Mineral melting behavior of chinese blended coal ash under gasification condition

Wu, Xiaojiang; Zhou, Tuo; Chen, Yushuang; Zhang, Zhongxiao; Piao, Guilin; Kobayashi, Nobusuke; Mori, Shigekatsu; Itaya, Yoshinori

doi:10.1002/apj.425

Cited by 24 publications

(16 citation statements)

References 25 publications

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“…It could be found from the comparison of the mineral composition between raw coal and semi-coke that orthoclase was present in raw coal, but not present in semi-coke, while sanidine is formed. Although the quartz and muscovite do not change, the characteristic peaks of quartz and muscovite in the pyrolysis semi-coke are significantly enhanced, indicating that there are increased contents of quartz and muscovite [44]. The decomposition of large amounts of volatile organic compounds during the pyrolysis process leads to the increases of the relative content of inorganic minerals.…”

Section: Minerals Transformation During Coal Pyrolysismentioning

confidence: 94%

Sequential Transformation Behavior of Iron-Bearing Minerals during Underground Coal Gasification

Zhang

et al. 2018

Minerals

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Detailed mineralogical information from underground coal gasification (UCG) is essential to better understand the chemical reactions far below the surface. It is of great scientific significance to study the mineral transformation and identify the typical minerals in certain process conditions, because it may help to ensure the stable operation of gasification processes and improve the utilization efficiency of coal seams. The transformation of iron-bearing minerals has the typical characteristics during the UCG process and is expected to indicate the process parameters. In this paper, UCG progress was subdivided into pyrolysis, reduction and oxidation stages, and the progressive coal conversion products were prepared. Two types of lignite with different iron contents, Ulankarma and Ulanqab coals, were used in this study. The minerals in the coal transformation products were identified by X-ray diffraction (XRD) and a scanning electron microscope coupled with an energy-dispersive spectrometer (SEM-EDS). The thermodynamic calculation performed using the phase diagram of FactSage 7.1 was used to help to understand the transformation of minerals. The results indicate that the transformation behavior of iron-bearing minerals in the two lignites are similar during the pyrolysis process, in which pyrite (FeS2) in the raw coal is gradually converted into pyrrhotite (Fe1−xS). In the reduction stage, pyrrhotite is transformed into magnetite (Fe3O4) and then changes to FeO. The reaction of FeO and Al2O3 in the low iron coal produces hercynite above 1000 °C because of the difference in the contents of Si and Al, while in the high iron coal, FeO reacts with SiO2 to generate augite (Fe2Si2O6). When the temperature increases to 1400 °C, both hercynite and augite are converted to the thermodynamically-stable sekaninaite.

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Section: Minerals Transformation During Coal Pyrolysismentioning

confidence: 94%

Sequential Transformation Behavior of Iron-Bearing Minerals during Underground Coal Gasification

Zhang

et al. 2018

Minerals

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“…It is considered that the sintering of impurities in Ofunato limestone occurs easier than in Kawara limestone with lower impurities. As shown in the XRD pattern, Ca2Al2SiO7 (gehlenite) is produced by the reaction of CaOAl2O32SiO2 (anorthite), Al2O3 and CaO during the decarbonization at 1573 K [24]. It can be presumed that the reaction starts from the surface of CaO particle [25,26] and then the gehlenite covers the surface of CaO particle to make it lose hydration reactivity.…”

Section: Effects Of Different Decarbonization Temperaturementioning

confidence: 99%

“…From the repeated hydration experiments, it is assumed that the negative effects of impurities on Ofunato CaO reactivity could be minimized by controlling the decarbonization temperature and time and the desirable decarbonization conditions can provide the high hydration reaction characteristics even if natural limestone such as Ofunato CaO containing some impurities. [24]. It can be presumed that the reaction starts from the surface of CaO particle [25,26] and then the gehlenite covers the surface of CaO particle to make it lose hydration reactivity.…”

