Char characterization and DTF assays as tools to predict burnout of coal blends in power plants
Char characterization and DTF assays as tools to predict burnout of coal blends in power plants
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DOI：
10.1016/j.fuel.2004.08.008
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发表时间：
2005
期刊：
影响因子：
7.4
通讯作者：
Claudia Ulloa;A. Borrego;S. Helle;A. Gordon;X. García
中科院分区：
文献类型：
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作者：
Claudia Ulloa;A. Borrego;S. Helle;A. Gordon;X. García
本研究的目的是预测电厂混合煤燃烧的效率偏差。与单煤相比，共混物的燃烧表明，某些共混物的燃烧行为本质上是非加性的。使用了两个发电厂混合燃烧的煤饲料和飞灰的样本，以及在与工业锅炉相似的温度和加热速率下在滴管炉（DTF）中产生的母煤的焦炭。这些煤种的内在动力学参数、燃烧剖面和岩相特征与电厂燃尽和DTF实验具有良好的相关性。DTF中的混合燃烧再现了期望加权平均值的正燃尽和负燃尽偏差。这些倦怠偏差以前归因于平行或平行串联的氧气竞争途径。具有相似特征的低阶煤的共混物在形貌、光学结构和反应性方面没有发现偏差。在煤的混合物中发现了负偏差，其等级适度不同，并被解释为与长期竞争有关。在这种情况下，粉煤灰中富集了来自最不活跃的炭的物质，但也鉴定了来自最活跃的炭的未燃烧物质。与加权平均值相比，在等级非常不同的煤混合物中观察到改善的燃烬，并解释为短相互作用期的结果，随后是在更有利于其燃烧的条件下较不活泼的炭燃烧的时期。在这种情况下，只有来自最不活泼的炭的未燃烧物质在粉煤灰中被识别出来。
The aim of this study is to predict efficiency deviations in the combustion of coal blends in power plants. Combustion of blends, as compared to its single coals, shows that for some blends the behavior is non-additive in nature. Samples of coal feed and fly ashes from combustion of blends at two power plants, plus chars of the parent coals generated in a drop-tube furnace (DTF) at temperatures and heating rates similar to those found in the industrial boilers were used. Intrinsic kinetic parameters, burning profiles and petrographic characteristics of these chars correlated well with the burnout in power plants and DTF experiments. The blend combustion in a DTF reproduces both positive and negative burnout deviations from the expected weighted average. These burnout deviations have been previously attributed to parallel or parallel-series pathways of competition for oxygen. No deviations were found for blends of low rank coals of similar characteristics yielding chars close in morphology, optical texture and reactivity. Negative deviations were found for blends of coals differing moderately in rank and were interpreted as associated with long periods of competition. In this case, fly-ashes were enriched in material derived from the least reactive char, but also unburnt material attributed to the most reactive char was identified. Improved burnout compared to the weighted average was observed for blends of coals very different in rank, and interpreted as the result of a short interaction period, followed by a period where the less reactive char burns under conditions that are more favorable to its combustion. In this case, only unburned material from the least reactive char was identified in the fly-ashes.