Influence of multiple air staging and reburning on NOx emissions during co-firing of low rank brown coal with woody biomass and natural gas
Influence of multiple air staging and reburning on NOx emissions during co-firing of low rank brown coal with woody biomass and natural gas
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DOI：
10.1016/j.apenergy.2016.01.081
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发表时间：
2016-04
期刊：
影响因子：
11.2
通讯作者：
N. Hodžić;A. Kazagić;I. Smajević
中科院分区：
文献类型：
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作者：
N. Hodžić;A. Kazagić;I. Smajević
对煤、木质生物质和天然气混烧过程中NOx排放进行了试验研究。研究的目的是调查的协同影响，先进的，同时适用于不同的主要减少措施对氮氧化物的排放在多燃料燃烧系统。在一台装有旋流燃烧器和燃尽风系统（OFAS）的20 kW PC实验室炉上进行了试验，改变了燃料成分、燃烧温度、总风量、空气分配（空气分级和OFA）和燃料分配（再燃）等工艺条件。以中波斯尼亚煤盆地的三种低阶褐煤及其混合煤为原料，与木屑、天然气进行了对比试验。木质生物质部分在燃料混合物中在5和20%w之间变化，而用于再燃烧的天然气部分在5和10%th之间变化。应用不同的工艺温度来研究它们对NOx排放的影响。除了多空气分级，燃料分级对NOx排放的影响已经被研究，首先通过分级基本燃料，即煤和木质生物质，然后通过天然气再燃。在多燃料的情况下，研究表明，在相同的过程温度下，在0.1共烧时可以实现超过50%的NOx减少，如果工艺温度降低，则为67%。已经表明，在高于1400 °C的工艺温度下，在没有燃料分级和OFA关闭的情况下，煤混合物产生最高的NOx排放（在6%O2干态下高于1100 mg/mn 3）。另一方面，NOx排放量显着减少与分级空气部分的增加，也与燃烧器和OFA喷嘴之间的距离的增加。此外，如果再燃烧是由天然气与OFA打开，NOx排放量减少到500毫克/立方米以下，在6%的O2干。如果温度降低到1100 °C以下，在6%O2干态下，NOx排放量降低到400 mg/mn 3。结果表明，煤、生物质和天然气混合燃料系统的设计和运行可以得到优化，有利于进一步降低NOx的排放。
The paper presents an experimental research on NOx emissions during co-firing of coal with woody biomass and natural gas. The aim of the research was investigation of synergetic influence of advanced and simultaneously applied different primary reduction measures on NOx emissions in a multifuel combustion system. During the tests run on a 20 kW PC lab-scale furnace equipped with a swirl burner and over fire air system (OFAS), the process conditions such as fuel composition, combustion temperature, overall air amount and air distribution (air staging and OFA) and fuel distribution (reburning) have been varied. Three single low rank brown coals from Middle Bosnia coal basin and their blends have been used in combination with sawdust and natural gas. Woody biomass fraction was varied between 5 and 20%w in the fuel blend, while the fraction of natural gas used for reburning was varied between 5 and 10%th. Various process temperatures were applied to investigate their influence on the NOx emissions. Besides multiple air staging, effects of the fuel staging in respect to the NOx emissions have been investigated, first by staging the basic fuels, that is coal and woody biomass, and then by natural gas reburning.In a multi-fuel case investigated, it has been demonstrated that over 50% of NOx reduction could be achieved at 0.1 cofiring at the same process temperature, and 67% if the process temperature is reduced. It has been shown that the coal blends at process temperatures above 1400 °C, with no fuel staging and OFA switched off, yield highest NOx emissions (above 1100 mg/mn3at 6% O2dry). On the other side, NOx emissions reduced significantly with the increase of the staging air portion and also with an increase in the distance between the burner and OFA nozzle. Furthermore, if the reburning is performed by natural gas with OFA switched on, NOx emissions reduce below 500 mg/mn3at 6% O2dry. If the temperature is reduced below 1100 °C, NOx emissions decreased to 400 mg/mn3at 6% O2dry. The results confirmed that the design and operation of multi-fuel system using coal, biomass and gas could be optimized, such benefiting further reduction of NOx emissions.