以連續式電去離子單元應用於超純水系統

Abstract

超純水系統是現今工業製程所需之必要系統，無論是半導體業、面板業、電子級化工、精密工業都需要使用大量的超純水；但高潔淨的超純水在製造過程中卻帶來許多的能耗與藥品的排放，可說是不環保但又必須高度需要的系統。因此如何削減超純水系統的藥品使用量與減少超純水系統中廢水的排放是本次研究的主要目的。 本研究是利用連續式電去離子單元與二段式逆滲透單元取代原超純水系統陽離子樹脂塔、陰離子樹脂塔、混床樹脂塔。並以實廠為例，在不影響既設系統水質、水量、下進行，並對既有樹脂塔單元進行改造前的水質分析與改造後的水質比對最終再進行運轉成本分析之差異研究。 連續式電去離子單元與陽離子樹脂塔、陰離子樹脂塔、混床樹脂塔(mixed bed)最大不同之處為連續式電去離子單元是利用電再生方式以達到再生之目的，使用連續式電去離子單元不需要設置酸鹼藥品槽、酸鹼藥品再生泵、再生水塔槽，所以就系統空間配置上本研究發現在以連續式電去離子單元取代傳統樹脂塔後可以多出原傳統樹脂再生系統65% 的空間，就空間而言更為節省。 安裝連續式電去離子單元後分析產水之比阻抗值為＞18 MΩ．cm (at 25℃)、陰離子為<1 μg/L 、金屬離子為<1 μg/L,均可以達到原有系統設計之功能，並在硼離子與二氧化矽去除率上面亦得到良好的去除率。運轉成本為若使用陽離子樹脂塔、陰離子樹脂塔、混床樹脂塔單元處理的成本為5.6元/M3使用連續式電去離子單元為4.9元/M3 ，以長期運轉來看使用連續式電去離子單元取代傳統樹脂單元的超純水系統設置相信是未來的趨勢。

All pure water system is a necessary system in the current industry, including semi-conductor, panel industry, electric related chemical industry and fine-tuned mechanism industry, they all need large quantity of pure water involved, However, the highly pure water comes along with energy consumption and medicine related chemical emission problems that is not only environment unfriendly but also highly being needed to run the system, therefore, how to reduce the quantity of chemicals usage and waste water emission is the purpose of this study. The study is using a continuous electro-deionization (EDI) unit and two-pass RO unit to replace cation tower, anions tower and mixed-bed, taking on the site factory for example, under the conditions of non-affection to the current water quality and quantity set by the system, carrying out water quality analysis and making cross check the water quality between transformation and transformation of the current resin tower unit. That of the major difference of continuous EDI unit with the cation/anions/mixed-bed towers is the regeneration method. Moreover, using the continuous EDI unit does not require to install chemical storage tanks, regeneration pumps, and regeneration tanks, as to the space arrangement concerned, the study revealed after using the continuous EDI unit to replace the traditional resin tower, there will be 65% more space available left, compared to that of conventional resin regeneration system, as far as the space placement concerned, that is much more cost saving. After installing the continuous EDI unit, water quality for resistivity is higher than 8MΩ．cm (at 25℃), anions concentration is less than 1 μg/L, metal ion concentration is less than 1 μg/L. Those changes can achieve the originally designed function of the system as well as have a good cleaning rate on the aspect of boron and silica. As for the operation cost concerned, the management cost of using the cation tower, anions tower and mixed-bed is 5.6 NT dollars /m3, however, using the continuous EDI unit only stands 4.9 dollars/m3, as far as long running operation concerned, using the continuous EDI unit to replace the traditional resin tower unit concerning the installing of all pure water systems, we deeply believe that will be a foreseeable trend in the future.