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摘要: 采用高温热台显微镜观测了片状煤焦颗粒CO2气化过程中的形态演变，并通过拉曼光谱分析了气化半焦的碳微晶结构，同时研究了气化温度（1000-1200℃）和煤焦初始当量直径（1.00-1.60 mm）对其CO2气化过程中的形态及结构演变的影响规律。结果表明，与反应前期相比，反应后期的颗粒收缩（面积、体积、当量直径）更加剧烈。在所研究的气化温度范围内，随着气化温度的升高，煤焦颗粒的面积收缩率和体积收缩率逐渐减小。煤焦初始粒径显著影响颗粒收缩，1100℃气化温度下，颗粒的收缩趋势在初始粒径1.30 mm处出现转折。煤焦气化过程中碳消耗主导着表观密度的变化，在所研究的温度和粒径范围内，当碳转化率达到80%时，表观密度比线性减小到0.4以下。在相同气化温度下，随着碳转化率的增加，煤焦的石墨化程度先减小后增加，无定形碳含量先增加再减小。Abstract: High temperature stage microscope was applied to observe morphology evolution of flaky char particles during gasification. Raman spectroscopy was used to analyze crystalline structures of gasification semicoke. Effect of gasification temperature (1000-1200℃) and initial equivalent diameter (1.00-1.60 mm) on morphology and structure evolution were examined. The results show that particle shrinkage in later stage of gasification is more intense than that in early stage. Within tested gasification temperature, the particle ASR (area shrinkage ratio) and VSR (volumetric shrinkage ratio) decrease with increasing temperature. The initial particle size of char has a significant effect on particle shrinkage. At 1100℃ the shrinkage trend of particle marks a turning point at initial diameter of 1.30 mm. The variation of char apparent density is dominated by carbon consumption. When the carbon conversion reaches 80%, the apparent density ratio linearly decreases below 0.4. At the same gasification temperature, with increasing carbon conversion the graphitization of char reduces first and then increases, while the amorphous carbon is opposite.
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图 1 煤焦颗粒在高温热台显微镜下的投影图像
Figure 1 Projection image of the char particle under the high temperature stage microscope
图 3 碳转化率随气化反应时间的变化
Figure 3 Carbon conversion vs gasification time for char particle
(a): equivalent diameter of 1.30 mm; (b): gasification temperature of 1100 ℃
图 4 1100 ℃气化温度下煤焦颗粒在反应过程中的面积演变
Figure 4 Area evolution of char recorded by the heating stage microscope at 1100 ℃
图 5 气化过程中片状煤焦颗粒z投影面的面积收缩
Figure 5 Area shrinkage of flaky char particle in CO2 gasification
(a): equivalent diameter of 1.30 mm; (b): gasification temperature of 1100 ℃
图 6 气化过程中片状煤焦颗粒的体积收缩
Figure 6 Volumetric shrinkage of flaky char particle in CO2 gasification
(a): equivalent diameter of 1.30 mm; (b): gasification temperature of 1100 ℃
图 7 气化过程中片状煤焦颗粒当量直径比的变化
Figure 7 Variation of equivalent diameter ratio for the flaky char particle in CO2 gasification
(a): equivalent diameter of 1.30 mm; (b): gasification temperature of 1100 ℃
图 8 气化过程中片状煤焦颗粒表观密度比的变化
Figure 8 Variation of apparent density ratio for the char particle in CO2 gasification
(a): equivalent diameter of 1.30 mm; (b): gasification temperature of 1100 ℃
图 9 ID1/IG与ID3/IG随气化温度和碳转化率的变化
Figure 9 Variation of ID1/IG与ID3/IG with gasification temperature and carbon conversion
表 1 原煤和热解焦的工业分析和元素分析
Table 1 Proximate, ultimate analysis of raw coal and pyrolysis char
Sample Proximate analysis wd/% Ultimate analysis wd/% A V FC C H O* N S SM 5.90 34.78 59.32 79.35 5.00 8.19 1.00 0.56 SMC 8.40 1.64 89.96 89.10 0.42 0.28 1.27 0.53 
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表 2 片状煤焦颗粒长、宽、高的尺寸
Table 2 Specific dimension of length, width and height for flaky char particles
Initial equivalent diameter /mm Length /mm Width /mm Height /mm 1.00 1.08-1.14 0.98-1.12 0.52-0.54 1.15 1.27-1.30 1.05-1.19 0.58-0.60 1.30 1.49-1.53 1.26-1.35 0.58-0.62 1.60 1.74-1.80 1.61-1.62 0.72-0.74
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表 3 1100 ℃气化温度下反应前期和反应后期的比表面积对比
Table 3 Comparison of specific surface area at the early stage and later stage of reaction
Sample 1100 ℃-0.3 1100 ℃-0.5 1100 ℃-0.7 ABET/(m2·g-1) 237.2 280.9 442.6
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表 4 不同气化温度下碳转化率为50%的气化半焦的BET比表面积
Table 4 BET specific surface area of gasification semi-coke with carbon conversion of 50 % at different gasification temperatures
Sample 1000 ℃-0.5 1100 ℃-0.5 1200 ℃-0.5 ABET /(m2·g-1) 649.2 280.9 78.3
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