跳到主要內容 :::

年度	109	專案性質	實驗性質
專案類別	研究專案	研究主題	整治
申請機構	國立台灣大學	申請系所	環境工程學研究所
專案主持人	林逸彬	職等/職稱	教授
專案中文名稱	以燒結法再生重金屬污染土壤生產水泥之研究
中文關鍵字	水泥, 重金屬土壤處理, 燒結
專案英文名稱	Regeneration of Heavy Metal Contaminated Soil by Cement Sintering Method
英文關鍵字	Cement, Heavy Metal Contaminated Soil, Sintering
執行金額	970,000元
執行期間	2020/1/1 至 2020/12/31
計畫中文摘要	隨著工業的發展， 因含有重金屬的廢棄物及廢水被不當的處置與排放， 導 致土壤重金屬污染問題產生。水泥窯協同處理(co-processing)可在不改變產品的最終質量和品質條件下， 利用廢棄物替代部分的製程燃料或水泥原料，以降低生產成本並減少環境負荷，達到有害廢棄物處理的目的。 由於結合水泥高溫燒結與重金屬污染土壤處理再利用的案例並不多，對於水泥製程參數的影響、最大可處理之污染土壤量、溶出方法適宜性等問題亦缺少討論，加上相關法規標準的不完善，造成此技術的發展仍有所限制。本研究透過添加不同種類的污染土壤、 控制土壤取代原料配比和燒結溫度等水泥製程參數製作水泥， 利用事業廢棄物毒性特性溶出程序(TCLP)、合成降水溶出程序(SPLP)及 EDTA 輔助 TCLP溶出程序(EDTA-mediated TCLP)等三種溶出方法檢測重金屬溶出量，進一步評估此污染土壤處理再利用方法之可行性。 本研究使用之污染土壤重金屬組成分別為場址1含銅、鋅及高濃度鉻， 場址 2則具有鉻、銅、鉛、鋇、鋅與較高濃度但不受法規限制之錳。 經由水泥原料及土壤組成成分分析與生料配比測試， 顯示污染土壤可用來替代水泥原料中之黏土成分， 在達熟料三率值標準下， 替代比例為3%及7.6%。 於水泥製成中，當添加土壤量愈多， 可觀察到礦物相 C3S 之比例有下降的趨勢， 使凝結時間延長且抗壓強度降低，尤其以添加場址1之污染土壤更為顯著。 在溶出試驗中， 以EDTA-mediated TCLP 方法所產生的重金屬溶出量最高， 判定可以 EDTA 輔助TCLP 作為評估在較極端環境下之環境相容性。 依照水泥使用狀態來說， 鉻金屬溶出量於使用場址1土壤取代之水泥粉中可高達6.41 mg/L，超過規範標準， 而硬固水泥溶出量為4.17 mg/L，經水化作用後，溶出量低於標準，但仍存在風險，經推算每公斤之水泥最多能容納403 mg 之鉻金屬； 而使用場址2土壤取代之水泥成品，僅有少量鋅溶出，無使用之疑慮。 由此可知，適合替代水泥生料之材料主要取決於重金屬種類， 其次為添加比例。 在水泥 XRD 礦物相圖譜中，發現添加不同土壤會使水泥熔點提高並破壞 C3S 之生成，且推斷土壤中雜質中含鈉、磷會取代矽及鋁而破壞主要礦物相之生成。 重金屬污染土壤成分與水泥黏土原料相似， 且雜質含量相對較低， 初步評估除了含高濃度鉻之土壤外，受重金屬污染之土壤適合以水泥窯協同處理之方式進行循環利用， 同時兼顧污染處理與源頭採礦減量的目的。
計畫英文摘要	Due to improper disposal of hazardous substances, soils could be contaminated by heavy metals. In the cement industry, co-processing is considered as an effective way to reduce the cost and environmental footprints by replacing fuel or raw materials by wastes for cement production. However, co-processing of heavy metal contaminated soils is still limited. In this study, we investigate the co-processing of heavy metal contaminated soils in cement sintering for cement production. The soils collected from site 1 contained copper, zinc, and high concentrations of chromium. The soils collected from site 2 contained chromium, copper, lead, barium, zinc, and a high concentration of manganese which is not regulated. Through preliminary tests, the contaminated soils were allowed to replace clay component used as the cement raw materials, and the replacement ratio is 3% and 7.6% for site 1 and site 2, respectively. In the cement production, especially for soils collected from site 1, the proportions of C3S decreased with the increasing added soils, resulting in longer initial setting time and reduced compressive strength. The results in leaching tests showed that the concentrations of heavy metals in leachates using EDTA-mediated TCLP were the highest. EDTA-mediated TCLP could be potentially used to evaluate the environmental compatibility of produced cement under more stringent environmental conditions. The concentrations of chromium leached from cement produced using soils from site 1 could be as high as 6.41 mg/L, which exceeded the standard. After hydration, the leaching concentrations in cement mortar met the standard (4.17 mg/L), but the risks still existed. It was estimated that each kilogram of cement could hold 403 mg of chromium. The leaching of zinc in the cement produced using soils from site 2 was limited, suggesting its high environmental compatibility. It could be seen that the use of contaminated soils for cement production is determined by the heavy metals present and the soil addition ratio. In the XRD pattern of produced cement, it was found that soil additions would increase the cement melting point and interfere the formation of C3S. Hence, the metal-contaminated soils could be used for cement kiln co-processing, although attentions should be paid to those contain high concentrations of chromium. Overall, co-processing of heavy metal contaminated soils could limit the migration of heavy metals and reduce source mining in the cement industry.