Section: Effects Of Different Decarbonization Temperaturementioning

confidence: 99%

Possibility of Calcium Oxide from Natural Limestone Including Impurities for Chemical Heat Pump

Lai

Imai²,

Umezu³

et al. 2020

Energies

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Improving energy recycle is an important way to save energy resources and preserve the global environment. Chemical heat pump (CHP) is a technology for saving energy, which utilizes chemical reactions to store thermal energy such as waste heat and solar heat, then release it to provide heat for heating/cooling/refrigeration. For a practical CHP, it is necessary to find cheaper and more stable supply materials. In order to evaluate the possibility of calcium oxide from natural Ofunato natural limestone including impurities, we compare Ofunato limestone with Kawara natural limestone and Garou natural limestone from Japan. These calcium oxides worked as a reactant for CaO/H2O/Ca(OH)2 CHP by repeated hydration/dehydration reaction cycle experiments in a thermogravimetric analyzer. As a result, Ofunato CaO exhibits a high hydration reaction rate after decarbonization at 1223 K for 5 h. The reactivity increased by the repeated hydration reaction although the first hydration rate was low. Furthermore, the sintering of impurities in Ofunato limestone occur easier than that in Kawara limestone with lower impurities. The impurities adhered to the surface of the CaO particle to make specific surface area of CaO particle smaller, which could inhibit hydration reaction of CaO particle. Even if Ofunato limestone contains some impurities, it can be utilized as a raw material for chemical heat pumps.

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“…13,14 Entrained flow gasifiers adopt slag tapping, and in order to prevent the rapid increase of slag viscosity and the slag blockage caused by the temperature fluctuation in the gasifier, the operating temperature should be higher than the critical viscosity temperature (T cv ) of coal ash slag. 15,16 Commonly, the slag viscosity is required to be less than 25 PaÁs; otherwise, poor fluidity of slag may cause an unexpected shutdown of the gasifier. 17 The fusibility of coal ash and viscosity-temperature characteristics of slag are important parameters to estimate the fluidity of coal ash slag in entrained flow gasifier.…”

Section: Introductionmentioning

confidence: 99%

Study on the fluidity of ash slag of liquefaction solid product and lignite co‐gasification

Wang

Liu

Guo

et al. 2021

Asia-Pacific J Chem Eng

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The utilization of liquefaction solid product (LSP) obtained from fluidization reaction pyrolysis has become a pressing obstacle limiting the industrialization of coal liquefaction technology. In this work, gasification of LSP and Hami lignite coal (LC) and their blend at different ratios was investigated. In addition, the melt flow, mineral transformation, and crystallization behavior in the fusion process and cooling process were investigated. The results show that both LSP and LC are typical crystalline slags and cannot be applied to entrained flow gasification alone. The co-gasification of LC and LSP is a feasible method to improve their fluidity. At the ratio of 2:1 (LC to LSP), the blend has the lowest AFT. For molten slag, viscosity of the sample corresponded well to the structure of the slag. LC1:2LSP with higher Q 2 and Q 3 content showed a high viscosity, while LC1:2LSP with higher Q 0 and Q 1 content showed a lower viscosity. Besides, the size of the crystals generated during cooling is inversely proportional to the high-temperature viscosity of the sample, the migration of ions became difficult, and the growth of crystal size was inhibited at high viscosity. Meanwhile, the slag type of samples was influenced by the precipitated crystals. T cv can be effectively reduced by blending LC with LSP in a certain proportion. The results provide a theoretical basis for the utilization of LSP for the operation of entrained flow gasification.

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Mineral melting behavior of chinese blended coal ash under gasification condition

Cited by 24 publications

References 25 publications

Sequential Transformation Behavior of Iron-Bearing Minerals during Underground Coal Gasification

Sequential Transformation Behavior of Iron-Bearing Minerals during Underground Coal Gasification

Possibility of Calcium Oxide from Natural Limestone Including Impurities for Chemical Heat Pump

Study on the fluidity of ash slag of liquefaction solid product and lignite co‐gasification

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