Structural analysis of functional group and mechanism investigation of caking property of coking coal
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摘要: 以11种炼焦煤为研究对象,分别进行FT-IR和黏结指数G测试。采用PeakFit软件对FT-IR谱峰进行分峰拟合和定量计算,研究炼焦煤特征官能团含量与其黏结性间的关系。结果表明,煤黏结性大小与其FT-IR吸收峰密切相关,特别是3 000-2 800和3 700-3 000 cm-1两个吸收带;脂肪族结构是煤黏结性形成的主要决定因素,通常脂肪链越短或支链化程度越高,越有利于煤的黏结性形成;含-OH(或-NH)的氢键缔合结构可以与脂肪链协同作用,共同决定煤的黏结性能。不论煤分子有多大,只要是结构单元缩合度较小而作为桥键的脂肪链较多的结构形式,在热解过程中就会生成大量适度分子量、以结构单元为基元的液相物质。氢键是煤中主要的分子间作用形式,当若干形成氢键的官能团聚集缔合时,其相互作用会更强,甚至会形成类似超分子的结构;在形成胶质体阶段,这类氢键缔合的结构也会被打破,并形成以胶质体液相为主的物质。这些液相物质的存在,有利于胶质体的流动、黏连和固化成为半焦,从而最终获得优越的黏结性。Abstract: Eleven coking coals were used in this study and FT-IR and the caking index tests were carried out. The peak separation and quantitative calculation of FT-IR spectra were performed by using Peakfit Software and the relationship between caking property and typical functional groups of coal was investigated. The results showed that there was a close relationship between caking property and FT-IR spectra of coal, especially in the regions of 3 000-2 800 cm-1 and 3 700-3 000 cm-1. The component with aliphatic structure was a major determinant of coal caking property. Usually the shorter chain length or the higher branching degree of coal aliphatic structure was, the higher caking property will be. The caking property was codetermined by aliphatic structure and hydrogen bond (including-OH or-NH) and there was a synergic relationship between them. When the condensed degree of structural unit was low and the amount of bridge bonds was higher, the plastic mass based on structural unit with moderate molecular weight can be generated regardless of the coal molecule size. The most dominant sort of binding forces in coal was hydrogen bond. An associative structure even supermolecular structure, which was broken and changed into plastic mass during the state of metaplast, was formed when a number of hydrogen bonds were associated together. The existence of plastic mass was beneficial to the transformation of metaplast into semi-coke and further acquisition of well caking property.
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Key words:
- coking coal /
- FT-IR /
- quantitative analysis /
- Peakfit /
- caking property
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图 2 煤样BL在FT-IR四区间上的分峰拟合图
Figure 2 Graphical representation of peak separation in the four regions of FT-IR spectrum of coal BL
表 1 煤样的来源矿区及其工业分析、元素分析与黏结指数
Table 1 Mines,origin,proximate and ultimate analysis and caking index of coal samples
