Effect of solvent swelling on structure and pyrolysis product distribution of Ordos lignite
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摘要: 采用四种有机溶剂对鄂尔多斯褐煤进行溶胀预处理并在粉-粒流化床上进行快速热解,探究溶胀对褐煤结构及热解特性的影响。采用傅里叶变换红外光谱仪、热重分析仪、气相色谱-质谱联用仪、固体核磁、X射线衍射、全自动化学吸附仪等仪器对溶胀煤及热解产物进行表征。结果表明,非极性溶剂对煤结构影响较小。极性溶剂可以降低褐煤含氧官能团的氢键交联,增加小分子的流动性,增加煤的平均孔径。溶胀后的煤热解焦油和气相产率提高,热解水产率降低。与原煤相比,极性溶剂甲醇、丙酮、四氢呋喃处理煤样的热解焦油产率分别提高了18.88%、26.72%、33.58%,焦油的轻质组分中酚类、单环和双环类芳香烃组分含量明显增加。Abstract: Four kinds of organic solvents were used to pretreat Ordos lignite to obtain swelling coal. The effect of swelling on the structure and pyrolysis characteristics of Ordos lignite was investigated by fast pyrolysis of swelling coal in a powder-particle fluidized bed. The swelling coal and pyrolysis products were characterized by FT-IR, TGA, GC-MS, 13C NMR, XRD. The results show that non-polar solvent has little effect on coal structure. The polar solvents can reduce the hydrogen bond crosslinking of oxygen-containing functional groups of lignite, increase the fluidity of small molecules and the average pore diameter of coal. After swelling, The yield of coal tar and gas phase yield increases, the pyrolysis water yield decreases. After pretreatment with methanol, acetone, and tetrahydrofuran, the yield of pyrolysis tar increased by 18.88%, 26.72%, 33.58% respectively. Compared with raw coal, and the contents of phenolic, monocyclic and bicyclic aromatic hydrocarbons components in the light components of tar were significantly increased.
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Key words:
- swelling /
- lignite /
- fast pyrolysis /
- powder-particle fluidized bed
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表 1 粉-粒流化床实验参数
Table 1 Experimental parameters of powder particle fluidized bed
Gas Feed rate/(gcoal·min−1) Mass/g Gas flow/(L·min−1) Temperature/℃ ED SiO2 feed gas fluidized gas reactor cyclone separator condenser tube N2 0.2 5.0 56.9−57.0 1.2 0.6 600 350 −40 ± 2 表 2 实验煤样的溶胀度、工业分析和元素分析
Table 2 Swelling degree and proximate and ultimate analyses of coal samples used in the experiment
Sample Q Proximate analysis w/% Ultimate analysis wdaf/% Atomic ratio Md Ad Vdaf FCdaf* N C H S O* O/C H/C ED — 2.59 6.21 37.27 62.73 1.24 79.45 4.52 0.40 14.40 0.225 0.683 ED-N 1.07 3.01 6.25 36.54 63.46 1.22 80.54 4.28 0.33 13.63 0.215 0.637 ED-M 1.27 3.29 6.12 37.36 62.64 1.18 81.17 4.27 0.30 14.17 0.221 0.639 ED-A 1.36 3.89 6.16 36.91 63.09 1.21 79.70 4.14 0.26 14.69 0.227 0.624 ED-T 1.50 3.45 6.29 37.84 62.16 1.16 79.85 4.23 0.25 14.52 0.225 0.635 note: * means the data obtained by subtraction method; the data of proximate and ultimate analyses are obtained after the coal samples were dried at 105 ℃ for 12 h 表 3 煤样孔结构参数
