| The clean and efficient use of coal resources is one of the priority development areas of China energy industry.The separation of macerals is an important way to achieve this goal.In this paper,based on the difference in surface properties of the main macerals(vitrinite and inertinite)of different coal seams in Shenfu mining area,the topic of this thesis introduces the oily bubble flotation method with low consumption and high selectivity of low-rank coal flotation reagent into the maceral flotation separation test.Systematic analysis of the surface(structure)properties of macerals particles of samples.From the perspective of surface structure and properties of surfactant-modified oily bubbles and macerals,the mechanism of adhesion between oily bubbles and the maceral particles is elucidated.The research results have theoretical and practical guiding signific ance for the separation and utilization of the macerals.(1)Study on sample preparation of micro-components of high-purity macerals.In order to obtain high-enrichment samples of macerals for flotation,the floatation-centrifugal method is used to separate and enrich the 5-2 coal seam(DLT5'2)of Daliuta mine and the 1-2 and 2-2 coal seam of Bulianta mine(BLT1-2 and BLT2-2),and obtain the samples of vitrinite and inertinte.The analysis results of density composition of raw coal show that the vitrinite is mainly distributed in the density level of 1.30?1.38 g/cm3,and the inertinite is mostly concentrated in the density class of 1.36?1.44 g/cm3.The floatation-isodensity centrifugation method was used to first separate the vitrinite-rich and inert-rich coal samples with a limit density of 1.38 g/cm3,and then further separate and enrich with the limit densities of 1.35 g/cm3 and 1.44 g/cm3,and get the vitrinite and inertinite.Analysis of the basic properties of coal samples and their macerals in different coal seams shows that the properties of samples are similar,and the differences in their macerals properties are small.The vitrinite had smaller ash content,O/C ratio,and S/C ratio than the inertinite.The particle size composition analysis test shows that the above three coal seam samples all show smaller particle size and higher ash content;DLT5-2,BLT1-2 vitrinite and inertinite are relatively enriched at 0.020?0.070 mm particle size;BLT2-2 vitrinite and inertinite are relatively enriched at 0.010?0.050 mm particle size.(2)Research on the surface structure and properties of coal samples and their macerals.Through XRD,FTIR,XPS,BET and contact angle measuring instruments and other analytical test methods,the surface structure and properties of the raw coal,vitrinite and inertinite of the three coal seams were studied.The results show that the above three coal seam samples and their macerals have small differences in the types of minerals,types of oxygen-containing functional groups and their existing forms.The raw coal and inertinite have relatively high mineral content.There are quartz and clay minerals,such as kaolinite and muscovite.The vitrinite contains a small amount of quartz minerals;the coal sample contains-CH3 and-CH2-hydrophobic groups,organic sulfur-containing-S-H functional groups,and Si-O-Si groups.Combined with the analysis of FTIR and XPS results,the oxygen-containing functional groups of coal samples are mainly hydroxyl(-OH)and ether group(C-O-C),with a small amount of carboxyl(O-C=O)and carbonyl(C=O),and in the fusain the carbonyl group(C=O)and carboxyl group(O-C=O)are higher than vitrain.The analysis of pore distribution and structure shows that the the sample is mainly micropores,the adsorption isotherm curve of samples are S-shaped,which belongs to the typical type ? curve,and the desorption curve belongs to the D2 desorption loop.Analysis of the contact angle of raw coal found that the contact angles of DLT5-2,BLT1-2 and BLT2-2 coal samples with water were 70.11°,66.40°and 69.75°,and the contact angles with diesel were 18.51°,17.00° and 24.70°,the samples showed oleophobicity and hydrophobicity.The samples DLT5-2 and BLT1-2 were more likely to adhere to diesel and be trapped by diesel collector.(3)The oily bubble flotation method is used to study the effect of modified oily bubbles on the separation effect of macerals in different coal seams.Through comparison of different flotation experiments,it was found that oily bubble flotation can greatly improve the recovery rate of concentrate and reduce the amount of reagent(1.5 L/min,or 1.98 kg/t).The addition of modified agent improves the recovery rate of concentrate in oily bubble flotation.In oily bubble flotation test of modified diesel collector,the best modified diesel collectors for three coal samples of DLT5-2,BLT1-2 and BLT2-2 are DH,DH and 2-EH modified diesel collectort,the best modified agent and diesel mass ratio of DLT5-2 the vitrine-rich group and the inert-rich group both is 0.04,while BLT1-2 and BLT2-2 are 0.04(the vitrinite)and 0.06(the inertinite).(4)Study on the adhesion mechanism between modified oily bubbles and macerals.According to the results of induction time measurement,the induction time of the vitrinite-rich and the inert-rich groups the air bubbles is higher than diesel oily bubbles.Activated oily bubbles can reduce the contact time with coal particles and cause adhesion,thereby improving the flotation efficiency.The induction time between 2-EH modified oily bubbles and DLT5-2 maceral particles is shorter.The induction time between 2-EH and DH modified oily bubbles with BLT1-2 and BLT2-2 maceral particles are relatively small,but DH modified oily bubbles can expand the difference between different macerals,so DH modified oily bubble is better.At the same time,the contact angle measurement results show that the contact angle of the modified diesel and the vitrine-rich group is slightly smaller than the inert-rich group,indicating that the vitrine-rich group is more lipophilic and easily adheres to the modified agent.Comparing the original contact angle of the coal sample,it can be found that the addition of the modifying agent can reduce the contact angle of the oily bubble and the macerals. |
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