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摘要: 以胜利褐煤为原料，利用一段流化床/固定床石英反应器，进行N2/O2/H2O/H2O+O2气氛的褐煤热解/气化实验。采用BET、Raman、FT-IR、微波消解ICP-AES、TGA等技术表征半焦。研究氧气添加对气化反应以及半焦结构和反应性的影响，解析了氧气对气化半焦的活化机理。结果表明，氧气添加可以改变半焦结构，活化半焦，从而促进转化率、H2产率和CO2产率的提高。氧气对气化半焦的活化作用主要包括两个方面，一是芳核与氧气发生氧化分解反应，破坏了芳环大π键，形成了新的官能团，从而促进了反应（C+H2O→H2+CO）的发生；二是随反应的进行，芳香大环（≥6）结构解聚为芳香小环（3-5）结构，同时氧原子进入芳核，形成缺陷位C-O-C，从而导致半焦微晶结构的缺陷程度提高、缩聚程度降低，进而导致半焦反应性和表面吸附作用提高，促进反应（CO+H2O→H2+CO2）的发生。Abstract: The char samples were prepared from pyrolysis/gasification of Shengli lignite in N2/O2/H2O/H2O+O2 atmosphere using a one-stage novel fluidized-bed/fixed-bed quartz reactor, and characterized by BET, Raman, FT-IR, microwave digestion ICP-AES, and TGA techniques. Effects of oxygen addition on gasification reaction and the char structure and reactivity were studied to investigate the activation and mechanism of O2 on the char. The results indicate that oxygen addition could change the char structure and improve the char reactivity, thus promoting gasification conversion and yield of H2 and CO2. The activation of O2 on the char mainly includes two aspects. First, with the decomposition of aromatic nucleus by oxygen, the large π bond of aromatic rings is destroyed, and the new functional groups are generated, which could promote the reaction (C+H2O→H2+CO). Second, with the gasification going on, the large (≥ 6 rings) aromatic structure is depolymerized into small (3-5 rings) one, and oxygen atoms enter the aromatic nucleus, forming the defect position C-O-C. As a result, the defect degree of char microcrystalline structure increases, the polymerization degree of char microcrystalline structure decreases, and the reactivity and surface adsorption of char is improved, which could promote the reaction (CO+H2O→H2+CO2).
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Key words:
- lignite gasification /
- char structure /
- char reactivity /
- Raman spectrum /
- fluidized-bed/fixed-bed
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图 2 800℃不同氧气体积分数的褐煤水蒸气气化转化率
Figure 2 Conversion of lignite steam gasification with different O2 concentrations at 800℃
图 3 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化煤气组分产率
Figure 3 Yield of gas components from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
HCG-CH4+C2H6+C2H4+C3H4+C3H8+i-C4
图 4 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化半焦的比表面积
Figure 4 Surface area of chars from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
图 5 800 ℃水蒸气体积分数25%时褐煤气化所得半焦的拉曼光谱分峰拟合
Figure 5 Peak-fitting of a Raman spectrum of the char from gasification in 25% steam at 800 ℃
图 6 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化半焦的拉曼微晶结构特征
Figure 6 Characteristics of Raman microcrystalline structure of chars from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
图 7 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化半焦的ISL/IVR
Figure 7 ISL/IVR of chars from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
图 8 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化半焦的红外吸收光谱谱图
Figure 8 FT-IR of chars from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
图 9 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化半焦的CO2反应性能
Figure 9 CO2 reactivity of chars from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
图 10 800 ℃不同氧气体积分数的褐煤水蒸气(25%)气化半焦的HNa和Hash
Figure 10 HNa and Hash of chars from lignite steam (25%) gasification with different O2 concentrations at 800 ℃
图 11 700 ℃不同氧气体积分数的褐煤水蒸气气化半焦的红外吸收光谱谱图
Figure 11 FT-IR of chars from lignite steam gasification with different O2 concentrations at 700 ℃
图 12 700 ℃不同氧气体积分数的褐煤水蒸气气化半焦的反应性
Figure 12 Reactivity of chars from lignite steam gasification with different O2 concentrations at 700 ℃
表 1 煤样的工业分析和元素分析
Table 1 Proximate and ultimate analyses of Shengli lignite
Coal Proximate analysis /% Ultimate analysis wdaf/% Mad Vd Ad FCd C H O* N S Shengli lignite 5.69 26.25 12.96 60.79 70.97 5.24 20.72 1.46 1.61 *：calculated by difference 
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