Abstract Oxy-steam combustion and devolatilization performance of three different coals (anthracite, blend of bituminous coals and low-rank coal) was studied in a thermobalance with a water vapour furnace under variable steam concentrations (0, 20, 40 and 70 vol% H2O) in N2 and CO2. Two oxygen concentrations were used during the combustion tests (20 and 30 vol%). Devolatilization behaviour was similar under N2 and CO2 atmosphere and increasing steam concentration did not affect significantly the observed reactivity and the reaction temperature range. Replacing CO2 with 20 vol% H2O during combustion tests produced a decrease in ignition and burnout temperatures. When H2O content increased to 40 and 70 vol%, this effect was only found with high-rank anthracite. Maximum mass loss rates for the low-rank coal with high volatile content were up to four times higher than with the other two coals. During direct oxidation experiments, DTG curves of anthracite and the coal blend showed a double peak, corresponding to devolatilization and oxidation reactions. This allowed determining independent kinetic parameters (Ea and A) for both stages. An only DTG peak was detected with the low-rank coal since devolatilization and oxidation reactions took place simultaneously owing to its high reactivity. Devolatilization and oxidation kinetics followed a first-order reaction using the Coats-Redfern integral method. Significant differences were not observed between the activation energies of the three coals when comparing conventional (N2), oxy-fuel (CO2) and oxy-steam conditions (70 vol% H2O in CO2), although Ea values were higher for the devolatilization stage than for the oxidation process.

中文翻译：

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氧蒸汽燃烧：增加蒸汽浓度对煤反应性的影响

摘要 在不同蒸汽浓度（0、20、40 和 70 vol% H2O）下，在水蒸汽炉中使用热天平研究了三种不同煤（无烟煤、烟煤和低阶煤）的富氧蒸汽燃烧和脱挥性能。 ) 在 N2 和 CO2 中。在燃烧测试期间使用了两种氧气浓度（20 和 30 vol%）。在 N2 和 CO2 气氛下脱挥发分行为相似，增加蒸汽浓度对观察到的反应性和反应温度范围没有显着影响。在燃烧测试期间用 20 vol% H2O 代替 CO2 会降低点火和燃尽温度。当 H2O 含量增加到 40 和 70 vol% 时，这种效果只在高品位无烟煤中发现。挥发分含量高的低阶煤的最大质量损失率是其他两种煤的四倍。在直接氧化实验中，无烟煤和混煤的DTG曲线呈现双峰，对应于脱挥发分和氧化反应。这允许确定两个阶段的独立动力学参数（Ea 和 A）。低阶煤由于其高反应性而同时发生脱挥发分和氧化反应，因此仅检测到 DTG 峰。脱挥发分和氧化动力学遵循使用 Coats-Redfern 积分方法的一级反应。在比较常规 (N2)、氧燃料 (CO2) 和氧蒸汽条件（CO2 中 70 vol% H2O）时，三种煤的活化能之间未观察到显着差异，