從都市垃圾焚化廠回收底渣時,鹽類和重金屬的含量必須加以考慮;尤其是氯離子會嚴重腐蝕金屬,必須另外加以清除處理,以增加底渣再利用之用途,甚至可將底渣作為混凝土骨材。除了探討氯離子的分佈特性之外,本研究也利用上流式反應器(upflow reactor)和兩種不同的淋洗方式及流量作為實驗變數,並研究去除氯離子前和去除氯離子後的特性改變。實驗結果顯示,以上流淋洗方式去除氯離子底渣的特性,如酸鹼值、氯離子濃度都會降低,並且產生清洗效果。高流量時的每單位時間去除氯離子效率最高,在流量為110 mL/min時,使用6,600 mL之用水量(120倍孔隙體積),氯離子的去除率可達95 %,而且底渣中氯離子的殘餘量可達0.0175 %,符合底渣第一類再利用之規範≦0.024 %。
The highly potential content of salts and heavy metal has to be considered while recovering bottom ash from municipal waste incineration plant. Among those unpleasant gradients, especially the chloride ion which will seriously contribute corrosion on metal surface must be removed properly, before any possible reuse like using bottom ash as concrete aggregate. In addition to the probing of distribution of chloride ion, this study also used upflow reactor and two different leaching methods as the experimental variables to study the chlorine characteristics before and after the removal. Experimental results show that the removing of chloride by counter-current measure produces cleaning effect which will bring down pH value and chloride concentration as well. The best cleaning performance obtained in this study could reach up to 95% of removal by high flow rate like 110 mL / min, using 6,600 mL of water (120 times the pore volume). And the chloride content remained in the bottom ash will be around 0.0175%, which stands in line with the end of the first class in the reuse of bottom ash specification ≦ 0.024%.