Abstract: The high contents of sodium and calcium in Zhundong coal induce severe slagging problems in boilers' heating surfaces durning coal combustion.The slagging of coal ash has important relationship with coal ash fusibility,and the alkaline oxides in coal ash can influence the ash fusibiltiy significantly.Recent progress on the effect of alkaline oxides on coal ash fusibility was summerized.The present studies show that the addition of Na₂O can reduce the ash fusion temperatures(AFTs)significantly.The Na containing minerals with low melting point such as albite,nepheline and the eutectics they form is the main reason for reducing the AFTs.K₂O mainly exists as illite in ash,the AFTs show no significant change as the K₂O content varies.The AFTs drop first and rise later with the increase of CaO or MgO content,the change of minerals' melting point leads to the change of the AFTs.The existing form of Fe₂O₃ depends on the reaction atmosphere.The Fe in ash mainly exists as FeO in reducing conditions,Fe-containing minerals such as fayalite and hercynite can easily form eutectics thus reducing the AFTs.Further studies should be focused on the effect of alkaline oxides on the ash fusibility of Zhundong coal,to produce novel additives for resisting the slagging problems efficiently.

Key words: coal combustion, ash fusibility, alkaline oxides, Zhundong coal, slagging, deposition

摘要： 准东煤中的钠、钙含量较高，导致在燃用过程中锅炉受热面发生严重的结渣。煤灰的结渣问题与煤灰的熔融特性密切相关，灰中碱性氧化物对灰熔融特性具有重要的影响。本文综述了碱性氧化物对煤灰熔融特性的影响。现有的研究表明，添加Na₂O可以显著降低灰熔融温度，钠长石、霞石等低熔点含钠矿物质的生成及其形成的低温共熔体是灰熔融温度降低的主要原因。灰中K₂O主要以伊利石的形式存在，对灰熔融温度的影响较小。随灰中CaO和MgO含量的增加，灰熔融温度具有先降低后升高的变化趋势，矿物质熔点的变化是灰熔融温度变化的主要原因。灰中Fe₂O₃的存在形式与反应气氛有关。在还原性气氛下，铁主要以FeO的形式存在，铁橄榄石、铁尖晶石等含铁矿物质容易形成低温共熔体，使灰熔融温度降低。未来应着重研究碱性氧化物对准东煤灰熔融特性影响的机理，开发抑制准东煤结渣的高效添加剂。

关键词: 煤燃烧, 灰熔融特性, 碱性氧化物, 准东煤, 结渣, 沉积物