| The key to coal flotation is how to achieve effective mineralization between coal particles and the air bubbles,meanwhile reducing the entrainment of some inorganic minerals into the clean coal.To solve the problem above,seven coal samples which have different metamorphic degrees and four coal samples of different sizes were selected to be research objects.Based on characteristic analysis,the flotation speed tests were completed respectively by adjusting dosage of flotation reagents,slurry pretreatment of using self-made anionic surfactants under the other same conditions.The effective adhesion rate of bubble-particles were calculated by element analysis using XRF,qualitative and semi-quantitative analysis using XRD,coupled with chemical equation before and after incineration.Thus,the rule of the effective sticking probability of bubble-particles was studied which will have great significance in enriching flotation theory,reducing ash and sulfur content.The functional groups and minerals of samples were analyzed by using XRF,XRD and FT-IR.The result showed that the main minerals contained in coal samples are kaolinite and quartz,followed by calcite,pyrite and a small amount of montmorillonite and gypsum.The content of quartz is higher than that of kaolinite in meager-lean coal and lignite,while opposite result was found among the other five coal samples.The strongest absorption peaks of oxygen-containing functional groups is found in lignite while there are the same trends in the other five coal samples.Also,the result showed that the main minerals contained in weakly caking coal are quartz and kaolinite which has the highest content.The strongest absorption peak of kaolinite was found in the coal sample(-0.074 mm)while the other ones have the same trend.The effective adhesion rate of bubbles-coal particles gradually reduced along with floatation time and the maximum value is 68.31 % during the whole process for meager-lean coal.For lignite,it maintained around 5.00 %.In terms of different sizes of coal samples,the optimum effective sticking probability of bubbles-particles appeared when the fraction is 0.250-0.125 mm while it is almost the same when the particle size is-0.074 mm.For coking coal,the number is 60.59 % without pretreatment and the one is 66.33 % using surfactant pretreatment.For the effective adhesion rate of bubble-kaolinite and quartz,the value of meager-lean coal and coking coal are far more larger than that of the others.The effective adhesion rate of sample(0.250-0.125 mm)fluctuated largely while the sample of 0.125-0.074 mm kept steady.In terms of the dosage of flotation reagents,the optimum effective adhesion rate of bubble-kaolinite arrived at 27.633 % and the maximum one of bubble-quartz is 28.910 %.For coal samples after surfactant pretreatment,the maximum effective adhesion rate is 32.734 % with C12 DPPS of 30g/t.The amount of the best adhesion rate of bubble-calcite and pyrite were almost around 1.00 % for all the seven coal samples.For different sizes of coal samples,the best adhesion rate range of bubble-pyrite was 0-0.8 % and that of bubble-calcite was 0-1.7 %.When adding various dosage of flotation reagents,the effective adhesion rate fluctuation range of bubble-calcite and pyrite were separately 0-3.5 % and 0-1.6 %.When considering coal slurry of pretreatment using surfactant,the effective adhesion fluctuation range of bubble-calcite and pyrite were separately 0-2.5 % and0-0.75 %.The elements including metamorphic degrees,sizes,dosage of flotation reagent,surfactant pretreatment have significant influence on kaolinite-entrainment and it would be sharpen using the surfactant pretreatment.Also,quartz-entrainment would be influenced obviously by the metamorphic degrees,what's more,these roles mainly played within one minute. |
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