Specie Mine Origin Proximate analysis w/% Ultimate analysis wdaf /% G Mad Ad Vdaf FCdaf C H Oa N St,d HB Hebi Henan 0.35 10.56 15.96 84.04 91.11 4.64 2.15 1.64 0.45 16.5 DY Dayou Henan 0.71 10.44 25.43 74.57 88.86 5.23 2.96 1.48 1.46 84.1 DX Daxie Anhui 0.46 10.75 32.68 67.32 88.41 5.86 3.49 1.61 0.63 90.4 XL Xinlei Shanxi 1.34 7.60 27.65 72.35 87.52 5.37 3.40 1.50 2.21 82.7 TT Tongting Anhui 1.17 7.01 32.52 67.48 87.08 5.88 4.88 1.77 0.37 97.2 BL Bailong Shanxi 0.82 8.95 32.67 67.33 86.52 5.52 5.55 1.61 0.81 78.9 YD Yaodu Shanxi 0.42 10.38 26.33 73.67 86.26 5.30 5.47 1.60 1.36 87.7 YC Yucheng Shanxi 0.68 8.69 37.13 62.87 86.24 6.06 5.09 1.63 0.98 91.4 JX Jinxin Shanxi 1.90 11.16 36.21 63.79 84.25 6.08 7.25 1.68 0.74 18.6 WS Weishan Shandong 1.74 8.49 36.36 63.64 83.50 5.88 8.32 1.69 0.61 69.7 TY Tianyi Shanxi 1.26 10.05 33.86 66.14 83.15 5.55 8.54 1.62 1.14 10.7 a by difference 
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表 2 煤样FT-IR吸收峰归属
Table 2 Bands assignment of FT-IR absorption peaks of coal samples
Band position σ/cm-1 Functional group 3611 free OH groups 3516 OH-π hydrogen bonds 3350-3470 self-associated OH,pyrrolic NH 3300 OH- ether O hydrogen bonds 3200 tightly bound cyclic OH tetramers 3150 OH-N 3030-3050 stretching aromatic C-H 2950-2850 stretching C-H aliphatic,R-CH3 and R2CH2- asymmetric stretching,RCH2- symmetric stretching 2950 RCH3 stretching vibration 2920 R2CH2 stretching vibration 2890 R3CH stretching vibration 1900-1650 residual water vapor 1700 conjugate C=O 1600-1590 (C-H)ar poly aromatic system,aromatic C=C stretching 1500 stretching C-C aromatic 1450-1440 bending C-H aliphatic 1380-1375 symmetric deformation -CH2-(bending) 1261-1251 weak band of C=O stretching 1091,1031,1010 ash in coal 900-700 aromatic bands mainly due to aromatic-carbon-carbon rocking vibrations 870 substituted benzene ring with isolated hydrogen 814 substituted benzene ring with two neighboring hydrogen or angular condensation ring systems 790 CH2- rocking mode of ethyl group 750 benzene ring orto-substituted and meta-substituted and condensed ring systems
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表 3 经Peakfit分峰拟合后所得FT-IR吸收峰的相对峰面积(Ⅰ)
Table 3 Relative peak areas of coal samples separated and calculated by Peakfit(Ⅰ)
Region Aromatic substitution Oxygen-containing functional groups 750cm-1 790cm-1 812cm-1 872cm-1 1033cm-1 1100cm-1 1200cm-1 1300cm-1 1400cm-1 1440cm-1 1600cm-1 1650cm-1 HB 0.1923 0.1164 0.0776 0.1406 0.3027 0.0606 0.0822 0.2529 0.6829 0.4300 1 0.8845 DY 0.2118 0.0751 0.0759 0.1062 0.7497 0.0637 0.1796 0.2852 0.4702 0.7444 1 0.5697 DX 0.1398 0.0538 0.0736 0.0429 0.5718 0.4274 - - - 0.5498 1 0.6500 XL 0.1635 0.1822 0.0628 0.1063 0.1318 0.3258 0.2310 0.1778 1.2052 0.3871 1 1.0561 TT 0.0839 0.0517 0.0478 0.0598 0.2200 0.3272 0.3620 0.3305 - 0.6684 1 - BL 0.0329 0.0386 0.0570 0.0254 0.3540 0.3561 0.0657 0.0745 1.0207 0.2715 1 1.1554 YD 0.1486 0.0359 0.0506 0.0566 0.6586 0.1476 0.2099 0.4455 - 0.5688 1 0.8207 YC 0.0990 0.0396 0.0688 0.0439 0.2219 0.1401 0.1560 0.5120 - 0.4585 1 0.9069 JX 0.0130 0.0100 0.0099 0.0078 0.3358 0.2551 0.1036 0.1862 0.1956 0.6740 1 0.8858 WS 0.0547 0.0213 0.0277 0.0190 0.1679 0.1607 0.2648 0.2060 0.2907 0.4518 1 0.1060 TY 0.0656 0.0204 0.0283 0.0011 0.3102 0.1240 0.2470 0.2932 0.7485 0.2786 1 0.3397
