System development of CO2 capture and sequestration by forming sodium carbonate gel in shallow aquifers

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K21163
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 31:Nuclear engineering, earth resources engineering, energy engineering, and related fields
• Research Institution: Institute for Future Engineering (2021-2022); Kyushu University (2020)
• Principal Investigator: Sasaki Kyuro 公益財団法人未来工学研究所, 研究センター, 研究員 (60178639)
• Co-Investigator(Kenkyū-buntansha): NGUELE RONALD 九州大学, 工学研究院, 助教 (50821401)
• Project Period (FY): 2020-07-30 – 2023-03-31
• Keywords: 二酸化炭素固 / ケイ酸ナトリウム / 浅帯水層 / CO2地中貯留 / ゲル / ダイレクトダンピング

Outline of Final Research Achievements

In this study, we have investigated the mass balance, Raman spectroscopic analysis results, and SEM-EDS spectroscopy of sodium carbonate (Na2CO2) gel formed by bubbling CO2 gas into sodium metasilicate (Na2SiO3) aqueous solution under subcritical pressure conditions. We collected and summarized the measurement results and basic chemical reactions on the gel formation, and searched the practical and optimal gel formation conditions. As a result, it was clarified that the formation of sodium carbonate gel was practical with an aqueous solution concentration of 1 to 7% and a pressure of 7 MPa or less. Furthermore, regarding the separation and recovery rate of CO2 gas and the configuration and feasibility of the injection system, we have proposed the specifications of the formation plant and injection well and facility for direct sodium carbonate gel injection and sequestration in the shallow aquifer.

Free Research Field

地球資源システム工学

Academic Significance and Societal Importance of the Research Achievements

安価なメタケイ酸ナトリウム水溶液に亜臨界圧条件下でCO2ガスを溶解させることで炭酸ナトリウムゲルが容易に生成され減圧後も安定であることから、深帯水層に匹敵する貯留ポテンシャルを持つ300-400mの浅帯水層にCO2を安全に固定できると着想した。また、炭酸ナトリウムゲル自体は自然界にも存在する化合物であり、深帯水層でのCO2貯留の場合には地下微生物が激減する苛酷な酸性環境となるのに比較して、ゲル層は良好な涵養環境(pH=9-10)であるため、微生物による鉱物固定化などが促進され、CO2の大気放出量の削減による地球温暖化の抑制に貢献できる。