Structural changes of Shenfu coal in pyrolysis and hydrogasification reactivity of the char
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摘要: 将煤加氢过程分解为原煤热解和焦加氢两个过程,在固定床反应器内研究了煤热解和焦加氢反应。采用红外气体分析仪、拉曼光谱仪和X射线衍射仪,分析研究了煤热解过程中气体组分含量与煤焦微观结构变化的相互关系以及煤焦微观结构对其加氢反应特性的影响。结果表明,热解温度对煤焦的微观结构和加氢反应性有较大影响,400-800℃,随着温度升高,煤焦拉曼分峰面积比AD1/AG、AD2/AG、AD3/AG、AD4/AG均上升,AG/AAll减小。800-900℃,AG/AAll增大,无序碳的相对含量增加,石墨化进程明显。煤焦的XRD分析与拉曼光谱分析结果一致。400-800℃,随着温度升高,煤焦中碳结构晶面间距d002先增加后减小,堆垛高度L002增加,晶面间距与堆垛高度比d002/L002减小,煤焦中石墨碳结构的含量增加。800-900℃,d002减小,L002明显增大。采用拉曼分峰比(aAD1/G+bAD2/G+cAD3/G+dAD4/G)与加氢反应性特征参数τ0.5进行线性拟合,得到代表碳微晶结构加氢反应性的拟合因子,且拟合因子越大,相应碳微晶的加氢反应性越好。Abstract: Coal hydrogasification, divided into coal pyrolysis and char hydrogasification, was studied in a fixed bed reactor.FT-IR gas analyzer, Laser Raman analyzer and XRD were applied to analyze the relationship between gas production component of coal pyrolysis and microstructure change of char, and the influence of microstructure change of char on char hydrogasification reactivity.The results show that pyrolysis temperature has an obvious effect on microstructure and hydrogasification reactivity of char.With rising temperature, the ratios of Raman band area AD1/AG, AD2/AG, AD3/AG, AD4/AG gradually rises, and the ratio of AG/AAll decreases within 400-800℃ and increases within 800-900℃.It indicates that graphitization process of char is obviously emerged due to the increase of relative amount of disordered carbon in pyrolysis.The results of XRD analysis are in accordance with those of Raman analysis.The interplanar crystal spacing d002 increases within 400-800℃.d002 decreases and L002 increases sharply within 800-900℃.By fitting the Raman area ratio formula (aAD1/G+bAD2/G+cAD3/G+dAD4/G) with hydrogasification reactivity (τ0.5), the obtained factor represents the hydrogasification reactivity of carbon microcrystal.The factor is bigger, and the reactivity of carbon microcrystal is better.
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Key words:
- coal pyrolysis /
- microstructure /
- char hydrogasification /
- Raman analysis
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图 1 固定床反应系统示意图
Figure 1 Schematic diagram of the fixed-bed reactor system
1: hydrogen cylinder; 2: high purity nitrogen cylinder; 3: inlet mass flow controller; 4: pressure gage; 5: feed hopper; 6: thermocouple; 7: double entanglements; 8: electric furnace; 9: outlet mass flow meter; 10: gas washing bottle; 11: gas drying bottle valve; 12: gas analyzer; 13: computer
表 1 神府煤的工业分析与元素分析
Table 1 Proximate analysis and ultimate analysis of SF coal
Proximate analysis wad/% Ultimate analysis wd/% M A V FC C H N S 3.02 8.28 36.28 52.42 71.94 3.197 0.94 0.43 表 2 神府煤的灰成分分析
Table 2 Ash compositions analysis of SF coal
Content w/% SiO2 Al2O3 CaO Fe2O3 K2O Na2O MgO 31.99 12.47 25.46 7.24 0.459 2.36 1.51 表 3 炭材料的一级拉曼拟合峰及其振动模式
Table 3 First-order Raman bands and vibration modes of carbon materials
Band Raman shift σ/cm-1 soot disordered graphite highly ordered graphite vibration mode G -1 580 -1 580 -1 580 ideal graphitic lattice (E2g-symmetry) D1 -1 350 -1 350 - disordered graphitic lattice (graphene layer edges,A1g symmetry) D2 -1 620 -1 620 - disordered graphitic lattice (surface graphene layers,E2g-symmetry) D3 -1 500 - - amorphous carbon D4 -1 200 - - disordered graphitic lattice,polyenes,ionic impurities 表 4 拟合峰位置及类型
Table 4 Initial position and peak-fitted type
Peak D1 D2 D3 D4 G Peak position σ/cm-1 1 350 1 620 1 500 1 200 1 580 Peak-fitted type Lorentz Lorentz Gaussian Lorentz Lorentz 表 5 不同热处理温度后样品的( 002) 峰微晶结构参数
Table 5 Crystallite parameters of samples after rapid-heat-treatment at different temperatures
Pyrolysis temperature t/℃ θ002/(°) B002/(a.u.) d002/nm L002/nm d002/L002 400 24.267 8.416 0.367 0.955 0.384 500 24.293 8.284 0.366 0.970 0.377 600 23.948 8.041 0.371 0.999 0.371 700 23.756 8.021 0.374 1.001 0.373 800 24.061 8.133 0.370 0.988 0.374 900 25.149 6.141 0.354 1.311 0.270 -
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