Characterization of temperature criteria using gas-phase fuel streams for MILD coal combustion
Characterization of temperature criteria using gas-phase fuel streams for MILD coal combustion
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DOI：
10.1016/j.fuel.2021.120445
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发表时间：
2021-07
期刊：
影响因子：
7.4
通讯作者：
Hang Zhou;J. McConnell;T. Ring;J. Sutherland
中科院分区：
文献类型：
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作者：
Hang Zhou;J. McConnell;T. Ring;J. Sutherland
当反应物入口温度（T入口）高于反应物自燃温度（T自燃）且反应后的升温（Δ T= T max-T入口）低于T自燃时，实现轻度燃烧。对于煤的燃烧来说，获得T入口和T自燃的方法是模糊的，因为随着颗粒升温，在不同的温度和不同的时间，煤颗粒通过汽化、脱挥发、焦油/烟尘反应和炭氧化/气化等多种燃料流释放出来。本文提出了一种利用各子过程的反应速率和着火前反应器内气体和颗粒温度分布来确定煤燃烧中气相燃料流的方法。采用燃料流与氧化剂的混合物来获得T进气和T自燃，作为轻度煤燃烧的温度标准。举例来说，该方法用于确定达到轻度煤燃烧所需的稀释率。对于本研究中使用的两种类型的煤（伊利诺斯州6号煤和贵州煤），即使气体燃料混合物的温度和成分受到煤的等级的影响，MILD煤的燃烧状态也不会发生显著变化。观察到，随着入口温度和最高温度的降低，达到MILD状态所需的稀释率kv随氧化剂温度的降低而增加。实现轻度煤燃烧所需的稀释率对焦油/煤烟反应模型并不敏感，即使是在忽略煤烟形成而使用c2h2的简化模型中也是如此。
MILD combustion is achieved when the reactants’ inlet temperature (T inlet) is higher than the self-ignition temperature of the reactants (T self-ignition) and the temperature increase upon reaction (Δ T= T max-T inlet) is lower than T self-ignition. The method to get T inlet and T self-ignition is ambiguous for coal combustion because the multiple fuel streams are released from coal particles through vaporization, devolatilization, tar/soot reaction and char oxidation/gasification at different temperatures and different times as the particles heat up. We propose a method to determine the gas-phase fuel streams in coal combustion using the reaction rate of each subprocess and gas and particle temperature profiles in the reactor before ignition. The mixture of fuel streams with oxidizer is used to get T inlet and T self-ignition for the temperature criteria for MILD coal combustion. By way of example, this method is applied to identify the required dilution rate needed to reach MILD coal combustion. The MILD coal combustion regime does not shift significantly for the two types of coal used in this work (Illinois# 6 and Guizhou), even with the temperature and composition of the gas fuel mixture affected by the rank of coal. It is observed that the required dilution rate, K v, to reach MILD regime increases for lower oxidizer temperature, with the decrease of both inlet and maximum temperatures. The required dilution rate to achieve MILD coal combustion is not sensitive to the model for tar/soot reactions, even for a simplified model that uses C 2 H 2 for tar while neglecting the formation of soot.