제강 환원슬래그의 광물탄산화

The Mineral Carbonation Using Steelmaking Reduction Slag

제강 환원슬래그(steelmaking reduction slag)를 출발물질로 사용하여 다양한 농도의 H2SO4 , NH4NO3 (0.3, 0.5, 0.7, 1 M) 용액, 반응온도 100°C 와 150°C 의 조건에서 Ca 용출 및 탄산화 실험을 실시하였다. 양이온 용출과 탄산화 반응시간은 각각 2시간 및 1시간이었으며 탄산화 효율 증대를 위해 pH는 약 12로 조절하였고 CO2 의 부분압은 1 MPa이었다. TG 분석결과로부터 탄산화율을 계산한 결과, H 2 SO 4 0.5 M과 반응온도 150°C 의 실험 조건에서 약 86%의 고정화율이 관찰되었으나 이 이상의 농도에서는 탄산화율은 급격히 감소하였다. 그러나 NH4NO3 용액을 사용 한 결과, 산의 농도가 증가함에 따라 탄산화율도 비례적으로 증가하여 1 M 농도에서 약 93%의 탄산화율이 관찰되었다. 따라서 제강 환원슬래그를 사용한 탄산화반응은 H2 SO4 보다는 NH4NO3 용액을 사용할 경우 유리한 것으로 분석되 었다. SEM 분석결과, 합성된 아라고나이트는 나무토막 형태(wood piece shape), 둥근형태(round shape), 꽃모양 (flower shape)으로 관찰되었으며, 방해석은 결정면이 잘 발달된 능면체형(rhombohedral shape)의 전형적인 형태로 확인되었다.

Mineral carbonation for the storage of carbon dioxide is a CCS option that provides an alternative for the more widely advocated method of geological storage in underground formation. Carbonation of magnesium- or calcium-based minerals, especially the carbonation of waste materials and industrial by-products is expanding, even though total amounts of the industrial waste are too small to substantially reduce the CO2 emissions. The mineral carbonation was performed with steelmaking reduction slag as starting material. The steelmaking reduction slag dissolution experiments were conducted in the H2 SO4 and NH4 NO3 solution with concentration range of 0.3 to 1 M at 100°C and 150°C. The hydrothermal treatment was performed to the starting material via a modified direct aqueous carbonation process at the same leaching temperature. The initial pH of the solution was adjusted to 12 and CO2 partial pressure was 1MPa for the carbonation. The carbonation rate after extracting Ca2+ under NH4 NO3 was higher than that under H2 SO4 and the carbonation rates in 1M NH4 NO3 solution at 150°C was dramatically enhanced about 93%. In this condition well-faceted rhombohedral calcite, and rod or flower-shaped aragonite were appeared together in products. As the concentration of H2 SO4 increased, the formation of gypsum was predominant and the carbonation rate decreased sharply. Therefore it is considered that the selection of the leaching solution which does not affect the starting material is important in the carbonation reaction.