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Pyrometallurgical Process for Recycling of Valuable Materials and Waste Management: Valorisation Applications of Blast Furnace Slags
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Sara Yasipourtehrani, Vladimir Strezov, Tim Evans, Hossain Md Anawar
There are different crystalline phases for BFS after heat treatment, such as merwinite, melilite, larnite, gehlenite, and åkermanite (Fredericci et al., 2000). Merwinite (Ca3 Mg (SiO4)2) is a metastable phase of BFS and it forms at 1000°C. Through further heating, merwinite irreversibly disappears to the thermodynamically stable phase. Melilite, which is another crystalline phase, includes all principal components of BFS and 10wt% Al2O3. Larnite (Ca2SiO4) is a slag with more SiO2 and CaO than is needed to form åkermanite (2CaO.MgO.2SiO2) and gehlenite (2CaO.Al2O3.SiO2), which are known as the melilite series. Melilite is a solid solution between gehlenite and akermanite. The excess CaO and SiO2 is sufficient to form calcium silicate (Fredericci et al., 2000). Eisenhuttenleute (1995) produced a slag atlas and discussed presented different characteristic compositions of BFS in two systems of CaO-SiO2-Al2O3 and CaO-SiO2-MgO. Melilite is a solid solution of åkermanite (Ca2MgSi2O7) and gehlenite (Ca2Al2SiO7) (Mendybaev et al., 2006). Melilite consists of åkermanite and gehlenite and produces interrupted solid solution. When the amount of Al2O3 increases the gehlenite phase will be obtained, but when the amount of MgO is increased the åkermanite phase will be obtained.
Cementing components
Published in Caijun Shi, Pavel V. Krivenko, Della Roy, Alkali-Activated Cements and Concretes, 2003
Caijun Shi, Pavel V. Krivenko, Della Roy
A slow cooling of slag melts leads to a stable solid, which consists of crystalline Ca−Al−Mg silicates. Melilite - a solid solution of gehlenite C2AS and akermanite C3MS2− is the most common mineral. Of course, the mineral composition of a slowly cooled slag is determined by its chemical composition, as indicated in the CaO−MgO−Al2O3−SiO2 phase diagram in Figure 3.2. These minerals, which are often identified in slowly cooled slag, are summarized in Table 3.3. The only crystalline compound in slowly
Investigation on the effect of MgO content on the crystallization behavior of synthetic BF slag
Published in Materials and Manufacturing Processes, 2018
Qian-Qian Ren, Yu-Zhu Zhang, Yue Long, Zong-Shu Zou, Shao-Sheng Chen, Jie Li
As shown in Figure 3b and c, the crystal phases of the synthetic BF slag primarily consisted of gehlenite and akermanite at a temperature of 1100°C. There was a little deviation with regard to the peaks of gehlenite and akermanite; this indicates that the gehlenite and akermanite formed a solid solution, melilite, during the cooling process. The peaks of anorthite and clinopyroxene were observed at a temperature of 1000°C; however, they could hardly be observed at a temperature of 1100°C. The peaks of wollastonite could not be observed within the XRD patterns, indicating that the wollastonite was not crystallized when the MgO contents were 10 and 12%; this corresponds to the results of FactSage simulation. The spinel phase was not detected within the XRD patterns of the sample with the MgO content of 12%. It is possible that there was an insufficient amount of spinel present to allow detection. It can be concluded that melilite was first precipitated during the cooling process, which governed the initial crystallization temperature of the synthetic BF slag; this corresponds to the results of FactSage simulation. Qin et al.[22] and Kashiwaya et al.[23] investigated the mineralogical compositions of BF slag using XRD and SEM analyses. They showed that the major components of BF slag were gehlenite, merwinite, and akermanite, similar to the results obtained in this work. The crystallized phases observed in the XRD patterns corresponded to the results of FactSage simulation. Therefore, it is feasible to simulate the mineralogical composition of slag using FactSage thermodynamic software.
The technology of CO2 sequestration by mineral carbonation: current status and future prospects
Published in Canadian Metallurgical Quarterly, 2018
F. Wang, D. B. Dreisinger, M. Jarvis, T. Hitchins
Santos et al. [88] researched the direct MC by steel slags which were intensified by ultrasound. They also showed that sonication can facilitate the MC reaction by removing the passivation layers of generated carbonates and silica as well as reduce the particle size obviously. Araizi et al. [92] have done the research where the direct MC by three kinds of alkaline waste residues, air pollution control residues, cement bypass dust and ladle slag, were enhanced by ultrasound. They verified that the application of ultrasound can considerably promote the carbonation efficiency but needed high L/S ratios (50–100). Huijgen et al. [81] also believed that steel slag was suitable for the MC. Kasina et al. [87] tried to use blast furnace and steel-making slags to sequester CO2 through the direct MC route. They discovered that steel-making slag was much easier to sequester CO2 into carbonates than blast furnace slag because of the different mineral compositions. The majority of minerals of the blast furnace slag were the melilite group minerals, which were much less reactive than the dicalcium silicates and calcium ferrites in the steel-making slags at the same conditions. Su et al. [89] utilised a basic-oxygen furnace (BOF) slag to sequester CO2 by the direct MC as well. However, they claimed that BOF slag was a better CO2 storage medium. Meanwhile, the valuable vanadium and chromium metals were released into solution during the MC. Polettini et al. [90] analysed in detail the effects of particle size on the MC by BOF slag. They found the effect was considerable. Particularly, the carbonation efficiency difference between the particle size of D50 = 44 μm and D50 = 88 μm was over 60% (approximately 72 and 8%, respectively) at the same conditions, whereas when D50 = 17 μm, the carbonation efficiency decreased to only 44% again. They have the consistent conclusions with Nyambura et al. [84] in terms of the important of particle size.
An overview of alternative raw materials used in cement and clinker manufacturing
Published in International Journal of Sustainable Engineering, 2021
Sabah Ahmed Abdul-Wahab, Hilal Al-Dhamri, Ganesh Ram, Vishnu P. Chatterjee
Various phases are present in the slag including glass (supercooled liquid silicates), semi-glass, quartz, Ca-rich silicates, aluminosilicates, the presence of modified C3S and C2S phases, and in melilite, gehlenite, akermanite, merwinite, rankinite, pseudo wollastonite, monticellite, oldhamite, anorthite, forsterite, perovskite, spinel, etc. in minor amounts (Yildirim and Prezzi 2011).