TLi上升而下降。在汽液質量比、ω、TSi及TLi分別為0.175 kg steam/kg liquid、900 rpm、120 oC及70 oC的條件下為最適操作條件，ARE皆可達到98 %。此外，本研究也探討汽液質量比與ω對總體積液膜質傳係數(KLa)及液相質傳單元高度((HTU)OL)的影響。研究結果顯示，KLa與(HTU)OL皆會隨者汽液質量比上升而下降；提高ω有助於提升KLa與減少(HTU)OL。第二部分為回收氨水再濃縮提純，研究結果顯示，進口氨氮廢水濃度直接影響回收氨水濃度是否達到20 wt. %，經由多次汽提濃縮雖然可以增加回收氨水的濃度，但是回收氨水產量也會因此減少。
並列摘要
This study investigates the steam stripping process to remove ammonia from wastewater and recover high concentration ammonia solution. The rotating packed bed (RPB) is characterized by its high mass transfer efficiency, small volumes of equipment, and short liquid retention time. First, the study investigates the effects of steam to liquid ratio, rotational speed (ω), inlet steam temperature (TSi), inlet liquid temperature (TLi) and inlet liquid concentration of ammonia (CLi) on the ammonia removal efficiency (ARE) and recycling ammonia solution concentration (CR). The results showed that the ARE and CR was found to be in the range of 78.4-98.9 % and 2.18-22.9 wt. %. The results also showed that the ARE was increased with the increase of steam to liquid ratio and ω, but the effects of the TSi, TLi, and CLi on the ARE were not significant. The CR was increasing with the increase of ω and CLi, but decreased with the increase of steam to liquid ratio, TSi, and TLi. The optimal operating conditions are: steam to liquid ratio of 0.175 kg steam/kg liquid, ω of 900 rpm, TSi of 120 oC, and TLi of 70 oC while the ARE could achieve 98 %. In addition, this research also investigates the effects of steam to liquid ratio, and ω on overall volumetric liquid-phase mass transfer coefficient (KLa) and overall height of a mass transfer unit based on liquid-phase resistance ((HTU)OL). The results showed that KLa and (HTU)OL were decreased with the increase of steam to liquid ratio, and the increase of ω was favorable for enhancing KLa and reducing (HTU)OL. Then the recycling experiments for increasing the concentration of ammonia solution were performed. The objective of the recycling experiments is to obtain the ammonia solution concentration greater than 20 wt. %.