高科技產業氟化鈣污泥做為水泥生料之可行性研究

Abstract

摘 要 高科技產業廢水處理產出之氟化鈣（CaF2, Calcium Fluoride）污泥的量大且受制於掩埋土地的不足而不易處置，且自2000年起，環保機關公告許多行政命令管制其處置與再利用。再利用技術已經發展了一段時間，適量的氟化鈣污泥加入水泥製程當中，並不會影響水泥的品質。然而，並無相關研究討論污泥中氟是否會隨燒結氣體排放出來，所以本研究於實驗室中建立一模擬水泥窯實廠條件之燒結設備，以添加某高科技產業廢水處理產出之氟化鈣污泥於生料中，進行燒結試驗，並分析氟在排氣中的分佈與平衡。 本實驗取40 g水泥生料，其中含有0.5﹪(w/w) 之純氟化鈣試藥，進行燒結試驗，並收集燒結中所產生的氣體，分析氣體中的總氟含量。實驗結果顯示，氟化鈣中的氟（F, Fluorine）在高溫燒結過程中有釋出的現象。在1000℃燒結溫度下，燒結20分鐘，燒結氣體中所釋出的總氟量約0.97 mg；而1200℃燒結溫度下，總氟的釋出量則增加至4 mg；到達1450℃，即水泥窯中之實際溫度，氟的釋出量則達9.3 mg，約佔生料中氟含量的8.9﹪。當同樣的水泥生料中改加入某高科技工廠之氟化鈣污泥，由於氟化鈣污泥之純度只有60﹪(w/w) ，因此添加量提升到1﹪，則40 g內含1﹪氟化鈣污泥之生料於1450℃中燒結，其排氣中的氟則高達14.6 mg，約佔生料中氟含量的10.5﹪。但水泥窯中高活性之氧化鈣（CaO, Calcium Oxide），在900℃會吸附揮發的氟，融入水泥熟料當中。實驗結果亦發現，在燒結設備後加裝氧化鈣之吸附裝置，並維持氧化鈣溫度900℃，則不管是內含0.5﹪氟化鈣試藥或1﹪氟化鈣污泥，最後氟之排放量均僅剩下約生料中氟含量之0.05﹪(w/w)。總氟質量平衡則顯示大部分的氟，主要還是存在於水泥熟料之中，約佔總含量的80％左右。 試驗結果顯示添加氟化鈣污泥的水泥生料，水泥生料的氟的在高溫燒結的環境中會被釋出象，且隨著燒結溫度的提升，氟的釋出量也愈高。如果讓燒結氣體通過900℃的氧化鈣吸附裝置時，燒結排氣中總氟含量明顯降低，推斷氧化鈣在900℃溫度下，對氟離子有一定的吸附能力。

Abstract The quantity of calcium fluoride from wastewater treatment in high technical industry is very large and not easy to be treated because the landfill is not enough in Taiwan. Since 2000, environmental manager agency announced many administrative decrees to control treatment and reuse of CaF2 sludge. The reusing techniques have developed for a long time. Moderately adding CaF2 sludge in the process of cement manufacture does not affect the quality of cement. However, there are not relative researches in fluorine releasing to air emission from sludge during sintering. Therefore, for this study, a set of sintering equipment that imitates the cement rotary kiln is established in the laboratory. CaF2 sludge is added in the raw meal as additive, and to confer the distribution and balance of fluorine in gas phase during the sintering process. In this experiment, 40 g raw meal of cement that contains 0.5﹪(w/w) pure calcium fluoride reagent was sintered in imitated equipment of laboratory. The exhaust is collected and analyzed the content of total fluorine. The results showed that fluorine of calcium fluoride was released in high sintering temperature. There is 0.97mg of fluorine released at 1000℃and 20 minutes sintering. At 1200℃, it increases to 4 mg. When getting 1450℃ that is the temperature in real cement kiln, 9.3 mg fluorine was released and it occupied 8.9﹪(w/w) fluorine of raw meal of cement. When the CaF2 sludge replaced pure calcium fluoride, the quantity of additive increased to 1﹪because the concentration of calcium fluoride in the sludge of someone high technical factory is 60﹪(w/w). There are 14.6 mg fluorine was released at 1450℃, it occupied 10.5﹪(w/w) fluorine of the raw meal of the cement. Calcium oxide has high activity, it can adsorb vapor of fluorine at 900℃, then the adsorbent melt in mature meal of cement. If one calcium oxide absorber that kept on 900℃ is connected after sintering equipment, no matter 0.5﹪(w/w) pure calcium fluoride or 1﹪(w/w) CaF2 sludge contained, there are only 0.05﹪(w/w) fluorine of raw meal of cement was released. Calculating the mass balance of fluorine shows that 80% fluorine is in cement mature meal. Summary of the result, adding the CaF2 sludge in the cement raw meal causes the fluorine released at the high sintering temperature. And the amounts of released fluorine are getting more with increasing the temperature. However, if let the exhaust pass through an calcium oxide absorber that is 900℃, the content of total fluorine in the emission air is lower. At this temperature calcium oxide has high adsorbing capacity for fluorine.