以流體化床去除半導體廠廢水中鈣之研究

本研究設計流體化床反應槽處理臺灣半導體之實場逆滲透及冷卻廢水。目的在於減少廢水中硬度，使其可回收再利用。設置方法是採用石英砂顆粒為流化床反應槽之結晶介質，利用碳酸鈣鈉、氫氧化鈣及氫氧化鈉三種鹼性物質控制pH值，來探討過飽和度之去除作用，再比較向上流速度，進水濃度，氣泡總去除率之影響。採樣之樣品利用離子色譜法測定進出水陰陽離子濃度，而結晶後之沙粒使用掃描電子顯微鏡和XRD進行分析。研究顯示，最佳去除效率之pH值為9.5∼10.5，鹼度添加以碳酸鈉效果最好，隨添加劑量增加可達95％。而在氫氧化鈉方面，去除率為60％且水質較為清澈。氫氧化鈣則是僅能去除40％。隨著上升速度增加，混合較均勻，去除效率也越好。在反應器中加入氣泡，反而會使去除效率些微降低。

關鍵字

鈣去除；流體化床；去除率；過飽和度

並列摘要

In this study, a fluidized bed reactor was employed to treat wastewater from reverse osmosis and cooling water system of one semiconductor industry in Taiwan. The main purpose was to reduce calcium content of the water for reuse. The treatment was done by crystallization in the fluidized bed reactor with quartz sand as the pellet media. The wastewater was supersaturated with calcium at different pH levels. Several chemicals were used to study the effect of nucleation on calcium removal rate. The experimental parameters include upward fluid velocity, dissolved ion concentrations in influent water and size of pebbles. The ionic concentrations of influent water were measured using ion chromatography. The crystals formed on the surface of sand were analyzed using scanning electron microscopy and x-ray diffraction. The optimum pH for effective removal was found to range from 9.5 to 10.5. The choice of chemical to be used to facilitate calcium removal depends on the concentration of carbonate in the waste water. For calcium concentrations and alkalinity used in this study, use of sodium carbonate could remove up to 99% of calcium, but resulted in a very high carbonate alkalinity. Sodium hydroxide could remove up to 60% of calcium and resulted in much clear water. Calcium hydroxide can remove up to 40% of calcium. Increasing the upward velocity resulted in better mixing and better removal. The bubbling into the reactor created a slugging bubble and decreased mixing efficiency in the reactor.

並列關鍵字

calcium removal ； fluidized bed reactor ； removal rate ； supersaturated

參考文獻

Aldaco, R., Irabien, A. and Luis, P. (2005). "Fluidized bed reactor for fluoride removal." Chemical Engineering Journal, 107(1–3), 113-117.

Baeyens, J. and Geldart, D. (1974). "An investigation into slugging fluidized bed." Chemical Engineering Science, 29, 255-265.

Carman, P. C. (1956). Flow of Gases Through Porous Media. London, Butterworths.

Clifford, Y. T., Chien, W. C. and Chen, Y. C. (1999). "Crystal growth kinetics of calcite in a dense fluidized-bed crystallizer." AIChE Journal, 45(8), 1604-1614.

Davis, K. J., Dove, P. M. and De Yoreo, J. J. (2000). "The Role of Mg2+ as an Impurity in Calcite Growth." Science, 290(5494), 1134-1137.

國際替代計量

以流體化床去除半導體廠廢水中鈣之研究

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