플라즈마 용융방식으로 배출된 슬래그의 냉각방식에 따른 재료적 특성분석 및 재활용 방안 연구

Abstract

본 연구에서는 국내 최초로 플라즈마 토치를 사용한 재(Ash)용융설비에서 발생한 슬래그를 대상으로, 슬래그 배출시 새로운 냉각방법을 적용하여 기존의 냉각방법 슬래그보다 적용성 및 부가가치를 높일 수 있는 냉각방법을 제시하고, 재료적 특성분석 및 토공재료로의 재활용 가능성을 검토하여 향후 재활용 Process 개발에 적용 가능한 방향을 제시하고자 한다.; In this study, it is intended to suggest the cooling method that enables to improve the applicability and added value higher than existing slag by applying new cooling method at the time discharging slag that is produced from the ash melting system where the plasma torch is used for the first time in Korea, and suggest the applicative direction in the development of future recycling process by discovering its nature of material and applicative possibility as earthwork material. In this study, the ashes produced after the sewage sludge discharged from Y city was incinerated by the fluidized bed method was used as test materials. As result of XRF analysis, main ingredient of sewage sludge ashes was SiO2 (32%) besides CaO, Al2O3, Fe2O3 and so on. The basicity was approximately 0.8, and the amount of other additives was judged to be at minor level. As result of thermal analysis, the majority of weight reduction was finished at 800℃ or lower, while melting started near 1100℃. In this study, the ash having the property as above was melted at 1500℃ or higher using plasma melting method to have slag discharged. The slag discharged was cooled in granulated/air-cooled/powder cooling methods using the equipment such as XRD, SEM, etc. to review the nature of material. As result of XRD analysis, traditional diffuse pattern of glass could be found from granulated air-cooled slags, while a minor crystal phase could be observed from powder cooling slag, which possibly arises because the powder on the surface exists in the state not melted. As result of EDX analysis, it is deemed that powder ingredient has no change before and after it is used as cooling medium, and accordingly it is thought that the powder can be produced as the material where the function is added if used in different shape. In order to review the applicative possibility of glass (granulated, air-cooled)slag and powder cooling slag as an earthwork materials, compression and flexural strength were tested against the specimen. In result, it is deemed that the strength of glass (granulated, air-cooled) slag remarkably drops as the replacement ratio with aggregate increases, while the strength of powder cooling slag tends to increase as its replacement ratio increases. This is probably because the hardness of the powder cooling slag aggregate itself is higher than that of existing sand, and the reactive nature (hydraulic nature) of slag itself as well. As result of testing environment safety, leaching behavior appeared in the order of granulated slag, air-cooled slag and powder cooling slag, but the figures were detected at the reference value or less. The figure in the powder cooling slag showed relatively high, which probably was caused by the leaching from the powder not melted out on the surface. The characteristic of the powder cooling method applied for the first time in this test is that both the advantage of slag and the property of powder utilized as a cooling medium can be applied. For example, if a material with strong absorption is used, it can be used as the material where absorption property is added. In the mean time, if photo-catalyst is used, it can be applied as the material that manages self-decomposition of non-point source. If the research is carried out in future on the application of the property of powder combined with slag as well as the applicability of slag itself, it is thought that the development of the product having merit as a new material with higher applicability in recycling field beyond the boundary as the recycling method currently limited to the earthwork material only.