| Abstract |
| This study developed a pilot-scale CO2 supersaturation system using water as a solvent and investigated CO2 dissolution characteristics under different pH conditions. The system was operated by pressurizing the feed water to 8.0 ± 1.5 kgf/cm² using a multistage pump, injecting CO2 gas through an injector, and maintaining a pressure of 3.0 ± 1.0 kgf/cm² in a pressurized tank. Total dissolved CO2 (TDC) concentrations were measured while varying the pH of the circulating water (unadjusted, 5.0, 6.0, and 7.0). After 30 min of operation, TDC concentrations reached 3,006 mg/L as CO2 at unadjusted pH, 3,303 mg/L at pH 5.0, 4,272 mg/L at pH 6.0, and 4,058 mg/L at pH 7.0. These values correspond to approximately 278-295 % supersaturation relative to the theoretical CO2 saturation concentration (1,449 mg/L) under pH conditions above 6.0. When operated for 180 min at pH 7.0, the maximum TDC reached 10,115 mg/L after 150 min, representing approximately 698 % supersaturation. The TDC increased linearly at an average rate of 1,000 mg/L per 15 min for the first 90 min. At pH values below 6.0, operating pressure decreased from 7.0 ± 1.0 kgf/cm² to 2.0-4.0 kgf/cm² due to degassing of dissolved CO2 in [H2CO3*] form, whereas stable operation was achieved at pH 7.0 or higher, where CO2 predominantly exists as [HCO3-]. After cessation of operation, TDC remained at 9,728 and 9,532 mg/L after 1 and 2 days, respectively, corresponding to retention rates of 94-96 %. Comparable TDC levels were achieved regardless of raw water source, confirming practical applicability. This study identifies optimal operating conditions (pH ≥ 7.0, 150 min) for water-based CO2 supersaturation and demonstrates its potential for applications such as mineral carbonation and carbon-capturing concrete mixing water. |
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| Key Words |
| Carbon capture, CO2 supersaturation, pH control, Solubility, Total Dissolved CO2 탄소포집, CO2 과포화, pH 조정, 용해, 총용존CO2 |
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