Study Of Transformation Behavior Laws Of Trace Elements (Hg, As, F, Cl) During Coal Processing

Study on the law of distribution of trace elements-percury, arsenic, fluorine and chlorine during size analysis and washability tests for three different coal. The results show that the contents of ash, total sulfur, pyrite and mercury, arsenic, and fluorine in the fractions of sizing and float-sink tend to reduce with the granule reduce and density of the medium reduce, the change of content of chlorine is in reverse. The law of distribution of mercury and arsenic is very similar to that of pyritic sulfur and the law of distribution of fluorine is very similar to that of ash (mineral matter). This indicate mercury and arsenic in coal are associated minerals with pyrite and fluorine is associated minerals with other inorganic compounds, chlorine in coal mainly associates with organic compounds, which is demonstrated by their inorganic /organic affinities result from above tests. The regression models of relationship between forms of sulfur and the contents of mercury and arsenic are highly significant, the regression models of relationship between the content of minerals and the contents of mercury and arsenic are also highly significant. Them can be used for calculating contents of mercury and arsenic in the fractions of sizing and float-sink separately. The ash and sulfur in coal can not only removed with cleaning-preparation of coal, but also the mercury, arsenic and fluorine can be removed. The (26-85)% of mercury, arsenic and fluorine can be removed depending on the type of coal and different trace elements. Study on the law distributing behavior of trace elements-mercury, arsenic, fluorine and chlorine during pilot-scale fluidised bed combustion (FBC) for six different coals and boiler combustion in two unit for four different coals. The results indicate that trace elements-percury, arsenic, fluorine and chlorine are concentrated in the fly ash except for those to be discharged into the air, the contents of them in fly ash are more higher than that in bottom residue. The test shows that the both of adding CaO in coal or adding CaO in hop-pocket filter can reduce emissions of SO2 effectively in FBC, the former also can reduce the emissions of Hg, As and F, but the later cannot. The content of residue carbon in the fly ash has a great influence on the content of Hg, As, F and Cl in that. The fly ash can be used for absorbing gas mercury to reduce the emission mercury to the air. Study on the law of distribution of trace elements-percury, arsenic, fluorine and chlorine in the process of coal-liquefacting for four different coals. The results indicate contents of mercury, arsenic and chlorine in coal liquefaction oils are very low,contens of fluorine is higher than that in coal.Con.tents of them in liquefaction water are higher than the oil,but the quite parts of them emitted into the air. At the same time, the methods of determination of mercury in coal and in ash and determination of mercury, arsenic, fluorine and chlorine in liquefaction oils are also studied and improved. The developed methods used in these researches have been demonstrated to be accuracy and reliable by Round-Rubin tests of international inter- laboratory, Certified Reference Material tests and standard -adding recovery tests. The research results in this paper make people understand deeply the law of transformation of mercury, arsenic, fluorine and chlorine in coal under the process of cleaning-preparation, combustion and liquefaction of coal, and hence estimate the possible pollution came from above p...