The crystal structure of coal char and the mineral transformation of coal ash during coal conversion under pressurized conditions
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摘要: 利用高温高压管式炉结合X射线衍射仪(XRD)和傅里叶红外光谱分析(FT-IR)研究了不同压力下(0.1-6 MPa)热解煤焦矿物相和碳微晶结构以及燃尽煤灰矿物相的演变规律。结果表明,在矿物相转化上,压力的升高对煤焦矿物相种类影响较小;在微晶结构上,温度和压力的升高使得焦炭的芳香层片堆叠高度变大,石墨化程度加深;在官能团特征上,压力对于煤焦中有机官能团结构的影响有限。压力变化对煤灰中主要矿物相种类的影响较小,但对其相对含量有一定影响,主要原因是不同压力下煤粉着火机理的转变造成燃烧温度有所不同;温度对煤灰物相转化的影响相较于压力更显著。Abstract: The influence of pressure (0.1-6 MPa) on the mineral phase of coal char and the carbon crystal structure and the mineral conversion of coal ash were investigated by using the tube furnace at higher temperature and pressure combined with the analysis of X-ray diffractometer (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The results indicate that the mineral phase of coal char is not significantly affected by the pyrolysis pressure; while, the average stacking height or the graphitization degree of coal char increases with increasing the temperature and pressure. With respect to functional groups, the pressure has little effect on the structure of organic functional group. Also, it is found that the pressure has little effect on the main mineral phases of coal ash, but it can affect the relative contents of mineral phases, which is mainly due to the varying of combustion temperatures caused by the transition of the ignition mechanism at different pressures. The effect of temperature on the mineral transformation is more significant than that of pressure.
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Key words:
- char /
- ash /
- mineral phase /
- crystal structure /
- organic functional group /
- high temperature and high pressure
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表 1 实验所用煤样的煤质分析
Table 1 Properties of pulverized coal sample
Proximate analysis wad/% Ultimate analysis wad/% M A V FC C H N S O 2.3 35.4 21.7 40.6 50.04 3.18 0.57 0.30 8.22 Ash composition w/% Al2O3 SiO2 CaO Fe2O3 MgO TiO2 SO3 K2O Na2O P2O5 25.1 58.6 4.47 5.03 1.42 1.17 0.461 2.29 0.678 0.324 表 2 1000 ℃不同压力下煤焦微晶结构参数
Table 2 Crystallite structure parameters of coal char under different pressures at 1000 ℃
Pressure Diffraction angle /(°) Microcrystalline
structure parameters
/10-1 nm002 peak 100 peak d Lc La 0.1 MPa 26.59 44.67 3.353 9.43 9.10 2 MPa 26.61 44.64 3.350 9.80 10.54 4 MPa 26.63 44.68 3.347 12.73 12.78 表 3 4 MPa不同温度下热解煤焦微晶结构参数
Table 3 Crystallite structure parameters of coal char under different temperatures at 4 MPa
Temperature Diffraction
angle /(°)Microcrystalline
structure parameters
/10-1 nm002 peak 100 peak d Lc La 800 ℃ 26.57 44.58 3.355 9.93 11.19 900 ℃ 26.63 44.67 3.348 10.7 10.72 1000 ℃ 26.63 44.68 3.347 12.78 12.78 1100 ℃ 26.65 44.67 3.345 12.73 9.79 -
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