Promoting effect of oxidation reaction on steam gasification reaction in Shengli lignite gasification processⅡ.Mechanism study
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摘要: 在φ80×3 000 mm耐高温不锈钢管反应器中，进行了N2/N2+O2/N2+H2O/N2+O2+H2O气氛下800和900℃的胜利褐煤气化实验，采用红外光谱、X射线光电子能谱、拉曼光谱和烟气在线分析等研究了添加氧气前后半焦的物理结构、官能团及煤气组成的变化，旨在探讨氧化反应促进水蒸气气化反应的作用机理。结果表明，氧化反应对水蒸气气化反应的促进作用可用半焦的微观结构变化和水蒸气气化解离吸附机理解释。氧化反应的开孔和扩孔作用使碳颗粒微孔数量、比表面积、孔容、吸附量明显增加，更多的碳表面活性位暴露出来，也促进了半焦中甲基、亚甲基、C=O键、C-O键的断裂和高活性的羧基COO-和大量氢自由基的生成，这些都有利于水蒸气气化反应的进行，尤其在高温和水蒸气含量较高时。同时，氧气的加入改变了反应气氛中CO2、CO、H2相对含量和水蒸气分子/活性炭原子内能，也有利于水蒸气气化反应的进行，这与水蒸气气化解离吸附机理相吻合。Abstract: Shengli brown coal was gasified at 800-900℃ in a simulated entrained-flow reactor, φ 80×3 000 mm.The physical structure and functional groups of char were tested by infrared spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy while coal gas was tested by gas on-line analysis instrument in order to explore the mechanism of promoting effect of oxidation reaction on steam gasification reaction.The results show that the synergy effects can be explained by dissociated adsorption reaction mechanisms of steam gasification reaction and semi-coke pore structure features under different atmospheres.The oxidation reaction can make microspores number, specific surface area, pore volume and adsorption capacity of the char particles greatly increase and more carbon active sites expose by producing microspores, developing mesopores;it also prompts small groups as-CH3, -CH2-, ＞ C=O & ＞ C-O-fractured and generation of hydrogen free-radical and carboxyl.All these promote steam gasification reaction rate, especially at a higher water vapor content or temperature.Meanwhile, the oxidation reaction can change the relative content of CO2, CO, H2 and internal energy of steam molecules and activated carbon atoms, in favor of steam gasification reaction.
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Key words:
- mild gasification /
- synergistic effect /
- steam gasification /
- pore structure /
- dissociated adsorption
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图 2 900℃时向水蒸气气氛中添加1%氧气前后半焦孔容及孔半径变化
Figure 2 Pore volume and pore radius of char in H2O and H2O+1%O2 atmospheres at 900 ℃
图 3 900 ℃时向水蒸气气氛中添加1%氧气前后半焦吸附等温线
Figure 3 Char adsorption is otherm in H2O and H2O+1%O2 atmospheres at 900 ℃
图 4 900℃时向水蒸气气氛中添加1%氧气前后半焦比表面积变化
Figure 4 Char specific surface are aversus steam concentration in H2O and H2O+1%O2 atmospheres at 900 ℃
图 5 向水蒸气气氛中添加1%氧气前后半焦红外光谱谱图
Figure 5 FT-IR spectrum of char in H2O and H2O+1%O2 atmospheres at 800 and 900 ℃
1: 100N2; 2: 15%H2O; 3: 25%H2O; 4: 35%H2O; 5: 15%H2O+1%O2; 6: 25%H2O+1%O2; 7: 35%H2O+1%O2; 8: 100N2; 9: 15%H2O; 10: 25%H2O; 11: 35%H2O; 12: 15%H2O+1%O2; 13: 25%H2O+1%O2; 14: 35%H2O+1%O2
图 6 900℃时向水蒸气气氛中添加1%氧气前后褐煤半焦IGR+VL+VR/ID比值变化
Figure 6 IGR+VL+VR/ID of chars in H2O and H2O+1%O2 atmospheres at 900 ℃
图 7 800和900 ℃时25%H2O和25%H2O+1%O2气氛下褐煤半焦的XPS-O 1s谱图
Figure 7 XPS-O 1s spectra for chars in 25%H2O and 25%H2O+1%O2 atmospheres at 800 and 900 ℃
图 8 800和900 ℃时向水蒸气气氛中添加1%氧气前后褐煤半焦IGL/IT比值变化
Figure 8 IGL/IT of chars in H2O and H2O+1%O2 atmospheres at 800 and 900 ℃
图 9 800℃时向水蒸气气氛中添加1%氧气前后煤气组成变化
Figure 9 Relationship between gas composition and steam concentration in H2O and H2O+1%O2 atmospheres at 800 ℃
图 10 900 ℃时向水蒸气气氛中添加1%氧气前后煤气组成变化
Figure 10 Relationship between gas composition and steam concentration in H2O and H2O+1%O2 atmospheres at 900 ℃
表 1 胜利褐煤的工业分析和元素分析
Table 1 Proximate and ultimate analysis of material
Material Proximate analysis w/% Elemental analysis wdaf/% Mad A V FC C H S O N Shengli lignite 5.89 9.87 36.23 53.90 62.26 6.12 0.66 29.85 1.11 
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表 2 氧交换机理和水蒸气解离吸附机理
Table 2 Oxygen-exchange & dissociative adsorption mechanisms for steam gasification reaction
Oxygen-exchange mechanisms Dissociative adsorption mechanisms H2O+Cf C(H)+C(OH) Adsorption of water molecules H2O+Cf H2+C(O) C(OH)+Cf→C(H)+C(O) and the formation of H2 C(H) 1/2H2+Cf Formation of CO C(O)→CO C(O)→CO Formation of CO2 CO+C(O) CO2+Cf CO+C(O) CO2+Cf
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