title: CO2 sequestration utilizing basic-oxygen furnace slag: Controlling factors, reaction mechanisms and V-Cr concerns.
abstract: Basic-oxygen furnace slag (BOF-slag) contains >35% CaO, a potential component for CO2 sequestration. In this study, slag-water-CO2 reaction experiments were conducted with the longest reaction duration extending to 96hr under high CO2 pressures of 100-300kg/cm(2) to optimize BOF-slag carbonation conditions, to address carbonation mechanisms, and to evaluate the extents of V and Cr release from slag carbonation. The slag carbonation degree generally reached the maximum values after 24hr slag-water-CO2 reaction and was controlled by slag particle size and reaction temperature. The maximum carbonation degree of 71% was produced from the experiment using fine slag of ≤0.5mm under 100°C and a CO2 pressure of 250kg/cm(2) with a water/slag ratio of 5. Vanadium release from the slag to water was significantly enhanced (generally >2 orders) by slag carbonation. In contrast, slag carbonation did not promote chromium release until the reaction duration exceeded 24hr. However, the water chromium content was generally at least an order lower than the vanadium concentration, which decreased when the reaction duration exceeded 24hr. Therefore, long reaction durations of 48-96hr are proposed to reduce environmental impacts while keeping high carbonation degrees. Mineral textures and water compositions indicated that Mg-wüstite, in addition to CaO-containing minerals, can also be carbonated. Consequently, the conventional expression that only considered carbonation of the CaO-containing minerals undervalued the CO2 sequestration capability of the BOF-slag by ~20%. Therefore, the BOF-slag is a better CO2 storage medium than that previously recognized.
authors.affiliation: Department of Earth Sciences, "National" Cheng-Kung University, Tainan 70101, Chinese Taipei.
authors.forename: Tung-Hsin
authors.initials: TH
authors.lastname: Su
authors.affiliation: Department of Earth Sciences, "National" Cheng-Kung University, Tainan 70101, Chinese Taipei. Electronic address: hjyang@mail.ncku.edu.tw.
authors.forename: Huai-Jen
authors.initials: HJ
authors.lastname: Yang
authors.affiliation: Department of Marine Biotechnology and Resources, "National" Sun Yat-Sen University, Kaohsiung 80424, Chinese Taipei.
authors.forename: Yen-Hong
authors.initials: YH
authors.lastname: Shau
authors.affiliation: Department of Geology, Niigata University, 8050, Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Takazawa
authors.affiliation: China Steel Corporation, 1, Chung-Kang Rd., Kaohsiung 81233, Chinese Taipei.
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Lee
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D057965:Carbon Sequestration; D006358:Hot Temperature; D007220:Industrial Waste / Q000032:analysis*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D002245:Carbon Dioxide; D010100:Oxygen
keywords: BOF-slag; Carbonation; Mineral CO(2) sequestration