Combustion of Coal Chars in O2/CO2 and O2/N2 Mixtures: A Comparative Study with Non-isothermal Thermogravimetric Analyzer (TGA) Tests
Combustion of Coal Chars in O2/CO2 and O2/N2 Mixtures: A Comparative Study with Non-isothermal Thermogravimetric Analyzer (TGA) Tests
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DOI：
10.1021/ef9002928
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发表时间：
2009-09-01
期刊：
影响因子：
5.3
通讯作者：
Liu, Hao
中科院分区：
文献类型：
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作者：
Liu, Hao
以高挥发分烟煤和无烟煤为原料，在热重分析仪（TOA）上对两种煤焦进行了非等温燃烧试验。在O-2浓度为3%、6%、10%、21%和30%的O-2/CO2和O-2/N-2混合气体中燃烧半焦。A.在2.5、5、7.5、10和12.5K/min的线升温速率下，对每种煤焦进行了一系列的非等温燃烧试验。本文应用四种不同模型的自由等转化率法，根据实验数据，测定了煤焦在O2-/CO2混合气体中的燃烧活化能。结果表明，四种方法测定的半焦活化能均随半焦转化率的增加而减小。在较高的炭转化水平下变得更加明显的扩散效应被认为是上述观察结果的主要原因。在忽略扩散影响的情况下，用最精确的方法求得的煤焦活化能与文献值吻合较好：无烟煤焦为138.03 kJ/mol，烟煤煤焦为127.83 kJ/mol。发现每种炭的测量的燃烧速率近似地位于O-2/CO2混合物中的O2浓度的一阶。
Two chars prepared from parent coals of a high-volatile bituminous Coal and an anthracite coal were subjected to non-isothermal combustion tests in a thermogravimetric analyzer (TOA). The chars were burned in mixtures of O-2/CO2 and O-2/N-2 with O-2 concentrations of 3, 6, 10, 2 1, and 30%. A. range of nort-isothermal combustion tests of each char were conducted with linear heating rates of 2.5, 5, 7.5, 10, and 12.5 K/min. Detailed comparisons of measured char combustion rates show that replacing the inert nitrogen gas in the oxidizer with CO2 has very little influence oil the measured combustion rates of coal chars atanv char conversion level under the conditions of the experiments. Four different models free isoconversion methods using the experimental data were applied to determine the activation energies of the combustion of chars ill O-2/CO2 mixtures. The results show that the activation energy of each char, determined by any of the four methods, decreases with the increase of the char conversion level. The effect of diffusion, which becomes more pronounced at higher char conversion levels, is believed to be the main reason for the above observation, At a low char conversion level (e.g., 20%), when the effect of diffusion call be neglected, the activation energy of each char determined by the most accurate method under the conditions of this study was found to be in good agreement with literature data: for the anthracite char, it was 138.03 kJ/mol, and for the bituminous coal char, it was 127.83 kJ/mol. The measured combustion rate of each char was found to lie approximately first-order to the concentration of 02 ill the O-2/CO2 mixtures.