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Slagging and fouling of Zhundong coal at different air equivalence ratios in circulating fluidized bed

机译：准东煤在循环流化床中不同空气当量比的结渣与结垢。

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Circulating fluidized bed (CFB) with low operating temperatures may become an appropriate solution to the utilization of high-Na Zhundong coal. In this paper, one kind of Zhundong coal with 3.92% Na2O in coal ash was used as fuel, and its slagging and fouling characteristics at different air equivalence ratios (ERs) were systemically investigated in 0.4 t/d CFB test system to determine a better utilization scheme of Zhundong coal. The results show that ash-related problems still occurred when this high-Na coal was used in CFB, which was greatly influenced by ER. At the reducing atmosphere (ER < 1.0), slagging obviously occurred in the riser at similar to 940 degrees C. Na-based species reacted with the SiO2-rich bed material to form low-melting-temperature sodium silicates (Na2O.nSiO(2)). The formed sodium silicates covered bed material particles and increased their stickiness. These sticky particles agglomerated and adhered onto the high-temperature metal surfaces by adhesion force or inertial force, resulting in slagging. During slagging process, Ca, Mg and Fe acted as fluxing agents. This type slagging related to the SiO2-rich bed material might be reduced or even avoided via the replacement of the bed material. At the oxidizing atmosphere (ER > 1.0), fouling on tail heating surfaces at medium-low temperatures (607-735 degrees C) was the main ash related problem. The released AAEM-based species were transported towards low-temperature surfaces by the mechanisms of diffusion, condensation and aggregation, or thermophoresis, resulting in a layered deposition.. The inner layer of deposits with micron grain sizes, which was mainly composed of Na2SO4 and K2SO4, played a key role at the initial deposition stage. Besides, two kinds of aggregated particles separately rich in alkali silicates and Ca-based species were also important for fouling. (C) 2017 Elsevier Ltd. All rights reserved.
机译：运行温度低的循环流化床（CFB）可能成为利用高钠准东煤的合适解决方案。本文以粉煤灰中Na2O含量为3.92％的准东煤为燃料，在0.4 t / d CFB试验系统中系统研究了不同空气当量比（ER）下的结渣特性。准东煤炭利用方案。结果表明，在CFB中使用这种高Na煤时，仍然存在与灰分有关的问题，这受ER的影响很大。在还原气氛（ER <1.0）下，冒口明显在940摄氏度左右发生结渣.Na基物质与富含SiO2的床层材料反应形成低熔点硅酸钠（Na2O.nSiO（2 ））。所形成的硅酸钠覆盖床材料颗粒并增加其粘性。这些粘性颗粒通过粘附力或惯性力附聚并粘附在高温金属表面上，导致结渣。在结渣过程中，Ca，Mg和Fe充当助熔剂。可以通过更换床层材料来减少甚至避免与富含SiO2床层材料有关的这种结渣现象。在氧化气氛（ER> 1.0）下，中灰（607-735摄氏度）的尾部加热表面结垢是与灰分有关的主要问题。释放的基于AAEM的物质通过扩散，冷凝和聚集或热泳的机理向低温表面传输，导致分层沉积。内层的微米级颗粒沉积物，主要由Na2SO4和在初始沉积阶段，K2SO4起着关键作用。此外，两种分别富含碱金属硅酸盐和钙基物质的聚集颗粒对于结垢也很重要。 （C）2017 Elsevier Ltd.保留所有权利。

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