Table 3 Pore structure parameters of coal sample
Samples Surface
area /(m2·g−1)Pore volume/
(mL·g−1)Pore size/
nmED 7.86 0.0153 7.78 ED-N 6.51 0.0156 9.61 ED-M 2.23 0.0102 18.30 ED-A 2.70 0.0124 18.42 ED-T 0.77 0.0062 32.40 表 4 TG参数
Table 4 TG parameters
Sample w/% ti/℃ tmax/℃ tf/℃ tp/℃ Rmax/(%·min−1) ED 33.48 355 452 549 700 1.34 ED-N 31.51 344 450 560 − 1.16 ED-M 34.41 322 445 568 676 1.18 ED-A 35.28 344 447 550 − 1.26 ED-T 33.37 339 449 559 − 1.21 note: − means that there is no obvious peak 表 5 XRD分峰拟合参数
Table 5 Fitting parameters of XRD peaks
Sample 2θ002/(°) d002/nm Lc/nm n 2θ100/(°) La/nm ED 25.32 0.1802 1.2157 6.75 43.74 1.9479 ED-N 25.28 0.1804 1.1982 6.64 43.77 1.7195 ED-M 25.21 0.1809 1.1206 6.20 43.25 1.8019 ED-A 25.01 0.1822 1.0594 5.81 44.11 2.0501 ED-T 24.92 0.1829 0.9445 5.16 43.12 1.9966 表 6 煤样的核磁分峰数据
Table 6 NMR peak data of coal samples
Sample Al-C Ar-C Carboxy-C CH2/CH3 ED 31.99 57.66 10.35 1.23 ED-N 32.03 57.58 10.39 1.37 ED-M 32.30 57.37 10.33 1.20 ED-A 32.76 57.34 9.90 1.19 ED-T 32.99 57.35 9.66 1.17 note: aliphatic carbon content Al-C=$ f_{\mathrm{a}\mathrm{l}}^{3} $+$ f_{\mathrm{a}\mathrm{l}}^{\mathrm{a}} $+$ f_{\mathrm{a}\mathrm{l}}^{2} $+$ f_{\mathrm{a}\mathrm{l}}^{1} $+$ f_{\mathrm{a}\mathrm{l}}^{\mathrm{*}} $+$ f_{\mathrm{a}\mathrm{l}}^{\mathrm{O}} $;aromatic carbon content Ar-C=$ f_{\mathrm{a}}^{\mathrm{H}} $+$ f_{\mathrm{a}}^{\mathrm{B}} $+$ f_{\mathrm{a}}^{\mathrm{S}} $+$ f_{\mathrm{a}}^{\mathrm{O}} $;carbonyl carbon content Carboxy-C=$ f_{\mathrm{a}}^{\mathrm{C}\mathrm{C}} $;CH2/CH3=($ f_{\mathrm{a}\mathrm{l}}^{3} $+$ f_{\mathrm{a}\mathrm{l}}^{\mathrm{a}} $)/$ f_{\mathrm{a}\mathrm{l}}^{2} $ 表 7 煤样热解产物的收率
Table 7 Yield of pyrolysis products of coal samples
Yield w/% ED ED-N ED-M ED-A ED-T Tar 9.32 9.56 11.08 11.81 12.45 Char 71.01 70.82 69.39 68.72 68.14 Gas 16.44 16.47 17.03 17.12 17.25 Water 3.23 3.15 2.50 2.35 2.16 note: the data above were obtained after eliminating the residual solvent in tar, and the gas yield was obtained by subtraction method 表 8 热解气相产物分布
Table 8 Distribution of pyrolysis gas products
Sample Component content/($ {\rm{mmol}} \cdot {\rm{g}}_{{\rm{coal{\text{,}}daf}}}^{-1} $) CO CH4 CO2 C2 C3 H2 ED 1.05 1.04 0.48 0.15 0.07 0.21 ED-N 0.97 0.75 0.49 0.13 0.08 0.12 ED-M 1.12 0.88 0.62 0.17 0.09 0.21 ED-A 1.17 0.68 0.66 0.15 0.07 0.14 ED-T 1.23 0.94 0.65 0.17 0.09 0.16 -
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