Influence of group component distribution of coal tar pitch on mesophase structure development of needle coke
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摘要: 原料沥青的族组成是决定针状焦品质的关键因素。采用超声溶剂萃取对煤焦油沥青进行组分分离,并对沥青族组成进行混合再调配,以探究不同组分对生焦中间相结构形成及发育的影响并进行优化。研究表明,正己烷可溶物(HS)中含有丰富的脂肪结构,在炭化过程中过高比率的HS不利于大尺寸中间相的生成,但是适量的组分HS在炭化过程中可以调节体系黏度,维持体系足够长时间的低黏度,保证中间相可以充分的生长和发育;甲苯不溶物(TI)主要为高聚合度的稠环芳烃,可以加速中间相小球体的生成和发育,但是过量的TI组分会导致镶嵌型结构的生成,降低针状焦的品质;正己烷不溶-甲苯可溶物(HI-TS)炭化得到的生焦具有最优的光学各向异性结构,是最适宜作为针状焦原料的组分。组成为HS≈25%、HI-TS≈69%、TI≈3%−8%的精制沥青炭化后可制备出中间相结构发育良好、热膨胀系数较低的针状焦。Abstract: Group composition distribution of raw coal tar pitch is the key factor to determine quality of needle coke. The components of coal tar pitch were separated by ultrasonic solvent extraction. Effect of each group composition on mesophase characteristics was investigated. The group components were well blended to explore impact of different components on formation and development of mesophase structure. The results show that n-hexane soluble fraction (HS) is rich of aliphatic functional groups, and the excessive amount of HS fraction is not conducive in formation of large scale mesophase. Nevertheless, an appropriate amount of HS can maintain a proper lower viscosity in a long time range of the melting pitch system, which is significantly beneficial to growth and development of mesophase. Toluene insoluble substance (TI) is mainly consisted of dense cyclic aromatic hydrocarbon with high degree of polymerization. It can accelerate generation and development of mesophase sphere. However, excessive TI fraction can lead to generation of mosaic structure and reduce quality of needle coke. The green coke obtained from n-hexane insoluble and toluene soluble matters (HI-TS) demonstrate better optical anisotropy structure and is considered be the most suitable component for preparation of needle coke. The refined pitch with HS≈25%, HI-TS≈69%, and TI≈3%−8% can produce needle coke with well-developed mesophase structure and low thermal expansion coefficient.
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Key words:
- coal tar pitch /
- solvent extraction /
- composition /
- carbonization /
- needle coke
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表 1 原料煤焦油沥青RCTP和精制沥青CTP的基本分析
Table 1 Basic analysis of raw coal tar pitch RCTP and refined pitch CTP
Sample C/% H/% C/H Softening point/℃ HS/% HI-TS/% TI-QS/% QI/% RCTP 92.96 4.29 1.81 78.5 21.51 62.64 12.87 2.98 CTP 92.75 4.82 1.60 72.4 24.58 65.81 9.56 0.05 表 2 CTP和萃取组分的氢分布
Table 2 Hydrogen distributions of CTP and extracted components
Sample Har% Hα% Hβ/% Hγ/% CTP 81.89 9.53 5.56 3.03 HS 54.60 27.12 15.62 2.67 HI-TS 81.76 7.40 7.02 3.79 HI 89.75 3.49 4.42 2.34 表 3 各向异性结构划分标准
Table 3 Classification of anisotropic texture
Anisotropic Texture Abbreviation Size/μm Spherical unit mosaic M dia. < 60 domain D dia. > 60 Elongated unit short flow SF l <300, w <60 long flow LF l >300, w <60 flow domain FD l >300, w >60 表 4 煅后焦的CTE值
Table 4 CTE value of calcined cokes
Sample CTE/(×10−6·℃−1) Sample CTE/(×10−6·℃−1) Sample CTE/(×10−6·℃−1) NC-HS-1 1.32 NC-TI-1 1.15 NC-HI-TS-1 1.58 NC-HS-2 1.13 NC-TI-2 1.18 NC-HI-TS-2 1.53 NC-HS-3 1.45 NC-TI-3 1.48 NC-HI-TS-3 1.46 NC-HS-4 1.48 NC-TI-4 1.65 NC-HI-TS-4 1.67 -
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