FactSage FToxid database was used for various solid and liquid oxide phases. Figure 3 shows the normalized Fe K-edge XANES spec- tra of the SFCA. FACTSAGE ™ thermo-equilibrium simulations of mineral transformations in coal combustion ash A.C. Collins I; C.A. Strydom I; J.C. Van Dyk I, II; J.R. Bunt I, III IChemical Resource Beneficiation, North-West University, South Africa IIAfrican Carbon Energy, South Africa IIISchool of Chemical and Mineras Engineering, North-West University, South Africa SYNOPSIS The aim of this investigation is to report on the influence of operating conditions, and of additives such as potassium carbonate, on the slagging behaviour of South African coal. This was done using a FACTSAGE ™ model that was previously developed to simulate the chemistry and mineral transformations occurring during a fixed-bed countercurrent gasification process. The mineral transformations in K- and Al-containing inorganic compounds under certain thermal conditions were tracked to see whether these species remain in the minerals or are captured by the slag. The main contributors to slag formation and possible inorganic mineral transformations were identified. The addition of potassium carbonate to the coal before thermal processing decreases the melt formation temperature and the melt percentage. The mineral transformations and slagging behaviour depend on the percentage of potassium in the sample, as well as the basic components present in the coal. Keywords: FACTSAGE ™, coal combustion, potassium, aluminium, slagging behaviour. Introduction Coal is a heterogeneous material (sedimentary rock) composed of organic and inorganic components. The chemical and physical properties of coal vary depending on the source of the coal, i.e. The age and geological environment in which the coal was formed (Oboirien et al., 2011; Yu, Lucas, and Wall, 2007). During gasification of coal, the organic matter partially decomposes (Kong et al., 2011); while mineral transformations occur (Song et al., 2009). Coal ash is thus a collection of mineral and non-mineral inorganic components that has undergone transformation as a result of thermal processing. The ash composition will depend on the organic and inorganic compounds present in the coal and/or any materials added to the coal prior to thermal processing (Kong et al., 2014). This specific composition of the sample, the organic and inorganic components, determines the mineral matter transformation and thus the slag characteristics (van Dyk, 2006). Mineral behaviour during thermal processing depends on: (i) The different types of minerals (modes of occurrence) and quantities present in the coal sample (Benson, Sondreal, and Hurley, 1995; Vassilev et al., 1995) (ii) The operating temperature (iii) The oxygen partial pressure in the atmosphere (Jak et al., 1998). When the coal is subjected to high temperatures (> 1100°C), melting and reactions of the component mineral matter occur, forming slag (Song et al., 2009). It is assumed that the slag composition depends on the minerals present in the coal, coupled with the operating conditions (Guo et al., 2014). In addition, the slagging behaviour of coal ash depends on the ash composition, i.e. The inorganic species present in the ash, as these minerals determine the ash fusion temperature (AFT) (van Dyk and Waanders, 2008). Consequently, the ash fusibility is generally expressed as a function of the content of principal oxides: SiO 2, Al 2O 3, TiO 2, Fe 2O 3, CaO, MgO, Na 2O, and K 2O (Seggiani, 1999). The AFT is determined by the modes (vapour, solid mineral grains) in which these elements occur in the ash. Although AFT is still widely used as a parameter for determining ash fusibility and melting characteristics of minerals (Jak et al., 1998), accurate results are difficult to obtain due to the complex composition of coal ash. Because of the complex nature of coal and the associated minerals, prediction of the mineral behaviour/transformation during thermal processing is a difficult task (Jak et al., 1998) when applying tradition methods (Hanxu et al., 2006). Latihan Soal UN SD Kelas 6 Lengkap Dengan Kunci Jawaban ~ Mei 2017 akan segera dilaksanakan sebuah ujian nasional serentak di seluruh indonesia, Diawali dari jenjang SMA sampai jenjang SD. Berbagai cara orangtua lakukan demi mempersiapkan anaknya agar mereka saat ujian dapat mengerjakan soal UN dengan lancar dan mendapatkan nilai yang baik. Jika ingin mengerjakan soal pilihan gandanya secara online dengan langsung ternilai secara online, silahkan dicoba: - > Soal Online Soal UTS Matematika Kelas 1 SD Semester 1 (Ganjil) Dan Kunci Jawaban. Soal mtk sd kelas 6.rar. FACTSAGE ™ simulation of the slagging process provides a means by which mineral behaviour/transformation towards equilibrium conditions can be predicted. It is an important tool that can be used to describe equilibrium ash properties, mineral transformation, behaviour of inorganic components, and the slagging tendency of coal ash at specific temperatures (van Dyk and Waanders, 2008), which can then be compared to experimental results. The modelling software was developed mainly for complex chemical equilibrium and process simulations, but can also be used to calculate and manipulate phase diagrams for minerals and mineral complexes (van Dyk et al., 2009).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |