Identification and quantitative analysis of polarized light microstructure of coal-derived needle coke
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摘要: 以精制煤焦油沥青为原料制备针状焦。利用bricc-m煤岩自动测试系统和RICC-Imager图像分析软件，使用打点计数方法，对煤系针状焦偏光显微结构进行定量分析。进一步利用扫描电子显微镜进行针状焦微观结构解析。结果表明，在炭化温度为490 ℃、炭化压力为0.2 MPa、反应时间为6 h条件下制备的生焦，定量分析其广域流线型结构含量为87.8%，显示出较好的光学显微结构。对比传统人工定量分析方法，使用计算机打点计数方法进行定量分析，提高了测试结果的准确性，更加高效，是针状焦显微结构识别和定量分析的有效手段。Abstract: Coal-derived needle coke was prepared using refined coal tar pitch as feedstock. Its polarized light microstructure was quantitatively analyzed by bricc-m coal macerals automatic testing system with RICC-Imager analysis software and the dot counting method. Microstructure of needle coke was characterized using scanning electron microscope. The results indicate that the large domain streamline structure content of the prepared green coke is 87.8% under carbonization conditions of 490 ℃, 0.2 MPa and 6 h, which shows good optical microstructure. Compared with the traditional quantitative analysis method, the quantitative analysis using dot counting method is more accurate and efficient. It can be used as an effective means for quantitative analysis of needle coke microstructure.
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Key words:
- pyrolysis /
- coking /
- microstructure /
- numerical analysis /
- quantitative analysis
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图 2 偏光显微结构定量分析方法示意图
Figure 2 Schematic diagram of the quantitative analysis method on polarized light microstructure
图 4 不同温度下的生焦显微结构照片
(a): 470 ℃; (b): 480 ℃; (c): 490 ℃; (d): 500 ℃; (e): 510 ℃
Figure 4 Polarized micrographs of green coke at different temperatures
图 5 不同压力制备的生焦显微结构照片
(a): 0.1 MPa; (b): 0.2 MPa; (c): 0.3 MPa; (d): 0.4 MPa
Figure 5 Polarized micrographs of green coke prepared at different pressures
图 6 不同炭化时间的生焦显微结构照片(a): 2 h; (b): 4 h; (c): 6 h; (d): 8 h
Figure 6 Polarized micrographs of green coke at different carbonization time (a): 2 h; (b): 4 h; (c): 6 h; (d): 8 h
图 7 不同炭化温度条件制备的针状焦扫描电子显微镜照片
(a): 470 ℃; (b): 480 ℃;(c): 490 ℃; (d): 500 ℃
Figure 7 SEM images of needle coke under different carbonization temperatures
图 8 不同炭化压力条件制得生焦制备的针状焦扫描电子显微镜照片
(a): 0.1 MPa; (b): 0.2 MPa; (c): 0.3 MPa; (d): 0.4 MPa
Figure 8 SEM images of needle coke under different carbonization pressures
图 9 不同炭化时间条件制得生焦制备的针状焦扫描电子显微镜照片
Figure 9 Polarized micrographs of green coke at different carbonization time
(a): 2 h; (b): 4 h; (c): 6 h; (d): 8 h
表 1 煤焦油沥青性质
Table 1 Properties of coal tar pitch and components
Sample Element composition w/% C/H (atomic ratio) Fraction distribution②w/% Ash w/% C H N S O① QI HS HI-TS TI-QS CTP 92.32 4.42 1.28 0.51 1.47 1.74 5.78 26.73 49.09 18.40 0.115 Refined CTP 92.25 4.40 1.20 1.58 0.57 1.75 0.08 13.50 47.49 43.21 0.085 notes:①: by difference; ②: HS: hexane soluble; HI-TS: hexane insoluble but toluene soluble; TI-QS: toluene insoluble but quinoline soluble; QI: quinoline insoluble 
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表 2 各向异性组分划分标准
Table 2 Textures standard for dividing anisotropic components
Texture category Optical properties Wide domain streamline length > 60 μm Thick streamline length 30−60 μm Medium streamline length 10−30 μm Large-grain mosaic radius 5−10 μm Medium-grain mosaic radius 1.5−5 μm Fine-grain mosaic radius < 1.5 μm Isotropy no optical properties
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表 3 不同温度下生焦各结构含量
Table 3 Polarized structural content of green coke at different temperatures
Temperature
/℃Wide domain streamline /% Thick streamline /% Medium streamline /% Large-grain mosaic/% Medium-grain mosaic/% Fine-grained mosaic/% Isotropy /% Streamline total content/% Mosaic total content /% Total anisotropic structure content/% 470 43.4 1.2 0.1 2.9 0.5 4.4 47.5 44.5 7.8 52.5 480 56.6 13.7 3.2 1.4 0.5 2.1 22.6 73.5 4.0 77.4 490 84.6 8.8 1.8 0.6 1.5 0.6 2.1 95.2 2.7 97.9 500 82.4 14.4 1.4 0.7 1.1 0 0 98.2 1.8 100 510 75.8 19.2 4.0 0.6 0.4 0 0 99.1 1.0 100
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表 4 不同压力下生焦各结构含量
Table 4 Polarized structural content of green coke at different pressures
Pressure/MPa Wide domain streamline /% Thick streamline /% Medium streamline /% Large-grain mosaic/% Medium-grain mosaic/% Fine-grained mosaic/% Isotropy /% Streamline total content/% Mosaic total content /% Total anisotropic structure content/% 0.1 87.1 6.3 1.1 0.0 0.9 0.5 4.1 94.5 1.4 95.9 0.2 87.8 8.1 2.2 0.7 0.6 0.6 0.0 98.1 1.9 100 0.3 87.3 8.9 2.0 0.4 0.6 0.5 0.3 98.2 1.5 99.7 0.4 84.6 8.8 1.8 0.6 1.5 0.6 2.1 95.2 2.7 97.9
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表 5 不同炭化时间的生焦各结构含量
Table 5 Polarized structural content of green coke at different carbonization time
Carbonization time/h Wide domain streamline /% Thick streamline /% Medium streamline /% Large-grain mosaic/% Medium-grain mosaic/% Fine-grained mosaic/% Isotropy /% Streamline total content/% Mosaic total content /% Total anisotropic structure content/% 2 81.8 4.6 1.9 1.0 0.3 0.6 9.8 88.3 1.9 90.2 4 87.3 8.7 1.3 1.3 0.7 0.7 0.0 97.3 2.7 100 6 87.8 8.1 2.2 0.7 0.6 0.6 0.0 98.1 1.9 100 8 89.8 6.3 1.8 0.7 1.3 0.1 0.0 97.9 2.1 100
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表 6 不同反应条件下的针状焦CTE
Table 6 CTE of needle coke under different reaction conditions
Parameter Value Temperature/℃ 490 490 490 490 490 Pressure/MPa 0.4 0.2 0.3 0.2 0.2 Carbonization time/h 6 6 6 4 8 CTE/(1 × 10−6/℃) 1.93 1.54 1.79 1.68 1.55
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