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首页> 外文期刊>Fuel >Influence of steam on ignition of Victorian brown coal particle stream in oxy-fuel combustion: In-situ diagnosis and transient ignition modelling
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Influence of steam on ignition of Victorian brown coal particle stream in oxy-fuel combustion: In-situ diagnosis and transient ignition modelling

机译：蒸汽对含氧燃料燃烧中维多利亚褐煤颗粒流着火的影响：原位诊断和瞬态着火模型

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In this paper, we have investigated the ignition behaviour of Victorian brown coal under the steam-ricoxy-fuel combustion conditions. Two differently ranked coal, sub-bituminous and bituminous coal, were also tested for comparison. The ignition experiments were conducted in O-2/N-2/H2O and O-2/CO2/H2O atmospheres, in an entrained flow reactor coupled with flat flame burner and in-situ optical diagnosis tools. A transient ignition model and 1-D single film model were also developed and used to predict particle ignition and the extent of char-steam gasification reaction, respectively. As has been confirmed, the injection of external steam to the furnace is beneficial in accelerating the ignition of Victorian brown coal in both air and oxy-firing modes with 21% O-2. This effect is even more pronounced for the combustion of dense particle stream. In the oxygen-enriched condition, the ignition time was similar regardless of the steam concentration in the bulk gas. The transient modelling prediction confirmed that the homogeneous water-gas shift reaction ( CO + H2OMCO2 + H-2) was the main cause for the accelerated ignition for brown coal. It produced a highly concentrated flammable gas mixture of CO and H-2 in coal particle cloud, which in turn accelerated the homogenous ignition of volatiles. This promotion effect is the most dominant for brown coal, because its volatile is rich in light hydrocarbons including gaseous CO that can readily react with the external steam via water-gas shift reaction. Moreover, the external steam triggered the heterogeneous char-steam gasification reaction for the brown coal, which further improved the overall char burnout rate. Regarding another two high-rank coals, their changes on both ignition and char burnout rate are however marginal upon the introduction of external steam, due to the shortage of gaseous volatiles ( thus no water-gas shift reaction triggered) and the difficulty for their char to undergo steam gasification reaction under the experimental conditions observed here. (C) 2016 Elsevier Ltd. All rights reserved.
机译：在本文中，我们研究了维多利亚褐煤在蒸汽-氧化燃料燃烧条件下的着火行为。还测试了两种不同等级的煤（次烟煤和烟煤）进行比较。点火实验是在O-2 / N-2 / H2O和O-2 / CO2 / H2O气氛中，在带有平面火焰燃烧器和现场光学诊断工具的气流混合反应器中进行的。还建立了瞬态点火模型和一维单膜模型，分别用于预测颗粒点火和焦炭气化反应的程度。如已证实的那样，向炉中注入外部蒸汽有利于以21％O-2的空气和氧气燃烧方式加速维多利亚褐煤的点火。对于浓颗粒流的燃烧，这种效果甚至更加明显。在富氧条件下，无论散装气体中的蒸汽浓度如何，点火时间都相似。瞬态模型预测证实，均匀的水煤气变换反应（CO + H2OMCO2 + H-2）是褐煤加速点火的主要原因。它在煤颗粒云中产生了高浓度的CO和H-2易燃气体混合物，从而加速了挥发物的均匀点火。对于褐煤，这种促进作用最为明显，因为其挥发物富含轻质烃，包括气态CO，这些轻烃很容易通过水煤气变换反应与外部蒸汽发生反应。此外，外部蒸汽引发了褐煤的异质焦炭气化反应，进一步提高了焦炭的总燃尽率。至于另外两种高级煤，由于气态挥发物的缺乏（因此不会触发水煤气变换反应）并且难以炭化，因此在引入外部蒸汽时，它们的着火和炭烧尽率的变化很小。在此处观察到的实验条件下进行蒸汽气化反应。 （C）2016 Elsevier Ltd.保留所有权利。

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