高温通水反応装置による灰長石を多く含む凝灰質砂岩とpH3.8のCO_2溶解水との溶解, 沈殿実験

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To evaluate the influence of rock properties on the geological sequestration of carbon dioxide, laboratory flow-through experiments were performed under 80 °C for 65 days by a permeability test machine. This technique enables to estimate the dissolution rate and dissolution time of rocks by the interaction with CO2 dissolved solution. This experiment uses two solutions, a pH 3.8-, CO2 0.107 mol/L dissolved-solution (CO2 undersaturated solution) and another with pH 6.4 distilled water. These solutions are independently passed through rock samples, using samples of tuffaceous sandstone including 32% unweathered anorthite collected at Yoichi, Hokkaido. Si, Ca, Mg, K, and Na ions are progressively dissolved to keep the time for 20 hours after increasing temperature at 80 °C with CO2 dissolved solution. After the initial reaction, ion concentrations decrease and became a constant dissolution state. In contrast, these elements, except for Si hardly dissolve under the freshwater flow-through conditions at 80 °C for 65 days. The surface area of rock increased for that of the starting material and many pits with diameters of about 0.5 μm were made and a 0.1 μm thick Si-rich layer was made only on the anorthite surface by reaction with the CO2 dissolved solution. The hydraulic conductivity of the rock did not change during 65 days in contact with the rock-CO2 dissolved solution and-distilled water. The Ca dissolution rate was calculated to be 7.4×10-17 mol/cm2/sec under the CO2 system, which is definitely greater than with the freshwater system: 3.7×10-18 mol/cm2/sec. The Si dissolution rate of the tuffaceous sandstone under the freshwater system: 8.5×10-17 mol/cm2/sec was almost the same under the CO2 system: 1.9×10-16 mol/cm2/sec. The dissolution time of Si from 1g of the tuffaceous sandstone mass containing 51 wt% of SiO2 was calculated to be 2.4 years. The dissolution time of Ca would be 1.2 years under the CO2 system and 322 years under the freshwater system from 1g of the rock containing 0.92 wt% of CaO. The interaction with the CO2 dissolved dilute solution and rocks obviously forms many ions including solution to contact rock and minerals at early reaction.
2009-09-30

高温通水反応装置による灰長石を多く含む凝灰質砂岩とpH3.8のCO_2溶解水との溶解, 沈殿実験

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