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表 4 经Peakfit分峰拟合后所得FT-IR吸收峰的相对峰面积(Ⅱ)
Table 4 Relative peak areas of coal samples separated and calculated by Peakfit(Ⅱ)
Region Aliphatic functional groups Hydrogen bond 2850cm-1 2890cm-1 2923cm-1 2950cm-1 3050cm-1 3130cm-1 3200cm-1 3300cm-1 3370cm-1 3440cm-1 3500cm-1 3600cm-1 HB 0.1201 0.0823 0.2017 0.0628 0.1303 0.3769 0.7570 1.5064 2.3682 3.7854 3.2547 1.7907 DY 0.2014 0.1533 0.3321 0.1613 0.1241 0.1261 0.4617 0.7754 1.4931 1.3551 0.8954 0.6264 DX 0.2322 0.1741 0.3891 0.1755 0.1190 0.4975 0.8989 1.1740 1.9280 2.3749 1.9147 0.9366 XL 0.1722 0.1213 0.2895 0.1108 0.2822 1.8510 2.1916 2.4976 4.2235 5.2989 4.1547 2.1920 TT 0.1009 0.0755 0.1658 0.0784 0.0850 0.3402 0.5562 0.7167 1.1509 1.4076 1.1631 0.6336 BL 0.1149 0.0729 0.2263 0.0861 0.1322 1.4915 1.8807 2.1757 3.6075 4.3605 3.2090 1.8038 YD 0.1560 0.1167 0.2587 0.1196 0.1770 0.3851 0.9498 1.3172 2.0749 2.5499 2.0843 1.0831 YC 0.1633 0.1221 0.2732 0.1271 0.2397 0.8039 1.3707 1.7956 2.8740 3.5340 2.8492 1.5636 JX 0.1229 0.0770 0.2310 0.0738 0.1675 0.9263 1.4848 1.9360 3.3764 4.2060 3.1607 1.7092 WS 0.0707 0.0519 0.1137 0.0517 0.0899 0.3070 0.4586 0.5427 0.8035 0.9701 0.8310 0.4477 TY 0.0865 0.0618 0.1379 0.0467 0.0908 0.3758 0.6312 0.7652 1.1354 1.2944 1.0329 0.5346
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表 5 FT-IR参数与G值关系的多元线性回归分析
Table 5 Multiple linear regression analysis on the relationship between FT-IR parameters and G value
No. Independent variables (xi,i=1,2,3) Radj2 No. Independent variables (xi,i=1,2,3) Radj2 x1 x2 x3 x1 x2 x3 E1 I1 - - -0.0467 E30 I1 I4 I6 0.9314 E2 I2 - - 0.1768 E31 I1 I5 I6 -0.1287 E3 I3 - - 0.1100 E32 I2 I3 I4 0.9290 E4 I4 - - 0.7846 E33 I2 I3 I5 -0.0175 E5 I5 - - 0.0165 E34 I2 I3 I6 0.2171 E6 I6 - - 0.1006 E35 I2 I4 I5 0.7952 E7 I1 I2 - 0.0744 E36 I2 I4 I6 0.9065 E8 I1 I3 - -0.1691 E37 I2 I5 I6 -0.0561 E9 I1 I4 - 0.7904 E38 I3 I4 I5 0.9397 E10 I1 I5 - -0.0696 E39 I3 I4 I6 0.9297 E11 I1 I6 - -0.1679 E40 I3 I5 I6 0.0264 E12 I2 I3 - 0.0958 E41 I4 I5 I6 0.9191 E13 I2 I4 - 0.7878 E42 I6* - - -0.1061 E14 I2 I5 - 0.0746 E43 I1 I6* - -0.1767 E15 I2 I6 - 0.0739 E44 I2 I6* - 0.0739 E16 I3 I4 - 0.9376 E45 I3 I6* - -0.2442 E17 I3 I5 - -0.0813 E46 I4 I6* - 0.8537 E18 I3 I6 - -0.0321 E47 I5 I6* - 0.0163 E19 I4 I5 - 0.7608 E48 I1 I2 I6* -0.0578 E20 I4 I6 - 0.9164 E49 I1 I3 I6* -0.3152 E21 I5 I6 - -0.0083 E50 I1 I4 I6* 0.9474 E22 I1 I2 I3 -0.0333 E51 I1 I5 I6* -0.2186 E23 I1 I2 I4 0.7704 E52 I2 I3 I6* -0.0178 E24 I1 I2 I5 -0.0572 E53 I2 I4 I6* 0.8647 E25 I1 I2 I6 -0.0058 E54 I2 I5 I6* -0.5760 E26 I1 I3 I4 0.9346 E55 I3 I4 I6* 0.9425 E27 I1 I3 I5 -0.2115 E56 I3 I5 I6* -0.2101 E28 I1 I3 I6 0.2237 E57 I4 I5 I6* 0.8359 E29 I1 I4 I5 0.7704
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