以水泥窯協同處理再生重金屬污染土壤生產水泥之研究

Reutilization of Heavy Metal Contaminated Soils for Cement Production by Cement Kiln Co-processing

張正欣(Jheng-Shin Chang)

指導教授 ： 林逸彬

國立臺灣大學/工學院/環境工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202101310

摘要

水泥窯協同處理(co-processing)利用廢棄物替代部分的製程燃料或水泥原料，可降低生產成本減少環境負荷並處理有害廢棄物。本研究添加兩種重金屬(場址1及場址2)污染土壤，取代原料配比，以0、3、7.6和10 wt.% 製作水泥，分析其工程特性，並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)、EDTA輔助TCLP (EDTA-mediated TCLP)溶出程序以及再生粒料溶出程序(RALP)檢測重金屬趨勢。
經由成分分析，污染土壤可替代水泥原料中之黏土。特性分析結果顯示當添加土壤量愈多，礦物相Ca3SiO5 (C3S)之比例有下降的趨勢，Ca2SiO4 (C2S)反之上升，使凝結時間延長且抗壓強度降低，尤其以添加高濃度之鉻污染土壤更為顯著。TCLP試驗中，添加量超過7.6%場址1的水泥粉之鉻溶出濃度超出事業廢棄物溶出標準，而添加量10%的硬固水泥之鉻溶出濃度仍符合溶出標準，添加10%場址2的水泥粉及硬固水泥之鉻溶出量皆符合標準。此外，EDTA輔助TCLP相較於TCLP有更高的鉻溶出量。RALP試驗結果顯示所有水泥皆可做為控制性低強度回填材料(CLSMs)。在本研究之添加比例下，以3 wt.% 場址1及10 wt.% 場址2污染土壤添加製作之水泥，可符合工程特性要求並兼具環境相容性。由經濟分析可知，水泥業者及污染行為人可藉由水泥窯協同處理獲得可觀的經濟效益。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，同時兼顧污染處理並降低傳統水泥生產之環境及經濟成本。

關鍵字

重金屬污染土壤 ； 水泥窯協同處理 ； 環境相容性 ； 經濟分析

並列摘要

Co-processing is considered as an effective way to reduce the cost and environmental footprints for cement production by replacing fuel or raw materials with wastes. In this study, we investigated the influences of co-processing of two heavy metal-contaminated soils (Site 1 and Site 2) in cement kiln on the engineering integrity and heavy metal leachability of cement powders and cement mortars. The replacements of the contaminated soil were set at 0, 3, 7.6, and 10 wt.%. Engineering integrity of the cement products was verified using typical performance tests first, followed by three heavy metal leaching tests, namely Toxicity Characteristic Leaching Procedure (TCLP), EDTA-mediated TCLP and Synthetic Precipitation Leaching Procedure (SPLP). The results showed that in TCLP, only Cr was the concern, in which leachates of cement powders produced by co-processing with > 7.6% site 1 soils exceeded the TCLP Cr limit (5 mg/L), whereas all leachates of cement mortars met the regulations. EDTA-mediated TCLP could potentially release higher Cr concentrations, indicating that cautions were still needed when applying the cement products in harsh environments. It was determined that co-processing of 3 wt.%. site 1 and of 10 wt.%. site 2 soils could satisfy the engineering integrity and TCLP standards. Preliminary economic assessment indicated that using co-processing to treat heavy metal-contaminated soils can bring benefits for both cement industry and soil polluter and could be an attractive alternative for the remediation of heavy metal contaminated soil.

並列關鍵字

heavy metal-contaminated soil ； cement kiln ； co-processing ； environmental compatibility

參考文獻

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