Research progress onmigration and transformation behavior of hazardousmineral matter in coals during coal combustion

Minerals and potentially hazardous trace elements in coals are the main origin of negative effects，such as environmental pollution，during coal combustion. There are so many minerals and trace elements in coals，and their transformation and migration during coal combustion are extremely complex，which are closely related to their emissions. Based on the previous studies，behavior of common minerals and trace elements in coals during coal combustion was reviewed from a coal geology insight，which can provide a reference for related researches and for controlling emissions. During coal combustion，thermal transformation of minerals involves of the processes of breaking，decomposition，evaporation，agglomeration，fusion，condensation，etc. Similar with minerals，emissions of trace elements during coal combustion also show distinctive differences，mainly depending on their volatiling and combustion conditions. Fate of mineral matter after coal combustion includes slag，bottom ash，fly ash，and suspended particles in coal-fired flue gas. Behavior of mineral matter during coal combustion is mainly influenced by the geological characteristics of mineral matter in coals and by the conditions of coal combustion process. Temperature and atmosphere are the two mostly significant factors effecting on their behavior. At present，there were some theories about the transformations of mineral matter in coals during combustion established preliminarily. Nevertheless，general regularities are rarely proposed and summarized. And studies on original geology factors affecting on the behavior of mineral matter during coal combustion are inadequate. The specific aspects are as follows. Enrichment and differentiation mechanism of mineral matter in nature and during coal combustion，potential relationship between geological characteristics of mineral matter and their thermal evolution behavior，and the dual effect mechanism of geological setting and combustion condition on the thermal behavior of mineral matter require to be studied further.