二氧化氯殺菌效能應用於冷卻水塔之實廠評估

Abstract

冰機的用電量一直以來就是工廠最耗電的部分，而影響冰機效率的其中一個重要參數就是趨近溫度；且冰機運轉時冷煤需要靠冷卻水塔的循環水來做熱交換，因此冷卻水塔內水質的控制就益顯重要，尤其是總菌落數項目；因為細菌若在冰機內部與冷煤作熱交換的銅管管璧形成生物膜，除了會影響熱交換效率造成冰機耗電增加外，生物膜更有可能會對銅管造成腐蝕；一般來說，次氯酸鈉(NaOCl)是最常被當做水處理系統的殺菌劑，因為它便宜且容易取得；但國內卻缺乏將二氧化氯殺菌(ClO2)應用於實廠冷卻水塔之案例。 有鑑於此本實驗評估以二氧化氯來取代次氯酸鈉，而實驗所使用之二氧化氯是以化學法之亞氯酸鈉及鹽酸反應產生高純度之二氧化氯，全程在實廠紀錄加藥前後之水質變化、冰機及金屬管路之腐蝕率，最後並藉由冷卻水塔之補水添加量、冰機趨近溫度改善情況來推估本研究之經濟效益，以兼顧理論與實廠應用之務實性。研究結果顯示，以化學法產生高純度之二氧化氯是一種極為有效之生物殺菌劑，使加藥後冷卻水塔之水質總菌落數下降至~ 5.0Î102 CFU/mL；冰機趨近溫度平均下降1℃以上；以本實廠為例：每年可節省費用達百萬元以上。

The chiller has always been the most powerful consumption operation unit among the factories. One of the most important parameter to remain the chiller operation efficiency is the approach temperature. During the operation, circulating water through cooling towers for heat exchanged is needed, therefore it has become the significantly important to keep good water quality by cooling tower, particularly the total bacterial count. Bacteria growth has become biofilm attached inside copper pipe within heat exchange unit, it will cause not only additional power consumption but also pipe corrosion. Conventionally, sodium hypochlorite (NaOCl) is the mostly used for disinfectants to water treatment since it’s very cheap and easy to access, however, we are short of the research of cooling tower operation by chlorine dioxide in Taiwan. This study is to evaluate how chlorine dioxide (ClO2) to replace sodium hypochlorite. The high-purity chlorine dioxide was produced via a chemical reaction by sodium chlorite and hydrochloric acid reacted. Continuous monitoring and data recording all the time during the trial for water quality, metal pipe line and inside copper pipe of chiller corrosion rate before and after dosing chlorine dioxide. Finally, we are about to evaluate the operation economical benefits via comparisons of cooling towers supply water addition rate and approach temperature variations.

The result indicated that high-purity chlorine dioxide is an extremely effective disinfectant; the total bacterial count in the cooling towers is decreased to the level of 5.0Î102 CFU/mL, chiller’s approach temperature is improved and dropped more than 1 ℃ in average. Also it is achieved and saved more than NT$ 1 million/year cost compared to current trial run plant on site.