- 學位論文
連續萃取法對岩石二氧化碳地質封存潛勢評估初探
Preliminary Study of Rocks Carbon Dioxide Geological Storage to Assess Potential Using BCR Sequential Extraction Procedure
摘要
因應全球氣候變遷，人為活動以及工業活動所排放的二氧化碳氣體日趨漸增，地質封存二氧化碳開始有其需求，為了緩解日趨漸高濃度的二氧化碳，在大氣中的碳捕獲和儲存（CCS）技術正逐步成為減少溫室氣體排放的一個重要概念。在IPCC報告中對於CCS利用地質構造的二氧化碳封存機制可以大致分為結構、地層、水力和地球化學方式。地球化學捕獲二氧化碳被認為是一個相對穩定並且有效和安全性永久儲存於地層之中，進一步也增加封存二氧化碳的體積。注入的二氧化碳可以隨著孔隙流體和儲層岩石相互作用並且礦化形成礦物。它來評估儲層岩石的能力抵扣二氧化碳是非常重要的。 本研究使用彰濱工業區火力發電計畫廠址所採集岩心樣本進行BCR連續萃取法實驗（Sequential extraction procedure, formerly the Community Bureau of Reference），BCR連續萃取法利用萃取液對於岩石中三個相態進行萃取，分為可交換相和碳酸鹽（第一階段）、氧化態（第二階段）和還原態（第三階段）萃取。多階段萃取後的水樣溶液使用感應耦合電漿質譜儀（ICP-MS）進行微量元素、稀土元素進行元素分析，並且對於溶出之元素及礦物相進行探討。固體樣本部分，選取兩樣本各階段固體乾燥樣本使用螢光光譜分析儀（XRF）分析固體樣本中的主要元素組成。經由萃取結果顯示，鈣和鐵為最主要被萃取出的離子，其餘陽離子萃取量過低則可以忽略不計。第一階段萃取過程包含碳酸鹽態，而碳酸鹽態所釋放的陽離子並無礦化能力，藉由主成份分析去除掉XRF分析結果中第一階段所萃取出的鈣離子。最終所得結果，頁岩層在三個相態中每公斤樣本分別可以消耗0.13 公克、23.79公克和4.19公克的二氧化碳。另一方面，上部的砂岩分別在三個相態之中每公斤樣本消耗0.50 公克、7.34克和5.66克的二氧化碳。因此，頁岩相較於砂岩具有較高的封存量，再考慮地層中還原態物質較具有礦化之潛勢，以及地層孔隙率計算後，本研究地層之礦化量砂岩及頁岩分別為5.95 g/kg及1.84 g/kg。此外，本實驗萃取過程中並無明顯來自於長石溶解所釋出的離子。
並列摘要
To relief the high concentration of carbon dioxide in the atmosphere, carbon capture and storage (CCS) is gradually becoming an important concept to reduce greenhouse gas emissions. In IPCC Special Report on CCS, the storage mechanisms for geological formations are categorized into structural/stratigraphic, hydrodynamic and geochemical trappings. Geochemical trapping is considered as a storage mechanism, which can further increase storage capacity, effectiveness and security in terms of permanent CO2 sequestration. The injected CO2 can have geochemical interactions with pore fluid and reservoir rocks and transform into minerals. It is important to evaluate the capacity of reservoir rock for sequestrating CO2. In this study, sedimentary rock samples were collected from Midwestern Taiwan; and, the BCR sequential extraction experiments developed by European Union Measurement and Testing Programme were conducted. BCR was designed for extracting three major phases from soil, including exchangeable phase and carbonates (the first stage), reducible phase (the second stage) and oxidizable phase (the third stage). The chemistry of extracted solutions and rock residues were measured with ICP-MS and XRF, respectively. According to the results of XRF analysis, considerable amounts of calcium and iron can be extracted by BCR procedures but other cations are negligible. Using principal component analysis on the results of XRF analysis, the extracted calcium in the first stage was released by calcite dissolution and should not be counted for sequestration capacity. Conclusively, the extracted cations in three stages extractions can mineralized CO2 of 0.13 g, 23.79 g and 4.19 g per 1 kg shale, respectively. On the other hand, a sandstone of 1 kg can release cations in three extraction stages to mineralize CO2 of 0.50 g, 7.34 g and 5.66 g. Accordingly, shale has a higher capacity of CO2 sequestration than sandstone. To account for the porosity of reservoir host rock, the total sequestration capacity would become 5.95g per 1 kg shale and 1.84g per 1kg sandstone. However, it should be noted that the calculated sequestration capacity did not include the dissolution of feldspar.