Quantum Chemistry Calculations And Experimental Research On The Performance Of Hydrocarbon Flotation Reagents

Coal preparation is the basis of clean coal technology. Flotation is the mosteffective separation method for the fine coal and flotation reagents greatly affectthe flotation result. Efficient and reasonable application of reagents can flexiblycontrol the flotation process and improve economic efficiency. The research ofrelationship between the molecules structure and properties of flotation reagentsshould be studied before the find and apply of new type and efficient drug.Quantum chemical calculations proved to be a good research method for thestudy of flotation mechanism and the design of new flotation reagents.In this paper, the proper structure model of hydrocarbon collector is builtby using the quantum chemistry calculations software-Gaussian. Parameters ofthe electronic structure such as geometric configuration, net charge and theconstituents of front molecular orbital are calculated by the software, whichare optimized by using the Density Functional Theory (DFT) at theB3LYP/6-31G level. So are the adsorption energy between coal and agents. Themechanism between coal and flotation agent are revealed from the perspectiveof quantum chemistry, which are in accord with the results of experimental.Proximate analysis, FTIR and XPS analysis were carried on for Datongcoal samples. These analysis show that the coal is weakly caking coal with highcontent of oxygen on the surface. Sub-bituminous coal structural element modelare selected to quantum chemical calculations.The quantum chemistry calculations are conducted to coal and flotationagent with hydrocarbon collectors whose carbon atom number is12,14and16 respectively as the research object. The proper structure model of coal andparameters of the electronic structure such as geometric configuration, netcharge and the constituents of front molecular orbital were studied by using theGaussian. The results showed that the chain length has little effect on theperformance of same series hydrocarbon flotation reagents; the chargedistribution, bond lengths, bond angles have a certain gap between hydrocarbonscollectors, leading to different properties. Frontline theoretical calculationsindicate that the frontier orbital energy gap ΔELUMO-HOMOdecreases in the orderalkanes, alkene and arene. The conclusion that the reactivity increases in theorder of alkanes, alkene and arene can initially determined.The adsorption energy between coal and agents were studied by using theMS，and the results showed that the adsorption energy between coal and agentswere all blow84kJ/mol, which shows that the adsorption of the three kinds ofreagents on the surface of coal is physical adsorption. The higher the adsorptionenergy, the stronger the adsorption between coal and agents, the adsorptionenergy is arene＞alkene＞alkanes.The wetting heat reflected the adsorption strength between collector andminerals.The wetting heat of coal and agents were analyzed by C80micro-calorimeter, and the results showed that wetting heat the collectingperformance of hydrocarbon collectors is arene＞alkene＞alkanes.The flotation index (clean coal yield, coal ash, combustible recovery,flotation perfectness) can get after flotation experiment with different collectordosage. The results show that: when the reagent dosage is qualified, clean coalyield、combustible recovery and flotation perfectness were arene＞alkene＞alkanes.The wetting heat analysis by C80micro-calorimeter and the flotation indexboth show that the performance of hydrocarbon collectors with the same carbonatom number is arene＞alkene＞alkanes. However, the viscosity of agents increase with the increase of carbon atom number of the same series collector,which result in the poor performance because of the low dispersity in the pulp.The research method of quantum chemical calculations combined withexperiments provides a nover way for the research and development of coalslime flotation reagents.