| The increasing contradiction between supply and demand of resources makes it more urgent for mineral processing to make comprehensive use of resources,even for the use of all its elements,the research on high value of mineral processing products has become the focus of the discipline development.Coal cleaning is the source of clean coal technology,and screening,float-and-sink is one of the most widely used processes in coal preparation process.In the classification products obtained by screening and float-and-sink,the mineral composition and various trace contents are often quite different.Therefore,it is of great theoretical significance and application value to study the distribution of minerals and trace elements in coal cleaning process for effectively enriching minerals and trace elements in coal and promoting efficient utilization of coal.Based on the analysis of the basic properties of raw coal and the screening and float-and-sink tests of weak clay coal in Pingshuo mining area,the products of various particle sizes and densities were obtained,and the ashing products were obtained by burning the products at high temperature,qualitative and quantitative analysis of minerals in products and ash was carried out by X-ray diffraction,gallium content was determined by chemical analysis,lithium content was determined by ICP-OES,and the correlation between minerals and trace elements was analyzed.The occurrence state of gallium and lithium in coal was preliminarily studied by step-by-step chemical extraction.Finally,the migration rules of minerals,gallium and lithium elements and the affinity relationship between gallium and lithium elements and minerals in the process flow of Antaibao Coal Preparation Plant are discussed in depth.The results are as follows:(1)Distribution rule of size range of separation about minerals,gallium and lithium shows that with the increase of grain size,the contents of minerals and gallium and lithium elements generally show a decreasing trend.Before ashing,the content of mineral kaolinite varies obviously in all particle sizes,with the highest content of kaolinite at-0.045 mm,reaching 21.22%;the content of gallium varies little in all particle sizes,basically in the range of 7.8-15.9?g/g;and the content of lithium is 456-536?g/g,which decreases slightly with the increase of particle size,and the decrease is not obvious,with the maximum and minimum value.The difference is 80?g/g.After ashing,the mineral anhydrite has the most obvious difference among the particle sizes,with anhydrite reaching 17.23%in-0.045mm particle size,gallium content higher than 30?g/g,among which the content of gallium in coal ash of small particle size is the largest,enrichment ratio is 3.36;lithium content is 330-500?g/g,which increases first and then decreases to 170?g/g with the increase of particle size,and the particle size of 0.045-0.074mm.The content of grade I reached the highest,which was 501.4?g/g.(2)The distribution rule of density size range of separation about minerals,gallium and lithium shows that with the increase of density,minerals and elements of gallium and lithium show an increasing trend.Before ashing,the content of kaolinite was the highest in all densities,+2.0g/cm~3,reaching 53.11%;gallium showed a slight increasing trend,ranging from 9-14?g/g;lithium content was 147-1987?g/g,with an obvious increasing trend with the increase of densities,the maximum and minimum difference was 1800?g/g.After ashing,the contents of anhydrite,andalusite and quartz in+2.0g/cm~3 are the highest,43.12%,14.03%and 8.25%,respectively;the content of gallium is 5-11?g/g,which gradually increases with the increase of density level the content of lithium is 50-2300?g/g,which gradually increases with the increase of density level,and the maximum and minimum difference is 2 250?g/g.(3)The results of correlation analysis between minerals,gallium and lithium before and after combustion show that kaolinite before combustion has the strongest correlation with gallium and lithium,and the correlation coefficients are 0.961 and 0.947,respectively.The correlation between gallium and quartz,andalusite and anhydrite is strong after combustion,which is 0.891,0.704 and 0.797,respectively.Quartz,hematite and andalusite have strong correlation with lithium,which are 0.921,0.965 and 0.678,respectively.In addition,in particle size test samples,the concentration factors of gallium and lithium are 0.4-0.85 and 0.62-0.98,respectively.The concentration factors of gallium and lithium were 0.5-0.85 and 0.62-0.94 in density-grade samples,respectively.It shows that gallium and lithium elements in the grading products escape in the form of gases during ashing,and most of them are enriched in ash in the form of solid state.(4)The enrichment pattern of the two elements in the step-by-step chemical extraction method shows that the content of gallium in humic acid-bound,organic and residue States is higher,24%,21%and 17%respectively.The residual state is mainly composed of silicate minerals,while clay minerals contain a large amount of silicate minerals,which indicates that gallium in Pingshuo coal mainly occurs in organic matter and clay minerals.lithium accounts for the majority of the residual and carbonate-bound states,with contents of 30%and 42%,respectively.It shows that lithium elements in Pingshuo coal enter more carbonate and silicate lattices in the extraction process,and mainly occur in carbonate and clay minerals.(5)Distribution of minerals,gallium and lithium in coal preparation process shows that:with the improvement of the degree of gangue,the contents of minerals,gallium and lithium in the products are also increasing.However,from the point of view of element enrichment rate,the enrichment effect of clean coal is the best.With the increase of gangue degree,the enrichment effect becomes worse.On the whole,no matter from the content and enrichment degree,the three products of smalls are more effective than the three products of lump coal.The correlation between gallium and lithium elements and kaolinite is strong before combustion;The correlation between gallium and lithium in coal ash and quartz is strong,while other minerals are relatively weak,which indicates that the affinity of gallium and lithium with silica-alumina oxides is good. |
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