Effect of tetralin on the reaction behavior of volatiles from pyrolysis of Naomaohu coal
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摘要: 煤在中低温热解过程中挥发物反应会显著影响焦油组成和析炭行为，这与挥发物反应活性及体系富氢组分含量有关。本文采用两段式固定床反应器，通过引入四氢萘（THN），进行淖毛湖煤热解挥发物在不同温度下的反应行为，及其对产物分布和析炭产率影响的对比研究，借助全二维气质联用仪对焦油组成进行分析。结果表明，400 °C时因挥发物与THN间的反应较弱且焦油冷凝导致析炭量较高；随着温度升高，挥发物和THN间的反应加剧，导致液体产物产量下降、气体产量增大。根据挥发物和THN反应产物分布的计算值和实验值发现，引入THN后液体产物产量增大，且2−5环芳烃和析炭量减少。表明挥发物与THN之间存在相互作用，促进了THN的α−H转移，为反应体系提供了更多H·。同时，有助于酚类化合物和其他含氧类物的形成，特别是多元酚。煤热解挥发物的反应活性与含氧类自由基有关，此类自由基对H·的键合力较强。Abstract: The volatiles’ reaction has a significant influence on composition and coking behavior of tar during low-medium temperature pyrolysis of coal, which is closely related to the activity of volatiles and the content of components rich in hydrogen in the system. By introducing tetralin, the effect of reaction of volatiles generated by pyrolysis of Naomaohu coal on the product distribution and coke yield was explored at various temperatures using a two-stage fixed bed reactor. The tar composition was analyzed by a comprehensive two-dimensional gas chromatography/mass spectrometry. The results show that the yield of coke is higher at 400 oC due to the weaker reaction between volatiles and THN and tar condensation. As the temperature increases, the reaction between volatiles and THN intensifies, resulting in the decrease of liquid products yield and the increase of gas yield. According to the calculated and experimental values of the reaction products of volatiles and THN, it is found that the liquid products yield increases after the introduction of THN. The contents of aromatic hydrocarbons with 2−5 rings and coke both decrease. This indicates that the interaction between volatiles and THN promotes the α−H transfer of THN and provides more active hydrogen for the reaction system. Besides, the interaction between volatiles and THN is also beneficial to the formation of phenolic compounds and other oxygenated compounds, especially for polyphenols. The activity of volatiles during coal pyrolysis is related to oxygen-containing radicals, which have a strong bond with active hydrogen.
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Key words:
- Naomaohu coal /
- tetralin /
- volatiles’ reaction /
- tar /
- coke
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图 1 两段式固定床-质谱联用装置示意图
Figure 1 Schematic diagram of two-stage fixed bed reactor and mass spectrometer
图 2 不同反应温度下THN对NMH煤热解产物产量的影响
Figure 2 Effect of tetralin on the product yields during pyrolysis of NMH coal at different reaction temperatures
(a): Liquid product; (b): Gas product; (c): Coke; (d): Water
图 3 不同反应温度下THN对NMH煤热解液体产物组成的影响
Figure 3 Effect of tetralin on the liquid compositions during pyrolysis of NMH coal at different reaction temperatures
(a): Phenols; (b): PAHs; (c): Aliphatics; (d): Benzenes; (e): Oxygenated compounds; (f): Heteroatomic compounds
图 4 不同反应温度下THN对NMH煤热解液体产物中多环芳烃组成的影响
Figure 4 Effect of tetralin on the PAHs compositions of liquid during pyrolysis of NMH coal at different reaction temperatures
(a): 2-rings aromatics; (b): 3-rings aromatics; (c): 4-rings aromatics; (d): 5-rings aromatics
图 5 不同反应温度下THN对NMH煤热解液体产物中脂肪族化合物组成的影响
Figure 5 Effect of tetralin on the aliphatics compositions of liquid during pyrolysis of NMH coal at different reaction temperatures
图 6 不同反应温度下THN对NMH煤热解液体产物中酚类化合物组成的影响
Figure 6 Effect of tetralin on the phenols compositions of liquid during pyrolysis of NMH coal at different reaction temperatures
图 7 不同反应温度下THN对NMH煤热解气体组成的影响
(a): H2; (b): CH4; (c): CO2; (d): CO
Figure 7 Effect of tetralin on the gas compositions during pyrolysis of NMH coal at different reaction temperatures
表 1 淖毛湖煤的基本性质
Table 1 Basic properties of NMH coal
Proximate analysis w/% Ultimate analysis wdaf/% Gray-King wdaf/% Mad Ad Vdaf C H N S Oa tar yield water yield 19.50 5.80 50.12 74.35 5.13 0.72 0.31 19.49 15.4 11.7 note: ad: air-dry basis; daf: dry-and-ash-free basis; a: by difference 
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