Study On Occurrence Of Fluorine In Guizhou Coal And The Distribution In Flotation Process

Fluorine is one of trace elements in coal of serious harm to the ecological environment. The air fluoride pollution has posed a huge threat to human health. This paper took high fluoride coal in Guizhou Province as the object,researched the content and occurrence of fluorine in coal as well as the distribution law on coal flotation process.Two samples were analysised by XRF,XRD,SEM+EDS,and size and density analysis. It showed that kaolinite and quartz are the major minerals in the two samples,the grain sizes of the two samples are relatively small, and the two samples are refractory coal.A high-temperature combustion hydrolysis test device platform was established to deal with coal samples. Total fluorine content in coal was determined by ion chromatography method, which was compared with selective electrode method. The ion chromatography method was ascertained to determine the content of fluorine in coal in the subsequent tests.Occurrence mode of fluorine in coal was studied by using the float-and-sink analysis, Extraction experiment, Sequential extraction experiment and the relaionship between fluorine and phosphorus in coal. The conclusions indicated that Fluorine content in two coal sample depends on the type and the content of gangue minerals, it also showed that the major trends of fluorine exist in coal of fine-grain,and high density, fluorine mainly occur in the insoluble inorganic minerals in two samples, the relative contents of the residual fluorine in coal samples are 70.77% and 57.98%,respectively, this faction fluorine exist in silicates after leaching.In addition, the results of progressive release flotation test shown that the cumulative removel rate for fluoride increases with the decrease of the cumulative clean ash,while the cumulative removal rate for phosphorus decreases,indicating that no positive correlation between fluorine and phosphorus exists,the fluorapatite is not the occurrence mode of fluoride in LPS sample.A series of flotation tests was carried out, investigated the impact of the factors, including flotation time, flotation concentration, as well as the collector and frother dosage. And a relatively optimized flotation conditions was obtained by the tests. The flotation time is 3min; the concentration is 80 g?L-1; the dosage of collector and frother are 150 g?t-1 and 100 g?t-1, respectively. The depressant was added into different processes under the conditions above. And then its impacts on the distribution of fluorine in coal in flotation process were discussesed. The distribution rate of fluorine in clean coal decreases, with the increase of depressant dosage in three processes,which indicated that fluorine in coal is more likely to enrich in tailing coal in flotation process,and the addition of sodium hexametaphosphate as depressant has changed the distribution rate of fluorine in flotation products,which also can used to prove that the main occurrence of fluorine in coal exists in the silicate minerals.