The melting temperature of Z coal ash was reduced by adding calcium–magnesium compound flux(WCaO/WMgO=1). In the process of simulated coal gasification, the coal ash and slag were prepared. The transformation of mine...The melting temperature of Z coal ash was reduced by adding calcium–magnesium compound flux(WCaO/WMgO=1). In the process of simulated coal gasification, the coal ash and slag were prepared. The transformation of minerals in coal ash and slag upon the change of temperature was studied by using X-ray diffraction(XRD). With the increase of temperatures, forsterite in the ash disappears, while the diffraction peak strength of magnesium spinel increases,and the content of the calcium feldspar increases, then the content of the amorphous phase in the ash increases obviously. The species and evolution process of oxygen, silicon, aluminum, calcium, magnesium at different temperatures were analyzed by X-ray photoelectron spectroscopy(XPS). The decrease of the ash melting point mainly affects the structural changes of silicon, aluminum and oxygen. The coordination of aluminum and oxygen in the aluminum element structure, e.g., tetracoordinated aluminum oxide, was changed. Tetrahedral [AlO4] and hexacoordinated aluminoxy octahedral [AlO6] change with the temperature changing. The addition of Ca2+ and Mg2+ destroys silica chain, making bridge oxide silicon change into non-bridge oxysilicon;and bridge oxygen bond was broken and non-bridge oxygen bond was produced in the oxygen element structure. The addition of calcium and magnesium compound flux reacts with aluminum oxide tetrahedron, aluminum oxide octahedron and silicon tetrahedron to promote the breakage of the bridge oxygen bond. Ca2+ and Mg2+ are easily combined with silicon oxide and aluminum oxide tetrahedron and aluminum. Oxygen octahedrons combine with non-oxygen bonds to generate low-melting temperature feldspars and magnesite minerals, thereby reducing the coal ash melting temperatures. The structure of kaolinite and mullite was simulated by quantum chemistry calculation, and kaolinite molecule has a stable structure.展开更多
与传统的煤炭开发利用技术相比,煤炭地下气化被誉为“绿色采煤技术”,但其潜在的地下水污染风险不利于该技术的推广应用。基于地下水对燃空区气化残留物的浸淋是造成地下水污染的原因之一,气化残留物的组成、孔结构等物化性质一定程度...与传统的煤炭开发利用技术相比,煤炭地下气化被誉为“绿色采煤技术”,但其潜在的地下水污染风险不利于该技术的推广应用。基于地下水对燃空区气化残留物的浸淋是造成地下水污染的原因之一,气化残留物的组成、孔结构等物化性质一定程度上影响残留物中有害物质的溶出及污染地下水的吸附净化等实际,借助自建的煤炭地下气化模拟试验系统,采用富氧/水蒸气两阶段气化方法完成焦作无烟煤气化试验并收集“三带”残留物。采用SEM、低温氮吸附仪、XRD和FTIR等分析手段对残留物的表面形貌、孔隙结构及表面官能团等物化性质进行研究。结果表明:氧化带残留物主要为灰渣,还原带残留物主要为气化残焦,干馏干燥带主要为热解半焦。还原带残留物的孔隙发达,其比表面积和孔容分别可达56.43 m 2/g和0.031 cm 3/g;干馏干燥带残留物的比表面积和孔容分别为15.65 m 2/g和0.014 cm 3/g;与还原带和干馏干燥带残焦相比,氧化带残留物的比表面积和孔容积较小,石英、莫来石是其主要矿物组分。还原带和干馏干燥带残焦具有类石墨微晶结构,同时可能含有酚羟基氧或醚氧等含氧基团。残留物的组成和结构对其所含有害物质在地下水中的溶出有一定贡献,同时也使其具有一定的吸附潜力,研究结果为了解并掌握气化残留物中污染物的溶出迁移特点及残留物对污染地下水的吸附净化规律奠定基础,丰富了煤炭地下气化地下水污染及其防控理论,也有助于该技术的应用推广。展开更多
基金Supported partially by the Major Science and Technology Special Projects Foundation of Anhui Province(15czz02045)the Natural Science Foundation of Anhui Province(1508085MB41)the China Postdoctoral Science Foundation(2015M571915)
文摘The melting temperature of Z coal ash was reduced by adding calcium–magnesium compound flux(WCaO/WMgO=1). In the process of simulated coal gasification, the coal ash and slag were prepared. The transformation of minerals in coal ash and slag upon the change of temperature was studied by using X-ray diffraction(XRD). With the increase of temperatures, forsterite in the ash disappears, while the diffraction peak strength of magnesium spinel increases,and the content of the calcium feldspar increases, then the content of the amorphous phase in the ash increases obviously. The species and evolution process of oxygen, silicon, aluminum, calcium, magnesium at different temperatures were analyzed by X-ray photoelectron spectroscopy(XPS). The decrease of the ash melting point mainly affects the structural changes of silicon, aluminum and oxygen. The coordination of aluminum and oxygen in the aluminum element structure, e.g., tetracoordinated aluminum oxide, was changed. Tetrahedral [AlO4] and hexacoordinated aluminoxy octahedral [AlO6] change with the temperature changing. The addition of Ca2+ and Mg2+ destroys silica chain, making bridge oxide silicon change into non-bridge oxysilicon;and bridge oxygen bond was broken and non-bridge oxygen bond was produced in the oxygen element structure. The addition of calcium and magnesium compound flux reacts with aluminum oxide tetrahedron, aluminum oxide octahedron and silicon tetrahedron to promote the breakage of the bridge oxygen bond. Ca2+ and Mg2+ are easily combined with silicon oxide and aluminum oxide tetrahedron and aluminum. Oxygen octahedrons combine with non-oxygen bonds to generate low-melting temperature feldspars and magnesite minerals, thereby reducing the coal ash melting temperatures. The structure of kaolinite and mullite was simulated by quantum chemistry calculation, and kaolinite molecule has a stable structure.
文摘与传统的煤炭开发利用技术相比,煤炭地下气化被誉为“绿色采煤技术”,但其潜在的地下水污染风险不利于该技术的推广应用。基于地下水对燃空区气化残留物的浸淋是造成地下水污染的原因之一,气化残留物的组成、孔结构等物化性质一定程度上影响残留物中有害物质的溶出及污染地下水的吸附净化等实际,借助自建的煤炭地下气化模拟试验系统,采用富氧/水蒸气两阶段气化方法完成焦作无烟煤气化试验并收集“三带”残留物。采用SEM、低温氮吸附仪、XRD和FTIR等分析手段对残留物的表面形貌、孔隙结构及表面官能团等物化性质进行研究。结果表明:氧化带残留物主要为灰渣,还原带残留物主要为气化残焦,干馏干燥带主要为热解半焦。还原带残留物的孔隙发达,其比表面积和孔容分别可达56.43 m 2/g和0.031 cm 3/g;干馏干燥带残留物的比表面积和孔容分别为15.65 m 2/g和0.014 cm 3/g;与还原带和干馏干燥带残焦相比,氧化带残留物的比表面积和孔容积较小,石英、莫来石是其主要矿物组分。还原带和干馏干燥带残焦具有类石墨微晶结构,同时可能含有酚羟基氧或醚氧等含氧基团。残留物的组成和结构对其所含有害物质在地下水中的溶出有一定贡献,同时也使其具有一定的吸附潜力,研究结果为了解并掌握气化残留物中污染物的溶出迁移特点及残留物对污染地下水的吸附净化规律奠定基础,丰富了煤炭地下气化地下水污染及其防控理论,也有助于该技术的应用推广。
