Fate of trace elements and ash formation during combustion and gasification of coal

煤炭占加拿大化石燃料总储量的65%以上，每年用于发电的煤炭近6000万吨。因此，清洁煤技术的发展是一个优先研究领域，需要在提高效率和减少污染物排放方面不断改进。煤中存在的微量元素，如汞、砷和硒，即使以百万分之一的水平存在，也会引起公众健康关注。决定煤中微量元素排放的因素有两个：煤的特性和燃烧环境。煤的特征包括有机质和无机物的非均质性，包括煤中微量元素的分布。这些元素大多在燃烧过程中蒸发，并主要凝结在难以捕获的细粉煤灰颗粒上。te在粉煤灰颗粒中的任何保留都受到它们与单个煤和矿物颗粒中的其他矿物的结合的强烈影响。煤-矿物结合体在细颗粒的形成、TEs的释放和随后的凝结过程中起着重要作用。

Coal represents more than 65% of total fossil fuel reserves in Canada and almost sixty million tons of coal is used every year for electricity production. Clean coal technology development is, therefore, a priority area of research and needs continuous improvements in increased efficiency and decreased pollutant emission. Trace elements (TEs) such as mercury, arsenic and selenium present in coal, even when present in parts per million levels, are of public health concern. There are two factors that determine the emission of trace elements: coal characteristics and the combustion environment. Coal characteristics include heterogeneity in both organic and inorganic matter including the distribution of trace elements in coal. These elements mostly evaporate during combustion and condense primarily on fine fly ash particles that are difficult to be captured. Any retention of the TEs in fly ash particles is strongly influenced by their association with other minerals in individual coal and mineral grains. The coal-mineral associations play an important role in the formation of fine particles, release of TEs and their subsequent condensation.